Thermal Management for Unmanned Aerial Vehicle Payloads: Mechanisms, Systems, and Applications

Abstract

Unmanned aerial vehicles (UAVs) are emerging as powerful tools for transporting temperature-sensitive payloads, including medical supplies, biological samples, and research materials, to remote or hard-to-reach locations. Effective thermal management is essential for maintaining payload integrity, especially during extended flights or harsh environmental conditions. This review presents a comprehensive analysis of temperature control mechanisms for UAV payloads, covering both passive and active strategies. Passive systems, such as phase-change materials and high-performance insulation, provide energy-efficient solutions for short-duration flights. In contrast, active systems, including thermoelectric cooling modules and Joule heating elements, offer precise temperature regulation for more demanding applications. We examined case studies that highlight the integration of these technologies in real-world UAV applications, such as vaccine delivery, blood sample transport, and in-flight polymerase chain reaction diagnostics. Additionally, we discussed critical design considerations, including power efficiency, payload capacity, and the impact of thermal management on flight endurance. We then presented an outlook on emerging technologies, such as hybrid power systems and smart feedback control loops, which promise to enhance UAV-based thermal management. This work aimed to guide researchers and practitioners in advancing thermal control technologies, enabling reliable, efficient, and scalable solutions for temperature-sensitive deliveries using UAVs.

1. Introduction

Drone-based delivery of materials is rapidly gaining traction across various sectors due to its potential for fast, cost-effective, and flexible transportation [1]. Two principal categories of drones dominate this space: fixed-wing drones, which leverage aerodynamic lift for extended flight times, and rotary-wing drones (such as quadcopters), chosen for their ability to hover and maneuver precisely in confined areas. While these unmanned aerial vehicles (UAVs) have proven successful for tasks spanning agriculture (monitoring crop production), construction (surveying land), industry (warehouse management), public safety (law enforcement and traffic surveillance), environmental conservation efforts (deforestation monitoring), commercial delivery of goods, and various medical purposes [2], their application for transporting temperature-sensitive cargo has highlighted a critical need for robust cold-chain systems in flight.

The transport of temperature-sensitive perishable materials (blood, medicines, patient samples, vaccines, organs, food products, research samples, etc.) to hard-to-reach places remains a challenge. This is especially true in places where infrastructure is limited, for which the use of unmanned aerial vehicles (UAVs) is an attractive solution. While significant advancements have been made in developing new vaccines over the last several decades [3], the cold chain logistics required to effectively deliver these temperature-sensitive products have not kept pace, hindering their potential impact on health. Maintaining the cold chain is crucial for vaccine efficacy, as exposure to temperatures outside the recommended ranges can degrade vaccine potency. Traditional delivery methods in remote areas often struggle to preserve these conditions due to inadequate infrastructure and long transit times. Several studies around the world have explored drone delivery networks for temperature-sensitive payloads [4,5,6,7]; however, the literature specifically addressing the thermal control of payloads during drone transport remains relatively limited. Drones offer a solution by rapidly transporting vaccines directly to healthcare facilities, reducing the risk of temperature excursions. For example, in Rwanda, drones have been employed to deliver Rift Valley Fever vaccines, with stakeholders noting improved cold chain maintenance as a significant benefit [8]. Drones enhance the reliability of vaccine cold chains, especially in hard-to-reach regions.

In a study comparing drone versus ground delivery of blood products, it was found that while drone transport was faster, temperature variability during transport was higher for drones [9]. This difference may not necessarily be due to the drone itself or the flight but could be attributed to the use of phase change materials (PCMs) for cooling in drone payloads, compared to standard vacuum-insulated panels used for ground transport. The choice of thermal control solutions for drones involves considerations such as payload weight, the weight of the cooling mechanism, and the additional weight of energy sources required for active thermal regulation. These factors highlight the trade-offs in selecting appropriate cooling systems for drone-based delivery.

Our work aims to provide a comprehensive and focused review of thermal management strategies for temperature-sensitive payloads in UAV systems. Although drone-based deliveries have advanced significantly in recent years, a critical knowledge gap remains in understanding the trade-offs and performance of different thermal control mechanisms under UAV-specific constraints such as limited power, payload capacity, and environmental variability. Our goal is to bridge this gap by systematically reviewing both passive and active thermal control methods, their integration into UAV systems, and their real-world applications. Though our primary emphasis in this work is on payload thermal management, to provide relevant context, we also briefly touch on thermal management of drone hardware such as propulsion and power components since these systems influence overall UAV reliability and operational constraints.

In this paper, we review various aspects of temperature control systems for sample delivery applications involving UAVs. We provide a comprehensive analysis of current strategies for thermal management in UAVs, while identifying research gaps related to energy efficiency, component integration, and regulatory challenges. Although drone-based transport of temperature-sensitive materials has gained significant attention, the existing literature often overlooks the engineering trade-offs and performance limitations of thermal management systems under UAV-specific constraints. To address this, we first briefly explored in Section 2 how UAV flight-critical components such as rotors, electronics, and batteries are thermally managed to ensure reliable operation in diverse environments. In Section 3, we examined both passive (e.g., phase change materials, high-performance insulation) and active (e.g., thermoelectric modules, Joule heating) approaches to controlling payload temperatures, outlining their respective strengths and limitations. Section 4 discussed case studies in which UAVs transported temperature-sensitive biological materials including blood, vaccines, organs, medicines, and environmental samples, highlighting real-world implementations and persistent challenges. We then transition in Section 5 to an overview of commercial solutions, ranging from major logistics players to emerging startups, and in Section 6, we surveyed the relevant patent literature to identify innovative trends in UAV-based temperature-sensitive delivery. Section 7 provided a detailed analysis of key hurdles such as regulatory barriers, payload and range constraints, and battery limitations. Finally, Section 8 presented an outlook on promising trends including hybrid power systems, more efficient thermoelectric devices, and smart sensor-driven feedback loops. Overall, this work provides a structured resource for advancing the design and deployment of robust thermal management systems for UAV-based delivery of temperature-sensitive payloads.

2. Brief Overview of Temperature Control Systems for Drone Components

While the primary focus of this review is on thermal control of payloads carried by drones, in this section, we briefly address thermal management strategies for the drone components themselves (independent of payload), as they are critical to flight performance and UAV system reliability. Extreme temperatures can significantly impact the functionality and lifespan of essential drone components, such as rotors, flight electronics, and batteries. Effective thermal management of these components is vital for ensuring operational safety and expanding the environmental range of drone applications. Common approaches to thermal control include the use of advanced insulation materials, internal cooling systems, and anti-icing technologies.

Drone components are subject to two primary thermal challenges: overheating in high-temperature environments and ice formation in sub-zero conditions. Overheating can degrade battery performance, reduce electronic efficiency, and shorten the lifespan of internal components. Conversely, freezing conditions can impair battery functionality, reduce thrust from rotor blades, and compromise flight stability. Addressing these challenges requires a combination of passive and active thermal control strategies, which may include thermal insulation, internal cooling systems, and de-icing technologies.

2.1. Advanced Insulation and Cooling Systems for High- and Low-Temperature Environments

Drones operating in extreme temperature environments require comprehensive thermal management systems that include advanced insulation, active cooling, and passive heating strategies. These systems are designed to protect critical components such as flight electronics, batteries, and motors from temperature extremes that can degrade performance or cause failure. In high-temperature conditions, effective thermal insulation combined with active cooling mechanisms prevents overheating, while in cold environments, passive heating methods help maintain battery functionality without excessive energy consumption. Such strategies often integrate advanced materials with high thermal resistance, such as aerogels, alongside innovative cooling techniques that leverage phase-change or compressed gas systems. Together, these solutions enable drones to perform reliably across a wide range of environmental conditions, from arid deserts to glacial landscapes.

A notable demonstration of these thermal management approaches is seen in the FireDrone (Figure 1), a multi-environment, thermally agnostic aerial robot designed for extreme temperature operations [10]. The FireDrone incorporates polyimide (PI) aerogels as its primary insulation material, chosen for their ultralow thermal conductivity (typically below 0.02 W/m·K) and high mechanical strength. PI aerogels are produced through the polymerization of aromatic dianhydrides and diamines, followed by supercritical drying to retain a highly porous structure with exceptional insulating properties. These aerogel tiles are arranged into a rhombicuboctahedron-shaped exoskeleton and coated with aluminum to reflect thermal radiation, reducing heat absorption while maintaining mechanical integrity. For active cooling in high-temperature conditions, the FireDrone utilizes an internal system powered by a liquid CO₂ cartridge, which absorbs and dissipates heat from electronic components, ensuring operational stability during prolonged exposure to extreme heat, such as during wildfire monitoring. In cold environments, the drone leverages passive heating by utilizing waste heat generated from its motors and electronics to maintain a constant battery temperature, thereby reducing power consumption. The FireDrone’s performance was validated through rigorous experiments in both high-temperature fire training centers and low-temperature glacier tunnels, demonstrating its capability to maintain stable operation in diverse and extreme thermal conditions [10]. A complementary line of work in Ref. [11] demonstrated that for medium-sized UAVs that use fuel, tightly coupling the fuel tank with an active phase-change heat exchanger can keep the avionics coolant below 50 °C during rapid power excursions.

2.2. Anti-Icing Technologies for Rotor Blades

Operating drones in cold environments presents significant challenges, particularly the risk of rotor blade icing, which can severely impair flight performance and safety. Ice accumulation on rotor blades disrupts airflow, reduces lift, increases drag, and can lead to catastrophic loss of control. This problem is especially critical for drones deployed in polar regions, mountainous areas, or for winter operations such as search-and-rescue and medical deliveries. Effective anti-icing technologies are essential for ensuring safe and reliable flight performance in such conditions. Current approaches to mitigating rotor icing include both passive and active systems, with embedded heating elements emerging as a prominent solution for real-time ice prevention.

Because ice accretion on propellers is one of the most common failure modes for winter missions, we illustrate a representative electrothermal de-icing layout in Figure 2 [12]. This active anti-icing technology embodies the implementation of resistive heating elements embedded within drone rotor blades. These thin, flexible heaters are embedded directly within the propeller surfaces and powered by super-capacitors, which supply short bursts of high power to rapidly increase surface temperatures above freezing. This targeted heating prevents ice formation without significantly increasing the drone’s energy consumption. Experimental testing under glaze ice conditions at air temperatures below −5 °C demonstrated that the heated rotors effectively prevented ice buildup, maintaining aerodynamic performance with negligible impact on thrust. Such a system’s energy efficiency can be largely attributed to the use of super-capacitors, which can deliver high power rapidly while consuming less energy than traditional battery-powered systems. Super-capacitors also recharge quickly, enabling the system to operate in short, intensive bursts, making them ideal for flight conditions that require intermittent de-icing. Such technology is particularly valuable for drones performing time-sensitive operations, such as emergency deliveries or search-and-rescue missions, where maintaining reliable performance in icy conditions is critical.

3. Temperature Control Mechanisms for Drone Payloads

3.1. Passive Control

Passive insulation is a fundamental approach to maintaining temperature stability during UAV-based transport of temperature-sensitive payloads. Passive temperature control can be achieved through either enhanced thermal insulation or the use of phase change materials (PCMs). PCMs are substances that absorb or release thermal energy during phase transitions (e.g., from solid to liquid or liquid to gas), providing a cooling or heating effect to their surroundings. Depending on the temperature requirements, PCMs can range from specialized formulations to common materials like ice or dry ice.

The effectiveness of passive insulation can be described using Fourier’s Law of Heat Conduction, which models the rate of heat transfer through an insulating barrier. According to this principle, the heat transfer rate ($q$) through a material is proportional to its thermal conductivity ($k$), surface area ($A$), and the temperature difference between the inside and outside of the container $\left(T_{inside}-T_{outside}\right)$, and is inversely proportional to the insulation thickness ($d$) as follows:

$$q={\displaystyle \frac{kA\left(T_{inside}-T_{outside}\right)}{d}} .$$

(1)

In this expression, $k$ represents the thermal conductivity of the insulation material, with lower values indicating better insulating properties. Increasing the insulation thickness ($d$) or using materials with low thermal conductivity effectively reduces heat transfer. Additionally, minimizing the exposed surface area ($A$) can further decrease thermal losses. Together, these factors determine the container’s thermal resistance ($R$), defined as $R=d/kA$, which quantifies how effectively the insulation resists heat flow.

In UAV applications, optimizing these parameters involves balancing thermal performance with payload weight, as thicker or denser insulating materials can reduce flight efficiency and range. Passive insulation is often enhanced with PCMs, which absorb and release thermal energy during phase transitions to maintain stable internal temperatures. PCMs complement insulation by absorbing excess heat when the internal temperature rises and releasing stored heat when it drops, thereby extending the thermal protection without additional energy consumption. The tunable phase transition temperature of PCMs further enhances their suitability by allowing precise temperature control tailored to different applications, making them an ideal choice for UAV-based transport.

Compared to active cooling systems, passive cooling solutions, such as those using PCMs, offer significant advantages. First, they do not consume power, preserving the UAV’s limited battery capacity for critical functions like driving rotors and flight electronics. This is essential because active cooling systems would otherwise reduce flight duration and performance due to their power demands on the UAV’s lithium ion battery. For example, a typical active cooling unit for a lightweight UAV consumes about 10–15 W of power for ~1 h flight time [13], whereas power consumption for maintaining flight in the absence of cooling for the same duration is typically around 40 W [14]. Therefore, for a similar total weight of the UAV, active cooling can reduce the flight time by nearly 25–40%. Recent numerical and experimental work demonstrated that flying a multirotor at (or near) its minimum-power airspeed (~8–10 m s⁻¹) can extend flight time and mapping coverage by ~30% compared with typical cruise speeds above 20 m s⁻¹ [15,16], suggesting flight-speed choice as a first-order design variable for any thermally-managed payload. Additionally, passive cooling devices are more compact and less disruptive to the drone’s aerodynamic profile, unlike bulky active cooling systems, which can increase drag and reduce flight efficiency. Studies [13,17,18] have revealed the need for modules and connectors that extrude beyond the payload unit for efficient active cooling systems (e.g., cooling fins and fans for the hot side of the cooling unit). Thus, compared to passive cooling systems, active cooling on an UAV can increase the dimensions of the payload compartment by up to 20% and result in non-smooth surfaces that can increase form drag.

The following studies in this subsection highlight practical implementations of these principles, showcasing a range of passive thermal management techniques used in UAV-based transport systems, including the use of phase change materials, insulated containers, and embedded payload designs. A recent study [19] focused on the thermal management of electronic equipment boxes used in UAV systems, especially for remote sensing applications. It evaluated various cooling strategies, including internal and external air circulation and the use of phase change materials like cold gel packs. The most effective method identified was the combination of internal air ventilation with gel packs, which maintained lower temperatures and prevented overheating during short UAV flights. The paper also highlighted the trade-offs between cooling efficiency, payload weight, and the suitability of different strategies for UAVs operating in isolated and dynamic environments.

Building on the advantages of passive cooling, a recent study [20] explored the use of 23.3% saltwater as a phase change material (PCM) for transporting frozen blood samples via drones (Figure 3). The PCM, pre-cooled with dry ice, maintained sub-zero temperatures of −20 °C for at least 70 min while ensuring a uniform temperature distribution across the sample and container. Experimental validation confirmed the efficacy of the system in maintaining thermal stability, even under the shear forces experienced by the samples during drone flight. By incorporating real-time temperature monitoring and feedback control of the UAV’s flight path, the study demonstrated the feasibility of using PCM-based passive cooling for high-quality transport of temperature-sensitive samples.

In the work of Kostin et al. [18], a thermally insulated container designed for medical cargo transport using drones was developed. Interestingly, this container employed a double-walled design with an internal air layer for passive insulation and used Peltier thermoelectric cooling elements controlled by an Arduino Nano for active temperature regulation (c.f. Section 3.2). Laboratory tests showed effective cooling, achieving a temperature drop from 22 °C to 12 °C within 20 min, demonstrating the container’s suitability for temperature-sensitive deliveries, such as medical supplies, over short distances. In another recent study, Kokate et al. [21] demonstrated that a phase change-based thermal management system for a series-hybrid UAV reduced the system weight, volume, and pumping power by 12%, 10%, and 23%, respectively, compared to a conventional single-phase liquid cooling solution.

Payload solutions for medium- and small-package delivery using medium-sized UAVs have also been explored [22], focusing on embedded payloads housed within the drone fuselage (Figure 4). The study emphasized its compatibility with medical transportation and user-oriented design, considering usability and safety. A prototype package was developed with high-performance corrugated cardboard offering mechanical strength, thermal insulation, and recyclability. The design allowed the integration of monitoring devices, passive cooling elements like dry ice, and temperature sensors. By embedding the payload within the fuselage, the design also minimized aerodynamic turbulence by avoiding external attachments that disrupt airflow, ensuring an efficient and stable flight.

3.2. Active Control

Active temperature control systems regulate payload temperatures by supplying energy to offset heat gain or loss, ensuring thermal stability under fluctuating environmental conditions. Unlike passive strategies, which rely on insulation or phase change materials to reduce heat transfer as described by Fourier’s Law of Heat Conduction, active systems directly counteract this heat transfer using energy-driven mechanisms such as refrigeration, thermoelectric cooling, or Joule heating. Such systems are crucial for UAV-based transport of temperature-sensitive payloads, including medical supplies, biological samples, and diagnostic equipment, where consistent internal temperatures are critical.

The energy required to maintain temperature stability under active control can be described using the first law of thermodynamics:

$$Q=Pt=m{C}_p\mathsf{\Delta }T,$$

(2)

where $Q$ represents the heat energy added or removed by the system, $P$ is the system’s power consumption, t is the duration of operation, $C_p$ is the payload’s specific heat capacity, $m$ is the payload mass, and $\mathsf{\Delta }T$ is the temperature change. In active cooling (heating) systems, this energy input compensates for the heat entering (leaving) through the insulation barrier, as quantified by Fourier’s Law. Thus, effective active thermal control involves balancing power input with the rate of heat transfer from the environment while optimizing system efficiency through insulation and feedback controls.

Active temperature control for UAV payloads typically employs three key technologies: sorption-based refrigeration, thermoelectric cooling, and Joule heating. Sorption cooling, often used in refrigeration systems [23], extracts heat using refrigerants and compressors, making it suitable for ultra-low temperature transport. Thermoelectric cooling (Peltier effect) transfers heat between surfaces when an electric current is applied, providing a compact and lightweight cooling solution for UAV payloads. Conversely, Joule heating, which converts electrical energy directly into heat through resistive elements, offers an efficient method for warming payloads.

Thermoelectric (Peltier) coolers, in particular, are well-suited for UAV operations due to their lightweight, compact design and minimal impact on aerodynamic performance. Active heating systems employing Joule heating elements are essential for maintaining internal temperatures in cold environments, especially when integrated with real-time feedback systems for power optimization. However, these active systems increase energy consumption and battery weight, underscoring the importance of system design and efficiency optimization in UAV applications. The following subsections explore the practical implementations of these technologies, presenting case studies on thermoelectric cooling systems, dual heating–cooling mechanisms, and thermal platforms for airborne molecular diagnostics.

3.2.1. Active Cooling

Active cooling systems employing thermoelectric coolers (TECs), commonly known as Peltier devices, are a popular solution for UAV-based temperature control due to their compact size, low weight, and mechanical simplicity, which are all critical for UAV operations where payload capacity and aerodynamic performance are tightly constrained [17,24]. Unlike vapor-compression refrigeration, TECs operate via the Peltier effect, transferring heat from one side of the module to the other when an electric current passes through it. This solid-state operation eliminates the need for moving parts, reducing maintenance and mechanical failure risks. Additionally, the compact and modular design of TECs allows them to be easily integrated into small UAV payload compartments without significantly increasing drag or disrupting flight stability, especially in windy conditions where additional thrust and power may be required to maintain stable flight.

A notable application of TEC technology is seen in Emvolio [25], a battery-operated portable refrigerator designed to maintain temperatures between 2–8 °C for biological samples. A preclinical study evaluated its performance in preserving the biochemical and hematological integrity of rat blood, serum, and liver samples, demonstrating that Emvolio successfully maintained a stable temperature range, effectively preserving sample integrity during storage and transport. The Emvolio system employs a Peltier-based cooling mechanism with an active heat dissipation strategy using integrated fans to cool the hot side of the thermoelectric module. Despite its efficient performance, the authors of the study noted that Emvolio relies on conventional air cooling (via fans) and does not utilize alternative heat dissipation methods, such as harnessing UAV rotor downdrafts or passive heat sinks, which could further reduce energy consumption during UAV-based deployments.

Another significant example of a UAV-compatible active cooling system is presented by Pamula et al. [13]. They designed and characterized a thermoelectric cooling system capable of achieving temperatures as low as −10 °C for UAV-based sample transport. Figure 5 summarizes their final lightweight assembly, highlighting how the expanded polystyrene (XPS) shell and duty-cycled TEC together achieve cooling with minimal battery draw. The cooling module was housed within a miniature XPS container, chosen for its lightweight and high thermal insulation properties, which minimized thermal losses and reduced the overall energy load on the thermoelectric system. The system employed an active feedback control mechanism that dynamically adjusted the TEC power input based on real-time internal temperature readings. This feedback mechanism enabled the system to maintain a stable temperature range of 2 °C to 8 °C, optimizing energy efficiency while ensuring sample integrity during flight. Additionally, Pamula et al. [13] developed an experimental battery model to estimate the additional battery capacity required to sustain the cooling performance across different ambient temperatures. The results highlighted the relationship between cooling efficiency, power consumption, and battery weight, providing valuable insights into the trade-offs between flight endurance and temperature control performance. In parallel, modeling studies have shown that optimizing control parameters such as propulsion thrust, lift thrust, and pitch angle, is critical for enhancing flight performance and energy efficiency in UAVs across varied mission profiles [26].

The above studies underscore several key design considerations for integrating active cooling systems into UAV payloads. Thermal management is critical, as effective heat dissipation from the TEC’s hot side is essential for maintaining cooling efficiency. Strategies such as forced-air cooling using fans, passive cooling through heat sinks, or, where possible, leveraging UAV rotor downdrafts, can improve heat dissipation. Additionally, high-performance insulation materials, such as polystyrene or aerogels, reduce the thermal load and minimize energy consumption. Energy efficiency can be further enhanced through active feedback control systems, which dynamically regulate power usage based on real-time temperature readings, optimizing performance while conserving battery power. Finally, weight and power trade-offs must be carefully balanced, as increasing battery capacity to support the cooling system can reduce flight time. Finally, experimental modeling is critical for optimizing this trade-off to ensure the practical deployment of UAV thermal management systems.

3.2.2. Active Heating

Active heating systems are essential for UAV payloads that require elevated temperatures to preserve sample integrity or facilitate thermal processes during flight. Unlike cooling systems, which aim to remove heat, active heating systems use energy-driven methods such as resistive (Joule) heating, thermic radiation, or heated fluid circulation to maintain precise temperature ranges. These systems are particularly valuable for transporting temperature-sensitive medical supplies or enabling in-flight diagnostic processes, where consistent thermal conditions are critical. Active heating can be integrated with feedback control mechanisms to ensure accurate temperature regulation, making them suitable for a wide range of UAV-based applications, from vaccine transport to mobile molecular diagnostics.

One such implementation is presented in [27], where a temperature-controlled cargo bay was developed for drones transporting medical supplies, such as blood and vaccines. The design incorporated a dual system of active heating and cooling mechanisms, using a cooling fan for convective cooling and an electric heating element (referred to as “thermic rays”) for warming. The cooling mechanism was limited to convective heat transfer, meaning that the system could not cool below ambient temperature as no refrigeration was involved. A Raspberry Pi-based control system managed these mechanisms in real time, communicating with a cloud server for remote temperature adjustments. During tests, the 1.5 kg cargo bay prototype maintained internal temperatures within a narrow range (e.g., 24–25 °C or 26–27 °C), achieved by alternating between the cooling fan and the heating element based on predefined temperature thresholds. A barrier membrane inside the cargo bay separated the storage compartment from the temperature control elements, enhancing thermal regulation efficiency. That study emphasized the importance of lightweight, responsive, and remotely manageable temperature control systems for UAV-based transportation of critical medical supplies.

In addition to cargo heating, active thermal control is vital for advanced diagnostic applications, such as polymerase chain reaction (PCR), which requires precise thermal cycling. PCR is a molecular biology technique used to amplify DNA by cycling through three temperature phases: denaturation (94 °C) to separate DNA strands, annealing (58 °C) to allow primers to bind, and extension (72 °C) for DNA polymerase activity. Accurate thermal control is crucial for PCR success, making drone-based PCR a promising solution for real-time diagnostics in remote areas. In a recent study [28], a thermal cycler was constructed from acetal, a thermoplastic polymer chosen for its high thermal inertia, dimensional stability, and low thermal conductivity, which helps retain heat with minimal loss during flight. The block-shuttle arrangement used to accomplish the three PCR temperatures is depicted in Figure 6. The assembly, measuring 255 mm × 50 mm × 43 mm, was mounted on a custom quadcopter and contained three thermal blocks, each preheated to the required PCR cycle temperatures using Kapton film heaters (75 mm × 25 mm, 12 V, 1.92 W). The thermal inertia of the acetal blocks maintained preset temperatures without continuous power input. The PCR reaction occurred within capillary tubes (75 mm length, 1.6 mm outer diameter) placed under a shuttle housing in contact with the thermal blocks. The drone performed a series of time-programmed tilts, synchronized with solenoid actuators, to move the tubes between the thermal blocks, ensuring the samples experienced the correct thermal cycles for DNA amplification. This design enabled precise and efficient thermal cycling during flight, demonstrating the feasibility of airborne PCR for mobile diagnostics.

Another interesting study [29] for advancing drone-based diagnostics presented a lightweight, drone-compatible biochemical analysis platform equipped for convective PCR (Figure 7). Demonstrating true point-of-care potential, Figure 7 shows a single-heater convective PCR rig that completes amplification during flight. Mounted on a 3D Robotics IRIS+ drone, the system integrates a single heater for thermocycling, enabling DNA amplification during flight. Joule heating, achieved using two 10 Ω ceramic wire-wound resistors, heated the system to 95 °C, with the temperature regulated via pulse-width modulation (PWM) signals from an Arduino Uno microcontroller. The device operates using a 5 V USB battery (3200 mAh capacity), allowing the convective thermocycler (under 300 g) to function for 15–18 min within a 5–10 mile radius. A smartphone camera and app were integrated for real-time fluorescence detection and quantification of the amplified DNA. In the study, Staphylococcus aureus and λ phage DNA were successfully amplified during flight within 20 min, demonstrating the potential for rapid, point-of-care diagnostics in remote or inaccessible regions.

These studies collectively highlight the versatility of active heating systems in UAV applications. Such systems are essential for maintaining precise temperature control in UAV payloads, and for supporting critical applications such as medical supply transport and in-flight diagnostics. As with active cooling systems, active heating systems must also balance thermal performance with energy consumption, addressing the trade-offs between battery capacity, flight endurance, and payload weight. As UAV-based applications continue to expand, active heating technologies will remain integral to ensuring reliable and consistent thermal conditions for temperature-sensitive payloads and on-board sample processing.

Table 1. Comparative Analysis of UAV Thermal Management Strategies for Payloads: Advantages, Limitations, and Operational Trade-offs.

Thermal Management Strategy	Key Technologies/Mechanism	Advantages	Drawbacks/ Limitations	Impact on UAV Operations/ Suitability
Passive Thermal Control	• High-performance insulation (e.g., aerogels, EPS) • Phase change materials (PCMs)	• Zero power consumption once preconditioned • Minimal mechanical complexity • Compact design that preserves aerodynamic profile	• Added weight if thicker insulation or high PCM mass is required • Limited control once deployed; temperature maintenance is governed by material phase change properties • May not cover prolonged or extreme fluctuations	• Well-suited for short-duration flights where either payload integrity and/or battery conservation is critical • More effective when flight conditions are predictable (e.g., known ambient temperature ranges)
Active Cooling (Thermoelectric Cooling/Peltier Devices)	• Peltier modules with associated heat sinks and fans • Duty-cycled operation for feedback control	• Precise temperature regulation • No moving parts (solid state), which can reduce maintenance • Modular design allows integration into compact payloads	• Low efficiency (~10–15% of input power converted to cooling); the majority of energy is dissipated as waste heat • Increases overall power draw, potentially reducing flight duration by 25–40% • Additional battery capacity, heat sinks, or fans add weight and affect aerodynamics	• Suitable for applications that demand tight temperature control (e.g., medical sample transport) but may be more appropriate for short or mission-critical flights due to power and weight penalties
Active Heating (Joule Heating/Resistive Elements)	• Resistive (Joule) heating elements • Integration with feedback control systems (e.g., via microcontrollers)	• Provides rapid, controlled heating • Can efficiently bring payloads to required temperatures in cold conditions • Simple implementation and precise power control with real-time monitoring	• High energy consumption during operation • Adds extra weight from the heating elements and required control electronics • Increased design complexity when integrating with cooling systems in dual-mode setups	• Critical for applications that require raising payload temperatures (e.g., preventing sample freezing during longer flights) but likely to impact flight endurance unless power trade-offs are managed effectively
Hybrid Systems (Combined Active-Passive Approaches)	• Insulated containers augmented with PCMs and integrated active components (e.g., TECs or Joule heaters) • IoT-enabled feedback and duty cycling	• Leverage the energy efficiency of passive systems for baseline control while using active components for fine tuning • Flexibility to adjust to varied environmental conditions • Potential to optimize power usage via real-time monitoring	• More complex design and control • Requires balancing the added weight and higher energy consumption from the active components • Optimization is crucial to ensure that power requirements do not excessively curtail flight range	• Can be adapted for both short and moderately long flights • Ideal for missions where both precise thermal regulation and energy efficiency are required, provided that the system design carefully accounts for additional weight and power demands

provides a comparative summary of the various passive and active heating and cooling strategies discussed in this section, including advantages, disadvantages, and operational tradeoffs for the methods.

4. Case Studies of Temperature-Sensitive Payloads Carried by UAVs

Unmanned aerial vehicles (UAVs) have increasingly been used to transport biomedical materials, such as blood, vaccines, and organs, where maintaining strict temperature conditions is essential [30]. Research has suggested implementing integrated systems for real-time monitoring and both passive and active temperature control. While our review focuses on thermal control for drone payloads, it is important to acknowledge that vibration can also impact the integrity of medical products during UAV transport; further insights on this issue can be found in the study by [31], which highlights the significance of payload attachment design in mitigating vibration effects. In this section, we surveyed several real-world examples evaluating the effectiveness of various thermal management approaches for temperature-controlled UAV deliveries across multiple domains, highlighting technological innovations, opportunities, and challenges.

4.1. Blood

Blood products, a critical category of temperature-sensitive biological materials, have been a focus of research in UAV network design for medical transport. Blood is either delivered for transfusion or collected for laboratory analysis. Blood is a scarce resource in non-hospital settings, primarily due to the logistical challenges of distribution and delivery to trauma sites, compounded by its perishability. While whole blood can be stored in insulated containers for short durations, storage for prolonged periods outside proper refrigeration often leads to temperature excursions that compromise its viability. Consequently, maintaining an adequate supply of blood and ensuring its rapid delivery under temperature control are critical for enabling transfusion capabilities.

For laboratory testing, maintaining blood samples at prescribed temperatures during transport is crucial to preserve their integrity—whole blood for most chemistry tests requires storage between 2 °C and 8 °C, while whole blood for coagulation testing coagulation needs to be at ambient (18–24 °C) temperatures [32] and plasma may need to be frozen. Deviations from these temperature ranges can lead to sample degradation, potentially altering biochemical properties and affecting diagnostic accuracy [33]. Proper sample handling in the pre-analytical phase ensures accurate laboratory results. Failure to maintain the correct temperature during transport, especially over long distances, may compromise sample quality, leading to erroneous results and potentially impacting patient care. Therefore, implementing stringent temperature control protocols during the transport of blood samples is essential to maintain their integrity and ensure accurate laboratory diagnostics.

A study [34] on UAV networks in Brussels highlighted the use of thermally insulated containers equipped with preconditioned eutectic gel packs to maintain the required temperatures during transport. This passive cooling method ensures the safe delivery of blood products without the need for active thermal regulation. The study further explored network optimization under constraints such as UAV flying range, demand satisfaction rates, and the inclusion of recharging stations to extend operational capacity. It underscores the importance of strategic base placement and effective preconditioned cooling mechanisms to meet the logistical and thermal demands of transporting blood and similar medical samples. From [9], a packed red blood cell payload of 0.51 kg required a PCM weight of 0.7 kg. In comparison, for actively cooling this payload using a Peltier, 0.142 g of battery capacity is required [13].

The feasibility of using UAVs (drones) for transporting red blood cell (RBC) products for transfusion was also evaluated in Japan [35]. This study underscores the potential of drones for delivering temperature-sensitive medical supplies during disasters or to remote areas with limited infrastructure. The study employed an active transport refrigerator (ATR) weighing 6.6 kg, including a 60 Wh lithium ion battery (approximately 1 kg), to maintain the required temperature range of 2 °C to 6 °C for RBC products during flights of up to 7 km. While the ATR’s specific cooling mechanism is not described, it is likely based on thermoelectric cooling. Despite minor deviations from the ideal temperature range, the temperature remained within safe limits, and no significant differences were observed in hemolysis (measured by lactate dehydrogenase levels) between drone-transported and control samples. Additionally, insights from [13] suggest that a lighter 12 Wh LiPo battery could be sufficient to maintain the same temperature range for 30 min using temperature duty cycling control techniques.

Another study [36] investigated the impact of different drone carriage materials on maintaining stable blood sample temperatures during transportation in an equatorial climate (Figure 8). Among the tested materials—aluminum, polypropylene (PP) plastic, and expanded polystyrene (EPS) foam—EPS was the most effective, maintaining a mean kinetic temperature of 4.70 ± 1.14 °C during an 8.15 km, 17 min drone flight. Ice packs were used as the cooling method, contributing to a total payload weight of 1.55 kg, which included simulated blood and a datalogger. Blood samples transported via drone showed no significant changes in critical hematological parameters, such as hemoglobin, hematocrit, or hemolysis index, as well as in biochemical analytes like sodium and potassium. The lightweight and insulating properties of EPS foam made it ideal for this application, aligning with findings from Pamula et al. [13], which also used EPS in active cooling systems. However, the study [36] did not explore active cooling mechanisms, focusing instead on the suitability of passive thermal control. This work emphasized the importance of material choice and highlighted potential directions for incorporating active cooling in similar contexts to support longer flight times and broader healthcare applications.

A smart capsule-equipped drone system (Figure 9) for transporting blood products in urban areas was successfully validated in another study [37]. The drone delivery system employed a smart capsule designed to maintain thermal stability for blood products, with monitoring capabilities for temperature, humidity, and vibration. Across eight test flights, lasting 13–17 min each and covering a total of 105 km, the UN3373-certified box maintained the required temperature for blood products. However, since the box took 42 min to reach 6 °C as there was no active cooling, the authors recommend pre-cooling the box in a refrigerator before inserting it into the smart capsule for flight. Hemolysis tests performed on blood specimens post-flight confirmed the integrity of the blood, with potassium values measured pre-flight (3.79 mEq/L) and post-flight (3.95 mEq/L), showing minimal variation. The authors noted that using drones reduced delivery times by up to 50% for distances of 10 km and 80% for distances of 40 km compared to ground transport.

In a continuation of their work, another study [38] expanded on the Smart Capsule system designed for medical drone delivery, introducing enhancements for thermal stability and real-time monitoring of blood components. The Smart Capsule incorporates a polyurethane outer layer, a UN3373 certified container, and high-density polyethylene (HDPE) stabilizers containing water–paraffin solutions that are pre-cooled to maintain the required temperature range during flight. The system also features a temperature control unit that leverages real-time internal and external temperature sensors to ensure the mission’s thermal requirements are met, adjusting the flight plan if necessary. Laboratory tests demonstrated the system’s effectiveness in cooling blood samples initially at 11 °C to the desired temperature range and maintaining stability throughout the flight. This demonstrates an innovative combination of passive cooling and active monitoring for drone-based medical transport. However, since the cooling is not active, the intervention for out-of-range temperature measurements would be abortion or alteration of the mission.

The Medi-PodTM project [39] outlines the development of an aerodynamic and lightweight medical transportation pod designed for drone compatibility. The pod utilizes cork insulation and a carbon fiber/Kevlar material combination to ensure thermal stability during transport. A 17.5 W thermoelectric cooler was tested and shown to maintain internal temperatures between 2–5 °C, even in external conditions up to 40 °C, critical for the transport of blood products and other medical supplies. However, additional details on the specific design and operation of the thermoelectric cooling system were not provided. The fully loaded pod weighs 1.454 kg.

A recent report [40] evaluated lightweight thermal insulation systems for medical delivery drones to maintain optimal blood transport temperatures between 1 °C and 6 °C, crucial for safety and quality. Polystyrene, polyisocyanurate, and polyurethane-lined polystyrene were tested in containers modeled for drone usage in heated chambers simulating 40 °C. Among these, polyisocyanurate reduced the rate of heat transfer by 19% compared to polystyrene, with a negligible weight increase of 57.51 g. This translates to an additional 26 min of safe flight time, potentially extending drone delivery ranges by approximately 38 miles.

In another study [41], blood samples from 56 adult volunteers were tested to assess the impact of drone transport on laboratory analytes. Each volunteer provided three paired samples (chemistry, hematology, and coagulation tests), with one set flown using a small fixed-wing drone (“Aero” from 3D Robotics) and the other held stationary. Flight times ranged from 6 to 38 min at an altitude of 100 m. The samples were packed in a multi-layered payload module comprising foam blocks, biohazard bags, and an EPS foam aircraft fuselage to protect and control the in-flight environment. The temperature control was passive, using just thermal insulation. The results showed that flown and stationary sample pairs were similar across 33 common analytes, with only bicarbonate slightly deviating due to imprecision rather than bias. Overall concordance in clinical stratification was 97%, and flight time had no significant effect on the results.

In a subsequent paper [42], Amukele took the work further with blood samples that were flown in a custom-built active cooling device that was designed to run using power from an onboard battery in a fixed wing drone that was powered by a gasoline engine. Inside the cooling device, the temperature was monitored at (1) the coldest part of the payload box (just outside the cooling element), (2) the warmest part of the payload box, and (3) the ambient temperature. The minimum temperature reported in this paper was 15.5 °C using an active cooling device. The cooling element in the box was set to a minimum temperature of 15.5 °C so as not to overcool the samples. The cooling element appropriately cooled to this minimum temperature during much of the flight, as ambient temperatures reached 32 °C. No further details about the cooling methodologies were provided. No significant differences were found between the stationary and drone-flown blood sample pairs for 7 chemistry tests and 12 hematology tests after flying for 174 min covering 258 km. Only glucose and potassium measured in flown samples did not meet the clinical criteria used in the study. It was found that the temperature of the flown samples was an average 2.5 °C cooler than the stationary samples. The deviations in these two tests were consistent with the temperature difference between flown and stationary sample sets. Their study demonstrated that the transport of laboratory specimens on drones for long flights does not affect the accuracy as long as environmental factors such as temperature are strictly controlled.

Another work [43] examined the impact of drone transport on the delivery of blood products as opposed to collection of blood specimens for laboratory analysis. The blood products studied included red blood cells (RBCs), platelets (PLTs), and frozen plasma (FP24). They utilized a DJI S900 hexacopter drone to transport blood products packed in a passive cooling system comprising a Coleman FlipLid 6 cooler. The cooler maintained temperature control with pre-equilibrated thermal packs for PLTs, wet ice for RBCs, and dry ice for FP24 units. The drones flew for durations up to 26.5 min, covering an equivalent distance of 13–20 km. The results showed no adverse effects on the integrity of the blood products: no hemolysis for RBCs; no significant changes in PLT count, pH, or mean platelet volumes; and no evidence of thawing for FP24 units. While passive cooling systems were effective for these short flights, that study highlighted the system’s limitations, such as the weight limitation of multicopter drones and their relatively short flight durations compared to fixed-wing aircraft.

A recent paper [44] evaluates the impact of Zipline’s fixed-wing, sling-launched UAV delivery system on the viability of whole blood transported for medical use. The study demonstrated that there was no significant difference in the viability of whole blood before and after transport, regardless of whether it was parachute-dropped or recovered after flight. However, the authors noted that the temperature was not monitored during the flights, and longer durations or harsher conditions may lead to temperature excursions affecting blood viability. Interestingly, not only does the blood need to be cooled during flight, but it would also be even more useful to have a pre-warmer so that the blood will be transfusion-ready upon arrival. This highlights the need for robust temperature control systems for both heating and cooling during UAV transport, particularly for maintaining the cold chain during extended missions. Additionally, the study emphasized considerations like payload capacity, flight duration, and the need for insulation and refrigeration for future UAV designs to support broader use cases in healthcare. When designing UAVs, additional factors to consider include the range and flight time, which are heavily constrained by existing battery technology, as well as stealth features to ensure secure delivery in dangerous zones, particularly in battlefields, and alternatives to fixed-wing designs that can improve maneuverability.

4.2. Vaccines

Vaccines require strict temperature control throughout their storage and transport to maintain efficacy, with temperature requirements varying based on vaccine type. Refrigerated vaccines, such as Hepatitis and DtaP, must be stored between 2 °C and 8 °C. Frozen vaccines, like varicella and MMRV, require temperatures between −50 °C and −15 °C, while ultra-cold vaccines, such as some COVID-19 vaccines, demand storage between −90 °C and −60 °C [45]. These temperature ranges highlight the need for precise thermal management systems during vaccine transportation, particularly in drones, to ensure the viability of vaccines in diverse conditions and across long distances. Adverse events, such as improper cooling methods or prolonged transport times, can lead to compromised vaccine efficacy or sample contamination, underscoring the importance of reliable transport solutions.

For passive cooling in cold chain equipment for vaccines, WHO continues to evaluate PCM technologies but remains in favor of countries using standard water-filled coolant-packs, for both operational and economic reasons.

A report [46] evaluated four passive cooling container designs for vaccine delivery by drones, each catering to specific operational needs. The cylinder design offers compact geometry for efficient drone attachment and transport of small vaccine shipments. The aerogel-based cooler uses lightweight, high-performance insulation for extended temperature retention in extreme conditions. The modular design features a rectangular, stackable structure to maximize internal capacity while maintaining compatibility with standardized packaging. Lastly, the folding bag design emphasizes portability and reusability, allowing compact storage and reduced logistical challenges in reusable container systems. These designs demonstrate diverse approaches to addressing the cold-chain requirements for drone-based vaccine delivery.

A recent work demonstrated a medical cooler with an expanded polystyrene foam, a thermoelectric module, heat sink, and a fan, and demonstrated 2–8 °C cooling for vaccine applications [47]. In their design, a heat pipe is located between two rows of slots (Figure 10). Figure 10 depicts the heat pipe/TEM pathway that removes latent heat from the vaccine chamber while keeping the unit compact. Vaccines are placed inside an aluminum enclosure to keep the vaccines in place. Due to the high thermal conductivity of aluminum, heat is removed from the vaccines to the thermoelectric module (TEM) at a fast rate. In order to ensure good contact between the aluminum and the heat pipe, thermal interface material is used. This material improves thermal conductivity between the aluminum parts as long as they are securely fastened. The EPS foam is the main insulator because it is lightweight, impact resistant, and has low thermal conductivity. A heat pipe connects the inner chamber with the TEM. The insulation and heat dissipation components require additional space to be effective, so we utilized a planar heat pipe to prevent the components from interfering. The TEM pulls heat from the inner chamber through the heat pipe, and this heat is then dissipated into the environment with the fan and heat sink.

4.3. Organs

Organ transplantation demands highly precise temperature control during transport to preserve viability. Specialized organ transport systems have demonstrated that maintaining 4–8 °C significantly improves outcomes. Post-heart transplant outcomes including reduced rates of severe primary graft dysfunction and better right ventricular function were demonstrated [48]. In comparison, traditional ice preservation at 0 °C or below may lead to irreversible cellular damage, while temperatures above 8 °C are associated with suboptimal outcomes, emphasizing the critical need for precise temperature control during organ transport. UAVs are being explored for organ transport due to their ability to reduce transit times, bypass traffic congestion, and cover remote areas rapidly. Recent studies have combined advanced insulation materials with IoT-enabled Peltier cooling systems to maintain stable temperatures during UAV flights. Moreover, vibration during flight has emerged as a significant factor affecting organ viability, highlighting the importance of choosing appropriate UAV platforms and damping mechanisms.

A recent work [49] focused on the design and development of an IoT-enabled organ container embedded with a Peltier cooling module for maintaining specific temperature ranges during the transportation of medical products using drones. The system was tested for a flight range of 2 km and operational endurance of 6–8 h. A temperature sensor (LM35) monitored the container’s internal temperature, while an ESP8266 microcontroller controlled the Peltier module through a relay. The entire system was managed through the Blynk IoT platform, which provided real-time monitoring and remote control of the container’s temperature, along with alerts for successful delivery using the Twilio API.

In another study [50] utilizing a modified hexacopter DJI M600 UAS, kidneys were transported across 14 missions while maintaining a stable temperature of 2.5 °C (Figure 11). Drone transport demonstrated significantly lower vibration levels (<0.5 g) compared to over 2 g observed during fixed-wing flights, where vibration was particularly pronounced during takeoff and landing. Kidney biopsies performed before and after a total flying time of around 1 h on the drone revealed no damage from drone travel. The longest flight in the study covered a modest 3 miles between two hospitals, suggesting that inner-city organ transportation via drones could serve as a promising initial step for implementing UAV technologies. To fully meet the demands of organ transport, future drones would require the range and speed of jet airplanes (300–500 mph), as well as sufficient payload capacity. Additionally, vertical takeoff and landing (VTOL) capabilities would enable hospital-to-hospital delivery, bypassing the need for airport-based logistics.

4.4. Medicines

Medicinal products, such as insulin, monoclonal antibodies (mAbs), and specialized therapies, have stringent temperature requirements to ensure efficacy and stability. Insulin, for example, requires a storage temperature between 2–8 °C, while biologics like mAbs are highly sensitive to temperature excursions and vibrations. UAV-based medicine deliveries are gaining traction due to their potential to rapidly supply life-saving drugs to remote locations and conflict zones.

A recent study [51] used a DJI Mavic Air drone to transport insulin under ambient temperatures of −1 to 0 °C without active temperature control (Figure 12). The results showed no adverse effects on insulin stability, even under simulated vibration conditions using a vortexer, as no visible aggregates were detected. While this demonstrates the feasibility of drone delivery for insulin in controlled environments, insulin’s high temperature sensitivity underscores the need for onboard active cooling or heating mechanisms to maintain the required storage temperature range of 2 to 8 °C, ensuring compliance with manufacturer guidelines and preserving insulin quality.

Another study [52] evaluated the effects of drone flight on the structural stability of monoclonal antibodies (mAbs) used in cancer treatments. A modified Plymouth Rock X1 multicopter drone was utilized to transport mAbs over 60 short-duration flights of 330 m each, simulating hospital to clinic deliveries. The temperature was maintained within the range of 2–8 °C using a medium-sized Versapak with preconditioned cool packs, ensuring compliance with storage requirements. Vibrations were analyzed and ranged between 1.5–3 g. It was found that Versapak provided vibration isolation at frequencies >20 Hz, in addition to maintaining a stable temperature. Pharmacological assessments revealed no significant changes in the structural integrity or stability of trastuzumab and rituximab after drone transport, with no adverse effects on aggregation, fragmentation, or particle size compared to controls. These findings suggest that the drone delivery system can maintain the quality of mAbs, highlighting its potential for medical transport.

4.5. Environmental Samples

UAVs have the potential to revolutionize environmental data collection by enabling remote and rapid sample retrieval from challenging locations, such as glaciers, oceans, and active volcanoes. Unlike medical samples, environmental specimens—such as ice cores, soil samples, and water samples—often require preservation at sub-zero temperatures or protection from thermal degradation. While some short-range missions rely on ambient conditions to maintain sample integrity, longer or autonomous missions necessitate thermal management systems to prevent sample degradation. As an example, the IceDrone [53] was designed to autonomously collect ice samples in challenging Arctic conditions, addressing logistical and safety challenges associated with traditional methods. It uses a modified DJI Matrice 600 Pro with a 3D-printed drill system capable of extracting ice samples weighing approximately 0.5 kg, demonstrating feasibility for field use. While this study focused on short-range missions (0.1–1 km) from a boat to an iceberg, it did not address thermal regulation for preserving ice samples during transport as it was not required due to the limited range with external temperatures at −15 °C. However, for longer missions or autonomous operations, incorporating active or passive cooling systems will be essential to maintain sample integrity.

Table 2. Overview of Temperature-Controlled Payload Applications Using UAVs.

UAV Application	Temperature Environment	Reference(s)
Payload
In-flight PCR Diagnostics	Thermal cycling with high-temperature denaturation (~94 °C) and lower temperatures for annealing/extension	[28,29]
Blood Sample Transport	Controlled low temperature; includes frozen samples (–20 °C)	[18,20,34,35,36,37,38,41,42,43]
Vaccine Delivery	Controlled low temperature (typically 2–8 °C; ultra-cold or frozen for some vaccines)	[46,47]
Organ Transport	Controlled low temperature (typically 4–8 °C)	[49,50]
Medicinal Products Transport	Controlled low temperature (e.g., for insulin, monoclonal antibodies)	[51,52]
Environmental Sample Collection	Temperature-controlled (sub-zero or as required based on sample type)	[53]
Drone components
FireDrone	High temperature (e.g., for wildfire monitoring)	[10]
Rotor Blade Anti-Icing	Low temperature (sub-freezing conditions)	[12]

summarizes various practical applications involving temperature control of UAV payloads and drone components discussed in this review.

5. Current Commercial Solutions

In recent years, drones have gained substantial attention from companies aiming to revolutionize the delivery of goods, including temperature-sensitive payloads such as medical supplies and perishable items. The growing demand for faster and more efficient deliveries, driven by the rapid expansion of e-commerce, has prompted major players to invest in UAV-based logistics solutions [54]. Despite technological advancements, the development of robust thermal management systems remains critical for ensuring the integrity of temperature-sensitive cargo. Several companies have pursued different approaches, including passive insulation methods, active cooling or heating mechanisms, and pre-flight thermal conditioning through ground-based systems. However, the sustainability of these commercial efforts has varied, with some promising ventures struggling due to financial challenges.

Notably, Flirtey, later renamed Skydrop, and Swoop Aero were pioneers in drone-based medical deliveries, marking historic milestones in UAV logistics. Skydrop made the first FAA-approved drone delivery in the United States on 17 July 2015, when it delivered medical supplies to a health clinic in Wise, Virginia. Swoop Aero achieved a similar milestone by delivering vaccines to remote communities in Vanuatu on 18 December 2018, representing the world’s first drone vaccine delivery. More recently, on 24 July 2023, Skydrop completed the first store-to-door drone delivery approved by the Civil Aviation Authority in New Zealand history, successfully delivering Domino’s and FedEx packages. However, despite these achievements, Skydrop announced on the same day that it had run out of funding and ceased operations [55]. Similarly, Swoop Aero filed for bankruptcy in November 2024, citing a lack of financial support for scaling its operations [56]. While both companies demonstrated the potential of drones to transport temperature-sensitive payloads using insulated containers and preconditioned cooling elements, their closure underscores the financial and operational challenges of sustaining commercial drone delivery services.

Zipline, a leading name in medical supply, food, and grocery deliveries, has taken a distinct approach to thermal management. Rather than relying on active cooling during flights, Zipline uses its rapid delivery model to maintain the integrity of temperature-sensitive items. Their approach prioritizes speed over onboard thermal regulation, ensuring that payloads such as vaccines reach their destinations before temperature excursions occur [57]. Interestingly, a Zipline patent describes a payload inventory management system that includes refrigerated storage containers for vaccines and other sensitive payloads [58]. These containers monitor and report temperature and inventory levels, ensuring proper storage conditions before dispatch. However, the patent does not elaborate on specific refrigeration mechanisms, focusing instead on integrating these containers into Zipline’s logistic system. Domino’s also uses Zipline’s rapid delivery model and does not have active temperature control [59].

Meanwhile, Amazon, despite investing in UAV delivery technology, does not employ temperature control in its drone fleet. This limitation is exemplified by its inability to operate in Arizona summers due to extreme heat. Unlike its competitors, Amazon is the only major retail company developing its own drones, whereas others, such as Walmart, rely on third-party providers like Zipline and Google Wing [60].

Google Wing has pursued thermal protection through packaging innovations rather than onboard cooling systems [61]. Their patented thermally insulated inflatable packaging enclosure is designed for secure aerial transport of various payloads. The enclosure consists of an inflatable exterior chamber with an inner cavity that conforms tightly around the package, providing both structural stability and thermal buffering. However, Wing’s approach relies solely on passive insulation, limiting its effectiveness for long-duration or extreme-temperature deliveries.

Matternet, by contrast, has invested in comprehensive thermal management strategies, incorporating both ground-based and onboard technologies. Their payload systems are designed to maintain temperatures between −40 °C and 10 °C, although specific details on achieving these temperature ranges have not been publicly disclosed [62]. A U.S. patent application from Matternet outlines their ground station’s thermal regulation mechanisms, which include heating and cooling components within a modular system [63]. The ground station comprises multiple modules, including the crown module, which serves as the central hub for payload storage and battery management, and the trunk module, which houses electronic systems and supports overall ground station functionality. The crown module includes vents, heating, and cooling components to regulate the temperature of stored payloads and batteries. For example, heat from the trunk module may be directed into the crown module during colder conditions via closable ducts or vent channels. This design ensures payloads and batteries are maintained within optimal temperature ranges. Additionally, batteries can be thermally managed using liquid-cooled charging stations, which not only rapidly cool batteries after use but also optimize charging based on flight conditions to enhance battery longevity. These systems underscore the integration of advanced thermal control methods in both ground and airborne segments of drone delivery operations, setting a benchmark for precision temperature management.

DHL, in collaboration with German drone manufacturer Wingcopter, has successfully utilized drones to transport temperature-sensitive medical supplies to remote areas [64]. Their UAVs incorporate temperature-controlled storage units that ensure medicines remain within the required temperature range during transit. Deutsche Post (DHL’s parent company) has also secured a patent [65] detailing a system for managing consignments with specific temperature requirements. This patent describes a network of mobile transport units (MTUs) that assess their energy reserves and reroute deliveries if an MTU lacks sufficient capacity to maintain the necessary cooling or heating conditions. If an MTU lacks sufficient energy to ensure proper cooling or heating, the system can reroute the consignment to another unit with adequate capacity, thereby preserving the sample’s integrity. While the patent does not specify the exact thermal regulation mechanisms, it highlights the role of energy management in preserving the integrity of temperature-sensitive payloads.

These commercial solutions showcase diverse approaches to UAV-based thermal management, ranging from rapid delivery models and insulated packaging to advanced ground-station-based preconditioning and integrated onboard cooling. Despite technical advancements, several challenges remain, including energy consumption, flight endurance, and cost-effectiveness. The closure of promising companies like Skydrop and Swoop Aero highlights the importance of aligning technological innovation with financial sustainability. Nevertheless, companies such as Zipline, Matternet, and DHL continue to set benchmarks by integrating advanced thermal management techniques across their delivery ecosystems, highlighting the growing maturity of commercial UAV-based logistics for temperature-sensitive deliveries.

A Note on the Connection Between Academic Research and Commercial Solutions

Academic studies have largely explored payload thermal control for UAVs using phase change materials, high-performance insulation, and active cooling via thermoelectric modules (including duty-cycled operation to reduce power consumption). Commercial solutions, by contrast, have prioritized rapid delivery and preconditioned passive systems, with Matternet being the only provider publicly documented to have implemented active thermal regulation (primarily at the ground station level). Direct commercial adoption of laboratory-based techniques like TEC duty cycling or PCM integration has so far remained limited. Bridging this gap will require further progress on certifiability, energy trade-offs, and real-world system constraints.

6. Patents on Thermal Management for UAV Applications

In this section, we review notable patented innovations in UAV temperature control, focusing on both payload management and drone component thermal regulation. These patents demonstrate a range of approaches, from passive and active cooling systems for sensitive cargo to advanced thermal management solutions for onboard electronics and batteries.

6.1. Temperature Control of Payloads

Several patents address methods for maintaining payload temperatures using both passive and active systems. Passive cooling solutions primarily rely on insulation, such as in a patent that describes thermally insulated packaging for UAV deliveries, using insulated walls without active temperature control [66]. However, most advancements are in active cooling technologies, where temperature regulation is achieved using various mechanisms. For example, a patent describes a sample processing unit (SPU)-equipped drone with an internal centrifuge housed in a temperature-controlled chamber for processing and transporting biological samples during flight [67]. Another invention details a freezer-equipped drone capable of maintaining biological materials, such as vaccines and blood samples, at desired temperatures through active cooling mechanisms [68].

Amazon has patented a temperature-controlled drone payload container with two compartments separated by a Peltier for transport of perishable goods at a specified temperature [69]. In one of their approaches, one compartment is heated while the other is automatically cooled, taking advantage of the properties of a Peltier. Another approach involves maintaining the Peltier hot side at extremely low temperatures and employing specialized heat dissipation methods. Additionally, an integrated UAV container design repurposes waste heat from UAV components such as motors and batteries to heat the payload chamber, while cooling is managed through Peltier junctions or refrigeration compressors, with a temperature controller regulating the internal environment using real-time sensor data. Another approach of using thermoelectric elements to provide heating and cooling within a housing mounted on a drone is described in Ref. [70].

Walmart offers another approach with a UAV storage system that combines active and passive cooling. The system uses slots for passive coolants and temperature-controlling devices managed by a computing system that adjusts cooling based on object attributes retrieved from a database. It can also employ endothermic or exothermic chemical reactions for temperature regulation [71]. Another invention addresses organ and fluid preservation by using a docking system with liquid cooling and fans to dissipate heat from a Peltier unit, ensuring precise temperature control during transport [72].

For ultra-cold storage, a patented design uses nested thermoelectric cooling systems suitable for COVID-19 vaccine transport. This design employs multiple cooling layers, with an inner thermoelectric assembly surrounded by intermediate assemblies, achieving high thermal efficiency and modularity for different transportation needs [73]. Another patent describes a drone with embedded TEC units and transport fans to prevent overheating of the internal payload space during flight [74].

Some designs focus on transportation versatility, such as a thermoelectric refrigeration box compatible with both motorcycles and drones, by integrating sensors and thermoelectric devices for temperature regulation [75]. Another invention incorporates temperature control directly into the drone’s mission planning, where an onboard system adjusts flight or power strategies based on internal temperature sensors and the available battery capacity [76]. Innovative applications extend beyond medical cargo, such as a system using dry ice for passive cooling to maintain insects in a dormant state during transport, with heating elements used to rewarm them before deployment [77].

In the commercial food delivery space, Walmart has patented a UAV-integrated oven system that cooks food during transit, ensuring freshness on arrival [78]. Additionally, Walmart has developed a dynamic insulation system for perishable goods delivery that adjusts the internal temperature conditions using valves to allow airflow or a vacuum pump to create a partial vacuum for enhanced insulation control based on sensor readings and uses coolants like dry ice for thermal management [79]. Supporting ground-based solutions include the AirBox system, which maintains temperature-sensitive payloads such as food, pharmaceuticals, and groceries post-delivery through insulation and integrated heating mechanisms activated via signals from the drone [80]. A retractable landing pad with integrated heating and cooling capabilities has also been described to offer combined in-air and post-delivery thermal management for perishable goods [81].

6.2. Temperature Control of Drone Components

Effective thermal management of UAV components, such as batteries, electronics, and rotors, is critical for maintaining operational performance and safety under varying environmental conditions. Several patented technologies address these challenges by managing heat dissipation, energy efficiency, and component protection.

Amazon’s patented system for package delivery incorporates a thermoelectric-based mechanism that severs the delivery cable using heat generated by the Peltier effect [82]. Another invention employs thermoelectric generators (TEGs) to harvest waste heat from UAV processors, converting it into usable energy. Propeller-driven airflow increases TEG efficiency by cooling the cold side of the thermoelectric module [83]. Additionally, Amazon developed a vibration-isolating thermal connector that transfers heat from onboard electronics to an external heat exhaust while minimizing mechanical vibrations. This exhaust system uses either a passive convection heat sink or an active cooling fan for heat dissipation [84].

Google Wing has patented multiple thermal management technologies for UAVs. One invention integrates self-powered packaging units that store energy to supplement UAV batteries during temperature-sensitive deliveries [85]. Another system manages airflow-cooled electronics by directing air from a scoop integrated into a solar shield, simultaneously reducing solar heating and enhancing convection-based cooling of onboard components [86]. For battery management, Google Wing patented a forced-convection cooling system, circulating air through battery compartments to maintain temperatures below 30 °C during flight [87].

Zipline has developed a method for preconditioning UAV batteries based on predicted temperature variations along the flight path. The system heats or cools batteries using onboard air streams to maintain them within their optimal operating temperature range, reducing thermal stress and enhancing performance during operations [88]. Ground-based solutions also contribute to component thermal management, such as a UPS patent for a UAV docking station equipped with climate-controlled compartments, including compressors and dehumidifiers, to preserve the temperature and humidity levels of parcels awaiting drone pickup [89].

Additional methods for cooling UAV components include an edge-cooling system for fuel-cell-powered fixed-wing drones, which uses ambient air to dissipate heat from fuel cells during flight [90]. Figure 13 provides a schematic of the passive edge-cooling scheme that exploits free-stream airflow along the nose of a fixed-wing UAV. Post-flight cooling is addressed in a docking station design described in another patent that integrates sensors to measure UAV temperatures upon landing and initiates active cooling procedures to reduce thermal buildup before the next mission [91]. Finally, precise component-level thermal control is demonstrated in a patent focused on maintaining the temperature of the inertial measurement unit (IMU) via a thermally conductive layer embedded in the circuit board. This design incorporates a heating component and a thermal regulation circuit that adjusts heating output through pulse-width modulation based on real-time temperature readings, ensuring sensor accuracy by mitigating thermal drift [92].

7. Challenges and Limitations

The adoption of unmanned aerial vehicles (UAVs) for transporting temperature-sensitive payloads offers significant advantages but presents multiple challenges spanning regulatory issues, payload capacity, flight range, temperature control, and battery performance. Addressing these limitations is crucial for advancing UAV-based delivery systems, particularly for medical and environmental applications.

7.1. Regulatory Challenges

Drones represent a relatively new mode of transport, and dedicated protocols or standards from accreditation agencies remain limited. The Federal Aviation Administration (FAA) regulations for commercial drone delivery remain underdeveloped and slower than expected. Additionally, regulatory hurdles, technological constraints, and specimen viability concerns have limited UAV adoption in healthcare delivery. Regulations in many countries emphasize restrictions over clear guidelines, creating barriers for beyond-visual-line-of-sight (BVLOS) operations. BVLOS operations are further complicated by the technical requirement for continuous communication with ground pilots and the absence of standards for active climate control during UAV transport. Additionally, validating the stability and viability of specimens transported via drones remains a critical challenge, requiring further research and testing to ensure reliability in healthcare applications. These hurdles highlight the need for advancements in regulation, technology, and validation to realize the potential of drones in healthcare.

Furthermore, regulations and guidelines for the transportation of temperature-sensitive payloads, such as medical supplies, human blood, and environmental samples, are evolving but remain fragmented for drone-based delivery. The Technical Instructions for the Safe Transport of Dangerous Goods by Air (ICAO Doc 9284) [93] provide overarching regulations for payloads classified as dangerous goods, including infectious substances, and mandate strict packaging, labeling, and documentation standards for air transport. Additional guidance, such as the World Health Organization (WHO) guidelines [94] for transporting infectious substances and the Good Distribution Practices (GDP) [95] for medicinal products, ensures payload integrity and compliance with safety standards. For medical supplies, adherence to IATA’s Perishable Cargo Regulations [96] may also be relevant. However, current regulations largely address manned aviation, leaving gaps for drones, particularly for BVLOS operations. A more unified framework tailored for UAVs is essential to ensure safe and reliable transport of thermally sensitive payloads.

Moreover, critical gaps exist in UAV-specific standards and regulations for cold-chain logistics. No dedicated regulations currently address the precise technical performance requirements of temperature-controlled payload systems on drones. These include minimum insulation efficiency, pre-flight temperature stabilization, and robust in-flight thermal monitoring that must account for challenges like rotor-induced airflow, vibrations, and altitude-related temperature variations. Existing frameworks, including ICAO Doc 9284, WHO guidelines, IATA’s Perishable Cargo Regulations, and the GDP provisions, were designed for manned aviation and conventional logistics. As a result, specific performance validation for active climate control systems, such as those based on Peltier or Joule heating modules, is not comprehensively covered. This highlights the necessity for a unified, drone-tailored approach that integrates current standards with the unique operational dynamics of UAV-based cold-chain transport, ensuring consistent thermal integrity and supporting the broader adoption of these systems in healthcare and other critical applications.

7.2. Payload Capacity Constraints: Thrust and Battery Limitations

Payload capacity directly impacts the ability of UAVs to transport temperature-sensitive cargo while supporting active thermal control systems. The payload capacity is primarily limited by thrust-to-weight ratios, which are constrained by battery capacity and motor efficiency. Quantitative relationships between the required battery weight, power capacity, and achievable target cooling performance are plotted in Figure 14, providing a guideline for designers to choose an optimal battery pack. It is to be noted that practical applications will require on-board power to be optimally distributed between maintaining flight and thermal regulation (c.f. Section 3.1). For multicopter drones, high energy consumption from multiple rotors limits payloads to approximately 2–5 kg, making them suitable for short-range, small-scale deliveries. Fixed-wing drones, in contrast, have longer ranges and higher payload capacities, typically supporting up to 20 kg, but they require runways for takeoff and landing. Hybrid drones with vertical takeoff and landing (VTOL) capabilities combine these advantages, offering greater payload capacities than multicopters and longer ranges without requiring runways. However, the addition of active thermal control systems, such as thermoelectric coolers or Joule heaters, significantly increases power consumption, further reducing payload capacity. Additionally, hybrid and VTOL drones require complex power management systems, adding to their overall weight and limiting payloads.

7.3. Flight Range Challenges

Flight range is influenced by UAV type, energy storage capacity, and aerodynamic efficiency. Fixed-wing drones can cover distances up to 300 km on a single charge or fuel tank, making them ideal for rural deliveries or distributed healthcare networks. However, they lack hovering capabilities and are less suited for urban operations. Multicopters, with typical ranges of 10–25 km, are suitable for dense urban environments but struggle with long-range operations due to high energy consumption. VTOL drones, combining vertical takeoff and fixed-wing flight, offer ranges of 50–150 km but at higher costs and complexity. In addition, urban environments with tall buildings can cause GPS signal loss and electromagnetic interference, reducing the effective range. Moreover, when carrying active thermal control systems, the flight range can decrease by approximately 20–30% due to an additional battery load for heating or cooling payload compartments [13]. Optimization studies further show that the minimum-power speed itself increases with payload mass; for a 2 kg payload it rises to ~12 m s⁻¹, and operating just 8 m s⁻¹ faster than this optimum can decrease endurance by almost 50% [16], a trend also seen in large-scale simulations that reported 30% greater coverage at the optimum speed [15]. Hybrid power sources, such as hydrogen fuel cells, which offer higher energy density, or solar-augmented batteries, are potential solutions to address range limitations for UAVs carrying temperature-sensitive payloads.

7.4. Temperature Control Challenges

Maintaining precise temperature control during UAV transport is technically challenging and energy intensive. Active heating methods, such as Joule heating and induction heating, require large energy inputs. Joule heating generates heat through electrical resistance, providing uniform heating but with high energy consumption, while induction heating, which uses electromagnetic fields to heat metallic payload containers, offers efficient heat transfer but requires specialized hardware, increasing drone weight. Cooling methods, such as Peltier (thermoelectric) modules, are compact and lightweight but have low efficiency, converting only about ~10–15% of input power into cooling, with the rest dissipated as heat. Effective heat dissipation from Peltier hot sides requires additional fans or liquid cooling systems, which further drain the battery. Recent environmental sampling advancements, such as the drone-based solid-phase microextraction (SPME) microextraction sampler for air pollutants [97], demonstrate UAVs’ potential for remote data collection, but thermal control during sample transport for such applications remains relatively underexplored. Temperature stabilization is crucial for samples prone to degradation, yet most UAV-based sampling and delivery systems lack integrated thermal management, presenting a major limitation for reliable sample integrity.

7.5. Battery Limitations

Battery performance is critical for both flight and temperature control capabilities, and thermal regulation of the battery itself is essential for UAV operations. High temperatures accelerate battery degradation, reducing lifespan, while cold temperatures limit battery discharge capacity, reducing flight times. For example, during a thin-film solid-phase microextraction (TF-SPME) water sampling mission, battery performance degraded in cold weather, causing the drone to fail after a single flight due to battery freezing [98]. Battery thermal management solutions include phase change materials (PCMs) that store heat and release it slowly, thin-film heaters that maintain the battery temperature, and insulation layers to reduce heat loss in cold environments. Additionally, active battery cooling systems, such as forced-air cooling using rotor downdrafts or liquid-cooled battery packs, help prevent overheating during intensive operations. Pre-conditioning, or heating batteries to their optimal operating range before flight, is another solution. Zipline’s method for battery pre-conditioning uses heated air streams to warm the battery before takeoff, reducing thermal stress during flight and improving performance. As battery efficiency directly impacts both payload capacity and flight range, innovations in battery chemistry, such as lithium–sulfur (Li–S) or solid-state batteries, are also crucial for enabling longer flights with temperature-controlled payloads.

7.6. Environmental Impacts

Environmental conditions like wind, rain, humidity, and altitude significantly influence UAV thermal system performance. Wind can enhance convective cooling by acting as a supplemental airflow, but it also increases the aerodynamic load, causing higher power draw and internal heat generation. This trade-off is especially relevant for long-distance or headwind flights [90]. Strategic vent placement can harness ram air cooling in forward flight, but during hover or low-wind conditions, such benefits disappear. Rain and humidity require careful sealing of vents and insulation, as moisture ingress can compromise payload integrity, degrade thermal system performance, and short electronics [99]. Moreover, evaporative cooling is less effective in humid environments, while highly effective in arid conditions.

At higher altitudes, lower ambient temperatures favor passive cooling, but reduced air density diminishes convective heat transfer, limiting fan or airflow-based systems [100]. In extreme cold, components such as batteries may require active heating to prevent freezing and power loss [101]. The environmental influences mentioned here highlight the importance of robust, adaptable thermal strategies for UAV payloads, especially for missions in variable or harsh climates.

7.7. Payload Safety from Overheating and Freezing Risks

Thermal excursions, including overheating and freezing, pose serious risks to the integrity of temperature-sensitive payloads. Many biological products, such as vaccines, blood, and enzymes, degrade irreversibly when exposed to temperatures outside their specified range [41]. For instance, freezing can denature protein-based therapeutics, while overheating can reduce the potency of vaccines or compromise blood sample viability (reviewed in detail in Section 4). Payloads maintained in both passive and active thermal systems are vulnerable to such risks. Passive systems lack precise temperature control, leading to gradual drift outside safe limits during long or variable flights [13]. On the other hand, active systems (e.g., TEC) could fail mid-flight, allowing internal temperatures to spike rapidly, while unheated compartments in sub-zero conditions may allow payloads to freeze before delivery.

To mitigate these risks, practical deployments rely on a combination of engineering safeguards and operational strategies. Redundant sensors and real-time monitoring can alert operators to unsafe temperature drift. Systems with active control often include feedback loops that trigger emergency cooling or heating cycles, and are paired with alarms or autonomous abort protocols if thermal limits are exceeded [13]. Pre-flight conditioning of payloads (e.g., precooling or preheating) and the use of phase change materials further buffer against rapid shifts [13,20]. In practice, safety also involves mission planning: limiting flight duration, avoiding extreme environments, or integrating smart containers that dynamically adjust to conditions mid-flight [102]. Collectively, these approaches can ensure thermal safety and maintain payload viability from launch to delivery.

8. Research Gaps, Future Trends and Directions

8.1. Gaps in State-of-the-Art

Despite significant advancements in both passive and active thermal management strategies for UAV-based payloads, several critical gaps remain that hinder the full potential of these technologies in real-world applications.

• Energy Consumption and Power Constraints: Active cooling and heating systems, particularly thermoelectric (Peltier) devices and resistive (Joule) heating elements, are essential for precise temperature regulation. However, these systems impose a substantial energy burden on the UAV. The extra power consumption not only reduces flight endurance but also necessitates larger battery capacities, which add weight and further compromise the payload-to-power balance. This trade-off between maintaining tight temperature control and sustaining efficient flight performance remains a major challenge.
• Added Weight and Payload Integration: The integration of thermal management systems introduces a significant weight penalty. While passive systems (using phase change materials and high-performance insulation) offer energy-efficient control, their added mass can reduce payload capacity and negatively affect the drone’s flight dynamics. Similarly, the integration of active cooling components increases not only the overall weight but also the design complexity, particularly when striving to maintain aerodynamic efficiency and operational stability. The current state-of-the-art has yet to fully overcome the implications of added weight on the overall UAV system performance.
• Heat Dissipation Efficiency and Insulation Performance: Although recent advances in insulation materials, such as aerogels and expanded polystyrene, have improved thermal resistance, achieving effective heat dissipation remains challenging. Enhanced insulation can minimize unwanted heat transfer but may also impede the efficient removal of accumulated thermal energy, especially under extreme or rapidly changing environmental conditions. This represents a critical gap where a delicate balance must be struck between insulating effectiveness and the ability to actively dissipate heat.
• Control and System Complexity: The evolution toward hybrid systems that merge passive insulation with active thermal control introduces significant system complexity. Current feedback control mechanisms, although promising, often struggle to dynamically adjust to the fluctuating thermal loads encountered during flight. The sophistication required to continuously manage such multi-modal systems, with demands for precision and reliability, poses substantial technical and manufacturing challenges. Achieving this balance is important, as overly complex systems may reduce overall reliability and complicate maintenance.
• Mission and Path Planning: Another key gap lies in the need for dedicated mission planning that explicitly accounts for thermal requirements alongside traditional flight parameters. Route selection, altitude, air speed, and overall flight duration can all be optimized to reduce thermal loads and conserve power for active thermal control. In many UAV delivery scenarios, relatively small adjustments in flight path or speed can significantly influence both battery consumption and the internal temperature profile of the payload compartment, especially under conditions with large ambient temperature swings or high wind loads. Integrating thermal considerations into path planning is critical to ensuring efficient power utilization while reliably maintaining target temperatures.

8.2. Future Directions

The future of temperature-sensitive payload delivery using drones is set to advance through innovations in smart containers, power systems, and thermal management technologies.

• Emerging solutions such as AI-enabled smart capsules are enhancing real-time temperature monitoring and climate control for medical payloads, such as vaccines, biologics, and organs [102]. These smart containers can autonomously adjust internal temperatures using feedback from embedded sensors, ensuring the integrity of temperature-sensitive payloads during transit. However, scaling such technologies for large-scale deployments faces significant challenges, including public acceptance of increased drone traffic and regulatory fragmentation across regions, which limits private investments and international operations.
• Advancements in drone power and propulsion systems are central to supporting active thermal management solutions. Hybrid power technologies, including lithium polymer (LiPo) batteries, hydrogen fuel cells, and supercapacitors (SCs), are enabling longer flight durations and higher energy efficiency, addressing the limitations of single-source power systems [103]. These hybrid power sources are particularly crucial for energy-intensive thermal control mechanisms such as Joule heating for warm payloads or Peltier-based cooling systems for vaccines and biologics. Additionally, optimized UAV propulsion systems leveraging these hybrid technologies hold potential for reducing recharge times and extending mission capabilities, which is vital for long-range deliveries of temperature-sensitive payloads. The emergence of solid-state batteries, with their higher energy density and longer lifespan, also offers a potential breakthrough in extending UAV flight durations. AI-driven flight management systems can further enhance autonomous decision-making, allowing drones to dynamically adapt flight paths to avoid hazards and optimize energy consumption.
• Battery thermal management systems (BTMSs) will become increasingly important as drones operate in diverse environmental conditions and carry high-power thermal control systems. Maintaining batteries within their ideal temperature range enhances efficiency, extends battery life, and ensures a continuous power supply for payload temperature regulation [104]. Techniques such as active cooling with heat exchangers, passive insulation with phase change materials, and hybrid liquid–air cooling, commonly used in electric vehicles, are being adapted for UAVs. Integrating BTMS with payload climate control systems will help maintain both battery and cargo temperatures during long flights, expanding the operational range of medical and pharmaceutical deliveries in extreme environments.
• The development of active climate control systems for payloads remains a significant research priority [105]. Current solutions rely heavily on passive methods, such as insulated containers, which are unsuitable for payloads requiring precise temperature control, such as biologics, diagnostic samples, and gene therapies. Innovations in miniaturized Peltier cooling modules, nested thermal chambers for ultra-cold storage, and AI-optimized temperature regulation are poised to address these gaps. Additionally, advancements beyond thermal management will play a crucial role in scaling UAV-based medical deliveries. High-precision navigation technologies, such as GPS and GNSS for accurate routing and LIDAR or RADAR for real-time obstacle detection and avoidance, are improving operational safety and reliability. Also, enhanced payload capabilities can enable the transport of diverse and fragile medical materials, from blood samples to entire organs for transplantation.

As the global medical drone delivery market is projected to grow from USD 245.4 million in 2023 to USD 1.9 billion by 2032 [106], research efforts must focus on achieving reliable active temperature control systems that balance energy consumption with thermal performance. Concurrently, advancements in navigation systems, autonomous flight algorithms, and BVLOS regulatory frameworks will further enable the safe and scalable deployment of temperature-controlled payload deliveries using drones.