Techno-Economic Analysis of an Air–Water Heat Pump Assisted by a Photovoltaic System for Rural Medical Centers: An Ecuadorian Case Study

Abstract

Air–water heat pumps are gaining interest in modern architectures, and they are a suitable option as a replacement for fossil fuel-based heating systems. These systems consume less electricity by combining solar panels, a heat pump, thermal storage, and a smart control system. This study was applied to a completely ecological rural health sub-center built on the basis of recycled bottles, and that, for its regular operation, requires an energy system according to the needs of the patients in the rural community. Detailed analyses were performed for heating and hot water preparation in two scenarios with different conditions (standard and fully integrated). From a technical perspective, different strategies were analyzed to ensure its functionality. If the photovoltaic system is sized to achieve advanced control, the system can even operate autonomously. However, due to the need to guarantee the energy efficiency of the center, the analyses were performed with a grid connection, and it was determined that the photovoltaic system guarantees at least two-thirds of the energy required for its autonomous operation. The results show that the system can operate normally thanks to the optimal size of the photovoltaic system, which positively influences the rural population in the case under analysis.

1. Introduction

Sustainable construction currently plays a crucial role in the fight against global warming, as this sector is responsible for a high proportion of greenhouse gas emissions, both during the construction phase and during building operations. By adopting more environmentally responsible construction practices, the environmental impact of this sector can be reduced and contribute to climate change mitigation [1]. The implementation of technologies that promote thermal comfort within buildings, such as the use of efficient insulation, low-emissivity glass, and passive design strategies, reduces the need for energy for cooling and heating [2]. This, in turn, reduces energy consumption from non-renewable sources and contributes to a healthier and more efficient environment.

One of the most significant advances in sustainable construction is the integration of renewable energy, especially through solar panels, which are considered easy to implement. However, this does not mean that other technologies, including hybrid systems, which can be of great contribution, should be ruled out. These systems not only help generate clean energy but also allow buildings to become energy self-sufficient, reducing their dependence on the conventional electricity grid and, therefore, their carbon footprint [3]. Solar panels make it possible to harness solar radiation to generate electricity while, in conjunction with technologies such as heat pumps and thermal storage, it is possible to optimize the use of the energy generated. Heat pumps provide heating or cooling through a process that consumes a minimal amount of electrical energy and can be powered by renewable sources [4]. Thermal storage, meanwhile, allows excess thermal energy to be stored for use when demand requires it, maximizing the energy efficiency of buildings.

The impact of these technologies is not only environmental but also economic. Although the initial investment in renewable energy systems and thermal comfort solutions can be high, the long-term benefits are considerable [5]. Particularly in public utility infrastructures such as medical centers, schools, and community centers, comfort needs are high to ensure health, the operational efficiency of indoor activities, and comfort, especially for vulnerable people [6]. Sustainable buildings have lower operating costs due to reduced energy consumption and maintenance, making them more competitive in the real estate market. Furthermore, the implementation of technologies such as solar panels, heat pumps, and thermal storage contributes to job creation in emerging sectors related to renewable energy and sustainable construction [7]. In this sense, the transition toward more sustainable buildings not only has positive effects on the environment but also the economy, and improves people’s quality of life, offering a more balanced and resilient future in the face of global warming.

1.1. Context and Motivation

The construction of more sustainable buildings has become an urgent necessity in the face of global warming. In this context, medical centers play a fundamental role, especially in rural areas with difficult access, as is the focus of this case study. The healthcare sector, due to the intensive use of medical equipment, ventilation and air conditioning systems, and the high volume of activity, presents great potential to reduce its carbon footprint through the implementation of sustainable construction practices. In this regard, the Puntahacienda community proposed to build a medical center using plastic bottles collected and recycled by all its members. These containers were then filled with dry sand to finally form the walls and other components instead of traditional blocks or bricks. This infrastructure is innovative, but the most interesting aspect is the organization of its inhabitants in their search for better conditions for healthcare services. To provide the best community services, renewable energy systems using solar panels were included, and the system was designed to include a heat pump and thermal storage. In the face of climate change, it is imperative to rethink how we design and operate infrastructure so that it not only meets the medical needs of the population but also contributes to the global fight against global warming, promoting a healthier and more sustainable future.

The motivation for building sustainable medical centers, as presented in Figure 1, lies in several intertwined factors. First, healthcare facilities must ensure a comfortable and efficient environment for both patients and medical staff. Thermal comfort and air quality are essential for a suitable environment for patient recovery and the well-being of healthcare workers. By integrating passive design solutions, such as adequate insulation, natural light utilization, and ventilation control, buildings can maintain a suitable environment without relying heavily on energy-intensive mechanical heating and cooling systems. Furthermore, the incorporation of renewable energy, such as solar panels in this case, and efficient heating systems, such as heat pumps, reduces energy consumption and also improves the medical center’s resilience by avoiding power outages, which is crucial in emergency situations. Ultimately, the motivation for building more sustainable buildings in the medical field is twofold: to combat global warming and to improve the health and well-being of both patients and professionals.

1.2. Review of Previous Work

According to a report by the International Energy Agency (IEA) [8], renewable energy use across the electricity, heating, and transportation sectors is projected to grow by nearly 60% between 2024 and 2030. During this period, global renewable energy capacity is expected to expand by over 5520 GW, representing a deployment rate 2.6 times higher than that observed from 2017 to 2023 [9]. These rising consumption levels, especially due to population growth and improved comfort, are driving the planning of distributed energy systems, particularly in hard-to-reach areas that require substantial improvements at the community level. These new conditions, where there is no direct dependence on the public electricity grid, have led academics and researchers to focus on these new social interactions, which require a deeper analysis of the technical and economic aspects of new energy infrastructures [10]. Furthermore, it must be recognized that a design is much more appropriate when renewable energy is used, taking advantage of the energy potential of the geographic surroundings and avoiding the use of polluting fossil fuels, which, in addition to requiring continuous transportation from main supply centers to rural areas, are inappropriate for use in buildings that, by their nature, must be pollution-free, as is the case with medical centers [11]. Another weakness of fossil fuels is the high risk of fires in localities that still lack sustained urban planning. Material losses can be quantified if we consider publicly accessible buildings, which often require cumbersome bureaucratic procedures to achieve proper implementation, such as medical equipment, offices, rest areas, etc. [12]. Renewable energy systems that have begun to operate in various isolated environments or are connected to the electrical grid are being largely expanded to diverse infrastructures [13], such as organic buildings [14], political training centers [15], and monument lighting [16]. In some cases, they operate with a single renewable source that includes storage systems, while in others, they also form hybrid systems [17].

The renewable energy sector is evolving rapidly, especially in regions where it is still emerging. As advancements accelerate, the long-term prospects for clean energy technologies are increasingly optimistic [18]. This progress reinforces the confidence of those who advocate for renewables as a key strategy to address the environmental impact of fossil fuel-dependent energy systems [19]. The growth of renewable energy has profoundly transformed the way energy is produced and consumed, providing significant benefits in both urban and rural areas [20]. In cities, the incorporation of technologies such as solar panels in buildings has made it possible to reduce dependence on fossil fuels and decrease polluting emissions, thus improving air quality and public health [21]. At the same time, in rural areas, where access to the conventional electricity grid is often limited or inefficient, renewable energy offers a decentralized and sustainable solution to guarantee the electricity supply [22]. Photovoltaic systems, mini-hydroelectric plants, and wind turbines have enabled the electrification of isolated communities, boosting local development and improving the quality of life of their residents [23]. Furthermore, the expansion of these energy sources generates employment, fosters technological innovation, and promotes greater energy equity across regions [24]. Therefore, the sustained growth of renewable energy is key to moving toward a cleaner, fairer, and more resilient energy model.

Various studies on energy systems emphasize the importance of identifying the energy strengths of each region, taking advantage of geographic conditions and renewable energy potential [25]. Some systems are composed of a single energy generation source, such as solar photovoltaic energy, which can only be used during the day as long as solar radiation is present. During the night, it is appropriate to design battery backup systems. Within this same group of renewable energies, there are other technically useful systems, such as ground heat, organic solid waste, and ocean waves [26]. The techno-economic analysis of an air-to-water heat pump assisted by a photovoltaic system is key to evaluating the viability and profitability of this technology in buildings [27,28,29,30,31]. This type of heat pump extracts thermal energy from the outside air for heating, cooling, or domestic hot water production by using electricity as the energy source [32]. By integrating it with a photovoltaic system, it is possible to power its operation with solar energy, significantly reducing electricity consumption from the grid and, therefore, long-term operating costs [33]. The analysis considers variables such as the initial investment, installation costs, maintenance, seasonal efficiency, equipment lifespan, and estimated annual energy savings [34]. Although the initial investment can be high, especially for the photovoltaic system, the return on investment is accelerated thanks to lower electricity bills and possible tax incentives or energy subsidies. Furthermore, the levelized cost of energy (LCOE) of the heat pump-photovoltaic combination is generally competitive with traditional systems, especially in regions with high solar radiation [35]. At the technical level, the coefficient of performance (COP) of the heat pump is evaluated in different climate scenarios and how solar generation can efficiently cover electricity demand during the day [36]. This type of analysis also considers the environmental impact, highlighting the reduction in CO₂ emissions compared to conventional gas or grid-powered electricity systems [37]. Overall, this solution offers a highly efficient and sustainable alternative for air conditioning and hot water in residential, commercial, and service buildings [38,39,40].

Recent studies have examined residential heat pump systems integrated with photovoltaic (PV) technology. Researchers have explored various control strategies and methods for storing surplus energy. For instance, Lukas Strobel et al. [41] evaluated a commonly deployed system aimed at efficiently managing energy flows to supply both thermal and electrical energy to an office building. Their energy management system (EMS) incorporates optimized lithium-ion battery (LIB) charging to prevent prolonged high states of charge (SOC) and continuously monitors latent thermal energy storage (TES) conditions to dynamically adjust heat pump (HP) operation. The integration of an air-source heat pump with PV panels enabled an increase in self-sufficiency by superheating the TES during PV-powered operation. This setup achieved 11% energy savings using an 800 L TES and a simple rule-based control system. Mamokone M. Modise et al. [42] conducted a techno-economic evaluation of hybrid solar-assisted air-source heat pump systems installed in university dormitories. Their study included the system’s design, implementation, and monitoring at the Mannheim girls’ residence of the Free State Central University of Technology. The project involved retrofitting a 2000 L (24 kW) electric boiler with the hybrid system. The results showed a strong financial return, with an annualized ROI of 14.39% and a profit margin of 87%. In a different approach, Francisco Zayas-Gato et al. [43] explored a geothermal energy system for a bioclimatic house, utilizing a heat pump with a horizontal heat exchanger. Their method focused on predicting the thermal output of the heat pump using historical sensor data. Promising results were obtained through the application of hybrid deep learning models that combined recurrent and convolutional neural networks. Meanwhile, Laura Romero Rodríguez et al. [44] performed simulations and analysis for the heuristic optimization of heat pump clusters that participate in residential frequency reserve programs. Their findings highlighted the importance of frequency, pricing, and activation duration in mitigating the additional energy demands caused by heat pumps. Taking into account both thermal comfort and self-sufficiency constraints, buildings were only able to accommodate up to 34% of the activation events without exceeding the comfort thresholds.

2. Methodology

For the systematic analysis, the community medical center with a gabled roof, a common feature in the community, was used. This infrastructure serves as a benchmark; it is rare to find such an environmentally friendly facility, and it is of interest to evaluate its characteristics in order to replicate it in other locations with similar characteristics, including the proposed energy and storage system. The area considered is a single floor, and its horizontal layout is 195 m², accommodating four healthcare professionals and eight patients.

The methodological analysis includes a heating system comprising a TES water tank, an HP air source, and a photovoltaic system as its main components, as presented in Figure 2. The HP air source is connected to a TES, a combi-store for preparing DHW and heating the different spaces in the medical center. Different volumes of water were added in capacities ranging from 400 to 1800 L, considered for studying the influence of the TES size on the overall energy efficiency of the system.

This study is organized as follows: Section 1 provides an introduction and a literature review. Section 2 presents the methodology. Section 3 presents an analysis of the energy sources for the supply of ecological buildings that were carried out. Section 4 presents the results obtained from the system studied. Finally, Section 5 presents the conclusions.

3. Analysis of Resources for the Hybrid System

3.1. Heat Emission System

The community has significant freshwater tributaries from the headwaters, which are transported to various users. For this project, sufficient water is available, which is heated by a heating system designed according to the internal medical requirements for a flow temperature tfl = 92 °C and a return temperature tret = 68 °C, according to the design conditions and ambient temperature in the medical clinic. The design heat load $\dot{Q}$ = 17.5 kW and a temperature of −10 °C were considered. Based on a constant ambient temperature inside the medical center, tm_center = 25 °C, the heating load $\dot{Q}$ is considered to be linearly dependent on ambient temperature [45]. Additionally, tfl and tret were determined as functions of the ambient temperature using Equations (1)–(3). The radiator describes a nonlinear relationship between the output power and the excess temperature of a radiator [46].

$${∆}_{tlog}={\displaystyle \frac{t_{fl}-t_{ret}}{Ln\frac{t_{fl}-t_{m\_center}}{t_{ret}-t_{m\_center}}}}$$

(1)

$$\dot{Q}=\dot{m_w{c}_{p,w}(t_{fl}-t_{ret})}$$

(2)

$${\displaystyle \frac{\dot{Q}}{{\dot{Q}}_{design}}}=\left({\displaystyle \frac{{∆}_{tlog}}{{∆}_{tlog,design}}}\right)$$

(3)

3.2. Heat Pump

Natural cooling is considered for cooling the environment inside the medical clinic. The equipment does not emit high amounts of heat, making it ideal for installation in these sensitive environments despite the low temperatures emanating from the compressor. Typically, high condensation temperatures can be achieved over a wide range of operating conditions compared to other refrigerants. The physical conditions of the building are quite interesting due to its walls and floors, which offer significant advantages for the system analyzed with high flow temperatures, especially for coupling the energy contributions of photovoltaics and overloading the heat storage system (TES) at higher temperatures. The air conditioning system considered for the simulations of this research includes a compressor with a speed control ranging from 15% to 100%. This subsystem uses a chiller, in which the water available in a tank from the community system is used to cool the refrigerant, which at times rises in temperature on the opposite side of the equipment. This action allows for greater performance and dissipates heat. Simulations show that the subcooler tends to significantly improve the COP compared to the feedback to the heat pump without subcooling by between 4% and 7% across the entire range of operating conditions.

The refrigeration system analysis model considers start-up and shutdown efficiency, as well as defrost losses. Compressor operating limits, such as the maximum condensation and minimum evaporation temperatures based on the compressor’s speed, were carefully considered in accordance with the technical specifications provided by the manufacturer. It is important that the community water flow be kept permanently available to avoid potential system failures when the electrical system is in operation; the energy parameters of the heat exchangers vary based on the flow rates. In this case, simulated energy consumption increased by 6% at each time step. The 3.5 kW heat pump operates with a COP of 5, water level temperatures of 2 °C, and outlet temperatures of 36 °C, considering that it is operating at only 35% of the compressor’s capacity.

3.3. Storage Tank

The combined storage tank was selected based on the position of the inlets/outlets and temperature sensors during the combined system simulations. Annual heating system data were considered, varying the height of the connections and the exact position of the sensors within a reasonable range. This procedure was used to identify the optimal energy consumption. A system was used that included a locally available 800 L water chamber designed for dynamic operation.

3.4. Photovoltaic System

Six photovoltaic modules were considered, along with their respective equipment, and were connected to the grid. The electrical system, including the photovoltaic modules, was modeled using the multi-cell equivalent circuit model [47]. The model used allows for determining the maximum extractable power of the system as well as the photovoltaic efficiency, depending on the solar radiation levels at the site. The efficiency of a modern inverter was considered to be 95%. The small photovoltaic system was sized for 3 kWp and was mounted on the roof of the building at an inclination of 15° with respect to the horizontal and with the reference plane facing south. The solar potential in Ecuador is very high due to its geographical location on the equator, varying between 4.5 and 5.5 kWh/m²/day across most of the territory. The site experiences consistently high levels of solar irradiation throughout the day, with the peak intensity being around midday. The electrical output of the photovoltaic system is defined by Equation (4) below.

$$P_{pv}=f_{pv}\ast Y_{pv}\ast {\displaystyle \frac{I_T}{I_S}}\hspace{1em}\hspace{1em}[\mathrm{W}]$$

(4)

$Y_{PV}$ is the nominal power of the PV solar panels, and $f_{PV}$ is the reduction factor. $I_T$ is known as the total incident radiation on the surface of the solar panel (Wh/m²). $I_S$ is considered as a base value of 1000 W/m², knowing that it is an optimal value of desirable irradiation.

The temperature to which the solar panels are exposed must be considered and can be determined using Equation (5):

$$T_C=G_S\left({\displaystyle \frac{NOCT-25}{1000}}\right)+T_{amb}\hspace{1em}\hspace{1em}[°\mathrm{C}]$$

(5)

$G_S$ is the solar irradiation in W/m², and $T_{amb}$ is the ambient temperature in °C. NOCT is the normalized temperature of the cell that is considered to have a global radiation of 1000 W/m², with a reference ambient temperature of 25 °C.

3.5. Demand and Recorded Weather Conditions

To ensure the suitability of the equipment considered in this study, it is important to consider parameters such as energy demand and weather conditions, which are key when placing the complete equipment into operation. The optimal physical location within the building must then be identified, especially the location of the solar panels, avoiding shadows, ensuring they are not exposed to destruction or deterioration, and ensuring access to allow for periodic maintenance. All of these factors are essential, and the most precise configuration will be achieved based on demand conditions. Parameters such as solar radiation, temperature, and system load, which must always be considered, are essential to avoid absorbing a large amount of energy from the grid. Ideally, the system should aim to be autonomous despite having a grid connection. The electrical demand profile is presented in Figure 3a, while the heating and cooling energy used are presented in Figure 3b. The solar radiation and temperature profiles for the location are also presented in Figure 3c and Figure 3d, respectively. As you can see, the system is not very large, but it could serve as a reference for new developments of this type in neighboring areas or in sites with similar characteristics where medical care is needed in rural areas. Ecological infrastructures, like those developed, complement each other very well, not only due to their architectural design but also due to their internal operating conditions. Energy efficiency is vital to ensuring service. The heating and cooling loads in the building’s compartments can be seen in Figure 3b. The consumption levels do not exceed 2950 W for heating or 1940 W for cooling.

Heat pumps will be used to source heat from the natural environment and transport it into the buildings, heating them. It also works in reverse, transporting heat from the interior of the rooms to the exterior and cooling them. This equipment is presented as an excellent option for providing greater thermal comfort to the various spaces within the building, and especially in a medical center, it is essential that these requirements be met. Furthermore, this technology is mature and ready to be utilized to meet the diverse needs of buildings.

3.6. Performance Level

To evaluate the system’s main parameters and corresponding control, the performance values were defined in an annual profile. The surplus energy produced by the solar panel is determined by Equation (6). This case arises when there is high electricity production due to fairly high levels of solar radiation that exceed the energy needs of the demand. The power consumption of the units considered is related to the heating system $W_{el,sys}$, presented in Equation (7) by calculating the HP consumption where the fan, the control system, and the pumps are involved. Energy was absorbed from the public electricity grid and sized in relation to the heating levels $W_{el,sys,grid}$ using Equation (8). The electrical demand of the building was also evaluated using Equation (9), which corresponds to the electricity for the medical center. The stored energy available for feedback to the energy system is calculated using Equation (10). The spatial performance factor (SPF) of the heat pump is determined using Equation (11). All heating of the system was considered with ${SPF}_{sys}$, Equation (12), where the useful energy for heating the different compartments within the building is delivered, as well as the demand of the system. The spatial performance factor relative to the electrical grid is determined using Equation (13). The self-sufficiency ratio, Equation (14), is a proportion of energy consumption that can be supplied with photovoltaics and is determined in relation to the total building. The fraction of electricity from the photovoltaic solar panels that are consumed in the center is evaluated using the self-consumption ratio SCR, Equation (15).

$$P_{el,PV,exc}=\mathrm{m}\mathrm{a}\mathrm{x}\left[\left(P_{el,PV}-P_{el,hh}\right),O\right]$$

(6)

$$W_{el,sys}=\int \left(P_{el,HP}+P_{el,pumps}\right)d$$

(7)

$$W_{el,sys,grid}=\int \mathrm{m}\mathrm{a}\mathrm{x}[\left(P_{el,sys}-P_{el,PV,exc}\right),O]d$$

(8)

$$W_{el,grid}=\int \mathrm{m}\mathrm{a}\mathrm{x}[\left(P_{el,sys}+P_{el,hh}-P_{el,PV}\right),O]d$$

(9)

$$W_{el,feedin}=\int \mathrm{m}\mathrm{a}\mathrm{x}[\left(P_{el,PV,exc}-P_{el,sys}\right),O]d$$

(10)

$${SPF}_{HP}={\displaystyle \frac{\int {\dot{Q}}_{cond}dt}{W_{el,HP}}}$$

(11)

$${SPF}_{sys}={\displaystyle \frac{\int {\dot{(Q}}_{SH}+{\dot{Q}}_{DHW})dt}{W_{el,sys}}}$$

(12)

$${SPF}_{sys,grid}={\displaystyle \frac{\int {\dot{(Q}}_{SH}+{\dot{Q}}_{DHW})dt}{W_{el,sys,grid}}}$$

(13)

$$SSR=1-{\displaystyle \frac{W_{el,grid}}{W_{el,sys}+W_{el,hh}}}$$

(14)

$$SCR=1-{\displaystyle \frac{W_{el,feedin}}{W_{el,PV}}}$$

(15)

3.7. Economic Analysis

The annual net cost of energy (NCOE) is evaluated using Equation (16), which considers the difference between revenues and costs. The costs of the energy purchased from the public grid management company are calculated based on the total consumption, and the average energy purchase price is valued by adding fixed costs, taxes, and variable costs per kWh. The energy purchase price = $0.25/kWh and a feed-in tariff = $0.06/kWh are used to calculate the revenues, which are values considered for this study related to the regular costs in Ecuador.

$$NCOE=Cost-Revenue=W_{el,gred}{C}_{purchase}-W_{el,feedin}{C}_{feedin}$$

(16)

The payback time (TPI) of the photovoltaic (PV) system was evaluated by comparing it with that of a comparable air-source heat pump without PV integration and equipped with an 800 L thermal energy storage (TES) unit. The analysis took into account the investment costs associated with the PV installation, as well as the additional TES volume required to manage surplus energy. The investment costs for the PV and the TES volume are considered using Equation (17), using the investment costs, which includes the difference in NCOE between a system with and without PV and the maintenance costs of the MCPV PV system. The PV system’s TPI payback time was determined by comparing it with that of a similar air-source HP system without PV and with the TES volume.

$$TPI={\displaystyle \frac{{IC}_{PV}+{∆IC}_{TES}}{∆NCOE-{MC}_{PV}}}$$

(17)

4. Results and Validation

The control strategies use specific configurations regarding the size of the photovoltaic system and TES size based on the energy demands. The photovoltaic system tested is 8 kW, a medium-sized system compared to other neighboring buildings in the community. The storage volume consisted of 1.0 m³.

The results achieved have been compared at this level, similar to those performed by Equation (14), considering a conventional control system and a system without photovoltaic energy as analysis cases. These include the building’s electrical system and heating. Figure 4 presents the values of the energy supplied to the heating circuit and the electricity provided by the utility, which is also considered a positive photovoltaic energy input. The energy values of the thermal component are also shown, which includes those provided by the heat pump, whether supplied by the utility or by the solar photovoltaic system. Approximately two-thirds of the medical center’s 125 kWh electrical demand can be guaranteed to be powered by the electricity provided by the solar panels. Figure 4 below shows the energy production under different conditions and the demand of the subsystems.

The economic analysis that allowed us to evaluate the efficiency of the HP system with the photovoltaic system and the impact of the control strategies and PV system sizing was assessed by comparing the configuration—including the photovoltaic supply and additional thermal energy storage (TES)—against a baseline system without PV, equipped with an 800 L TES and operated under standard control conditions, as defined by Equation (17).

As the size of the photovoltaic system increases, as shown in Figure 5a, assuming a constant TES size, $W_{el,grid}$ and $W_{el,sys,grid}$ decrease, while $W_{el,feedin}$ tends to increase. There is a tendency to further decrease consumption from the public electricity grid. Furthermore, in good proportions, it is possible to inject the energy produced by the eco-friendly home where the photovoltaic solar panels are installed into the electricity grid. This dynamic occurs in both the fully integrated and standard scenarios.

In the integral process, increasing the size of the photovoltaic system produces an increase in ${SPF}_{sys,grid}$; however, it reduces the ${SPF}_{sys}$. For the standard strategy, the ${SPF}_{sys}$ is the same for all photovoltaic system sizes since the system will always operate with energy regardless of whether it is supplied with power from the photovoltaic system or the public electricity grid. In this context, the size of the photovoltaic system has a more significant influence on the fully integrated control system than on the standard control system. The self-consumption ratio (SCR) tends to increase as the PV system size decreases, reaching a maximum value of 75% with a capacity of 65 kWh in both scenarios.

5. Conclusions

The implementation of an air-to-water heat pump assisted by a photovoltaic system in rural medical centers represents a sustainable and highly efficient solution for air conditioning and hot water production. This system, constructed from two-liter plastic soda bottles, is an innovative construction that allows for heat insulation and, at the same time, better cooling of the internal environment without negatively affecting the interior from external conditions such as snowfall or extreme heat waves. Furthermore, solar energy is used to power the heat pump compressor and the electrical system of the small rural medical center. This implementation of solar energy significantly reduces electricity consumption from the grid and lowers the facility’s carbon footprint. In rural areas, where access to conventional energy sources may be limited or expensive, this technology guarantees greater energy, which is especially important in contexts where the continuity of medical services is critical. Furthermore, the combination of renewable technologies helps stabilize long-term operating costs by mitigating the impact of energy price volatility. The seasonal efficiency of heat pumps can exceed COP values of 3, meaning that for every kWh of electricity consumed, more than 3 kWh of thermal energy is generated, optimizing energy efficiency. The use of solar energy further improves the overall performance of the system, reducing payback times compared to conventional systems. It is even more important to avoid fossil fuels such as gasoline or diesel, which, in critical environments like healthcare, can be more harmful due to the odor, fuel combustion, and risk of internal accidents due to improper handling. This also translates into improved thermal comfort and health in rural medical spaces, where a stable and adequate temperature is essential for clinical care. The versatility of this system allows it to be adapted to different scales of demand, making it ideal for doctors’ offices, health centers, or small rural clinics.

Furthermore, the social and environmental benefits of the system are equally significant. By promoting the use of renewable energy in rural areas, a more equitable and inclusive energy transition is fostered, aligned with the Sustainable Development Goals (SDGs), particularly goals 3 (good health and well-being), 7 (affordable and clean energy), and 13 (climate action). Reducing greenhouse gas emissions contributes to mitigating climate change, while the use of a clean energy source like solar improves public perception of sustainable technologies. Furthermore, the installation of these systems can generate local employment in assembly, maintenance, and operation tasks, strengthening the community economy. Their relatively low maintenance and long component lifespan ensure continuous operation with minimal interruptions, which is crucial in healthcare facilities. It is also important to consider that this solution can be integrated into hybrid systems with a grid backup or generators to ensure continuous operation in low solar radiation conditions. Overall, the photovoltaic-supported air-to-water heat pump is presented as a technically and economically viable option, improving the energy resilience of rural medical centers and elevating the quality of medical care while promoting environmentally responsible practices.

Solar-powered heat pumps have limitations that are associated with intermittent solar radiation, which can affect their performance on cloudy days or at night. Furthermore, system efficiency depends on an adequate thermal or electrical storage capacity to cover demands when solar production is not available. Initial installation costs can also be high. Finally, their performance can be affected by extreme weather conditions in cold climates.