Search Results (32)

The growing demand for energy-efficient heating, ventilation, and air conditioning (HVAC) systems has increased interest in multi-source heat pumps as a sustainable solution. While extensive research has been conducted on heat pump performance prediction, there is still a lack of practical tools for early-stage system evaluation. This study addresses that gap by developing regression-based models to estimate the performance of various heat pump configurations, including air-source, ground-source, and dual-source systems. A simplified performance estimation model was created, capable of delivering results with accuracy levels comparable to TRNSYS simulation outputs, making it a valuable and accessible tool for system evaluation. The analysis was conducted across nine climatic zones in Italy, considering key environmental factors such as air temperature, ground temperature, and solar irradiance. Among the tested configurations, hybrid systems like Solar-Assisted Ground-Source Heat Pumps (SAGSHP) achieved the highest performance, with SCOP values up to 4.68 in Palermo and SEER values up to 5.33 in Milan. Regression analysis confirmed strong predictive accuracy (R² = 0.80–0.95) and statistical significance (p < 0.05), emphasizing the models’ reliability across different configurations and climatic conditions. By offering easy-to-use regression formulas, this study enables engineers and policymakers to estimate heat pump performance without relying on complex simulations. Full article

The transition to low-carbon heating systems is fundamental to achieving climate neutrality, particularly within the building sector, which accounts for a significant share of global greenhouse gas emissions. Among various technologies, heat pumps have emerged as a leading solution due to their high energy efficiency and potential to significantly reduce CO₂ emissions, especially when powered by renewable electricity. This systematic review synthesizes findings from the recent literature, including peer-reviewed studies and industry reports, to evaluate the technical performance, environmental impact, and deployment potential of air source, ground source, and water source heat pumps. This review also investigates life cycle greenhouse gas emissions, the influence of geographical energy mix diversity, and the integration of heat pumps within hybrid and district heating systems. Results indicate that hybrid HP systems achieve the lowest specific GHG emissions (0.108 kgCO₂eq/kWh of heat delivered on average), followed by WSHPs (0.018 to 0.216 kgCO₂eq/kWh), GSHPs (0.050–0.211 kgCO₂eq/kWh), and ASHPs (0.083–0.216 kgCO₂eq/kWh). HP systems show a potential GHG emission reduction of up to 90%, depending on the kind of technology and energy mix. Despite higher investment costs, the lower environmental footprint of GSHPs and WSHPs makes them attractive options for decarbonizing the building sector due to better performance resulting from more stable thermal input and higher SCOP. The integration of heat pumps with thermal storage, renewable energy, and smart control technologies further enhances their efficiency and climate benefits, regardless of the challenges facing their market potential. This review concludes that heat pumps, particularly in hybrid configurations, are a cornerstone technology for sustainable building heat supply and energy transition. Full article

Mid-deep geothermal heat pump systems (MD-GHPs) feature high energy efficiency and low energy consumption, yet their promotion is restricted by high initial investment. While the initial investment of air-source heat pumps (ASHPs) is obviously lower, it also has a larger energy consumption. To address the complementary strengths and weaknesses of single-source heat pump systems, this paper puts forward an integrated system combining MD-GHPs and ASHPs, and the series mode was determined as the optimal integration approach for the hybrid system through comparative analysis. Simulation analysis was conducted to explore the adaptability of series mode, and numbers of mid-deep ground heat exchangers in nine cities across various climate regions were studied. The MD-GHP system is suitable for space heating in Xining and Xi’an, while ASHPs are suitable for space heating in Nanjing and Hangzhou. For intermediate resource areas like Urumqi and Tsingdao, the series mode achieves the best economic benefits during the 24th year of operation. Full article

The implementation of renewable energy systems (RESs) in the agricultural sector has significant potential to mitigate the negative effects of fossil fuel-based products on the global climate, reduce operational costs, and enhance crop production. However, the intermittent nature of RESs poses a major challenge to realizing these benefits. To address this, thermal energy storage (TES) and hybrid heat pump (HHP) systems are integrated with RESs to balance the mismatch between thermal energy production and demand. In pursuit of clean energy solutions in the agricultural sector, a 3942 m² greenhouse in Yeoju-si, South Korea, is equipped with 231 solar thermal (ST) collectors, 117 photovoltaic thermal (PVT) collectors, four HHPs, two ground-source heat pumps (GSHPs), a 28,500 m³ borehole TES (BTES) unit, a 1040 m³ tank TES (TTES) unit, and three short-term TES units with capacities of 150 m³, 30 m³, and 30 m³. This study evaluates the long-term performance of the integrated hybrid renewable energy and thermal energy storage systems (HRETESSs) in meeting the greenhouse’s heating and cooling demands. Results indicate that the annual system performance efficiencies range from 25.3% to 68.5% for ST collectors and 31.9% to 72.2% for PVT collectors. The coefficient of performance (COP) during the heating season is 3.3 for GSHPs, 2.5 for HHPs using BTES as a source, and 3.6 for HHPs using TTES as a source. During the cooling season, the COP ranges from 5.3 to 5.7 for GSHPs and 1.84 to 2.83 for ASHPs. Notably, the HRETESS supplied 3.4% of its total heating energy directly from solar energy, 89.3% indirectly via heat pump utilization, and 7.3% is provided by auxiliary heating. This study provides valuable insights into the integration of HRETESSs to maximize greenhouse energy efficiency and supports the development of sustainable agricultural energy solutions, contributing to reduced greenhouse gas emissions and operational costs. Full article

The global challenges of rising energy consumption and carbon emissions underscore the urgent need for efficient and sustainable heating solutions in the building sector. The implementation of high-performance buildings that envelope insulation and the increasing adoption of low-temperature radiant heating systems have significantly reduced the water temperature required from heat sources, enabling greater compatibility with renewable energy systems. In this study, we propose a renewable energy heating system incorporating a solar-assisted medium-depth ground heat exchanger (MDGHE). A dynamic simulation model of the solar-assisted MDGHE system was developed in TRNSYS, featuring a novel MDGHE module specifically developed to improve simulation accuracy. A case study of a residential building in China was conducted to evaluate the performance of the proposed system. The simulation results demonstrate that while the standalone MDGHE covers 71.9% of the building’s heating demand, integrating solar collectors with the MDGHE can increase this coverage to 99.9%, enabling full compliance with heating requirements without relying on conventional heat pumps. The results revealed that the system’s COP reached 9.26. Compared with the traditional medium-depth ground source heat pump system with the COP of 4.84, the energy efficiency of this system has been enhanced by 47.7%. A static payback period of 7 years has been obtained compared with the cost of central heating service for residential buildings. These findings highlight the potential of solar-geothermal hybrid systems as a sustainable alternative to traditional heating methods. Full article

Earth-Air Heat Exchangers (EAHEs) provide a compelling solution for improving building energy efficiency by harnessing the stable subterranean temperature to pre-treat ventilation air. This comprehensive review delves into the foundational principles of EAHE operation, meticulously examining heat and mass transfer phenomena at the ground-air interface. This study meticulously investigates the impact of key factors, including soil characteristics, climatic conditions, and crucial system design parameters, on overall system performance. Beyond independent applications, this review explores the integration of EAHEs with a diverse array of renewable energy technologies, such as air-source heat pumps, photovoltaic thermal (PVT) panels, wind turbines, fogging systems, water spray channels, solar chimneys, and photovoltaic systems. This exploration aims to clarify the potential of hybrid systems in achieving enhanced energy efficiency, minimizing environmental impact, and improving the overall robustness of the system. Full article

With rapidly developing new energy technologies, rational energy planning has become an important area of research. Ground source heat pumps (GSHPs) have shown themselves to be highly efficient. effective in reducing building or district energy consumption and operating costs. However, when optimizing integrated energy systems, most studies simplify the GSHP model by using the rated coefficient of performance (COP) of the GSHP unit, neglecting factors such as soil, buried piping, and actual operating conditions. This simplification leads to a deviation from the actual operation of GSHPs, creating a gap between the derived operational guidelines and real-world performance. Therefore, this paper examines a hotel equipped with photovoltaic panels, a GSHP, and a hybrid energy storage unit. By constructing models of the underground pipes, GSHP units, and pumps, this paper considers the thermal exchanger between the underground pipes and the soil, the thermal pump, and the operating status of the unit. The purpose is to optimize the running expenses using an enhanced mote swarm optimization (PSO) algorithm to calculate the optimal operating strategy of system equipment. Compared to the simplified energy system optimization model, the detailed GSHP unit model shows a 21.36% increase in energy consumption, a 13.64% decrease in the mean COP of the GSHP unit, and a 44.4% rise in system running expenses. The differences in the GSHP model affect the energy consumption results of the unit by changing the relationship between the power consumption of the PV system and the GSHP at different times, which in turn affects the operation of the energy storage unit. The final discussion highlights significant differences in the calculated system operating results derived from the two models, suggesting that these may profoundly affect the architectural and enhancement processes of more complex GSHP configurations. Full article

This review examines the integration of ground source heat pump (GSHP) systems with energy piles as a sustainable approach to improving energy efficiency in smart cities. Energy piles, which combine structural support with geothermal heat exchange, offer significant advantages over conventional air source heat pumps (ASHPs) by using stable ground temperatures for more efficient heating and cooling. System efficiency can be improved by integrating hybrid systems, cooling towers, and solar thermal systems. While the initial investment for GSHP systems is higher, their integration with energy piles significantly reduces electricity consumption and operating costs, providing a compelling solution for regions with high energy demand and escalating energy prices. Government financial incentives, including subsidies, loans, and tax rebates, can reduce payback periods to less than 10 years, encouraging the adoption of energy piles and GSHP systems. The paper analyzes heat transfer mechanisms in energy piles, particularly the role of groundwater circulation in improving heat dissipation and overall system performance. It also discusses optimized design considerations, performance metrics, and economics, highlighting the critical role of site-specific conditions from thorough site surveys and strategic planning of adaptive management to adjust system operations based on real-time demand in optimizing the benefits of geothermal energy systems. This review serves as a comprehensive guide for engineers and researchers in the effective application of energy piles within urban infrastructure, thereby supporting sustainable urban development and mitigating the urban heat island effect. Full article

This paper investigates the optimization of insulation thickness with respect to the integration of renewable energy systems in residential buildings in order to improve energy efficiency, maximize the contribution of renewables and reduce life cycle costs. Using the DesignBuilder and EnergyPlus software, this study models a representative two-story residential building located in Athens, Greece. The building envelope features extruded polystyrene thermal insulation and windows with unplasticized polyvinyl chloride frames and low-e glazing. Six scenarios with hybrid renewable energy systems are analyzed, including air- and ground-source heat pumps, solar thermal systems and a biomass fired boiler, so as to assess energy consumption, economic feasibility and internal air temperature conditions. A Pareto-fronts-based optimization algorithm is applied to determine the optimal combination of insulation thicknesses for the walls, the roof and the floor, focusing on minimizing the life cycle cost and maximizing the percentage of renewable energy utilized. The results demonstrate that scenarios involving biomass boilers and solar thermal systems, both for heating and cooling, when combined with reasonable thermal protection, can effectively meet the recent European Union’s directive’s goal, with renewable energy systems contributing more than 50% of the total energy requirements, whilst maintaining acceptable internal air temperature conditions and having a life cycle cost lower than contemporary conventional buildings. Full article

Demand response (DR) enhances building energy flexibility, but its application in hybrid heating systems with dynamic pricings remains underexplored. This study applied DR via heating setpoint adjustments based on dynamic electricity and district heating (DH) prices to a building heated by a hybrid ground source heat pump (GSHP) system coupled to a DH network. A cost-effective control was implemented to optimize the usage of GSHP and DH with power limitations. Additionally, four DR control algorithms, including two single-price algorithms based on electricity and DH prices and two dual-price algorithms using minimum heating price and price signal summation methods, were tested for space heating under different marginal values. The impact of DR on ventilation heating was also evaluated. The results showed that applying the proposed DR algorithms to space heating improved electricity and DH flexibilities without compromising indoor comfort. A higher marginal value reduced the energy flexibility but increased cost savings. The dual price DR control algorithm using the price signal summation method achieved the highest cost savings. When combined with a cost-effective control strategy and power limitations, it reduced annual energy costs by up to 10.8%. However, applying the same DR to both space and ventilation heating reduced cost savings and significantly increased discomfort time. Full article

This article investigates heating options for poultry houses (or sheds) in order to meet their specific indoor air temperature requirements, with case studies conducted across Australia under conditions similar to those encountered worldwide. Hybrid geothermal–solar (PV)–gas heating systems with various configurations are proposed to minimise the lifecycle costs and GHG emissions of poultry shed heating, which involves six seven-week cycles per year. The baseload heating demand is satisfied using ground-source heat pumps (GSHPs), with solar photovoltaic panels generating the electricity needed. LPG burners satisfy the remaining heating demand. Integrating these systems with GSHPs aims to minimise the overall installation costs of the heating system. The primary focus is to curtail the costs and GHG emissions of poultry shed heating with these hybrid systems, considering three different electricity offsetting scenarios. It is found that a considerable reduction in the lifecycle cost (up to 55%) and GHG emissions (up to 50%) can be achieved when hybrid systems are used for heating. The Pareto front solutions for the systems are also determined. By comparing the Pareto front solutions for various scenarios, it is found that the shave factor, a measure of the GSHP proportion of the overall system, significantly influences the lifecycle cost, while the size and utilisation of the solar PV panels significantly affect the lifecycle GHG emissions. Full article

Ground source heat pump (GSHP) systems depend on the capacity for heat transfer between the system and the ground, and it is good practice to carry out an in situ thermal response test (TRT) to determine the undisturbed ground temperature, the thermal conductivity of the ground, and the thermal resistance of the borehole. Conventionally, a TRT is undertaken in a replica borehole heat exchanger (BHE); however, alternative methods have been developed that can provide continuous depth-resolved temperature recordings. The enhanced TRT (ETRT) uses a hybrid cable system which incorporates a resistance heating wire to provide a linear heat source and a fibre optic cable to measure the temperature along the length of the borehole. In this paper, a case study is presented in which a TRT and ETRT were carried out in the same BHE to evaluate its thermal response and estimate the thermal characteristics of the ground. After a brief introduction of both methods and their interpretation, a comparison between them is presented regarding their advantages and disadvantages using the results of the performed tests, which revealed an 8% difference in the soil thermal conductivity values, averaged over the length of the BHE. Full article

Germany is undergoing an energy transition. By 2045, fossil fuels will be gradually replaced by clean energy. An alternative option is to use geothermal, solar and wind energy to generate heat or electricity. Currently, an economic model that considers these three energy sources and incorporates the design and installation of the energy system as well as operational costing focusing on the local market is lacking. In this study, we present a concept for a hybrid energy system combining solar, wind and geothermal energy for small, detached houses. We also develop a simplified economic model for the German market and local energy subsidy policies. The model was applied to two different cities in northern Germany, calculating the installation and long-term operating costs of different energy systems and combinations over a period of 100 years, including the consideration of the lifespan of variable equipment. The calculations show that for this small hybrid energy system the initial installation costs can vary from EUR 20,344 to EUR 70,186 depending on different portfolios. Long-term operating costs come mainly from electricity purchased from the grid to compensate for periods of low solar or wind production. In addition, the study included a calculation of the payback period for retrofitting a natural gas heating system. Results show that combining a photovoltaic system with a ground source heat pump, especially in the form of a near-surface heat exchanger, yields a shorter payback period (5 to 10 years). However, the incorporation of on-roof wind turbines into the hybrid energy system may significantly prolong the payback period and is therefore not recommended for use in low wind speed areas. Full article

Hybrid ground source heat pump systems (GSHP) offer energy flexibility in operation. For hybrid GSHP systems coupled with district heating, limited studies investigated control strategies for reducing system energy costs from the perspective of building owners. This study proposed a cost-effective control strategy for a hybrid GSHP system integrated with district heating, investigating how power limits of district heating/GSHP, COP value for control (COP_ctrl), and control time horizon impact the system annual energy cost, CO₂ emissions, and long-term borehole heat exchanger system performance. The simulations were performed using the dynamic building simulation tool IDA ICE 4.8. The results indicate that to realize both the energy cost savings and the long-term operation safety, it is essential to limit the heating power of district heating/GSHP and select an appropriate COP_ctrl. The control time horizon insignificantly affected the annual energy cost and long-term borehole heat exchanger system performance. The recommended COP_ctrl was 3.6, which is near the GSHP seasonal performance factor. Eventually, the cost-effective control reduced the system’s annual energy cost by 2.2% compared to the GSHP-prioritized control. However, the proposed control increased the CO₂ emissions of the hybrid GSHP system due to the higher CO₂ emissions from district heating. Full article

Geothermal energy exploration, development, and research have been ongoing in Canada for several decades. The country’s cold climate and the push to develop renewable energy sources have driven interest in geothermal energy. Despite this drive, regulatory complexities and competition with other relatively inexpensive energy sources with existing infrastructure have hindered development. As such, interest has grown and waned with changes in the energy economy over several decades, leaving many projects at a standstill. As of January 2023, there are currently no operational geothermal power projects in Canada. Many hot spring pool and spa complexes remain active, and Canada is a leading country in the installation of ground source heat pumps (GSHPs; also called geo-exchange systems). However, in the last decade, the interest in deep geothermal systems has renewed, with many new projects starting up across several provinces and territories. Moreover, projects that had shown limited progress for many years—such as Mount Meager in British Columbia—have begun to renew their development efforts. Research is also expanding within prominent research groups and universities. The areas of focus include both building upon previous studies (such as thermal gradients and the heat flow in sedimentary basins) and researching new methods and resources (such as GSHPs, closed-loop systems, integrated geothermal operations, and hybrid systems, including heat storage). The development is supported by federal, provincial, and territorial governments through grants and the development of regulatory frameworks. Although challenges still remain for Canada to develop its geothermal energy resources, several power, thermal, and co-production projects, ongoing research, funding, and regulatory acts are all moving forward to support geothermal development. This paper aims to study Canada’s geothermal energy update in 2023 regarding the aspects mentioned above. Full article