Space Conditioning Of Buildings Research Articles

IoT-driven monitoring and controlling to improve performance of thermoelectric air conditioning system

Thermoelectric module-based air conditioners (TEM-AC) are scalable, reliable, and have the potential to replace conventional air conditioners. However, the coefficient of performance (COP) of TEM-AC is still relatively low. Improving the COP requires a combination of temperature control, voltage control, heat recovery, airflow control, and material selection. The present study focuses on enhancing COP of the TEM-AC for building space cooling. To control and monitor the parameters of the TEM-AC, a low-cost, IoT-enabled monitoring and controlling system (MCS) is developed. The MCS helps in TEM-AC system designing as it can apply different current pulses to improve cooling capacity and control the temperature difference between both surfaces. MCS also measure all the required parameters of the TEM-AC to calculate the COP of the system and helps in reducing the calculation time for each experiment. Using a developed technique and TEM-AC design, a performance comparison of eight experimental cases has been done. Experiments have been performed in normal and control modes with different heat sinks and airflow of TEM-AC. The TEM-AC system is installed over a 16-inch × 12-inch enclosed space with a TEC-12706 module. The study indicates the COP of the system is enhanced by controlling the cold side temperature and air flow rate. For this study, maximum COP is achieved around 0.44 with control operation. The developed IoT-based monitoring and controlling system offers a promising solution for improving the performance of thermoelectric modules in building space conditioning applications.

Optimization of Double-Skin Façades for Heating and Cooling in High-Rise Buildings: A Case Study in Kuwait City

In hot arid climates such as Kuwait, the challenge of heat transfer through building façades has prompted significant debate. Determining the heating and cooling loads of buildings in such environments is crucial to assess their energy efficiency. Objectives: This research was undertaken to gauge the energy efficiency of high-rise buildings outfitted with double facades in Kuwait City, emphasizing their heating and cooling loads. Methods: A parametric computer simulation was employed, utilizing the eQUEST program, to model a prototype of a high-rise building with double facades in Kuwait City. This model was used to quantify the double façade's efficacy in mitigating heating and cooling loads, drawing comparisons with typical glazing buildings in the city. Results: Findings indicate that the total energy consumption for space conditioning in buildings with DSFs was 235 MWh/year for heating and 2,890 MWh/year for cooling, aligning well with the energy conservation program (MEW/R-6/2014) benchmarks in Kuwait. Additionally, when optimally configured with materials like polycarbonate and an optimal cavity width of 50cm, DSFs contributed to a significant reduction in building loads. Specifically, the DSFs constituted 2,900 MWh/year of the total cooling load and 235 MWh/year of the heating load. Conclusion: Our results underscore the potential of double-skin façades in decreasing energy consumption for both heating and cooling purposes, demonstrating their superiority over conventional high-rise building facades in Kuwait City.

Computational Review and Assessment of The Urban Heat Island Effect and Its Impact on Building Space Conditioning

This paper reviews and reports the recent progress and knowledge on the specific impact of the urban heat island (UHI) effect on building space conditioning for vulnerable housing where lack of air conditioning and fuel poverty causes indoor overheating, thus increasing vulnerability. Previous studies demonstrated that the increase of the ambient temperature due to UHI and heat waves impacts adversely cooling energy consumption of buildings and raises the peak electricity demand during summer and heat waves. Given the aging and dilapidated housing conditions in low-income communities, mostly of color and minorities, the economic burden of the cooling energy penalty induced by urban overheating is higher. However, literature on overheating is primarily driven by the physical characteristics of the building such as insulation, albedo, and envelope properties, and the Heat Vulnerability Index (HVI) by demographic data such as age, income, education largely remains isolated thus failing to capture the overall understanding of heat vulnerability and the role architects/urban designers can play in mitigation. Through a computational query review of the last fifteen years of publication, we are inquiring, about how UHI impacts building energy consumption in low-income and poor-quality housing and what role city and housing characteristics play in indoor overheating. Our study suggests, that in the US, due to segregated historic planning policies, low-income houses are often located in low tree canopy areas with varying urban typologies, and higher impervious material which substantially increases the air temperature thus determining energy consumption and anthropogenic heat release which contribute to present-day inequitable exposure to intra-urban heat. Both housing characteristics and the location of housing play a crucial role as similar housing will experience different exposure to intra-urban heat if not located in a heat canyon. Through this literature review, it became evident that there is a gap in the research that fails to connect building characteristics and overheating with heat vulnerability. Research involving UHI and heat vulnerability has continued to advance through energy analysis and mitigation studies, but future studies need to redefine the HVI index, especially by incorporating city and housing characteristics, which can help architects/urban designers make informed design decisions.

Estimating Optimal Cost, Insulation Layer Thickness, and Structural Layer Thickness of Different Composite Insulation External Walls Using Computational Methods

All the modern gadgets and space conditioning in buildings consume lots of energy. Energy consumption can be optimized using Composite Insulation External Walls (CIEW) built from mortar plaster and structural and insulation layers. This study aimed to improve the overall performance of CIEW by optimizing the structural and insulation layer thickness. The objective was to minimize the Life Cycle Cost (LCC) and maximize the Life Cycle Savings (LCS) of CIEW. The nonlinear Least Squares Estimation (LSE) optimization technique for optimizing LCC and LCS of CIEW was used in the study. The study considered three insulation materials—Extruded Polystyrene (XPS), Rock Wool (RW), and Glass Wool (GW)—across three heat sources, including Circulating Fluidized Bed (CFB), Grate-Fired Boiler (GFB), and Air-Source Heat Pump (ASHP). The Life Cycle Cost Analysis (LCCA) methodology suggested by Huang using a traditional optimization technique was used as a basis for mathematical formulations and result comparison. The payback period of CIEW with optimal structural and insulation layer thickness was computed. The findings revealed that applying the LSE method enabled greater economic efficiency than the LCCA method, with an up to 9.12% increase in LCS value and an up to 7.41% decrease in LCC value. The research also revealed significant correlations between insulation and structural layer thicknesses and economic parameters.

A novel method to evaluate phase change materials' impact on buildings' energy, economic, and environmental performance via controlled natural ventilation

The construction industry consumes a significant portion of global energy, with space conditioning in buildings accounting for a substantial 34% of energy usage. Notably, the energy consumption of a building is significantly influenced by its envelope. Researchers widely acknowledge that incorporating phase change materials (PCM) into the building envelope is a promising way to enhance energy efficiency and mitigate CO2 emissions in the building sector, owing to their high latent heat capacity. However, PCM must be completely charged after each cycle to exploit its full potential. Natural ventilation is a viable technique to facilitate the charging and discharging cycle of PCM within a 24-h period. To this end, the present study utilized EnergyPlus simulations to optimize the cooling energy savings of a residential building incorporating PCM into its envelope for PCM melting temperatures, considering various ventilation strategies across 45 cities in 15 climate zones worldwide. In order to evaluate the latent heat utilization of PCM and its improvement facilitated by natural ventilation, two novel indicators, namely HS and HR, were formulated to represent the heat stored and released by PCM during a 24-h cycle, respectively. In addition, following an economic analysis of PCM integration, a comprehensive environmental evaluation was carried out, which included the carbon intensities (CI) of all fuel sources contributing to power generation. The study's findings reveal substantial energy savings across all climate zones when controlled natural ventilation is coupled with PCM, and the newly proposed indicators precisely quantify the performance of PCM in all scenarios evaluated. In the arid climate zone (A), combining PCM and natural ventilation enhances energy savings, albeit to a similar extent as using ventilation alone. However, the integration of PCM with temperature-controlled ventilation yields striking energy reductions of up to 72.8%, 85.3%, and 61% in arid (B), warm temperate (C), and snow (D) climate zones, respectively. The cost-benefit analysis reveals a minimal return period of as short as five years in climate zone C. In the same climate zone C, the in-depth environmental analysis reveals a maximal reduction of 42,004 CO2-e kg/year in carbon emissions. In conclusion, this research study demonstrated that integrating PCM with controlled natural ventilation offers a practical, sustainable, and cost-effective solution with eco-friendly and energy-efficient outcomes.

Recycling Textile Waste to Enhance Building Thermal Insulation and Reduce Carbon Emissions: Experimentation and Model-Based Dynamic Assessment

By enhancing the thermal properties of cement-based building materials, energy consumption and carbon dioxide (CO2) emissions related to space conditioning in buildings can be alleviated. This study aims to present cement-based composites reinforced by textile fibers for application in building and construction. Several lightweight coating mortars were produced by partially replacing the sand in the mix with different percentages of textile waste. Mechanical and thermal characterizations of the reinforced cementitious composites were performed. The results showed that the thermal conductivity of cementitious compounds decreased as the proportion of reinforcing material in the mixture increased. In terms of mechanical properties, the textile slightly reduced the compressive strength of cementitious mortar, while it improved the flexural strength. A numerical study was then performed to derive the actual impact of these reinforced materials on the thermal behavior of a building element using COMSOL Multiphysics. Numerous configurations of walls coated with different mortar mixtures were studied. The results showed that coating both sides of a building wall with 20 mm of textile-reinforced mortar reduced the internal temperature by 1.5 °C. Thus, the application of these thermally improved mortars as coating mortars appears to be a relevant solution to enhance the thermal performance of buildings.

Optimizing space cooling of a nearly zero energy building via model predictive control: Energy cost vs comfort

The space conditioning of buildings is liable for more than 10 % of World final energy uses and related CO2-eq emissions. Such share must be drastically reduced to pursue sustainability by optimizing both energy design and devices control. In this frame, space cooling is assuming an increasing weight owing to climate change. Accordingly, this study applies a simulation- and optimization-based framework for the model predictive control (MPC) of space cooling systems. The case study is a nearly zero energy building located in Benevento – Southern Italy, Mediterranean climate – featuring an efficient air-source multi-split system for cooling. The framework is envisioned to provide optimal values of setpoint temperatures on a day-ahead planning horizon to minimize energy cost and thermal discomfort, based on weather forecasts. Accordingly, a Pareto multi-objective approach is applied considering different discomfort indicators to compare the Fanger theory with the adaptive one of ASHRAE 55. The optimization problem is solved by running a genetic algorithm – variant of NSGA II – under MATLAB® environment. The objective functions are assessed via the coupling between MATLAB® and EnergyPlus, using a validated building energy model. The multi-criteria decision-making is performed by setting a limit to discomfort to pick an optimal Pareto solution. The framework is tested addressing a typical day of the cooling season and using monitored weather data to simulate weather forecasts. Different optimal solutions are provided to fit different comfort categories. Compared to a reference control at fixed setpoint – 26 °C – the proposed solutions with similar comfort performance ensure cost savings around 28 %. Besides the proposed hypothetical implementation, the framework can be integrated in automation systems for real-time MPC. The novel contributions of this study lie in the methodology to combine MPC with different thermal comfort models as well as in the results, which provide deeps insights about the application of MPC for the space cooling of nearly zero energy buildings in a balanced climate.

Comparative Performance of Low Global Warming Potential (GWP) Refrigerants as Replacement for R-410A in a Regular 2-Speed Heat Pump for Sustainable Cooling

Heat pumps are currently being developed to reduce the energy footprint for residential and commercial building space conditioning and water heating loads in cold climates. To mitigate the nocuous impact of greenhouse gas emissions on the environment, and to create a carbon-neutral building stock, alternate lower-GWP refrigerants must also replace the predominant use of R-410A, without re-engineering the mechanical hardware. In this paper, we analyze the performance of lower-GWP alternative refrigerants (R-32, R-452B, R-454B, and R-466A) relative to the conventional R-410A and draw conclusions on the relative performances to meet cooling loads. The simulations are accomplished using the heat pump design model, a well-known, public-domain design tool with a free web interface and downloadable desktop version to support public use and the HVAC R&D community. The contributions contain detailed, hardware-based heat exchanger and system analyses to provide a comprehensive assessment. The results of the simulation are scrutinized from the first (capacity and energy efficiency) and second laws (exergy analysis) to identify sources of systemic inefficiency, the root cause of lost work. This rigorous approach provides an exhaustive analysis of alternate lower-GWP refrigerants to replace R-410A using the same hardware. The results have practical value in engineering heat pumps in an economy that is compelled to alter by the consequences and uncertainties of climate change, to reduce its anthropogenic carbon footprint.

Facile technique to encapsulate phase change material in an amphiphilic polymeric matrix for thermal energy storage

A facile fabrication technique of producing novel porous microcapsules encapsulating n-Eicosane as phase change material (PCM) with a random copolymer of poly (methyl methacrylate0.9-co-2-hydroxyethyl methacrylate0.1) (poly(MMA0.9-co-HEMA0.1)) as shell material is being reported. The porous microparticles (particle size: 31.8 ± 9 µm; porosity: ~30 ± 13%) with a hollow core (shell thickness: 1.60 ± 0.2 µm) were obtained by adopting a synthetic pathway of hot water assisted double emulsion (water/oil/water) system. Strikingly, the microcapsule system was found to entrap > 95% n-Eicosane, thus achieving significantly high thermal energy storage capability (~95%). The porous microcapsules with a phase transition enthalpy of ~ 160 J/g exhibited high phase transfer repeatability and long durability. The non-isothermal and isothermal DSC study further revealed the heat charging and discharging conditions for the microcapsules. Moreover, in contrast to neat hydrophobic PCM, the porous particles with partially hydrophilic shell (owing to polyHEMA unit) displayed better water dispersibility along with efficient thermal management characteristic as revealed by Infrared thermography. Thus, the microencapsulated phase change material in porous microcapsules can be a smart combination of good thermal energy storage function with wettability. Potentially such microcapsules may be exploited as thermal energy storage materials for space conditioning in buildings because of the suitable phase transition temperature (37 °C) displayed by the selected PCM (n-Eicosane). Our study comprehensively demonstrated water dispersible porous polymeric particles with significantly high thermal energy storage (>95%) performance that was not reported till date.

Theoretical Minimum Thermal Load in Buildings

Summary Building cooling and heating accounts for a large portion of total global energy use and requires commensurate amounts of resources, which contribute significantly to global warming. Traditionally, addressing this issue has meant improving the efficiency of equipment supplying the thermal energy, reducing envelope heat transfer, and reducing air infiltration. However, this approach is already reaching practical limits. In this perspective, we explore (1) how to reduce thermal load in buildings theoretically and (2) how to achieve that reduction and dramatically lower the energy required to support building loads practically. First, we discuss our framework developed for calculating the theoretical minimum thermal load (TMTL) in buildings. Our analysis shows that current thermal loads in buildings are more than an order of magnitude higher than the TMTL. We also introduce an approximate formula to calculate energy savings from zonal control of thermal load, which shows that the majority of zonal control benefits can be achieved with fewer than 10 zones. Then, we discuss pros and cons of various approaches and strategies to achieve the TMTL. We conclude our perspective with some longer-term R&D ideas, such as thermally adaptive clothing and thermal storage to help approach the TMTL, while providing the additional benefit of interacting with the renewable grid of the future.

Development of software codes and system architecture for optimum performance Trombe wall system in buildings using IoT devices

Trombe wall systems are passive solar structures used for space heating or cooling depending on the season of the year. Reviews in literature have shown that Trombe walls can effectively maintain a room within a desired temperature range. It is a green technology and therefore promotes the use of non-fossil technology for space conditioning in buildings. This research seeks to develop an autonomous and intelligent Trombe wall system that accounts for sudden fluctuations in the prevailing weather condition and adjusts itself to maintain the desired room temperature. Presented are the program algorithm for the deployment of an intelligent trombe system and C# code for the execution of the job on an Arduino machine.

Requirements for Building Thermal Conditions under Emergency Operations in Cold Climates

This paper provides recommendations on thermal and moisture parameters in different types of buildings under emergency operation in cold/arctic climates. We consider three scenarios under normal operating conditions: occupied, temporarily unoccupied, and long-term unoccupied. These thermal parameters are necessary to: (1) perform required work safely and efficiently, (2) support building processes, and (3) support long-term integrity of the building under emergency conditions (i.e., interruption of fuel, steam, hot water, and electrical service that interrupts building space conditioning). Under emergency conditions, requirements of thermal parameters for different categories of buildings may change. Mission critical areas can be conditioned to levels that support the agility of personnel who perform critical operations, but not to optimal comfort levels. Critical process requirements are given priority. This paper was developed for military applications, based on research performed under the International Energy Agency’s Energy in Buildings and Communities Program, Annex 73; under the Department of Defense Environmental Security Technology Certification Program project EW18-D1-5281, “Technologies Integration to Achieve Resilient, Low-Energy Military Installations,” and under the Office of the Deputy Assistant Secretary of the Army project “Thermal Energy Systems Resiliency for Army Installations located in cold climates.” Results are applicable to similar public and private sector buildings.

Analysis of basic airflow configurations for separate sensible and latent cooling systems with indoor air recirculation

Separate sensible and latent cooling (SSLC) is a technology with efficiency and comfort advantages over conventional cooling systems used for space conditioning of buildings. Using multiple cooling processes at different temperatures allows SSLC to save energy by raising the evaporation temperature of the sensible cooling process. In this paper, all possible airflow configurations of SSLC systems are enumerated under the following constraints: exactly two heat exchangers are used, and air is recirculated to the conditioned space (no exhaust or outdoor air treatment). Seven designs are identified, with varying free operating variables, and each is modeled. Analysis reveals that several configurations are equivalent, and there is only one unique basic airflow SSLC configuration: the one with the sensible and latent heat exchangers placed in series. The efficiency of the SSLC system is compared against that of the conventional system. Under standard conditions, an SSLC system can improve the coefficient of performance by 14.8%. In addition to the numerical simulation, the optimal operating condition of the basic air configuration of the SSLC system is derived analytically. The basic SSLC system is shown to offer the highest performance improvement when the outdoor temperature is relatively cool and the space sensible heat ratio is high.

Potential and Future Prospects of Geothermal Energy in Space Conditioning of Buildings: India and Worldwide Review

This paper presents modern trends in geothermal energy utilization, mainly focusing on ground source heat (GSH) pumps for space conditioning in buildings. This paper focuses on India along with a general review of studies around the world. Space conditioning of a building contributes to about 40–50% of the total energy consumed in buildings and has an adverse impact on the environment and human health. The India Cooling Action Plan (ICAP) estimates that the demand for electricity for heating and cooling of buildings will increase by over 700% in India at current levels by 2047 with an additional 800 GW of power generation capacity needed just to meet heating and cooling needs by 2050, of which about 70% is required for the residential sector only. It further intensifies as the demand for peak electric load sharply increases in summer because of the extensive use of building air conditioning systems. Researchers across the globe have tried different cooling systems and found that some systems can offer a certain amount of energy-efficient performance, and also occupant comfort. Therefore, this article examines the geothermal potential in buildings for space conditioning by critically reviewing experimental and numerical studies along with the future prospects of GSH pumps.

CFD Simulation Studies on Integrated Approach of Solar Chimney and Borehole Heat Exchanger for Building Space Conditioning

In this communication, integrated approach of solar chimney and borehole heat exchanger has been studied by using computational fluid dynamics software. It is observed that, the room temperature can be maintained at 25-30 °C, at 4.9 ACH with this integrated approach in both peak summer and winter conditions. The cooling and heating effects are evaluated as 4.73-5.55 kW at 40 °C in summer and 8.27-10.56 kW at 5 °C in winter. The SC-BHE integrated system approach produced 21-37 % higher heating effect than the BHE alone system. In cooling mode SC fitted after the room in fluid circuit and it produces the induce effect for air suction from BHE along the air blower. So, integrated approach is a feasible solution for building space conditioning.

Benefits of latent thermal energy storage in the retrofit of Canadian high-rise residential buildings

Apartment buildings in major Canadian cities make the largest share of the residential stock. However, their poor performance is often characterized by indoor thermal discomfort conditions and high-energy consumptions. Therefore, decreasing the energy demand of high-rise residential buildings through energy retrofits is critical. In the recent years, the adoption of thermal energy storage has often been proposed to stabilize indoor temperatures and to reduce the energy demand for space conditioning in buildings. In this study, the benefits of passive latent thermal energy storage systems are investigated by integrating phase change materials (PCMs) into walls and ceilings of apartment units. A hybrid PCM system with a thickness of 2 cm composed of two PCM products with melting temperatures of 21.7 °C and 25 °C respectively, is investigated. The effectiveness of this composite PCM system is evaluated by quantifying the changes in indoor temperatures and energy demands for apartment buildings in the climate conditions of Toronto and Vancouver. A parametric analysis considering the building window to wall ratios, orientations and temperature set points is performed using simulations done with EnergyPlus™. The results show that the composite PCM system improves the indoor temperatures in both climates by reducing temperature fluctuations and balancing temperature peaks. Overall, the adoption of this system results in the reduction of cooling energy demand by 6% in Toronto and 31.5% in Vancouver. The results showed the benefit of applying two PCM melting points in one zone as an effective method for annual indoor temperature regulation, especially in Toronto.

CFD Simulation Studies on Integrated Approach of Solar Chimney and Earth Air Tunnel Heat Exchanger for Building Space Conditioning

Individual studies on solar chimney and earth air tunnel heat exchanger have been carried out by various researchers but individual systems are not fulfilling the space heating and cooling demand of buildings. So, integrated approach of solar chimney and earth air heat exchanger has been studying in this communication. Computational fluid dynamics software is used for the modelling and simulation studies. The cooling effect is produced by 5.30-6.72 kW at 40°C ambient temperature and space heating is evaluated as 10.28-14.71 kW at 5°C ambient temperature and 400-1000 W/m2 16 solar radiations. And it is sufficient heating and cooling for buildings at average solar irradiance. The SC-EATHE integrated system approach produced 18 37% higher heating and cooling effect than the EATHE alone system.

Ground source heat pumps as high efficient solutions for building space conditioning and for integration in smart grids

Buildings space conditioning is a key sector with a high potential for cost effective energy and carbon savings, in which high efficient heat pumps can have a significant contribution. Besides consuming electricity increasingly produced by renewable energies, heat pumps can also have an important role to balance supply and demand, allowing the integration of intermittent renewable generation in smart grids. The aim of this paper is to demonstrate that ground source heat pumps are a very high efficiency technology for buildings space conditioning, and present a high potential for electric load management as a flexible load, when combined with the thermal storage capacity of the building.The very high efficiency of an advanced ground source heat pump system, which integrates state of art components in an optimal manner, was assessed considering the seasonal performance factors for one complete heating season and one complete cooling season, calculated based on the monitored data of an experimental site installed in a service building in Portugal. Innovative load management strategies to control the heat pump coupled with the thermal mass of the building were tested and its associated benefits, including integration for intermittent generation, were evaluated.The thermal response of the building was analyzed applying a model based on the lumped capacitance method, and it was validated with experimental data. A load shifting strategy by preheating the building and avoiding peak periods is proposed to allow the use of lower electricity rates leading to a reduction of electricity costs of 34%. Additionally preheating the buildings also contributes a larger integration of the renewable generation surplus (19–30% of the surplus generation). The implementation of Demand Response actions by switching off heating loads, during some periods of time, to compensate the variations and forecasting errors of wind power is also evaluated with positive impacts.

Evaluation of a low-cost solar cooling system for hot and humid regions in Iran

Cooling is very important for space conditioning of buildings in warm and humid regions. Along with the growth of cooling loads in modern buildings, the peak electricity demand increases during the day. This causes problems concerning the energy supply in some countries, such as Iran, as the demand for air conditioning occurs simultaneously with the maximum electricity demand of industries. The new solar cooling system presented in this article takes air from the outside by a wind tower, dehumidifies it with a desiccant wheel, cools it by an air-to-air heat exchanger (heat recovery system), and then cools it by a direct evaporative cooling system to the desired state of a maximum 100% relative humidity in the inlet air stream. The desiccant must be regenerated by heat. This can be achieved with solar energy from a solar air collector that is installed in the southern wall and roof of the building. In addition, the system is mathematically modeled. The model is used to simulate two hot and humid regions of Iran in the north (Babolsar) and south (Bushehr) over 1 year. The results show that this solar cooling system with a payback time of 5.5 years can provide 54% of the annual cooling load in the north and 48% in the south of Iran.

Modeling the interactions between the performance of ground source heat pumps and soil temperature variations

The adoption of geothermal energy in space conditioning of buildings through utilizing ground source heat pump (GSHP, also known as geothermal heat pump) has increased rapidly during the past several decades. However, one problem in operating GSHPs is that collection or rejection heat from the ground alters the ground temperature, which can adversely affect the coefficient of performance (COP). In turn, the amount of heat that must be exchanged with the ground increases in order to satisfy a given heating or cooling load. This paper presents a novel model to calculate the soil temperature distribution and the COP of GSHP. Different scenarios were simulated to quantify the impact of different factors on the GSHP performance, including seasonal balance between heat collection and heat rejection, daily running mode, and spacing between boreholes. Our results show that greater loads and smaller distances between boreholes cause changes in soil temperature large enough to adversely affect the GSHP performance, even resulting in COPs less than those commonly achieved with air source heat pumps. However, shifting from heating to cooling on a seasonal basis can, in part, mitigate this problem. Long boreholes, additional space between boreholes and intermittent running mode could also improve the performance of GSHP, but large initial investment is required.