Groundwater Source Heat Pump System Research Articles

Hybrid model-free control based on deep reinforcement learning: An energy-efficient operation strategy for HVAC systems

At present, most optimization objectives of heating, ventilation, and air-conditioning (HVAC) systems focus on the local optimization of equipment during cooling hours, usually ignoring the importance of the end conditions. In addition, traditional control methods may not perform well in complex or dynamic systems. Therefore, in this study, a hybrid model-free control (HMFC) strategy was developed that combines deep reinforcement learning (DRL) with L-BFGS-B and expert knowledge to improve its ability to cope with complex system environments. This strategy was used to optimize the cooling and heating periods of a groundwater source heat pump system in a bitterly cold region of China throughout the year, considering the end-of-system conditions. L-BFGS-B optimized the fresh-air ratios for the end air-handling unit, whereas DRL achieved global optimization of the heat pump outlet temperature, air-conditioning water circulation pump frequency, and submersible-pump frequency. To verify the effectiveness of the strategy, a simulation platform was built based on actual data and device parameters, and the simulation results of HMFC and model predictive control (MPC) were output, compared, and analyzed with data of the system measured in 2022 under expert rule-based manual control (RBC). The results show that HMFC was 7.38 % and 9.38 % more energy efficient than RBC during heating hours, respectively. HMFC was 24.26 % more energy efficient than RBC and 10.03 % more energy efficient than MPC during cooling hours. Moreover, the distribution of the system coefficient of performance under the HMFC method was more concentrated in the higher range, indicating that the proposed HMFC can save energy savings. Thus, it is a feasible optimization scheme for buildings without a large number of historical data. Finally, the strategy was applied to a real engineering experimental analysis, and the engineering practice results show that the strategy is robust and practical.

Study on heat exchange of groundwater under complex geological conditions in karst area of south China

This paper takes a groundwater source heat pump in the region as the research object and based on field research, experimental tests combined with comparative analysis, the data on its operation is monitored and analyzed in terms of operation, energy saving, and environment. The results show that the cooling temperatures of the test rooms were all below 26°C, the average coefficient of performance of the units was 4.61–4.93 and the average coefficient of performance of the system was 3.08–3.27. In addition, compared to conventional water-cooled chillers, 466 tons of standard coal could be saved in one cooling season, resulting in a reduction of 1,150.8 tons of carbon dioxide emissions, 9.3 tons of sulfur dioxide emissions and 4.7 tons of dust emissions The savings in operating costs are 793,000 RMB. This shows that the groundwater source heat pump has good energy efficiency and economy. The research results obtained in this paper provide a reference for improving energy efficiency and optimizing the operation of the groundwater source heat pump system. It is of great significance to the application of groundwater source heat pump systems in areas with complex geological environments.

Comparative economic analysis of air conditioning system with groundwater source heat pump in general-purpose buildings: A case study for Kayseri

In this study, which aims to reduce energy consumption and dependence on fossil fuels in buildings, the use of an alternative air conditioning system instead of conventional air conditioning systems (CACS), which are widely used in general-purpose public buildings (GPPBs) with high energy consumption, is investigated. A groundwater source heat pump system (GSHPS) was selected as the alternative air conditioning system that exploits an underground water source used in Kayseri province (Turkey). GSHPSs were used both for heating and cooling of a sample GPPB and all costs were determined in detail in the study. In order to compare whether the GSHPS is economical or not, a commonly used CACS, which consisted of a central heating system with natural gas and an air-cooled cooling system was selected. After system components was selected according to the thermal loads of the building, the system costs were determined considering the initial investment cost and the operating costs. Results showed that the proposed GSHPS was more economical than the CACS in terms of initial investment cost and equivalent uniform annual cost by 22.68% and 11.09%, respectively, despite being 3.87% more expensive in terms of total annual operating costs.

Geothermal dynamic constraints of groundwater source heat pump system in shallow aquifers

Due to the temperature of shallow aquifers being affected by atmospheric temperature, groundwater source heat pumps (GWSHPs) become unstable and the operation efficiency of GWSHP is constrained. In the study, the coupling numerical simulation model of the groundwater flow field and temperature field is established based on the continuous monitoring results in an actual experimental site, and the water and thermal migration of shallow aquifer is simulated under the influence of the atmospheric environment. The influence of the dynamic change in ground temperature is analyzed on a GWSHP. The results indicated that the temperature of the shallow aquifer is affected by the external temperature, and the recharge temperature in the summer cooling period was 33°C, and that in the winter heating period was 6°C in the actual site, to avoid the occurrence of thermal penetration when there is a gap between the actual situation and the design situation, the single cooler can balance the insufficient cooling capacity in summer under the most unfavorable situation. The research results can also provide a reference for the development and utilization of geothermal energy resources in shallow aquifers.

Optimization of solar-assisted GWHP system based on the Trnsys model in cold regions

In this study, a Trnsys simulation prediction model for multistage utilization solar-assisted groundwater source heat pump system and a new year-round operation control strategy are proposed. A new dual-interface solar and groundwater heat storage module Type299 was created, which was imported into Trnsys transient simulation model for simulation. A one-year experiment was conducted to test the accuracy of the new model Type299 and Trnsys transient simulation prediction model, taking a case system in the Shenyang area as an example. When the proposed new system and control strategy was applied to the case system, the results showed that the maximum comprehensive performance coefficient of the new system is approximately 4.54, which is 23.8% higher than that of the original system. The annual solar energy utilization of the new system increased by approximately 4.68 × 105 MJ compared with the original system. After 10 years of simulation operation, it was found that the groundwater temperature under the action of the new system was approximately 3.1 °C higher than that of the original system. This effectively alleviates the underground water temperature decrease year by year caused by the operation of the original system.

Cyclic use of groundwater: An innovative way to improve performance of a groundwater source heat pump system during a cooling period

The building sector is a large user of energy and thus a large emitter of CO2. Replacing traditional energy with renewable energy in buildings can effectively reduce greenhouse gas emissions and global warming effects. This paper introduces a new groundwater source heat pump (GWSHP) system installed for air-conditioning of an official room. The main innovation of the new GWSHP system is the cyclic use of groundwater to save the electricity consumption of the lifting pump that pumps the groundwater from a well and also to reduce the amount of groundwater needed by the GWSHP system. The cyclic use of groundwater was realized by adding a circulating pump and a tank in the GWSHP system and intermittently running the lifting pump according to the water temperature in a groundwater heat exchanger. The performances of the new GWSHP system for four different operation modes of the lifting pump were evaluated and compared based on measurements of representative days in 2017 and 2019. The results show that the cyclic use of groundwater with an optimal operation mode can not only effectively improve the performance of the GWSHP system but also significantly reduce groundwater consumption. Specifically, the coefficient of performance of the GWSHP system was increased from 3.6 for conventional operation mode with no cyclic use of groundwater to 4.3 for the optimal operation mode, and the groundwater consumption per working day was significantly decreased from 9.2 m3 for conventional operation mode to 4.0 m3 for the optimal operation mode. Moreover, the long-term performance for three consecutive years from 2018 to 2020 was also evaluated based on measurements, and the results show that the long-term performance is almost the same as the performance of the representative day, which means that the representative day method used in this paper to evaluate the performance of the GWSHP system is feasible and reliable. The operating experience of this study can provide an important reference for the design and selection of GWSHP systems in areas with a different abundance of groundwater.

Analysis of the thermal performance reduction of a groundwater source heat pump (GWHP) system

This paper investigates the thermal performance reduction of a groundwater heat pump (GWHP) system installed in Hubei province, China by the monitoring of the system operation over a two-year period. Pipe corrosion and deposits were detected in the maintenance of heat pumps, which might contribute to the thermal performance reduction. In order to understand the physic-chemical dynamics inside heat pumps during the system operation, the groundwater pumped out from the aquifers and the deposits collected in a condenser of a heat pump were analyzed. The groundwater has electrical conductivity of 973 μS/cm, indicating low salinity. The X-ray fluorescence (XRF) analysis shows the deposits were composed mainly of 66.4% Fe2O3 and 17.8% CaCO3, indicating both effects of iron oxidation and groundwater fouling.The corrosion effects on the heat transfer efficiency of metal pipes were examined. The heat transfer coefficient (HTC) comparison of a raw pipe and three rusted pipes show that the HTC of the rusted pipes was reduced by 8.3–41.5%, meaning a significant decrease in heat transfer efficiency. It is verified that the thermal reduction of the GWHP system could be attributed to the pipe corrosion which desires to be carefully considered in system design and operation in future.

Performance evaluation of a hybrid heating system combined a groundwater source heat pump with an existing fuel oil heater for a horticultural greenhouse

ABSTRACT This paper reports a new hybrid heating system (HHS) installed in a horticultural greenhouse to lower the impact of high and unstable fuel prices on the greenhouse operation cost, to save the energy necessary to heat the greenhouse, and to reduce CO2 emissions. The HHS consisted of a groundwater source heat pump system for basic heating and an existing fuel oil heater for peak heating. The performance of the HHS, including the fuel oil and energy savings, and CO2 emissions reduction, was evaluated based on measurements during a heating period from November 2014 through May 2015. The results show that, comparing with only using the existing fuel oil heater to heat the greenhouse, the HHS can save 74.4% fuel oil and 22.8% energy, and reduce 35.5% CO2 emissions. In order to further increase the performance of the HHS, the operating control of the HHS, indoor hot air delivery system, and local thermal insulation of the greenhouse were improved. Performance evaluation based on measurements from November 2015 through May 2016 shows that the improved HHS can save 88.0% fuel oil and 35.9% energy, and reduce 48.7% CO2 emissions, which are significantly higher than those of the HHS before improved. Moreover, the comparison indicates that the performance of HHS was almost not changed with three different groundwater pumping rates tested herein. The proposed HHS is particularly suitable for transforming conventional fossil heating systems of horticultural greenhouses into a more energy-saving and thus sustainable heating system with a comparatively low initial cost.

Experimental Study on Automatic Switching of Solar Coupled Groundwater Source Heat Pump System

There have been few practical applications of solar coupled groundwater source heat pump (GWHP) systems in large public buildings, and data on this technology are scarce. A solar coupled GWHP system was investigated in this study. The system uses an underground water source heat pump system for heating in winter, cooling in summer, and providing part of the domestic hot water, and it also uses a solar energy system to prepare domestic hot water. These two types of energy are complementary. The system was tested throughout the cooling season. This experiment ran from May 10, 2021, to September 10, 2021. The results show that the system can guarantee the indoor design temperature and the supply of domestic hot water. The solar water heating system operated for 1233 min in the summer; hot water (2334 m3) was prepared. During the summer, the average energy efficiency ratio of the GWHP unit was approximately 4.88. The energy efficiency ratio of the entire system was approximately 3.34. Such projects can play a key role in demonstrating this type of system.

Energy consumption analysis of a ground water-source heat pump for the plant factory based on TRNSYS simulation

The ground water-source heat pump system for the plant factory lacks a scientific operation strategy to solve the problem of high energy consumption in winter and summer. It is very difficult and uneconomical to change the operation conditions by experimental means to obtain actual operation data. The current study aims to build a TRNSYS simulation model of the ground water-source heat pump system of Shanghai Chongming Natural Light Plant Factory. For the heating season, the simulation of energy consumption was 2315 GJ. Compared with the actual energy consumption, the relative error is -0.98%, which indicates that the simulation results are accurate and the simulation model developed is appropriate and usable. Numerical simulations for the whole year on this basis yielded that the plant factory energy supply system operates from November to March with a heating energy consumption of 3530.84 GJ and from June to September with a cooling energy consumption of 1126.24 GJ. In most cases, the indoor temperature fluctuates within a reasonable range, but in the summer high-temperature season, the plant factory temperature will reach above 40℃, which seriously affects plant growth. After optimization, the plant factory stops production in July and August, and the system stops running, the results are that the optimized system can save 56% of the annual cooling energy consumption, totalling 767.48 GJ, which can reduce the costs by 160,318.05 RMB.

Analysis of the influence of heat source well parameters on pumping temperature of groundwater source heat pump

In this paper, MATLAB software is used to simulate the influence of parameters of different heat source wells on pumping temperature in groundwater source heat pump system. The absolute value of horizontal permeability coefficient of aquifer will not affect its pumping temperature, but when the permeability coefficient ratio increases from 1 to 10, the pumping temperature decreases by 1.1°C; When the specific heat capacity increases from 2000 kJ / m3 · °C to 3000 kJ / m3 · °C, the pumping temperature decreases by 0.8 °C; When the degree of thermal dispersion increases from 1m to 3m, the pumping temperature decreases by 0.4°C.

Suitability and feasibility study on the application of groundwater source heat pump (GWSHP) system in residential buildings for different climate zones in China

To alleviate the pressure of energy utilization of buildings, more attention was focused on the utilization of GWSHP (groundwater source heat pump) systems. However, there have been many debates on feasibility. This paper is to study the suitability and feasibility of GWSHP systems in different climate zones. A simulation model of a GWSHP system is established based on TRNSYS software in the severe cold climate zones A and B, cold climate zones, hot summer and cold winter climate zones, and the hot summer and warm winter climate zones. Simultaneously, the reliability and energy-saving benefits of GWSHP systems in typical residential buildings situated in different climate zones are deeply analyzed. Results reveal that the operating performance of GWSHP systems is considered as the best in the climate zones that need both heating and cooling loads for residential buildings. In contrast, the energy-saving benefits of the GWSHP system in typical residential buildings are deemed to be higher in the cold climate zones and severe cold climate zones. Overall, compared with the ASHP, the economy of the system is generally better based on economic analysis.

Numerical evaluation of the performance of a single-well groundwater source heat pump system in Beijing, China

Shallow geothermal energy is stable and clean. Using a heat pump to produce groundwater and realize heating and cooling can effectively prevent haze and reduce energy consumption. To reduce engineering costs, many buildings in Beijing, China, plan to utilize single-well groundwater source heat pumps. Numerical modeling is an effective way to gain an understanding of thermal transport processes. However, wellbore-reservoir coupling and the uncertainty of productivity due to geological parameters make simulation difficult. A wellbore-reservoir-integrated fluid and heat transport model is defined by T2Well simulator to predict the productivity of a typical single-well system, with consideration of complex geological factors. The model is validated by the analytical model developed in Beijing, China. The fluid processes in the wellbore are described by 1 D non-Darcy flow, and the reservoir 3 D fluid and heat transport processes are calculated. Six crucial factors satisfying a random distribution are used, and for a single well that can supply heat for an area of 9000 m2, the output temperature during the heating season ranges from 11°C to 15°C.

Performance evaluation of ground water-source heat pump system with a fresh air pre-conditioner using ground water

From the perspective of cascade utilization of low-grade energy stored in the ground water, a new type of ground water-source heat pump (GWHP) system with a fresh air pre-conditioner using the ground water (abbreviated to GWHP-FAP) is proposed in this paper. For the GWHP-FAP, the ground water will be firstly used to cool/heat the fresh air in a pre-conditioner, and then enters the condenser/evaporator of heat pump (HP) unit for the secondary utilization. Thus the low-grade energy stored in the ground water is maximally used, and the energy consumption of the whole HP system and buildings is reduced. The working principle and the air treatment schemes of the GWHP-FAP are described in detail in this paper. To evaluate the performance of the GWHP-FAP, an office building is taken as an example to apply the system, and six typical cities distributed in three different climatic areas in China, i.e., Beijing, Zhengzhou, Wuhan, Chengdu, Changde, Guangzhou, are selected to preliminarily discuss the applicability. The results show that the energy saving performance of the GWHP-FAP is very good. The GWHP-FAP compared with the conventional GWHP, its seasonal energy saving rates are respectively 39.2%, 34.2%, 30.1%, 36.7%, 28.4% and 16.6% for the six typical cities during the cooling mode.

Heat pump system assessment for a groundwater‐source municipal drinking water utility

Compared to a typical heating, ventilation, and air conditioning (HVAC) system, a groundwater source heat pump (GSHP) system should have lower operating costs and greenhouse gas emissions, providing economic and environmental advantages for a ground water‐based municipal water utility. This article describes a test of that hypothesis, involving simulations and evaluations of the economic performance of the above two systems for a model office building in five major U.S. climate zones. The cost–benefit analysis suggests that a GSHP system in climate zone 5 (Chicago‐region) has the best return on investment, whereas climate zone 2 (Phoenix‐region) is not economically promising. Relative to a reference HVAC system, the GSHP system has lower carbon emissions in each of the five climate zones, with the greatest reduction of carbon emissions occurring in climate zone 5 (Chicago‐region). Significance: When faced with decisions about hot water supply and space heating and cooling, relative to drinking water utilities that rely on surface waters, groundwater‐based utilities have ready access to groundwater source heat pumps (GSHPs) that should offer better energy efficiency and lower greenhouse gas emissions. These advantages, however, will depend on regional climate conditions and the course of electrical energy. A better understanding of GSHP performance in different climate zones will provide the information needed to make these decisions. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13047, 2019

Dynamic exergoeconomic analysis of a heat pump system used for ancillary services in an integrated energy system

The integration of different energy sectors, such as the electricity and heating sector, is an effective way to integrate large shares of renewable energy into the energy system. Heat pumps allow efficient heat production based on electricity. As such, they may be used to provide two different services - the generation of heat and the provision of demand flexibility as ancillary services for the power system. The paper presents a method to assess the impact of providing demand flexibility on the performance of the conversion system based on a dynamic exergoeconomic analysis. A way to allocate the cost of heat and flexibility products based on the difference in exergy destruction was proposed. The method was applied to a case of a groundwater-source heat pump system supplying a district heating island system. It was found that providing demand flexibility causes higher exergy destruction, mainly due to heat losses during storage and the need to reheat the fluid using an electric heater. The major part of the additional exergy destruction was not related to heat pump regulation. When providing flexibility the overall cost of the system increased and according to the proposed allocation, demand flexibility accounted for 12% of the overall cost.

Study on Optimization of Underground Water Source Heat Pump

Based on the study of groundwater source heat pump air conditioning system, the thermodynamic characteristics of the water source heat pump system are analyzed in detail. This paper analyzes the energy saving optimization of a new type of underground water source heat pump system, making the groundwater source heat pump system more efficient and energy saving. Based on the theory of thermal economics and quantitative analysis, five independent variables are selected as the variable parameters of the thermal economic analysis after designing the objective optimization function. The exergy efficiency under several variable values are discussed, and then a comparative analysis is carried out. Finally, the parameters of the traditional water source heat pump and the optimized new water source heat pump are compared through the experiment. We found that the compressor power consumption of traditional underground water source heat pump system is greater than that of the new underground water source heat pump system. The exergy efficiency of the new underground water source heat pump system is high and the annual total cost is low. So the water source heat pump system has higher exergy efficiency, better economic and better exergy efficiency after optimization design.

Optimization model analysis of centralized groundwater source heat pump system in heating season

The ground-water heat-pump system (GWHP) provides a high efficient way for heating and cooling while consuming a little electrical energy. Due to the lack of scientific guidance for operating control strategy, the coefficient of performance (COP) of the system and units are still very low. In this paper, the running strategy of GWHP was studied. First, the groundwater thermal transfer calculation under slow heat transfixion and transient heat transfixion was established by calculating the heat transfer simulation software Flow Heat and using correction factor. Next, heating parameters were calculated based on the building heat load and the terminal equipment characteristic equation. Then, the energy consumption calculation model for units and pumps were established, based on which the optimization method and constraints were established. Finally, a field test on a GWHP system in Beijing was conducted and the model was applied. The new system operation optimization idea for taking every part of the GWHP into account that put forward in this paper has an important guiding significance to the actual operation of underground water source heat pump.

Performance analysis of ground water-source heat pump system with improved control strategies for building retrofit

This paper presented a case study on performance analysis of ground water-source heat pump system (GWHP) for a hotel building retrofit. Splitting air-conditioner was used for cooling and coal fired boiler was used for heating in original system. The GWHP system could save electricity energy and water source consumption under improved operation methods compared with the common operation methods. In this study, the experimental average cooling coefficient of performance (COP) of the units and system were 5.53 and 3.29, respectively (from Jun. to Sep.). The average heating COP of the units and system were 4.45 and 2.79, respectively (from Nov. to Feb.). The primary energy consumption of GWHP system was reduced by 42.9% when compare with the original cooling/heating system in a year. The indoor air temperature fluctuated in comfortable range (19.3°C–24.4 °C) during test day in winter. The results show that the GWHP system was particularly suitable for this hotel under our improved operation methods. This renewable and environment-friendly technology could promote energy conservation and sustainability obviously for the hotel building.

Measurement and Analysis of the Groundwater Source Heat Pump System in Shenyang

IntroductionAs one of the pilot cities for renewable energy application, which is defined by Ministry of Housing and Urban-Rural Construction of the People's Republic of China, Shenyang has widely popularized and applied GSHP(Ground Source Heat Pump) technology in winter heating and summer cooling. MethodsThis paper uses the GSHP system of a residential district of Shenyang as an example to investigate, test and analyze the GSHP project. The test of the indoor temperature and humidity should be done after the buildings have achieved stable thermal. ConclusionsThe system had stable performance, which benefited the system to have long-term operation. Compared with traditional air conditioner, the operation cost of GSHP was lower and it saves about 21.39% annual operation cost, which leads to the result that GSHP is economic and energy saving. The paper focuses on the experimental verification, needs further simulation software to calculate the results. This project was financially supported by the National science and technology support plan sub-topic (2011BAJ05B01-04).