Air-Source Integrated Heat Pump System Development – Final Report

Experimental investigation on heating performance of solar integrated air source heat pump

This work analyzed an air-source heat pump with an integrated adsorption thermal storage component for residential applications. The application of high density storage materials allows a building to meet its onpeak heating and cooling demands without interruption using thermal energy stored during off-peak hours. A simulation model was developed using Engineering Equation Solver (EES) to predict the performance of the system in four different climate zones: Chicago, San Francisco, Bern, and Tokyo. R134a and CO2 (R744) were considered as heat pump working fluids. The analysis was conducted assuming the heat pump would provide for space heating, and hot water heating. The results show that thermal energy saved during offpeak hours can be applied during on-peak hours, effectively reducing the maximum electricity demand and annual utility costs. The CO2 heat pump system has a higher seasonal performance factor (SPF) than the R134a heat pump system due to higher compressor efficiency. Additionally, a cost-benefit analysis shows that the payback period for the thermal energy storage components strongly depends on an on-peak/offpeak electricity charge difference.

In South Africa, there is an ongoing constraint on the electricity supply at the national grid to meet the demand. Eskom is implementing various measures such as the Integrated Demand Management and the promotion and encouragement of the use of energy efficient devices like an Air Source Heat pump (ASHP) water heater to replace the high electrical energy consuming conventional geysers for sanitary hot water production. The ASHP water heater market is fast gaining maturity. A critical mathematical model can lead to performance optimization of the systems that will further result in the conservation of energy and significant reduction in global warming potential. The ASHP water heater comprises of an ASHP unit and a hot water storage tank. In this study, a data acquisition system (DAS) was designed and built which monitored the energy used by the geyser and the whole building, the temperature at the evaporator, condenser, tank outlet hot water, tank inlet cold water, the ambient temperature and relative humidity in the vicinity of the ASHP evaporator. It is also worthy to mention that the DAS also included to a flow meter and two additional temperature sensors that measured the volume of water heated and inlet and outlet water temperature of the ASHP. This work focused on using the mathematical equation for the Coefficient of Performance (COP) of an ideal Carnot’s heat pump (CHP) water heater to develop basic computation in M-file of MATLAB software in order to model the system based on two reservoir temperatures: evaporator temperatures (Tevp) of 0°C to 40°C (approximated to ambient temperature, Ta) and condenser temperatures (TCon) set at 50°C, 55°C and 60°C (approximated to the hot water set temperature of 50°C, 55°C and 60°C) respectively. Finally, an analytical comparison of a CHP water heater to the practical ASHP water heater was conducted on a hot water set point temperature of 55°C. From the modelling results, it can be deduced that at 0°C Tevp, the COP was 5.96 and 2.63 for CHP and ASHP water heater respectively, at a hot water set temperature of 55°C. Above 20°C Tevp, the rate of change of COP increased exponentially for the ideal CHP system, but was constant at 0.01/°C for the practically modelled ASHP water heater.

Renewable energy systems have received considerable attention as a sustainable technology in the building sector. Specifically, the use of ground-source heat pump (GSHP) and air-source heat pump (ASHP) for heating and cooling of buildings is increasing rapidly, and the combination with photovoltaic (PV) systems and heat pump systems provide energy savings and environmental benefits. This study investigates the feasibility of replacing conventional heating and cooling systems in a multifamily, residential building with GSHP and ASHP systems and their combination with PV. The integration of PV with GSHP and ASHP systems presents an opportunity for increased solar energy usage resulting in a reduction of electricity demanded and a reduction of emissions of greenhouse gases. To analyze different heat pumps systems with and without PV, system modeling and computer simulations are performed with RETScreen Expert software.A multifaceted verification and validation study is conducted for the system model and computer simulation. The important objective of this part of the study is to understand and develop confidence for modelling individual studies in RETScreen Expert software. To accomplish this, RETScreen Expert is used for modeling and simulating the performance of PV systems in several geographical locations, including Fort Wayne, IN. A comparison is made to performance predictions from System Advisory Model (SAM) software. In addition, a study is done to compare predictions from both software to previously published data.In the further phase of the study, eQUEST software, a tool for building energy simulation is used to predict outputs such as electricity consumption, heating loads, and cooling loads for the multifamily residential building considered in this study. These outputs, as well as, building parameters are used as inputs to RETScreen Expert. Since, this study focuses on modeling and simulating the heating and cooling systems coupled with PV for feasibility analysis, only a few minor modifications to the eQUEST default settings are made.The outputs from eQUEST are used as inputs to RETScreen Expert and analysis of ASHP and GSHP systems, as well as their combination with a PV system are performed. The results include the technical performance and financial model of each system, which can be used to indicate feasibility. The results show that both GSHP and ASHP systems are environmentally friendly and reduce energy consumption. These systems are economically feasible, with payback periods of under 10 years, when electricity prices are high. When combined technology is preferred, PV-GSHP systems are more environmentally friendly and have fuel savings far better than any other proposed systems. But the feasibility of the both the GSHP and PV-GSHP systems strongly depends on loop installation cost.

In this study, the design strategy for hybrid ground source heat pump (GSHP) systems consisting of GSHP and air source heat pump (ASHP) is investigated with a focus on the early design stages of an air conditioning system for a commercial building. A design procedure for determining the capacity ratio of the GSHP and ASHP is presented. Then, conservative values of the design parameters for the design process are described. A case study conducted according to the introduced procedure showed that the capacity ratio of GSHP and ASHP is influenced by the magnitude of the peak load of the building and building site conditions, as well as the configuration of ground source heat exchangers. Furthermore, an effort to reduce the peak load would increase the capacity ratio of the GSHP. It was shown that the capacity ratio would be approximately set by the site conditions, which can be a dominant constraint on GSHP capacity design. Finally, in the initial design phase, a design practice with conservative design values was instituted that would help in determining the capacity ratio and the configuration of the ground source heat exchangers.

Long-term energy and exergy analysis of heat pumps with different types of ground and air heat exchangers

Heat pump systems are promising technologies for current and future buildings and this research presents the performance of air source heat pump (ASHP) system. The system was monitored, analysed and simulated using TRNSYS software. The experimental data were used to calibrate the simulation model of ASHP. The specific climate conditions are evaluated in the model. It was noticed for the heating mode that the coefficient of performance (COP) varied from 1.98 to 3.05 as the outdoor temperature changed from –7.0 ºC to +5.0 ºC, respectively. TRNSYS simulations were also performed to predict seasonal performance factor of the ASHP for Vilnius city. It was identified that seasonal performance prediction could be approximately 15% lower if frost formation effects are not included to air-water heat pump simulation model.

Aiming at the performance deterioration of air source heat pump at low temperature in cold area, an air source heat pump system with sodium chloride aqueous solution as low temperature phase change heat storage material was proposed to increase the air inlet temperature of the unit under low temperature conditions and improve the low temperature performance of the heat pump unit. The system form, unit energy consumption model, and economic model were given, and the operating economy of the traditional electric auxiliary heat air source heat pump system and the phase change heat storage air source heat pump system were compared through computational intelligence powered methods. On this basis, the operation economy of the heat pump system using different concentrations of sodium chloride solution as the heat storage material was simulated and optimized, and the operation efficiency and energy-saving performance of the system were analyzed by taking an actual residential building in a cold area as an example. The simulation results showed that the Heating Seasonal Performance Factor (HSPF) of the heat pump system using 8.5% sodium chloride aqueous solution as the heat storage material is 2.24, and the HSPF of the traditional electric auxiliary heat pump system is 1.83. Compared with the traditional electric auxiliary heat pump system, the phase change heat storage heat pump system saves heating energy consumption by 19.6% and defrosting energy consumption by 38.8%. The heat pump system using 10% sodium chloride aqueous solution as the heat storage material has the best operating economy, and the system HSPF is 2.33, which saves heating energy consumption by 23.2% and defrosting energy consumption by 34% compared with the traditional heat pump system. The operation condition of phase change heat storage air source heat pump system is stable, and the system performance is significantly improved.

Feasibility Analysis of Building Heating System Based on Thermal-Economical Evaluation

Performance analysis on compression-assisted absorption heat transformer: A new low-temperature heating system with higher heating capacity under lower ambient temperature

TRNSYS simulation software was used to modify a validated Air Source Heat Pump (ASHP) model in an Archetype Sustainable House (ASH) in Toronto. In this model, a Building Integrated Photovoltaic-Thermal Collector (BIPV/T) was coupled with ASHP. The PV/T system arrangement was considered as a part of the south-oriented roof of the house. The warm air generated in the BIPV/T collector was considered the source of the heat pump for heat production. The coupling of BIPV/T and ASHP enables a highly efficient heating system in harsh winter conditions. The developed TRNSYS model of the house along with integrated PV/T system with ASHP was simulated for the whole year to predict the hourly outlet air temperature, thermal energy and electricity obtained from the PV/T array. The results from the simulation were used to estimate the saving in energy and cost as well as to predict the electricity related GHG emission reduction potential from the PV panels. Monthly greenhouse gas (GHG) emission credit from PV production based on hourly GHG emission factor was obtained; the results showed that annual GHG emission due to electricity demand by the ASHP was reduced by 225 kg CO2 (19.3%) when the heat pump was integrated with the PV/T array. Also, in this study, the annual electricity cost credit from PV production based on Time-of-Use (TOU) and the reduction in electricity cost of the heat pump when connected with PV/T systems was calculated and compared with the cost of working the heat pump alone. The results show that there is a saving of $500 in annual electricity bills and GHG emission credit of 862.6 kg CO2 from renewable electricity generation.

With the increasing amount of building renovations in Austria, the potential increases for replacing conventional national gas heating systems with heat pumps (HP) and thereby reduce CO2 emissions particularly when combined with solar photovoltaics (PV). The Austrian subsidization scheme for HP and PV systems are different for every state, creating confusion and inconstancy for potential adopters. This study provides a parametric techno-economic analysis of PV + HP systems to identify the critical economic parameters on profitability and make policy recommendations. A case study in Vienna is modelled using demand from the Building Model Generator and black box efficiency models for the HP and PV simulated with hourly time steps. The results show that both air-source and ground source heat pumps are currently profitable with PV under current subsidy schemes. The benefit-to-cost ratio (BCR) is highly influenced by capital costs and subsidies, however natural gas prices have the greatest influence. Increasing natural gas prices by 0.01 €/kWh, or 17%, is enough to replace all other complicated subsidies for both HP and PV. This is equivalent to a carbon emissions price of 33 €/ton and could result in a reduction of CO2 emissions in multi-family houses by approximately 45%–60%.

A significant part of energy in Norway is utilized for space heating due to the cold climate and heat pump technology has gained popularity in the country for space heating. According to the European heat pump association, Norway has the most heat pumps per capita in Europe, providing 16 TWh of heat energy annually. This review paper discusses the most common types of heat pumps in Norway. A comparison between the performance and payback time of different types of heat pumps in Norway is presented. Ground source heat pumps are more suitable than air source heat pumps due to maintaining a higher coefficient of performance during cold periods. The amount of thermal energy extracted using ground source heat pump systems is estimated to be 3 TWh and expected to be 8 TWh by 2030. However, more than 90% of heat pump installations in Norway are air source heat pumps. Compared to air source heat pumps, ground source heat pumps face many challenges, such as high initial cost, lack of public awareness, and insufficient professional workforce. The sales of heat pumps dropped by 13% in 2020, mainly due to the Covid-19 impact on the market. However, the sales increased significantly in 2021 due to the ongoing energy crisis and increase in energy prices.

Researchers at the Department of Energy (DOE) facilities at Oak Ridge perform a variety of basic and applied research involving lasers and laser technology. One of the major strengths at Oak Ridge is the combination of core capabilities in optical materials, optical diagnostics, and sensors. Communities benefiting from these core capabilities include environmental, biomedical, and industrial sponsors. Industry can interact with Oak Ridge in a variety of ways; with Cooperative Research and Development Agreements (CRADAs), through Work for Others (WFO) programs, and as User Center participants. Oak Ridge is also active in sponsoring workshops and symposia for industrial participants like the recently held (December 1993) “Optical Diagnostics in Manufacturing and Process Control” symposium. In this paper, an overview of a selection of laser technologies residing at Oak Ridge is provided. Examples of the application of these technologies are given as well as overviews of several on-going CRADAs with industrial partners.

Model development and numerical analysis of a vertical falling film absorption heat pump