Evaluation of a Dual Tank Indirect Solar-Assisted Heat Pump System for a High Performance House

Abstract

This work focused on the design and evaluation of an integrated mechanical system, which incorporated a dual tank indirect solar-assisted heat pump, that offsets spaceheating, cooling, and domestic hot water loads for a high performance house. A model of the system was developed to investigate the effects of various parameters on the performance of the system. These parameters included the tank configurations, the solar collector size and orientation, and heat pump size and controls. In addition, an experimental study was conducted to investigate the relationship between the heat pump load side flow rate, the heat pump performance, and the thermal stratification in the storage tank. The experimental results indicated that the coefficient of performance of the heat pump reduced with lower flow rates. However, lower flow rates could result in higher temperature rises across the condenser and greater levels of the stratification which could improve the overall performance of the system by reducing the auxiliary energy consumption. Results from the modelling and experimental work were compared and the experimental results were used to improve the heat pump performance map that was used in the simulations. The simulation results showed that the system could achieve a free energy fraction of 0.506 (neglecting energy draws from circulation pumps and fans) for space-heating, cooling, and domestic hot water. This result suggests that the system does have the potential of reducing energy consumption in the residential sector in Canada. iii Table of Contents iv List of Tables viii List of Figures x Nomenclature xiv u COP Uncertainty of the coefficient of performance u COPaverage Uncertainty of the average coefficient of performance u Q load Uncertainty of the accumulated energy transferred (kJ) u Pcomp Uncertainty of the accumulated heat pump energy consumption (kJ) uṖ comp Uncertainty of the heat pump power consumption (kW) uQ load Uncertainty of the heat pump heat transfer rate (kW)

Evaluation of Heat Pump Water Heater Performance and Optimization Strategies In Cold Climates

“…Chu conducted a sensitivity analysis with the TRNSYS model, and found the optimal values for the construction of the experimental apparatus through a sensitivity analysis of the free energy fraction. In this case, a free energy fraction, or portion of energy that is collected from the sun and not supplied by utilities, of over 50% could be obtained [25]. Both studies found that sizing the heat pump correctly was the most sensitive factors on economics and total energy consumption.…”

“…Chu designed and tested a solar assisted heat pump system to highlight the sensitivity of many advanced heat pump system parameters such as COP, flow rate, and heat pump capacity to system design parameters [25]. The importance of efficient thermal stratification was also noted.…”

“…Sterling and Collins [36], as well as Chu [25], have analyzed solar assisted heat pumps, that is, systems where the evaporator of the HPWH is connected to a solar collector to boost performance by raising the heat source temperature. Both studies used TRNSYS to simulate the performance of an indirect solar assisted heat pump system, and…”

Assessing the Impact of Rock-Bed Storage for Tempering Air-to-Air Heat Pumps

“…In the direct configuration, the solar collectors are integrated into the ASHP on the evaporator side, and the fluid circulating in the solar collector also serves as a refrigerant of the heat pump. Although direct systems demonstrate promising performance results, they are typically installed in climates milder than those of Canada (Chu, 2014). Contrarily, an indirect configuration is suitable for cold climates because the solar collector and heat pump form separate loops with an antifreeze solution and refrigerant, respectively.…”

“…As part of her study on solar-assisted heat pump system, Chu (2014) provided an extensive survey of different system configurations with integrated diurnal TES used for space-heating and domestic hot water supply in residential applications. It was highlighted that the system proposed in the thesis was unique for satisfying both the heating and cooling demand of a residential house with consideration of the Canadian climate.…”