Indirect Solar Assisted Heat Pump Research Articles

Multi-objective optimization of a solar-assisted heat pump for swimming pool heating using genetic algorithm

A proper assessment of heating systems for swimming pools should evaluate the compromise between comfort level and the willingness to pay for it. The present work presents a multi-objective optimization of indirect solar assisted heat pump systems for outdoor swimming pool heating. Four different configurations are reported; (air-to-water heat pump and three solar assisted heat pumps, air-to-water, water-to-water and a dual-source); and evaluated in six different locations (three location in Chile: Antofagasta, Santiago, and Concepción; and three locations in Brazil: Brazilia, São Paulo, and Florianópolis). The methodology approach configures two objectives optimization, the minimization of the Annualized Life Cycle Cost (ALCC) and the maximization of the comfort level offered by the swimming pool. The optimization scheme consists of using a combination of tools: the energy-savings potential of i-SAHP are evaluated using the TRNSYS software in combination with GenOpt; and the economic modeling and optimization are performed in the MATLAB environment, using an approximation model and variant of NSGA-II genetic algorithm for building the Pareto frontiers. The optimization results demonstrate that solar-assisted configurations present significant improvements in performance for almost all locations, reaching the same levels of comfort at lower ALCCs when compared with the ASHP configuration.

CFD modelling development and experimental validation of a phase change material (PCM) heat exchanger with spiral-wired tubes

Employing phase change materials (PCMs) for latent heat storage (LHS) application has a great potential to improve a solar thermal system performance. Despite this fact, the use of PCM in this area is quite limited due to the poor thermal conductivity of available PCMs. Therefore, heat transfer enhancement is one of the essential strategies that can overcome this obstacle. In this paper and related project, a PCM heat exchanger (HX) is purposely designed with spiral-wired tubes and integrated in an indirect solar assisted heat pump test system. Although the spiral-wired tube has not been applied in a PCM HX, it is expected to enhance significantly the PCM heat transfer and heat storage performance. To verify this and understand the PCM heat storage and releasement processes, a detailed 3D CFD model has been developed for the PCM HX and validated with measurements. The temperature variations and visualizations of the PCM during charging and discharging processes are therefore simulated and presented temporally. Furthermore, the effects of different inlet heat transfer fluid flow rates and temperatures on the PCM melting/solidification time are demonstrated in this study. Some significant simulation results have been obtained which can instruct efficiently the operation of the heat exchanger and its integration with the solar system.

Indirect expansion solar assisted heat pump system for hot water production with latent heat storage and applicable control strategy

Integration of renewable energy with energy conversion application for hot water production is a significant technology to be studied for industrial, commercial and residential proposes. It has been further enhanced since the international energy agency (IEA) puts effort to standardize such kind of technology. In this paper, a novel study has been carried out experimentally to control an indirect solar assisted heat pump (IDX-SAHP) system integrated with a latent heat storage (PCM) tank. The PCM heat exchanger tank was designed specially and controlled automatically which allowed storing excess energy during the day and releasing it when needed. In addition, a system control strategy has been purposely designed and implemented in a Building Management System (BMS) to ensure the stable and reliable system operations. The experimental results show that the PCM heat exchanger tank installation has a significant effect on the system operation stability and can improve the COP of the IDX-SAHP system at different weather conditions and a specified hot water load profile.

Effects of latent heat storage and controls on stability and performance of a solar assisted heat pump system for domestic hot water production

Solar assisted heat pump systems have been widely applied in domestic hot water productions due to their sustainability and stability in operations. However, their performance efficiency requires further improvement using advanced technologies such as energy storage with phase change materials (PCM) and optimal system controls. Accordingly, a test rig of a new indirect solar assisted heat pump (IDX-SAHP) system has been designed, built and instrumented. The IDX-SAHP system consists of three operational loops: solar thermal, solar assisted heat pump and load profile. A PCM heat exchanger tank was purposely designed and installed in the system solar thermal loop to store solar energy, when applicable, and release heat when required by the heat pump. In addition, an air cooling heat exchanger was also installed in the solar thermal loop to absorb heat from the ambient air for the heat pump. A detailed control strategy has been designed and implemented for the system for efficient operation in different modes and maintain constant load supply water temperature during an operational day. In different weather conditions of sunny and overcast, comprehensive measurements were carried out on the test rig and system structures with and without the PCM tank. Test results showed that the system could efficiently meet the daily domestic hot water demand and the PCM heat exchanger integration exerted a significant effect on system stability and performance efficiency. Quantitatively, the average COP of the IDX-SHAP system with a PCM tank could increase 6.1% and 14.0% on sunny and cloudy days respectively compared to systems without PCM tank integration.

Experimental Evaluation of Thermal Performance of Solar Assisted Vapor Compression Heat Pump

The thermal performance of indirect expansion solar assisted heat pump, IX-SAHP, was investigated experimentally under Iraqi climate. An Indirect-Solar Assisted Heat Pump system was designed, built, instrumented and tested. Experimental tests were conducted by varying the controlling parameters to investigate their effects on the thermal performance of the IX-SAHP such as cooling water flow rate, heating water flow rate, ambient temperature and solar radiation intensity. The investigation covered values of cooling water flow rate of (2, 3, 4, 5 l/min) and heating water flow rate of (2, 3, 4, 5 l/min) under meteorological condition of Baghdad from November 2014 to January 2015.
 The results indicated that the performance of the IX-SAHP is not dependent on the heating water flow rate. On the contrary of heating water flow rate, cooling water flow rate has significant effect on the thermal performance of the system. The COP of the heat pump system is decreased with increasing cooling water flow rate. The collector heat gain increase with increasing the solar radiation and ambient temperature, this leads to increase in COP from 2.2 to 2.39 as the ambient temperature and solar radiation increase from 9.9℃ and 268 W/m2 to 14.9 ℃ and 689 W/m2 respectively.
 

Modeling of an Indirect Solar Assisted Heat Pump System for a High Performance Residential House

The combination of solar thermal and heat pump systems as a single solar assisted heat pump (SAHP) system can significantly reduce residential energy consumption in Canada. As a part of Team Ontario's efforts to develop a high performance house for the U.S. Department of Energy's Solar Decathlon 2013 Competition, an integrated mechanical system (IMS) consisting of a SAHP was investigated. The system was designed to provide domestic hot water (DHW), space-heating, space-cooling, and dehumidification. The system included a cold and a hot thermal storage tanks and a heat pump to move energy from the low temperature reservoir to the hot reservoir. Solar thermal collectors supplied heat to the cold storage and operated at a higher efficiency due to the heat pump reducing the temperature of the collector working fluid. The combination of the heat pump and solar thermal collectors allows more heat to be harvested at a lower temperature, and then boosted to a suitable temperature for domestic use via the heat pump. The IMS and the building's energy loads were modeled using the TRNSYS simulation software. A parametric study was conducted to optimize the control, sizing, and configuration of the system. The simulation results suggested that the investigated system can achieve a free energy ratio (FER) of about 0.583 for the high performance house designed for the Ottawa climate.