Abstract
In Canada, more than 80% of energy in the residential sector is used for space heating and domestic hot water (DHW) production. This study aimed to model and compare the performance of four different systems, using solar energy as a renewable energy source for DHW production. A novel microchannel (MC) solar thermal collector and a microchannel-based hybrid photovoltaic/thermal collector (PVT) were fabricated (utilizing a microchannel heat exchanger in both cases), mathematical models were created, and performance was simulated in TRNSYS software. A water-to-water heat pump (HP) was integrated with these two collector-based solar systems, namely MCPVT-HP and MCST-HP, to improve the total solar fraction. System performance was then compared with that of a conventional solar-thermal-collector-based system and that of a PV-resistance (PV-R) system, using a monocrystalline PV collector. The heat pump was added to the systems to improve the systems’ efficiency and provide the required DHW temperatures when solar irradiance was insufficient. Comparisons were performed based on the temperature of the preheated water storage tank, the PV panel efficiency, overall system efficiency, and the achieved solar fraction. The microchannel PVT-heat pump (MCPVT-HP) system has the highest annual solar fraction among all the compared systems, at 76.7%. It was observed that this system had 10% to 35% higher solar fraction than the conventional single-tank solar-thermal-collector-based system during the wintertime in a cold climate. The performance of the two proposed MC-based systems is less sensitive than the two conventional systems to collector tilt angle in the range of 45 degrees to 90 degrees. If roof space is limited, the MCPVT-HP system is the best choice, as the MCPVT collector can perform effectively when mounted vertically on the facades of high-rise residential and commercial buildings. A comparison among five Canadian cities was also performed, and we found that direct beam radiation has a great effect on overall system solar faction.
Highlights
Renewable and sustainable energy generation technologies have been a concern for scientists due to climate change, increasing greenhouse gas emissions, and limited fossil fuel resources
More than 32% of the energy used in Canada is in the building sector; more than 80% of this fraction is used for space heating and to generate domestic hot water (DHW) [1]
Many studies have been completed for DHW provision by solar systems such as solar thermal collectors, Photovoltaic/Thermal systems (PVT) collectors, and PV-resistance
Summary
Renewable and sustainable energy generation technologies have been a concern for scientists due to climate change, increasing greenhouse gas emissions, and limited fossil fuel resources. Solar thermal collectors are a common way to generate DHW directly from solar irradiation They are currently being overtaken by photovoltaic panels as the dominant method of solar energy production due to the decreasing manufacturing cost of photovoltaic panels. To improve photovoltaics’ efficiency by reducing the temperature of photovoltaic cells while simultaneously generating electricity and thermal energy, hybrid Photovoltaic/Thermal systems (PVT) have been studied by many researchers [2]. By summarizing the available published works, Rodriguez et al [7] found a strong relationship between theoretical and experimental prototypes of a single-tank direct solar-thermal heat pump. According to their findings, a 5.6 m2 solar thermal collector could maintain DHW for 150 L/day of consumption in Spain’s climate. Seara et al [8] showed that the COP of a direct solar-assisted heat pump is highly dependent on the solar irradiance availability and ambient temperature
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