| Work Detail |
Italian scientists have coupled a solar-powered air-cooled heat pump with a thermal energy storage water tank to supply hot water to a residential building as a retrofit solution.
Researchers at the University of Bologna (Italy) have developed a new retrofit solution for domestic hot water (DHW) that uses a photovoltaic-powered air-source heat pump system that relies on a water tank for heat storage. thermal energy.
The system is expected to replace traditional electric boilers and aims to decouple energy production and demand. According to the scientists, the novelty of their approach consists in creating two levels of thermal energy storage to take advantage of the full potential of the photovoltaic system.
“A first level of storage is provided by a large centralized water tank that is equipped with a programmable control system to use the water tanks as a buffer and let the heat pump work in the desired conditions,” they explained. “The second level of energy storage is provided by innovative thin and modular decentralized tanks, hereinafter called e-TANKs, dedicated to the production and storage of ACS, which provide greater thermal efficiency and, at the same time, greater autonomy. of users through local storage installed in each home.”
The e-TANK consists of a water tank and a hydronic module designed by the Austrian specialist Pink GmbH. Both components are wall-mounted on a steel frame. The tank is also equipped with an internal helical heat exchanger that is connected to a 2-pipe hot water network. This network can be used both for charging DHW storage tanks and for heating. It can run at high temperatures during charging periods during the day. It presents lower heat losses from the pipe network and lower consumption of circulation pumps compared to conventional boilers.
Using the TRNSYS software, which is used to simulate the behavior of transient renewable systems, the research group simulated the configuration of the proposed system in a residential building located in Catania (Sicily, southern Italy) and assumed that it could be powered by a photovoltaic system. 13.5 kW formed by 36 monocrystalline modules.
The electricity produced by the photovoltaic array could be consumed by a reversible air-water system, with a heat output of 26.0 kW and a coefficient of performance (COP) of 3.10, or stored in a 20 kWh battery. “The maximum temperature of the water supplied by the heat pump is equal to 65°C for an outside temperature between 5°C and 19°C”, the researchers say.
The academics compared the energy performance of the proposed retrofit solution with that of the existing system in the pilot building and found that the system achieved “desirable” thermal performance in both the loading and unloading processes.
"The result obtained through dynamic simulations indicated that the e-TANK system reduces the annual energy consumption for DHW production by more than 7,200 kWh, compared to the current DHW system," they explained. “A typical centralized system was shown to require about 11 times more electrical power for the circulation pump than the e-TANK solution.”
They also verified that, in a period of 20 years, the new solution has a life cycle cost (LCC) 6.1% lower than that of traditional boilers. "In addition, it turned out that the application of the proposed PV-BESS system for electricity generation reduces the necessary primary energy by 7.1 MWh/year, compared to the case where electricity is supplied by the grid," they stressed.
The team presented the new solution in the article “ Techno-economic analysis of a novel retrofit solution for the domestic hot water system: A comparative study ”. , published in Energy Conversion and Management . “The results of the present study for the pilot building are expected to be extended to a significant part of the existing European building stock,” he concludes. |
