Influence of boundary conditions and component size on electricity demand in solar thermal and heat pump combisystems. (15th January 2016)

• Record Type: Journal Article
• Authors: Poppi, Stefano; Bales, Chris; Haller, Michel Y.; Heinz, Andreas
• Is Part Of: Applied energy. Volume 162(2016)
• Page Start: 1062
• Page End: 1073
• Publication Date: 2016-01-15
• Subjects: Solar combisystem -- Heat pump -- Component size -- Simulation; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2015.10.190
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: A simulation study on solar thermal and heat pump combisystem with two climates and buildings has been made. Penalty functions were used to ensure that all variations of the parametric study provided the same comfort requirements. Variation of heat pump size was shown to affect total system electricity use differently in the different climates and buildings. Heat pump losses (defrosting, start/stop, thermal) have significant impact on the annual electricity use, highlighting the importance of modelling these effects explicitly. Abstract: Solar thermal and heat pump combisystems are used to produce domestic hot water (DHW) and space heating (SH) in dwellings. Many systems are available on the market. For an impartial comparison, a definite level of thermal comfort should be defined and ensured in all systems. This work studied the influence of component size on electricity demand for a state of the art solar thermal and heat pump system. A systematic series of parametric studies was carried out by using TRNSYS to show the impact of climate, load and size of main components as well as heat source for the heat pump. Penalty functions were used to ensure that all variations provided the same comfort requirements. Two reference systems were defined and modelled based on products on the market, one with ambient air and the other with borehole as heat source for the heat pump. The results show that changes in collector area from 5 to 15 m 2 result in a decrease in system electricity of between 305 and 552 kW h/year. Changes in heat exchanger size for DHW preparation were shown to give nearly as large changes in electricity use due to the fact that the set temperature in the store was changed to give the same thermal comfort in all cases. Decrease in heat pump size was shown to give a decrease in electricity use for the ASHP in the building with larger heat demand while it increased or had only a small change for other boundary conditions. Heat pump losses were shown to be an important factor highlighting the importance of modelling this factor explicitly.