Unglazed Photovoltaic Thermal Collectors in Heat Pump Systems

Abstract

Unglazed Photovoltaic Thermal (PVT) collectors provide very high efficiency for heat and electricity generation at low temperatures. Therefore they are particularly suitable to support the heat source of heat pump systems, where low temperature heat is required. In this combination the PVT collector improves efficiency in two ways-of the heat pump by additional low temperature heat and of the photovoltaic module by lower cell temperatures. An increase of 4% of the annual and up to 9% for the daily photovoltaic electricity production and a high collector yield of 450 kWh/(m² a) was measured at a pilot system between April 2009 and April 2010. As the improvement of the PV and heat pump efficiency depends strongly on the thermal PVT collector performance, efficiency measurements of five different unglazed PVT collectors have been carried out. They showed significant differences, e.g. the conversion factor 0 without electricity production varies from 0.33 to 0.73. Further, a simulation model for unglazed PVT-collectors is presented. It is based on thermal performance parameters of EN 12975 and PV performance data at standard test conditions and it further includes thermal collector capacity and condensation effects.

Performance indicators of photovoltaic heat-pumps

“…The nomenclature used for the HP technology and application is explained in Table 5.Ref.HP Tech.Syst. App.Exp/SimTime spanLocationG (W/m 2 )T amb (ºC)T c (ºC)[8]A-WW-HE8h (H)---- PVT grid-connected [51]A-WW-HE8h (H)----[52] bA-A/WSW-HE4 days (H)Hefei (China), Lat: 31.88ºN, Long: 117.25ºE60613.731.9[53]A-WW-HE7h (H)Hefei (China), Lat: 31.88ºN, Long: 117.25ºE60315.833.9[54] bA-A/WSW-HS8h (H)Hefei (China), Lat: 31.88ºN, Long: 117.25ºE---[55] bA-WW-HS3h (H)-8002549.0[56] bA-WW-HE5h (H)-7003657.0[57] aA-A/WSW-HE1 year (Y)Frankfurt (Germany), Lat: 50.7ºN, Long: 8.41ºE2611320.0[58] bA-AS-HE8h (H)-83722.147.2[59] bA-AS-HE9h (H)Coimbatore (India), Lat: 10.98ºN, Long: 76.96ºE6503251.5[60] bA-WW-HE1...…”

Simulation Study of Building Integrated Solar Liquid PV-T Collectors

“…Contrary to PV modules cooled by air, PV-T liquid collector concept seems to be more suitable for BIPV applications if combined with efficient use of low temperature heat, for example, for cold water preheating, swimming pool heating circuits, or primary circuits of heat pumps. Several studies have been led on combination of unglazed PV-T collectors with heat pumps [7,8] or floor heating [9]. Unglazed PV-T liquid collectors are suitable to applications with priority of electricity generation and waste heat removed from cells is a byproduct at low temperature level with worse usability than in standard solar thermal collectors.…”

Photovoltaic heat-pumps for cooling applications

“…This is precisely the indicator that is independent from the climatic conditions and the time span of the measurement, and that makes PV systems actually comparable. [66] To show that the PRSTC,ref is more stable than the others, Figure 16 presents the monthly values obtained for these three indicators for the reference [99], located in Naples. It is easy to observe how the variability along the year is reduced with the PRSTC and practically eliminated with the PRSTC,ref.…”