LowEx solar building system: Integration of PV/T collectors into low exergy building systems

The integration of an unglazed solar photovoltaic/thermal (PV/T) collector to a ground source coupled heat pump system has the potential to increase the heat pump performance to a minimal SPF of 6 by providing higher average source temperature. Furthermore the integration of a PV/T collector increases the system stability and introduces new degrees of freedom in the design of renewable and zero emission energy supply for buildings. This study shows the design of a low exergy (LowEx) solar building system and its potential for the total solar energy building supply in moderate climates as in the EU and northern China. The collector array is dimensioned according to the building heat load. The area can be maximized to provide the entire yearly heat demand, without the problem of excess collector heat in summer, by employing solar ground regeneration. The low-temperature thermal collector supplies the heat needed by the heat pump to provide hot water and heating of the building, while the PV production exceeds the annual electricity demand of the heat pump and auxiliary pumps. Different hydronic circuit layouts and controls have been evaluated by simulation according to reference buildings of SHC IEA task 44 with regard to the criteria of simplicity and reliability in order to realize LowEx solar buildings. An implementation of a system that maximizes the thermal system input considering minimal internal exergetic losses is presented. A PV/T collector has been realized as prototype, installed and tested in LowEx building systems. (C) 2012 The Authors. Published by Elsevier Ltd.