Performance of a multifunctional PV/T hybrid solar window

A PV/T collector have been developed and evaluated at the department of Energy and Building Design at the
Technical University of Lund, LTH in Sweden. The PV/T, a “multifunctional solar window” made of PV cells
laminated on solar absorbers, is placed in a window behind the glazing. The solar window is built into a single
family house, Solgården, in Älvkarleö outside Gävle in the eastern part of Sweden. To reduce the costs of the
solar electricity, reflectors have been placed in the construction to focus the radiation onto the solar cells. In this
way expensive solar cells can be replaced by considerably cheaper reflector material. The tiltable reflectors give
the user a possibility to control the amount of radiation being transmitted into the building. The reflectors can
also be used to reduce the thermal losses through the window.
A model for electric and hot water production was developed. The simulation program, in Excel, can perform
yearly energy simulations where different effects such as shading of the cells or the glazing effects can be
included or excluded. The simulation can be run with the reflectors in an active, up right, position or with the
reflectors in a passive, horizontal, position. The simulation program was calibrated against a prototype window
placed in Lund in the south of Sweden and against the solar window in Solgården. The calculation model serves
as a basis for the module written for the simulation program TRNSYS. A “TRNSYS-deck” was built and
calibrated for the building Solgården.
Yearly simulations of the energy balance for a house with the solar window was compared to simulations where
the 16m2 solar window was replaced with an 8m2 normal window. The results show that the annual amount of
auxiliary energy is lower with a developed solar window, including low-e coating on the glazing, compared to
the normal window case. The developed solar window has considerable lower U-values than the existing solar
window.