Luis Ricardo Bernardo*, Bengt Perers, Hakan Hakansson and Bjorn Karlsson

Energy and Building Design Division, Lund Technical University, Box118 SE-221 00 Lund, Sweden
* Corresponding Author, Ricardo. Bernardo@ebd. lth. se

Abstract

The purpose of this study was testing and performance simulation of an innovative tracking hybrid solar system being developed by the Swedish Company Arontis. The Solar8 collector produces both electrical and thermal energy in one system. Its performance was compared with conventional photovoltaic panels and solar thermal collectors working side-by-side which are already on the market. The solar8 sample tested in Lund is a prototype designed for small demonstration projects and further development is ongoing.

The evaluation shows that the thermal collector has an overall heat loss coefficient of 3.1 W/(m[5] [6].°C), an optical efficiency of 65% and an electrical efficiency at 25°C of 8% per active glazed area. If we account the total glazed area instead, the thermal collector has an overall heat loss coefficient of 2.5 W/(m2.°C), an optical efficiency of 52% and an electric efficiency at 25°C of 6%. The electric efficiency of the bare cells is 16%. Annual performance simulations were carried out for the Swedish (Stockholm), Portuguese (Lisbon) and Zambian (Lusaka) climate. From the simulations one can conclude that: Solar8 can be replaced by a traditional PV-thermal collector side-by-side system using less space and producing the same electric and thermal outputs; tracking around one axis placed in North-South direction is considerably better then tracking around an axis set on East-West direction; the global irradiation on a static surface is always higher when compared with the beam irradiation towards a tracking concentrating surface; the ratio between electric and thermal output decreases when Solar8 is moved to the equator.

Keywords: Solar8, Solar Hybrids, Photovoltaic Thermal Concentrators, PVT

output is limited by the output coming from the poorest cell since all the cells are series connected. This is one of the challenges to overcome in this new technology. Local diodes installed in each cell can be able to bypass the current over the poorest cells and help reducing the problem with uneven radiation.

It is important to notice that the production of both heat and electricity is favoured by lowering the operating temperature. However a minimum water temperature is generally required by the given application involving higher working temperature on the cells. Due to lower insulation, the hybrid system thermal losses are higher when compared to a normal solar collector. Hence, it is expected that a flat plate hybrid system will deliver approximately 10% less electricity and 10% less heat compared to a thermal collector beside a PV module with the same cells amount [1]. It is also important to have in mind that when an electric load is connected to the PV cells, the thermal efficiency is further decreased since part of the radiation is converted into electricity. [7]