Solar8 vs. traditional PV module based on cells area

One of the most common arguments in favour of PVT concentrating systems is the higher electrical efficiency per cells area when compared with a regular PV module with the same cells area. In this situation and based only on the PV cells point of view, Solar8 has a considerable higher efficiency per cell area when compared with the PV module (Table 9). This result can be explained by the higher irradiation the cells receive due to the reflector concentration factor and the tracking system. The thermal output can be seen just as an additional output one can get by cooling down the cells.

Table 9. Solar8 and traditional PV module electric output comparison based on cells area. PV module inclination is 40° in Stockholm, 30° in Lisbon and 20° in Lusaka. Aceels=0.33m2.

Electric annual output per cells area (kWh/m2)

Stockholm (lat=59.2°N)

Lisbon (lat=38.7°N)

Lusaka (lat= 15.4°S)

Solar8 tracking N-S (50°C)




Traditional static PV module (25°C)




Ratio Solar8/PV module




For this simulation it was considered that the PV module has16% efficiency at 25°C, the same cells area as Solar8 and that they cover 90% of its glazed area.

It is important to notice that the thermal and electric outputs shown previously don’t take into account system distribution losses, array shading effects and load distribution.

4. Conclusions

With this study several conclusions can be taken not only for Solar8 but also perhaps to the general photovoltaic/thermal concentrating hybrids being developed:

1. Solar8 can be replaced by a traditional side-by-side system using less space and producing the same electric and thermal output.

2. 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.

3. One axis tracking around North-South direction is considerably better than tracking around an axis placed on East-West direction.

4. The global irradiation on a static surface is higher when compared with the beam irradiation towards a tracking concentrating surface.

5. The ratio between electric and thermal output decreases when Solar8 is moved to the equator where the beam irradiation values are higher.

6. This PV/T combination still present lower outputs when compared with the traditional side-by­side system for the same glazed area. It is possible to say that there is chain efficiency around the most important components in Solar8. If every part of this chain works accurately and perfectly integrated in the system, higher efficiencies can be achieved in future models.

3. References

[1] Measurement report: Test of PVT module “PVtwin”. IEA task 35. Danish Technological Institute.

[2] Duffie, J. A., & Beckman, W. A. (1980). Solar Engineering of Thermal Process. Wiley Interscience, New York.

4. Acknowledgement

This study was supported by SolNet — Advanced Solar Heating and Cooling for Buildings — the first coordinated international PhD education program on Solar Thermal Engineering.

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