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Wednesday, 24 February 2010 18:47
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5. Conclusions

The project HELIOTRAM - TPG, comprising 154 kWp of PV-modules directly coupled to the DC grid of the public transports of Geneva, has started production at the beginning of July 1999. The plant had been designed and optimised using the PVSYST software simulations, and a production of 1038 kWh/kWp/year had been foreseen (i.e. a total production of 160'000 kWh/year).

Up to now , the plant operated satisfactorily. About 60 days of detailed monitoring data have been analysed.

During design, two essential parameters were slightly misestimated. On the one hand the grid operating voltage has been raised from 630 to 650 V since our old measurements. On the other hand the thermal factors didn't take into account that cooling by ventilation is less efficient for horizontal modules than for tilted ones. Moreover, due to an asphalt covering, the overall roof temperature strongly raises with insolation.

These observations will lead to a yearly loss of about 5% by respect to the previsions, i.e. about 990 kWh/Kwp/year. Wiring ohmic losses are limited to 1.5%. Other losses of less than 3%, could be attributed to the module quality or mismatch by respect to the manufacturer specifications.

However, the real measured yield of the plant stays within some few percents of the foreseen production. The result of about 1000 kWh/kwp/year is far over the Swiss average yield of PV plants, and is a remarkable result for such a module layout, almost horizontal, which is one of the main special features of this plant.

References :

[1] Guidelines for the Assessment of Photovoltaic Plants :

Document A Photovoltaic System Monitoring
Document B Anlysis and Presentation of Monitoring Data.

CEC/JRC : Commission of the European Communities, Joint Research Centre, Ispra (Italy),June 1993.

[2] Pierre Ineichen, GAP, University od Geneva, Private communication.

Last Updated on Thursday, 25 February 2010 13:25