  BIPV systems are small PV generation units spread out over the territory, and
whose characteristics are very diverse. This makes difficult a cost-effective
procedure for monitoring, fault detection, performance analyses, operation and
maintenance. As a result, many problems affecting BIPV systems go undetected.
In order to carry out effective automatic fault detection procedures, we need a
performance indicator that is reliable and that can be applied on many PV
systems at a very low cost. The existing approaches for analyzing the
performance of PV systems are often based on the Performance Ratio (PR), whose
accuracy depends on good solar irradiation data, which in turn can be very
difficult to obtain or cost-prohibitive for the BIPV owner. We present an
alternative fault detection procedure based on a performance indicator that can
be constructed on the sole basis of the energy production data measured at the
BIPV systems. This procedure does not require the input of operating conditions
data, such as solar irradiation, air temperature, or wind speed. The
performance indicator, called Performance to Peers (P2P), is constructed from
spatial and temporal correlations between the energy output of neighboring and
similar PV systems. This method was developed from the analysis of the energy
production data of approximately 10,000 BIPV systems located in Europe. The
results of our procedure are illustrated on the hourly, daily and monthly data
monitored during one year at one BIPV system located in the South of Belgium.
Our results confirm that it is possible to carry out automatic fault detection
procedures without solar irradiation data. P2P proves to be more stable than PR
most of the time, and thus constitutes a more reliable performance indicator
for fault detection procedures.
