Energy Yield

The study of the efficiency of photovoltaic modules in outdoor conditions allows determining their correct operation and to detect abnormal behavior. Most efficiency models developed use experimental data that are difficult to obtain as they require specialized equipment and a long measurement time under laboratory conditions to identify or adjust the model parameters. In this article, we propose a linear equation that estimates the efficiency of photovoltaic modules using irradiance and back panel temperatura measurements as input variables. The main contribution is that the parameters of the proposed model can be obtained directly from the reference information (IEC61853-1 power values) without any data regression. The proposed model was validated using experimental data obtained from three different climatic zones during a whole year. The model shows the best fit to the data of four analyzed models, and its normalized root mean square deviation for all photovoltaic modules is less than 3.6%; this dispersion could be explained by the fact that the outdoor data have an uncertainty of around 3.0%

The number of solar photovoltaic (PV) systems installed in Europe has drastically increased over the last few years, mostly thanks to the advantageous feed-in tariffs set in by each country’s government. A relatively little fraction of the energy production data of these PV systems has been analysed, and
as a consequence, there still remain wide gaps in the knowledge of the real-world performance of these PV systems. This feedback from the field is nevertheless important for the future development of the PV industry and for the establishment of new renewable energy development programmes by the respective governments.

We have analysed the operational data monitored at more than 31,000 PV systems in Europe. These installations comprise residential and commercial rooftop PV systems distributed over 9 different countries, including multi-megawatt PV plants installed in the South of Europe. The PV systems were installed between 2006 and 2014. The mean Energy Yield of the PV systems located in the four reference countries are 1115 kWh/kWp for France, 898 kWh/kWp for the UK, 908 kWh/kWp for Belgium, 1450 kWh/kWp for the PV plants in Spain mounted on a static structure, and 2127 kWh/kWp for those mounted on a solar tracker in Spain. We suggest that the typical PR value for the PV systems installed in 2015 is 0.81. We have observed that the performance of the PV system s tends to increase when the peak power of the PV systems increases. We have found significant performance differences as a function of the inverter manufacturer, and the PV module manufacturer and technology. We have found an improvement of the state-of-the-art, in the form of an increase in performance in the yearly integrated PR of around 3 to 4% over the last seven years, which represents an increase of about 0.5% per year.

The wide disparity in yearly integrated performance ratio, between 0.6 and 0.9, implies that there is a difference of some 30% between the best and the worst performers. Ideally, the PV sector should aim at reaching PR values over 0.84 for most of the PV systems to be installed in the future. More quality controls and further improvement in the state of the art are therefore a very promising option towards a leap in overall performance, which could lead to an average value of PR over 0.84, representing an improvement in performance around 10%, and a corresponding reduction in LCoE of the same order of magnitude.