What performance should one expect from a photovoltaic system, and how does one evaluate the real-time performance against a 3rd party system?
There are many ways to install solar panels. Ground vs. roof mounted, hard tie vs. ballasted, stationary vs. tracking etc. and there are appropriate applications for each. No two installations are the same, so how does one compare against normalized data? Panels are rated using the Standard Testing Conditions (STC), but those conditions are rarely present. Therefore, the trend is to establish the kWh/kW/year, but that rate is too infrequent, too difficult to measure, and even more difficult to analyze.
Also, the designer must produce an energy model accounting for weather, solar data, shading, panels, inverters, etc. A good model is able to produce an accurate seasonal production profile, but individual, unique days do not match up.
So what can you do?
Find open sources of real-time data. For example, the Kortright Centre (just north of Toronto) has established a performance verification facility, aptly named Photovoltaic Performance Verification (PVPV) to compare solar panels that qualify for domestic content under the OPA’s FIT rules, side by side. The results are public, and in real-time. An analyst can compare their data against www.pvpv.ca, or compare panels against their counterparts to observe performance. Once the major independent variables (shading and orientation) are factored, the results will become predictable.
Dave Ferguson, C.Tech, BA, G3