Polysun is a simulation software created by Vela Solaris AG, a spin-off-company of the Institut für Solartechnik (Institute for Solar Technology) at the Schweizer Hoch¬schule für Technik in Rapperswil, Switzerland. Over the years, the line of products that bear the name Polysun has grown to include a whole range of software products from an online version (sometimes offered free of charge by companies) to a Professional package for system designers, as well as a Designer package. The latter allows the user to simulate an unlimited number of generator fields as well as enabling the import of weather data – limited features in the other versions. The PHOTON lab tested the top version.
In our test, simulation results differed by an average 4.8% to the actual yields – a very good result indeed. A crosscheck carried out by the manufacturer even came up with an average difference of only 3.2%. The average difference between forecast and actual yields was 4%.
Both in the PHOTON lab and at the manufacturer’s premises, the yields calculated with the programme were consistently slightly too low: for two of the three reference systems by just 4%; for the third system by almost 10%. Economic viability calculations based on Polysun-generated forecasts include therefore a small safety margin.
Polysun is designed for installers, energy consultants and distribution businesses. Its user-friendly structure makes it the perfect solution for these target users. The software enabled project data to be managed in a clear and effective manner, allowing the comprehensive documentation of single client systems. The user can design a system in a matter of minutes, no background knowledge of simulation techniques is necessary. Setting options are slightly more limited than those in software packages that are more oriented towards in-depth scientific analysis. Parameters such as the albedo cannot be specifically adjusted for example. However, key parameters such as cable losses, degradation or the type of rear ventilation can be adjusted.
The modelling of systems is aided by a wizard that guides the user step by step in entering the main project and system features; the result is a functional system design that can be further refined. The fact that the software supports different system variants and allows the direct comparison of results is very useful in this context.
In addition to fixed-orientation systems, Polysun is also able to simulate module arrays with single or two-axis tracking systems. Polysun does not allow the modelling of off-grid systems. Likewise, the load profiles required for the calculation of the amount of electricity consumed for own use could not be read in the version we tested in the PHOTON lab. However, at the manufacturer’s site it was possible to determine domestic consumption using load profiles we provided. Although, to do this Vela Solaris employed a programme version that has not yet been released.
The software is able to simulate the effects of horizon shading. This is also possible through the import of external horizon files (from “Suneye” or other “.hor” files). Nearby shading sources such as dormers, chimneys and self-shading modules are not taken into account.
Databases include a wide range of modules and inverters that can be expanded independently, if required. An integrated data generator provides weather records for any location worldwide. The programme includes a simple economic viability calculation application that takes into account key acquisition costs, fixed and percentage maintenance costs as well as different types of subsidies. However, credit based variations, fiscal issues and funding conditions that vary on a regional basis are not considered.
Simulation results are shown in clear, detailed reports. All results may be represented graphically and may be exported or printed as picture files to provide more comprehensive documentation. In addition, results are summarized in a report and may be used directly by sales representatives to make proposals. Company logos and contact details can also be added to the documents.
Good simulation results, ease of use, comprehensive component databases and effective project management features already make Polysun an almost ideal tool for professionals. On our wish-list: a tool to analyse shading caused by surrounding objects, a way to account for load profiles and a graphical layout based on measurements. afi, cpo