Guides
Guides for people who design PV systems.
Each guide answers a question from PV design work: how to calculate it, which rules apply and where the figures come from.
- String sizing and Voc in the coldThe most and fewest panels per string, worked out step by step with real datasheets.
Snow and wind loads on solar panelsFrom ground snow load and reference wind speed to load per m², wind zones and the c/c spacing of fixings.
East–west or south on flat roofsMore kWp per m² or more kWh per kWp – the comparison with figures for four locations, ballast, walkways and fire safety.
Shading losses on solar panelsNear shading, horizon and rows – and why a partly shaded panel loses more than its share.- Battery sizing for solar PVSelf-consumption, hourly readings, the knee where the next kWh adds less, hourly prices and backup power.
Row spacing for ground-mounted PVThe formula for unshaded row spacing, ground coverage ratio (GCR) and worked examples for four latitudes.
How the guides are structured
First a short answer to the question, then the background and the formula or worked example, with values from the manufacturers’ datasheets. One section shows how the same thing is done in Ritwerk, another what applies in Sweden, Germany, Spain and Italy.
The guides explain how to do the calculation. The applicable standard, the authorities’ rules and the manufacturer’s installation instructions take precedence.
Figures with a source and a date
Standards, subsidy rules and datasheets change. Every figure in the guides has a source, and the date shows when it was checked. If you see something that has changed, write to info@ritwerk.se.
Questions and answers
Questions and answers
Who are the guides written for?
For PV installers and designers who size strings, mounting systems and batteries and want to see how the calculations work, with figures from real datasheets and sources.
Do the guides apply outside Sweden?
Yes. The calculations follow the same principles across Europe, but the values and rules differ, for example in the national choices in the load standards. That is why each guide has a section on what applies in Sweden, Germany, Spain and Italy, with a source for every rule.
Do the guides replace the standards?
The guides explain how to do the calculation and where the rules are written. The applicable standard, the authorities’ regulations and the manufacturer’s instructions take precedence, and you should have them in front of you when you design.
Try it on a real roof.
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