There are several calculators available on-line for various aspects of solar design.
One excellent tool is the PhotoVoltaic Geographical Information System (PVGIS) which "provides a map-based inventory of solar energy resource and assessment of the electricity generation from photovoltaic systems in Europe, Africa, and South-West Asia."
The model algorithm estimates beam, diffuse and reflected components of the clear-sky and real-sky global irradiance/irradiation on horizontal or inclined surfaces. The total daily irradiation [Wh.m-2] is computed by the integration of the irradiance values [W.m-2] calculated at regular time intervals over the day. For each time step during the day the computation accounts for sky obstruction (shadowing) by local terrain features (hills or mountains), calculated from the digital elevation model.
It is often useful to be able to work off-line.
Julian Pearson volunteered me his own (Excel) spreadsheet that "calculates the duration of sunlight per day, at the latitude entered by the user, as well as the angle of the sun... works out the efficiency of the solar strike on the panel for each day of the year ... [it assumes] optimised conditions ... [with an unobstructed, unshaded] clear view south." He's happy for it to be distributed for free providing that the usual courtesies are respected: no messing with it, no charging for it or for use of it, and attribution for his work and that of the people he mentions in the spreadsheet.
One PC-based (paid-for) tool is the PVSYST PC application "for the study, sizing, simulation and data analysis of complete PV systems."
- See the on-line PVGIS Solar Irradiance Data tool.
- Underlying PVGIS is the EU's Solar Electricity Action SOLAREC programme (map of solar energy potential in Europe 12MB PDF).
- RenSMART Solar PV Comparison Table: table of the commonly offered solar pv panels available in the UK.
- Optimum Tilt of Solar Panels.
- RapidTables Voltage Drop Calculator.
- The PVSYST PC application "for the study, sizing, simulation and data analysis of complete PV systems."
- SMA's Sunny Design Web to help design PV systems, including storage.
- See PV Resources' software roundup.
- Midsummer Energy's solar panel calculator suggests that each Wp of panel will generate about 1Wh per day in winter in the UK and about 5Wh/day in the summer (and a yearly average of ~2.47Wh/day), so to cover nWh of base load year-round might require nWp of panel, plus maybe 20% for storage and conversion losses, and with a huge excess of capacity in summer.
- Spreadsheet calculator for optimal panel angle (xls) c/o Julian Pearson.
- See SolarHome, suppliers of solar heating and DHW systems in the UK. SolarHome's site lists the following handy conversions: 1kWh = 3.6MJ = 3412Btu = 0.03412Therms.
- Consolar has a useful sizing guide, for example: allow for 40l/person/day, allow between 80l and 100l per m^2 of collector (other sources suggest as little as 57l/m^2). Plus good sense such as to angle collectors at >45°C to maximise winter output and reduce overheating risk in summer.
- See Libre Software in Building design.