Available solar energy

[Tattynure]

Hi all,
I am considering installing PV panels to supply my household energy. Is it possible to use my Cumulus solar radiation data from the last couple of years to establish how much sunshine I receive annually and then use this to establish how the likely output from my panels?

I am aware that performance figures for panels are pretty unreliable, but at least this may give me some idea of the likely returns so that I can optimise my array. Over the last 5 years, my average loading is 14 kWhr/day, with peak loads around 20 in v cold winter spells.

Thanks,
Peter

[steve]

I don't know how valid this is in practice, but you could do this:

You have your W/m2 value logged every N minutes in the Cumulus logs. As an approximation, assume that the sun was shining at the same strength for the entire N minutes, so multiply each value by N and total the results over whatever period. This gives you your input Watt-minutes per square metre for your chosen period. Divide by 60000 to give kWh per square metre. Multiply by the area of your proposed solar panels, but take into account their efficiency, e.g. if they are 50% efficient, divide by 2. The result is your expected output kWh over whatever period you chose.

[AllyCat]

Hi Peter,

Potentially, your data could be quite useful. AFAIK the Davis sensor has a similar frequency (colour) response to PV panels (about half of the useful energy is actually in the Infra Red) and the sensor has a "sine" characteristic, which represents a "flat plate collector". The data could be particularly valuable if the Davis sensor was tilted at a similar angle to that of the PV panels.

But Steve was being rather optimistic about the efficiency of PV panels, it's unlikely to be above 20% and maybe only 15%.

Cheers, Alan.

[Tattynure]

Many thanks, Steve. I'll give it a go.
Peter