Daily PV data where to get it ?

Capt'n Midnight

where would I get daily PV data for Dublin ? hourly would be better,

or a graph of power vs. % of time it was exceeded.

To size batteries you need the data of when the sun doesn't shine, so I'm surprised that I haven't found it easily.

Was there a thread where people uploaded spreadsheets ?

The met.ie data only lists full sunlight and a lot of our PV comes from diffuse light so not that useful.

quentingargan

Most PV systems come with logging, so it would be a matter of getting permission from someone to look at their data. I'd give you mine, but I am messing around with it at the moment so its offline (and I'm in Bantry)

When I have sized batteries, I have used a term called "black day equivalents". This gives the information on the longest likely period when power is below average. You need to create a login here to get that data for a set Long and Lat.

Q

Investing in lead Capt'n?

Global Solar Radiation in Joules/cm2 for Dublin_Airport

If you want to work it out on paper convert solar radiation to Watt per m²
Equate 1m² as 200Wp of PV panel (mono. or polycrystalline only...amorphous are larger) and cap it at panel efficiency x kWp PV.

Then compensate for panel efficiency ~14%
Angle of incidence losses (it's logarithmic and changes hourly that's a fun one..;) perpendicular to direct light= unity, horizontal mount = best case (of minor significance) for diffused light)
Solar panel temperature up-rating. (~1% per 2°C below 25°C)
Module shading.
Wiring losses < 3%
True measured battery bank capacity not plated. (depends on age, batch, use, temperature, load, charger fidelity, manufacturer and composition...always changing)
Battery charge inefficiency ~15% < 25%
Battery temperature de-rating. (~1% per °C below 25°C ambient)
Battery discharge curve compensated capacity. (tech. explanation here, formula here , a more specific figure will be on the data sheet for most good batteries)
Inverter losses 5% - 10% (usually more than rated)
System constant loads Inverter/charger idle, metering idle, electromechanical trips switches, relay coils etc.
Consumer loads (usually less than rated).



Or just size it 50% DOD per week max. 7% - 10% DOD per day min.
ie. Size the batteries to the max/min runtime then the chargers to suit the batteries. Not batteries to suit the chargers.
If you want a year round working battery system you'll be needing another charging source for the Winter; wind, hydro, diesel/WVO, mains, some-at

Paper figures will be way off whatever you do. I'd take Quentin up on his offer to get the controller readout then just offset the met.ie radiance figures for Dubland (compensate derating for the age of his panels too...:pac:).

These will be mostly UK figures and grid tied.

Capt'n Midnight

Capt'n Midnight wrote: »

To size batteries you need the data of when the sun doesn't shine, so I'm surprised that I haven't found it easily.

Most people work around it, turn off the unnecessary loads.
Run the big things when the sun is shining/generator is running.

Capt'n Midnight

Sir Liamalot wrote: »

Investing in lead Capt'n?

Global Solar Radiation in Joules/cm2 for Dublin_Airport ...

Paper figures will be way off whatever you do. I'd take Quentin up on his offer to get the controller readout then just offset the met.ie radiance figures for Dubland (compensate derating for the age of his panels too...:pac:).

Thanks, yes the problem with the met.ie data is that it only shows direct sunshine and doesn't indicate diffuse light.

I'll have to check the data again but for Casement the longest run with 0 measured hours was several weeks and I know it wasn't that dark. Might be a recording thing so maybe I'll sum up several stations to see.

As far as I understand it solar irradiation isn't measuring sunshine. It's calculated by a pyranometer monitoring flux density..

Forgot to mention all the power your charge controller is dumping when your batteries are near full. :rolleyes:

Although it can be used if you set up your PV charge controller as you would a wind turbine...with diversion control instead of charge control.
Charging batteries takes time + electrons.