Solar panel output figures.

[portvasgo]

Just a quick question on Solar panel ratings please.
I have a Solara semi-flexible solar panel on my boat, it came with the boat when I bought her.
The model is SM225M. On the leaflet it is rated at Wh/d (average summer time daily output) 225 and Wp (which I think stands for Watt peak) 56.

What I am not sure of is how these two figures relate to the figures formurites give when talking about solar panel output. For example in the current thread on solar panel regulators, contributors talk about 30w and 40w panels, how do these figures relate to the two figures quoted in the leaflet for my panel?

Thanks for the advice.

 

[alan]

Solar panel Output Figures

When most people talk about solar panel outputs they are quoting the Wp (peak value).
For the Solara panels this is 56 Watts at (IIRC) 19 volts, so about 3 amps. You will find that the manufacture usually quotes a short circuit current which is higher than this (for Solara panels I think they quote 4 amps or so).
The "mistake" that most people make is to buy a 60W panel and think that they will get 60/12 = 5 amps!!!! What you will actually get is 60 divided by the open circuit volts for that panel.
The other value that is quoted by Solara (225 Wh/day) is the amount of power (watts) that you can accumulate on a summers day for a given number of hours of sunlight ........... I think on their web site somewhere they explain just how they calculate this.


Alan.

 

[VicS]

Yes the average daily energy output is 225 watt hours
and the peak instantaneous output is 56 watts.

But I think you will find that the peak output will be at around 15, 16 or 17 volts. The makers bumph should state it.

19 volts is more like the open circuit volts.

some of the manufacturers websites are good with the detail, others are not!

 

[Boo2]

The model is SM225M. On the leaflet it is rated at Wh/d (average summer time daily output) 225 and Wp (which I think stands for Watt peak) 56.

What I am not sure of is how these two figures relate to the figures formurites give when talking about solar panel output. For example in the current thread on solar panel regulators, contributors talk about 30w and 40w panels, how do these figures relate to the two figures quoted in the leaflet for my panel?

Aiui, the peak wattage is the maximum the panel can give out under the most favourable circumstances of sunlight and angle of inclination etc. In normal use the output is around 20% of this, or thereabouts.

I expect the 56W quoted is the peak power output for your chosen panel and would correspond to the 30W / 40W you've seen quoted on the forums. The astdo figure will be the total number of watt-hours for a typical summers day (presumeably a UK summer ?). To obtain the figure for the "average peak" over that entire day, you need to know how many hours of sunshine they allow for and divide by that.

Eg, if they recon on 10 hours of useable sunshine in a summers day then the average power from the panel would be 225/10 == 22.5W. The fact that this is around half the "maximum" peak power instead of 20% tells you they are optimists in respect of their expectations of a UK summers day

Hth,

Boo2