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Piggyphile

Solar without Batteries?

Having looked at Otley Lads solar thread I have a numpty question. I know very little about electrics so don't shout at me.

Is it possible to run a solar PV panel and use the power directly without the use of batteries? Could I for example run and use my laptop or a well insulated fridge during daylight hours? I am well aware of the issues of batteries, the expense and non environmental friendliness of them.

Would a panel just sit there and be available when I switched stuff on assuming there was decent light?
Thanks
vegplot

You could. You'd be at the mercy of when the sun is shining and it's intensity but it is possible for some devices.

However, many electrical items have very high starting currents, freezers for example, that require high starting currents which the PV array will probably not be able to support.
OtleyLad

As vegplot said, you can use the power without batteries as long as the load matches the output.

One way to get around the on-off supply problem is to use a relay to switch between mains and your solar supply (assuming your solar supply is inverted to 240v). The relay is controlled by a light sensor - when light is low it connects the mains, when its bright, the solar is connected.
Both the relay and light sensor are cheap (under 10).

I can send you the wiring diagram if you wish.
Piggyphile

Thanks but I will save for a panel or two first, it is on my to do list along with a few other things. It is good to know that it is possible though.

Trying to seriously downsize here and minimize my dependency on electricity for when the zombie hoards attack.
mark

Hmm pretty certain in Galicia with it rainfall clouds solar power without a storage system (batteries?) is likely to pretty unsatisfactory.

You can probably use solar for direct heating of hot water in summer - but I would not rely on it for any use where you convert it to electricity in autumn winter or spring without good storage . There are other systems but batteries are the cheapest and simplest.

Relay switching with mains can work but beware of simple cheap systems if you are using it for computing or refrigeration where switching spikes can cause problems.

PS refrigeration with solar heat works best if you can keep fridge, freezer in a cool unheated place (cellar or outhouse). If it is in house and you heat house in evening when no sun then you need stored power to cool , fridge freezer. Insulation is great til you open the doorr to get anything out!
dpack

you might be surprised at how much energy a laptop uses even allowing for a direct feed at the input voltage it uses ,19v is quite common it would need a biggish panel and would not work at night .
daytime it can be done but it would be a bit fiddly and would need control gear to flatten out sunny/cloudy etc but does avoid the losses from the conversion from panel voltage to battery voltage to 240 to lappy input with a loss at every stage.
it will need a fair sized panel to power a lappy on any style of rig.

iirc tablets use a lot less power (as do some basic systems such as low power tower /cathode ray screen)

if i wanted to power a pooter i would go for bigger panels/battery bank and either inverter/lappy transformer or direct from the batteries using control gear (or a car charger if one is available for that pooter) to give it the proper smoothed input voltage.

i hope that isnt too technical ,it is based on doing it .

the basic things are lappys are greedy,that you will need bigger panels than you think you do ,batteries are a good idea (and if a panel says it produces x amount of energy it is a fair guess that in reality it will produce less).

if you have moving water it is potentially a much better power supply than sunshine/cloud glow or perhaps consider a biomass based heat and power alternative.

ps sunshine is rather good at warming water even if it isnt really best for electricity
Piggyphile

Thanks all, lots to think about there. Solar hot water with a wood burner for top up in winter is our intention.
dpack

i was chatting to a bloke on the east coast of north yorkshire and the solar water warmer they used gave bath temp and lots of hot water in summer and about a 20 degree advantage in pre heating for winter for bath or ch system

iirc they had some clever heat exchanger stuff and tank kit to direct the heat to the required purpose.it wasnt very expensive and would pay for itself in a few years
vegplot

Thanks all, lots to think about there. Solar hot water with a wood burner for top up in winter is our intention.


Good idea. You'll get excellent performance with solar thermal and short payback time.
alison

That is what we have.
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