Solar power for shed

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Solar power for shed

Postby colint50 » Sat Jan 14, 2017 10:52 am

Hi all, I am hoping that I can get some guidance and suggestions from those that are more knowledgable on solar than myself. A retired neighbour is wanting to install a small system into his shed. He has a small workshop where he tends to use rechargeable tools and then a large space that his grandchildren use occasionally for weekend stayovers, on a rural property in the Hunter Valley.

He has already purchased 4 x 190w solar panels - specs CEEG model SST SE 190-72M, Pmax 190w, 5.08 Amps, Open cct volts 44.48v, SL open cut current 5.42A
He would require a MPPT, inverter and batteries plus the option of utilising a generator for charging batteries if required in overcast weather periods.

Expected power usage:
1. Small workshop use of rechargeable tools and the occasional use of say an electric saw where a bit of extra grunt is needed
2. General lighting (led's) probably around 6-7 lights -should these be 12v or 240v?
3. Occassion also use of shed by grandkids (late teens or so) - most of the lights would be utilised, say 6 hours overnight, also they have portable car fridges such as Engel, Walcott, etc around 40-60 litres. I haven't been able to find much detail on something like this, however I would expect that they may draw around 2A each, and there could be up to 3 of these units in use.
Maybe it may be beneficial for the neighbour to just buy a bar fridge?

My thinking was to go with 12v lighting, MPPT 20A unit, inverter 1500w, batteries say 4 x 120ah, given that panels total 760W.

I would gratefully appreciate any advice and suggested equipment......thanks in advance
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Re: Solar power for shed

Postby davidg » Sat Jan 14, 2017 8:56 pm

colint50 wrote:He has already purchased 4 x 190w solar panels - specs CEEG model SST SE 190-72M, Pmax 190w, 5.08 Amps, Open cct volts 44.48v, SL open cut current 5.42A
He would require a MPPT, inverter and batteries plus the option of utilising a generator for charging batteries if required in overcast weather periods.

If going 12V then you need to understand that the panels will be 4 in parallel, so will require fusing for each panel preferably in both the positive and the negative leads. Rating MAX 12A the fuses are there so that should a single panel develop an issue (short circuit for instance) and start accepting current rather providing it then the fuse/s will "blow" rather than the panel having a total meltdown (fire).

colint50 wrote:My thinking was to go with 12v lighting, MPPT 20A unit, inverter 1500w, batteries say 4 x 120ah, given that panels total 760W.

A true MPPT charge controller will need to be 60A for 12V with 760Watts of panels and if the panels are set-up properly, under various circumstances it will be able to produce this sort of current. Proper MPPT charge controllers that handle this sort of current are in excess of $300.00 at the very least, elcheapos while they may say they are MPPT they most certainly are not.

A decent inverter preferably a pure sine wave LF (Low Frequency) inverter are by far the best option. Check the efficiency of the unit.

N.B. Pass though or Bypass efficiency or similar is a rubbish spec %, ignore it as the inverter is not actually providing power in that mode, you want the actual inverter efficiency and not the eco mode either.
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Re: Solar power for shed

Postby colint50 » Tue Apr 18, 2017 9:48 pm

Thank you Davidg, and my sincere apologies for the delayed response...a few medical problems have got in the way of late unfortunately.....but up and ready to go again. Thankfully I have a patient neighbour....
I am grateful for your suggestions, however on further reflection, think that maybe it makes more sense to go 24v rather than 12v.
Is this more suitable?
Many thanks
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Re: Solar power for shed

Postby lantern » Thu Apr 20, 2017 8:16 am

Quite a few LED's are 12-33V these days so 24 is your best option. Also a lot cheaper on cable.
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Re: Solar power for shed

Postby jules » Thu Apr 20, 2017 2:00 pm

Hi colin 50,

if your neighbor hasn't already taken the plunge, he'd be best off creating a bank of batteries in series, not parallel. 12 batts X 2V or 4 batts X 6V for example. The series arrangement helps keep the batteries more or less equal whereas batteries in parallel can form backwaters, to use a water analogy.

Plenty of excellent 24V LEDs available and they use very little power.

24V is a good idea.

The fridges and the teenagers are the unpredictable factors :D . You're right to say one of those fridges will use about 2 amp though of course the power consumption over winter will be considerably less than that over summer. The proposed system is quite similar to what I use to power my house [see below]. Overall the power- in power- out should balance reasonably well though there could be problems if there were a few grey days, lots of teenagers and several fridges.

Could the fridges be charged at the main house?

Maybe a slightly bigger battery bank would be wise. It's fairly easy to increase the number of panels later [provided the regulator has the spare capacity] but it can be tricky to increase battery storage without changing the whole bank
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