A solar charging system for a big garage

[char1ie]

Hi,

I have been researching a solar charging system for a big garage where I would like to use lights, power tools and a dehumidifier. I am planning the following and would be interested in your opinions:

6 X Suntech 250W panels. Total 1500W. Output per day approx 4500WattHours

2 X Varta 230AH batteries. Total 460AH

Outback 12V 2000W pure sine wave inverter

Outback FM80 charge controller


The charge controller and inverter I hope are big spec enough that if I want to add batteries and panels in future I can.

The roof is 56sqm.

The cost will be around £3,600.

UK Power Networks quote to connect to the mains was £10,000!!!

Any thoughts and suggestions greatly appreciated.

Thanks all,


Charlie
Not an electrician btw

 

[amlu]

It will work, how well depends on how much power you will take out of it. cannot say much about sun in UK or how heavy is your power tool use. in the worst case you will need a wind turbine/couple more solar panels/small generator for backup.

Go for led lighting they take next to nothing of power.

give me a pm if you are in London and need some help wiring it up.

 

[char1ie]

give me a pm if you are in London and need some help wiring it up.

Thanks, I may do.

I have a backup generator. LED lights make sense, and yes, power tool use will be sporadic.

Any more comments?

Charlie

 

[Worcester]

If you go for an AC inverter for the solar panels and something like sunny backup (I know it adds some losses) despite not being grid connected you could be eligible for the Feed-In-Tarriff, additionally being a non heated / conditioned environment should get you the higher rate FiT, so although it adds to the capital costs, you would be better off long term.

Food for thought .. and some maths to do

 

[char1ie]

If you go for an AC inverter for the solar panels and something like sunny backup (I know it adds some losses) despite not being grid connected you could be eligible for the Feed-In-Tarriff, additionally being a non heated / conditioned environment should get you the higher rate FiT, so although it adds to the capital costs, you would be better off long term.

Food for thought .. and some maths to do

OK, did a little bit of research... The installation would be eligible for the feed in tarriff of 12.89p per kWH. Tarriffs here: Tariff Levels | FI Tariffs

Does this mean that for every kWH I use I get 12.89p? If I don't have a meter how do I know how much I use? Or how do I claim the payment? I don't think it would be worth it.

Charlie

 

[ExtremePV]

Couple of suggestions:

Follow Worcester's suggestion and use SunnyBoy inverter + SMA Sunny Island inverter/charger.
24V 2.2kw Sunny Island:
SMA Sunny Island Inverter 2.2kW 24V 0-80A charger SI-2224

Use this with either a SB1300 or SB1600TL.

You can get a feed in tariff.. simply get MCS installer to install the system with the Sunny Island acting as the grid. Put kwh meter in normal place and your good to go.
PLEASE use a 24V system or 48V system if you think you might need more power. 12V off grid is really very small systems and when onboard 12v vehicles/boats.

Outback are a great products, but European support isn't as good as it should be.
I can't comment on the batteries..but if you can work out how many kwh's of power you need per day/week it would be useful.

While you might not think its worth claiming the FITS payment..even a small payment will help pay for the system or replacement batteries.
Ken

 

[TedM]

Charlie, the correct rate is 15.44p - the row below the one you used.

You do need to work out what battery capacity you need. This is critical to a successful system. See this other thread - http://www.electriciansforums.net/p...een-energy-forum/72590-120hr-backup-800w.html

 

[Gavin A]

what is your winter usage per week going to be in kWh / amp hours - work this out, then size your battery bank and panels accordingly - my advice, drop the dehumidifier in winter as far as possible.

 

[char1ie]

Hi all,

I am reviving this thread because after a long cold and wet winter I am now more keen to get on the roof of the garage and get this system built.

A few comments: I like simplicity, so not keen on fitting a meter or claiming a feed in tariff - I can do this in future. I have three big garages, so once I have done this once I will build the same system again, and again, and if I acquire more garages I will build more of the same. I want to understand and build the system myself - I like learning, and it's cheaper, and when I make a mistake I can learn, and not make the same mistake again.

So the Sunny Boy 4000TL inverter:
SUNNY BOY 3000TL / 3600TL / 4000TL / 5000TL with Reactive Power Control.*SMA UK

This will take 24v from the batteries and output a maximum of 4000W or 22A at 230V. So in the garage, with a load of lights on, and firing up a big angle grinder, this is going to be at capacity? If I try to draw more than 4000W would the Inverter trip, or just not be able to supply the demand. Would the lights dim?

Would it be worth have two inverters? One small one hooked up to a battery to run the lighting circuit. One large one to run the double sockets in the workshop?

Has anybody on this forum built or come across an off grid charging system of this size? I would like to hear about the practicalities.


My calculations for use:
3 hours of the lights being on. 300W per hour X 3 hours = 900Wh
1 hour of power tools. 1500W per hour = 1500Wh
Total is 2400WH + extra capacity just in case = 3000Wh per day.
3000 / 24V = 125Ah
allow for max 50% discharge = 250Ah

So I need batteries to provide 250Ah total. Two Varta batteries at 230Ah each is 460Ah. So I think in terms of batteries I am about right.

More to follow...

 

[char1ie]

Further thinking this evening is getting me to a new plan to build two systems within the garage:
1. Lighting circuit using one or two panels, 12V battery, 12V lighting.

2. Socket ring using four or five panels with one inverter and two batteries. 230V

Any thoughts?

Charlie

 

[char1ie]

Hmm, big post with an update seems to have disappeared. I will resubmit it in the morning...

 

[Marvo]

Hmm, big post with an update seems to have disappeared. I will resubmit it in the morning...

Your big post got caught in the moderating queue possibly because it had an outbound web link in it. I've approved it now.

 

[solarfred]

How about getting a second hand (possibly unused) GT inverter cheap and connecting to the PV. The inverter is connected to a Victron Multiplus which will allow the inverter to work via batteries as a virtual grid. Then you can connect a generator to the Multiplus which will assist with heavy loads when the batts are too low ; in winter. The PV will supply AC more efficiently when required or divert to the batts. The genny only kicks in if required. This all happens automatically. Run heaviest voltage you can to use smaller cables and get less losses. Run AC LED tubes for lighting.
The multiplus can be daisy chained if you want to add more capacity later. You can’t add old batts to new batts though.
If you find second hand (unused) PV you can do it all quite cheaply if no MCS required.
If you need help with load calculations PM me.

 

[char1ie]

I will use second hand if I find it but first I need to design the system.

At the moment I am planning two systems in the garage:

1. 12V lighting, 12V battery, 1 250W solar panel

2. 230V sockets, 2 batteries, 1 inverter, 5 250W solar panels

I don't really want to use a generator as I want to spec the system big enough for what the garage will be used for. And if I find that a tenant is running out of power I can add more panels and/or more batteries.

Charlie

 

[solarfred]

You do not need a generator but it is an effective/efficient way of covering the peak loads. Otherwise you need a lot more PV and batteries. You have not allowed for any losses in the system. You have about 20% losses in the battery system and another 20% in the inverters.
You need a proper load calculator to include the losses. You need to know how much solar power you will have in winter (PVGIS). You need to have X days latency for when there is no light which will happen in winter. Run lights in 24v minimum if you insist on doing a separate system.
How will you fully charge the batteries in winter? You may need to use a mobile charger off a genny to keep them 100% or they will deteriorate as unlikely to get a full charge if you are running loads AND trying to charge batts. off PV alone.
Once you know the total loads and the total solar power you can see how much it needs to fill the gap between the two numbers.

It also just occurred to me you are renting so will have the added problem of tenants not abiding by the "off grid code". It is hard enough to have the discipline yourself to be frugal with the power but anyone paying for the garages (or not paying for that matter) will not be so frugal. They will leave things running/lights on/fill the kettle to the brim etc..... I would consider how you incorporate controls to mitigate this?