Storing Domestically Generated Solar Power

[anonguest]

Contributing to the neighbouring thread on Electric Cars here jogged my memory on addressing/investigating means for storing modest amounts of electricity generated by solar panels (or even wind turbines) - either to make up shortfalls in live streaming supply (when appliance use demands exceeds the supply from installed panels) or to provide full supply outside of daylight hours.

Obviously some sort of 'battery' arrangement. The addition of a means to actually store ones own self generated juice will obvioulsy add to the overall cost of any such private/residential solar power setup. Question is what is best and most cost and space effective techology to use?

Loads of solar power related webistes selling panels, etc. but info on actual storage of the energy generated is thin on the ground (most sites I have seen instead talk about feed-in to the grid, etc). I am interested in a setup that, whilst still technically connected to (or readily connectable to!) the national gird can in the first instance make use of its own previously generated power before having to resort to the grid.

By way of example, I am envisaging a scenario of using daytime generated power to be used to power a collection of low power domestic appliances outside of daylight hours. An example scenario could be LED TV for 2 hours in evening, laptop computer for hour or so, other high power consumption devices for short bursts (e.g electric kettle). The power stored might even be several days worth before being called upon.

I'm also looking for commercially available solutions rather than DIY projects if I can help it. Also, the setup is not necessarily intended as a means of reducing ordinary existing electricity bills as its primary goal (though it is assumed that, over time, some savings will be seen in any case?)

Anyone got any experience/ideas/suggestions/pointers in any direction?

[Riedquat]

I've seen someone with a pile of car batteries in a shed (connected to wind power but the principle is the same). Probably not the best method though; this was somewhere without a mains electricity supply.

[fluffy666]

Been thinking along similar lines.

If you could adapt a UPS for a standard PC so that it charged in the day and drove appliances at night you might be there. Put it in the lighting circuit for the house, use CFC's or LEDs for lights and your lighting would be 'free'.

(Note: I am not an electrician. Don't complain if my advice leaves you dead)

I wouldn't go for high-power devices (Ovens, Kettles, Heaters, Microwaves, that sort of thing - that's a lot harder and more expensive.

[onlyme2]

Ther is only one long term sensible storage point - your electric car.

You use it both for transport and for storage, only then having to invest on one battery pack, the size is about right as well too. Whether manufacturers will want you to do this or providethe necessary electronics / connectors to do this is another thing.

Your best bet in the interim - small battery bank and small grid tied inverter (for ease of fitting maybe one or two of those microinverters and basically create the necessary DC panel voltage required directly fromthe battery bank). You;d need a controller than could monitor when to switch on the battery bank charger, monitor the battery state and then monitor when to turn on the backup inverters based on time of day once no more solar power being generated. The savings would be pretty low scale though so any new batteries and equipment would likely eat up any potenital savings.

[anonguest]

Been thinking along similar lines.

If you could adapt a UPS for a standard PC so that it charged in the day and drove appliances at night you might be there. Put it in the lighting circuit for the house, use CFC's or LEDs for lights and your lighting would be 'free'.

(Note: I am not an electrician. Don't complain if my advice leaves you dead)

I wouldn't go for high-power devices (Ovens, Kettles, Heaters, Microwaves, that sort of thing - that's a lot harder and more expensive.

Lighting and relatively low power TV and other such appliances are the bulk of the envisaged use. The inability to use the stored supply at all for higher power consumption devices (e.g a kettle or microwave for 2 minutes or so) would be s shame of course.

I'm guessing that if insisting on having this occasional higher power drain ability (albeit for short 'bursts') will affect the choice ofsetup and technogy used?

[onlyme2]

Been thinking along similar lines.

If you could adapt a UPS for a standard PC so that it charged in the day and drove appliances at night you might be there. Put it in the lighting circuit for the house, use CFC's or LEDs for lights and your lighting would be 'free'.

(Note: I am not an electrician. Don't complain if my advice leaves you dead)

I wouldn't go for high-power devices (Ovens, Kettles, Heaters, Microwaves, that sort of thing - that's a lot harder and more expensive.

Problem is those devices only maintain a separate circuit when power lost - some you may be able to change configuration and trigger when you want but they won't backfeed power to your normal mains circtui - which is what you really want to do. Grid tied inverters will do this - the trick is to only feed them the power when i) you have the power spare and ii) when you are not generating any and want to use your stored energy.

[anonguest]

Ther is only one long term sensible storage point - your electric car.

You use it both for transport and for storage, only then having to invest on one battery pack, the size is about right as well too. Whether manufacturers will want you to do this or providethe necessary electronics / connectors to do this is another thing.

Your best bet in the interim - small battery bank and small grid tied inverter (for ease of fitting maybe one or two of those microinverters and basically create the necessary DC panel voltage required directly fromthe battery bank). You;d need a controller than could monitor when to switch on the battery bank charger, monitor the battery state and then monitor when to turn on the backup inverters based on time of day once no more solar power being generated. The savings would be pretty low scale though so any new batteries and equipment would likely eat up any potenital savings.

Which, as intimated, is why the recent neighbouring thread jogged my mind on this.

I am assuming that the most desirable battery technology to make use of for this sort of setup up is Li-ion and not banks and banks of lead acid batteries?

Once again....anyone know of any commercially available 'solutions' to this question?

[SarahBell]

You need a caravan?

[onlyme2]

Which, as intimated, is why the recent neighbouring thread jogged my mind on this.

I am assuming that the most desirable battery technology to make use of for this sort of setup up is Li-ion and not banks and banks of lead acid batteries?

Once again....anyone know of any commercially available 'solutions' to this question?

Li-Ion is better, but any failure in charging and discharging and you have lost the pack - that is probably a risk not worth taking. As yet not heard of anything car related - so could not recommend that route yet.

Deep cycle discharge Advanced Glass Mat lead acid probably the safest option, you may get a pack from something like a forklift battery pack. Not sure of any off the shelf solution.

[corevalue]

I have a stack of sealed lead acid batteries at home - 4 x 100 Ah12V - ex-telecomm, set up as a 48V bank as it lowers the current draw to the inverter. These are charged by a 4 x 175 Watt array, the regulation being done by a home-made device. You can now buy these regulators very easily (not at the time I installed my system). This powers a converted UPS, as the inverters in these are pure-sine wave. The only mod was to connect the battery in place of the battery pack (and add a fuse). You can now also buy the inverters much more cheaply.

One essential is to make sure all your appliances, especially vacuum cleaners and power tools are soft-start, otherwise the surge will trip your inverter (or blow it up!).

The system was set up as a prototype for the similar system I have installed on a boat. It provides all the power we need for cooking, drinks, fridge, power tools etc. on the boat.

If you are interested, PM me for more detail.

[thecrashingisles]

Use solar powered grass to feed a flock of sheep. Then feed the sheep to a family member and install a bike that they can use to convert the excess calories back to electricity.

[inactionman]

Would suggest flywheel energy storage, you can get them as a part of a UPS (similar to batteries) but price is a problem!

[SarahBell]

Use solar powered grass to feed a flock of sheep. Then feed the sheep to a family member and install a bike that they can use to convert the excess calories back to electricity.

Nah use the solar energy to pump water into a tank a mile in the sky. Then let it out when the sun goes in and run in through a turbine.

[anonguest]

You need a caravan?

A caravan? How will that help?

[anonguest]

I have a stack of sealed lead acid batteries at home - 4 x 100 Ah12V - ex-telecomm, set up as a 48V bank as it lowers the current draw to the inverter. These are charged by a 4 x 175 Watt array, the regulation being done by a home-made device. You can now buy these regulators very easily (not at the time I installed my system). This powers a converted UPS, as the inverters in these are pure-sine wave. The only mod was to connect the battery in place of the battery pack (and add a fuse). You can now also buy the inverters much more cheaply.

One essential is to make sure all your appliances, especially vacuum cleaners and power tools are soft-start, otherwise the surge will trip your inverter (or blow it up!).

The system was set up as a prototype for the similar system I have installed on a boat. It provides all the power we need for cooking, drinks, fridge, power tools etc. on the boat.

If you are interested, PM me for more detail.

I thinnnnnk I 'get' the technicals here. Sounds interesting. I may well take up your offer and be in touch (after I mull over what exactly I have in mind first). Thanks.

[anonguest]

Would suggest flywheel energy storage, you can get them as a part of a UPS (similar to batteries) but price is a problem!

Fascinating! But I suspect that the total power that could be stored (for each unit at least) isn't going to be that great??

[Gigantic Purple Slug]

Use solar powered grass to feed a flock of sheep. Then feed the sheep to a family member and install a bike that they can use to convert the excess calories back to electricity.

Your incredibly irritating cat avatar has stopped moving. May the gods be praised.

[Rave]

Deep cycle glass mat batteries are your only sensible option at this point in time. Something like:

http://www.ebay.co.uk/itm/Off-Grid-Solar-Power-Kit-Alone-System-With-Battery-Storage-4-5-KW-9-6-KWh-/221379273303?pt=UK_Gadgets&hash=item338b3ba257

would presumably do? TBH though with the feed in tariffs still available I'd be far more inclined to just install the panels and use grid power at night, unless you're prone to power cuts? From a green perspective it makes sense to feed the existing grid infrastructure during the day and use the plentiful power available at night from the nuclear fleet (and, increasingly, wind, I would guess).

[onlyme2]

Deep cycle glass mat batteries are your only sensible option at this point in time. Something like:

http://www.ebay.co.uk/itm/Off-Grid-Solar-Power-Kit-Alone-System-With-Battery-Storage-4-5-KW-9-6-KWh-/221379273303?pt=UK_Gadgets&hash=item338b3ba257

would presumably do? TBH though with the feed in tariffs still available I'd be far more inclined to just install the panels and use grid power at night, unless you're prone to power cuts? From a green perspective it makes sense to feed the existing grid infrastructure during the day and use the plentiful power available at night from the nuclear fleet (and, increasingly, wind, I would guess).

Yes, but price still far too high and I think off-grid is fine if you have no other supply but too much of a compromise solution if you are grid connected - you are looking at complete switching between grid and local supply or running a separate off grid low power link, both of which not optimal solutions. Hence why suggesting a grid tied system, but even then I am, like you, dubious of the economics and think it not worthwhile unless you can get a deal (primarily on the batteries) to make it worthwhile. Also unless you have the skills to design and build yourself the all up cost is increased considerably.

[Jason]

How about compressing air as a energy storage device?

I've always thought the electricity produced from solar energy in the day, could go directly to heating your super insulated house so little additional heating is required in winter.

[onlyme2]

How about compressing air as a energy storage device?

I've always thought the electricity produced from solar energy in the day, could go directly to heating your super insulated house so little additional heating is required in winter.

Compressed air - no, not practical.

Dumping excess PV into hot water tank via additional water heater is quite common though.

[happy_renting]

Sell the surplus electricity by dumping it on the national grid.

That way the electricity companies store it for you, by keeping oil and coal underground instead of burning it.

A little trite, perhaps, but i suspect it compares well with the cost of a shed full of batteries when you do not enjoy the economies of scale.

It all depends on why you are generating excess electricity, and what you intend to ultimately use it for.

[justthisbloke]

I store my 'leccy in a car. No mechanism to get it out again - which is a shame as it would be nice to have an in extremis tappable 24kwhrs.

My brother dumps his excess sun in his hot water tank via an immersion heater.

From my limited research, none of the routes to off-grid storage are cheap. They only make sense if you actually are off-grid. Or are a rich prepper who'll just do it to be the best prepper in town.

[whitevanman]

Deep cycle glass mat batteries are your only sensible option at this point in time. Something like:

http://www.ebay.co.uk/itm/Off-Grid-Solar-Power-Kit-Alone-System-With-Battery-Storage-4-5-KW-9-6-KWh-/221379273303?pt=UK_Gadgets&hash=item338b3ba257

would presumably do? TBH though with the feed in tariffs still available I'd be far more inclined to just install the panels and use grid power at night, unless you're prone to power cuts? From a green perspective it makes sense to feed the existing grid infrastructure during the day and use the plentiful power available at night from the nuclear fleet (and, increasingly, wind, I would guess).

£6k ?!

I've got a system for my shed with a couple of deep cycle batteries, a charge controller, some salvaged solar panels and a cheap 1kw inverter (not pure sine wave). It'll run loads of power tools, chargers, lights and a hoover.

It owes me a few quid for the controller but the rest was free to me. I reckon you could do a home supply for very little as long as you don't demand heat. Batteries don't need to be fancy. The more basic the better. Flooded lead acid batteries are cheap and easily maintained. Don't worry about weight or space, you just need cheap capacity. I wonder what they do with the batteries from the hunter-killer submarines they decommission?

[StainlessSteelCat]

If you want a polished grid replacement with batteries, it'll cost a fortune and is probably not worth the saving. Get a certified array and the feed-in tariff etc might well pay for the rest of the electricity bill.

We use an immersun to dump excess power into the hot water immersion heater. That works pretty well for 8-10 months of the year.

I am very interested in a cheap and cheerful off grid storage system as I have a south facing porch roof doing nowt - and the grid probably goes down 4-5 days a year around here. It would be nice to have an emergency back up - and perhaps a supplement to the rest of the array during winter months for the hot water tank.

I have also been wondering about some form of seasonal heat storage as frankly even with the wood burner the house gets pretty cold during the winter.