The Accidental Smallholder Forum

Smallholding => Renewables => Topic started by: bazzais on December 17, 2012, 06:40:28 pm

Title: Solar power redundant power harvesting and storage.
Post by: bazzais on December 17, 2012, 06:40:28 pm
Hi all

my electric supplier has just refitted me with a smart meter which means on sunny days my meter does not go backwards like the old meter.  Its a bit of a bummer and means that I have to use the excess electric produced by my panels as they produce it in the daytime - useless as most my electric gets used for lighting at night.

I have two meters here on the farm and was wondering if there was anyway to tap my home supply with the panels into my yard supply to help use that extra power that is produced before it gets fed back to the grid in the day.  Or better still some kind of backup power battery that can use the excess electric I produce in the daytime to use at nights when the panels are not working.

Yes I know I am getting paid for the feed in tariff - but as long as I dont mess with the meter or anything up from that point its my responsibility and my property and electric to do what I want with - and so I want to use it and save it for my own purposes.

I was wondering if you could simply join the electric rings together with a 3 point pin on either end of a cable?

Maybe use the excess power produced in the daytime to charge storage batteries?

Ta

Barry


Title: Re: Solar power redundant power harvesting and storage.
Post by: chrismahon on December 18, 2012, 06:48:52 pm
Store it by charging batteries and release it via an inverter to an independent circuit, because the inverted supply will be out of phase with the mains. Inverter meltdown! Lot of hassle because of the cost of the kit and the aging on the batteries.
Title: Re: Solar power redundant power harvesting and storage.
Post by: oigoi on December 18, 2012, 11:01:41 pm
HI Barry you can not simply join the house ac to the yard ac because they will be out of phase with each other. There are pieces of equipment that could match the phases together but it's not something I've done.

If I was in your situation and I had equipment on the yard power circuit that could use the power the house's solar is making I would install a changeover switch that disconnects the yard from its mains supply and connects it to your house's solar system.

The downside of storing the excess solar energy in batteries is that you would lost about 25% of it through the inefficiencies of battery charging and then inverting that dc power to ac again.

Another possibility is to use the excess electricity in your house to heat water - nice hot bath for free every night!
Title: Re: Solar power redundant power harvesting and storage.
Post by: bazzais on December 19, 2012, 02:27:39 am
Batteries might be an option as all the electric I produce just goes back to the grid - on my lines probably gets burned away before it reaches anyone else. Loosing 25% is gaining 75%.

Even if its a simple as getting a few marine dry cells and charging batteries for lighting on the campsite and on the yard at nights.

Could put a timer on the 12v chargers or a light sensor on the charging side.

Mmmm
Title: Re: Solar power redundant power harvesting and storage.
Post by: deepinthewoods on December 19, 2012, 07:32:15 am
a wild suggestion here, could you invest in an electric car or quad. that would be useful asset.
Title: Re: Solar power redundant power harvesting and storage.
Post by: bazzais on December 19, 2012, 05:46:41 pm
I think it could be a gimmick I could use on the website to advertise to the 'greeners' to come and camp - but an electric car?  Wouldnt even get up the driveway!?
Title: Re: Solar power redundant power harvesting and storage.
Post by: Plantoid on December 22, 2012, 12:35:32 am
I was always under the impression that it is highly dangerous to use stored power via an inverter fed into your domestic or farm wiring  because if there is a powercut and there are engineers working on what they think is a dead wire you can end up electrocuting them from your power source .
 Is it not now illegal for anyone to play with electrics anywhere with in the EEC unless they are a fully qualified & certified electrician nowadays & if  discovered doing so will suffer severe consequences   that may also include up to seven years in jail?
 
Title: Re: Solar power redundant power harvesting and storage.
Post by: Small Farmer on December 22, 2012, 02:43:26 pm
The PV inverter contains a cut-out to prevent feeding the grid when it's dead.  When using either stored energy or a generator you need a manual switch for the same reason.


There are several people on eBay flogging devices which will recognise when the PV generation exceeds the amount being consumed.   On a brilliant sunny day a 3kw immersion heater load makes sense: but we don't get too many of those. One suggestion is to feed the immersion through a 110v transformer: the load is the reduced to around 750 watts I'm told.


I didn't bother doing anything, no yet anyway, because I could see the cost exceeding the benefits.
Title: Re: Solar power redundant power harvesting and storage.
Post by: Aardvarker on December 22, 2012, 08:08:26 pm
IFF you lived further north, you might consider a mini pump storage system?
Title: Re: Solar power redundant power harvesting and storage.
Post by: Polished Arrow on December 22, 2012, 11:34:03 pm
We have been facing the same conundrum as the OP.  Near here, in one of the local Transition groups, there is one couple with more money than most of the other members.  Fair play to them, they have been willing to invest and test and feedback and share, and one of the things they are currently looking at is battery storage of excess power.  They (and we) have both a wood burning boiler doing heat and hot water and solar panels for 'lecky', so are interested in ways of using the excess power we get many days.


So far, the best way to save the power is indeed as hot water.  There is a simple and not toooo expensive device called the ImmerSUN which helps you do exactly that.  A neighbour is testing it out and when he's got 6 months' feedback, we'll consider whether to invest in one or not.  I am happy to share the feedback here.


ImmerSUN Linky (http://www.immersun.co.uk/)
Title: Re: Solar power redundant power harvesting and storage.
Post by: bazzais on December 23, 2012, 02:47:20 pm
I dont use much hot water  :innocent: takes so long to come through the pipes there is no point using it for handwashing - and as for showers - its not my birthday all the time.

Its frutating with hot water - you can put the washing machine on in the day to use electric - but the drum size is smaller than the amount of water inbetween the boiler and the washer  - so unless you run the hot tap and waste water for 3 minutes you dont get any hot water through anyway.

Some people might say that using and storing the energy is some home job and is a bit parasitic as you cant compete with the big boys for the cost of storing and reclaiming evergy.  But locally storing energy is the key. 

I was so disappointed that after they installed my panels and I stated 'at least I can use electric when the electric fails'  they said ' no you need a supply to produce your electric'  kinda defeats the point.
Title: Re: Solar power redundant power harvesting and storage.
Post by: bazzais on December 23, 2012, 02:49:28 pm
Surely it would have been better for government grants to cover the storage of electric within homes to power the grid in a fall down?


Will have a look on ebay for some chinese bodge but if its anything like the chrimbo tree lights and the outside lighting i bought - it will be dead with no refund in a week.
Title: Re: Solar power redundant power harvesting and storage.
Post by: mab on December 23, 2012, 05:44:38 pm
I don't have a grid connected solar system, but a small battery based system. As stated by Oigoi, a lead acid battery is about 80% efficient and you'll probably lose another 10% if using it via an inverter.

One way of storing excess solar is to 'charge up' the freezer with the 'deepfreeze' button (overrides the thermostat). I've lined the inside of the chest freezer with storage heater bricks, and if I get it down to -24C it'll stay cold enough without power 'til the next days sun - even at this time of year.

in a similar vein, you can make ice packs during the day to use in the fridge rather than using grid power to keep it cold at night.


I've installed a couple of immersuns for customers and they seem very happy with them (can of course also be used with storage heaters up to 3kw).


if you want to go down the battery-inverter route properly, then you'd need a decent battery  (ideally a traction type battery (forklift battery usually works out cheapest)) and a decent inverter (not an ebay chinese job) so you're talking serious money.

if you want to start small you could look out for a 2nd hand UPS (uninterruptible power supply) like this:-

http://www.ebay.co.uk/itm/APC-1400-UPS-with-faulty-batteries-in-cream-/230900355821?pt=UK_Computing_Uninterruptible_Power_Supplies&hash=item35c2bbd2ed (http://www.ebay.co.uk/itm/APC-1400-UPS-with-faulty-batteries-in-cream-/230900355821?pt=UK_Computing_Uninterruptible_Power_Supplies&hash=item35c2bbd2ed)

which is an inverter, battery and charger all in one. connect it to a bigger battery (the built in one is only ~17Ah), but bear in mind that it will only run ~500w continuous and with a limit of 1400va it will only start small fridges and freezers (which typically draw 5-7 times their rated current at startup).

Quote
Surely it would have been better for government grants to cover the storage of electric within homes to power the grid in a fall down?

Mmm.. well there isn't really a turnkey small scale energy storage solution unless, maybe, if you use lithium batteries and that would cost , and it would still have only 70% efficiency.
Title: Re: Solar power redundant power harvesting and storage.
Post by: bazzais on December 26, 2012, 07:00:44 pm
Thats a great idea about the freezers - in summer I could get two to rotate and campers could hire out freezerpacks for their sandwiches :)
Title: Re: Solar power redundant power harvesting and storage.
Post by: Small Farmer on December 27, 2012, 09:35:18 am
So far, the best way to save the power is indeed as hot water.  There is a simple and not toooo expensive device called the ImmerSUN which helps you do exactly that.  A neighbour is testing it out and when he's got 6 months' feedback, we'll consider whether to invest in one or not.  I am happy to share the feedback here.
ImmerSUN Linky (http://www.immersun.co.uk/)
I looked this up and it's about 500 installed so about 4200 units of leccy at 12p. We generated 3300 units in 2012 but I've no idea what proportion we used ourselves.  I guess that's the analysis that needs doing. We have one of those radio meters in the kitchen but it reads wrong when there's any PV generated.
Title: Re: Solar power redundant power harvesting and storage.
Post by: HenLivingstone on June 06, 2013, 03:01:55 pm
There is now a commercially produced standard package solution to domestic PV storage
http://www.solar-enles.co.uk/SunBat.html (http://www.solar-enles.co.uk/SunBat.html)
It's pricey though!