Free electric on saturdays with smartmeters

[whisky-dave]

I assume british gase prices for the reast of the week will increase in order to pay for the 'free' eleccy, but an a pessimist or a realsist.

[Jim K]

certainly no typisht

Jim K

[Andrew May]

So large bank of lead-acid batteries to charge up on Saturday and use during the week. Or feed back into the grid and claim the FIT if you have solar panels.

[Caecilius]

I wondered that, but a quick calculation seems to indicate that a car battery holds less that 1KWh, which is worth what - about 12p or something?

Here's how I calculated it, in case someone can spot a glaring mistake and show I'm off by a couple of orders of magnitude:

A car battery is something like 40 amp-hours. That's 40 x 12 x 3600 joules, which is around 2MJ. 1KWh is 3.6MJ (1000 x 3600).

If the electrical contents of a car battery are only worth around 10p, I can't imagine you'd make a profit before the battery dies. You'd need something like 500 charge/discharge cycles.

Is there anything with a better energy density at a reasonable cost I wonder?

[Tim Watts]

On Thursday 01 August 2013 14:17 Caecilius wrote in uk.d-i-y:

40 Ah = 12 x 40 Wh = 0.48kWh, so about 6p before charger/inverter inefficiencies are factored in.

It could work if you and access to an endless supply of milk float batteries, but not if buying new.

Big-assed flywheel? Electrolysing water to H2 + O2 and back through a fuel cell?

[Steve Firth]

Err you do realise that there's no need to convert to Joules, don't you?

3600 on both sides cancels out.

Hence 40x12 = 480 Wh or approx 0.5 kWh

Except it won't because discharging the battery to less than 50% capacity will severely shorten its life.

[Andrew May]

Who cares about charger/inverter inefficiencies? Hey, the electricity is free - if you do it on Saturdays.

[Adrian]

That's a very small car battery - the battery in a 2cv's 40Ah...

Especially given that you want to deep-discharge, you're really looking at a leisure battery as in a motorhome. They're easily findable up to a bit north of 200Ah. Work on about 70p/Ah, and you won't be far wrong.

For example...

£150 for 1x220 or 2x110, delivered.

But I gather the cheapest deep-cycle £/Ah is to be found with used fork- lift or golf-cart batteries.

[Andy Burns]

We could hope they pay zero rate for saturday FITs too.

[Bob Eager]

Am I missing something, or what's wrong with:

40Ah x 12 volts = 480Wh? (= 0.48 kWh)

[Adrian]

Charging a 12v battery would normally be done at 14.5v.

[Tim Watts]

On Thursday 01 August 2013 14:33 Andrew May wrote in uk.d-i-y:

Well, you do care as the storage is not free :0

[dennis]

ITYM a thermal store and a swimming pool. That would be legal too.

[The Natural Philosopher]

why go to that bother? 40Ah and 12v is 480 Wh.

[Bob Eager]

I thought we were looking at what we could get out. Losses are another matter.

[harryagain]

It's called an electric car. NOT reasonable cost but otherwise useful. But even there the battery is only in the16-20Kwh range.

You battery calculation is wrong.

40x12 = 480wh = 0.48Kwh That's when it's new and you would need a deep discharge battery.

Such devices can be bought to use in conjunction with solar PV panels BTW. But not cheap.

Get yourself some PV panels and have free electricity every day.

The BG thing is just a gimmick. It has the potential for some massive fiddles, they willsoon with draw it.

Eg run a power cable froma house to a workshop next door.

[harryagain]

True but this won't last two minutes, they will soon withdraw it.

[David.WE.Roberts]

saturdays-75893

If your house is built on a concrete raft, than jack it up on hydraulic jacks then use the potential energy to drive a turbine on the output side of the jacks.

You would need flexible connections for your services, of course.

Cheers

Dave R

[SteveW]

Large thermal mass and a load of electric heating?

SteveW

[The Other Mike]

Thought for a moment to change suppliers and start building a pumped storage system but then decided that as the water is unmetered I may as well power a mini turbine direct from the outside tap.

21.65p/kWh + 4.64p/kWh export FIT payments