House batteries

[Night Train]

I've got my thesis hat on again.

What sort of batteries would one use in a building to most effectively store excess electricity?

I'm thinking about an 'intelligent building' storing electricity when there is some and using during power failures with the option of charging when electricity is cheap and in excess and selling when prices are high and demand peaks.

Unlike an EV there would be less contraints on size and weight I would have thought though one wouldn't want to be changing them too often due to cycle time either.

Thank you.

[qdos]

either lots of them basically one at each device or you'd need to install very big wires. Basically it's not practical

[JonSpence]

either lots of them basically one at each device or you'd need to install very big wires. Basically it's not practical

I beg to differ about its practicality. It's been done many times by many people. You don't start with the batteries though. You start by evaluating your needs and making energy savings everywhere that you can before you size your inverter and battery bank.

Examples of where it has been done are Internet servers, telephone exchanges etc. However some private individuals have done the same for their homes, usually where the mains power is unreliable.

The battery of choice depends upon what your expected use is. Valve regulated or AGM have the advantage of needing less maintenance, while flooded PbA is the battery of choice amongst those who generate their own electricity.

Homepower did an article on the subject back in 2001.
http://www.homepower.com/article/?file= ... 4_Schwartz
Sadly they now charge, it use to be free to download.

[Night Train]

Thanks Jon, yes, it is something that is done. The sort of installations I know of are usually houses in isolated places using renewable generation and a bank of ex submarine batteries.

I would be looking at the idea of evaluating the energy requirements of a development of passivehaus standard dwellings using stored electricity to cover some or all of their electricity requirements while being charged through intermittent generation, say, from a local wind turbine or CHP plant. Excess energy could be sold back to the grid and charging could be from the renewables or the grid as available. Energy trading meters would need to be used to make it financially viable while the stored capacity would make the intermittent renewable generation more attractive. It is the distributed storage that would be interesting in the same way as Car to Grid but with the larger capacity and permanent connection offered by a house. It would also be the sort of thing that could happen now rather then waiting for an abundance of EVs.

I will need to research the capacity and physical size and intallation requirements of those and also consider flywheel storage and maybe even the possiblility of pumped H2O storage in a tower block.

[Alternative]

I am interested in doing exactly what is being discussed. I have recently had a 4kWp solar PV grid tied system installed and get paid by Ecotricity 9p for every kWh generated. This is whether I use it myself or export it to the grid.

I charge my G-Wiz, when the sun is shining of course, but once it has charged and the washing is done, I generally have surplus power. I have dabbled with renewable energy for many years and have a small battery storage system with a medium sized inverter/charger which can feed the house electrical system when required.

My plan is to invest in a much larger battery bank, to store as much of my "free" energy as possible. I am tempted by the Crown deep cycle batteries as they seem very well constructed, but may opt for a bank of separate 2v cells as used in fork lift trucks. I don't mind the investment as long as they prove reliable.

Nigel

[Night Train]

Hello Nigel,

Sounds like you have an interesting situation there that is worth exploring.
How do you monitor your electricity useage? Do you aim to consume only when you are generating, where possible, or do you just consume when you want?
I assume that if you are able to store your surplus then you can choose to only consume your own generated electricity and not buy from the grid unless absolutely necessary.

[qdos]

Whilst I too am very keen to do something like this at home and I am aware of a number of folk who have home generated electricity has anyone got a system that powers anything much more than a portable telly and a car headlight ?

What cost has the generating and storage system come in at? About the only people who manage to get anything much like worthwhile electricity are those who live either at the top of a hill or on a flat plain where they can put up a very substantial wind generator usually on a farm far away from complaining neighbours. PVs in this country haven't been of much practical use so far as they have been prohibitively expensive and other than a few garden LEDs there's not a lot out there currently in the UK for PVs

[JonSpence]

Whilst I too am very keen to do something like this at home and I am aware of a number of folk who have home generated electricity has anyone got a system that powers anything much more than a portable telly and a car headlight ?

Many people have, though not I grant you many that live in the UK. I did read of a house in Wales that used "wild AC" generated by a micro-hydro system to provide background heat. If you study the subject you will know that heating is by FAR the greatest energy requirement of a home. There are also island communities and remote places that are not on mains electricity.

The issue is always one of space and cost effectiveness. It's NOT cheap at the moment, but then the same could be said of EV's.

The more power that you require, the more that you will spend to generate and store it. IF you are connected to the grid, then it's usually not economic to buy batteries and store the energy (or so I understand).

If a grid connection is not available or very expensive then the economics change. Strangely those in such situations still want to run a washing machine and often a fridge. Naturally they would rather use low energy light bulbs and ultra insulated fridges than install extra capacity. But isn't the same true of EV's? Why else our concern over vehicle weight, transmission efficiencies and rolling resistance?

*Wild AC is unregulated with respect to either voltage or frequency and only useful for resistive loads.

PVs in this country haven't been of much practical use so far as they have been prohibitively expensive and other than a few garden LEDs there's not a lot out there currently in the UK for PVs

PV's are getting a LOT cheaper and there is talk of oversupply in the next few years. Did you follow Nigel's link?
Here is a different one.
http://www.heatmyhome.co.uk/solar-panels/?p=537
solar silicon could drop in price by as much as 43% next year. Additionally, silicon wafer prices could drop 41% - and contract silicon prices dropping by 67%
Not good for my PVCS shares, but good for their customers.

[qdos]

There's talk all the time of PVs coming down in price in just the same way as EVs having 300 mile ranges but do we actually see these make it to market?

I do actually know someone who runs his entire house on home generated electricity and sells the surplus on to the Grid but he's fortunate to be living in a converted watermill. For they likes of Joe Bloggs it's just not practical currently which I'm sure is much to the relief of the Electricity Board

I'm just as keen as anyone to see us generating at least some of our own power and I do think it is possible to be self sufficient even in an average 3 bed semi but we do need to cut back on our usage. To a big extent generating your own does make you a lot more aware of how much we waste. In short it's colossal !

[JonSpence]

There's talk all the time of PVs coming down in price in just the same way as EVs having 300 mile ranges but do we actually see these make it to market?

Not quite. The talk of oversupply is usually all in the financial press. You know the likes of the FT or "Shares" or the Investors Chronicle. Oversupply is NOT a good thing for the readers of those mags.

ie to quote from FT
Analysts have predicted that the supply of solar panels will exceed demand by the end of next year, if not before, which would cut the price of components substantially.....Crystalox's discount makes the stock relatively undervalued but investors must weigh the risk of a substantial fall in component prices in the next two years.

Also it's a bit unfair I feel to compare an example of something that has not happened to something that we have historical records for.
According to the data that I have found PV's halved in price between 93 and 98 but didn't stop getting cheaper. Those are historic facts not speculation.

Nor is it speculation to read the company accounts and see how much these companies have invested recently to increase production.

However I can't quible with the rest of your post. Oversupply simply means that there is more available than people wish to buy and hence the price will be lower. It DOESN'T mean that more people will wish to buy the product.