Generator or inverter?

[Peter Scott]

Duly noted. I didn't realise that they were that good. Still means a lot of UPSs for a steady power supply though.

Peter Scott

[tony sayer]

[The Natural Philosopher]

mm..probably around 90% each way. Say 81%

Well I reckoned about 5 grand..batteries SHOULD do what? 10 years? Hmm. Not as attractive as I thought ;-)

[Dave Plowman (News)]

I'd be amazed if it was anything like that high. Charging Ni-Cads at a

1/10th capacity constant current takes 14 hours. More difficult to work out with a lead acid as the charge current varies with state but my reasonably new 8 amp (says 11) charger won't *fully* charge a 75 amp/hour battery overnight - takes about a day. A good inverter is about 90% though. I'd guess at more like 60%.

Caravan types would know how long a leisure type battery lasts - I doubt it averages at 10 years.

[The Natural Philosopher]

Thats why Nicads are not ideal: Lead acid or Lithium polymer are far better in the charge cycle. You CAN fully charge Nicads in about 6 minutes..BTW. At even worse efficiency.

The inefficiency of the charge cycle is related to how much the voltage needs to rise above the off load voltage..with a lead acid its never more than about 10%.

I know, but here we are not talking massively deep discharges or massively high discharge currents, nor are we talking extremes of temperature. In a house, these things would be running at around a 20-40 hours discharge rate, and about a 1/10th capacity charge rate (i.e. a

110 AH battery charged at 11A or so.

I feel fairly certain that batteries can be optimised for various duties..car batteries are for short duration high peak output. Leisure batteries for lower output but deeper discharge. Here we are talking about optimizing for cycle life. I think 10 years is not unrealistic. Certainly few car batteries will not - if not allowed to go totally flat

- fail after 5 years.

[Dave Liquorice]

But it's not that simple. Your battery bank couldn't realistically operate at 12v. The current demand would be so high that it becomes impractical.

I quite like the idea of using E7 to charge a battery bank then use that for the rest of the day. But in an all electric house you'll need a 10kW+ invertor assuming you want to have a shower and have other things on at the same time. 10kW @ 12v is 833A, it comes down to a more manageable 83A with a 120v battery bank or about 60 wet lead acid cells in series.

Assuming an average load of 1kW/hr you need capacity of 24kWhr for each day, which, (if my maths is right) roughly 200A/Hr per cell. Cells of that capacity are available. Of course you'd need a proper Battery Room (acid proof floor walls, fittings, ventilated etc) for the cells and a fairly rigourous electrolyte testing routine to ensure that all the cells are preforming equally.

Then of course can you thump in enough charge in the available 7 hours to last 24hrs? (You'll still be wanting to draw power during the charging period...). I guess so, assuming 50% effciency raw mains to invertor output and the 1kW average load that comes out at a 7kW charger, small fry for E7.

[Owain]

Why woulndn't you just store the E7 heated water?

Owain

[The Natural Philosopher]

I never said it should. Actually it could and can. 15KW is only 1200 amps or so.

Quite doable on an inverter. Not efficient tho.

Yes. I actually went for about that.

Yup. Within a few percent we are talking the same numbers.

Lithium cells would technically be a better solution - no electrolyte to speak of - but those sorts of capacities are about 10 times the price of lead acid currently.

charger should be 90% efficient or better.

As would be the inverter. 120VDC is just about perfect for modern switching MOSFETS. Now there will be a lot of RF interference, but the thing - the inverter/charge - could be in a shielded grounded box.

I think that an installation like this is on the cards in the next 20 years actually.

If we do go nuclear - and I think we must - the ability to use off peak cheap electricity to power cars and houses is very great.

>

[The Natural Philosopher]

Indeed.

Thats possible a very effective way - do storage heaters 'properly'

[Dave Liquorice]

My telly doesn't run on hot water... but yes splitting the E7 across a water based heat bank and a battery bank probably does drop the required invertor size to sub 10kW. How ever add up the breakfast routine, kettle (3kW), toaster (1 or 2kW), hob (1kW) for porridge plus lights and fridges/freezers, breakfast/kids telly. The peak demand of a single house can be surprisingly high, if short lived, even if 24hr average is less than 1kW.

[Dave N]

Indeed, but I don't think we should overlook the amount of energy required by, and the amount of "hothouse" gases emitted during, the manufacturing processes for heavy duty batteries and electronic control systems, not to mention heavy gauge wiring with plastic coating and large copper terminals. SFAIK, metal smelting processes alone require huge amounts of power and produce toxic gases. Then there is the issue of recycling heavy metals and plastics when the batteries and control gear have reached the end of their working lives.

In other words, supplementing the direct consumption of electricity with stored energy systems in every home will create problems for the manufacture of sufficient plant irrespective of how the electricity is generated. In fact the use of wind and wave power by its very nature implies the installation of large stored energy systems somewhere.

I don't want to appear a doom merchant but I do believe that such matters are significant. I suspect that I am only now beginning to grasp the scope of problems created by an exponential growth in the use of energy by mankind. If I am totally misguided, I would be grateful for correction.

[The Natural Philosopher]

Yep. I reckoned 15KW was about right for peak, and 30KWH for a 24 hour usage.

Actually this got me thinking when I was taking the dogs for a walk..

Tow massive lumps of concrete with holes in, and water pipes (or a working fluid anyway) buried in the ground under the house in loads of insulation..and a third under the lwan..heatpump from one to the other or to teh third..so you have one hot block for heating, one cold block for cooling..and source or sink the difference into the soil..

Because ultimately - if we take overall domestic power., about 80% is used to heat things, about 15% to cool things (reverse in hot summers) and the rest ends up as heat anwyay after doing whatever else it does, like running a computer...

So if you are talkinng nuclear electric, it makes sense to store tehheat rather than the electricity through times of peak demand.

Now how big a block of concrete represents 30KWh over say a 40C temperature span? I found a reference of 0.2BTU per lb per degree F..who is USING such units..ah well..anyway I get 9995 BTU per ton over a 40 C change from that..that's 2.91768532 kWh per ton..so to get 30KWh is about ten tons.

Cripes. That is NOT a lot of masonry at all.The storage heater to end all storage heaters..

Oh..dunno if I did the calcs right, but WATER is the ultimate store. I get around 400KWh per metric ton for a 40C change in temperature.

So there's your thermal store then. Bloody great insulated tank of hot (or cold) water under the house ...

Won't do cooking, but it sure would do house heating or cooling, and cool room stuff.

[The Natural Philosopher]

They are, but less than you might think.

For a start, dont worry about energy used in making stuff. If its all nuclear generated, its zero carbon.

All this 'carbon burnt in manufacture' becomes utterly meaningless if your energy is carbon neutral.

There is an implied shift here, form 'energy conservation' to 'carbon emission reduction'

The actual energy used is a very small fraction of what falls on te earth..that won't affect the climate half as much as the CO2 does.

Very little industrial process actually generates Co2..smelting does a bit, as does concrete making. Smelting you could probably do in order ways than using carbon monoxide aqs a reducing agent..electrolysis for example. I suspect there is no way to make cement without releasing CO2 though. But there are other materials..

Ive actually been to a lead and zinc smelters.. the place was dripping sulphuric acid..and the old batteries were simply tipped into the process at some point to recycle the lead. However we went there to install toxic metal detectors, for the outflows, to monitor mercury and cadmium levels..they are not that bad. Most of the nasties can be separated out, at a cost. So although there are issue, I don';t see them as insuperable. At some level to maintain an industrial or post industrial lifestyle means SOME form of waste will be generated. You have to literally pick your poison..ultimately the best battery material is lithium anyway, which is plentiful and abundant almost everywhere, it just takes a lot of power to extract. But with power cheaper, its not such a big deal.

AND if my last posts calcs are correct, you can keep a house warm with a few tons of stored hot water heated on E7 overnight anyway.

So battery requirements are not huge.

\

I suspect that I am only now beginning to

[Steve Firth]

Concrete making is carbon negative. Taking a large view cement making is close to being carbon neutral, if one ignores the fuel consumption which you seemed to be suggesting is a necessary part of your calculation.

[Dave N]

It is this issue which interests me because AIUI conversion to a system based upon widespread use of stored electricity in homes and vehicles, would lead to an increase of an order of magnitude at least (if not two or more orders of magnitude) in the use of battery systems reliant upon such materials. Perhaps hydrogen cells or motors would be a better solution for stored energy, assuming that electricity isn't too costly? However, as I inferred before, I realise that I do not know all of the facts.

[Owain]

A small one might run on some Peltier cells.

A stored heat cooker could help there.

If you don't use a lot of cooking appliances, and stagger the washing machine and dishwasher (or operate them on E7), 5kW would probably cover most things. People on barges manage with sporadic mains electricity and gas/diesel heating, and they're restricted by the space available for batteries.

Owain

[The Natural Philosopher]

I estimate a tripling of the national Grid in size, ( electrical use of energy is about 30% of total use at the moment: aparet from aircraft and military and specialised vehicles, that assumes everything else 'goes elecvtrioc'

And each household with a car, having 30-100KWh of storage capacity - possibly IN the car, possibly IN the home.

The latest data point I have on lithium cells is this:-

which is about 37 watt hours for $54.99

That puts an undiscounted 37Kwh car pack of 1000 cells at $54,995.

About £27,500 ..which is not - for the equivalent of driving a car on ten thousand 'Rabbit' duracells, unduly expensive.

Note the peak power available from a single cell - 370 watts. so a thousand would be capable of 370KW. Around 500bhp. For about 5 minutes ;-)

Total weight around 200kg for the pack. About what an engine and gearbox comes in at for a small car.

Volume about 1/10th of a cubic meter.

Say 1.5 meters long, by a meter wide, by 6cm thick, tho for high power use the cells need air cooling between them. There is a fire risk associated with these cells, so probably under the floor in the center of the car with a fireproof barrier is the place to put them Good for weight distribution as well. In fact near perfect.

So the cost is about ten times a lead acid solution at the moment, for retail 'hobby cell' prices.

I've been abusing cells like this for a few years. They are now pretty good. At modest discharge and charge rates (which we seldom use) they approach 95% cycle efficiency, and some I have that are rather poor at high power - have showed almost no self discharge in 6 months.

Charge regime is really simple - like lead acid. Limit the charge current to at MOST a one hour charge rate, and limit applied voltage to

4.2v/cell.

Dischrge shows an initial sharp drop of about .1v per cel, then an almost linear voltage reduction down to around 3-3.3v/cell, and then a rapid drop in voltage thereafter: That makes monitoring charge state relatively easy.

The cell chemistry tends to be flammable - althuogh some raw lithium is produce by lithium carbonate electrolysis, that is not the real problem. The solvents used to get decent internal resistance are organics, and highly inflammable. There are tradeoffs between power, longevity, charge rates, flammability and efficiency that have yet to be explored for automotive use.

On a estimated 500 cycle lifetime, of say 200 miles per charge, the capital cost amortizes to 27.5p per mile.

Electricity costs on economy 7 overnight charging? Even at 10p a unit, its £3.70 to 'fill the tank' for 200 miles..so worst case around 1.9p a mile.

Apart from routine lubrication, tyres and brakes (and with regenerative braking possible, less of those too) the annual service charges would be minimal. One would expect - at least in the early days - cell failures, so a routine test and module replace of what would probably be a modular battery, with each module having its own regulation and safety circuitry, would be likely to be the worst costs.

If tax incentives were added on to a car like this, it would further reduce the overall cost per mile.

Most likely way to power the thing would be two or four hub based highly multipole brushless DC motors, with hall effect sensing for commutation purposes. Ironless designs MIGHT bet up around 95% plus efficiency. However the wide speed range over which the motor has to operate would probably not result in much better tan an overall 75% efficiency from power station to wheel. Without a non carbon fuel based power generation, the thing - tho cheap to run taxation wise - is no better on emissions. (Just like the Priapus really).

Why aren;t we doing this right now?

Although te isses of a load of power electronics and chips needing to be developed is one thing in the way - but one that companies like Lucas and Bosh should be able to tackle effectively - the main thing holding it back is that almost nothing of what constitutes todays car/oil industry is of any use whatsoever in developing this technology. I would say that an electric car might use the same steering wheel, seats, pedals and tyres as a conventional car, and the same windscreens. The rest? forget it. All gone.

Likewise conventional garages would be totally ill equipped to deal with the electrical side without major investment in test equipment.

In short,. there is zero incentive to develop this technology. And very many reasons to NOT develop it and hinder its introduction.

Nevertheless it WILL happen. As you can see under current tax regimes its almost economic to run one.

Perhaps hydrogen cells or motors would be a better

No. The hydrogen bollocks - like most greeny bollocks, is as biased as hell, all about 'hey, this is a fuel people *could* use in cars that have the sort of engines we build, and would have to buy at our service stations, and would have to be transported by a fleet of trucks which we have exactly the right infrastructure for'

The conversion efficiencies are dire, the safety is dubious - unless you want a tank of liquid hydrogen with the power of a medium size fuel air bomb, in your car, it needs to adsorbed into a sintered metallic substrate. That's not light.

You CAN make it at power substation sized plants along the M1 by electrolysis, but you certainly wont make it at home..

As far as I can see it simply is nonsense. Its like windpower, its possible, but the overall cost benefit doesn't make real sense.

Nor it seems do those making decisions about all this. And those who DO know the facts are usually employed by companies in whose interest it is to keep those facts to themselves.

I don't mean there is a conspiracy of silience..more like some poor graduate does a design proposal, more or less as outlined above, it goes to the bean counters, they take one look and say 'all I can see is spending a billion to commit commercial suicide and invalidate the rest of our entire operation'

Nonetheless I expect a Japanese electric car - or Korean or Chinese, pretty soon..

[The Natural Philosopher]

Ah. like an Aga.

6 grand of heatbank and cooker combined. ;-)

Yup. Cooking uses surprisingly little power. Its just that rapid heating demands a high peak output. Batteries CAN do that. They are rather good at it.

[Clint Sharp]

I don't know about carbon negative or even neutral but it's a nice way to lock up carbon dioxide. Concrete actually works by soaking up CO2 as it cures because it turns to limestone eventually IIRC. ISTR some research about soaking concrete with liquid CO2 to cure it faster and allow the manufacture of some extremely un-concrete like structures (springs being one that come to mind, if I can find the reference I'll post it.)

[Dave N]

[...]

Thank you for a detailed explanation of your thinking.

It will be interesting to see how Iceland gets on with its plans for

100% conversion to hydrogen fuel cell technology. Sources I've found via the internet appear to agree that storage and transport of hydrogen is the main technical problem.