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alancalverd: So if you are an average family you will need to find space for 8000 car batteries just to cover the 20% of your electricity that comes from wind. At £40 each, that more than doubles the cost of your house. And the batteries will need replacing every 5 years or so.
chiralSPO: Can it be done economically?
The hydrogen economy can be set up at very low cost as we already have the necessary distribution network for most stationary purposes. Centralised storage isn't a problem: oldfashioned gasholders worked at low pressures, modern LPG farms can handle several atmospheres' compression, and the bigger the storage vessel, the more economical it is to fill it with liquid hydrogen.You can burn hydrogen in a conventional gasfired power station any time you need electricity. Indeed the maintenance costs of a hydrogen furnace are much lower than for fossil fuels or even methane.The only real difficulty is using it for transport as the losses from small liquid hydrogen tanks are significant and the specific energy of the gas is too low for aviation, though adequate for urban transport. .
no wind above 5 knots over England
Agreed. So if we had a 100 MW wind or solar (or wave) farm producing hydrogen, and feeding that to a hydrogen-burning power station, would that not solve the problem of intermittency? (provided that one could store enough of the hydrogen to smooth out the seasonal variation in energy capture and demand).
When it is blowing a gale in the North Sea, the Spanish can turn their coal-fired generators back to "idle".
Real world capacity factorsUK Wind average (2007-2012): 27.5%I think making ammonia efficiently could be an alternative (better) use of excess electricity from intermittent renewables, instead of producing hydrogen.
The problem with capacity factors is that they are arbitrary. If I put a 100 kW blade on a 150 kW alternator I can put a 50 kW rating plate on it and claim 20% capacity factor even though it only produces 10 kW.
Interesting. Are you thinking of creating ammonia for use as a fuel/energy storage medium, or as a useful product to make when there is excess electrical energy available, and then finding some other source of energy when there is a deficit?
I know of a company that pays industrial electro-refineries to up- and down-shift their electricity demand as the grid energy balance fluctuates--they never sell any electricity back to the grid, but because the operation is so energy intensive, and would otherwise be going 24/7, a reduction is consumption is equivalent to increasing the available energy for the grid.
I am unclear, following your logic, how you get a nameplate rating would be 50kW in your example. It could conceivably be 100kW, based on the size of the generator installed.
And I would question why such a turbine would use a 50% larger generator anyway. Any increasing in size and weight of electrical machinery in a nacelle, a couple of hundred metres in air must also scale up everything else up as well (tower rigidity etc); there will an additional increase in maintenance costs and, off-shore, this is obviously a serious overhead - thus, a generator, say, 10-15% larger than the blade's continuous rating seems somewhat more realistic.
If I read your figures correctly, a 230 kg 2volt deep cycle unit will give you 3000 Ah. That is 6 kWh, so you need 24 of these to supply 20% of one person's energy needs for 5 days. Add in the controller and connectors, and we are talking about 40 tonnes of battery pack per household. Most believable price today is about $500 per cell, so $50k or so per household for the batteries alone. And then there's the small problem of dealing with 4 tonnes of scrap lead and a few gallons of sulfuric acid every year.
If I read your figures correctly, a 230 kg 2volt deep cycle unit will give you 3000 Ah
Can it be done economically? Not with existing technology,
alancalverd: ... It says that 2.3 tonnes of batterries will supply 400 AH at 240V, and I have no argument with that. That amounts to 96 kWh. Now each person in the UK consumes 5 kW,*** so to supply 4 people for 5 days you need 2400 kWh, i.e. nearly 60 tonnes of batteries.The problem is that people (well, politicians) talk about domestic electricity consumption, but that is only a tiny part of our energy use....
alancalverd: 1. i.e. nearly 60 tonnes of batteries. , 2. ..., then takes about 6 hours to recharge
alancalverd: We'd need 150 Hoover Dams to supply the UK's energy needs, but where would we live, and where would we get the water from?
so some politician's brother in law must be making money out of the scam.
Pumped water storage is a lot of fun. It's very expensive both in land and capital to install, which is why there are only two significant installations in the UK. Dinorwig is the larger one. Its capacity is about 10,000 kWh,[/b] so it can supply all the UK's energy needs for about 0.12 seconds, then takes about 6 hours to recharge.
The problem isn't the size of windmills, though there is a practical limit to hiow big you can make them, but the energy density of wind. Wind speed squared, multiplied by air density, comes out as watts per square meter, so if you want more watts, you need more square meters of wind, not just sail area. You then design the sail to optimise the power extraction from th area you have got, and it turns out that multiple baldes work well for high windspeeds and small areas, but two or three blades are best for low speeds and large areas - it's the difference between a jet engine and a helicopter!.
But that then never solves the problem of compaction (of 4 to 6 x generators on one pole head) ( e.g. the picture of the wind farm here with 1 generator size-(n) output per pole... (think of six times the output from this...)
You can't extract more power than the wind puts in. If your generator isn't matched to the sail, just use a bigger generator.
Alas, no. Friction and inertia are not the problem. It's all a matter of conservation of energy, the lack of appreciation of which seems to run through all your posts! The maximum power you can extract from a windmill at a given air speed, depends on the swept area of the sails. Adding more or better generators will not affect the speed of the wind or the density of the air.