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back to article Liquefied-air silos touted as enormo green 'leccy batteries

A technology invented to use chilled air as a power source for engines has been put forward by Britain’s Institution of Mechanical Engineers as a possible solution for storing electricity generated by renewables, such as solar and wind power. One of the main criticisms levelled against renewable energy sources is their inability …

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Penny wise, pound foolish.

They are highly unlikely to achieve that 70% efficiency. It sounds like best case scenario under ideal conditions. But it doesn't matter. This is a solution looking for a problem. No matter how you slice it, renewable energy (aside from hydro-, and in some places geothermal) will never become load-bearing. It is simply too inefficient and expensive to maintain.

We're inevitably going to move to nuclear, even if some people will need to be dragged kicking and screaming. The only question is when - before we lose any remaining competitive advantage to China (and other emerging nations) or after. Right now China is building 25 nuclear reactors and has another 30-40 in the planning stages. For comparison, UK has a total of 18 nuclear reactors used for power generation. As labor cost gap narrows due to globalization, whoever can supply its industry with cheapest energy owns the future. Right now, it doesn't look like it's us.

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Re: Penny wise, pound foolish.

A storage mechanism to store excess generation until its needed is equally useful for nuclear.

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Childcatcher

Re: Penny wise, pound foolish.

"As labor cost gap narrows due to globalization, whoever can supply its industry with cheapest energy owns the future. Right now, it doesn't look like it's us."

This kind of them/us attitude has always bugged me. It's not a competition: no matter where people happen to live they have feelings and families same as everyone else. Fortunately the globalisation you mention will help make borders less relevant.

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Holmes

Re: Penny wise, pound foolish.

A world-wide grid would minimise the need for storage of any kind, and maximise the benefit from baseload generation. Unfortunately, it's a long way off the roadmap for governments and utilities, since it would require strategic thinking, and getting along with the neighbours.

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Re: Penny wise, pound foolish.

I agree, this reminds me of the TATA compressed air car. They were claiming ridiculous efficiencies when in fact the full cycle efficiency was in the single digits. Compressed air is a horrible energy storage medium. Pure gas is a little better, but in the end the thermal dynamic losses of the compression/decompression cycle render it useless for energy storage.

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Re: Penny wise, pound foolish.

@stucs201

Storage mechanism is absolutely necessary for baseload renewable energy and unnecessary for nuclear. They are far from equally useful. Logically, your statement is false.

@Martin Budden

I'm sorry if the realist approach makes you uncomfortable, but us/them division is a natural product of evolving in competing tribes. It has aided the survival. While you may snobbishly consider yourself enlightened enough to dispense with such archaic nonsense, most people in the world aren't. Ignore their views at your own peril.

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Re: Penny wise, pound foolish.

"A storage mechanism to store excess generation until its needed is equally useful for nuclear."

Nuclear plants are by their nature "baseload" plants because they output continuous steady power. Unlike gas or renewable generators they're actually difficult to shut down.

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Re: Penny wise, pound foolish.

"renewable energy (aside from hydro-, and in some places geothermal) will never become load-bearing"

I'm not saying that renewables will ever rival nooclia, but this is a bit of a sweeping statement. The tech will no doubt advance. Who knows what the future will bring?

Anyway, I'm all for trying these clean energies. I'd rather see money 'wasted' on these than the trillions currently pumped into the military.

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@proto-robbie

Wouldn't transmission losses make a world-wide grid unworkable?

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@ Long Fei

"The tech will no doubt advance."

Enough to alter day/night cycle, eh?

"I'd rather see money 'wasted' on these than the trillions currently pumped into the military."

Money pumped into military was instrumental in creating the Internet via which you made this post (military waste is a separate matter). Money pumped into renewables has (paradoxically) increased the price per kWh you pay to run your computer and allowed concrete companies, Chinese factories, and Al Gore to make some windfall profit. I'll take the military spending.

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Re: Penny wise, pound foolish.

"A world-wide grid would minimise the need for storage of any kind"

Do you have the first clue how much power is lost transmitting it across a state, let alone between countries?

"Unfortunately, it's a long way off the roadmap for governments and utilities, since it would require strategic thinking, and getting along with the neighbours."

Its a long way off the road map because it would require re-writing the laws of physics to make it work, not because governments don't want to talk!

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Holmes

Re: Penny wise, pound foolish.

>"Nuclear plants are by their nature "baseload" plants because they output continuous steady power."

Doesn't this mean an energy storage mechanism would be very useful for them too? Otherwise in a fully-nuclear energy economy you would have to dimension the nuclear capacity according to the peak consumption, and then would have overproduction most of the time.

Opponents of nuclear like to point out (at least over here) that because of the inflexibility of nuclear power plants, they cannot rid us of fossil energy plants and their CO2 emissions, because those are needed for responding to the varying load. An efficient energy storage system would counter this argument.

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Headmaster

Re: Penny wise, pound foolish.

I agree with solidsoup, the 70% idea is windowdressing. This thing will have to face the laws of thermodynamics twice, on import and export, so I'd have thought the 25% figure is as good as it gets.

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Happy

Re:This kind of them/us attitude has always bugged me.

LOL best troll this week.

Sir I salute you :-)

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Re: @proto-robbie

Not if it was a high-voltage DC network. HVDC is suitable for long distance transmission, but not short distance.

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«Nuclear plants are by their nature "baseload" plants

because they output continuous steady power. Unlike gas or renewable generators they're actually difficult to shut down.» Well, «Charles 9», you obviously don't live here in Sweden, where nuclear power plants often seem to break down and/or be forced to run with reduced output just during the winter months, when need for power is at its peak. This variablity in output is particularly profitable for our power companies, as electricity from other sources, e g, their hydropower plants can be sold at drastically raised prices....

Henri

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Re: @proto-robbie

"Not if it was a high-voltage DC network. HVDC is suitable for long distance transmission, but not short distance."

Ummmmm, HVDC for long distance transmissions??? There is a reason Westinghouse/Tesla WON the AC v. DC battle you know! And one of those reasons is the inability to transport DC over any significant distances. 3 Phase AC links have much lower transport losses (Or why would EVERY single long distance link already in use be AC?)

Solar and wind will NEVER be a baseload power-supply. The ability to store energy does not a baseload make. A long enough "dry spell" (Several low wind, clouded days in succession and you still lose all power generation.) The idea behind a baseload is that it should be reliable. It should just work.

On top of that, I find the modern wind generator to be but ugly. Solar panels are not much better to look at. And to those about to scream about me wanting a nuclear plant in my back-yard. YES I would have no trouble having a single nuclear plant nearby. I find a well designed one easier on the eye than the eye-sores called wind-generators popping up everywhere.

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Re: Penny wise, pound foolish.

"No matter how you slice it, renewable energy (aside from hydro-, and in some places geothermal) will never become load-bearing. It is simply too inefficient and expensive to maintain...We're inevitably going to move to nuclear,"

Ready to throw your sabots into the wind turbines, I see!

Clearly, your mind is already made up, and no amount of innovation is going to change it.

You state as certainty what is clearly massively uncertain. Viable energy storage or new developments and increased efficiency could be around the corner, so I feel it's foolish to fix your thinking in such a way. Sure: You might be 100% right; but you don't leave much room for changing your mind if the situation changes.

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Re: Penny wise, pound foolish.

"Right now China is building 25 nuclear reactors and has another 30-40 in the planning stages. For comparison, UK has a total of 18 nuclear reactors used for power generation."

Right now, China has a population of 1.3bn, is a huge country with a rapidly expanding* economy. For comparison, the UK has a population of 63 million, is a tiny island and has an economy which is in the shitter.

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Anonymous Coward

Re: Penny wise, pound foolish.

"but in the end the thermal dynamic losses of the compression/decompression cycle render it useless for energy storage."

I think they're talking about storing the bulk of the energy in a phase change in the fluid, rather than just compressing it. I can't understand why not choose a working fluid which doesn't need to be cooled so much first and keep it in a closed cycle, like propane in an empty gas field for example.

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@imanidiot Re: @proto-robbie

"Ummmmm, HVDC for long distance transmissions??? There is a reason Westinghouse/Tesla WON the AC v. DC battle you know! And one of those reasons is the inability to transport DC over any significant distances. 3 Phase AC links have much lower transport losses (Or why would EVERY single long distance link already in use be AC?)"

A compelling and well written argument. Except most long distance links are DC. Especially where they go under the sea. Check it out on Wikipedia. :-)

(Nice username though.)

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Re: @proto-robbie

@ imanidiot:

"Ummmmm, HVDC for long distance transmissions??? There is a reason Westinghouse/Tesla WON the AC v. DC battle you know! And one of those reasons is the inability to transport DC over any significant distances. 3 Phase AC links have much lower transport losses (Or why would EVERY single long distance link already in use be AC?)"

While it was certainly true in Teslas time that DC was unsuitable for long distance transmission, and AC was better, it's just not true now.

A simple search for power transmission will give you lots of information, and if you're interested in specific examples, you can search for "Pacific DC Intertie" which should get you info on one example which is over 800 miles long.

Using DC now with modern technology is better than AC which introduces all sorts of issues when tying disparate grids together.

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Mushroom

HVDC - @imanidiot @proto-robbie @AC

The reason why all long-distance links are HVDC is very simple:

Every single generating set in a linked AC system has to be exactly* in sync, as otherwise they end up consuming power instead of generating it.*

It would be incredibly complicated and extremely unreliable to try to keep all of mainland Europe in sync with each other, or even just keeping France in sync with the UK.

On top of that, once there's more than one link with enough geographic distance between them it becomes impossible due to speed-of-light delays.

So we use HVDC for these long-distance links between different Grids - that way we don't have to keep our generators running at exactly* the same speed and phase as the French.

Originally these really were big DC motors driving big AC generators (and vice-versa)!

- High-power silicon is now good enough for solid-state versions, which are much better as they can sync instantly and as well as being more efficient.

Icon for what happens if you don't sync the generators.

* Rather simplified.

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Re: @proto-robbie

The reason why AC won over DC in Edison's day was more to do with generation than transmission, plus issues with stepping up the voltage. You can transfer HV DC a lot more efficiently than HV AC. This is why most power lines from off shore wind farms are DC.

With modern power electronics it is far more efficient to convert fro AC to DC and back again. Similarly renewables such as wind farms are moving to DC generators so removing another inefficiency in the chain. World wide energy transmission is more an element of cost and politics than technical issues.

You are welcome to your opinion as to the beauty of wind, personally I find them quite elegant. Certainly I would prefer living next to a wind farm than the local coal powered station I do now.

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Re: Penny wise, pound foolish.

"Pure gas is a little better, but in the end the thermal dynamic losses of the compression/decompression cycle render it useless for energy storage."

You might like to read the article a little more carefully.

What is being proposed is liquifaction *not* compression.

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Unhappy

Re: @proto-robbie

"You are welcome to your opinion as to the beauty of wind, personally I find them quite elegant. "

It's the <26% duty cycle (for onshore wind) and the fact *something* (probably connected to a fossil fuel supply) that will have to take up the slack I find rather ugly.

Although I've heard their low frequency/high amplitude noise output is pretty irritating as well.

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Re: Penny wise, pound foolish. @Charles 9

"Nuclear plants are by their nature "baseload" plants because they output continuous steady power. "

That is truly a great feature, if we were using the energy evenly spread over a 24 hour period. Unfortunately, 70% of our energy is used over a 12 hour period. The other 12 hours, nukes "pump" excess electricity into the ground. That combined with an average of 60% loss in transportation (official EDF figures) ...

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Happy

Re: @ Long Fei

Come now, the tech to provide permanent sunlight to a specific point on the Earth via space-based mirrors is readily available. But we don't actually need to do it right now so why pay? Clouds and lack of wind on the other hand are still a work in progress.

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Re: Penny wise, pound foolish.

"A storage mechanism to store excess generation until its needed is equally useful for nuclear."

No it isn't. A nuclear power station can provide a steady level of output and can be ramped up or down to adjust for changes in demand. A means to store excess power is therefore of only marginal use for nuclear because mostly it wont be generating excess. As the storage and retrieval process of power has inefficiencies, it is intrinsically worse than just getting the right amount of power output in the first place. Wind power cannot produce a steady level of output and only ever produces the right amount of power needed as one moment of intersection on the graph as it slides lower or higher that what is actually desired. Therefore a means to store excess generation of power is highly useful for Wind Power. Ergo, the mechanism is not equally useful for nuclear as it is for wind power (and other renewables to a greater or lesser extent). For nuclear, it is of marginal value (I don't say no value).

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FAIL

AC grid

@Robbie The reason why all long-distance links are HVDC is very simple: Every single generating set in a linked AC system has to be exactly* in sync, as otherwise they end up consuming power instead of generating it.*

Utter nonsense I'm afraid. An electricity grid is self-synchronizing in the same way that two people pedalling a tandem are self-synchronizing. If something synchronous (generator or motor) gets even very slightly ahead, it will start supplying energy to the grid until it is back in synch. If it gets behind, it will start draining energy until it has once again attained the same speed as everything else. If the total power drain exceeds the amount of power going in, the frequency and voltage of the whole grid will droop, until regulators at individual power plants notice this and open valves to increase the flow of steam to the turbines. The regulation is totally decentralised. There's no single control centre, no master grid-regulation station that could be attacked by terrorists.

The only time there might be trouble is if a (synchronous AC) generating plant gets disconnected from the grid and has to be reconnected. This requires careful monitoring of both the frequency and phase of the plant to make sure that they both match the grid before the connection switch is thrown. Otherwise, there would be a massive surge that would blow "fuses" and probably break many other things.

As for HVDC, as other people have observed, technology has advanced since Tesla and Westinghouse's day. Transmission losses are reduced with HVDC, and HVDC to grid-AC conversion is no longer impossible or uneconomic. Long-distance HVDC has another large bonus. It is immune to the effects of solar storms (which increase as the length of the line increases). If a huge CME induces a DC current in a DC line, it either adds to or subtracts from the power being transmitted, but it doesn't appear as any sort of abnormality to the plant at the ends. When the same happens to a conventional AC line, the DC current cannot be transformed by the transformers, and instead becomes waste heat inside the transformers. If someone doesn't break the circuit fairly rapidly, the transformers catch fire. In other words, either we suffer a short-term blackout or a long-term blackout (possibly an end-of-civilisation blackout were all the safeties to fail). Had a Carrington event occurred in, say, the 1960s, this would have been a real possibility. Today, we know to watch our sun closely, and to cut the power to save the grid if it throws another big belch at us).

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Re: @proto-robbie

That would have been a good argument 25 years ago, and it's one I've previously made myself ... but since then I've taken the trouble to familiarise myself with the more recent advances in voltage transformation and electrical transmission technology.

Long story short, AC is a good tech for driving synchronous motors, and ramping up power generated from low-voltage alternators to high voltage for long distance transmission, but when you take those two things out of the equation it is itself actually rather wasteful. Hence why very nearly all electrical devices that aren't synch motors or simple heating/lighting filaments internally run on DC.

Back in the day - especially Edison & Tesla's day - converting between LVDC and HVDC was a difficult and wasteful, if not flat-out impossible task, whereas doing so for AC required a lump of magnetised iron with a bunch of wires wrapped around it (and then, if you needed DC back out the other end, a liquid-mercury-and-spark rectifier and some kind of primitive capacitor). Nowadays, we have high power MOSFETs, IGBTs and the like which allow us to convert DC voltages much more easily and efficiently than hooking up a motor and a dynamo on the same shaft, or shedding most of a high supply voltage as heat through a high-ohm resistor.

This page may also be of some interest to you

http://en.wikipedia.org/wiki/High-voltage_direct_current

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Re: @proto-robbie

Oh, and also... coal generators break down just the same as anything else. As can the supply. By your standards, that precludes them from being a baseload generator as well.

There are very few seconds out of the year where the air over the whole UK is so still as to preclude wind generation, and very few hours per year between sunup and sundown where the sky is so dark you can't get at least SOME power out of a PV array. Even when it was chucking down with rain under gloomy skies recently the few-kW experimental installation at my workplace was still making 700w. Sure, that's not a great deal even vs its modest maximum, but it's something.

And who says we wouldn't retain a few traditional type power plants, able to be brought into service with a few hours' notice if the energy store was running down and we needed a backup?

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Anonymous Coward

Re: Nuclear plants are by their nature "baseload"

Sure. But this storage mechanism could be used to adjust output according to demand, in situations where the "base-load" plants cannot match te inevitable fluctuations in demand. And since we're getting (some) wind/etc renewable power generation whether you like it or not, this kind of tech will at least help iron out their intrinsic variability.

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Re: Penny wise, pound foolish.

Not really, you can slow down nuclear production, and speed it back up again too...

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@Psyx

The situation you're describing is the day/night cycle. Currently, solar energy is 4x as expensive to produce (including capital & fuel costs) as coal/gas/nuclear. The efficiency of most solar panels is ~15%. It would take four-fold increase in in efficiency just to get even with our current cost of generation for all other methods. But wait, we didn't account for the fact that the energy needs to be stored for the nighttime use. Even assuming this liquified air system's unrealistic 70% efficiencies, it would require solar cells to have 86% efficiency. That's very fortunate as it happens to be the Shockley–Queisser theoretical limit for solar cells with infinite layers. We've gained about 0.5%/year in solar cell efficiency since 1980. At these rates, we should be hitting the theoretical limit, oh say, in 2130. So, there you have it, in a best case scenario, you need 2100s solar cell technology to match 1800s coal technology and 1950s nuclear technology electricity generation cost. Do you agree with me that solar is useless?

Now as to wind. It should be noted that it's also subject to day/night cycles, but the variance of peak times in different locations make it a little more palatable. However, off-peak energy storage is not really the problem here anyway. Offshore wind generation is similar in cost to solar, but with the exception that wind turbines are already operating close to peak realistic efficiency (unless you have a way of eliminating friction as a force). It means that it will never become competitive with other energy sources.

Onshore wind is slightly better. In fact, according to Parsons Brinckerhoff study it's directly comparable to nuclear (8-11 vs 8-10.5p/kWh). That's with one small caveat. It didn't account for all the subsidies and tax breaks given to wind power. If it had, you would be looking at 1.5-2x the cost of coal/gas/nuclear. Note that economy of scale doesn't apply to wind. The windiest spots that are cheapest to develop get snatched up first. It means that wind power would actually get more expensive, not less, as it's scaled up. And that's before we take into account having to store excess peak power due to wind variability. It doesn't matter whether their efficiency is 25% or 70%. Wind will never become economical. And that's in the UK, which is one of the best countries to utilize wind in. What's everyone else supposed to do?

In conclusion, we both made up our minds. I did so based on current and projected figures and you based on a pipe dream that may happen around the corner. That's all fine and dandy, as long as the ruling class doesn't socialize the cost of that pipe dream. I, for one, don't see why I have to pay higher fees for energy, so that you can have a warm and fuzzy feeling generated by the marketing campaigns of environmental lobby.

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Re: HVDC - @imanidiot @proto-robbie @AC

"Icon for what happens if you don't sync the generators."

I've seen the the result of connecting a 1MW diesel gen set to the grid out of sync. The stator (the clue's in the name) rotates by the phase difference. Apparently the bang was quite loud!

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Re: @proto-robbie

I'm afraid you're waving your ignorance around in a big way there. Fom a purely technical level, DC kicks AC's arse. Anything with AC behaves like a radio transmitter, and that saps power which you would rather be selling to your customers. DC simply doesn't. If you want to talk theory, there are reactive losses for AC (extra impedance due to capacitance and inductance) which just don't apply in DC-land.

There's a better reason why Westinghouse won the AC v. DC battle - and it's that if you don't have semiconductors, getting high-voltage DC back down to low-voltage DC is a seriously complicated procedure, and if you can't go high-voltage then you need much thicker cables. With AC though it's dead easy to use transformers to step voltages up and down, so back in the Westinghouse/Tesla days, it was AC all the way. But now we have these things called "transistors" and "diodes" which you may have heard of. In fact transformers are still more efficient than semiconductors, so local grids still use AC - but start pushing power over any real distance and AC gets proper f*cked from the extra losses in umpty-tum hundred miles of cable.

So since the 50s MOST long-distance links were HVDC, and since the 70s EVERY single long distance link was HVDC. Do yourself a favour and google "HVDC".

(PS. Yes, I did actually have a job at a place which designed and built HVDC equipment for national grids, once upon a time.)

FWIW I happen to agree with you on alternative sources and nuclear, although the fact that you can't rely on alternative sources isn't a complete disaster. If you've got a few days of storage lined up, you've got plenty of time to start ramping up those power stations which have been offline for the last month or two. All you need is to ensure that all the offline power stations can meet the nation demand if necessary. So it won't let you get away with fewer power stations, but it *will* let you cut their fuel bill pretty dramatically.

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Holmes

Re: Penny wise, pound foolish.

Also, for comparision, China has an area of 9.6M million square kilometres compared to the UK's 250,000 and a population of 1.3 billion compared to our 60 million. I don't thinka a comparison of the number of nuclear reactors each country has has anything to say about competetiveness.

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Re: Hans 1

Haven't you read the word "baseload" in the bit you copied. Do you not understand what baseload is. It means the base or minimum level at which power is forecast to be required 24/7.

It's obvious that we use more power in winter for heating than in summer and more during the day than during the night. Power stations can be adjusted to cope with these forecasts very easily. So no baseload electricity is pumped into the ground.

What might get pumped into the ground is the output from wind turbines spinning madly in a gale in the middle of the night.

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Re: @Psyx

"It would take four-fold increase in in efficiency just to get even with our current cost of generation for all other methods. "

And so what, its completely irrelevant. If you get a 4 fold increase in efficiency but it costs 8 time as much to make and run, then you are worse off. You need to reduce the unit cost to make the stuff economically viable, no more no less. So half as efficient at 1% of the cost and you would be more than good to go for example.

Low interest rates will also help, as then the up-front capital costs become easier to absorb, otherwise after about 25 years net present cost of fuel for a coal station is effectively zero, just like solar.

Oh, wind turbines are limited by the Betz Law, not by any considerations of friction, and again the price of energy has sfa. to do with the efficiency of the machine, ih has to do with how much it costs to buy, how much it costs to run, how long the machine will last, and how expensive it is to borrow money. (and how much it costs to get rid of the stuff afterwards, but I believe it is normal to ignore this when you look at nuclear :P, or just build an extra reactor or two to cover the disposal costs if you live in Britain! ).

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Boffin

@Solidsoup

To be competitive, soalr doesn't need to be four times more efficient than it is now, the ration of efficiency to cost needs to be four times as great. It is much more likely that this will be obtained by a combination of small increases in efficiency, and large reduction in the cost of manufacturing the materials and economies of scale cut in, and the technologies continue to mature. In reality, this is what we are already seeing.

So yes, solar is currently more expensive than other forms of generation, but if you were to draw a graph of cost per kWh over time for each type of power generation, you would see that the cost of solar is creeping down, whilst gas and coal are increasing as the fuels become more expensive to extract. There will come a point where those lines cross, and solar will be the economic choice.

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Facepalm

Re: Penny wise, pound foolish. @Hans 1

"nukes "pump" excess electricity into the ground. That combined with an average of 60% loss in transportation (official EDF figures) ..."

Go on then, produce evidence that supports 60% transmission losses for nuclear power. I say that's crap, and that you should think more carefully before posting such nonsense.

UK electricity generated amounts to 29.5 MTOE (DECC aggregate everything to MTOE), and distribution losses and use amount to 4.5 MTOE, so that's 16% losses on average, mostly on the LV side which affects all sources equally.

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Re: @Psyx

@dkjd

You're absolutely right that efficiency is not the sole factor, but I've never claimed it to be. It's simply the one that's ostensibly easiest to modify and the one that people look up to future technology(tm) to solve. It would've been nice if you provided some data to support the assertion that price decreases in materials would make it all better. But the truth is, there isn't any. I don't have any data on wind, but its hard to imagine construction costs of turbines going down significantly. Solar, on the other hand, has been approaching an asymptote in terms of price per W. See this: http://blogs.scientificamerican.com/media/inline/blog/Image/naam-solar-moore_s-law-1.jpg

Betz law limit is ~60%. However, most turbines get only 30% efficiency for energy extraction (assuming constant wind). Most of that loss is due to friction. You can't do anything with Betz law, but friction can potentially be addressed (though not at all effectively).

Nuclear companies are required to amortize the cost of decommission of their stations and set up special funds for that purpose into which they pay from operating proceeds. All nuclear electricity cost estimates already account for decommission. Nice straw man though.

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Re: @proto-robbie

Absolutely. Instead of power grids we need to distribute the power generation.

http://en.wikipedia.org/wiki/Micro_nuclear_reactor

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Re: @markp 1

"There are very few seconds out of the year where the air over the whole UK is so still as to preclude wind generation, "

If only that were true. In some quarters the capacity factor of onshore wind has been as low as 14% for three whole months. Given that there were some windy days, that's a whole bundle of seconds (amounting to weeks)when there was no useable wind power. And when you get a winter high pressure zone you'll find that there may be no useable wind across all of northern Europe, whilst electricity demand goes through the roof.

Regarding the PV output, I see yet more touching optimism on your part, but as a rule at these latitudes you'll get only 25% of summer output in January, and on any day stuff all output outside 8:30 and 17:00 local. So two thirds of the time PV isn't available because the sun is below the horizon or has poor azimuth, and for one third of the year the output is crap even when the sun is up. If you want to use solar it makes sense to move to Spain.

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Re: @Psyx

It doesn't really make a lot of sense to compare the efficiency of a thermal plant to solar.

If you are saying solar is useless because it's total free energy in / electrical out is less than the Carnot efficiency of burning coal then you should also include the solar energy to make the coal in the first place.

On the other hand saying it's useless because it's expensive and unreliable is perfectly true

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Re: Penny wise, pound foolish. @H@rmOny

Errr - hate to point out the flaw in your argument. If we went 100% (or even close it it) nuclear there would be a huge need to store that excess power because it would have to be set up to meet peak power demands - which afaik are much much higher than the average.

Ergo Nuclear would benefit almost as much as Renewables from this technology.

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Stop

Re: @proto-robbie

> Although I've heard their low frequency/high amplitude noise output is pretty irritating as well.

You've heard wrong.

You have to literally be standing right next to a modern windmill to hear anything at all. The older ones were pretty whiney, but the modern equivalents are practically silent.

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Re: @proto-robbie

HVDC has much lower losses during transport than HVAC, which is why it's commonly used on long (400km+) runs and subsea cables. See http://en.wikipedia.org/wiki/High-voltage_direct_current

The issue at the start of the 20th century was that AC is easy to step up/down via transformers. This was particularly important in Tesla/Edison's day but addressable these days using large inverter systems. Edison was always interested in local generation in order to sell heat as well as electricity, but the lousy economies of having to build/run a small generating station every 2-3 miles is what finally killed off DC. Larger plants are far more efficient and hydro/geothermal resources are seldom close enough to where the demand is for Edison-style DC to work.

Railway traction supply systems commonly use DC or 15Hz AC for the same reason (reduction of trasmission losses). The tradeoff for low frequency AC is bigger transformers, but that's not an issue in most cases.

AC is still a win for local distribution or for lines where power needs to be transported in both directions (but modern electronics is making bidirectional DC links more feasible)

Aircraft use 400Hz to reduce transformer iron. it works for them, but such frequencies for long distance power distribution would have devastatingly poor efficiency.

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