The Carnot Cycle efficiency of such a system is appaling.

I suggest that the most efficient engines use fuel that will run out, or minerals ditto, and while they remain in use they are damaging our ecosystem, might be a good reason not to shy away from alternatives which are less efficient but more sustainable.

And particularly if they are excellent for driving fridges which it happens are needed, right now, to get us through a disaster.

Cheers, Tim

Yes but it doesn't matter because green is so cheap. Conversion efficiency only matters when the input is expensive. Coal and oil have to be extracted, processed and transported, which costs a bomb, whereas the sun just shines.

A sunny day with a half decent breeze delivers far more energy than we need and the input costs nothing. But ways of storing it are needed because green energy comes and goes at the whim of mother nature. The through life cost of storage matters, but not efficiency because green energy is wasted unless some of it is stored.

Dave

Where does that info come from? As far as I can see, installed wind capacity is 24GW and installed solar is 13.4GW. That is installed capacity, not actual output. Max Demand earlier this evening was 42GW. This website shows interesting info on the actual generation mix. If you look, a high proportion of electricity is from gas – doesn’t go below about 25% at any time.

**LINK**

We've been down this road before, briefly

1. you can't compress nitrogen to a gas, you have to cool it. Anybody who says you can has lost my attention from then on
2. storing energy as compressed gas is wildly inefficient (as others have said). It was used in mining locomotives, but not widely
3. the amount of energy that can be stored by raising weights up mine-shafts is trivial compared with the likes of Llanberis Magic Mountain
4. green energy s only cheap if you can build the windmills and solar panels for nothing, you can't which is why we've had a green levy (ie more expensive power) to kick start it. Even after you've paid off the capital you still have to maintain it, which is neither easy nor cheap when it's offshore

If there is lots of 'free' liquid nitrogen left over from making liquid oxygen, why not just build a dewar flask into the lorry and use the evaporating gas to keep the lorry cool

Don't get me wrong, I'm all for renewables, but let's not waste money on technologies which are unlikely to be much use.

Edited By duncan webster on 12/01/2021 00:43:35

Hardly an original or unique idea. I'm sure we had a forum thread recently that included a drawing of a proposed nitrogen power station, full sized gigawatt type thing. Based on sub-cooling nitrogen via refrigeration with cheap green power when it was available on sunny windy days etc then releasing the liquified nitrogen to drive turbines and the like when extra power was needed on cold windless nights etc. Perhaps someone with better search skills than mine can find it. Seemed like it was getting ready to start construction?

This latest story seems a typical example of a technologically illiterate journalist waxing lyrical over some old git in his workshop with a dream project that the rest of the world has discovered and discarded for various reasons, including probably the practicalities of producing, storing, shipping and dispensing liquid nitrogen.

Our local paper used to run a story every year or two about the locally made Lutec 1000 generator that was claimed to produce more power than it took to run it and included all the usual perpetual motion speak of motors driving pivoting magnets and then the increased power driving generators etc. LUTEC FREE ENERGY

500 per cent efficiency, the Cairns Post journalist reports. 500 per cent compared with a car's 40 per cent!!! Scientifically radical, to say the least, but it never stopped the journalists — who majored in English not Science — from spruiking it year after year in breathless terms about saving the world etc. You could plug it into a wall outlet in your house and produce enough power to run the whole suburb etc etc. Saaaay whaaat?

I don't know if their investors, impressed by such reports no doubt, ever got their money back let alone a dividend.There were, apparently, millions to be made but it seems to have dropped from sight.

Not that old mate in his shed with his nitrogen engine is perhaps the same thing but the willingness of journalists to take the word of a lone old git in his shed against the scientific and industrial establishment's is the same.

Edited By Hopper on 12/01/2021 03:39:56

Edited By Hopper on 12/01/2021 03:41:31

Don't confuse capacity with potential! Before canals and railways the energy obtained from coal was tiny despite a good part of the UK being sat on a giant coal-field. To benefit from coal it was necessary to build a lot of expensive infrastructure and to develop new technologies like electricity.

Green energy is the same. There is a development phase. New technology is expensive and unreliable at first, then it becomes cheap and reliable.

Rather than digging up and burning fossil fuels laid down hundreds of millions ago, green exploits solar energy directly. And the amount of energy delivered by the sun to the earth's surface is enormous – about 1.3kW per square metre. In total the Green energy potential is between 4 and 16 million Terawatt/hours per year. Forever.

Everything has pros and cons. On coal's plus side storage is trivial – it can be stacked in a heap – and power output can be controlled by throwing more or less fuel on a fire. Straightforward to manage with primitive methods. Coal also has many disadvantages; it has to be mined, cleaned, graded and transported. It's dirty to handle, tricky to burn efficiently. and the combustion products are polluting. Boilers are expensive to build and high-maintenance. As it took 200 years for the industrial revolution to put coal powered electricity into all UK homes, I think Green has made excellent progress. Although heavily subsidised at first, green today is the cheapest form of energy available in the UK. The 24GW wind and 14GW of capacity installed so far barely tap into what's available.

Cheap and plentiful but imperfect. (All technologies are imperfect.) The big problem with green is how to manage a source that comes and goes with the weather. At present green feeds into the grid and it's been possible to shut down coal generation almost entirely. This is good because the coal is imported from Brazil, Australia and the USA. But it can't replace everything. Green is flawed because it fades in and out at inconvenient moments. So the UK system relies on Nuclear, imported electricity, and Gas to cover the gaps. Effective electrical storage systems would eliminate gas as well, but there is no simple answer. Many options but they are all more-or-less high tech.

Mark's reference to Carnot suggested efficiency mattered, and I'm saying it doesn't in this case because the input energy is free and clean. Provided the infrastructure is affordable and stores a reasonable amount of power, running inefficiently on solar energy can be extremely wasteful without concern. Although the same system is completely uneconomic, wasteful and polluting when powered with fossil fuels, it makes sense when powered by Green energy. The rules change when one form of energy is substituted for another.

Dave

Edited By SillyOldDuffer on 12/01/2021 10:09:34

A relative that lives in Switzerland clubbed together with three other neighbours to have a deep bore hole drilled adjacent to their properties. The cost of drilling this hole was not insignificant at the time but now it’s done all four houses benefit from very cheap heating.

It should be very easy to get FREE energy from liquid Nitrogen!

Air is liquified to get the valuable gases, Oxygen and Argon. Liquid Nitrogen is really a waste product. Get those who want Oxygen and Argon (welders, hospitals, steel makers, etc) to pay for the distillation process. So you then have free liquid Nitrogen. All you then need is a heat engine, of some form, that uses the atmosphere as the heat source and the liquid Nitrogen as the cold sink.

It is just a question of money, not physics.

I think the idea that started this thread (and the similar one a few months ago) considered Nitrogen as a compressed gas, not a liquid.

JA

you certainly can