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A bit of an answer
Posted by mheartwood
2nd Oct
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pumped storage efficiency
Posted by Grids1
2nd Oct
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liquid air
Efficiency is not everything, pumped storage is for instance only 60% efficient. The forte of the liquid air storage is its capability to drive very cheap, reliable and compact engines, and if combined with fossil fuels, this power could be variable & admirable. So it could find its niche uses in peaking plants, harbor tugs, heavy cranes, floating docks, emergency pumps in nuke plants, fire truck pumps, etc., but in cars hardly. Its energy density and efficiency are too low, and its evaporation too fast.
Posted by praoss
2nd Oct
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Would it not be easier and more efficient...
to use that excess energy to turn water into steam and store the steam instead? Certain railroad operations used to use what they called a "fireless locomotive" where a coal-fired steam energy plant would charge a huge thermos bottle (oddball-looking boiler) on a locomotive and get from 8 to 10 hours of functional yard-switching operations out of that locomotive before it needed recharging. It wouldn't be that difficult to use a similar process to store steam created by those wind turbines' excess electricity and use it to drive more highly-efficient steam turbines during the morning surge and maybe even balance some of the summertime air conditioning load.
Posted by DWFields
2nd Oct
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An Answerable Question
@DWFields, your question is an answerable one--I just have not done the calculations. However, safety is also an issue. An equivalent amount of energy stored in liquid air (I do not like this phrase, see below) is probably safer than that stored in steam. A catastrophic release of liquid air will not be as dangerous as a similar release of steam or liquid CO2 for that matter.
Actually the energy is being removed from the liquid air and being deposited in the gaseous air at the compressing station--so there is already waste heat at the compressor site but maybe not as high in quality as that from an industrial site. Creating a colder heat sink for the engine is really all that is going on here.
Actually the energy is being removed from the liquid air and being deposited in the gaseous air at the compressing station--so there is already waste heat at the compressor site but maybe not as high in quality as that from an industrial site. Creating a colder heat sink for the engine is really all that is going on here.
Posted by EmmettRedd
2nd Oct
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Not really the best design
Those designs were mainly used in mines and factories where an open fire could cause a massive explosion. They weren't more efficient than standard steam engines. While they did store steam at a superheated temperature and pressure, most of the energy storage came from superheated water under pressure that was also in the "thermos bottle".
The most efficient heat engines derive their power from converting liquid to a gas (e.g., water into steam, or gasoline into gases from an explosive reaction). We've gotten pretty good at doing this as efficiently as possible. The problem with the liquid air design is that you have the added step of converting gas into a liquid first. You'll always have added inefficiencies from that no matter what.
The most efficient heat engines derive their power from converting liquid to a gas (e.g., water into steam, or gasoline into gases from an explosive reaction). We've gotten pretty good at doing this as efficiently as possible. The problem with the liquid air design is that you have the added step of converting gas into a liquid first. You'll always have added inefficiencies from that no matter what.
Posted by zackers
2nd Oct
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A bit of an answer
Mark either doesn't quite understand what happens in the creation of liquid nitrogen or explain it badly. But what happens in the creation of liquid nitrogen is also part of the answer to your question about "fireless locomotives".
The boiling temperature of any liquid is directly proportional to the temperature but inversely proportional to the pressure. This creates some interesting phenomena. It's why you can use steam to cool a building. If we take water, inject it into a partial-vacuum such that the water's temperature is above the boiling point for that particular pressure, the H2O boils, and in the process, absorbs heat. When we then return the H2O to "room temperature and pressure" it condenses, thus releasing its absorbed heat. This is known as steam refrigeration.
Fireless steam locomotives place the water in a closed container, and then super-heat it. By reducing the pressure within the container, the water is allowed to boil, thus turning it into steam. The problem is, you're dealing with a super-heated material under high pressure.
Using liquid nitrogen means compressing the air. But as you compress the air, it loses its capacity to store heat and thus releases heat. So you carry off the heat to use somewhere else. Once the nitrogen is compressed until it is a liquid, and the excess heat has been removed, you then run into the problem of storing it since if it absorbs heat, it will boil away. Luckily, Liquid Nitrogen is fairly easy to store within a vacuum-walled thermos bottle without it being under high pressure. So while you use high pressure to make it, you don't need high pressure to store it. This makes it a safer storage medium.
The boiling temperature of any liquid is directly proportional to the temperature but inversely proportional to the pressure. This creates some interesting phenomena. It's why you can use steam to cool a building. If we take water, inject it into a partial-vacuum such that the water's temperature is above the boiling point for that particular pressure, the H2O boils, and in the process, absorbs heat. When we then return the H2O to "room temperature and pressure" it condenses, thus releasing its absorbed heat. This is known as steam refrigeration.
Fireless steam locomotives place the water in a closed container, and then super-heat it. By reducing the pressure within the container, the water is allowed to boil, thus turning it into steam. The problem is, you're dealing with a super-heated material under high pressure.
Using liquid nitrogen means compressing the air. But as you compress the air, it loses its capacity to store heat and thus releases heat. So you carry off the heat to use somewhere else. Once the nitrogen is compressed until it is a liquid, and the excess heat has been removed, you then run into the problem of storing it since if it absorbs heat, it will boil away. Luckily, Liquid Nitrogen is fairly easy to store within a vacuum-walled thermos bottle without it being under high pressure. So while you use high pressure to make it, you don't need high pressure to store it. This makes it a safer storage medium.
Posted by mheartwood
2nd Oct
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Export
This would be best produced in cold countries, where the heat removed from the air could be used to warm houses, then the liquid air could be exported and used in hot countries that already have the heat needed to release the air, in the air. Also, it could be used to cool down hospitals etc. in Africa and similar places. "Liquid-air" pipes could run from the polar regions to the equator, and some sort of heatpipes could return heat in the form of hot water.
Posted by Dukhalion
2nd Oct
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pumped storage efficiency
In response to praoss in Liquid Air, pumped storage is not 60% efficient. Older plants are 65-80% efficient. New plants are considered to be 80% efficient.
Posted by Grids1
2nd Oct