When the Wind Doesn't Blow
Jul. 28th, 2008 09:55 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
webfarmerBeen increasingly looking into utility-scale storage lately. Somewhat surprisingly, the compressed air option seems to be in the lead at the moment. You can use it in a lot of locations unlike pumped hydro storage. You can go big like pumped hydro.
The problem area seems primarily to be one of efficiency. A good chunk of the energy used to compress air goes into heat. Those of us who hand pump our bike tires with portable pumps are a little aware of that effect. Conversely when compressed air is released, it wants to recapture that heat. With utility scaled systems, this heat is often provided by natural gas.
So to get around this efficiency loss, folks are designing heat transfer and storage systems. The heat generated on compression is captured and stored. When the air is released, this stored heat goes back into the air. This results in near 70% efficiency. Good enough for govmint work.
Add to that wind turbines designed to directly compress air and things start getting interesting. The wind plant that General Compression is working on, for example.
General Compression Aims to Double Wind Farm Profits - Cleantech - 20 Mar 07
"When the wind blows, General Compression compressors inside turbines are to pump air to over 100 atmospheres of pressure and send the air down the towers into an underground network of high-pressure pipes. The pipeline network is to collect and store 6-12 hours of energy. If the project is sited near a geologic feature such as a salt dome, aquifer, limestone cavern, or depleted gas field, the company projects energy storage times of weeks, or even months."
Storage Technology Comparisons - Capital Cost - Electricity Storage Association
Nice storage technology comparison graphs.
How Compressed Air Could Power the Future - Live Science - 04 Jun 08
"CAES can supply around 100 megawatts of power for several hours, and the needed geological formations (abandoned mines, salt caverns, aquifers) can be found around the world. Other storage devices, such as batteries and flywheels, cannot store nearly the same amount of energy and are much more expensive to install than CAES."
"To improve the efficiency, RWE and GE are working on a new design called advanced adiabatic CAES (AA-CAES), in which the heat that is removed from the air during compression is stored and later used to reheat the gas as it is discharged. 'In this case, the air is hot enough to drive an air turbine without using combustion gases,' Marquardt said. The efficiency could be increased to 70 percent, and if combined with wind power, an AA-CAES system would release no carbon dioxide, a major driver of global warming."
The problem area seems primarily to be one of efficiency. A good chunk of the energy used to compress air goes into heat. Those of us who hand pump our bike tires with portable pumps are a little aware of that effect. Conversely when compressed air is released, it wants to recapture that heat. With utility scaled systems, this heat is often provided by natural gas.
So to get around this efficiency loss, folks are designing heat transfer and storage systems. The heat generated on compression is captured and stored. When the air is released, this stored heat goes back into the air. This results in near 70% efficiency. Good enough for govmint work.
Add to that wind turbines designed to directly compress air and things start getting interesting. The wind plant that General Compression is working on, for example.
General Compression Aims to Double Wind Farm Profits - Cleantech - 20 Mar 07
"When the wind blows, General Compression compressors inside turbines are to pump air to over 100 atmospheres of pressure and send the air down the towers into an underground network of high-pressure pipes. The pipeline network is to collect and store 6-12 hours of energy. If the project is sited near a geologic feature such as a salt dome, aquifer, limestone cavern, or depleted gas field, the company projects energy storage times of weeks, or even months."
Storage Technology Comparisons - Capital Cost - Electricity Storage Association
Nice storage technology comparison graphs.
How Compressed Air Could Power the Future - Live Science - 04 Jun 08
"CAES can supply around 100 megawatts of power for several hours, and the needed geological formations (abandoned mines, salt caverns, aquifers) can be found around the world. Other storage devices, such as batteries and flywheels, cannot store nearly the same amount of energy and are much more expensive to install than CAES."
"To improve the efficiency, RWE and GE are working on a new design called advanced adiabatic CAES (AA-CAES), in which the heat that is removed from the air during compression is stored and later used to reheat the gas as it is discharged. 'In this case, the air is hot enough to drive an air turbine without using combustion gases,' Marquardt said. The efficiency could be increased to 70 percent, and if combined with wind power, an AA-CAES system would release no carbon dioxide, a major driver of global warming."
