GE Global Research has come out with an experimental desk-size turbine that has the capability to power a small town of about 10,000 homes. The unit is designed to be operated by “supercritical carbon dioxide”. In this state, carbon dioxide will be neither a liquid nor a gas and will exhibit a very high pressure and temperature of 700 Degree Celsius. Supercritical CO2 will be passed through the turbine to produce the electrical power. The resultant CO2 is again cooled and repressurized in a closed loop to send it again through the turbine for another pass.
The compact size of the unit and rapid turnaround time (ability to turn on and off) will make it very useful for grid storage. It is one-tenth of the size of a steam turbine with similar capacity. Efficiency wise, it is stated to be 50% efficient in turning heat into electricity whereas the steam based counterparts are only around 40% efficient. This whopping 10% improvement is possible due to improved heat-transfer properties and reduced need of compression system.
The current prototype used by GE is of 10 megawatts. GE is planning to scale it up to 33 megawatts. The most attractive part of this technology is that it is nimbler in the grid storage scenario. Heats generated from solar, thermal, nuclear or combustion could be stored as molten salt and subsequently be used to drive the process.
This kind of heat reservoir is used to boil water so that it can be used to power a steam turbine. While the conventional turbine takes around 30 minutes to be cranked up, the CO2 based turbine gets ready in a minute or two which makes it perfectly suitable for on-demand power generation during peak hours.
This system by GE’s is likely to be better than huge arrays of batteries. More hours of operation translate into having a larger or hotter reservoir of the molten salt. No additional array of large battery is needed here. “The key thing will come down to economics,” says Doug Hofer who is the engineer in charge of the project. There are more work in hand, he says, “at this point we think our economic story is favorable compared to batteries.”
Author: Technology Vista
