Super efficient turbines the size of a desk could one day generate sufficient power for entire towns, utilising energy harvesting and reducing emissions.
The new turbine is driven by supercritical carbon dioxide, which is carbon dioxide kept under high pressure at temperatures of 700 degrees Celsius. When thus pressurised and heated, carbon dioxide (and many other fluids) enters a physical state between a gas and liquid — where the boundaries between liquid and gas no longer apply.
The turbine will make use of this supercritical fluid to drive its rotation, which GE Global Research engineers claim will result in increased power generation efficiency.
This approach allows the turbine to be scaled down, but still generate large amounts of output — output that would otherwise only be possible with larger conventional turbines. A steam turbine of comparable output would need to be ten times the size of this new turbine.
The engineers also say the turbine driven by supercritical carbon dioxide has the potential to be 50 percent efficient at turning heat into electricity, while steam-based systems are typically in the mid-40 percent efficiency range. Much of the improved efficiency comes from the better heat-transfer properties and the reduced need for compression in a supercritical fluid system compared to a steam-driven turbine.
The roughly five percent improved efficiency, if applied across the entire energy industry, could be a critical component required to address the increasing demand for energy.
Of course, a turbine works by transforming heat into electricity, so the supercritical carbon dioxide passes through the turbine, after which it is cooled and reheated/repressurised before returning for another pass.
The carbon dioxide itself is not actually consumed in the process, which is designed to be a closed loop in which the carbon dioxide is circulated continuously. The energy to super-heat and pressurise the carbon dioxide can be taken from various sources: solar energy, or waste heat from nuclear power stations, which could be used to generate molten salt needed to heat the carbon dioxide to its supercritical state. The process, the engineers claim, would be much quicker than heating water for steam: one or two minutes to start up, compared to 30 minutes.
The engineers have already created a 10 MW prototype, but hope to scale it up to 33 MW, and eventually to 500 MW. The smaller size, and the ability to turn on and off rapidly could make it useful for grid storage, or even to replace batteries. Rather than having solar panels charge batteries and store the energy for later use, the solar panels could be used to create molten salt that would be used to drive the turbine to generate electricity at high efficiency.