A novel mist-based cooling concept is analyzed with the objective of reducing water consumption in thermoelectric power plants. Additionally, this concept offers the potential to increase electricity generation capacity. The concept involves the integration of two independent mist-based technologies. In the first technology, the cooling tower is replaced with a two stage heat exchanger consisting of air-cooled and water mist-cooled sections. The mist-cooled heat exchanger chills the cooling water to near wet bulb temperature ambient, which enables lowered condenser pressures and temperatures. Enhanced evaporation control through mist cooling allows the mist to reach temperatures closer to wet bulb temperature conditions than cooling towers. In the second technology, the shell-and-tube steam condenser is replaced with a direct contact condenser, wherein Rankine cycle steam condenses on water mist streams. The large area offered by mist droplets increases heat transfer rates significantly, resulting in compact, low maintenance condensers.
Analyses show that mist cooling technology can reduce water consumption by up to 65 %, compared to present-day cooling towers of the same power output. Furthermore, by reducing the condenser pressure, electricity generation can be increased by 4 % while still consuming less water than cooling towers. First-order techno-economic analyses reveal that mist cooling technology can benefit 17 out of 18 coal-fired power plants in Texas. It is expected that this technology will significantly benefit other U.S. power plants located in water-stressed areas.
