Down-Draft Energy Tower
From PESWiki
Down-Draft Energy Towers, proposed by Robert J. Rohatensky, are like an funnel, with a method to remove heat at the top of the tower causing the cold heavy air to fall down the tower and drive electrical generation turbines. The input energy source is solar.
The quotations from Rohatensky's website are done with permission.
How it Works
A down draft chimney utilizes a heat pump at the top of the tower to extract energy and cool air. The cold heavy air falls and creates a downward pressure to drive electrical generation turbines. This is opposite the idea of a solar tower and uses the ground as a solar collector which greatly reduces costs and land requirements.
Contributed Improvements to Displayed Design
2006-08-26 (Robert J. Rohatensky) - A rotating air intake at the top controlled to face into prevailing winds would increase performance and provide radiant heat insulation over the cooling coils. It should also improve system startup.
Benefits
Quoting from http://www.energytower.org
- The design does not require a water source and the construction may be placed anywhere there is daytime heating of air
- The more heat (energy) captured at the top of the tower by the cooling system, the larger the force of the air down the tower and through the turbine. This should provide a highly efficient system where an increase of heat capture at the top provides an increase of the power output the lower turbine.
- The condensation on the cooling coils at the top may be used to provide a clean domestic water source at distilled water quality as a by-product.
- If I understand Professor Zaslavsky's design, his intent is to use the weight of moist, evaporatively cooled air. I propose that cooling the air with refrigerant coils sufficiently will cause air with 100% relative humidity if it contains any humidity at all prior to cooling. Cooling the air with a water mist will only cool until the air is 100% relative humidity and then any additional water added to the system is innefficient, only cooling the air by the temperature difference of the source water. Any energy captured from the falling water is lower than the energy required to pump it to the top.
- A refrigerative system will work in all relative humidity situations, producing more water by-product in high humidity situations. The total energy output should be based on the temperature difference generated at the inside of the top of the tower and the external air at the bottom. This allows this system to be placed in extreme hot arid locations with no available water source and it will produce water if there is any moisture in the air.
- The energy required to pump water to the top of the tower is eliminated and replaced with a heat pump system that should have a positive energy gain (4-10 times the input energy for existing heat pump systems). The heat may be converted to electricity with classic steam turbine (steam could also drive the compressor directly) or possibly a Sterling Engine.
- The system should operate in a wide range of climates with the limitation that there is sufficient heat at ground level to allow for a large air temperature difference to be created by the cooling coils.