Fall wind power plant

An Energy Tower or Abwindkraftwerk is a theoretical heat engine to use the small temperature difference, which may be caused by the evaporation of water in ambient air. The air cooled at the top of a high chimney and therefore denser, creates an overpressure at the bottom compared to the outside air. Turbines extract energy from the artificial fall wind to produce electricity .

The type of power plant was described and patented in 1975 by the American engineer Phillip Carlson. Since the 1990s, the Israeli Dan Zaslavsky from the Technion in Haifa has been trying to develop and implement this technology.

interpretation

The evaporating water removes heat from the air. Below the zone in which the sprayed droplets evaporate, the temperature increases with the dry adiabatic temperature gradient downwards. The air enters the turbine (s) and is isentropically expanded there. Despite the monumental height, the efficiency remains significantly below the efficiency that a Carnot cycle would have in the same temperature range. The energy requirement of the pumps for the water to be evaporated also contributes to this, which would amount to a third to half of the gross output in the planned systems.

As the overall height increases, not only do the flow losses increase, but the temperature of the outside air, the saturation vapor pressure and thus the cooling effect also decrease. Tower heights of up to 1200 meters were proposed, with which a temperature difference of up to 12 ° C could be achieved in good locations.

Flow velocities of up to 20 m / s are provided. Flow losses decrease with increasing diameter; diameters of up to 400 meters have been proposed.

Only with a system of this size, with a net output of 350 to 400 megawatts, electricity production costs of around 3 ct / kWh can be achieved.

Comparison with the updraft power plant

Gerhard Weinrebe and Wolfgang Schiel compared the downwind with the updraft power plant . With the same dimensions of the chimney, the updraft power plant with its higher (optimal) temperature difference delivers three to five times as much the net downwind power plant (pumping power subtracted). On the other hand, building the collectors of the updraft power plant requires larger land areas and investments. Both types can also produce less electricity at night, whereby the heat accumulator is to be arranged at the bottom of the collector or is free of charge (the free troposphere cools only slowly). Both types are sensitive to unfavorable meteorological conditions: the updraft power plant benefits greatly from high insolation (global radiation) , the downwind power plant from low humidity. The conditions given by Zaslavsky (1999), 45 ° C on the ground and 16% relative humidity, are very favorable assumptions.

Locations

Particularly warm and dry air is the hallmark of the desert climate . Large amounts of water are also required. This means that construction in the (central) mountains and in deserts remote from the coast is ruled out. Sea water can be used if the remaining salt spray is deposited. Most suitable would be locations at 15 to 30 ° north or south latitude on the arid west coasts of the continents ( Sahara , Namib , Atacama desert ) including Australia . There the Hadley cell provides dry air from the upper troposphere and offshore wind.

Individual evidence

1. ↑ Patent US3894393 : Power generation through controlled convection (aeroelectric power generation). Applied on May 2, 1974 , published July 15, 1975 , applicant: Lockheed Aircraft Corporation, inventor: Phillip R. Carlson. ‌
2. ↑ Dan Zaslavsky: Energy towers for Producing Electricity and Desalinated Water without a Collector ( Memento of the original from May 12, 2014 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . ISES 1999 Solar World Conference Proceedings, 4. – 9. July, International Solar Energy Society (ISES), Israel Ministry of Science, Jerusalem. 
3. ^ Gerhard Weinrebe, Wolfgang Schiel: Up-Draft Solar Chimney and Down-Draft Energy Tower - A Comparison . ISES 2001 Solar World Congress.
4. ↑ S. Hassid, I wish Samer R. Guetta: Energy Towers - The effect of droplet coalescence on power and the environment. Solar Energy 86, 2012, 1443-1453.
5. ↑ Gregory Czisch, Dan Zaslavsky, Rami Guetta: Evaluation of the Global Potential of Energy Towers ( Memento of the original of May 12, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . Research Proposal, 2001. 
6. ↑ T. Altmann et al .: Assessment of an "Energy Tower" Potentials in Australia Using a Mathematical Model and GIS ( Memento of the original from May 12, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . Solar Energy 78, 2005, pp. 799-808.