Energy tower (downdraft)
In one case, wind power plant, or Abwindkraftwerk is warmed by the sun air cooled by spraying with water and falls into a chimney down. Turbines generate from this artificial air flow electricity.
The type of power plant was first described in 1975 by an American engineer Phillip Carlson and patented. So far, no such power plant has been realized. Since the 1990s, in particular the Israeli Dan Zaslavsky from the Technion Institute in Haifa efforts to the development and implementation of this technology.
Principle of operation
Case wind power plants do not need to convert the solar energy collector. With this principle, only a high fire is used, in the upper portion of water is sprayed. The evaporating water removes heat from the air, it cools to about 12 ° C above the outside air and falls within the chimney at speeds up to 20 m / s downward. At the base of the chimney wind turbines are arranged similarly to the solar chimney power plant, then generate electricity.
The best and most consistent conditions for this type of power plant can be found in the horse latitudes, since the year is over by the Hadley cell warm and dry air is available. Due to the indirect solar gain the technology works even at night.
Economic Consideration
Towers with about 1200 m height and 400 m in diameter should reach at appropriate locations capacities of up to 900 MW or can provide a net power of 600 MW to approximately 2/3 of the year. Case wind power plants would thus on a performance and service life, which is comparable with conventional fossil and nuclear power plants. Although the efficiency is only about 2,5 %, but due to the "infinite " and free resource " warm air " irrelevant. About 1 /3 of gross electricity generated is required as the pumping energy to transport the water to be evaporated to the top of the chimney. Since the efficiency is greatly affected by smaller plants, this means that only large systems appear economically viable. This entails a considerable risk for investors who would have to at least € 1.5 billion muster. The arguments presented by the planners cost of 2.5 cents / kWh at best locations ( coast of the Persian Gulf and the Red Sea, West African Coast, Namib Desert, Baja California, Atacama Desert, parts of Australia ) are therefore not reliable.
Applications in the environment
A great advantage of the technology is that it manages, even without direct sunlight, so also works at night without memory techniques must be used. In regions with large relief differences would add the ability to temporarily store the necessary amount of water in high-altitude reservoirs to call in times of great demand for electricity and at times of low demand to replenish. The power plants could thus theoretically compensate for the fluctuating power demand. Another uses the cost desalination of sea water come ( in the wet, salty wind that would forced through semipermeable membranes ), the cooling of power plants, industrial facilities or settlements, desalination critically polluted rivers and canals and the rearing of fish in the feed channels into consideration.
Environmental influences
The water consumption of such a power plant is about 1 cubic meter per 6 kWh, that is, for the generated electricity in the example of 3.4 TWh / a are required 560 million cubic meters of water per year, which is why sea water is usually used. Here, the lifting of 1 m³ of water absorbs at 1.2 km altitude at 97 % efficiency of the pumping system about 3.2 kWh to complete. The production of desalinated water and the air conditioning and irrigation of the surrounding land through the cool, damp wind that are possible co-benefits of this principle, which could thus offer an interesting option for colonization of desert regions. The salt discharge from the chimney has to be avoided, as this would lead to salinization of the soils. For the same reason, the significant potential environmental hazards due to possible cracks or leaks in the water supply lines / channels arise. The 1000 m high towers could lead to certain landscape impairments, the area consumption is compared to other forms of energy, solar low.
There are as yet no studies to large-scale application of thermal power plants, for example, could be the construction of several hundred such plants change the air layers, with potential consequences for the climate.
Projects
The realization of the first prototype is being promoted for several years in the Wadi Araba in Israel near Eilat, but probably lies in the moment of lack of financial resources. Another project to be launched in India in the state of Rajasthan.
A further development of the type of power plant is proposed by Robert J. Rohatensky. No statement can be made here, however, the technical and financial feasibility.