Power Plant Engineering

2.15.6 RECENT DEVELOPMENTS
The present windmill technology is inadequate for the low wind speed regions in the plains.
Special development projects in the following areas must be taken up so that wind energy can also be
used in the low wind speed regions.
Artificial Winds. Generation of artificial winds to drive windmills by heating large surfaces
with favorable thermodynamic properties is technically feasible. A project report has been prepared to
heat a large surface in which case the resulting current (artificial wind) can drive turbines. The efforts
needed to pursue the project in the form of money, manpower and time are huge.
Aeroelectric Plant. The low wind velocity in the plains can be augmented by the use of diffuser
at intake to wind mills. Besides the propellers, Madaras and Darrieus, there has been a plethora of
designs for wind machines. One intriguing power plant design, called the aeroelectric plant, uses the
flow up a tower that looks like a cooling tower as shown in Fig. 2.10. Its walls are heated by solar
radiation. Since the walls are circular, the sun’s rays need not be tracked as it changes position in the
sky during the day. The heated walls, in turn, heat the inside air and a flow up the tower is established.
This air flow is made to drive a number of air turbines located near the top of the tower. The driving
pressure causing air flow is given by the well-known chimney effect.
P. Carlson of Californica has proposed a slightly modified form in which, the interior air in a
very tall tower would be cooled by pumping water to the top. The water evaporates in the low pressure
air there, causing a downward flow of cooled air. The driving pressure can be calculated in a manner
similar to that for wet cooling towers. A conceptual design of such a plant called for 2.4 km high, 300
m diameter tower located in a hot desert and 10 wind turbines surrounding the tower periphery at the
bottom producing 2500 MW.