An air mass flow

has a temperature increase

when heated with solar radiation

according to the formula

, where

is the soil absorption factor,

is the glass transmittance factor,

is the density of air, and

is the specific heat of air [1].

The air mass flow as the result of a temperature difference in a stack of height

and cross section

can be calculated by

, where

is the discharge coefficient for the opening (assumed to be 0.65) [3].

Solving the above two equations simultaneously gives the temperature between the end of the collector and the entrance of the stack where the turbine is located.

The resulting power of the turbine can be calculated with the formula

[1].
For comparison, the solar radiation energy on the same surface area as the canopy roof is

.

The following quantities are calculated in the Demonstration:

1.

: the mass flow of air in the stack

2.

: the air speed in the stack

3.

: the power generated in the turbine

4.

: the solar radiation energy on a surface equal to the collector roof surface.

The theoretical background of a solar updraft tower is discussed in [1]. Most of the formulas used here come from this article.

Other interesting descriptions are found in [2].

For a theoretical background of the stack effect see [3].

A working solar tower in Spain is discussed in [4].

For solar tower projects around the world see [5].

[2] J. Schlaich, R. Bergermann, W. Schiel, and G. Weinrebe. "Design of Commercial Solar Updraft Tower Systems." 1000 Friends of Florida.

www .1000friendsofflorida.org.