Formula and value explanations

Back

m = metre, m2 = square metre, m3 = cubic metre, m/s = metres per second, km = kilometre

SC = Solar Constant/flux, here, amount of solar energy hitting the surface of the Earth. The solar constant value entered should be the yearly average for the region.

DSC = Dye Solar Cells or Graetzel cells

µg = microgram, (1/1'000'000th of a gram), mg = miligram (1/1000th of a gram), g = gram, kg = kilogram (1000 gramms),

w = watt (1 joule per second), Kw = kilowatt (1000 watts), Kwh = kilowatt hour (1 Kw over 1 hour)

The average m2 of a SCAF, given as 452 m2, is the minimum surface area of a SCAF. This will change if the Av diametre is altered.

The m2 of DSCs is half of total SCAF area. The solar constant of the DSCs is slightly lower than total to account for energy lost through reflection etc.

DSC efficiency is put at 10% which is it's current efficiency level but recent advances have increased this to 11% and more increases in efficiency are expected.

The number of SCAFs in a network should be 10 minimum.

Chimney and filtre windspeed values are found using the following equation,

Where:

p=Air density inside found using the formula 1.293*273/(273+Te)

Cd=intake coefficient set at .07 to account for filtres

Ar=chimney area (5% of filtre area)

As=filtre area (currently set at 75% of exterior wall area)

g=gravity (9.81 m/s)

T=temperature difference

Te=temperature outside

Hrs=height of structure

Crs=Wind effect coefficient 

v=outside wind speed (m/s)

The power available to the windmill is calculated with the following formula, P=Rho*A*Cp*V3*Ng*Nb

Where:

P = Power (in Watts)

Rho = Air Density

A = Rotor sweep area (m2) exposed to wind 

Cp= Coefficient of performanc (.59 is the betz limit and .35 for a good design)

V = Wind Speed (m/s)

Ng = Generator efficiency (80 for a good one)

Nb = Gearbox/Bearing efficiency <> 95%

Filter efficiency can go up to 85% but this reduces the flow through rate. By using a filter with lower efficiency the flow rate is increased, filtering more air and allowing the SCAF to function normally.

The chimney area is 5% of filtre area.

The pollution filtered from the air is calculated by multiplying the filter m2 by the filter flow rate by the ug/m3 of pollution and multiplying that by the filter or activated carbon efficiency rating.

The final energy produced total is in fact 95% of the total to allow for transfer losses.

The filter area is 75% of the exterior wall area. 

info@scaf.ch