15.07.2015   EuroSun2008-3

Static surface vs. tracking concentrating surface

Another issue to take into account is that concentrating solar systems, with concentration ratio C=10, can make use only of the beam irradiation plus 10% of the diffuse one, roughly. On the contrary, non­concentrating systems make use of the global irradiation coming from the sun. Thus, the received global irradiation by a non-concentrating static surface was compared with the beam irradiation plus 10% of the diffuse onto a tracking concentrating surface (Table 4).

Table 4. Incident irradiation on a static non-concentrating surface and on a tracking concentrated surface. Static surface inclination from horizontal is 40° in Stockholm, 30° in Lisbon and 20° in Lusaka.

Static surface vs. tracking concentrating surface

Stockholm

(lat=59.2°N)

Lisbon

(lat=38.7°N)

Lusaka

(lat=15.4°S)

Static non-concentrating surface G (kWh/m2,yr)

1170.0

1865.0

2164.0

North-South tracking concentrating surface Gb + 10%*Gdiff (kWh/m2,yr)

842.1

1518.2

1836.9

Ratio Static/Tracking concentrating surfaces output

1.39

1.23

1.18

The global irradiation incident on a static surface is higher when compared with the beam irradiation plus 10% of the diffuse towards a tracking concentrating surface. This means that a non-concentrating fixed collector receives more usable irradiation than a tracking concentrating one like Solar8. Closer to the equator, the beam irrradiation values are higher and this result becomes less accentuated.