The intensity of solar radiation above the earth’s atmosphere is
around 1.4 kW m2
, whereas the average daily insolation (over
24 h) at the surface is likely to be 200e400 W m2
, depending on
the latitude. During the day the DNI (Direct Normal Irradiation)
may reach 1000 W m2
. This is in equilibrium with the temperature
of a black body near 360 K i.e. about 88 C (stagnation temperature).
On the other hand, a black body at a temperature at 900 C
will be in equilibrium with an incident radiation of 37 kW m2
.
Therefore to act as a heat source for gasification, solar radiation will
need to be concentrated theoretically by at least an order of 50
times, but much more than this in practice. It is claimed [15] that
a concentration of 500 times is necessary for maximum process
efficiency at about 900 C.
A