Exergy analysis of solar radiation processes - Solar Energy Sciences and Engineering Applications - page 53

Figure 2.4.5 Effect of combustion of hydrocarbons on CO 2 generation.

For example, due increased pollution, the relatively significant increase from 17%
do 17.5% of the transmissivity τ 0 of the air for the low temperature radiation, causes,
based on formula (2.4.14), a relatively small increase in environment temperature T 0
from 287.16 K to: 44 . 087

· (0 . 175 − 0 . 17) + 287 . 16 = 287 . 38 K.

The main factor considered in global warming is the concentration of CO 2 in the
atmosphere. The CO 2 is a product of combustion of substances containing carbon. It
is noteworthy to emphasize that regardless which kind of compound (fuels or biomass,
etc.), when carbon is combusted there is always CO 2 released into the atmosphere.
Therefore combustion of any compounds containing carbon (e.g. hydrocarbons) is
releasing CO 2 proportionally to the content of carbon in the compound. The effect
of combustion of some exemplary hydrocarbons is illustrated in Figure 2.4.5. Data
were obtained by the assumption that the calorific value of combusted hydrocarbon is
utilized by 40% for power generation. Generally, the larger the molar content of C in
combusted material, the smaller the energy per released amount of CO 2 . The smallest
value corresponds to pure carbon C. However, for example, pure hydrogen cannot be
shown in the diagram because the corresponding potential energy amount is infinity.
This should be emphasized that such infinity value corresponds also to utilization of
solar energy in production of power, heat or photosynthesis.

2.4.1.4 Canopy effect

The global warming effect often is compared to the effect of a greenhouse in which the
solar radiation is trapped at the Earth by using transparent canopy over the surface