Principles of Solar Engineering 3rd Edition by Dr. Yogi Goswami

Introduction to Solar Energy Conversion
A thing that will assume enormous importance quite soon is the exhaustion
of our fuel resources. Coal and oil have been accumulating in the
earth over five hundred million years, and at the present rates of demand
for mechanical power, the estimates are that oil will be all gone in about
a century, and coal probably in a good deal less than five hundred
years. For the present purpose, it does not matter if these are under-estimates;
they could be doubled or trebled and still not affect the argument.
Mechanical power comes from our reserves of energy, and we are
squandering our energy capital quite recklessly. It will very soon be all
gone, and in the long run we shall have to live from year to year on our
earnings (Darwin 1953).
Charles Galton Darwin
(grandson of Charles Darwin)

The only energy earnings or income we have is the direct radiative energy
from the sun (Daniels 1964). Fossil fuels are the stored form of the sun’s
energy, representing our energy savings or energy capital. In addition, we
have the indirect forms of solar energy (wind, biomass, ocean, and hydro),
geothermal energy, and nuclear energy in radioactive materials. It is clear
that we have been using the energy capital at unsustainable rates over the last
100 years while throwing away our energy earnings, the direct energy from
the sun. However, there is concerted effort throughout the world to change
it. As we move toward a future where solar energy will play a far greater
role, education of students in the science and engineering of solar energy has
become extremely important and urgent. This book fills that need.
This book assumes that the reader is familiar with traditional thermodynamics,
basic heat transfer, and fluid mechanics and has knowledge of calculus
and ordinary differential equations. Some elements of radiation, fluid
mechanics, and heat transfer specific to solar engineering are presented in
the text. The design and analysis of solar utilization schemes are approached
from a systems-analysis viewpoint, which combines technical design with
economic analysis. There is no single solution to a given task in solar energy
utilization and each problem must be analyzed separately from fundamental
principles.