Environmental Engineering Reference
In-Depth Information
Chapter 1
Energy, Climate Change and
Renewable Energy Sources
T
HE
E
XPRESSION
'E
NERGY
'
The expression 'energy' is often used without a great deal of thought and is
applied to very different contexts. In this textbook - which only deals with
technically usable types of energy, especially renewables - the physical laws
describing the utilization of the energy resources will be investigated. Power is
inseparably linked with energy. Since many people mix up energy, work and
power, the first part of this chapter will point out differences between these
and related quantities.
In general, energy is the ability of a system to cause exterior impacts, for
instance a force across a distance. Input or output of work changes the energy
content of a body. Energy exists in many different forms such as:
•
mechanical energy
•
potential energy
•
kinetic energy
•
thermal energy
•
magnetic energy
•
electrical energy
•
radiation energy
•
nuclear energy
•
chemical energy.
According to the definition above, a litre or gallon of petrol is a potential
source of energy. Petrol burned in an internal combustion engine moves a car
of a given mass. The motion of the car is a type of work. Heat is another form
of energy. This can be seen when observing a mobile turning in the hot air
ascending from a burning candle. This motion clearly demonstrates the
existing force. Wind contains energy that is able to move the blades of a rotor.
Similarly, sunlight can be converted to heat, thus light is another form of
energy.
The
power
:
d
W
d
t
P
=
=
(1.1)
W
