Energy - Wind Energy: Renewable Energy and the Environment - page 16

energy than the energy needed to run the machine. A number of people have invested
money in such machines, but needless to say, the money was lost since the devices contra-
dict the first law of thermodynamics.
2. Thermal energy, heat, cannot be transformed totally into work. In laymen's terms, you can-
not even break even. In every transformation there is an energy efficiency that will be less
than 100%. So it takes energy to move heat from a cold place to a hot place (refrigerator,
heat pump for house in the winter time). Another way of looking at it is that systems tend
toward disorder, and in transformations of energy, disorder increases. In succinct terms,
entropy is increasing.

Therefore, some forms of energy are more useful than other forms. For example, the energy in
a liter of gasoline is not lost but only transformed into heat by a car. However, after the transforma-
tion, that energy is dispersed into a low-grade form (more entropy) and cannot be used to move the
car. So the efficiency from energy input to end product, energetics, needs to be calculated. Fuel cells
have a much higher efficiency than the internal combustion engine, so why aren't the highways filled
with cars powered by fuel cells.

2.4 ENERGY DILEMMA IN LIGHT OF THE LAWS OF THERMODYNAMICS
There is not an energy crisis, as energy cannot be created or destroyed, only transformed to another form.
We have an energy dilemma in the use of finite energy resources and their effect on the environment,
primarily due to the burning of fossil fuels. The first and primary objective of any energy policy must be
conservation and efficiency. It is the most economical form for alleviating our energy problems.

2.4.1 C ONSERVATION
Conservation means if you do not need it, do not turn it on or use it. Admonitions to reduce the
thermostat setting and reduce speed limits are conservation measures. High prices and shortages
of energy increase conservation; for example, in the California electrical crisis of 2000-2001, con-
sumption of electricity was reduced. In general, utility and energy companies like to sell more
electricity and energy rather than have customers reduce the use of energy.

2.4.2 E FFICIENCY
Efficiency is the measure of energy for the function or product divided by the energy input:

Eficiency (energy out)/(energy in) (2.5)

Energy can be used to do work (mechanical energy) or heat an object or space (thermal energy), can
be transformed to electrical energy, or can be stored as potential or chemical energy. In each trans-
formation, physical principles can determine an upper limit on efficiency. In thermal processes, the
temperatures of the hot and cold reservoirs determine this efficiency:

TT
T

(2.6)

Eff

H C

H

where T H and T C are the temperatures of the hot and cold reservoirs, respectively. Temperatures
must be in Kelvin, and the conversion is T K T C 273. Thermal electric power plants have effi-
ciencies of 35-40%. In other words, 40% is converted into electricity and 60% of the chemical (or
nuclear) energy is rejected as waste heat.