Environmental Engineering Reference
In-Depth Information
higher energy efficiency. This problem is very well described in the topic
Factor
Four
by Weizsäcker and Lovins:
In the next 50 years, twice the current global prosperity must be
achieved with half the energy and demand on natural resources
(Weizsäcker et al, 1998).
Renewable energies will be the key to this development, because they are the
only option that can cover the energy demand of Earth in a climatically
sustainable way.
Renewable energy sources
are energy resources that are inexhaustible
within the time horizon of humanity. Renewable types of energy can be
subdivided into three areas: solar energy, planetary energy and geothermal
energy. The respective available annual energy globally is:
•
solar energy
3,900,000,000 PJ/year
•
planetary energy (gravitation)
94,000 PJ/year
•
geothermal energy
996,000 PJ/year
Energy stored in wind or rain, which also can be technically exploited,
originate from natural energy conversions. The annual renewable energy
supply exceeds the global energy demand shown in the previous section on
evolution of world energy demand by several orders of magnitude. Renewable
energies can, theoretically, cover the global energy demand without any
problem. However, that does not mean that the transition from our present
energy supply to renewable energy supplies will be possible without any
problems. On the contrary, renewable energy supplies need a totally different
infrastructure compared to what has been created during the past decades.
The present energy supply depends mainly on fossil energy resources. The
priority is to produce and transport fossil fuels in the most economical fashion
and to convert them cheaply into other types of energy in central power
stations. The main advantage of fossil fuel-based energies is their ready
availability. Fossil energy can be used whenever there is consumer demand.
In contrast to fossil fuels, the availability of most renewable energy sources
fluctuates. A fully renewable energy supply must not only convert renewable
energy sources into useful energy types, such as electricity or heat, but must
also guarantee their availability. This can be done through large energy storage
systems, global energy transport or adaptation of the demand to the available
energy. It is not in question that renewable energies can cover our energy
demand; the open questions are what share the different renewable energy
sources will require for an optimal mix and when will they provide the entire
energy demand. In terms of global warming, the transformation of our energy
supply is the single most important challenge of the 21st century.
Geothermal energy
Geothermics utilizes the heat of Earth's interior. Geothermal power stations
can utilize geothermal heat and convert it into electricity or feed it into district
