Introduction and Structure - Renewable Energy: Technology, Economics and Environment - page 7

550

500

Biomass

450

Hydropower

400

Nuclear power

350

Coal

300

250

Natural gas

200

150

100

Crude oil

50

0

65 69 73 77 81 85 89 93 97 01 05

Time in years

Fig. 1.4. Worldwide consumption of fossil primary energy carriers, hydropower and bio-
mass according to energy carriers (for data also refer among others to /1-3/)

1.2 Applications of renewable energies

Provision of final or useful energy using renewable energies is based on energy
flows originated by the movement and gravitation of planets (i.e. tidal energy),
heat stored and released by the earth (i.e. geothermal energy) and in particular en-
ergy radiated by the sun (i.e. solar radiation) (Chapter 2.1). There is thus a great
variety of renewable energies in terms of energy density, variations of the avail-
able forms of energy and the related secondary or final energy carriers and final
energy to be provided. Each technical option for utilizing the described renewable
energy flows or carriers must be adapted to the corresponding characteristics of
the available renewable energy; there is thus a broad range of current and also fu-
ture technical processes and methods to exploit the renewable energy options
most successfully.
In the following, the different renewable energy sources are classified. Subse-
quently it will be discussed which energy utilisation options will be analysed more
in detail throughout this topic.

1.2.1 Renewable energies

The three sources of renewable energies give rise to a multitude of very different
energy flows and carriers due to various energy conversion processes occurring in