Introduction and Structure - Renewable Energy: Technology, Economics and Environment - page 9

1.2.2 Investigated possibilities
Appropriate techniques permit the exploitation and conversion of different renew-
able energy flows or energy carriers into secondary or final energy, energy carri-
ers or useful energy, respectively. Currently, there are tremendous variations in
terms of utilisation methods, status of technology and given perspectives. More-
over, not all options are possible for every site and every set of boundary condi-
tions. Therefore only those opportunities that are most promising from the current
viewpoint will be investigated in more detail in the following. They include:
− solar heat provision by passive systems (i.e. architectural measures to use solar
energy),
− solar thermal heat provision by active systems (i.e. solar thermal collector sys-
tems),
− solar thermal electrical power provision (i.e. solar tower plants, solar farm
plants, Dish/Stirling and Dish/Brayton systems, solar chimney plants),
− photovoltaic conversion of solar radiation into electrical energy (i.e. photo-
voltaic systems),
− power generation by wind energy (i.e. wind turbines),
− power generation by hydropower to provide electrical energy (i.e. hydropower
plants),
− utilisation of ambient air and shallow geothermal energy for heat provision (i.e.
utilisation of low thermal heat by means of heat pumps),
− utilisation of deep geothermal energy resources for heat and/or power provision
(i.e. utilisation of the energy stored in deep porous-fractured reservoirs by
means of open and closed systems) and
− utilisation of photosynthetically fixed energy to provide heat, power and trans-
portation fuels (i.e. energy provision on the basis of biomass).
With the exception of biomass utilisation all of the possibilities of utilising renew-
able energies mentioned above will be outlined and discussed in detail in the fol-
lowing. In addition, within the scope of an excursus, selected options of harness-
ing ocean energy (such as tidal energy, ocean current energy) are addressed. Fur-
thermore, the possibilities of utilising biomass, and thus photo-synthetically fixed
energy, are outlined briefly as an overview in the annex; please refer to /1-4/ for a
more detailed and comprehensive description of utilising organic material for en-
ergetic purposes.
1.3 Structure and procedure
Due to the great variety of possibilities to use renewable energy sources with the
aim to fulfil the demand for end or useful energy, it is very difficult to present the
different possibilities in a similar manner. It is thus highly important to explain the