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Factsheet                                                                                             Berlin, 24.05.2004

Solar energy: Immense potential

                    Technology                                   continue to grow dynamically in the future, but is
                                                                 not expected to contribute one percent to total
Solar energy in the stricter sense1 can be used in               power production before the year 2020 (Nitsch
three ways:                                                      and Staiß 2002).
    Solar thermal collectors use the solar                      Nonetheless, in sparsely populated off-grid areas
     radiation falling on them to heat tap water                 photovoltaic supply is often more cost-effective
     (and, to a lesser extent, to heat water for                 than a connection to the power grid.
     space heating).                                             Consequently, photovoltaics can contribute
    Photovoltaic modules convert solar radiation                substantially to improving quality of life and
     directly into electricity.                                  promoting sustainable development, particularly
    Solar thermal power plants use solar heat by                in rural areas of developing countries (Witzel /
     concentrating solar radiation (for instance                 Seifried 2004).
     using mirrors focussed upon a “solar power
     tower”, or by means of parabolic troughs) and               Solar heat
     then conveying the energy of the medium                     The potential of solar heat is also huge. In the 15
     thus heated to a turbine or to a Stirling                   “old” European Union member states alone (prior
     engine.                                                     to enlargement in 2004), the solar thermal industry
                                                                 anticipates a potential totalling one billion square
    Progress and potential worldwide                             metres (Intersolar 2004).
                                                                 Barcelona, the capital city of Catalonia, has shown
Photovoltaics                                                    how this potential can be tapped. In 2000 the city
Theoretically, the entire present energy                         adopted a regulation prescribing the installation of
consumption of the world could be met by an area                 solar thermal systems when new buildings are
of 700 km * 700 km covered in photovoltaic cells.                constructed. As a result, the overall installed area
Economic aspects are the main obstacle to tapping                of solar collectors has grown about tenfold, from
this potential. The photovoltaic contribution to                 1,650 to 15,677 square metres. The municipality
power generation is still small compared to that of              of Vellmar in Germany is pursuing a similar path.
other renewable technologies. Despite strong                     The solar contract concluded between the local
growth in recent years, the worldwide contribution               administration and each property developer
is still well below 0.01%. The sector is forecast to             stipulates the installation of a solar system, but at
                                                                 the same time promotes energy-efficient
                                                                 construction by providing that the local authority
  The sun also drives our climate – wind, clouds and             carries the costs of energy consultancy (Intersolar
thus also rain are a result of solar irradiance. Similarly,      2004).
sunshine is essential to biomass. This is why wind
energy, hydropower and biomass are included under the            It is in Israel that the strongest efforts are being
concept of solar energy in a wider sense.                        made to harness solar energy for water heating:

WWF Germany is one of the national organizations of WWF – World Wide Fund For Nature – in Gland (Switzerland).
                                                       24.05.04 . Solar energy

With a newly installed collector area of 67 square     plants for seawater desalination, thus easing the
metres per 1000 inhabitants in 1999, the country       mounting scarcity of freshwater in the region.
leads the field worldwide by a long margin. This is
due to the construction laws in force: Since as          Progress and potential in Germany
long ago as 1980, installation of a solar thermal
system is mandatory for all newly constructed          Solar heat
residential buildings, hotels and public facilities    By the end of 2003, a total of 5.5 million m²
(Staiß 2003).                                          collector area had been installed in Germany. New
                                                       collectors installed in that year totalled about
Solar thermal power plants                             840,000 m² (BMU 2004b). These collectors are
Power generation in solar thermal power plants         used mainly to heat tap water. Only 20 percent of
requires high levels of direct solar radiation, as     them also support space heating. Overall this
only this can be concentrated optically. This          corresponds to about 250 million litres of
necessitates a high number of sunshine hours as        prevented heating oil consumption (BMU 2004a).
well as solar irradiance that is only rarely reduced   Roof areas are the mounting sites most suitable for
by clouds or haze. Such conditions prevail in          the future expansion of solar thermal collector
warmer climate zones. Consequently areas such as       systems. With due consideration to the
the southern Mediterranean region are particularly     competition for roof areas with photovoltaic
suited to this technology.                             systems, about 970 km² (= 970 million m²) are
The annual solar power output of such plants           available for solar thermal systems in Germany.
amounts to about 200-300 GWh/km² land area.            The rate at which these areas are developed
Theoretically, a covered area of about 45 km x 45      depends upon various factors, such as public-
km (corresponding to 0.03% of the suitable areas       sector support for solar thermal energy, the way in
in North Africa) could meet the entire electricity     which prices of other energy carriers develop, the
requirement of Germany (BMU 2004). Attention           way in which costs for solar thermal systems
is thus now focussing on how the potential in          develop, and the development of storage
countries south of Europe can be used for Europe.      technologies. The public-sector promotion policies
The interconnected European grid would need to         currently in place and the volume of applications
be reinforced, and the solar power plants would        for such promotion already made indicate high
need to be connected to this grid by high-voltage      growth rates, at least in the current year (Intersolar
lines.                                                 2004).
Under the precondition of dynamic market take-up       It is feasible to push collector area in Germany to
of solar thermal power plants, Germany might be        273 million m² by 2050 (BMU 2004a). This could
able to use imported solar power by the year 2020.     save fossil energies totalling about 78 TWh/a.
Overall costs, including transmission costs, are
expected to run to about 0.10 Euro/kWh (BMU            Photovoltaics
2004a).                                                The photovoltaic market has been highly dynamic
Both Europe and North Africa could profit from         over the past two decades. By late 2003,
the construction of such power plants. Europe          photovoltaic systems installed in Germany had a
could tap cost-effective renewable energy sources,     total capacity of about 400 MW (BMU 2004b).
which would also make it easier to meet its            The solar power produced by these corresponds
climate protection commitments. North Africa           roughly to the consumption of 100,000
could profit from the export of solar power, while     households.
at the same time using the waste heat of the power

                                                       24.05.04 . Solar energy

This total installed capacity makes Germany the        BMU (2002): Erneuerbare Energien und Nachhaltige
second largest market for photovoltaic systems
after Japan. About 70% of the photovoltaic             BMU (Ed.) (2004a): Ökologisch optimierter Ausbau
                                                       der Nutzung erneuerbarer Energien in Deutschland,
capacity installed in Europe is in Germany.            Forschungsvorhaben          im       Auftrag      des
Development in this sector can be expected to          Bundesministeriums für Umwelt, Naturschutz und
continue to be dynamic, notably within the context     Reaktorsicherheit. Auftragnehmer: Deutsches Zentrum
of the amended German Renewable Energy Act,            für Luft- und Raumfahrt (DLR); Institut für Energie-
                                                       und Umweltforschung (ifeu); Wuppertal Institut für
which guarantees since April 2004 higher               Klima, Umwelt und Energie
payments for power fed into the grid than in           BMU (2004b): Entwicklung der erneuerbaren Energien
previous years.                                        in Deutschland. Erste vorläufige Abschätzung. Stand
The technical potential of photovoltaic systems is     Februar 2004
determined by the solar radiation falling on the       Intersolar (2004), Beilage zu Neue Energie 5/2004
module area, the available areas, and the              Nitsch and Staiß (2002): Strategies for Introducing
efficiency with which systems convert solar            Renewable Energies and the Contribution of
                                                       Photovoltaics. In: A. Bubenzer, J. Luther (Eds.):
radiation into electricity. Presupposing practicable   Photovoltaics Guidebook for Decision Makers.
and economically viable integration of                 Staiß (2003): Jahrbuch Erneuerbare Energien 02/03
photovoltaic systems into existing settlement
structures, i.e. the use of roof areas, facades,
                                                       Further information:
coverings, noise barriers etc., and giving due
regard to competing uses of areas for thermal          Claudia Kunz, WWF – Climate Protection and
collectors for hot water and space heating, the        Energy Policy Division, Tel.: +49-30/308742-
available module area in Germany totals about          17, Fax: -50, mailto:
700 km² (BMU 2004a).
This delivers a power generation potential of 105      Regine Günther, WWF – Head of Climate
TWh/a, corresponding roughly to one fifth of           Protection and Energy Policy Division, Tel.:
today’s total power consumption. This does not         +49-30-308742-18, Fax: -50, mailto:
take into consideration any use of open spaces for
photovoltaic power generation, which is quite
                                                       This factsheet is available, together with further
feasible in principle.                                 background information, at


Today, direct solar energy use only makes a small
contribution to overall electricity and heat
requirements. Nonetheless, both photovoltaics and
solar thermal energy hold out a great utilizable
potential. These are definitely technologies for the
future, whose development and cost-reduction
potential should be tapped systematically.