Today accurate and continent-wide scale measurements of ground radiances
are provided every 15 minutes by the European Space Agency's Meteosat
Second Generation satellite. Integrating this information with the
business practices of solar energy managers is the objective of the
ENVISOLAR project (Environmental Information Services for Solar Energy
Industries), funded by ESA within the framework of the Earth Observation
Market Development Programme (EOMD).
In both photovoltaic and solar thermal applications, precise, long-term
irradiance data is needed for choosing plant locations and estimates of
likely energy yield for prospective investors. Then once a plant is built,
managers need data updated in near real-time to check the facility is
working optimally, and energy output tallies with available sunshine.
"Today our audits form the basis of huge investments in the range of 50
million euros for single projects," said Gerd Heilscher from Meteocontrol,
a company auditing photovoltaic systems and involved in ENVISOLAR.
"Besides the layout, solar radiation is the most important issue. But
unfortunately only a few high-quality ground-based measurements are
available at this time."
Within the wider energy market, such information is also valuable for
forecasting electricity load - irradiance is the other major environmental
influence on demand besides temperature.
How best to measure sunlight? Ground radiance is quite complex to quantify
as it is influenced by much more than simply a site's distance from the
equator. Variations in cloud cover, humidity, aerosols and ozone in the
air determine the amount of incoming solar radiation actually reaching the
ground. Local topography is also important and there are large regional
differences - in Europe the southern side of the Alps receives twice the
annual radiance of northern slopes.
Measuring from below using in-situ data is technically demanding,
expensive on an ongoing basis and limited in coverage - there are only
around 200 solar-energy-measuring stations to cover all of Europe and
Africa in the official networks affiliated to the World Meteorological
Organisation (WMO).
Measuring from above using satellites provides a wide-area, objective and
cost-effective solution. Research by MeteoSwiss has shown that satellites
are even more accurate than ground measurements once the distance to the
next ground station is greater than about 30 kilometres.
Today, ENVISOLAR partners are developing and marketing a variety of solar
services based on satellite radiance data. These services benefit from the
latest scientific results and state-of-the-art algorithms developed by a
EU Research & Development project called Heliosat-3.
ENVISOLAR services based on these data products comprise solar plant yield
estimates, plant fault detection and performance checking, energy
forecasting for energy utilities, and time series services including maps
and statistics of irradiance, its direct and diffuse components and
spectral components such as illumination.
Customers of ENVISOLAR services include SAG Solarstrom AG, a publicly
traded German firm that builds and operates photovoltaic installations,
providing entire financial investments in photovoltaics to its customers.
"We need solid information for investment decisions, especially with
regard to future markets like Spain," said Uwe Ilgeman, CEO of SAG
Solarstrom AG. "The sampling and spatial resolution of ground-based data
is too coarse - for example in Spain there are only 30 sites available at
the moment."
High-resolution radiance data from the Solar Energy Mining (Solemi)
service operated by the German Aerospace Centre (DLR) - leader of
ENVISOLAR - have contributed to the quantification of the renewable energy
potential within 14 developing countries, in the framework of the SWERA
project of UNEP. Results of SWERA suggest the potential is far greater
than has previously been supposed.
"These countries need greatly expanded energy services to help them in the
fight against poverty and to power sustainable development," said Klaus
Toepfer, Executive Director of UNEP. "SWERA offers them the technical and
policy assistance to capture the potential that renewable energy can
offer."