Wind energy

Offshore windfarm

Selecting the optimal location for windfarms is very important. Christof Stork of UK-based Garrad Hassan told the Frascati workshop how satellite data on land use, surface topography and roughness could improve the accuracy of regional wind atlases currently used to site land-based windfarms.

Offshore windfarms are more productive and most future farms are likely to be built in the coastal ocean due to the saturation of land-based sites. To be viable, offshore developments have to generate at least 200 MW, and to build on such a scale costs at least €300 million.

The problem is there is hardly any offshore wind data available to industry. Furthermore, existing data record mainly extreme wind events. And to gather in-situ data from a single offshore meteorological mast can cost a million Euros a year, and provides data only for a small area.

But using satellites enables a shift from a local to a global view. The sophisticated Synthetic Aperture Radar (SAR) instruments on board ESA’s ERS-2 and Envisat can provide high-resolution 100-metre data on the wind field, and a decade-long data archive is available.

Other space-borne instruments could come into play through the cycle of wind turbine planning, construction and maintenance. Optical sensors such as Envisat’s Medium Resolution Imaging Spectrometer (MERIS) could be used to carry out environmental impact assessments. And satellite images could also be used for marine traffic management during initial construction and later repair work, as well as for daily energy production forecasting.

Hydropower

Hydropower is the leading renewable energy source

Currently supplying around one fifth of the world’s energy needs, hydropower is a pollution-free power source that requires only the flow of water to spin a turbine. Accurate quantification of how much water will flow from a given region at any one time is extremely useful for optimising hydroelectric power production, deciding dam levels and setting electricity prices.

In Norway for instance – where hydropower supplies almost all the country’s energy needs – around half of all winter precipitation accumulates on the ground throughout the winter as snow. By measuring snow coverage and thickness, then combining this information with meteorological data such as ground temperature, run-off can be accurately modelled and predicted.

Optical EO data is already used to monitor snow coverage, together with ground observation. The operational use of optical data remains however severely limited by the presence of clouds. But radar instruments such as those aboard ERS-2 and Envisat have the potential to greatly supplement the amount of snow data gathered, because they can see right through clouds.

Anders Rognes of the Norwegian Computing Center told the Frascati workshop how they have worked with Statkraft, a major Scandinavian hydropower company, to prepare a snow reservoir mapping system called SnowStar. The SnowStar server automatically processes satellite information of several different systems, including radar imagery, for display within geographic information system (GIS) software.

The next step

ERS SAR image of Danish windfarm

Representing a first in the EO field, the Invitation to Tender issued by ESA this month is open to applications until 5 September 2003. The hope is that pilot services to the renewables sector can be developed, then grow to become self-sustaining.

“The ESA gathering was very useful in getting service providers and potential service users together,” said workshop participant Marion Schroedter-Homscheidt of the German Aerospace Centre DLR. “Now the Invitation to Tender gives both sides the opportunity to turn the ideas we discussed into reality.”