Siting and planning of solar energy projects needs precise data about the available solar resource. In most cases these data are not available in an adequate quality. Ground measurements are expensive and therefore the measurement network density is usually scarce.
Solar irradiance is the "fuel" of a solar power plant. Its availability is an important factor in the economy of solar power plants. High quality data is a prerequisite for the design of solar power systems. The data should be used to best fit the components to each other for reaching highest efficiency and calculating the economy of solar power use. It is a fundamental information to ensure optimal return of investment.
The satellite based resource assessment SOLEMI offers an alternative:
| SOLEMI | saves you costs. No expensive instruments have to be bought and no staff for the maintenance of a measurement station has to be hired in the phase of site selection. After acquiring measurement equipment can be placed directly at the most promising sites. |
| SOLEMI | saves you time as data are available in retrospect. Large areas and long time periods can be evaluated at once. You do not have to wait for time consuming from ground measurements. Preliminary planning and safeguarding of project prerequisites (e.g. land options) can start immediately. |
| SOLEMI | has a comprehensive temporal and spatial data base (up to 20 years for Meteosat Prime and 7 years for Meteosat East, it covers Europe, Africa, Eastern Brazil, West and South Asia with a temporal resolution of one hour and spatial resolution of up to 2.5 km). Potentials of whole regions can be analysed to evaluate synergies of multiple projects. |
| SOLEMI | data are very accurate. The high resolution allows the analysis of the exact location, no interpolation from far away measurements has to be done. The continuous long term data cover all year to year variabilities. |
| SOLEMI | data are comparable. A ranking of sites enhances planning flexibility. The spatial measurement of the satellite is more representative for a large solar plant than a single point measurement. All measurements are done with the same sensor. A ranking based on satellite data shows you the best available site without misleading measurement equipment errors. SOLEMI supports you to find the best site but not the most “optimistic” or best cleaned instrument. |
For long term measurements current satellite based methods already have comparable accuracy, accuracies are about 5% (root mean square deviation - rmsd) for yearly averages or sums.
Even for hourly global irradiance data satellite measurements reach the quality of a 25 km grid of ground stations. The next figure shows the results from two ground measurement networks in Switzerland and the northeastern US compared to satellite data :
RMS Error of hourly values of irradiance versus distance of ground measurement networks.
Source: Zelenka, A., Perez, R., Seals, R., Renne, D., 1999. Effective accuracy of satellite-derived hourly irradiances. Theoretical and Applied Climatology 62, 199-207.
The red bar shows the typical RMSE of hourly global satellite data vs. ground measurements. The dots show typical RMSE of hourly ground measurements vs ground stations x km away. Available ground measurement networks are less dense, especially in the solar belt.