The Fachhochschule Wiesbaden has developed and operated two decentral energy-systems of hydrogen-technology where the hydrogen serves as storage-medium for solar and wind-energy. The principal economical results are described. It is evident that the hydrogen-price is too high for energy-technology. One of the reasons is the high storage-price for pressurized hydrogen. A price-reduction is possible if also the electrolytical oxygen is used, for instance in a waste-water purification plant. The storage problem can be solved if one lets react the hydrogen with carbon dioxide. The reaction product is methanol, a liquid energy-carrier for which exists the distribution infrastructure. The principles of this energy-technology (to store energy by reaction-products of hydrogen and carbon-dioxide) are known, because nature has applied it for millions of years in plants. But a lot of details have to be developed. The introduction of this new technology requires considerable efforts in the development of procedures, catalysts, apparatus, materials. There are many possibilities to solve the problem; the optimized one has to be found.