At the beginning of the 1970s, the Club of Rome’s Limits to Growth raised awareness about the idea that exponential growth on Earth is not possible in the long term. It also stated that crude oil reserves would be depleted in 30 years under a specific set of assumptions. Today, oil reserves are reported to […]

Solar collectors can heat up to around 80°C. But much higher temperatures can be reached when sunlight is concentrated. This concentrated heat can then boil water and steam can be used to drive a turbine to generate electricity. In such cases, one speaks of solar thermal power plants or concentrated solar power (CSP). In CSP […]

Under German law, electricity from biogas units receives special compensation (feed-in tariff). If a biogas unit is then run as a cogen­eration unit, the generator’s waste heat can then not only be used to heat the fermenter, but also to provide space heat. The power generated can be used internally or exported to the grid. […]

7.1 Water power – the largest source of renewable energy Solar energy keeps water circulating on the Earth. Worldwide, more than 50 billion cubic metres of water evaporates each hour, most of it over the oceans. When this water falls onto land as precipitation, the difference in altitude between the land and sea level provides […]

A look at the various EU member states reveals considerable differences in the use of renewables, mainly as the result of different geography. For example, countries with tall mountains have much more hydropower potential than flat countries. It therefore comes as no surprise that Austria (65 per cent) and Sweden (44 per cent) get a […]

A solar strategy restricted to user-owned property does not go far enough. Most multi-family dwellings and rental complexes would remain unaffected. Yet, such build­ings offer tremendous potential for inexpensive solar heat. On the one hand, large collector areas reduce the cost per kilo­watt-hour; on the other, the large number of users means there is always […]

Financing is not the only obstacle towards renewables. For instance, a lot of people have the money but don’t have a good roof: • Roughly half of Germans do not own their own homes. • Just under 20 per cent of the rest live in apartments with shared roof space, and PV arrays generally cannot […]

Though Germany is sometimes touted as a global leader in renewables, the country imported 59 per cent of its primary energy consumption as oil or gas in 2005. And even when it comes to nuclear energy (12.5 per cent of primary energy consumption) and hard coal (12.9 per cent), Germany is hardly independent; 100 per […]