Virtual power plants pool energy from a broad variety of plant types and forward it to the distribution networks that are connected to them. To do this, they must be able to strike a balance between the over- and under-supply of power that occurs when renewable sources of energy are used. For this reason, most combined power plants are equipped with energy storage systems. These “giant batteries”, which Bosch is developing in cooperation with its industry partners, take excess energy from wind or solar parks, for instance, and either feed it into the grid or forward it to connected consumption points. Stationary energy storage systems can vary in capacity, from several hundred kilowatts to several megawatts. Depending on their size, they can supply a household, a company, or even entire communities with power. Cities account for 80 percent of global CO₂ emissions. In attempts to address the issue, several pilot projects have been initiated around the world in recent years that have tested sustainable living, energy, and mobility concepts for the city of the future. One of them is currently being carried out in the Austrian region of Rheintal, which comprises 29 communities. The “Smart City Rheintal” project has an ambitious goal: to make the region's energy supply CO₂-neutral by 2050 with the help of decentralized green energy power generation.