TY - SER AU - Mangold, Dirk TI - Solar in the city: active solar heating systems for urban areas KW - ACTIVE SOLAR HEATING SYSTEMS KW - URBAN AREAS KW - CENTRAL SOLAR KW - HEATING PLANTS KW - GERMANY KW - PILOT PLANTS KW - SOLAR ENERGY N1 - Central solar heating plants present one way of utilizing solar thermal energy in the urban environmental; Germany has seen several pilot plants built ER -