Power Generation Using District Heat: Energy Efficient Retrofitted Plus-energy School Rostock

Abstract

The Mathias-Thesen-School in Rostock/Germany is one of few schools which has been retrofitted as an Energy Plus building as part of the energy-efficient school research project “EnEff:Schule” sponsored by the German Ministry of Economics and Technology. The original building complex (build 1960, useful area 2200sqm) is being converted into a compact building by extending the main building with two new buildings connected by light-flooded buffer spaces. Both the existing building and the new buildings will be highly insulated. The low remaining heating demand will be covered using an innovative concept, made reasonable by the low primary energy factor of the district heat in Rostock: A small-scale Organic Rankine Cycle system generates electricity using high-temperature district heat. The excess heat of the generator is then used to heat the building via low-temperature distribution systems. In combination with two small-scale onsite wind turbines and building integrated photovoltaics a positive primary energy balance is achieved. For this balance, the development of the primary energy factors (PEF) of the German electricity mix is crucial: With rising generation from renewable energies the PEF of electricity in Germany is going to descent, leading to higher primary energy factors of cogeneration systems. In the Mathias-Thesen-School in Rostock a detailed monitoring system was installed, which has been checked and reworked for proper functioning. First measures to optimize the HVAC system and user comfort have been taken. The second construction phase will take place in 2014, after which the performance of the ORC system and the Energy Balance will be analyzed in detail.