Hannover, Germany

Project: act2

Renewable Energy Sources:

• Sun
• Solid Biomass

Low Carbon Technologies:

• Photovoltaics
• Solar Thermal Collectors
• District Heating
• CHP based on biomass
• Biomass Boiler
• Mechanical Ventilation and Heat Recovery

Technologymix implemented in this CONCERTO site:

In the residential scope two small district heating networks, each based on a 150 kW pellet boiler, have been installed. The public building “Burgweg Depot” and the “School Biology Centre” have also been equipped with a pellet boiler. Additionally the “Woodland School” had been connected to the boiler of “School Biology Centre” as the old gas-boiler had to be decommissioned. A Cemetery Chapel (30 kW) and a hibernation greenhouse (600 kW) have been equipped with a wood pellet boiler.
A photovoltaic system has been mounted on the storage building at Herrenhausen power station and produced 70 MWh of electricity in 2011. At a public open air swimming pool solar collectors with an absorber area of 1,800 m² (600 kWpeak) have been installed.
At Vahrenwald and Ahlem altogether 305 apartments (originating from 1950 – 1970) have been retrofitted to meet the energy standard for new buildings. At Kronsberg another 35 apartments (built in 1956) were retrofitted with innovative Passive House components to reduce end energy use for heating to 55 kWh/m² a. The “Brüder Grimm” primary school (5,356 m²) has been retrofitted to reduce heating demand by 50% (Picture 1). A PV-plant of 83 kWpeak has been installed on its roof. The “Cultural Centre Hainholz” (2,157 m²) and secondary school “Luther School Nordstadt” have been modernized by energy efficient measures.
The coal fuelled CHP (combined heat and power) plant, which supplies a large existing district heating network, is now partly based on wooden biomass. 1,400 MWh of heat, now produced by renewable energy sources, cover the energy demand of the act2 ecobuildings.
In 2007 the “Wood Energy Centre” was commissioned. On the site of the Hannover-Stöcken power station a modern splitting logs plant is operated (Picture 2), which directly uses surplus heat from the power station to dry the wood. The local ESCO „Stadtwerke Hannover“ sells wood products for various types of wood burners: pellets, chips, split logs and wood briquettes.

Picture 1 – Retrofitted “Brüder Grimm” School

Picture 2 -  Log splitting plant