New “Neckarpark Stuttgart” urban district: Local heating and cooling energy from waste water
|Location of network||Derelict land belonging to the former Bad Cannstatt railway freight depot (mixed area): Approx. 22-ha site area; 170,000 m² NFA, of which approx. 70,000 m² is earmarked for residential use|
|Location of local community||Landeshauptstadt Stuttgart, 70173 Stuttgart, Baden-Württemberg|
|Settlement in figures||207 km²; 590,000 residents|
|Developer, organizer||State capital of Stuttgart|
|Heating system||Local heating network (waste heat from waste water / waste water heat)|
The state capital of Stuttgart has more than 35 years of experience in managing the energy requirements of its municipal properties under the direct influence of local communities. The energy management has significantly reduced the energy consumption in the municipal buildings. Energy guidelines were developed for the energy-related operation and planning. The proportion of renewable energies for supplying the buildings has been continually increased. A municipal contracting model helps to implement measures for increasing the energy efficiency.
A particular focus in recent years has been on energy research. A series of projects has enabled the energy consumption of existing buildings to be considerably reduced (primary energy reduction of up to 70%). These refurbished pilot schemes act as demonstration buildings for planners, building users and owners. The knowledge garnered from the projects is also transferred to other schemes and the city’s energy requirements are correspondingly updated.
In addition to municipal properties, increased requirements for structural thermal protection (currently 30% according to EnEV 2009) are specified and contractually stipulated with new-build schemes within the entire municipal area to the extent that developers are required to conclude contracts with the City. A municipal energy saving programme has triggered investments totalling more than 200 million euros, particularly in the local professional trades. Private developers in the residential sector are provided with impartial and cheap information through Energieberatungszentrum Stuttgart e.V. (EBZ) founded in 1999. Its range of services includes information events, energy diagnoses and the so-called Stuttgart Refurbishment Standard.
As a member of the European Covenant of Mayors, the City of Stuttgart is developing an energy action plan in order to achieve a 20% increase in energy savings, energy productivity and the use of renewable energies by 2020 relative to 1990. The main aim is to achieve sustainable, efficient energy provision for specific buildings, at the district level, and for all of Stuttgart.
In terms of the project, the energy efficient design of the Burgholzhof housing estate should be highlighted, which was developed in the 1990s on sites earmarked for redevelopment. Here the developers were required to construct low-energy houses and connect them to a solar-powered local heating network.
One of the most important development areas in Stuttgart is the 22-hectare former railway freight depot in Stuttgart-Bad Cannstatt. The Deutsche Bahn rail company used the site until the end of the 1980s. The City of Stuttgart bought the site in 2001. In 2009 the City adopted the “Neckarpark” urban framework plan, which envisages the construction of 450 apartments and the establishment of service providers and commercial enterprises on the site.
The “Neckarpark Stuttgart” project
The Neckarpark is being realised with buildings which, owing to the high quality specification for the building envelope and the technical equipment, only have a low energy requirement and are therefore considerably more energy productive than the provisions of EnEV 2009 (KfW Efficiency House 55). Waste heat from a nearby large sewage channel provides a possibility for supplying heat. Even with a high structural density, this concept will only produce a small thermal density. Traditional district heating with high supply temperatures and corresponding pipe losses often prove to be inefficient and uneconomic for supplying heat to such nearly zero-energy areas. There was a danger that inefficient individual heating systems based on biomass or air-air heat pumps and electrical compression chillers could be predominantly used for heating and cooling the buildings. In terms of environmentally friendliness and the energy productiveness, such an approach would only enable a sub-optimum overall system to be achieved for heating the buildings.
The planned project is intended to help furnish the Neckarpark with a future-oriented, integrated energy concept which, in addition to energy-optimised new build schemes, also contains an innovative new local heating network that is designed to ensure a high degree of low-exergy use and the use of locally available energy fuels. The core element is the exemplary, monovalent supply of heat from municipal waste water. The waste water also enables a thermal discharge and thus the generation of cooling energy.
The conceptual approach
The development of the Neckarpark as a near-zero energy area enables the supply temperatures for the planned heating network to be considerably reduced (30 °C or less). This in turn enables large-scale use of waste water heat. The hot water provision (65 °C) can be provided using a cascaded heat pump operation. The heat will be extracted from a nearby sewage channel and distributed via a low-temperature local heating network. Different heat exchanger systems are planned for using the waste water heat: channel-integrated and as a bypass. Photovoltaics shall be used to meet the required auxiliary energy.
In combination with near-zero energy buildings and low-exergy provision with renewable energy, it is intended to achieve an optimal overall system for supplying heat to buildings that is also ecologically and economically sustainable since it can exist independently of fossil fuels and markets. The results can also be used for the extensive expansion of district and local heating in areas with low thermal densities.
The project has been costed at 7.6 million euros, of which 5.8 million euros are being spent on construction-related investments and 1.5 million euros on planning services. The German Federal Ministry of Economics and Technology (EnEff:Wärme) is funding half the costs of the R&D project (3.8 million euros).
The energy concept is being further developed in an interdisciplinary manner until it is ready for execution and will then be implemented on a step-by-step basis. As part of the integrated planning, it will be necessary to select technologically suitable components and develop a viable operating concept.
Developers and investors in the district are being particularly encouraged to implement innovations and findings from the German Federal Ministry of Economics and Technology’s “Energy-efficient city” (EnEff:Stadt) and “Energy–optimised construction” (EnOB) research initiatives.
|Area with energy requirement (NFA)||170.000,00||m²|
|Primary energy ratio/factor for heating||0,60||0|
|Extraction capacity for waste water heat||2.100,00||kW|
|Calculated overall costs||7,60||Mio. Euro|
|Construction-related investments||5,80||Mio. Euro|
|Planning services||1,50||Mio. Euro|