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Integrated district energy concept for Ludwigsburg Grünbühl/Sonnenberg

EnEff:Stadt - Forschung für die energieeffiziente Stadt

Heat requirement simulation with a 3D urban model

© HfT Stuttgart

Settlement summary

Project status Projektstatus: Phase 1Concept
Location of local community 71638 Ludwigsburg, Baden-Württemberg
Settlement in figures Area: 43.35 km², inhabitants: Approx. 88,000
Developer, organizer Hochschule für Technik Stuttgart, City of Ludwigsburg, Ludwigsburg-Kornwestheim municipal utility company
Settlement New-build schemes comprising apartment buildings and single-family homes as well as existing medium-density terraced houses and a high-rise residential building
Utilisation type Predominantly general residential accommodation supplemented with communal uses and occasional commercial use
Estate size 38 ha
Gross floor area, before (according to DIN 277) 48.824 m²
Living area in Sonnenberg, before 12.793 m²
Living area in Grünbühl, before 29.876 m²
Total living area, before 42.669 m²
Commercial area in Sonnenberg, before 0 m²
Commercial area in Grünbühl, before 2.002 m²
Total commercial area, before 2.002 m²
Communal area in Sonnenberg, before 927 m²
Communal area in Grünbühl, before 3.226m²
Total communal area, before 4.153m²
Age structure Existing building stock mostly from 1949-1968 (50 buildings) and new-build schemes (recently built or under construction – approx. 87 buildings)
State of construction and refurbishment Post-war buildings urgently require refurbishment
Heating system Sonnenberg: Heat supplied via local heating network (geothermal), Grünbühl: Decentralised provision via individual stoves or central heating systems
Ownership structure Predominantly rental accommodation provided by local authority and private housing associations; New-build schemes: Predominantly own use
Project themes

Project description

As part of the project, an innovative local heating concept, exemplary energy-based refurbishment projects and an energy-optimised new-build standard were investigated and implemented. By jointly investigating both a new-build area and an existing district, synergies are created that enable the post-war housing estate in need of refurbishment to benefit from the innovative measures in the new-build area. Several studies on potential implementation projects for the upcoming project phases have been conducted.

The envisaged individual projects provide central components in the rebuilding and new construction to create a social energy-plus district. A new local heating network is being constructed to supply Sonnenberg with heating. The base load heat is generated with brine-water heat pumps. The innovative aspect is the use of geothermal energy, the combination of heat pumps and cogeneration as well as the incorporation of solar thermal energy. The aim of the project is to develop technically innovative measures involving local heating and LowEx technology approaches for new-build schemes and refurbished existing buildings. The work concerns a diverse variety of building types that will be defined in the concept phase in terms of the technology and costs.


For many years now, the City of Ludwigsburg has been engaging with issues concerned with energy and climate protection in a diverse number of ways. The basis here is provided by the urban development concept “Opportunities for Ludwigsburg”, which provides guiding principles and goals for eleven aspects concerned with sustainable urban development. The aspects are continually updated as part of the integrated sustainability management. Their implementation is supported by the “Sustainable Urban Development Department”, which as an interdisciplinary unit bundles the sustainable urban development tasks, deals with them in a process-oriented manner and links them with all administrative activities. Based on this, a communal energy and climate protection concept has been developed, which is currently being implemented in the form of numerous individual projects.

In the past, Ludwigsburg has successfully taken part in various energy and climate projects, including the EU projects “Managing Urban Europe 25” (6th Framework Programme) and “Snowball” (Intelligent Energy Europe programme). Ludwigsburg was also conferred the European Energy Award in January 2011. Ludwigsburg is currently participating in the EU’s “Living Green” (INTERREG IV B programme), EnSURE (INTERREG IVB Central Europe) and “Sustainable Now” (Intelligent Energy Europe programme) projects. As part of the Baden-Württemberg sustainability strategy, a model project for achieving more energy efficiency in commercial enterprises is currently being conducted.

Existing buildings

The Grünbühl and Sonnenberg housing estates are situated on the south-eastern edge of Ludwigsburg. In terms of transport they are well connected to the city centre and also have direct access to the open countryside. This means that both districts provide potential as attractive residential areas within the city. As a result of their own historic development, both housing estates have a very different character.

Sonnenberg was created in the 1950s and ’60s as residential complex for US army officers and covers a total area of around 15 hectares. The US army relinquished the site in 1991. The focus here was on demolishing the existing building stock and replacing it with new buildings. The housing estate is currently being enlarged population-wise, whereby it is intended to implement a passive house standard with energy-plus ambitions for Sonnenberg Southwest. To supply heating to Sonnenberg, a new local heating network is being constructed that is provided with heat via a central CHP plant. The house connections have already been prepared for the planned new buildings. For buildings being newly constructed, a compulsory connection requirement has been specified for the local heating network.

The Grünbühl urban district exemplifies the structural and energy-based refurbishment requirements for buildings from the 1950s to the 1970s, including in regard to issues relating to further urban development, socio-economic compatibility and demographic change. The district was created during the middle of the 1930s as a military base and was later converted to a prisoner-of-war camp. After the Second World War, further buildings were constructed in the district for displaced people and German immigrants. Today, the existing buildings in Grünbühl have low energy standards and in some cases are in serious need of refurbishment. Grünbühl currently has 2,350 residents across an area of approximately 23.6 hectares. It is planned to connect Grünbühl to the existing local heating network.

Scope of the project

As part of the conception phase, an integrated energy district concept is being developed that takes into account energy-related, socio-economic and urban design issues and requirements to an equal extent. Following an application by the Ludwigsburg local authority in 2006, the housing estates have been included in the joint federal and state government programme, “Socially Integrative City”, for urban districts with particular redevelopment requirements. In addition to innovative energy-based solutions, this is why socio-economic issues also play a substantial role in the concept development. On the one hand, the major urban redevelopment offers an opportunity to stabilise the existing social structure through the targeted settlement of new residential groups and to generate ownership. On the other hand, the provision of a differentiated range of homes should prevent segregation tendencies. For this purpose a socio-economic assessment is being conducted and a district marketing concept developed. The results provide the basis for the implementation strategy in the second phase from 2013.

Project aims
  • Development and implementation of system-integrated measures for the efficient management of the urban development area
  • Specification of the infrastructure for linking the supply and demand (monitoring system, intelligent meters for recording data and remote access, power electronics for the grid integration, electrical/thermal storage system, etc.)
  • Analysis of the supply and demand structure and optimisation of the temporal and spatial matching of the supply and demand
  • Development of optimisation strategies in power plant, building and energy management systems (EMS)
  • By jointly investigating both a new-build area and an existing district, synergies are created that enable the post-war housing estate in need of refurbishment to benefit from the innovative measures in the new-build area.
Conception, Work programme (before-after)

The focus of the project is on developing technically innovative measures involving local heating and LowEx technology for new-build schemes and refurbished existing buildings with different building types. The following overall measures are planned:

  • Before: The officers’ apartments in Sonnenberg were heated with fossil fuels.
  • After: Model area for the future: LowEx sub-grid for the passive house residential estate with energy-plus ambitions in Sonnenberg Southwest.
  • Before: The Grünbühl housing estate was heated decentrally with fossil fuels and the building energy standard is poor.
  • After: Expansion of the local heating network, urban redevelopment and social stabilisation in the Grünbühl district.
  • Exemplary refurbishment of an historic school building with a sports hall and swimming pool to become an energy-plus building in Grünbühl. Renewable local heating micro-network with decentralised solar energy injection as a basis point for the Grünbühl grid expansion.
  • Before: High cooling requirement for the commercial enterprises with high CO2 emissions as a result of heating with fossil fuels.
  • After: Low-Ex concept with geothermal recooling and heat source for heat pumps for commercial enterprises including Aldi, the Theo Lorch Workshops and a gardening centre in Grünbühl.
  • Smart metering in the electricity + heat sectors, intelligent load management monitoring is planned.

Energy characteristics

before potential after unit
Total area with energy requirement 112.000,00    
Final energy requirement (heat) 119,00     kWh/m²
Primary energy requirement (heat) 126,50     kWh/m²