Energy supplyThrough the comprehensive use of solar energy, compact construction, and measures to avoid overheated dwellings in the summer months, the energy demand was kept extremely low.
The name solarCity stands for the comprehensive use of solar energy in the sense of the European Charter for Solar Energy in Architecture and Urban Planning of 1996. The term “solar” is conceived as broadly as possible and begins with the planning of the buildings in accordance with the principles of solar architecture. This includes the use of both passive and active solar energy and does not exclude possible uses of renewable energy sources.
Individual access to the sun is achieved by making the dwellings as sunny and bright as possible, with large window areas. Technically speaking, passive uses of solar energy, such as sun-facing windows and conservatories, provide not only greater living comfort but also better heating of the respective rooms in winter. Solar panels on the roofs of the buildings contribute actively to the provision of hot water.
An essential element of solar architecture is the orientation of the building according to solar factors. In the solarCity the distances between the buildings as well as their heights were selected so as to allow sunlight to penetrate directly into the rooms of the dwellings even in the winter months. Low-energy building construction, achieved by means of the concepts and technologies of solar architecture, compact construction, and optimal thermal insulation, was implemented throughout the entire urban district of the solarCity. This introduction of low-energy building construction on a broad basis was a trendsetting step in the history of social housing in Upper Austria.
The solarCity evinces many different varieties of solar construction. They range from east-west-oriented, deep buildings with large window areas to south-oriented buildings with six-meter-high conservatories as solar facades or passive houses in various styles of construction. The solarCity clearly demonstrates that excellent results can be achieved by applying a wide variety of approaches to solar architecture within one housing estate.
Exemplary model, subsidies
The open approach taken by the City of Linz with respect to numerous aspects of solar energy use and resource-saving construction enabled the new urban district solarCity to become an exemplary European model for low-energy construction using alternative energy sources in social housing.
Twelve housing developers concluded a joint contract with the City of Linz; the specifications in this contract included standard values for the generation of solar energy and the maximum energy demand of the buildings. As a result, all the housing developments and public buildings were constructed as low-energy buildings with solar panels on their roofs.
In general, at least 34% of the hot water in the solarCity housing developments was to be provided by means of solar energy. In actuality, solar energy systems cover about 50 % of hot water needs in the solarCity.
The City of Linz supported the construction of these solar energy systems with financial subsidies. The municipal subsidy system for solar energy systems in communal housing provides for a basic allowance of 720 euros plus 150 euros per square meter of collector area. In total, the twelve housing developers installed some 3.500 square meters of solar panels on the roofs of their buildings.
It was decided that energy demand must not exceed 44 kWh/(m²a) in each of the buildings of the solarCity. As a rule, the buildings are even more energy-saving than specifications required, so that the average energy demand throughout the urban district is, in fact, only 36 kWh/(m²a).
The avoidance of overheated dwellings in the summer months is just as important as compliance with energy demand thresholds. Therefore, all the developers had to submit proof that their buildings were summer heat resistant.
All the buildings of the solarCity are heated by means of the district heating network of LINZ GAS/WÄRME GmbH. Implementation began in the spring of 2002 with the construction of a supply line that is about 2000 meters long (diameter 150 mm), from Linz-Ebelsberg via Hillerstrasse and Traundorferstrasse to Lunaplatz, the center of the “sun city”. The transport medium selected is a steel pipe with a polyethylene coat. The high-quality insulation of the interstitial space with polyurethane foam ensures a very low heat loss, which in fact amounts to only eight per cent from generating plant to consumer. But careful planning also contributed to the results: thanks to the incorporation at an early stage (1999) of what was then called the ESG district heating system into the infrastructure planning of the solarCity Linz-Pichling, it was possible to optimize the district heating distribution system both technically and economically.
LINZ AG is one of the leading energy concerns in Linz and Upper Austria. The company philosophy focuses on its responsibility for people in the supply area and for the environment. With the modernization of the district heating plant Linz-Mitte in 2004 and the construction of the 65-meter high thermal storage tank (capacity 35,000 m³) the company already began to place important accents in Austrian energy politics a number of years ago. The new biomass heating plant is a further milestone on the path to sustainable, ecologically oriented electricity and district heat supply in Linz. By producing both electricity and district heat at the same time - known as cogeneration or combined heat and power - the utilization rate of heating material achieved is more than 85 per cent – a top value. The new plant annually supplies around 17 per cent of the district energy consumed and gives the energy supply system a third basis in addition to gas and oil. Thus the new biomass heating plant - incidentally the largest of its kind in an Austrian regional capital - also plays a significant role in reducing Kohlendioxid emissions and the use of primary energy. This goal is also part of the mission statement of solarCity Linz-Pichling.
The customers of the district heating system profit from a sure supply of environmentally friendly heating and an economic form of energy that is stable in price. A comparison of all the district heating companies in Austria reveals that LINZ GAS/WÄRME GmbH charges the most reasonable prices for residential heating.