Case Report

Energies to Reduce CO2-Emissions at Saarbrücken

by Jürgen Lottermoser, City of Saarbrücken, Germany

1. CO2-Reduction Program

The city of Saarbrücken was engaged in the "CO2-Reduction Project" of the International Council for Local Environmental Initiatives (ICLEI) since 1991. In the framework of this very interesting project the city developed a CO2-Reduction Program, well adapted to the specific situation at Saarbrücken. In june 1993 the program was adopted by the city council, after a detailed discussion.

The general goal of this program is a reduction of the CO2-emissions from energy-consumptions and traffic by 25% in the time period from 1990 to 2005.

The total CO2-emissions in the year 1990 are 1.952.000 t. The city has 200000 inhabitants. The specific emissions are roughly 10 t/year and inhabitant.

2. Energy Saving

A lot of energy saving measures are possible with different strategies. Some of the most important are presented.

2.1 Cogeneration

About 95% of the electricity demand is generated in power plants, owned by the municipal city works ("Stadtwerke"). These power plants are all working in cogeneration, the heat is fed into a relative large district heating system. About 30% of the total heating demand in the city is now covered by the district heating system.

The Stadtwerke are now, step by step, enlarging the district heating system and more and more individual buildings can switch from coal- or oil-heating plants to district heating. This is giving considerable drops in the CO2-emissions. The details of this program are not so easy, because of the big investments necessary for the construction of new district-heating-lines.

In some parts of the city the density of the buildings is not so high, in consequence a district heating system as described before will never be economic. In these cases the "Stadtwerke" are constructing small motor-driven power plants working in cogeneration, if this is economic. A detailed study showed, that about 100 of these small units may be economic.

2.2 Advise of the citizens, trade and industry

The citizens have a very important role in the CO2-reduction program, because they are directly responsible for a large part of the total CO2-emissions.

For that reason we have an Energy-Information Center in the city. Each citizen can learn, what he can do himself to reduce the energy consumptions, as well for heating as for electricity. Practical demonstrations are given, a "solar school" is integrated, to inform on the use of solar energy and so on.

A similar service is also offered by the "Stadtwerke" to trade and industry, to develop programs to save energy and money for the consumer.

2.3 Good example of the municipality

In the municipality-owned buildings, as schools, swimming-pools, sporting centers, offices, we are demonstrating the possibilities of saving energy, water and money (because all the taken measures are economic). We have reduced the CO2-emissions in the time period from 1980 to 1995 by 49%, demonstrating that the goal of 25%-reduction in 15 years is possible, if a strategic action program is consequently realised.

3. Renewable Energies

Our goal is to use about 10% of renewable energies in the heat market and about 1% of electricity in the year 2005. To understand this goal better, it is important to know that solar radiation is about 1 kWh/(m2.a) on a horizontal plane at Saarbrücken.

Different techniques will be applied:

3.1 Absorber System

Absorber Systems are more or less black tubes to be put on a roof. These systems are very cheap and well suited for the heating of outdoor-swimming-pools. The municipality is now running 3 of 4 outdoor-swimming-pools only with solar heating using absorber systems. This is even with the low energy prices of today economic. Total use of solar energy is approximately 700 MWh/year, corresponding to 70000 1 of oil at least.

3.2 Collector systems for domestic hot water

These systems are not so economic. We have now about 100 m2 installed, which is a rather small surface. Further activities are planned in the future.

3.3 Photovoltaic

Photovoltaic is expensive, but technically interesting. We have now installations of 220 kWp in the city, which corresponds roughly to 1 Wp/inhabitant.

The city has made a plan to make installations of 1000 kW on the roof-tops. The economic conditions today are favourable:

New activities are planned to reach the goal.

3.4 Wind

The mean wind speed at Saarbrücken is 2,0 m/s. This is too small to run wind turbines.

But 50 km north from the city on the tops of some hills, the Stadtwerke are engaged in a farm of wind turbines with a maximum capacity of 4,2 MW.

3.5 Hydro Power

The possibilities are limited, because at Saarbrücken we have only one river and no mountains. One hydro-power plant with a capacity of 2 MW is under construction. A second power plant with a capacity of 400 kW is planned today.

3.6 Heating with seasonal storage

We have enough solar energy in summer, but we need heating in winter. The idea of the seasonal storage is to use big water tanks to store solar energy by heating this water up in summer and to use this energy in winter for the heating of buildings.

We have developed a project with this new technique, which will probably be realized in the near future. The technique is rather simple, but installation costs are high. But probably we will get public funding for this project to give us the possibility of realisation.

The potential of this technique for CO2-reduction is high.

3.7 Biomass

Different kinds of biomass can be used: All these techniques are under examination, some small plants are realised.

4. Conclusion

A CO2-reduction program with an annual reduction of 1 to 2% is not easy to realise, but possible. Main problems are the low energy prices for fossile fuels and the relative high costs of the available techniques for the use of renewable energies. But we have to keep in mind, that 50 years later oil and natural gas will become rare and very expensive. Energy consumption will become not only an environmental problem but also a social and economic problem. The best solution of these problems is the reduction of energy consumption and the use of renewable energies.

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