For the sixth year in a row, Stadtwerke Gießen has succeeded in reducing its primary energy factor in heat and electricity generation for the city of Gießen. This is accompanied by a significant reduction in carbon dioxide emissions.
0.36 - Stadtwerke Gießen (SWG) was able to reduce the primary energy factor for the city of Gießen to this new peak value in 2014. Experts can read the efficiency of heat production from this figure, which is unimpressive to the layman. The primary energy factor describes the ratio of fossil fuels used, such as coal, oil or natural gas, to the usable heat generated. In concrete terms, this means for Giessen: SWG only has to use 0.36 kilowatt hours of natural gas for one kilowatt hour of heat.
In 2013, thanks to its three wood-fired heating plants, the TREA and several biogas-fuelled combined heat and power plants, SWG recorded a primary energy factor of 0.41, which is already exceptional in a nationwide comparison. The recent improvement is the result of the strategy that SWG is consistently pursuing. "At the beginning of 2014, we converted another four CHP units to run on biogas," explains Matthias Funk, Technical Director of Stadtwerke Gießen. This means that 19 of the 59 CHP plants in Giessen now run on renewable energy.
However, the Lahnstraße is not satisfied with the current low figure. On the contrary. When TREA 2 is connected to the grid in 2016, the primary energy factor is likely to fall significantly below the 0.2 mark in one fell swoop. In 2018, the biowaste fermentation of biowaste from the district of Giessen could possibly be added. "Ultimately, we are aiming for a primary energy factor of zero," says Matthias Funk, explaining SWG's plans. When this is achieved - Matthias Funk expects it to be by 2020 at the latest - more than 50 per cent of Giessen's district heating will be generated from non-fossil fuels.
Solid calculation
To precisely determine the primary energy factor, Stadtwerke Gießen uses the generally recognised formula defined by the independent district heating working group. This also takes into account the energy required to produce and supply the fuel - for example, fuel for tanker lorries or energy for transporting natural gas over long distances. Two comparisons show how good the value of 0.36 is: an inherently efficient natural gas condensing boiler is considerably higher at 1.1, while the current electricity mix in Germany is 2.4. There is another important reason for SWG being able to reduce its primary energy factor so drastically, in addition to the switch to renewable energies: Stadtwerke Gießen has always produced a large proportion of the heat it requires using combined heat and power generation. "The electricity generated at the same time has a positive effect on the calculation," Matthias Funk calculates. After all, no additional primary energy is needed for this.
Combined heat and power generation as the basis
It is only thanks to this efficient combined heat and power generation that the primary energy factor in Giessen can reach zero in the medium term. This is because regenerative fuels also have a primary energy factor greater than zero. For example, it is 0.2 for wood pellets and 0.5 for biomethane, whose transport or production is dependent on the use of fossil fuels for the time being - such as machines for harvesting the energy crops or for shredding the wood and then pressing it. "My predecessors laid the foundations for our good primary energy factors in Giessen almost four decades ago," admits Matthias Funk. In 1982, Giessen's first CHP plant went into operation in the Ringallee bathing centre - the nucleus for one of the most efficient district heating networks in Germany.
Significantly lessCO2
Because the primary energy factor is essentially reduced through the use of renewable energies, it naturally has a direct, positive influence on carbon dioxide emissions. If the same quantities of heat and electricity were generated separately in conventional boilers and power plants, around 45,000 tonnes more climate-damagingCO2 would be produced each year. Stadtwerke Gießen saves the environment precisely these emissions. As long as the factor is 0.36. If the value continues to fall - and this is already foreseeable for 2015 -CO2 emissions and primary energy consumption will fall again. And when the primary energy factor reaches zero, around 125,000 tonnes less carbon dioxide will be released into the atmosphere every year.
Your contact for district heating
With its pipeline-based heat supply in Giessen, SWG provides its customers with an economical, sustainable and competitive heat supply. All legal requirements - including those relating to subsidy programmes - are met by the Giessen heat supply.
If you have any questions about district heating, the contact persons at the SWG customer centre on the market square in Giessen can help you and put you in touch with the relevant experts at Stadtwerke Giessen. Opening hours: Monday to Friday 9 a.m. to 6 p.m. and Saturday 9 a.m. to 2 p.m.