A few days ago, Stadtwerke Gießen commissioned the first section of its second thermal residue treatment and energy utilisation plant (TREA 2) - after a construction period of just 16 months. The modern plant now produces heat and electricity simultaneously in a climate-friendly way. A milestone for the energy transition in Giessen and the entire region.
Since 2010, the thermal residue treatment and energy utilisation plant, TREA for short, has been producing heating energy from waste for the Giessen heating network. The plant has played a key role in making the university city in central Hessen one of the pioneers in terms of climate-friendly energy supply. Stadtwerke Gießen (SWG) is building on this success with TREA 2. The first part of the power plant went into operation on 6 December. While the solid fuel line is expected to go into operation at the end of next year, the two combined heat and power (CHP) plants are already running at full capacity.
In addition to heat, TREA 2 - unlike TREA 1 - also produces electricity. The engineers have further developed the original operating principle and done pioneering work in the process. The biggest challenge: the temperatures generated during the incineration of the medium-calorific waste are not sufficient to drive a generator. Two CHP units therefore provide the necessary temperature increase. The exhaust gases from these efficient units are so hot that they heat the vapour to over 350 degrees Celsius - enough to generate electricity.
Electricity and heat for thousands of households
Matthias Fink, Head of the Heat Supply Department at SWG, emphasises one of the key advantages of TREA 2: "The entire plant is extremely variable. We can operate it in the range of 1.3 to 5.5 megawatts of electrical output and thus react flexibly to the respective electricity demand or the current market situation." Based on the experience with the first TREA and the CHP modules, Matthias Fink expects an annual operating performance of around 7,400 hours. This means that the TREA 2 would cover the heating requirements of up to 4,200 single-family homes and the electricity requirements of around 13,500 average households. Figures that prove it: TREA 2 takes the energy transition in Giessen another big step forward.
All-round clean energy
With TREA 2, SWG is increasing its own generation ofCO2-neutral electricity to 180,000 megawatt hours per year. In addition, the plant being built right next to the first TREA will in future provide 17 per cent of the heat required in the SWG grid. This will have a positive impact on the already excellent environmental balance of SWG district heating. Matthias Fink assumes that the current primary energy factor of 0.28, which is already very good, will fall to well below 0.2. The primary energy factor is the ratio of fossil fuels used to the heat produced. This means that in future, SWG will need less than 0.2 kilowatt hours of natural gas or heating oil to produce one kilowatt hour of heat.
At the same time, the TREA 2 fulfils all current requirements in terms of environmental protection - and more than meets them. The solid combustion residues are free of toxins and can be used in road construction. As in the TREA 1, sophisticated flue gas cleaning technology ensures that no hazardous pollutants are released into the environment via the chimney. On the contrary, it saves the environment 28,000 tonnes of climate-damaging carbon dioxide every year and the fuel - processed waste - comes from the region.
07.12.2016