Diploma's thesis Tobias Claus


Analysis of the potential of waste heat recovery for a district heating system in the area of Bottrop - Welheimer Mark

Flowchart for waste heat potential analysis Copyright: EBC Flowchart for waste heat potential analysis

This thesis was written within the scope of the research assignment from the RWTH-Aachen E.ON Energy Research Center in the project Eneff:Stadt – Bottrop, Welheimer Mark. Welheimer Mark is a district of the city of Bottrop in North Rhine-Westphalia. The district includes two industrial areas and a residential area. The objective of the project is the development of an optimized district concept to reduce the CO2 emissions by 50 % until the year 2020 towards the reference year 2010.

This thesis analyzes the potential of industrial waste heat for district heating systems. Industrial processes produce waste heat. Waste heat is the part of the heat which leaves the process but has no purpose for the performance of the process. The thesis analyze to what extent the use of waste heat in district heating systems can help to achieve the CO2 emission target.

First of all methods for qualitative and quantitative determination of industrial waste heat are investigated. Afterwards, options for use of waste heat are under discussion. Direct use of waste heat in heating systems as well as indirect use in thermal heat pumps, chillers or conversion into electricity is possible.

The external use of waste heat by third parties is competing with the internal use. Feeding district heating systems comes into consideration when the internal potential for waste heat usage is exploited. District heating systems can increase the energy efficiency when high quality forms of energy like fuels or electricity are substituted. The use of waste heat lowers the amount of CO2 emissions of heat delivery. From the economic point of view district heating systems cause high initial investments which must be compensated by energy savings during the operating life towards the decentralized heat generation in buildings.

For the project Welheimer Mark a model was designed which considers economic and ecological parameters of industrial waste heat delivery for heating demand of residential and industrial buildings. Six scenarios for the district heating grid are considered. At the beginning single industrial buildings are plugged to the grid. Afterwards the grid is successively enhanced to both industrial areas and the residential area. The economic evaluation is based on avoidance cost of CO2. The ecological evaluation is based on the emission reduction due to substitution of fuel by waste heat.

The results show cost advantages through the use of waste heat in case that companies close to the heat source can be supplied. The integration of small-scale consumers reduces the specific head demand per meter too much for an economic operation of the grid. The maximum decrease of CO2 emissions due to the use of waste heat and combined heat and power is 30 %.