Analysis and Improvement of an Existing University District Energy System

Abstract

Climate change is one of the greatest crises facing humanity in the 21st century. It is a complex challenge that affects all levels of society, from the personal to the international level. Only if all parts of the international community work together, it will be possible to limit global warming to 1.5 °C above pre-industrial levels, as agreed in the Paris Agreement on Climate Change in 2015. An important contribution to this must be made in cities and districts, which are becoming increasingly more important due to the worldwide progress of urbanization. Within the district, energy demand of buildings has a great influence on the CO2 emissions. A centralized supply of thermal energy via district heating and cooling enables highly efficient generation via combined heat and power or combined heat, power and cooling as well as the integration of locally available waste heat sources from industrial plants or data centers. By means of cost-efficient thermal storage, generation and demand can be decoupled from each other, and operating times of combined heat and power plants can be extended. In addition, renewable sources such as solar thermal energy can be used more efficiently. The basis of this work is a dynamic simulation model of the energy system of campus Lichtwiese of the Technical University of Darmstadt, which represents and connects the generation plants, the thermal networks and the buildings as consumers. Using time series of the current and future energy demand of the buildings for heat, cooling, and electric energy, the energy production of the entire system and the resulting CO2 emissions and costs can be calculated. By comparing different scenarios via annual simulations within the model, the example of campus Lichtwiese shows how existing energy systems can be prepared for a local energy transition at the district level. Research focuses on the optimization of the design and operation of existing energy systems with 3rd generation district heating networks, the reduction of temperatures to transfer the networks to 4th generation district heating, and the integration of data center waste heat. All proposed measures are compared energetically, ecologically and economically with the current state of the system. The results show that the energy system of the TU Darmstadt is well designed and operated for the current demand, while at the same time there is great potential for reducing temperatures and energy demands by measures within the buildings. Furthermore, it can be shown that the integration of data center waste heat into district heating is already ecologically reasonable today, even without a prior reduction of network temperatures. By implementing the developed measures, the CO2 emissions of the district can be reduced. More important, however, is that the measures presented are a prerequisite to decarbonize the TU Darmstadt campus Lichtwiese energy system in the medium term, especially regarding heating and cooling. The measures developed for campus Lichtwiese can be transferred to other districts. The decisive factor here is comprehensive energy monitoring, which enables the operator to gain a good understanding of his system, to identify faults with little effort and to take corresponding measures to improve their system.