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Optimization of data centre waste heat integration into existing district heating networks

The number of data centres (DC) in recent years is growing rapidly, and with that, the share in total consumption of electricity is growing too. A significant amount of electricity is transformed into heat energy which increases the optimal temperature in data centres for component operation. This heat needs to be removed and usually, it doesn’t have any further application. Today it is recognized that waste heat can be integrated into district heating (DH) and by using it reduce the usage of conventional heat fuels. Utilization of waste heat is possible in three ways: with a heat exchanger (HE), with a heat pump (HP), or with the combination of the heat exchanger and heat pump. In this paper, a combination of the HP and HE was used. Although those utilizations are examined and implemented, there is a lack of research on the optimization of integration of waste heat in district heating networks. To perform optimization, a thermodynamic model of the data centre and a linear programming optimization model were developed, whose objective function is to maximize the amount of waste heat exploitation considering the pinch temperature gap, and temperature regimes of streams by minimizing the cost of the HE. The created model consists of the data centre, vapor compressor chiller, HE, HP, and cooling tower. As a case study, the City of Zagreb was chosen, together with its existing data centres and district heating network. Optimization was conducted considering the possibility to use different refrigerants in HP, and various temperature regimes in the DH network. This article will give insight into the results such as the Coefficient of Performance (COP) of HP, the percentage of used waste heat, energy savings due to waste heat integration in the DH network, and cost-benefit parameters. The main outcome of the paper is to analyse how the optimization of waste heat integration impacts the Levelized cost of heat (LCOH), cooling tower capacity, and heat energy savings in DH.

district heating, waste heat, data centre, optimization, heat exchanger, heat pump, LCOH, energy savings

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