Nyhet | 2018-09-05 | 16:02

Identification of waste heat sources in Uppsala – with potential use in Bergsbrunna as a case study

Master thesis by Malin Frisk and Elise Ramqvist.

Abstract

This master thesis was carried out at Vattenfall Research and Development in collaboration with Uppsala Municipality with the aim of identifying the waste heat potential in Uppsala Municipality. This work can be divided into three main parts. 

1. A survey was sent out to a great amount of businesses in Uppsala Municipality to collect data about the waste heat generating processes. It was realized that this method was not as successful as expected.
2. The maximum theoretical amount of waste heat was estimated by hourly based waste heat profiles developed for a number of low temperature waste heat sources, such as grocery stores of different sizes, ice rinks, indoor swimming pools, hotels and restaurants. This amount adds up to approximately 62 GWh per year, which corresponds to roughly 5% of the district heating demand in Uppsala.
3. Lastly, it was assed how low temperature waste heat sources in a low temperature district heating network could contribute to the heat supply in a newly developed area, which was realized by a case study of Bergsbrunna. The low temperature waste heat was upgraded by means of a heat pump, therefore costs related to this temperature rise were calculated. It was found that the waste heat sources could cover the heat demand by 14% and the lowest cost is 0.34 SEK/kWh for raising the temperature to the supply temperature of 60°C in a low temperature district heating network. This was compared to raising the temperature of the low temperature waste heat to a conventional district heating network with a supply temperature of 80°C, where the lowest cost was estimated to 0.39 SEK/kWh.

It should be mentioned that a number of assumptions have been made to calculate the waste heat potential. The most important assumption is addressed to the fact that the potential is based on secondary data of an average energy use in different buildings on a national level, which was not intentionally collected for calculating waste heat potential. The urban planning used in the case-study of Bergsbrunna is based on several assumptions. Thereby, it is not certain that this represents Bergsbrunna in the future or another area of the same size. Also, the heat production cost only includes approximated investment and installation costs of the heat pump and the electricity costs, which are based on historical data.