Unconventional Excess Heat Sources for District Heating in a National Energy System Context

Steffen Nielsen,Diana Moreno,Rasmus Lund,Kenneth Hansen

doi:10.3390/en13195068

Abstract

District heating (DH) is an important technology in future smart energy systems as it allows for an efficient implementation of various renewable energy sources. As DH develops towards lower temperatures and renewable electricity production increases, new types of heat sources become relevant. Thus, the aim of this article is to assess the potential for utilizing four unconventional excess heat (UEH) sources in DH systems, namely: Data centers, wastewater treatment, metros and service sector buildings. The main method used to assess the UEH potentials is an energy system analysis focusing on the availability and economic feasibility of utilizing the UEH sources in national contexts. The analysis consists of 2015 and 2050 scenarios for Germany, Spain and France. The results show a potential for utilizing the UEH potentials in all three countries, both in 2015 and 2050 systems. The potentials are highest in the 2050 scenarios, primarily due to larger DH shares. Furthermore, the potentials are limited by competition with other heat supply sources, conjunction with heat demands and feasible heat pump operation. In conclusion, the four UEH sources could impact the local DH systems, but in a national energy system context they are expected to play a minor role.

Highlights

With most countries having ratified the Paris Agreement [1] and thereby ensuring the long-term climate targets, the focus has turned towards technological solutions that can contribute to the realisation of the goals
The results show that utilizing the unconventional excess heat (UEH) sources can reduce the of 18 primary energy supply in all countries; the potential is higher in 2050 compared to122015, mainly due to the District heating (DH) coverage being larger in 2050
This paper examines the potential of integrating four UEH sources in DH systems, within a national context, and with the aim of lowering the emissions and economic costs of the energy systems

Summary

Introduction

With most countries having ratified the Paris Agreement [1] and thereby ensuring the long-term climate targets, the focus has turned towards technological solutions that can contribute to the realisation of the goals. The basic idea behind smart energy systems is to find the best solutions by applying a holistic approach, examining solutions across various energy infrastructures, namely electricy, heating and gas networks, and different energy sectors such as transport and industries. In connection to the smart energy system concept there has been a revival of the benefits of utilising DH in urban areas, as these systems allow for more renewable energy integration in the overall energy systems, technologies such as combined heat and power (CHP) plants, excess heat from industries [4] and waste incineration, solar thermal, geothermal as well as large scale heat pumps. There is a general need to develop the DH systems towards the so-called fourth generation DH [5,6]. The fourth generation DH is characterized by forward temperatures that are reduced to 55 ◦ C from typically

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