HOT|COOL NO.3/2021 - "Don't waste it!"

Heat and hydrogen THE NEWPOWER COUPLE A key to making Power-to-Xmuch more energy-efficient - and cost-effective - is district heating (DH). A key to making 100% carbon neutral DH is integrating excess heat from other sectors. Also, municipalities and governments are beginning to see that, together, heat and hydrogen can increase the speed and quality of the green transition.

Don't use hydrogen for heating. Use DH and PtX in combination.

By Hanne Kortegaard Støchkel, author of the report, Project Development Manager, DBDH Jannick Buhl, Chefkonsulent, Dansk Fjernvarme

Report on integration of Power-to-X and district heating This article is based on a comprehensive report on the integra- tion of Power-to-X (PtX) and district heating (DH) in Denmark. The report is published by the Danish District Heating Associa- tion, the think tank Grøn Energi, COWI and TVIS. Why Hydrogen? PtX is closely tied to the green transition in the transport of goods by road, sea, and air and the production of carbon-neu- tral fertilizers for agriculture and carbon-neutral forms of prod- ucts such as steel, plastic, and chemical products. This gives a rapidly increasing demand for green hydrogen in the coming year. This underlines the need to use green hydrogen where it is most needed and most valuable – and that is not for heat- ing. For heating, much better alternatives exist already today. In rural areas, this could be small, electric heat pumps. In more densely populated areas, the cheapest and most efficient solu- tion is DH based on renewable heat source and reused surplus heat. Some argue that hydrogen should be used in households for heating, but it makes much more sense to combine PtX with DH and use the surplus from the hydrogen production for heating. PtX processes involve energy losses in the form of heat, and infrastructure is needed to collect and use that heat. That is where DH systems come in (Figure 1).

requires two things: green hydrogen and green carbon. The hy- drogen comes from electrolysis. Carbon, in the form of concen- trated, green CO 2 , will become a challenge, but both WtE and biomass-based units for heat production are essential sites for collecting large quantities of CO 2 for storage or use in e-fuels. Don’t waste green energy The forecasted electricity consumption for PtX is significant and so are the accompanying energy losses. Assessments on electrolysis show that usable waste heat makes up around 10- 25 % of the energy input to the hydrogen plant. With energy ef- ficiency becoming more and more important, energy losses on that scale must be investigated and converted into solutions. Faster and better green transition Due to the climate challenges, we have to develop efficient so- lutions and implement them quickly. But risks and creating a good business case for hydrogen production are holding back PtX. By integrating PtX and DH, the owner of the hydrogen plant can sell the surplus heat to the DH company - generat- ing revenue and increasing the competitiveness. From the DH point of view, utilizing surplus heat fromhydrogen production can replace fossil-based heat production and pro- vide energy for new DH areas currently heated by natural gas.

A less known link between PtX and DH comes through the waste-to-energy (WtE) plants. The production of most e-fuels



PtX refers to green power to produce a product (X), which could be green hydrogen, basic green chemicals, e-methane, e-methanol, green ammonia, or green aviation fuel. All PtX processes require hydrogen. Electrolysis is, therefore, an essential element in the green transition because it converts water into hydrogen and oxygen using green electricity.

Energy loss (heat)

District heating

Figure 1: PtX converts power into another energy source called 'X,' for instance, hydrogen, methanol, or aviation fuel. In energy conversions, a substantial part of the energy is converted into surplus heat - potentially to be utilized for DH.

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