Decarbonization of heating networks will require energy-to-heat technology – Euractiv

In the energy sector, electricity production can be decarbonized relatively quickly, but other sectors such as heating will be much more difficult to decarbonize. We have over 17,000 district heating systems in Europe, of which only 43% use renewable energy sources and waste heat. However, this may change. Power-to-Heat technology shows how renewable energy can also be used for heating. As indicated in the latest report of the Polish Association of Utility Heat and Power Plants, the use of electricity for heat may be one of the most preferred and useful options for decarbonizing heating systems in Poland.

The article comes from the Polish Electricity Association (PKEE) and the Polish Association of Commercial CHP Plants (PTEZ)

What is power-to-heat technology?

The power-to-heat concept refers to the possibility of transforming electricity generated from renewable energy sources into efficient heating or cooling. Technologies for converting energy into heat have been available on the market for a long time, not to mention electric boilers such as electrode boilers and heat pumps.

Heat pumps use electricity to extract heat from the ground, water or air, amplify it and then use it to power heating systems. This technology is already very mature, with a wide range of performance and high efficiency of up to 250-500%. Heat pumps are a source of low-temperature heat (approx. 80-90°C), which in some heating systems may involve additional investments in heating networks due to lower parameters of the feed water.

Electrode boilers directly convert renewable energy into heat – water is heated in huge tanks to a set temperature – up to 160°C – which allows the boilers to be a source of heat in high-temperature heating networks. The heat production efficiency of electrode boilers is practically independent of the unit load and is approximately 99%. Additionally, there are no greenhouse gas emissions or other pollutants produced by combustion-based systems.

Power-to-heat technologies are very well suited to the current trend of combining the electricity and heating sectors. Operating electrode boilers with heat storage (heat accumulators and seasonal heat storage) simply allows the use of surplus renewable energy, which can be converted into heat, stored and released when needed for district heating. Moreover, the use of heat storage contributes to the purchase of electricity on SPOT or balancing markets at favorable prices (low or even negative) regardless of the time of heat demand, which in turn further improves the profitability of using power-to-heat technology.

How can power-to-heat technology help accelerate the transformation of district heating?

By converting electricity into heat, power-to-heat technologies contribute to increasing the share of renewable energy in the heating sector. If these systems are operated using renewable energy, it also helps protect the climate by reducing CO emissions.₂ emissions and use of fossil energy sources.

Technologies such as electrode boilers are needed in Central and Eastern Europe, where most district heating systems operate at high temperatures, because they can provide a stable peak heat source while providing technical capabilities that low-temperature technologies cannot yet provide. Heat pumps, especially large-scale ones, can also be used in district heating, but they are most efficient at lower temperatures. This means that at negative outdoor temperatures, heat from heat pumps requires an additional temperature increase to be used in high-temperature networks, for example during the frosty winters we have in Poland.

Due to the different operating conditions of these two technologies in district heating systems, heat pumps have the potential to replace base units that use fossil fuels to generate electricity. On the other hand, the use of electrode boilers combined with heat storage can help replace peak load generating units.

Since the process of replacing heating networks with low-temperature ones involves significant costs and inconveniences for residents as well, it should be assumed that it will take a long time. Hence, both of the above-mentioned power-to-heat technologies should be treated as complementary in the transformation of heating systems.

How can energy-to-heat technology play a role in power systems?

According to the Commission’s Impact Assessment Report on the European climate target for 2040, to achieve climate neutrality, Europe needs 3,760 TWh of clean electricity and needs to electrify more than 50% of the European economy. Therefore, we cannot afford to lose even one MWh of clean energy. However, when renewable electricity generation, mainly solar and wind, increases, this can lead to constraints if the electricity system is not flexible enough and demand does not match the temporary increase in renewable generation. Converting surplus electricity into heat can help stabilise the grid and integrate a larger share of intermittent renewable energy to provide demand-side flexibility in electricity systems. Additionally, when it can be combined with electricity or heat storage, it increases the efficiency of renewable energy use while optimising costs and meeting heating needs.

Only in Poland, restrictions on the production of energy from renewable sources from the beginning of 2024 to the present (20^t June) reached 460 GWh – which means that this much renewable energy was lost. In this case, too, converting energy into heat, and especially electrode boilers and heat storage, can be a way to reduce constraints and increase the potential for using clean energy. In the future, an increase in the installed capacity of RES is expected, and consequently, an increase in the share of RES in the national energy mix. The share of RES in electricity production during constraints was then an average of 55%. This means that the heat generated in electrode boilers will already constitute at least 55% of RES, and in the future this share will increase even more.

Fig. 1: Level of RES limitations and share of RES in electricity production in particular hours in Poland based on announcements of the Polish TSO.

Energy-to-heat conversion technologies allow for a significant reduction in variable costs, which contributes to the stabilization of heat prices paid by consumers. The situation on the coal fuel and natural gas markets, as well as on the CO market, has the greatest impact on price parameters₂ emission allowances. These parameters are highly variable, which increases the risk of investing in heat sources based on fossil fuels. At the same time, energy-to-heat technologies are resistant to environmental costs – they are not directly related to the combustion of fossil fuels and are intended to be used when electricity prices are low.

Fig. 2: Example of SPOT prices and the balancing market in Poland during hours of renewable energy restrictions. Based on data from the Polish Volunteer Fire Department and ENTSOE.

During the hours of RES generation surpluses and RES limitations – electricity prices in Poland on the SPOT market and balancing market were very low or negative. During these hours, power-to-heat technologies could be used to produce heat from electricity.

How will power-to-heat technology contribute to the goals of the Fit for 55 standard?

Energy-to-heat conversion technologies, both heat pumps and electrode boilers, are among the key solutions that will enable cost-effective decarbonization of heating systems in Poland, while enabling their transformation in directions consistent with the criteria of effective heating systems within the meaning of the definition as amended by Art. 26 of the Energy Efficiency Directive (EED). These criteria set the path to achieving climate neutrality in heating systems, while maintaining the status of an effective heating system, enable access to financing and are at the same time treated as one of the preferred methods of heating zero-emission buildings, the definition of which is introduced by the amended EPBD directive (Energy Performance of Buildings).

Are energy-to-heat technologies already used in Europe?

There are many examples of large-scale power-to-heat technology applications across the European Union. One of the largest investments that implemented a large-scale power-to-heat project was carried out by PGE Energia Ciepła, a part of the PGE Energy Group in Gdańsk – in northern Poland. It consists of two electrode boilers with a capacity of 35 MWt each and can convert green electricity into heat.

From January to June 2024, these two boilers delivered clean heat to the district heating system for 2,364 hours, avoiding 22,963 tons of CO₂ emissions that would result from the combustion of 11,040 tons of hard coal delivered in 552 wagons. By 2030, PGE intends to build almost 1 GWt of electricity-to-heat technologies, including both electrode boilers and heat pumps.

Other examples of the implementation of the Power to Heat technology in Poland are the Szlachęcin project of the Veolia Group (a heat pump system with a capacity of 1.7 MW) and the Wrompa project by Fortum in Wrocław (12.5 MWt). As for European projects, in June 2023, the largest air-water heat pump system connected to the heating network in Espoo (Finland) (11 MWt) was put into operation, and two electrode boilers with a total capacity of 100 MW were put into operation. in the same city in 2023.

What are the most important issues related to the development of power-to-heat conversion technology?

The goal will be for all heating systems to meet the criterion of an efficient heating system. Power-to-heat solutions should be considered to provide renewable heat if it is possible to use, for example, power purchase agreements (PPAs) or a guarantee of origin mechanism to prove the renewable nature of the electricity used in the power-to-heat solutions .

The provisions of the EED and RED III directives allow this amount of electricity from renewable sources to be considered as meeting the criteria for an efficient heating system, and PPAs or a mechanism based on guarantees of origin can be used for this purpose. There is also a need to create financial support mechanisms for technologies for generating electricity into heat. First, the implementation of the investment will require financing; funds for this purpose should come from both EU and national sources. The transformation of heating should be a priority in the new political cycle, and then dedicated funds should be made available that would also support technologies for converting energy into heat.