Staying warm without warming the planet!

Whether it’s “The battle of the radiator” or “Things are getting heated”, the press are striving to outdo each other when it comes to finding the wittiest headlines as they report on the negotiations that are going on behind the scenes as France attempts to draw up its new environmental building regulations. These regulations called  RE 2020 will notably define the prescribed method of heating for new builds. Debate is raging between the proponents of an all-electric solution and those who swear by gas, each side hoping to influence the final decision in its favour. But what exactly are the ins and outs of the matter at hand?

Over the last 30 years, heating performance has improved significantly as oil and coal have gradually been replaced by natural gas and electricity, as well as with the shift to producing electricity using nuclear energy, hydroelectric power and natural gas. According to the Ademe, emissions from heating have been divided by three since 1975 for an equivalent area, but at 400 terawatts-hour, heating still accounts for a quarter of France’s final energy consumption  It is therefore a key sector for achieving carbon neutrality.

Today natural gas and electricity are by far the main energies used for heating (see graph below), however electricity is not a primary energy, which means it is not directly available in nature. As electricity is an energy vector that results from the transformation of primary energies (natural gas, uranium, wind, solar radiation, etc), studying the primary energy sources used to provide electricity for heating shows a completely different picture. Although nuclear energy is predominant accounting for almost 50%, there is still a considerable part of fossil fuels in the mix.

A question of balance

The place of the various energies in tomorrow’s energy mix is therefore not so much a question of either natural gas or electricity, but rather a question of balancing different primary energies. Some renewable resources can, by nature, only be converted into electricity (wind, photovoltaic), whereas others, such as renewable gases and solar thermal energy (STE), can be used directly for heating. Electric energy does however have its limits when it comes to coping with daily and especially seasonal demand variations. The difficulty for the electrical system is to be able to start up electricity generation plants usually intended for use in winter and to ensure that the size of the network is sufficient to respond to short peaks in demand.

Let’s do a little maths. In 2019, the peak energy demand of buildings was estimated at 280 gigawatts (85 GW of which were supplied by the electricity grid) and their lowest energy demand was 80 gigawatts. If we were to imagine a hypothetical situation in which every building used electric heating, 200 gigawatts would have had to be kept in reserve in 2019 and used solely to respond to winter peak demand. This amount is the equivalent of 120 EPRs or 250 state-of the- art gas-fired power stations, which would then have to be shut down during the summer.

In the light of this, what route seems the most advantageous if we are to achieve carbon neutrality by 2050? We must begin by attacking the root of the problem, which is the level of winter peak demand, starting by rapidly and drastically reducing the energy demand of buildings. The fight to reduce heat leakage has been ongoing for several years but it is time to step up our efforts.

The second line of attack focuses on heat generation systems. If the latter rely on controllable resources - whether these resources are renewable (biomass, renewable gases) or low carbon such as an EPR nuclear plant – they must be as efficient as possible. In addition, solar, wind and hydropower will need to be backed up by sufficient storage capacity. Less controllable means of production are of little use in responding to changes in demand, in particular winter peak demand. The different storage solutions (each of which has its advantages and disadvantages) include batteries (whose environmental performance may be questionable), mechanical storage, thermal energy storage (in water or other more complex materials), and storage in the form of hydrogen, which is considered to be a renewable gas if generated with renewables.

The next question is the share of each of these controllable resources in the future energy mix, which is where the real debate on the place of electricity and gas in heating lies. The question can be rephrased as follows: “What are the most appropriate means of heat production to respond to winter peak demand and where are they situated?"

We need to decide between controllable, centralised means of electricity production and more decentralised ones that are closer to the end-user and which make the most of short, circular cycles (electric heat pumps coupled with a system using renewable gas, solar energy coupled with thermal energy storage, the use of waste heat, etc.). This can be on a regional level with energy communities based on existing networks, or on the scale of one or several buildings with hybrid systems that call upon controllable, carbon neutral means of production to provide extra energy as necessary.

Three levels

Each of these levels (centralised, regional and building) has its advantages and disadvantages which can be summed up as follows: the more powerful (and therefore the more centralised) production is, the easier it is to control and manage from a technical standpoint. On the other hand, it is less energy efficient because of the losses during the transformation of one form of energy into another. Arbitrating between the relative roles of each level is complex and, while it is a burning issue of current interest, it is essential not to lose sight of the fact that putting all one’s eggs in one basket (often all-electric) without allowing for resilience and evolution, means risking failure. In order to reach zero carbon, it is vital we keep all our options open, work at every level, not hide carbon emissions in centralized electricity production, and finally, aim to achieve energy efficiency as well as economic efficiency. This is what the teams at ENGIE are working toward. Can you see the headline : “An alliance for virtuous heating”? 

Written by:

Benjamin Haas, ENGIE Lab CRIGEN and Mures Zarea, ENGIE Research.