The Power-to-Gas technology: a bridge between electricity and natural gas networks
Coordinated by GRTgaz in association with eight industrial partners, Jupiter 1000 Power-to-Gas demonstrator, will allow to store electricity under gaseous form in order to inject it into the natural gas transport network. As the first projects are currently being implemented in France, this technology feeds many expectations for its capacity to store big volumes of electricity while minimizing losses. In addition to energy storage, Power-to-Gas can also allow to value CO2 stemming from industrial installations located nearby via methanation and find potential applications in different sectors such as mobility or smart management of the energy networks.
I. Power-to-Gas processes and networks’ integration
The Power-to-Gas technology (that can be found under the acronym “P2G”) refers to the transformation of electricity into hydrogen (H2) through water electrolysis. This process allows to store electricity when its production is higher than network demand. In the electrolysis process, electricity is used to “break” water molecules (H2O) into hydrogen (H2) and oxygen (O). This hydrogen mode of production is not as spread as steam reforming process with fossil fuels[i] because of its higher cost. However, it uses “fatal” electricity (potential loss because of the lack of demand) generated by renewable energy sources, and does not produce CO2.
So, Power-to-Gas answers the intermittent nature of most renewable energies (wind and photovoltaic especially) by creating a storage solution for the electricity surplus.
Power-to-Gas appears as a technology at the junction between electricity and gas networks:
– Electricity conversion into gaseous hydrogen allows the opposite conversion from gas to electricity in order to match consumers’ demand when electricity production is not as high as the consumption on the network (Gas-to-Power).
– Hydrogen can also be injected in the transport/distribution network of natural gas, either directly, in restricted quantities (~6%), or after methanation. The synthetic methane obtained by the combination of hydrogen and carbon dioxide has the same properties as natural gas and can be injected massively into the network, without any volume limitation.
Thus, Power-to-Gas potential allows the electricity networks administrators to increase the network flexibility to insure the matching between energy supply and demand. In so doing, this technology creates exchanges between electricity and natural gas networks. Then, it also proposes tracks for the development of other sectors such as heat networks and sustainable mobility.
II. Power-to-Gas applications
To sustain the electric network
The French Programmation Pluriannuelle de l’Energie (PPE) published in October 2015, defines development targets for each electricity production sources. Concerning intermittent renewable energy sources, objectives to achieve in 2023 are ambitious: ground wind capacities will have to reach 15 GW (compared to 12,14 GW installed in March 2017) and solar sources are expected to reach 10,2 GW (6,85 GW in March 2017).
The intermittent nature of these energy sources rises an issue for networks administrators who balance energy flows so power production always matches demand. Currently, Power-to-Gas is the most accomplished technology to store massive volumes of electricity over a long period and so to avoid the loss of this “green” electricity.
To decarbonize of the natural gas network and local production
Hydrogen generated by electrolysis can be directly injected in the natural gas distribution / transport network (within the limits of 6 % of the forwarded volumes). This “renewable” gas then mixes with fossil gas transiting toward final consumers.
Hydrogen injection into the gas network can also come along with a phase of methanation. Methanation creates synthetic methane by capturing carbon dioxide rejected from a production site of biomethane, or by an industrial facility. This process allows to implement a closed-circuit, valuing CO2 by associating it with hydrogen gas from renewable electricity.
The local production of hydrogen and synthetic methane is also an answer to the French strategy of natural gas supply sources diversification. Importing almost all the natural gas consumed on the national territory, France energy security remains bound to the outer events influencing international exchanges. The local production of synthetic gas and biomethane could mitigate the risk of supply disruption.
To support sustainable mobility through its complementarity with NGV and/or electrical mobility with hydrogen
Transportation is the first oil consumption sector with 55% of the global demand. The average consumption has been increasing by 4% per year since 1990. Cost issues, environmental impacts as well as sanitary stakes bound to this dependency stimulate the need for alternative fuels. These new fuels are expected to drive the transportation sector towards a “sustainable mobility”.
“Clean vehicles” expression is used to qualify the means of transportation not relying on fossil fuels (or only partially). A vehicle fueled by hydrogen does not emit either CO2 or nitrogen oxide during its use.
Currently, two technologies rely on hydrogen to fuel vehicles:
– Hydrogen engine: An internal combustion engine uses the hydrogen as fuel. Dihydrogen (H2) “explodes” in dioxygen (O2), this reaction ending in the production of water (H2O) and in energy liberation. This energy is used to propel the vehicle. As a comparison, the combustion of a kilogram of dihydrogen produces three times more energy than a kilogram of gasoline.
– Fuel cell: The fuel cell produces some electricity by oxidation of hydrogen (stored in a reservoir) in an electrode coupled with the reduction of the oxygen (taken in the air) from a second electrode. The current generated powers an electric engine.
Nevertheless, hydrogen mobility is still remaining in the experimental stage in France. Fourteen supply stations are currently operational[ii] and forty are financed for a commissioning in 2018[iii]. One of the main obstacle to the massive deployment of this technology remains its cost, which is higher than the cost of conventional fuels. The average cost of a refueling station reaches approximately 1 million euros. Moreover, to be profitable, the installation should have a utilization rate included between 60 and 70 % of its distribution capacities. Furthermore, hydrogen vehicles for individuals have a cost twice as expensive as their equivalents vehicles propelled by thermal fuel, on average[iv].
In order to increase its deployment in the French trend of « sustainable mobility », the Natural Gas for Vehicles (NGV) leans on captive fleets (urban collective transports, garbage trucks, business fleets) and on heavy trucks. In August 2017, 60 supply stations (Compressed Natural Gas – CNG) were displayed in France. By 2023, the French Association for the NGV (AFGNV) aims to reach 250 stations, allowing natural gas to settle as a pillar of the “green” mobility dynamic.
Bio-NGV, which is biomethane used as a fuel for vehicles, strengthens the ecological interest of natural gas in the transportation sector. This fuel reduces carbon dioxide emissions up to 80% in comparison with commonly used diesel[v].
III. Power-to-Gas projects in France
About fifty Power-to-Gas projects are currently driven worldwide, Germany being the most active in the domain with several initiatives linked to this technology. In France, otherwise, hydrogen utilization and alternative fuel supply stations are mainly at the stage of demonstrators.
The deployment of these projects can be considered as a growth driver for the actors leading them: initiators of projects, Power-to-Gas specialists and industrial partners usually in association with public entities (research entities, institutions, associations and platforms, national agencies). According to their role and positioning on the various projects, these actors can stimulate and / or benefit from initiatives profitable to the whole French energy landscape:
– New products and/or services development: strengthening of NGV or Bio NGV, renewable gas guarantees of origin certification, distribution of a new gas NG-H2 through the existing natural gas network …
– Upgrading of innovative technologies: electrolyze, methanation, network management tools, production driving and hydrogen injection
– Hydrogen transportation through the network under the NG-H2 form
IV. Development of the French Power-to-Gas sector
In 2014, a study driven by GRTgaz, GRDF and the ADEME in collaboration with the association of consulting companies HESPUL – Solagro – E&E, focused on the hydrogen price trends. One of the key conclusions stated that hydrogen sector, with a production cost close to 100 €/MWh, would approximate biomethane purchase prices (between 45 €/MWh and 125 €/MWh, according to the installation size and methane final products). Nevertheless, such a cost would remain approximately three times higher than natural gas prices. According to the International Energy Agency (IEA) forecasts, in 2030, hydrogen sector would remain approximately twice as expensive as the wholesale fossil natural gas prices (methane prices would remain between 2,8 and 4 times higher)[vi].
Even though Power-to-Gas does not need any technological breakthrough (all the technical components are already available and efficient), the sector’s development would require a stage of processes’ industrialization as well as the implementation of a specific legislation and legal incentives in order to overcome the remaining profitability issues.
In a context of energy transition and strategic thinking on the French energy mix’ future, there is a strong interest from politics, scientists and economists on the Power-to-Gas related topics (storage, networks management, renewable energies’ integration). In 2017, the Power-to-Gas Club creation within the ATEE underlines such a commitment toward the development of this technology: the club aims to gather the actors from the sector and so, to support the projects’ deployment. The dynamism from this Club may stimulate the implementation of the necessary means to support the deployment of the sector.
[i] The steam reforming process the most spread process for the production of hydrogen. Although this method benefits currently from the economics factor, its cost remains higher than natural gas and requires the use of fossil energy sources emitting CO2 (natural gas, liquid fuels, coal).
[ii] Symbio, French deployment – 2017
[iii] Mobilité Hydrogène France – 2016
[vi] ADEME, GRTgaz, GRDF – 2014