“Power to Gas” uses renewable or low-carbon electricity to make hydrogen. The electrolysis of water to produce hydrogen and oxygen has existed almost since the “discovery” of electricity, writes Mike Parr.
Until the 1950/1960s electrolysis was the key method used to produce hydrogen which is an important feedstock for the production of chemicals such as ammonia which is, in turn, a key chemical in the production of fertilisers.
The growing availability of low-cost natural gas in the 1960s led to steam-methane-reforming (SMR) which uses natural gas as a feedstock to produce hydrogen more cheaply than electrolysis. However, SMR also produces CO2 and the situation on the cost for emitting CO2 is now changing as EU ETS prices for CO2 rise (now circa Euro20 – 25/tonne) making electrolysis, once more cost competitive.
Once EU ETS prices hit Euro30/tonne, there will be a good business case for the use of hydrogen from electrolysis, rather than SMR. However, this “good business case” rests on the availability of low-cost and low carbon electricity. For the business case to “work” electricity needs to be priced around Euro25 – Euro30/MWh. In general terms there are two source for such electricity: renewables and nuclear. This begs the question which industrial groups will take the first steps to use renewables or nuclear to supply “zero-carbon” hydrogen to industries that may find it both economically attractive (why buy “expensive” SMR hydrogen when “renewable” hydrogen is cheaper?) and politically expedient (we have decarbonised our production process and product by moving to “low-carbon” hydrogen)
However, the “story” with respect to hydrogen does not finish with relatively niche markets such as ammonia. Europe needs to widely de-carbonise its heating sector (mostly powered by natural gas). Heat in Europe uses around 6300 TerraWatt hours of energy (2017). By contrast electricity consumption is around 3000 TWh (with perhasp 15% of thus being used for heat). Natural gas accounts for around 35% of the 6300TWh and much of this is used for space heating in the built environment. Furthermore, natural gas is cheap and the gas network is pervasive in most EU towns and cities.
If Europe is to de-carbonise to any meaningful extent by 2050, natural gas will have to be replaced by some other gas. This could be hydrogen. Data obtained by PWR suggests that much of the low pressure gas network in the EU i.e. the part of the network connecting to households, offices and medium sized gas users, is hydrogen-ready. Although the energy density of hydrogen is one third that of natural gas, the problem of supplying enough hydrogen down the existing low pressure network can be overcome by renovating buildings to make them more energy efficient. In depth energy renovation can reduce heating demand by around 50% – which means that one would need 50% less natural gas to heat a building – which in turn reduces the relative need for hydrogen vs natural gas to 1.5 to 1.
Open questions remain. Electrolysers work best with a steady supply of electricity which points to sources such as nuclear. Funding of MW-class or GW-class electrolyser systems would be needed. Availability of large-scale electrolysers is less of a problem, Thyssen-Krupp have already developed a 300MW system.
Taking one example of a possible producer and a possible user: a 1000MW nuclear station in Ukraine supplying electrolysers could produce 157,000 tonnes of hydrogen per year. This has a heating value of around 40kWh/kg.
In the residential sector, normal houses have a heating demand of around 20,000kWh per year. A house that has been properly energy renovated will use 10,000kWh/year. So the hydrogen output from of a 1000MW nuclear station coupled to electrolysers would be sufficient to heat using zero-carbon energy around 628,000 households.
Poland, in common with many EU countries has a large stock of poorly insulated houses many of which use coal for heating. The country is also under great pressure to reduce CO2 emissions. A programme that renovates the housing stock coupled to a move to hydrogen-based heating would deliver both warm comfortable homes to Polish citizens whilst meeting EU demands for CO2 reductions. It would also usefully engage existing (Ukraine) nuclear assets in the move to a hydrogen economy.
A major advantage of gas (hydrogen or natural gas) is that it can be easily stored in very large (terawatt hour) quantities. Electricity cannot. For example, Germany at any point in time has in the gas system about 220 TWh of gas. This is the equivalent of 40% of Germany’s annual electricity consumption.
In such a scenario, the gas “market” would be a function of the electricity “market” and vice versa with gas delivering a functionality which electricity lacks – storage.
The Author, Mike Parr, is the Technology Editor for EU Political Report.
