The cost of domestic heat in the UK: Hydrogen vs Heat Pumps
Should the UK use green hydrogen for domestic heat or heat pumps?
In a recent post by David Cebon, he highlighted that half of the energy used to create green hydrogen would be wasted before it got to where it’s most needed. You need a large amount of untested storage and there might be emissions which negates the reason to use hydrogen in the first place.
But proponents focus on renewable energy being intermittent and suffering from wind droughts. Domestic heat is not something you can time shift and switch back on when it gets windy again. And the issue is existential, a visual of a shivering granny doesn’t sit well with politicians looking to avoid the front page of the tabloids.
So what’s the solution? Here’s the keynumbers on UK domestic heat.
What’s the problem?
The UK is warming up the world more than its homes! Natural gas like all fossil fuels, emits CO2 when you burn it and a lot more when you don’t in the form of fugitive emissions.
So why is the UK destroying the world?
Because it’s cheap and easy to use. The UK, like a lot of high latitude countries, needs a lot of heating in the dark winter months. From the below graph of hourly gas consumption, most of the gas is required in the winter months. It also needs to be highly dispatchable as consumers quickly change the gas boiler settings to counter the variable weather.
When this graph was produced in 2018, natural gas was 4p/kWh. Ofgem, the UK energy regulator estimates a typical household consumes 11,500 kWh of gas or less than ￡500/year. Even with recent increases to 7-9p/kWh, it’s still very cheap.
But the problem is the emissions. David Cebon estimates an annual consumption of 300 TWh of gas which would emit over 55 million tonnes of CO2. This is roughly 20% of UK per capita emissions.
To counter this, the UK government has enshrined net zero into law and emission free alternatives are required.
Can Green Hydrogen replace natural gas?
The fossil gas industry has touted green, clean hydrogen as a substitute that is able to re-use existing infrastructure, has a workforce that is used to moving molecules around while still providing the seasonal storage and dispatchability needed for the winter months.
But how much will it cost?
Green Hydrogen Costs
The above chart assumes 183 GW of nameplate capacity running for 39% of the time.
At this scale, land space and permitting become an issue. Offshore wind maybe the only option that can meet the 2050 deadline without getting bogged down in nimbyism. This has the benefit of higher capacity factors such as Dogger Bank Wind Farm which can run for over 60% of the time.
But electrolyser running time needs to be factored in and many developers oversize the renewables.
The SeaH2Land project proposed by Orsted is a good example, 2GW of offshore wind are required for each 1 GW of electrolyser. This means the electrolyser is better utilised but it’s the equivalent of wind going from over 60% capacity factor to 40%. ?
To get to the 300 TWh, we’re back to 183 GW of offshore wind and half that for electrolysers.
For storage costs, the Royal Society published a report where they recommended salt caverns. Using numbers from the H21 NE project, they had estimates of ￡325M for 1.22TWh or roughly 25p/kWh of hydrogen storage space.
A simple calculation of totalling all the construction costs gets to ￡650b, double it for financing charges and developer profit and divide this by the 300 TWh gets to about 20p/kWh
For transmission costs, this is kind of uncharted territory so we can use current gas transmission and distribution cost of 1p/kWh as a benchmark and then assume that it’s triple the cost of this due to the need for additional compression, better pipes etc.
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Add in supplier profit, ESG levies and VAT, the price is close to 30p/kWh or almost ￡4000/yr for the average household.
Direct Electrification with Heat Pumps?
Doing the same process with heat pumps, direct electrification loses 10% of transmission but heat pumps using a Coefficient of Performance of three means two free units of energy.
Looking at a site like Dogger Bank and there is a lot of intermittency. Storage is required so assume a simple rule of 50% used and 50% stored for later with a round trip efficiency of 50% on the stored part would mean about 30 GW is required. ?
But is this enough, should the system be designed for a 1 in 5 year event, 10 years or 100 years? It gets expensive very quickly and opens up the argument to green hydrogen.
Historically, long duration storage options involved some form of hydropower. But with the scale required, the UK may not have enough suitable sites to flood. Compressed Air Storage (CAES) including advanced options that better utilise heat would be ideal for 1-3 days storage but they are not useful for seasonal storage.
The other issue is that the real cost of storage is converting stored energy back into electricity. For example, Pacific Northwest National Laboratory, Grid Energy Storage Technology Cost report has a 1000MW/24hr compressed air system broken down into power (Turbine, compressors, BOP etc $1061/kW) and storage (cavern storage $6.11/kWh) or roughly 90% is the power cost and 10% is the storage cost. Adding in a mix of different storage systems would mean duplicate power systems and make it less economical.
The ideal scenario is to have only one form of storage that can handle intra-day to seasonal. For example, iron-air batteries are designed for seasonal and potentially the 40% poor round trip efficiency might be offset by not building multiple power systems.
Is this possible?
If you can meet storage needs with 100 hours, then heat pumps will cost about 10p/kWh or just a bit more than gas. Need more storage, it could get very expensive again, meaning granny cannot afford either option.
Couple of Notes!
?Energy and transport analyst, strategist, and advisor? Supporter of a sustainable future. The first aid provider for #hopium overdose
10 个月#hydrogen as a fuel is a square wheel. https://www.dhirubhai.net/posts/michael-sura-9a47511bb_hydrogen-hydrogen-hopium-activity-7150837735828705280-eqT3?utm_source=share&utm_medium=member_desktop
Head of Australia - Rondo Energy
10 个月Storing heat is far cheaper than storing hydrogen or electricity. It's also much more efficient than your assumption! Consider a simple tank of water, heated by the heat pump. Zero losses as the leakage of heat is still useful. An unpressurised tank of water with a bit of foam insulation is very cheap per kWh.
Managing director at ReSus Technology Ltd.
10 个月If you use green hydrogen for heating you have to produce enough hydrogen to meet your entire heating demand, plus losses, which needs roughly twice as much electrical energy to make it.. If you use hydrogen for power generation back up to provide 100% support for renewable electricity, which is used to power heat pumps you need to produce about 15 times less of hydrogen. In round numbers, you May need to provide about 10 percent of electricity from seasonal Energy (possibly hydrogen other molecules, and even atoms, are available) storage, worst case. Assuming average COP of 3 and boiler efficiency 90%, you only need 30% of electrical energy compared to using hydrogen, so that's about 33 x less energy. However, you've got about 50% or so efficiency loss converting the hydrogen back to electricity which gives you your 15x reduction in the amount of hydrogen required. However, this is a worst case scenario, so on average you’re probably looking at only half of this quantity of hydrogen typically required for storage.