Store energy in batteries, not hydrogen.

Hydrogen may be inefficient for many tasks, like:

  • Driving a car powered by green hydrogen uses about 2.3 times more renewable electricity than a car with a lithium-ion battery.
  • Generating electricity from green hydrogen with:
    • a gas generator uses about 2.3 times more electricity than pumped hydro, and
    • a fuel cell uses 1.4 times more electricity than the pumped hydro.
  • Cooking on a cooktop burning green hydrogen uses about 3.1 times more electricity than an electric induction cooktop.
  • Heating a house by burning green hydrogen uses about 6.8 times more electricity than an air conditioner.

So, using green hydrogen requires more renewable energy – and the building of more wind and solar farms.

Many people are trumpeting hydrogen as the future of energy and investing in the development of this future. At the same time, others say this hydrogen future does not make sense. I would like to believe the hype about hydrogen, but I’m concerned about this inefficiency.

The inefficiency of green hydrogen is due to the energy losses from (1) converting renewable electricity to green hydrogen, (2) compressing the hydrogen to store it, and then (3) converting from hydrogen back to electricity. The efficiency of these processes must increase to make hydrogen competitive; otherwise, avoid storing energy in hydrogen when you can.

Caveat: These figures are based on a brief consideration of the subject by one person and rest on detailed calculations, assumptions, and references described below.


Hydrogen cars: 33% efficient

Look at the efficiency of running a “battery car” versus a “hydrogen car” when you start with renewable electricity.

Energy using stepsBattery car efficiencyHydrogen car efficiency
Distribution: Get electricity to the car94%
Charge the car battery95%
Store the electricity in the battery95%
Electrolyser: Use electricity to make hydrogen gas76%
Compress hydrogen gas, store in a high-pressure tank & distribute89%
Fuel cell: Use hydrogen to make electricity54%
Inverter: Convert direct electric current into alternating current95%95%
Motor: Use electricity to move the car95%95%
Overall Efficiency77%33%
Efficiency compared to hydrogen car2.31

(The data comes from Shahan (2021), see the hyperlink in the References section)

To power a car using green hydrogen, you transform renewable energy in the five ways shown in the table:

  • run an electrolyser using renewable electricity to made hydrogen,
  • compress the hydrogen into high-pressure tanks, distribute it, and fill the car with it,
  • run the car fuel cell to use the hydrogen and generate electricity,
  • convert the direct current into alternating current, and
  • run the electric motor to move the car.

In each of these steps, you incur a loss of energy. The energy efficiency of each step is the “the useful energy output” as a percentage of the “the input energy”.

For a hydrogen car, 33% of the renewable electrical energy used to make hydrogen becomes the car’s useful energy of motion. The rest of the energy, 67%, becomes unwanted heat, sound, and movement.

You get the 33% “overall efficiency from electricity to motion” by multiplying together the efficiencies of the five steps. I explain this calculation further in the section “A simple example of an energy efficiency calculation”.


A battery car: 77% efficient

To run a lithium-ion battery car, you have two of the same energy transformations as the hydrogen car and three different transformations. In all, 77% of the original electrical energy becomes the car’s energy of motion.

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Conclusion: a hydrogen car is inefficient compared to a lithium-ion battery car:

  • a hydrogen car uses 2.3 times more electricity than a lithium-ion battery car. (77 divided by 33 = 2.3)
  • the electricity needed to drive a hydrogen car 33 km would drive a battery car 77 km,
  • a green hydrogen car needs 2.3 times more solar panels.
  • fuelling a green hydrogen car should cost 2.3 times more than a battery car.

This analysis suggests that you should store electrical energy in a lithium-ion battery rather than hydrogen.


A simple example of an efficiency calculation

Consider an unrealistic process consisting of two steps:

  • Step 1 is to cut a lump of butter in two, drop one half and throw it out, keeping the remaining half. The efficiency of step 1 is 50%.
  • Step 2 is the same as step 1. You take the remaining butter from step1, cut it in two, drop one half and throw it out, keeping the other half. The efficiency of step 2 is also 50%.
  • You now have only one-quarter of the original butter.

Now, arithmetic can get the same answer as common sense:

  • The overall efficiency is 50% multiplied by 50%
  • = 0.50 multiplied by 0.50
  • = 0.25
  • = One quarter.

Store energy: hydrogen & burn: 36% efficient

The company Australian Industrial Power plans to build a gas-fired generator at Port Kembla, initially fuelled by imported gas from a permanently moored storage vessel, but then by green hydrogen. The proposal is to generate renewable electricity, make green hydrogen, and burn the hydrogen to generate electricity again.

(Fortescue to burn green hydrogen in a gas generator at Port Kembla: Renew Economy: 5 October 2021)

This proposal is surprising as generating electricity by burning hydrogen is inefficient. Consider its energy efficiency:

Process Efficiency Source
Electrolysis: renewable electricity to green hydrogen 76%Shahan, 2021
Hydrogen storage95%Guided by Shahan
Gas generator: Burn hydrogen to get electricity 34 – 50%50%Albatayneh, 2020, p.671
Overall efficiency36%

So, the round-trip efficiency of taking electricity, converting it into hydrogen for storage, and then burning the hydrogen to make electricity again is 36%.

This 36% is a high estimate as I used; (1) the highest gas generator efficiency in the range 40-50%, i.e., 50%, and (2) an electrolysis efficiency of 76% (Shahan, 2021), not 70% (Barnard, 2018). Also note, Shahan (2021) put the efficiency of storage and distribution of hydrogen at 86%. Guided by this, I put the efficiency of storage alone at 95%.

See Barnard (2018): hyperlink in the references section.

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Store energy: hydrogen & fuel cell: 58% efficiency

Rather than burning the hydrogen in a gas-fired generator, using a fuel cell to generate electricity is more efficient.

Process Efficiency Source
Electrolysis: renewable electricity to green hydrogen 76%Shahan, 2021
Hydrogen storage95%Guided by Shahan
Fuel cell 60 – 80%80%Gencell, 2021
Overall efficiency58%


Regarding fuel cell efficiency: Gencell (2021) gives the specifications of three types of fuel cells that use hydrogen. The energy efficiencies range from 30 to 80%. (See the table at the end of the article). I used the highest efficiency of 80%. The high efficiency requires that the stationary fuel cells find a use for fuel cell heat. The theoretical maximum efficiency is 85%. Above, for the fuel cells in cars where you cannot use that heat, I used a far lower efficiency, 42%.

So, the round-trip efficiency of taking electricity, converting it into hydrogen for storage, and then using a fuel cell to make electricity again is 58%. This 58% is a high estimate of efficiency.

(Gencell (2021) Comparing fuel cell technologies: Retrieved October 2021: See Table at the end of the article)

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Store energy: Pumped hydro: 81% efficient

Australia has many suitable locations for pumped hydro, so compare the above ways of storing energy with pumped hydro generation. Pumped hydro generators store electrical energy by using the electricity to pump water from a low reservoir to a high reservoir. Then they run the water from the high reservoir through a turbine generator and back to the low reservoir when they want electricity again.

A typical round-trip energy efficiency of pumped hydro is 81% (Blakers, 2020).

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These calculations suggest that storing energy via pumped hydro is more efficient than storing via making hydrogen, even though the analyses include assumptions that favour hydrogen. Generating electricity from green hydrogen:

  • using a gas generator will use about 2.3 times more electricity than pumped hydro (81 divided by 36 = 2.3), and
  • using a fuel cell will use1.4 times more electricity than the pumped hydro (81 divided by 58 = 1.4).

The analysis suggests that we use pumped hydro rather than less efficient hydrogen storage.

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Store energy: Emerging technologies

Due to the energy inefficiency of hydrogen, hydrogen storage investment will be vulnerable to emerging technologies. Some challengers could be:

  • The company MGA Thermal, based in Newcastle NSW, is developing Miscible Gap Alloy blocks. These blocks could store energy from intermittent renewables to power existing coal or gas generators.
  • The company 1414 Degrees, based in Adelaide, is moving towards commercial-scale heat storage using molten silicon.
  • Form Energy is developing cheap, long duration iron-air batteries.
  • Mercedes-Benz is using solid state lithium-ion batteries in its eCitaro electric buses.

Injecting green hydrogen into town gas

In South Australia, AGN adds green hydrogen into town gas, distributing a blend of 5% hydrogen and 95% methane to homes. The following calculations indicate that this use of hydrogen is inefficient compared to using electricity for home cooking and heating.


Cook by burning hydrogen: 22% efficient

Compare cooking with hydrogen and an electric induction cooktop. First, work out the efficiency of using a gas cooktop burning green hydrogen.

ProcessEfficiencySource
Electrolysis: renewable electricity to green hydrogen 76%Shahan, 2021
Hydrogen storage95%Guided by Shahan
A gas burner heating water 31%Livchak et al., 2019, p 11
Overall efficiency22%

Cook using induction: 69% efficient

Now work out the efficiency of using an induction cooktop and pumped hydroelectricity.

As it may be possible to store the blended town gas, to compare like with like, I’ve assumed that the induction cooktop uses electricity from stored energy, i.e., from a pumped hydro generator.

Process Efficiency Source
Pumped hydro 81%Blakers, 2020
Induction cooktop: electricity to heat water 85%Livchak, 2019, p.11
Overall efficiency69%

Conclusion: Burning green hydrogen from the blended town gas on a gas kitchen cooktop is inefficient: it uses 3.1 times more electricity than an induction cooktop. (69 divided by 22 = 3.1)


Heat by burning hydrogen: 54% efficient

Compare heating a house with hydrogen and an air conditioner. First, work out the efficiency of burning green hydrogen from the blended town gas.

Process Efficiency Source
Electrolysis: electricity to hydrogen 76%Shahan, 2021
Hydrogen storage95%Guided by Shahan
A flued gas heater 70 – 80%75%Brakels, 2021
Overall efficiency54%

Heat with air conditioning: 365% efficient

Now work out the efficiency of heating using an air-conditioner powered by electricity from a pumped hydro generator.

An air conditioner (heat pump) heats a house by gathering heat from the external air and releasing the heat inside the house. An air conditioner can gather 4.5 times more heat energy than the electrical energy it uses, giving an efficiency of 450%.

Process Efficiency Source
Pumped hydro 81%Blakers, 2020
Air-conditioner: 300-600%450%Heating & Cooling, 2021
Overall efficiency365%

Conclusion: Burning green hydrogen from the blended town gas to heat a house is inefficient: it uses 6.8 times more electricity than an air conditioner. (365 divided by 54 = 6.8)


Putting hydrogen into town gas pipelines

The natural gas piped around Australia is mostly methane. Compared to methane, hydrogen has far less energy per unit volume, 3.3 times less energy. So, for the pipelines to carry the same energy, the pipes would have to transport 3.3 times the volume of gas, significantly increasing the cost of pumping town gas. Also, many pipelines would need larger diameter pipes, an expensive, long-term project. Another concern is that hydrogen can attack the structure of metal or polythene pipelines.


Hydrogen car in Asia using our hydrogen: 22% efficient

Consider making green hydrogen in Australia, liquefying it, shipping it to Japan, and then using the hydrogen to run a car. To transport hydrogen, it’s liquified by cooling it to minus 253 degrees C. This liquefaction uses about 30% of hydrogen’s energy: efficiency 70%

Process Efficiency Source
Liquefaction of hydrogen 70%
Shipping uses 5% of the energy 95%Unsourced
The efficiency of a hydrogen car33%From above
Overall efficiency22%


The efficiency of a hydrogen car driven in Japan powered by Australian green hydrogen is 22%.


Shipping ammonia overseas

Liquifying hydrogen requires so much energy. It is more efficient to (1) turn the hydrogen into ammonia, (2) compress and transport the ammonia, and (3) either use the ammonia or convert it back to hydrogen. I have not done these energy calculations.


Internal combustion engine: 21% efficiency

The well to wheel efficiency of a car considers:

  • energy used to extract the oil from the oil well,
  • energy used to refine the oil,
  • energy used to distribute the petrol,
  • energy provided by the petrol, and
  • the useful energy supplied to the car wheels to move the car.

The well to wheel energy efficiency of a petrol-driven car is between 11 and 27%. (Albatyneh et al., 2020, in the abstract) We have done well with low-efficiency fossil fuels for a long time, but for many tasks, we now have alternatives that are more efficient than both fossil fuels and hydrogen, so the hydrogen economy may not take off.


Making green hydrogen more competitive

Currently, the cost of producing green hydrogen is $5/kg, and the federal government says this cost needs to fall to $2/kg to make it competitive with competing fuels.

Bringing down the cost of solar panel generation can contribute to this cost reduction. However, to improve hydrogen’s competitiveness against batteries, you need to increase the efficiency of (1) electrolysers producing hydrogen from electricity, (2) storage of hydrogen and (3) the fuel cells generating electricity from hydrogen.

You could also reduce the cost of green hydrogen by paying electrolysers to slow production during periods of electricity scarcity. If we have large scale hydrogen production, then there will be a considerable ability to slow production. The electrolysers would be earning money by making electricity available to others, acting as virtual batteries.


Why is so much money going into hydrogen

The above simple energy calculations suggest that hydrogen is inefficient for:

  • storing energy,
  • powering a car,
  • generating electricity,
  • heating homes, and
  • cooking on a stovetop.

Companies like BHP, Fortescue, and Macquarie have made plans to produce green hydrogen. There are plans for 35 electrolysers, many of them with an enormous capacity.

(Australia has 38GW of green hydrogen in the pipeline, but major cost falls are needed: Renew Economy: 11 June 2021)

Surely these organisations know what they are doing.

In some regions, hydrogen may be the best alternative, e.g., where pumped hydro storage is impossible or where instaling electric vehicle charging is too difficult. Hydrogen does carry a huge amount of energy per unit mass, and filling hydrogen cars is quicker than charging electric vehicles.

Some authors are concerned that fossil fuel companies may be backing the hydrogen economy to (1) sell hydrogen produced from fossil fuels or (2) use their gas pipelines and sell gas.

I would like the green hydrogen economy to succeed, but I’d like to understand how it can compete given its apparent inefficiency.


The future areas of use for hydrogen

It seems that the inefficiency of hydrogen will limit hydrogen or ammonia use to:

  • energy export to places like Japan, South Korea and Germany,
  • hydrogen hubs (to avoid liquefying the hydrogen for distribution),
  • shipping & heavy freight transport,
  • the chemicals industry,
  • fertilisers,
  • refineries,
  • steelmaking, and
  • plane fuels.

(Separating hype from hydrogen: The demand side: BNEF: 16 October 2020: Liebreich)


Data Sources

Albatayneh, A. et al. (2020) Comparison of the overall energy efficiency of internal combustion engine vehicles and electric vehicles, Environmental and Climate Technologies, vol 24, no 1, pp 669-680: Retrieved from Sciendo Oct 2021.

Blakers, A. Stocks, M. & Lu, B. (2020) Australian electricity options: pumped hydro energy storage, Australian Parliamentary Library 20 July 2020

Barnard, M. (2018) What are the pros and cons of using hydrogen to generate electricity, from Forbes, 8 May 2018

Brakels, R. (2021) Air Conditioners Will Heat Your Home Cheaper Than Gas. Here’s Why. Solar Quotes, 23 August 2021

Heating & Cooling (2021) Australian Government, Dept of Industry, Science, Energy & Resources: Retrieved October 2021

Livchak, Hedrick & Young (2019) Residential Cooktop Performance and Energy
Comparison Study, Frontier Energy report, July 2019

Shahan, Z. (2021) Chart: Why battery electric vehicles beat hydrogen-electric vehicles without breaking a sweat from CleanTechnica, 1 February 2021


An overview of Australia’s progress towards renewable energy superpower


Updated 17 October 2021