Producing hydrogen, ammonia and methanol requires an enormous amount of energy – wind and solar just don’t cut it on their own, argues Giulio Gennaro, technical director at atomic propulsion firm, Core Power.
A lot of consideration is currently being given to hydrogen as a means to decarbonise shipping. While hydrogen can be used only onboard very low powered / short-ranged vessels due to storage and handling issues, ammonia and methanol derived from hydrogen could see a widespread use. Both these electro-fuels have shortcomings, as with most energy sources, but they could be a suitable compromise. It is true that both of these fuels require a lot of tank space, but when obtained from green hydrogen produced by cheap solar photovoltaic (PV) or wind they would be either carbon free (ammonia) or carbon neutral (methanol). The total lifecycle greenhouse gas emissions and health, safety environmental emissions would be fairly low and diesel engines have the unparalleled ability to run on possibly every kind of fuel.
So, have we finally found the silver bullet to solve shipping decarbonisation? Not really.
Green electrofuels such as hydrogen, ammonia and methanol, as opposed to fossil fuels, are energy carriers. This makes their production an extremely energy hungry process. In fact, more energy is required to produce one ton of hydrogen than the energy that can be carried in the hydrogen itself. If that production energy is not clean, or is not durable, we’re not really helping the cause.
The idea of producing cheap, green electrofuels at industrial scale with surplus energy only from variable renewable energy sources (VREs) is a mirage. The reasons are simple:
- Cheap energy surplus will no longer be a surplus, and it will no longer be cheap as soon as there will be a need for it.
- The total system levelised cost of energy (LCOE) of offshore wind, the most vouched for VRE, is not cheap at all.
- VRE, by definition, are characterised by low capacity factors and they are not dispatchable (meaning they do not supply energy on demand, but only when they can). As a consequence of the low capacity factor VRE need to be massively over deployed in order to provide the necessary amount of energy, and that would still not be sufficient, as being non dispatchable, a massive energy storage infrastructure is also needed to ensure a steady and secure power supply. And this energy storage, whether that is batteries, thermal or pumped hydro, has consequential severe repercussions on LCOE, use of resources, emissions and other external factors.
In order to understand the implications of the above it should be recalled that:
- About 10 MWh are required to produce one ton of green ammonia.
- IMO GHG Study 2020 estimates for 2018 a total HFO equivalent consumption by global shipping and fishing fleets of about 339m tons. Considering fleet growth and increase in propulsion efficiency it can be estimated that by 2040 more than 425m tons of HFO equivalent will be needed, equating to about 1bn tons of green ammonia equivalent.
The above can then be combined with the figures provided by the US Energy Information Administration (EIA) in respect of a total system that combines the levelised cost of energy and the levelised cost of storage, for new resources entering service in 2040, and presented below:
The final total system LCOE, relevant to achieve 90% capacity factor, necessary to power a large-scale industrial production of green ammonia are as follows.
The actual additional power generation then needed to produce green ammonia to cover one third of the needs of shipping, i.e., about 335m tons per year by 2040, can be assumed as follows:
The conclusions are straightforward:
- The challenge in decarbonising shipping by means of green electrofuels ultimately lies in the durable, low-cost production of such fuels in large quantities.
- VRE alone is not an option for such a large-scale industrial production due to the much higher power capacity needed, and the much higher total system LCOE.
- Production at such a large industrial scale requires dispatchable power generation, not intermittent power.
- Whatever energy source is used, the power generation capacity which will need to be deployed will be massive.
- Advanced atomic power, from molten salt reactors would be ideal in this respect thanks to the low total system LCOE and the high-capacity factor.
- VRE may be used alongside advanced atomic to supplement and provide ancillary power supply.
- VRE could be used alone only for extremely small scale / local production with negligible impact on the global bunkering industry.
These conclusions are cascading across our industry. In a recent poll of 150 senior executives from maritime transportation, 90% agreed that energy density matters the most. 84% of those polled said we would see floating assets using advanced atomic power to produce zero-carbon fuels in the future, and when finally asked if advanced atomic is a viable solution to decarbonise the shipping sector, 47% agreed and 42% strongly agreed. Just 6% disagreed and 5% strongly disagreed.