Enterprise explains: How to move renewables. Renewable energy is a focal point in the clean energy transition, but achieving net zero by 2050 requires a tripling of green energy capacity by decade’s end, according to forecasts published in the 2023 update to the International Energy Agency’s (IEA) Net Zero Roadmap report (pdf). Trade in renewables is necessary to ensure countries’ access to clean energy and to reduce costs by bringing to bear economies of scale and market mechanisms. But how can renewable energy be moved? Surplus renewable energy can be transformed into hydrogen via electrolysis, and several vehicles have been proposed as enablers of cost-effective transport of hydrogen in bulk over long distances for trade purposes.

Why hydrogen? Hydrogen trade is more efficient than cross-country power lines: Carrying energy over power lines yields some waste as part of that energy is emitted as heat. The proportion of the energy that is lost-in-transit grows as power lines get longer and the effect adds up, according to analysis by the Conversation. This means that although power grids are practical for renewable energy trade over short distances, they are inefficient for long distance trade.

The methods: The International Renewable Energy Agency (IRENA) ’s Technology Review of Hydrogen Carriers report (pdf) looks at four workable carrier options: ammonia, liquid hydrogen, and liquid organic hydrogen carriers (LOHC), are shipping pathways; while pipelines — either newly installed or retrofitted from natural gas networks — present a fourth overland alternative. The hydrogen carriers proposed may — to varying degrees — be integrated with the trade and storage infrastructure underpinning today’s fossil fuels trade.

Hydrogen can also be used to clean up sectors that have proven difficult to decarbonize in the past, including the steel, iron, and chemical industries, as well as long haul transport, such as ocean and road freight, and air travel, CNBC explains (watch, runtime: 15:25). Green hydrogen refers to hydrogen produced from renewables, as opposed to gray or blue hydrogen which are produced from fossil fuels and entail carbon emissions. Surplus renewable energy during times of high output and low demand can be diverted to the production of green hydrogen via electrolysis.

Angling to get in the game early, global powers are pumping substantial investments into green hydrogen projects: The EU is looking to launch a hydrogen bank to manage investments that could run up to EUR 471 bn, according to a draft document picked up by Reuters in March. Japan is also planning to deploy investments worth USD 107 bn over a 15-year period, Reuters reported separately. China, the US, and other world powers are pursuing their own initiatives. Closer to home, Saudi Arabia’s NEOM megaproject plans to roll out substantial green hydrogen production capacity.

The catch: hydrogen is flammable and difficult to handle, presenting unique challenges in terms of safety. It also has a low volume energy density and must be packed at high pressures for meaningful storage and transport to take place. The extreme pressures and temperatures required to store and transport hydrogen imply significant energy outlays, making hydrogen trade less efficient and capital intensive.

With these challenges in mind, renewable energy analysts are weighing options for pathways to kick-off hydrogen trade: Despite the manifold advantages hydrogen presents, new technologies must be rolled out to enable transport of the fuel in bulk so that it can be traded in the same way fossil fuels are today. There are costs involved in converting the fuel into a transportable medium, moving it, and reconverting back to hydrogen at the importing destination. To this effect, the different carriers proposed for hydrogen trade each come with their own pros and cons.

Ammonia has a head start as a hydrogen carrier because it is already produced and traded on a global scale: Some 120 ports worldwide already have infrastructure that can be used to store and trade ammonia, IRENA’s report noted. The caveat: most ammonia produced today is sourced from natural gas and coal, meaning that certification procedures must be introduced to separate green ammonia in trade.

Another advantage inherent in the use of ammonia as a hydrogen carrier is its multiple end-uses. Aside from use as a hydrogen carrier, the compound can also be used in fertilizers, as an industrial feedstock, and — subject to innovations in engine technology — as a maritime fuel, the report explained.

Ammonia is projected to be the go-to solution for decarbonizing shipping: As ammonia two-stroke engines come into play and the use of oil as declines, ammonia’s use as a maritime fuel is projected to stand at 6% in 2030 and 15% in 2035, according to the IEA report. By 2050, ammonia’s use as a maritime fuel is slated to stand at a full 44% granting it “the biggest stake in energy consumption for international shipping”, the IEA says.

Ammonia’s most significant drawback is a hefty energy penalty, but there’s more: A substantial energy outlay (equivalent to 12-26% of the hydrogen carried) is required at the ammonia synthesis stage, according to numbers cited in the report. Even more energy (13-34%) is required for hydrogen reconversion, or “cracking”, at the importing destination. Ammonia is also toxic and corrosive, requiring special protocols and equipment for its handling. Finally, hydrogen that has been decoupled from its ammonia carrier may need further purification.

A liquid hydrogen supply chain is also starting to take shape: Liquified hydrogen is commercially available today, albeit at a much smaller scale than ammonia. Marine trade in liquid hydrogen has been demonstrated, with Japan’s Suiso Frontier — the world’s first liquid hydrogen carrier — making its first shipment early this year, Bloomberg reported. Aside from existing infrastructure pilot projects, liquid hydrogen benefits from a simple reconversion process that is not capital intensive and does not require significant energy outlays.

On the downside: It also suffers from a high energy outlay + storage challenges. Liquid hydrogen requires temperatures around -253 degrees celsius, and the energy required to achieve such temperatures accounts for 30-36% of the hydrogen supply, according to figures cited in IRENA’s report. However, if today’s pilot projects are scaled up and new technologies are innovated, the energy outlay may potentially decrease to 15%. The equipment required to achieve and maintain cryogenic storage also requires large investments in capital, the report noted. Another drawback to using liquid hydrogen is boil-off, which wastes 0.05-0.25% of hydrogen stores per day during shipping and storage.

To put things in perspective: The same amount of energy provided by liquefied hydrogen that is carried on two and a half ships can be carried on just one ship of the same volume in the form of liquefied natural gas, according to BloombergNEF.

On the other hand, liquid organic hydrogen carriers (LOHC) are compounds that can be stored and traded using the same infrastructure available for fossil fuels today. LOHC carriers can be “recycled” and used multiple times to load and offload hydrogen, albeit with a 0.1% loss rate per cycle, according to numbers cited in the report. Due to the fact that LOHCs are mostly oil derivatives and are at a liquid state in ambient temperatures, they can be stored and traded using the same infrastructure employed in the fossil fuels trade today with only minor adaptations. Unlike liquid hydrogen, LOHC storage and transport does not incur boil-off costs.

But, you guessed it, there’s a high energy outlay at the reconversion stage of the LOHC value chain: Dehydrogenation — or the decoupling of hydrogen from its LOHC carrier — requires temperatures in the range of 150-400 degrees celsius. This implies 25-35% energy consumption at the importing destination, according to IRENA’s report. After conversion, the hydrogen must also be purified and pressurized, implying further energy outlays.

Another disadvantage to LOHCs are their low hydrogen density, whereby only 4-7% of an LOHC cargo's weight is hydrogen. Despite pilot projects for hydrogen conversion and reconversion via LOHCs, existing initiatives require significant scaling in order to achieve economies of scale and allow tradable volumes.

Pipelines present an attractive overland option, especially in regions where natural gas pipeline networks already exist: Hydrogen storage (in salt caverns and other reservoirs) and transport via pipelines has already been successfully demonstrated at a commercial scale, with successful pilot projects in North America, the UK, and the Netherlands, the report noted.

By the numbers: Pipelines are particularly attractive for projects involving large volumes and short distances, with the material costs of expanding the capacity of a pipeline lower than the actual pace at which the capacity increases, according to the report. Natural gas pipelines can — on a case-by-case basis, depending on the materials used — be retrofitted to carry hydrogen, thereby driving down costs by 65-94% in regions where such networks exist, according to the report.

But not all regions have pipeline networks: Most natural gas pipeline networks today are limited to North America, Europe, Russia, and eastern China, meaning that only those regions can benefit from pipeline retrofitting, the report indicates. Another significant drawback to pipelines is that project costs have a linear relationship to distance and quickly become uneconomical outside of regional spans.Storage in a reservoir also carries its own risks of losses and contamination, the report explained.