Dr Rory Monaghan, NUI Galway, MaREI and GenComm
Right now, Ireland is the world’s leading producer of onshore wind energy. The country’s installed capacity of over 4 GW produced nearly 40% of all electricity demand in the first half of 2020. More than 8 GW of wind will be needed by 2030 if Ireland is to meet the targets of the 2019 Climate Action Plan. More recent announcements, including the Coalition’s Programme for Government target of a 50% reduction in greenhouse gas (GHG) emissions by 2030, and this month’s proposed strengthening of the EU Green Deal to 55% GHG reductions by the same year, mean that 8 GW is only the starting point of our ambitions.
The obvious next step for Ireland is to turn our attention offshore. For a brief period in the mid-2000s, Ireland was an offshore wind pioneer, with the Arklow Bank wind farm operating what were the world’s largest offshore turbines. Since then, progressed stalled. Until now.
Over 4 GW of offshore wind is in the pipeline to the east in the Irish Sea and the south in the Celtic Sea. This is without considering the near limitless offshore wind energy potential off the northern and western coasts, accessible using floating wind technologies. Initial estimates of the technically exploitable wind capacity start at 50 GW, with much higher capacity factors than the 30-35% commonly achieved onshore. These numbers dwarf Irish electricity demand, even if we electrified every aspect of energy use. But the headline numbers hide the fact that long-term, high-capacity storage will be needed, as will the infrastructure to transmit these enormous quantities of energy.
Green hydrogen, which is produced by water electrolysis powered by renewable electricity, has the potential to provide not only energy storage and transmission at scale, but also the energy system integration needed to link green electricity to sectors that will be very difficult to decarbonise with direct electrification, such as heavy duty transport, industrial heat, shipping and aviation.
But could green hydrogen go one step further? Could Ireland become a green fuel exporter?
One route to export our renewable electricity resources is electrical interconnection. The largest interconnectors proposed for Ireland are in the 1 GW range, giving the country flexibility and security into the medium term. But if we are to truly exploit our offshore potential, what is the right energy carrier to transform Ireland into the Saudi Arabia of renewable energy?
Green hydrogen is under investigation as a medium to trade renewable energy internationally. In Ireland’s case, this could be done in two ways, by gas pipeline or by ship. Ireland’s gas interconnection with Great Britain can transfer natural gas from east to west at a rate equivalent to over 5 GW of thermal power. If the technical challenges of handling high hydrogen concentrations in steel transmission systems and enabling high rate two-way flow in the interconnector can be addressed, this critical piece of infrastructure could provide a ready route to the British market.
But to benefit from the scale of offshore renewables potentially available in Irish waters, we need export routes that extend beyond our near neighbours, which means maritime shipments of hydrogen. Despite being a difficult gas to handle, there are several options for transporting hydrogen by ship, including liquefied hydrogen (LH2), ammonia (NH3) and liquid organic hydrogen carriers (LOHCs).
LH2 bears many similarities to liquefied natural gas (LNG), in that it a gas, in this case hydrogen, is cooled to below -253 oC, at which point it becomes a high-density liquid with volumetric energy density 600-700 times that of hydrogen at atmospheric conditions. It is shipped as a liquid and re-gasified at the receiving port, ready for use as pure hydrogen. But this comes at a loss of 25-35% of the hydrogen’s energy content in the liquefaction and re-gasification processes.
An alternative is to combine hydrogen with nitrogen from the atmosphere to make ammonia (NH3), which liquifies at -33 oC. This process is well established in fertiliser manufacture but still costs 7-18% of the hydrogen’s energy. NH3’s volumetric energy density is 70% higher than LH2, making shipment more efficient. However, the process of extracting hydrogen back out of NH3 at the receiving port can cost up to an additional 20% of the hydrogen’s energy. One way to avoid this would be to use the NH3 directly in chemical industries or engines.
NH3 is toxic, so another alternative is LOHCs. This process involves chemically bonding hydrogen to a high-density liquid for shipment. At the receiving port, the process is reversed, and pure hydrogen extracted, with the LOHC ready for reuse. Many LOHCs are non-toxic and all are liquid at atmospheric conditions, meaning that current oil tankers could possibly be repurposed. Their volumetric energy densities broadly span the range between LH2 and NH3. But the laws of thermodynamics never allow a free lunch and current LOHCs incur overall penalties of 35-40% of the hydrogen’s energy.
So there is no perfect hydrogen export solution, but the International Energy Agency projects that through research, the energy penalties for LH2, NH3 and LOHCs could be reduced by 30-50% in the medium term. Some hydrogen producers are not waiting around. In April 2020, the AHEAD project (https://www.ahead.or.jp/en/) made the world’s first transoceanic hydrogen shipment 4,000 km from Brunei to Japan using containerised tanks of LOHC. The HySTRA project (http://www.hystra.or.jp/en/) launched the world’s first purpose-built LH2 carrier, Suiso Frontier, in December 2019. It will ship hydrogen 9,000 km from Australia to Japan.
But there is still time for Ireland to steal a march on the international competition. Both the AHEAD and HySTRA projects produced hydrogen from fossil fuels. While those projects’ end uses of hydrogen will be emission-free, no one has yet demonstrated an international green hydrogen supply chain. What’s to stop Ireland, with our world-beating offshore resources, from leading?
Dr. Rory Monaghan is the Director of the Energy Systems Engineering Programme at NUI Galway. He is a Principal Investigator in the NUI Galway Ryan Institute for Marine, Environment and Energy, and a Funded Investigator in MaREI, the SFI Research Centre for Energy, Climate and Marine. Rory leads the Long-Term Effects Work Package of the GenComm project to demonstrate green hydrogen in communities and founder of the Community Hydrogen Forum.