By Peter Duffy, President of the Irish Energy Storage Association
Energy Storage is the bridge between supply and demand. While we may think of it as a new concept, we actually encounter it every day in our fossil-fueled lives when we convert the energy stored within the coal, oil and gas; what is new is that we are faced with a new paradigm namely that energy sources and supply chains, energy forms at the point of use and energy storage will all be very different in the future. Today we fill the tanks in our cars, trucks or buses from filling stations, we power our industrial facilities and power plants with natural gas, oil or coal – all with well-developed and reliable supply chairs including storage. These storage methodologies and facilities have been developed over the past c. 70 years but unfortunately we don’t have a further 70 years to implement a new energy regime – more likely we have less than a decade to get the building blocks in place. In short, the future will be very different.
Fig. 1: Primary energy demand per sector, region and fuel (BP, 2019)
The planned/expected global shift away from fossil fuel energy supplies to renewable energy sources – largely wind, solar and ocean that are intermittent and unpredictable, is the key driver for energy storage. If we could switch on/off the wind and bright skies at will – which we cannot do – there would be little need for concern as the focus would be on reliable supply chains for distribution and storage of energy at the point of use.
While this article is directed towards Ireland, many of the issues raised are common to energy storage across all economies whether highly developed or not. The article contends that short and medium-duration energy storage needs have been largely cracked – battery & other storage technologies are well developed although considerable room for improvement remains – the real challenge for the future in moving progressively away from dependence on fossil fuels between now and 2050 as required under Climate Action targets is the large scale longer-term security of energy. This has to be an issue of huge concern not just for Ireland but all European countries and around the globe.
In the past two years Ireland has increased its renewable electricity target from 40% in 2020 to 70% in 2030 (70/30). With the commitment to achieve a decarbonized economy by 2050 it seems reasonable that at this early stage we should move beyond that timeframe and tentatively set the electricity renewable targets as 90% for 2040 (90/40) and 100% for 2050 (100/50). Electricity at c. 21% is the smallest component in Ireland’s annual energy consumption with heat at c. 37% heat and transport at c. 42% transport.
With regard to transport, Irish Government policy in recent years is to encourage/support the switch from diesel and petrol cars to electric vehicles, which are likely to be powered by Lithium Ion batteries (BEVs). However, the question of how heavy-duty transport will be powered in the future needs to be addressed at an early stage e.g. trucks, buses, trains and agricultural tractors. The likely solution will be green hydrogen powering these Fuel Cell Electric Vehicles (FCEVs). While Ireland has reasonable solar resources its wind resources are the envy of many countries. There is great potential to develop large-scale off-shore wind on the west and south coasts, which in turn could supply large-scale electrolyser capacity to produce green hydrogen on a grand scale. This could then be fed into the existing/upgraded gas grid for transmission to the load centers or storage facilities, or distributed throughout the country to ‘filling’ stations or exported in bulk tankers into the global commodity market.
Fig. 2: Share of renewables in capacity additions per region in 2018-2040 (IEA, 2018)
The heavy-lifting in transitioning from a fossil-fueled economy to one which is renewable-based must be done over the coming decade – the ‘30s and ‘40s will be largely about enhancing and scaling up but the fundamental changes and infrastructural requirements to enable a renewable-based economy must be faced over the coming decade. From large scale wind generation (primarily off-shore) to HV grid connections, electrolyser and green hydrogen infrastructure to facilitate distribution, storage and export, all must be put in place if we are serious about achieving 2030 Climate Action targets. With enormous wind generation potential on the west and south coasts, and well-developed docking facilities in the Shannon Estuary’s deep water coupled with good electricity grid infrastructure, Ireland’s Shannon region potentially has a glittering future for a green hydrogen economy. However, as the global pace in energy transition is about to pick up, it is time for Ireland to jettison the slippers and to don the running spikes.
Energy storage will be the bridge between supply & demand. The planned/expected global shift away from fossil fuel energy supplies to renewable energy sources – largely wind, solar and ocean that are intermittent and unpredictable, is the main driver for energy storage. If we could switch the wind and bright skies on and off at will – which we cannot yet do – there would be little need for longer-term storage but short and medium-term storage would still be required. So, while renewable energy sources are intermittent and unpredictable, customer demand in developed countries across electricity, transport and heat are quite predictable both across the daily peaks and valleys and throughout the seasons. Flexible demand, particularly through aggregation of smart appliances, can play a role, but to ensure economies can grow and develop in a planned and smooth manner, and that citizens can enjoy a degree of certainty in life this supply-demand must be bridged. The solution to this problem is energy storage across different timeframes – short, medium and long – providing energy security at the point of use in small, medium and large quantities
These timeframes will be subject to different definitions depending on different economies/countries; however, for the purposes of this article we define short as 0 to 20 minutes, medium as 20 minutes to one day and long as 1 to 14 days and beyond.
To a large extent batteries, flywheels, ultra-capacitors, pumped hydro, compressed air and thermal storage are all developed to a point where short and medium energy storage needs can be satisfied. However, huge improvements are still needed through further development of these storage technologies including energy density, longer asset-life, greater recyclability of storage materials and significant cost reductions.
Fig. 3: Contribution of flexibility for RES penetration in Europe by 2050 (Bloomberg NEF, 2018)
The Real Energy Storage Challenge for the Future
It is my contention in this article that with short and medium energy storage needs having been largely cracked, the real challenge for the future in moving progressively away from dependence on fossil fuels between now and 2050 is the large scale longer-term security of energy. This has to be an issue of huge concern not just for Ireland but all European countries and beyond.
Batteries, flywheels, pumped hydro, compressed air and thermal are all unlikely to be of mega-capacity to provide energy security over several days to 2 weeks and beyond. Hence some other form of long-term storage is needed. The contention in this article is that large scale surplus renewable energy can be stored by conversion to green hydrogen for transport, heat and industrial use AND for long-term storage employing a range of measures including possibly depleted gas-reservoirs, aquifers, salt caverns, disused mines, green hydrogen storage terminals and to a lesser extent in the national gas grid itself. Of course the geology and natural features of different countries with respect to those will vary greatly. These points are developed further below.
Need for Longer-term Storage
The gas industry in Ireland & UK historically relied on fuel switching from gas generation to coal/oil in the electricity generation sector to manage gas supply/demand issues. It is expected that this fuel switching capability will be gone on both islands in a relatively few years, due to coal and HFO plants taken out of commission. This points to an urgency in finding an alternative fuel source – perhaps green hydrogen.
An examination of historical weather patterns and other studies in Belgium and Germany have shown that as Europe as a whole increases renewable generation, Europe is at risk of serious disruption due to periods of low Wind & Solar which can possibly last for 2 -3 weeks at a time, frequently in winter when energy demand is highest. Remember the weather impact on Europe when “the Beast from the East” collided with storm Emma in 2018. This means that we cannot rely on electricity interconnectors as most/many European countries will be short at the same time, so everyone is in the same boat. This requires seasonal Hydrogen storage, using back-up Hydrogen-fueled generation.
New SOFC technology (solid oxide fuel cell) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Advantages of this class of fuel cells include high combined heat and power efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost; it is reversible, so that it acts as an electrolyser when electricity is plentiful and the same piece of equipment can act as a generator to convert Hydrogen to electricity when electricity is scarce, using the same grid connection, thus saving a lot of costs. The question of how to store the Hydrogen then arises, as Ireland has no salt deposits which can be converted to storage chambers (other than small deposits in Northern Ireland).
Green Hydrogen or Green Ammonia
The global knowledge of electrolysis and fuel cell technologies, and their widespread use for conversion of electricity to hydrogen and vice-versa, would point to green hydrogen as a logical contender for a preferred long-term and large-scale storage medium. Renewable electricity – preferably surplus – could be stored as green hydrogen and then this hydrogen distributed for short and medium term use in transport and heating/cooling, with the remainder stored for longer term use.
Some people regard Green Ammonia as a better option to Green Hydrogen. Although Ammonia is a toxic gas, liquid Ammonia storage is well developed and understood, particularly by the fertiliser industry which has been storing Ammonia liquid for decades. The most cost effective way to do it is chill the Ammonia so that it does not have to be pressurized. This reduces the steel in the tanks and saves capital costs. Another advantage of Ammonia is that it could be readily exported for the fertiliser industry or marine transport. Many of the European ports already handle Ammonia. Also, it would be possible to repurpose the fossil fuel storage facilities from the past like in coal yards, oil tanks, etc. to store the Ammonia. On the island of Ireland, most of our good generation sites are at ports for historical reason for importing fuels, both North and South, so could be used in the future for sea delivery of Ammonia (or LOHC - Liquid Organic Hydrogen Carriers).
Also, as Hydrogen has only approximately one third the energy density of natural gas by volume, Ireland’s best hope for Green Hydrogen longer-term storage may be either Green Ammonia or LOHC. This is another method to store hydrogen at ambient conditions namely through Liquid Organic Hydrogen Carriers (LOHC). LOHCs are potentially cheap, safe, and easily manageable. Moreover, they allow for long-term energy storage without boil-off or other hydrogen losses as well as an uncomplicated transportation.
Green-gas Storage Considerations
It is too early yet to come down solidly on the side of Green Hydrogen rather than Green Ammonia/LOHC. Ireland should engage in such discussions in Brussels and be central to the decisions made, so that we are part of a bigger ‘green’ energy picture in the future. Additionally, the global trend in whether hydrogen or synthetic liquid fuels derived from Green Hydrogen will be adopted for aviation and whether these and/or Ammonia/LOHC will be adopted for shipping will be crucial. Ireland must remain a player in large scale renewable energy (possibly large floating wind farms off the west and south coasts), large scale conversion to Green Hydrogen or Green Ammonia which can be transported by bulk tankers to help serve the global energy market.
Storage of Green Hydrogen for longer-term use remains a concern. It is generally regarded that Ireland is not blessed with good geology and other than the small salt deposits in Northern Ireland, we have little that is suitable for large-scale underground storage. This is a major concern if considered on a stand-alone basis. It would seem that a shared mega-storage capability across groups of countries is one approach to be considered but this carries inherent risks in time of scarcity.
The Need to Start Planning & Call for Development of Green Hydrogen Strategy
It is likely that Ireland’s Corrib and other natural gas will be exhausted in less than 15 years; imported natural gas may also be limited so we may have to look to our own resources, hence the need to start planning at this stage.
This is why the Irish Energy Storage Association (IESA) earlier this year called upon Minister Eamon Ryan to commence the development of a National Green Hydrogen Strategy; perhaps IESA should be calling for a green gas strategy (hydrogen & ammonia & other). The EU Commission and a number of Member States have already developed Hydrogen Strategies. The Minister’s office has indicated that he expects to kick-off this process in early 2021. The development of such a strategy – which should include hydrogen storage - is crucial in that it will have the effect of providing direction and coherence among the many groups active in this space.
An examination at how to decarbonize the Irish economy would point to renewables and Green Hydrogen as the only viable way for Ireland, particularly with the natural resources we have. A portfolio of storage technologies would be required from flywheels, batteries, pumped storage etc., to longer-term storage like Hydrogen (and maybe Ammonia) for seasonal storage. These technologies will operate over different time-frames. Also, looking at the security of supply and resilience in the total energy system it is clear, while it is a very positive move towards decarbonization, the loss of coal storage in Moneypoint, Peat on the bogs, HFO in Tarbert, Gas Oil for CCGTs, etc. as well as the loss of National Oil Reserves Agency’s (NORA) oil storage for transport as we electrify transport, all makes Ireland's energy system very brittle and at risk of serious disruption to energy security / supply.
Challenges for the gas networks
In some countries, gas network operators are looking at splitting their networks into 100% Hydrogen and gradually changing over the entire gas networks to 100% Hydrogen. Blending Hydrogen will only be an interim measure as an outlet for early-stage Green Hydrogen and then under controlled conditions so that downstream implications are understood and the combustion safety in all devices including domestic cookers and boilers or CNG for transport applications are within respective safety margins - blending is not a long-term solution.
GNI's (Gas Networks Ireland) network is probably too small to split into two, as it really is just one ring main. However, it is believed that GNI are acting in a very progressive and proactive manner by giving this matter huge consideration and examining different options including moving to a non-fossil gas grid in the longer term. It can be argued that the long term outlook for the natural gas industry in Ireland is bleak, particularly as we move beyond 2030 and fossil fuels are being phased out. It seems most likely that the national gas grid can only be used long term for only one gas, either for Methane (fossil, renewable or synthetic) or else Hydrogen.
Fig. 4: Current natural gas value-chain (Moreira da Silva, 2020)
Transport, Heating/Cooling and Shipping/Aviation
If one considers energy sustainability/reliance from a European and also global perspective that 100% renewable energy is the longer term objective with dispatchable plant to augment wind, solar and ocean energy, then finding a way to store large-scale renewable electricity by converting it to a usable form (batteries and Green Hydrogen) should be the way to go for electricity, transport and heating/cooling.
The Irish Government’s clear option for transport in a decarbonized economy is for EVs. However, many people interpret that to mean for Battery Electric Vehicle (BEV) cars and light-duty transport. However, for heavy-duty transport including trucks, buses, trains and agricultural tractors then green hydrogen Fuel Cell Electric Vehicles (FCEV) would seem the obvious solution for Ireland with our abundance of wind and also solar resources.
Regarding residential heating, it is also much better to use heat pumps if at all possible, as Green Hydrogen when used for heating, consumes approximately 4 times the electricity used by heat pumps because of the efficiency losses in converting from electricity to Hydrogen in the first place, as well as the coefficient of advantage in using heat pumps.
The vast energy requirements for shipping and the aviation industry should be considered also – where Green Hydrogen or maybe Green Ammonia/synthetic liquid fuels will become the global energy sources of choice. In the shipping sector, cargo vessels, cruise ships and ferries are all important parts of the global economy with most ships burning fossil fuels for power, emitting CO2 and other pollutants. A recent study by the ICCT (International Council on Clean Transportation) stated that liquid hydrogen could power nearly all container vessels crossing the Pacific Ocean – one of the busiest shipping lanes in the world.
Deploying Green Hydrogen to power the aviation industry is a long way down the road but much RD&D work is already under way in this area, where California-based ZeroAvia recently completed the first ever test-flight of a 6 passenger airplane powered solely by a hydrogen powered fuel cell. Synthetic liquid duels, derived from Green Hydrogen is another potential pathway. Furthermore, a recent independent study in Europe concluded that “hydrogen – as a primary energy source for propulsion, either for fuel cells, direct burn in thermal (gas turbine) engines or as a building block for synthetic liquid fuels – could feasibly power aircraft with entry into service by 2035 for short-range aircraft”.
Hydrogen Storage and System Frequency Regulation and System Recovery
In Ireland the renewable electricity target for 2030 is that 70% of all electricity consumed should come from renewable energy sources. While no decisions have been made beyond that, this target is likely to rise to 90% by 2040 and 100% by 2050. EirGrid (the TSO in Ireland) has demonstrated that when SNSP (System Non-Synchronous Penetration) is increased above 50% on windy/sunny days the System Operator requires additional support services to augment those coming from the remaining running synchronous power plant, to ensure a stable and secure system. Currently the trend is that Lithium Ion batteries will provide these services in response times of between 150 to 200 milliseconds, although ultra-capacitors and flywheels can also do the job. Such support may be needed for up to 20 minutes to enable system stability to be fully restored.
A significant advantage of Green Hydrogen is that fast-acting electrolysers can respond in real time (milliseconds) to fluctuations in renewable generation so actually enabling the TSO to accommodate more intermittent renewables on the grid, as well as solving curtailment issues. However, where they cannot respond in less than 200 milliseconds then they can be coupled with an appropriately-sized rapid-response battery, e.g. 2C or 3C Lithium Ion battery, to provide rapid high power input albeit for a shorter duration.
Fig. 5: Power system's frequency control (RWE, 2008)
Considerations for Investors in Wind farms and Solar-farms
It can be expected that ever-larger wind farms and solar-farms will be built in the future. The development of large off-shore floating wind farms will provide huge volumes of renewable energy and more importantly surplus renewable energy when the wind is blowing. Work on these is already underway with the Hywind Scotland 30 MW in commercial operation as the world’s first such wind farm using floating wind turbines, off the coast of Scotland. Floating wind farms have the potential to significantly increase the sea area available for offshore wind farms for western European countries and particularly those with limited shallow waters e.g. Japan.
Operating in harsh and aggressive environments will be a big challenge for floating wind farms and one that remains to be cracked. A €31 million floating wind project off the west coast of Ireland near Belmullet, which has some of the harshest conditions but also some of the strongest wind resources in the world, has been approved. The plan is that a full-scale floating wind turbine will be deployed for testing at a Sustainable Energy Authority of Ireland (SEAI) site. It is intended to demonstrate the survivability and cost-competitiveness of floating offshore wind technology. Such a break-through will be of huge benefit, not just to Ireland, but to the global off-shore wind generation industry.
Potential Glittering Future for the Shannon Estuary
The Shannon Estuary on the lower west coast of Ireland is naturally gifted with deep water, enabling large bulk tankers to sail upstream and load and unload cargo. Currently, this is confined largely to coal, oil and bauxite but the future will likely see coal and oil imports diminish significantly to be replaced by exports of bulk hydrogen and/or ammonia.
The proximity of Moneypoint and Tarbert with their large docking and unloading facilities (coal in the case of Moneypoint and oil in the case of Tarbert), coupled with their location on the electricity grid bestows an enormous advantage to this region. The two Moneypoint/Dublin 400 kV lines and the strong grid connection between Moneypoint and Tarbert and onto Knockraha, terminal of the planned Ireland-France Celtic Interconnector, enhances the infrastructural status of this region. Additionally, the proximity of Foynes, Aughinish and the proposed gas-storage terminal at nearby Ballylongford further enhances the riches of this region. In summary, the combination of deep water, superb docking facilities, excellent electricity grid connections and adjacent gas-storage capacity would point to an ideal region for development of a thriving Green Hydrogen economy over the coming decade for Ireland.
Assuming that current proposals for large off-shore wind generation is developed on the south and west coasts of Ireland are progressed over the coming decade then the deployment of large-scale electrolysers and Green hydrogen distribution and bulk storage facilities should be developed in parallel. This region has the potential to be one of the major hubs in the Green Hydrogen economy in Europe, in addition to being the construction/assembly/launching point for floating wind generators off Ireland’s west and south coasts. This article urges the Irish Government, together with all the relevant State Agencies including its inward investment arm IDA Ireland to embrace and develop this golden opportunity at an early date.
Note on the Author
Peter Duffy is President of the Irish Energy storage Association and has worked as an engineer in the energy industry for more than 50 years, including several years in power plants and in the training, commercial and regulatory functions. He has worked as an energy consultant and expert in several countries and in recent years worked on power plant and energy storage projects in Ireland. He is a member of Al Gore’s Climate Reality global team. He is a contributor to the Royal Chemistry Society’s 2018 publication “Energy Storage Options and their Environmental Impact”. While this article does not explicitly reflect the policies and views of the Irish Energy Storage Association (IESA), the author wishes to thank his IESA colleagues and former work colleagues for their comments and support in writing this article.