In September 2017, the supply of natural gas from the Corrib Gas terminal was interrupted due to a fault in odorising system. In order to maintain public safety all gas users in Galway and Mayo were asked to stop using natural gas and the flow of gas was reversed so that the unoderised gas could be flared at the Corrib terminal. This incident highlights an important question: How secure is Ireland’s gas supply?
Currently, the Corrib gas terminal is supplying more than 50 per cent of the country's gas demand (Figure 1), with the remainder coming mainly from the Moffat interconnectors with Great Britain (DCCAE, 2017). With the Corrib gas field due to run out over the coming 10 to 15 years, coupled with the potential of an increasing gas demand, especially if Ireland is to replace coal and peat with cleaner burning natural gas power plants, then the question arises: does Ireland need another source of gas, or are the current interconnectors more than capable of providing all of our natural gas needs for the foreseeable future?
Ireland’s first domestic gas field was discovered off the southern coast near Kinsale in 1971 (Energy Institute, 2017), this was followed by the creation of Bord Gáis Éireann in 1976 and the subsequent development of the natural gas network through the conversion of existing town gas systems. Natural gas has now become one of the main sources of energy in Ireland, contributing to 28 per cent of the primary energy. A total of 45 per cent of electrical power and 44 per cent of residential heating is being generated from natural gas (Howley, 2015). Demand for it in Ireland varies throughout the year, with the maximum occurring during the winter months; in 2016, this was approximately 544 million cubic meters, MCM (Figure 2).
Natural gas has the lowest CO2 footprint of fossil fuels and is an ideal fuel to provide back-up for intermittent renewable electricity, meaning that demand for gas is expected to grow by 28 per cent between 2016 and 2025 according to 'Ireland’s Network Development Plan, 2017' and 'Energy Security in Ireland: A Statistical Overview'(Dineen, 2016). In 2014, the island’s natural gas network contained approximately 2,200km and 11,200km of transmission and distribution pipelines respectively (GNI, 2015). The transmission network (high pressure pipelines) consists of an onshore gas supply in Moffat, Scotland; the interconnector pipelines (IC1 and IC2) with pipe diameters of 24” and 30” respectively; and the Scotland-Northern Ireland Pipeline (SNIP), which is 24” in diameter and has a 135km length along with the local transmission pipelines. Both interconnectors (IC1 and IC2) connect to the UK national transmission system: IC1 supplies the Republic of Ireland network and IC2 mainly provides natural gas to Northern Ireland and the Isle of Man (GNI, 2017) (Figure 3). The transmission network in the republic is relatively modern and because it is predominately a ring main with spurs, is capable of coping with outages. But as was observed in September 2017, customers along the transmission network spurs are at risk of potential supply issues.
A secure supply of natural gas is crucial for Ireland’s power generation system. Up to 85 per cent of electricity is obtained via gas during some peak winter days, when renewable electricity is not available. In the past decade,as has supplied generation plants with 2300 MW capacity (GNI, 2015). Despite natural gas being a fossil fuel, there remains the possibility to decrease Ireland’s overall CO2 footprint by the conversion of Ireland’s largest power plant, Moneypoint, from coal to natural gas. Moneypoint is a 915MW (ESB, n.d.) power plant which burns 7,000 tonnes of coal per day (two million tonnes per year); it is due to come to its end of life in 2025, and with no decision yet on its future, there are voices calling for its conversion to Combined Cycle Gas Turbine (CCGT), resulting in improved conversion efficiency and reduction of the CO2 emissions by up to 60 per cent (GNI, 2017). Therefore, along with an increasing investment in renewable energy sources, there is also a need to ensure that there is an uninterrupted supply of electricity and gas.
Of most importance to all gas and electricity users is that the utility is always available. This means that the gas network must be capable of transporting and delivering gas to all end users, all of the time. With production from the Corrib source already starting to decline, the question arises can Moffat supply all of Ireland’s future natural gas requirements and for how long? Gas velocity and pressure drop are the two most important operational parameters for gas networks,with recommended velocities of five to 10 m/sec and up to 15m/s in certain circumstances according to the pipeline standards such as API 14E. In 2017, at the peak gas demand for the island of Ireland, the interconnectors supplied 13.8 MSCMD (GNI, 2018), 57 per cent of Ireland’s total demand.
During the Corrib shutdown in September 2017, Moffat was capable of suppling all of Ireland’s gas requirements along with the gas required to flow back along the Mayo-Galway spur to flare all unoderised gas a total demand of 20.1 MSCMD, which is less than Ireland’s winter peak demand. Using the forecasted gas demand expected for 2025 (ERVIA, 2017), and if Corrib were again to be offline for a period of time, the Moffat interconnectors would have to supply up to 28.3 MSCMD. Distributing this flow among the three interconnectors, and modelling the flow through the pipeline using SAInt ® (an energy systems modelling software), results in an expected pressure drop of 19-27Bar with exit velocities of 6.8-6.9m/s from the pipelines when the inlet pressure is 70 barg (GNI, 2015) (Table 1)
However, if Moneypoint was also converted to natural gas, it would require an additional 2.2 kTonne per day of the natural gas for its 915 MW production (3.2MSCMD), resulting in increased flowrates and pressure drops through all pipelines. While the modelled scenarios suggest that the Moffat interconnectors are capable of supplying all the natural gas to the island of Ireland in 2025, even without the Corrib field, a loss of any of the interconnectors could result in the others exceeding their recommended operational specifications. Another potential source of natural gas in Ireland is from biogas and GNI is already planning for the installation of 12 biomethane injection facilities with a combined production of 11,500 GWh per year of methane, supplying approximately 15 per cent of projected natural gas in 2025 and 20 per cent by 2030 (Browne, 2017).
The inclusion of this gas would, of course, reduce demand on the interconnectors and would be available as a source of green gas. Despite the additional biomethane produced locally, with an increasing trend of gas consumption in Northern Ireland of 2.3 per cent annually and 3.5 per cent per annum in the republic, the maximum operational limit of the Moffat IC1 and IC2 interconnectors could potentially be reached by the late 2030s, when pipeline velocities exceed 15m/s and the exit pressure is approaching 20Barg. For Ireland’s requirements beyond 2025, reliance on a single source of gas is not ideal for energy security or gas market competition. The continuing Brexit negotiations and the uncertainty of what the future final outcome will look like (Deane, 2017), highlight the importance of diversified gas sources. The Shannon LNG terminal, which was granted planning permission in 2008, is still listed on the EU Projects of Common Interest 2017, but has stalled due to the energy regulator's decision on gas network access tariffs, and does not currently seem like a viable project.
The advent of Floating Storage Regasification Units (FSRU) and the recently signed memorandum of understanding between Cork Harbour and Next Decade looks increasingly like the most viable option for direct LNG importation into Ireland. The lower cost of FSRU and the quicker turnaround time of these projects makes it a more attractive proposition than a capital intensive on-shore LNG terminal. An example can be seen in Lithuania, where a FSRU was installed in December 2014 to ensure security of gas supply and this helped overcome the reliance on a single gas supply source. Worldwide, the LNG market is continuing to increase (IGU, 2017), with more export facilities coming online each year.
This opens up the possibilities for other sources of potentially cheaper gas for Ireland. The conversion of Moneypoint to a gas-fired power plant does raise questions about the over-reliance of the electricity system on natural gas, but there are other jurisdictions, for example, Singapore which produces more than 95 per cent of its electricity from natural gas. It has overcome the security of supply concerns by having multiple interconnector pipelines and an LNG terminal which, following recent upgrades, is capable of supplying all the state’s natural gas needs. Therefore, if Ireland is to ensure it maintains a secure supply of electricity, while at the same time keeping its CO2 emissions to a minimum, it may be time to consider a plan that will deliver security of gas supply through diversification. Authors: M Ali Ekhtiari, Eoin Syron, School of Chemical and Bioprocess Engineering, UCD Energy Institute, UCD O'Brien Centre for Science University College Dublin
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