Ireland has the potential to become a world leader in operating a renewables-based island electricity system, backed up by batteries to provide the essential system stability

Author: Nigel Reams, managing director, Lumcloon Energy Ltd

Battery Energy Storage Solutions (BESS) is a system that stores energy via the use of a battery technology for it to be used at a later time. Intended to assist the meeting of the EU’s 2020 renewable targets by enabling greater levels of wind and solar to be accommodated on the grid, the technology is in use across the UK, Europe, the United States and Australia. And the technology is poised to unlock the broad benefits of indigenous renewables for Irish electricity consumers. Internationally, BESS is quickly gaining traction due to vast improvements in battery capabilities and reduced production costs, mainly driven by the electric vehicle industry.

• In the UK, large-scale battery storage capacity exceeds 450MW, with 250MW completed in 2018 alone;
• In California, proposals were lodged in June for BESS projects totalling 2,270MW;
• In Queensland, Australia, up to 4,000MW of battery storage facilities have been proposed as part of a major new energy supply and security initiative.

It is an economic imperative that Ireland maximises the potential of its indigenous renewable resources. Ireland, Europe and the international community have set future targets to reduce greenhouse gas emissions to address the existential challenge that is climate change. ‘Meeting targets’ should be viewed as a unique opportunity and not as a burden.

Ambitious in transition to a low-carbon economy

Ireland needs to be ambitious in its transition to a low-carbon economy and realise this unique opportunity to increase the country’s energy independence. It has the potential to become a world leader in operating a renewables-based island electricity system, backed up by batteries to provide the essential system stability.

Figure 1: Profile of system frequency in Ireland for 2017, showing approximately twenty system frequency events. Image courtesy of Lumcloon Energy Ltd

The significant steps EirGrid has made towards achieving this are commendable – but we still have some distance to go. A stable, decarbonised electricity supply significantly improves the environmental benefits of electric mobility and electric heating/cooling. Sweden took a proactive approach towards wind deployment and is now set to meet its 2030 target this year [1]. More importantly, the Swedes are reaping the benefits of renewables.

Ireland’s great abundance of renewable energy sources

What about Ireland? We have a great abundance of renewable energy sources, including wind, solar, wave, tidal and biomass. The country is already successfully harnessing some of the available wind energy on the island; currently there is more than 4,500 MW of installed capacity (3,458 MW in the Republic of Ireland and 1,167 MW in Northern Ireland).

Wind energy accounted for more than 20 per cent of electricity generation in 2016 and is reaching an instantaneous penetration of 65 per cent in 2018. Last March, EirGrid announced ‘record levels’ of 65 per cent mainly wind-based renewable energy following a successful five-month trial and aims for 75 per cent levels in the near future.

The 75 per cent instantaneous penetration level of renewable energy was estimated as a requirement to reach an average level of 40 per cent that is the Ireland 2020 target of the annual renewable penetration [2]. It is expected that large-scale solar will soon contribute to the supply of renewable energy, complementing wind which had a low output during the recent spell of dry and sunny weather.

Operating the electricity system with a high penetration of variable non-synchronous renewables (wind and solar) comes with some challenges to maintain stability. In 2011, EirGrid and SONI, the Transmission System Operator (TSO), began the multi-year programme, ‘Delivering a Secure, Sustainable Electricity System’ (DS3). It aims to address the challenges of operating the electricity system securely.

Importance of continuity of supply

Continuity of supply is important for Ireland’s residents, and essential services such as hospitals, and is vital for our high-tech industries: pharmaceuticals, data centres, and advanced manufacturing, which are sensitive to fluctuations in system frequency. Stability and reliability to maintain the system frequency close to 50Hz is key for the electricity supply, which supports our society and economy. Figure 1 shows how the system frequency fluctuated in 2017 and several events of frequency shifting significantly from 50Hz.

Figure 2: Distribution of system frequency in Ireland for 2017. Image courtesy of Lumcloon Energy Ltd

While Figure 2 shows that most of the time the system frequency varies between 49.9 to 50.1Hz, on several occasions the frequency dropped below 49.5Hz as clearly visible in Figure 1.

These drops are considered ‘serious’ events and can cause large instabilities in the electric grid or even lead to blackouts if the frequency drop is not arrested quickly and then reversed so that the frequency recovers. To avoid disastrous scenarios, BESS or similar technologies are used to react by injecting/absorbing power in a fraction of a second and restore the frequency in the safe range.

Less and less space on system for heavy conventional generators to provide grid stability

Historically, heavy steam turbines and generators which were synchronised to the grid reacted automatically to inject power and stabilise the frequency. However, as the percentage of non-synchronous renewable generation increases, there is less and less space on the system for these heavy conventional generators to provide grid stability. The issue of frequency instability and the further challenge of operating an electricity system with renewable sources led to the development of an enhanced system services market.

Recently, this market transitioned from the old market (named Harmonised Ancillary Services) to the new DS3 market in 2016. It started with an interim arrangement with contracts being awarded to 25 existing providers shown in Figure 3.

The interim arrangement is being replaced by the enduring arrangement in two phases. Phase 1 started in mid-2018 with the Volume UnCapped contracts (results yet to be published).

Phase 2, the Volume Capped process, was due to open in March 2018 but has been beset by a series of delays – the most recent of which was announced by EirGrid on July 28, 2018. It provided limited explanation for the delay and lacked any firm timeline for implementation, which is disappointing. Volume UnCapped contracts are offered for five years and can be terminated with one-year notice from the TSO, presenting a high risk for new investments.

BESS projects to target contracts in Volume Capped process

BESS projects are expected to target contracts in the Volume Capped process, which offers a six-year contract, providing the minimum required certainty to underpin the significant new investment and subsequently new technologies.

EirGrid has signalled an initial demand up to 300MW of system services in the Volume Capped process, but this can be expected to grow in the coming years as much more ambitious 2030 and 2050 emission reduction targets become a reality.

Figure 3: DS3 System Services Interim Arrangements successful tenderers for Ireland and the services for which they have been contracted. [3] Image courtesy of Lumcloon Energy Ltd

Lumcloon Energy Limited, backed by South Korean BESS experts Hanwha Energy Corporation and LSIS, is one developer which has been closely following the regulatory signals over the past several years and has developed two shovel-ready BESS projects in the midlands.

BESS is a highly efficient and effective source of system services, as it is not a generator, meaning BESS can provide stability to the electricity system without displacing renewable resources.

Conventional generators, on the other hand, must be generating, which reduces the amount of renewable electricity that can be accepted on the electricity grid. Curtailing (and substituting) renewables with high emissions intensity conventional generators for reasons of electricity system stability, defeats the objective of greenhouse gas reductions.

The DS3 requirements for BESS are not fully defined yet. The BESS industry in Ireland is eagerly awaiting the forthcoming decision from the regulatory authorities and is expected imminently to clarify important technical and contractual conditions.

Capability to perform when the wind is blowing

However, one can clearly conclude now that the electricity system will benefit from proven BESS capabilities, rapid response of BESS, high availability, and the capability to perform when the wind is blowing, and renewable penetration is at its highest.

A BESS plant will operate as a ‘stand-by’ system, continuously monitoring the electricity system frequency, poised to respond rapidly to system frequency events (when, for example, a conventional generator trips off line).

A BESS plant’s power output will follow the Frequency Response Curve, shown in Figure 4, adjusting its power output as the system frequency fluctuates. BESS for DS3 are expected to be focused on achieving high power output rapidly and sustaining it for a reasonably short duration, up to 20 minutes.

Figure 4: Frequency Response Curve for DS3 Volume Capped. [4] Image courtesy of Lumcloon Energy Ltd

BESS can provide a rapid and accurate response, injecting power within 150 milliseconds, to recover the imbalance between electricity supply and demand caused by the loss (trip) of a generator or transmission line.

A simulated response to a real event in 2017 is shown in Figure 5, where the frequency falls rapidly, triggering the automatic output from a BESS plant, which reacts as per the Frequency Response Curve.

Reducing risk of brown-out or blackout

The faster an imbalance can be recovered, the less impact an event will have on the electricity system, reducing the risk of brown-out or blackout and damage to electrical machines.

One example of a 100MW BESS on a similar size grid to Ireland is the Hornsdale Power Reserve, in South Australia, which has demonstrated its performance capability [5].

BESS has high availability, making it a very effective source of system services due to the minimal requirement for maintenance. Operational BESS plants have demonstrated availability of 98 per cent, meaning that a plant can operate for more than 8,500 hours per year. This should provide assurance to the system operator that the system services will be available when needed.

The modular nature of BESS means it has an inherently high redundancy as components are arranged in parallel. This reduces the risk of a single point failure impacting the overall performance of the BESS plant.

Figure 5: Expected BESS power output determined by the Frequency Response Curve based on real system frequency event (05/10/2017 05:28:42) Image courtesy of Lumcloon Energy Ltd

Unlike conventional generators, BESS can provide system services at high system non-synchronous penetration (SNSP) as the capability is not dependent on being dispatched and synchronised to the electricity system. At times when renewables are generating 75 per cent of the electricity, BESS is capable of supporting the electricity system.

BESS development in Ireland has seen huge growth in recent months with incumbents (including ESB, Bord Gáis Energy and AES) and new entrants (including RES, Engie, Low Carbon, Grid System Services, Highfield Energy, and ABO Wind) developing projects across the country, with more than 10 100MW projects in the pipeline.

Developers are eagerly awaiting decisions from the regulatory authorities, in order to finalise plant designs, before the procurement process opens in September this year.

Author: Nigel Reams, managing director, Lumcloon Energy Ltd

[1] Svensk Vindenergi, (Swedish Energy Association), “Statistics and forecast for the Wind Power Market (Q2,
2018),” 2018.
[2] EirGrid, “DS3 Programme,” August 2011. [Online]. Available: works/ds3-programme/.
[3] EirGrid, “DS3 System Services Interim Arrangments Procurement Outcome,” 27 February 2017. [Online]. Available: EirGrid_Final.pdf.
[4] EirGrid, “EirGrid Group,” 29 March 2018. [Online]. Available: files/library/EirGrid/Consultation-on-DS3-System-Services-Volume-Capped-Competitive- Procurement.pdf.
[5] Australian Energy Market Operator, “Initial Operation of the Hornsdale Power Reserve Battery Energy Storage System,” 5 April 2018. [Online]. Available: Hornsdale-report. O'RiordanElecEirGrid,energy,renewables
Author: Nigel Reams, managing director, Lumcloon Energy Ltd Battery Energy Storage Solutions (BESS) is a system that stores energy via the use of a battery technology for it to be used at a later time. Intended to assist the meeting of the EU's 2020 renewable targets by enabling greater levels of...