MSc Energy Engineering with Environmental Management ENG-7003B – Wind Energy Engineering Ex1 Team-based Coursework Supporting Summary: “Examine the role that pumped storage power stations play in supporting the UK grid. If a catastrophic failure occurred that put Dinorwig power station out of action for 3 years from December 2017, what impact is that likely to have on the way the grid could supply UK peaks in demand?” by Project Team B (Catalina Igoa, Andy Cossey, James Eastman, Manuel Manrique Castañeda) University of East Anglia Faculty of Science School of Mathematics Norwich Research Park Norwich NR4 7TJ United Kingdom 20/02/2017 1. Introduction 1.1 Brief The aim of the presentation and this report is to analyse the role pumped storage stations play in supporting the United Kingdom’s (UK) National Grid, particularly the main pumped storage station: Dinorwig Power Station. To help determine Dinorwigs’ importance, and what may happen if it were out of action until 2020, current and future electricity generation was examined. 1.2 Current electricity generation Figure 1. Shares of Electricity Generation (BEIS,2016a) 1.3 Future Targets The UK has compromised itself by the Renewable Energy Directive 2009/28/EC on Promotion of the use of energy from renewable sources (2009) to achieve 15% of energy production from renewable resources by 2020. One of three targets set to help achieve this objective is the aim to produce 30% of electricity from renewables by 2020 (DECC,2010). Most of this supply will come from wind farms. Another objective of the Directive is to reduce carbon dioxide emissions. The UK's objective is to reduce approximately 75% of the emissions from electricity generation by 2030 (DECC,2015). To achieve this reduction cost-effectively, whilst ensuring the stability of electricity supply, the UK’s strategy is based upon an increase of gas, nuclear and offshore wind power generation (House of Common, 2016). Figure 2. Change in the percentage of electricity generation (Vaughan, 2017) 2. Consequences from the use of Gas, Nuclear and Offshore Wind Energy Supplies As shown (Figure 2), the decrease in the use of coal from 2009 is somewhat compensated by increased use of gas and wind energy sources, which is aligned with the strategy to reduce CO2 emissions. The use of gas, nuclear and offshore wind as sources of energy each have their advantages and disadvantages, but it can be concluded that extra storage capacity is needed to support this change; the reasons for this will be explained throughout the document. 2.1 Gas On average, each gigawatt-year of electricity generation switched from coal to natural gas reduces CO2 emissions by 59 percent (Lafrancois, B., 2012). However, burning gas is still not a renewable source of energy and it is not as clean as renewable energy; although it has the advantage of being a relatively flexible source of energy. Gas Turbines can be powered during peak hours, although they cannot respond quickly to sudden demand spikes (for example, over a thirty-minute period). The total UK electricity demand in 2016 was approximately 330 TWh (GridWatch,2017). Per Figure 2, 40% (132 TWh) of production in this period came from gas. This output is close to the maximum generation that the UK’s Combined Cycle Gas Turbines (CCGT) can currently deliver. Calculations supporting this statement can be found in Annexe 1. Furthermore, as shown in Figure 3, the UK relies upon imports for more than 50% of its total gas consumption. Figure 3. UK gas (The Source, 2016) Upon consideration, gas is certainly a cleaner energy source than coal and helps towards providing a stable baseload of supply to meet with the constant electricity demand; however, it is unable to react quickly to sudden demand spikes, indeed, current gas-powered stations are already working close to capacity. Furthermore, the requirement for gas imports reduces energy self-reliability in the UK. 2.2 Nuclear As seen (Figure 2), electricity generation from nuclear energy has been very consistent throughout the eight-year period; 2009-2016. Similarly, as with gas-powered stations, nuclear power plants are operated continuously at full load and therefore are unable to provide additional power during demand spikes. Although additional capacity is planned, this will not be operational in the relevant period and there is significant worldwide political pressure against the building of nuclear fission power stations, primarily due to security concerns following the Fukushima accident along with potential terrorist activity. 2.3 Wind power Wind power has seen an exponential increase since 2009, as wind energy has been seen as the key factor to achieving the 30% target of electricity from renewables by 2020. Installed wind power capacity in January 2017 was 14.5 GW; 9.395 GW from onshore capacity and 5.098 GW from offshore capacity (RenewableUK, 2017). However, wind power is an inconsistent and somewhat unpredictable source of power, its efficiency depends upon the hour, day, and season of the year along with daily weather patterns. Figure 4 shows the average wind power capacity factor by season in the UK: Figure 4. Average Daily Variability in UK Wind Power Capacity Factor (Sinden, 2007) However, the data in Figure 4. is averaged, and there is no security than in any certain day these values will be achieved. Figures 5 & 6 aim to show the intermittency of wind by comparing the contribution of wind energy recorded over two days, with a two-week interval between each day. Additionally, the data in Figure 5 was recorded upon the day with the greatest demand during the 2015/2016 period; it is apparent that the contribution from wind energy this day was very low (relatively), measured in megawatts. 300 Wind (MW) 250 200 150 100 50 0 0:00:00 4:48:00 9:36:00 14:24:00 19:12:00 0:00:00 Time Figure 5. Wind Contribution for triad day 19.01.2016 (GridWatch,2017) 7000 Wind (MW) 6000 5000 4000 3000 2000 1000 0 0:00:00 4:48:00 9:36:00 14:24:00 19:12:00 0:00:00 Time Figure 6. Wind Contribution for 01.02.2016 (GridWatch,2017) Research estimates that, as wind power capacity increases, by 2020, 27% of our wind electricity will be wasted unless it can be stored and released when needed to help balance peak supply and peak demand. Additional storage capacity is therefore the key factor for ensuring that increased power generation is not wasted. 3. Pumped Storage Power Stations Pumped storage stations operate using two water reservoirs, one lower than the other, to create an energy potential. During periods of low demand and cheaper energy, water is pumped to the upper reservoir; this water then is released through a turbine to generate electricity during times of peak demand. Pumped storage is a net user of power, but, when used in conjunction with other renewable energy methods to pump water back to the upper reservoir, it can help to resolve problems with intermittency issues associated with renewable technologies (BHA,2017). 3.1 Pumped Storage Stations in the UK The UK has four pumped storage facilities: Festiniog, Cruachan, Foyers and Dinorwig. The maximum amount of energy stored by the four facilities is 30GWh. Dinorwig is the main supplier to the National Grid, with a capacity of 1.8 GW. It can be switched on and providing 1.3 GW of power within 12 seconds (MacKay,2009). With all four facilities operating simultaneously, they can produce 2.8 GW of power. Compared with other sources of electricity, this amount may not seem particularly significant, however the main advantage is it can be switched on and providing very quickly, helping the Grid to cope with sudden demand or lulls in wind activity. 4. Triad Days 4.1 Definition The Triad Days are three half hour periods of peak power demand across the National Grid in the period from November to February, when energy demand is at its most intensive. They need to be 10 days apart to avoid adversely affecting industry and business within consecutive half-hours. Triads are used to calibrate the transmission costs, which are then passed to heavy consumers of energy. Although there is no way of knowing in advance when a Triad may occur, companies can sign for a Triad warning service, and if they have an efficient energy strategy, they may escape from Triad payments (SSE Business Energy, 2016). Table 1 shows the Triad days of the last three years. It can be seen how the maximum demand is always around 17:30 and between Monday to Friday. This is due to high domestic demand coinciding with industry/business demand. Table 1 Triad days from 2013 to 2016 (National Grid, 2017a) DATE 2015 - 2016 Wednesday 25 - 12 - 2015 Tuesday 19 - 01 - 2016 Monday 15 - 03 - 2016 HALF HOUR ENDING DEMAND (MW) 17:30 17:30 18:30 47,601 50,596 47,982 2014 - 2015 Thursday 04 - 12 - 2014 Monday 19 - 01 - 2015 Monday 02 - 02 - 2015 17:30 17:30 18:00 49,655 51,276 50,859 2013-2014 Monday 25 - 11 - 2013 Friday 06 - 12 - 2013 Thursday 30 - 01 - 2014 17:30 17:30 17:30 50,694 49,927 49,947 4.2 Triad day: 19.01.2016, maximum demand for the 2015/2016 Period The importance of pumped storage on the 19th January 2016 triad can be seen in Figure 7 below. In the hour where demand peaked, the pumped storage contribution reached its maximum, because of its ability to reach full capacity within seconds. As previously stated, the total capacity of pumped storage is 2800 MW, while average efficiency is 0.75 (MacKay,2009). Therefore, with all of them operating together, output would be 2100 MW. At 17:30, the contribution was 1815 MW, close to the total maximum output. 2000 Pumped (MW) 1816 1500 1000 500 0 0:00:00 4:48:00 9:36:00 14:24:00 19:12:00 0:00:00 Time Figure 7. Pumped Storage output 19th January, 2017 (GridWatch, 2017) Another important contribution towards satisfying peak demand is the imported electricity from the UK's interconnections with France, Northern Ireland, Netherlands and with the East-West (South Ireland). Table 2. Interconnectors in the GB electricity system (Moore, 2010) Project Name Company Location Capacity (GW) Start year Interconnexion France Angleterre (IFA) Moyle National Grid and RTE (French transmission system operator) Mutual Energy Between Folkestone, Kent and Calais, France 2 1986 Between Auchencrosh, Ayrshire, Scotland and Ballycronan More, Co. Antrim, Northern Ireland Between Isle of Grain, Kent and Rotterdam, Netherlands 0.5 2001 BritNed National Grid and TenneT (Dutch TSO) 1 Between Shotton, Wales and Rush North, Co. Dublin 0.5 Operational since 2009, at full capacity since 2010 2012 East-West EirGrid However, as can be seen in Figure 8, during peak demand they are already working almost to their full capacity. There could still be 500 MW left from the Dutch interconnector, but this would not be enough to replace the contribution of Dinorwig (1800 MW) if it were non-operational. 4000 2000 ew_ict irish_ict 1000 dutch_ict french_ict 0 -1000 0:00:00 1:10:00 2:20:00 3:30:00 4:40:00 5:50:00 7:00:00 8:10:00 9:20:00 10:30:00 11:40:00 12:50:00 14:00:00 15:10:00 16:20:00 17:30:00 18:40:00 19:50:00 21:00:00 22:10:00 23:20:00 Imported (MW) 3000 -2000 Figure 8. Imported electricity 19.01.2016 (GridWatch, 2017) Furthermore, analysis (Ofgem, 2014) shows that the risk of supply to each of the countries interconnected with the UK is expected to increase in future. Therefore, unless we become more selfreliant, there is a potential to lose import availability. 5. Mitigating Actions to Manage Supply Shortfalls If electricity demand exceeds market supply the first mitigating action to be used by the National Grid would be the SBR and DSBR services (Ofgem, 2015): Supplemental Balancing Reserve (SBR): the service is aimed at generators who are either closed, mothballed or generally unavailable to the market. They would only be required after all actions within the normal operations have been taken (National Grid, 2017b). Through SBR, coal power stations are paid to be available if needed. Demand Side Balancing Reserve (DSBR): the service is targeted at commercial and industrial consumers who volunteer to decrease their demand of energy between 4 and 8 pm on winter weekday evening in return for a payment (National Grid, 2017c). For example: a fridge-freezer draws around 18 W power; the estimated number of refrigerators is approximately 30 million. The ability to switch off all the nation’s fridges for a few minutes would be equivalent to 0.54 GW of automatic adjustable power (MacKay, 2009). If these measures are not enough, other actions that can be implemented prior to a controlled disconnection are: voltage reduction; maximum generation; and emergency services from interconnectors. Furthermore, National Grid concluded the T-4 Capacity Auction for 2020/21 delivery on December 2016, to secure electricity supplies for the 2020/2021 winter period (National Grid, 2017d). The auction secured over 52GW capacity; remarkable excerpts: ● New gas generation, including two new power stations, will be built ● 500 MW of new battery storage – agreements won for the first time in market auctions. 6. Storage Technologies Dinorwig installed capacity is 1800 MW and works at an average efficiency of 75%. Therefore, the output is approximately 1350 MW. Annexe 2 shows an estimated cost of replacing Dinorwig’s 1350 MW output with different storage technologies. Other factors that should be considered when choosing an alternative, for instance, the technological maturity and economy of the solution. As previously stated, in the National Grid 2016 auction, low-carbon battery storage has been agreed upon. 7. Conclusions Pumped storage generation, particularly at Dinorwig, is already key to satisfy peak demand and is working close to maximum operating output. If Dinorwig power station was inoperative for three years from 2017, although the National Grid would have several courses of mitigating action before any disconnection is suffered by the customers, the loss would have a large impact, more so in triad days. As Dinorwig contribution is 1800 MW at 75% efficiency, reachable within 12 seconds. Given that the UK electricity generation strategy to reduce CO2 emissions and to achieve the target of 30% of electricity from renewables is based upon the increase of gas, nuclear and wind energy, pumped storage becomes even more important. A problem in Dinorwig in 2020 would be even worse that if it happened today. 8. Recommendation Increasing energy storage would be an answer to: intermittency issues associated with renewable technologies fixed output of nuclear plants making the UK more energy self-reliant by not depending so heavily on imported electricity and gas reducing CO2 emissions by further reducing use of gas, or coal, powered stations any problem that may potentially put Dinorwig power station out of action. The most mature storage technology is pumped storage, but other technologies will become more important in future as technology matures and associated costs reduce. Annexes Annexe 1 Electricity from gas is primarily delivered from CCGT power plants as shown in Table 3. The total capacity of CCGT at the end of 2015 was 31,741 MW, compared with 1,333 MW for the sum of gas turbines and oil engine power plants. For the following calculation, the total capacity of 2016 for CCGT will be considered using 2015 data, as 2016 data is currently unavailable. The values used can be found in Table 3 and Table 4. CCGT Output = 330×40% (24×365)×106 =15,069 MW CCGT Capacity (2016): 31,741 MW CCGT Thermal Efficiency: 48% Maximum Output 2016: 31,741 * 48% = 15,236MW CCGT in 2016 worked almost to its full capacity. On average, there was 168 MW capacity remaining. Table 1 Plant Capacity United Kingdom (BEIS,2016b) MW 2011 2012 2013 2014 end December 2015 89,031 89,299 84,598r 83,543r 80,820 Conventional steam stations (8) 34,164 30,988 25,230r 23,392r 20,794 Combined cycle gas turbine stations 32,395 35,357 34,872r 33,807r 31,741 Nuclear stations 10,663 9,946 9,906 9,937 9,487 1,706 1,651 1,639r 1,643r 1,333 Natural flow (4) 1,550 1,556 1,561 1,569r 1,580 Pumped storage 2,744 2,744 2,744 2,744 2,744 Wind (4) 2,781 3,827 4,821r 5,606r 6,145 Solar (4) - - 488 922 1,561 3,027 3,231 3,337r 3,923r 5,435 Major power producers (1) Total capacity Of which: Gas turbines and oil engines Hydro-electric stations: Renewables other than hydro and wind (4) Table 4 Thermal Efficiency (BEIS,2016b) 2011 2012 2013 2014 end December 2015 Combined cycle gas turbine station: Per cent 48.1 47.2 47.7 48.0 Coal fired stations Per cent 35.7 35.8 35.9 35.6 Nuclear stations Per cent 38.0 39.8 39.6 39.1 Thermal efficiency (gross valorific value basis) Annexe 2 Table 5. Storage technologies (REA, 2016) Technology Maturity Cost (2010 US dollars/kW) Efficiency Response Time Average cost Average efficiency Necessary installed capacity (MW) Total Cost (2010 US dollars) Pumped Hydro Mature 1,5002,700 80–82% Seconds to Minutes 2100 81% 1666.7 3,500,000,000 Compressed Air (Underground) Demo to Mature 960-1,250 60-70% Seconds to Minutes 1105 65% 2076.9 2,295,000,000 Compressed Air (Above-ground) Demo to Deploy 1,9502,150 60-70% Seconds to Minutes 2050 65% 2076.9 4,257,692,308 Flywheels Deployed to Mature 1,9502,200 85-87% Instantaneous 2075 86% 1569.8 3,257,267,442 Lead Acid Batteries Demo to Mature 950-5,800 75-90% Milliseconds 3375 83% 1636.4 5,522,727,273 Lithium-ion Batteries Demo to Mature 1,0854,100 87-94% Milliseconds 2592.5 91% 1491.7 3,867,265,193 Flow Batteries (Vanadium Redox) Develop to Demo 3,0003,700 65-75% Milliseconds 3350 70% 1928.6 6,460,714,286 Flow Batteries (Zinc Bromide) Demo to Deploy 1,4502,420 60-65% Milliseconds 1935 63% 2160.0 4,179,600,000 Sodium Sulphur (NAS) Demo to Deploy 3,1004,000 75% Milliseconds 3550 75% 1800.0 6,390,000,000 Power to Gas Demo 1,3702,740 30-45% 10 Minutes 2055 38% 3600.0 7,398,000,000 References BHA, 2017. Pumped storage: British Hydropower association. [online] Available at: < http://energystorage.org/energy-storage/technologies/vanadium-redox-vrb-flow-batteries >[ Accessed 11 February 2017]. Department for Business, Energy & Industrial Strategy (BEIS), 2016a. Energy Trends December 2016. [pdf] London: Department for Business, Energy & Industrial Strategy. Available at: <https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/579542/ET_Dec_16.p df > [Accessed 9 February 2017]. Department for Business, Energy & Industrial Strategy (BEIS), 2016b. Digest of United Kingdom Energy Statistics 2016. [pdf] London: Department for Business, Energy & Industrial Strategy. Available at: <https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/577712/DUKES_2016 _FINAL.pdf > [Accessed 9 February 2017]. Department of Energy & Climate Change (DECC), 2010. National Renewable Energy Action Plan for the United Kingdom,2010. [pdf] London: Department of Energy & Climate Change. Available at: <https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/47871/25-nat-renenergy-action-plan.pdf> [Accessed 7 February 2017]. Department of Energy & Climate Change (DECC), 2015. Updated energy and emissions projections 2015. [pdf] London: Department of Energy & Climate Change. Available at: <https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/501292/eepReport201 5_160205.pdf> [Accessed 9 February 2017]. GridWatch,2017. G.B. National Grid Status. [online] Available at: <http://www.gridwatch.templar.co.uk/index.php> [Accessed 31 January 2017]. House of Commons Energy and Climate Change Commitee, 2016. The energy revolution and future challenges for UK energy and climate change policy. [pdf] London: House of Commons. Available at: < https://www.publications.parliament.uk/pa/cm201617/cmselect/cmenergy/705/705.pdf > [Accessed 9 February 2017]. Lafrancois, B., 2012. A lot left over: Reducing CO2 emissions in the United States’ electric power sector through the use of natural gas. Energy Policy, [e-journal] 50(428). Available through: University of East Anglia Library website <https://portal.uea.ac.uk/library > [Accessed 9 February 2017]. Macalister T., 2016. Longannet power station closes ending coal power use in Scotland. The Guardian, [online] Available at: <https://www.theguardian.com/environment/2016/mar/24/longannetpower-station-closes-coal-power-scotland> [Accessed 9 February, 2017]. MacKay D., 2009. Sustainable Enegy - without the hot air. [pdf] Cambridge: UIT Cambridge Ltd. Available at: < http://www.withouthotair.com/cft.pdf> [Accessed 11 February, 2017]. Moore S., 2014. Getting Interconnected. [pdf] London: Policy Exchange. Available at: <https://policyexchange.org.uk/wp-content/uploads/2016/09/getting-interconnected.pdf> [Accessed 16 February, 2017]. National Grid, 2017a. Triad Data. [online] Available at:< http://www2.nationalgrid.com/UK/Industryinformation/System-charges/Electricity-transmission/Transmission-Network-Use-of-SystemCharges/Transmission-Charges-Triad-Data/> [Accessed 30 January, 2017]. National Grid, 2017b. Supplemental Balancing Reserve (SBR) Tender Documentation. [online] Available at:<http://www2.nationalgrid.com/UK/Services/Balancing-services/Systemsecurity/Contingency-balancing-reserve/SBR-Tender-Documentation/>[Accessed 14 February, 2017]. National Grid, 2017c. Demand Side Balancing Reserve (SBR) Tender Documentation. [online] Available at:< http://www2.nationalgrid.com/UK/Services/Balancing-services/Systemsecurity/Contingency-balancing-reserve/DSBR-Tender-Documentation/> [Accessed 14 February, 2017]. National Grid, 2017d. Provisional Auction Results, T-4 Capacity Market Auction 2020/21. [pdf] Available at: <https://www.emrdeliverybody.com/capacity%20markets%20document%20library/provisional%20res ults%20report%20-%20t-4%202016.pdf> [Accessed 11 February, 2017]. Ofgem, 2014. Electricity Capacity Assessment 2014: Consultation on methodology. [pdf] London: Ofgem. Available at: <https://www.ofgem.gov.uk/sites/default/files/docs/2013/11/electricity_capacity_assessment_2014__consultation__1.pdf> [ Accessed 16 February, 2017]. Ofgem, 2015. Electricity security of supply. [pdf] London: Ofgem. Available at: < https://www.ofgem.gov.uk/sites/default/files/docs/2015/07/electricitysecurityofsupplyreport_final_0.pdf >[ Accessed 15 February, 2017]. Renewable Energy Association(REA), 2016. Energy Storage in the UK An Overview. [pdf] London: REA Publication. Available at: <http://www.r-ea.net/upload/rea_uk_energy_storage_report_november_2015_-_final.pdf> [Accessed 13 February, 2017]. Renewable Energy Directive 2009/28/EC of 23 April 2009 on Promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC. RenewableUK, 2017. Wind Energy Statistics. [online] Available at: <http://www.renewableuk.com/page/UKWEDhome> [Accessed 11 February, 2017]. Sinden, G., 2007. Characteristics of the UK wind resource: Long-term patterns and relationship to electricity demand. Energy Policy, [e-journal] 35(112). Available through: University of East Anglia Library website: <https://portal.uea.ac.uk/library> [Accessed 11 February, 2017]. SSE Business Energy, 2016. How peak power warnings can save you money. [online] Available at: <https://www.ssebusinessenergy.co.uk/business-energy-electricity-and-gas/largeorganisations/triads/> [Accessed 1 February, 2017]. The Source, 2016. Where does UK gas come from?. [online] Available at: <https://www.britishgas.co.uk/the-source/our-world-of-energy/energys-grand-journey/where-does-ukgas-come-from> [Accessed 8 February, 2017]. Vaughan A., 2017. UK wind power overtakes coal for first time. The Guardian, [online]. Available at:< https://www.theguardian.com/business/2017/jan/06/uk-wind-power-coal-green-groups-carbon-taxes> [Accessed 9 February, 2017]. Wind Energy Update, 2015. Pumped hydro storage softens blow of wind imbalance penalties. [online] Available at:< http://analysis.windenergyupdate.com/construction/pumped-hydro-storage-softensblow-wind-imbalance-penalties> [Accessed 7 February, 2017].