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December 2020 – open access articles The following articles are taken from Energy World magazine’s December 2020 edition for promotional purposes. For full access to the magazine, become a member of the Energy Institute by visiting www.energyinst.org/join
Your EI magazines Dear member, The feedback from members now reading their usual EI magazine in our new digital flipbook format has been tremendous, as the comments on this page demonstrate. I have been particularly pleased at the number of members who, as a result, have started reading both our magazines – Energy World and Petroleum Review. Together they provide an unrivalled window onto the complete energy landscape. As I wrote in last month’s issue, digital is fast becoming our default for delivering and improving our member benefits, and it is also part of our determination to reduce our impact on the environment. From the start of 2021, in place of hard copies being the norm, we will instead be inviting you each month in our Energy Network e-newsletter to access the latest digital flipbook magazines online. So please do ensure your email address on our system is up to date at myprofile.energyinst.org/Home/Login There is still time for anyone genuinely without ready access to the internet to opt in to a hard copy. We can make sure you continue to receive your magazine without interruption if you email magsinprint@energyinst.org or write to Mags in print, 61 New Cavendish Street, London W1G 7AR by 7 December, stating your name, membership number and preferred magazine. But I should stress this is the exception. My strong encouragement is to make the most of your membership online – by logging in at knowledge.energyinst.org/magazines, where you will find not one, but both, of those exclusive member magazines. My best wishes,
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Renewables
OCEAN ENERGY
Waiting in the waves
The urgency of the climate crisis means it’s high time to get serious about harnessing the power of the oceans. Andrew Mourant looks at how the wave and tidal sector is finally beginning to be established at several sites around the world.
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Simec Atlantis, one of the world’s most active tidal energy companies, prepares a turbine for installation. Photo: Simec Atlantis
nvestment in wave and tidal energy has long been inhibited by the sheer cost of building in the ocean. What’s more, there’s the risk of storm damage to consider, as well as maintenance costs and the sensitivity of marine environments. More money and research are needed if ocean energy is to catch up with other renewables. This means cooperation on a big scale: research institutes, funding bodies, public authorities, utilities and the supply industry all need to get on board. Industry optimists claim the potential of the sea is enormous. In October, network body Ocean Energy Europe (OEE) predicted that 2.9 GW could be deployed annually by 2030 around the continent, accounting for 92% of global output. Costs could be reduced so that price of tidal energy would be €90 per MW, while wave power would cost €110 per MW. By 2050, OEE predicts wave and tidal sources could deliver 100 GW of capacity – equivalent to 10% of Europe’s electricity consumption. Crystal ball-gazing from those with a vested interest should be treated cautiously, but as collaborations mature, there may be grounds for optimism. In February 2020, the European
12 Energy World | December 2020
Marine Energy Centre (EMEC), which provides sea testing facilities, listed 97 wave and tidal projects globally. Tidal is farther ahead in contributing to the worldwide grid than wave, which has had a chequered history, and for which technologies are still evolving. Waking up to wave power The world’s first commercial operation, Pelamis Wave Power’s Agucadoura farm off Portugal’s north-west coast, was shortlived. Its three generators began producing 2.25 MW in September 2008. The long-term aim was to generate 22.5 MW for staterun power company Energias de Portugal. But the project was plagued with technical and financial problems. The global credit crunch put a stop to the reinstallation of faulty generators and the farm shut down. The Sotenäs wave energy project, off Sweden’s west coast, was also ill-fated. Construction began in 2010 and it was commissioned in 2016. Using energy-capturing buoys, it was intended to provide an output of about 10 MW, making it the world’s largest demonstration project of its kind. Its design
comprised a coupled linear wave energy generator attached to the seabed, connected via a line to a buoy on the sea’s surface. Sotenäs was jointly financed by power generator and retailer Fortum, wave technology company Seabased, and the Swedish energy authority. Research and development involved specialist academics at Uppsala University. However, by January 2019, the project ground to a halt after Seabased, citing ‘multiple factors’, liquidated the subsidiary company that made its generators and buoys. The difficulty with wave energy technology lies in the complexity of harnessing its power. Attempts to do so lead to many and varied designs – there’s no shortage of trial projects. Swedish firm Eco Wave Power (EWP) is among the pioneers. Since 2014, it has operated an off-grid pilot power station in Jaffa Port, Israel. The station allows for the testing of new components along with floater designs and materials. In October 2018, EWP was awarded an Israeli government grant to expand the station to 100 kW and connect to the Israeli national grid. EWP is also active in Gibraltar, where, in 2014, it signed a 5 MW power purchase agreement with the local government and electricity authority. The station, still in development, sits at a former World War II ammunition jetty. Could a revival of wave power in Portugal be on the cards? Recently EWP joined forces with Portuguese engineering and construction company Painhas. EWP’s role is to provide technical support for a 20 MW project being developed in a concession agreement with the port authority of Leixoes. Tidal test runs Although Europe is a stronghold of tidal research and development, the world’s largest power plant is found in South Korea at Lake Sihwa, with a capacity of 254 MW. Opened in 2011, the $560m project was financed by the South Korean government. Now Korea’s Institute of Ocean Science and Technology (KIOST) has contracted EMEC to help develop a tidal energy test site on the Jang-Juk Strait in Korea’s southwestern sea. It will have a 4.5 MW grid capacity and is
Renewables
expected to be operational by 2022. EMEC’s technical support for KIOST includes reviewing the cable layout, protection and maintenance, electrical infrastructure, and grid connection. Before Lake Sihwa came on stream, the La Rance tidal power plant in Brittany – capacity 240 MW and built between 1961 and 1966 – was the world’s biggest. Its barrage, spanning the Rance estuary, is 145 m long. Power is generated through 24 reversible bulb turbines with a rated capacity of 10 MW each. In terms of developing tidal power, the UK’s marine energy tech firms have a long global reach. Edinburgh-based Simec Atlantis (SA), for instance, is involved several projects in Asia. SA is providing the turbine and onshore systems for China’s largest tidal current demonstration project, part of a programme funded by the State Oceanic Administration (SOA). In April, a demonstration 18 m SG500 turbine was deployed at a grid-connected test site near Daishan, operating at 500 kW capacity. In Indonesia, SA is working with SBS International on delivering up to three 150 MW tidal stream projects around the islands of Bali and Lombok. A 10 MW demonstration phase is due to start next year. SA and SBS will deploy 24 m rotor diameter AR2000 turbines across all phases. Power will be sold to Indonesia’s stateowned electrical utility company PT Perusahaan Listrik Negara under a 30-year agreement. The total cost of the commercial array has been estimated at $750mn. SA is also working with Gujarat Power Corporation to complete the concept design and consent process for a 250 MW project in the Gulf of Kutch, north-west India. Gujarat has a long coastline, and the Ranwara Shoals create a shallow region through which flow is accelerated, ideal for deploying tidal turbines. The Gujarat state government has funded studies for the first 50 MW of a commercial scheme. Part of SA’s role is to monitor policy developments within the Ministry of New and Renewable Energy – the current focus is on developing other sites. In Japan, SA is providing a full AR-Series turbine system (turbine, foundation, cable and onshore infrastructure) under a lease agreement for a state-funded project in the Goto Islands. This was due to be installed in late November 2020.
Closer to home, the MeyGen tidal energy project will be one of world’s biggest upon its completion – boasting an expected output of around 400 MW. Located in the Pentland Firth off the north coast of Caithness, Scotland, the project is 77% owned by SA. In April 2018 MeyGen Phase 1A entered its 25-year operations phase. Since then, its four turbines have exported more than 30 GWh to the grid. The offshore lease currently permits up to 398 MW of tidal stream capacity to be installed and while MeyGen currently only has grid capacity for up to 252 MW, the site is capable of supporting the full project buildout. Commercial bids Energy World readers may recall EMEC’s Managing Director Neil Kermode reflecting recently that UK government policy towards marine power has hardly been conducive to rapid progress. Mustering all hands to deck could be the answer, at least if the momentum behind the AngloFrench Tidal Stream Industry Energiser Project (TIGER) is any indication. Its mission is to show that tidal stream energy is a maturing technology which, with revenue support, could lead to production costs becoming competitive. TIGER, which will last three years, launched in October 2019. It comprises 19 partners from the UK and France – a broad base of turbine developers, ocean energy demonstration sites, research bodies, and local and regional authorities. It was awarded €28m of EU money via the Interreg programme, to install up to 8 MW of generating capacity at sites around the south coast of England and the north of France. According to Interreg, the theoretical tidal energy capacity in the Channel region is nearly 4 GW, enough to power up to 3mn homes. Besides trying to prove that such energy can, in stages, become cheaper, it aims to develop a UK/ France supply chain. There’s a focus on reducing component and installation costs, alongside improving system reliability. Carolyn Reid, Programme Manager for Interreg France (Channel) England Programme, says the aim is to halve the generating costs of tidal stream energy from €300 per MW to €150 per MW by 2025, and to increase uptake. ‘TIGER has enabled collaboration between organisations in the UK and France that may otherwise never
Although Europe is a stronghold of tidal research and development, the world’s largest power plant is found in South Korea at Lake Sihwa, with a capacity of 254 MW
have happened,’ she says. In turn, costs should fall by ‘learning through doing’. Interreg is keen to see installations at tidal channels and headlands, and with varying types of turbine. EDF-Hydro’s open-sea test site at Paimpol-Bréhat in France will be upgraded to accept a wider range of turbine technology. In August, current and acoustic measurements were carried out there by SEENEOH, EDF and Bretagne Ocean Power, with certification of the turbine’s power curve being carried out by EMEC. The data will offer a better understanding of the environment and Paimpol-Bréhat’s potential for prospective tidal power developers. One of TIGER’s most ambitious schemes is Raz Blanchard, north of the Channel Islands in lower Normandy, home to France’s strongest tidal current. Normandie Hydrolliene, a joint venture between SA and regional development agency AD Normandie, has been established with the long-term ambition of harnessing up to 2 GW of power from the Alderney Race, the eight-mile strait running between Alderney and La Hague, France. In June 2020, Normandy’s prefecture approved the transfer of a 12 MW tidal power development lease to Normandie Hydroliennes. Tim Cornelius, CEO of SA, said this would enable immediate progress in developing of one Europe’s largest arrays and exploit Normandy’s ‘huge untapped’ tidal power. Raz Blanchard will explore the possibility of delivering energy profitably for less cost than the current offshore wind feed-in tariff of €150/MWh (for projects delivered between 2021-23); and creating a demonstration array using French-built RAR2000, 2 MW horizontal axis turbines. The plan is for a full multi-hundred-megawatt array to be online by 2024. Wealth of potential Ocean energy has been quietly making a case for itself for years – and it has expanded incrementally across the world. Whether it ever comes to be as prominent as wind or solar is a now a matter of government will and support. There is, quite literally, a wealth of potential energy in the world’s oceans just waiting to be harnessed. Ignoring it would seem like a tremendous waste. l
Energy World | December 2020 13
Renewables
BIOENERGY
What does sustainable biomass actually mean?
There’s no doubt that burning wood to make electricity produces less carbon emissions than burning coal – but does that make the process sustainable? It’s a controversial area, but here Nick Cottam sifts through the arguments of those on each side.
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n Friday 13 March 2020, shortly before the UK entered a prolonged period of COVID lockdown, the Zheng Zhi bulk carrier vessel docked at the Humber International Terminal in the Port of Immingham. Housed in this enormous ship’s hold were just under 64,000 tonnes of wood pellets from the US port of Baton Rouge in Louisiana, the largest ever biomass shipment, bound for the Drax Power Station in Selby, Yorkshire. As the Zheng Zhi nosed its way into Immingham, applause, praise and indeed some degree of The Zheng Zhi bulk carrier vessel docked at the Humber controversy were already echoing International Terminal around the port and beyond. delivering wood pellets from Biomass from plants, animal the US port of Baton Rouge for the Drax Power Station waste, charcoal and in this case, wood residue, currently Photo: Drax 16 Energy World | December 2020
contributes around 40% of the UK’s renewable energy. When burnt to generate electricity at Drax and other power plants around the UK it also produces several million tonnes of greenhouse gas emissions every year. However, despite its emissions, bioenergy is clearly cleaner and less polluting than the coal it is replacing, claim advocates. Not true, argue opponents. Bioenergy, they claim, is an expensive political stop gap which is itself doing significant damage to the environment. Targeting net zero Whichever way you look at it, the introduction of biomass and its resulting bioenergy has been an effective short-term political
fix as part of efforts to phase out coal and move towards net zero carbon emissions targets, both in the UK and elsewhere. Alongside the mighty Drax Power Station which over the past 10 years has converted four of its six generating units to biomass, there are now over 1,770 biomass power plants operating in the UK which, between them, have become an important part the energy mix. ‘Bioenergy from biomass and waste already plays a significant role in delivering low carbon heat, power and transport fuels in the UK,’ notes Hannah Evans of the Energy Systems Catapult, the UK energy technology R&D centre: ‘Our research in this area aims to highlight the importance of developing the bioenergy sector to deliver cost-effective emissions reductions.’ Like diesel for motor vehicles, bioenergy has been seen as a good political fix and a quick win in the drive to balance energy security with cutting carbon emissions. Just as coal has become the number one persona non grata in the low carbon energy mix, so biomass is seen by many, including our political leaders, as an acceptable substitute. There’s plenty of timber residues in the world, runs the argument, so why not burn it? What’s more, say advocates, providing the wood you burn comes from sustainably managed forests, there’s a convenient carbon offset built into the arrangement. The trees are replaced, the forests keep growing and while carbon emissions result from the burning of biomass, plenty of carbon is being taken out of the atmosphere by all those growing trees. Rising greenhouse gas emissions However, opponents such as the US-based Natural Resources Defense Council (NRDC) and the UK and US-based Biofuelwatch argue that trees simply can’t grow fast enough to absorb enough carbon to counter carbon emissions from bioenergy generation. In the UK, for example, greenhouse gas emissions from bioenergy rose from 4mn tonnes a year in 2010 to 15mn tonnes a year in 2017, but emissions from coal reduced by 20mn tonnes over the same period. So what happens to bioenergy in the medium and long term when the coal has been phased out? Needless to say, biomass sensitivities have heightened as demand for the fuel increases,
Renewables
driven by generous government subsidies. Over the past decade, Europe has significantly increased its use of renewable energy and about 50% of this has come from burning biomass. Like the UK, other countries are exhausting their home-grown residues of timber and turning to imports, some of them involving long haul shipments like the Zheng Zhi. According to climate expert Phillip Williamson of the University of East Anglia: ‘Replacing fossil fuels with biomass energy seems like a good idea, both nationally and at the global scale. But such policies haven’t been properly thought through and risk making matters worse, not better.’ He adds that: ‘even if further carbon dioxide releases can be prevented, the scale of bioenergy required seems likely to have serious land use implications, either at the expense of food production or resulting in natural habitat loss.’ Perhaps inevitably, carbon capture and storage is put forward as a viable mechanism to reduce carbon emissions from bioenergy. National Grid has stated that using carbon capture to trap bioenergy power plant emissions would mean that the electricity produced by bioenergy would save 62mn tonnes of carbon dioxide by 2050, the equivalent to about 13% of the UK’s total greenhouse gas emissions in 2019. According to the latest 2020 Outlook Report by the International Energy Agency, renewable energy capacity is set to expand by 50% between 2019 and 2024 and bioenergy will continue to be an important part of the mix. While solar PV is expected to lead the charge, accounting for almost 60% of the expected growth, bioenergy is on a par with offshore wind, with the greatest expansions in China, India and the EU. Generous subsidies Bioenergy growth in the UK has been backed by taxpayer largesse to the tune of millions of pounds. In 2016, according to the campaign group Biofuelwatch, energy companies received around £890mn in UK subsidies for generating electricity from bioenergy, and the vast majority of that came from burning wood. While new rules in the UK were introduced in 2018 to stop subsidies for new bioenergy power plants, the rules do not apply to existing facilities. This means that Drax Power Station, for example, the UK’s largest bioenergy burner,
Opponents such as the Natural Resources Defense Council and Biofuelwatch argue that trees simply can’t grow fast enough to absorb enough carbon to counter carbon emissions from bioenergy generation
will continue to receive subsidies of around £2mn a day. While Drax has its critics, the station continues to be an integral part of the UK energy mix and claims to take sustainability, including sustainable biomass sourcing, very seriously indeed. On 26 May 2020, for example, Drax supplied just under 14% of the UK’s electricity, delivering a consistent and responsive load unaffected by variations in weather or other technical factors. What’s more, says Drax Group Media Manager Selina Williams, all the wood burnt is sustainable: ‘We get two-thirds of our wood chips from managed forests in the south of the US, but none of this is virgin timber. This is residue timber that can’t be used anywhere else and all of it comes from growing forests.’ Drax and others on the side of bioenergy make the point forcefully that they are using timber that has locked up carbon, helping to offset carbon emissions when the timber is burnt for energy. ‘We never cause deforestation, forest decline or carbon debt,’ adds Williams. ‘We’re independently audited and our biomass complies with and in many cases goes beyond stringent standards set by Ofgem and the EU.’ Sustainable sourcing While opponents such as NRDC highlight forest decline and the time taken for new trees to absorb significant amounts of carbon, Williams insists that Drax will only source from forests that are growing at a greater rate than the material that is harvested. ‘The forests we source in the US South have doubled in growth since the 1950s,’ she adds. While it’s clear that the sourcing of residue timber for bioenergy – doesn’t drive the forestry industry, there is little doubt that the growing demand for biomass has had an impact and, in the view of many, changes the economics. The ‘Cut Carbon not Forests’ campaign is among the more vociferous opponents to the growth in bioenergy generation. ‘The climate emergency requires us to build a genuinely clean energy economy and end wasteful subsidies for dirty biomass energy,’ said Almuth Ernsting, Co-Director of Biofuelwatch, which is part of the campaign. ‘Cutting down trees, shipping them from forests overseas and burning them in power plants was never compatible with the need to keep global warming to 1.5°C,’ she adds.
Without further reform, argues the campaign, UK energy bill payers will spend £13bn in direct support to large biomass power plants between now and 2027. Drax, it says, will account for £10bn of this money, as well as being exempt from paying carbon taxes. The campaign argues that climate change and biodiversity are inextricably linked, the priority being to keep forests standing where at all possible. To understand the polarity of arguments for and against the growth in timber for biomass you only have to compare contrasting images published by the NRDC and by Drax. The former presents blighted areas of cleared forest, while the latter shows responsible forestry management in its latest sustainability report. In the case of Drax, it’s all about responsible sourcing and in the US South, notes the company, forest harvest statistics show that biomass accounts for just 3% of the material harvested. Supporting woodland management Other smaller UK bioenergy operators also highlight their approach to climate change and the responsible sourcing of timber. For example the Kent Renewable Energy biomass plant at Dover, which opened in 2018, claims to be saving over 100,000 tonnes of carbon dioxide a year. As part of this process the company says it is playing a part in ‘reinvigorating the woodlands of south-east England’, and supporting local coppicing, which is leading to a higher proportion of the region’s 320,000 ha acres of woodland being actively managed. ‘Unmanaged woodlands represent a huge opportunity in terms of carbon balances, biodiversity management, employment opportunities and productive potential,’ notes the company. ‘By providing a significant local market for low-grade wood, our power plant is re-vitalising local forestry.’ In contrast to Drax, the Kent plant is tapping into home-grown timber, not all of it residue, and making a virtue of promoting local forestry and all its various offshoots. The 27 MW plant highlights its capacity to supply electricity to 50,000 homes – more load, more coppicing but undoubtedly some impact on biodiversity. Whether this counts as sustainable bioenergy remains open to debate. l
Energy World | December 2020 17
Fossil fuels
COAL-TO-POWER
Asia moves towards ‘highefficiency, low-emissions’ coal power F rom a European or American perspective, it has become easy to think that coal power is a dying technology. However, it bears remembering that coal remains, by some distance, the largest source of power generation worldwide, and it has increased more than any other source even over the last two decades. This remarkable proliferation has been driven by rapidly growing Asian economies, where coal represents readily available, low-cost power and energy security. For these countries, coal power plants are not relics of an industrial past, but the engines of an industrialising present. Well over half of the world’s current 2 TW of coal capacity was built in the last 20 years, and over 90% of that expansion has taken place in Asia – primarily in China, but also India, and increasingly South-East Asia, Pakistan, and Bangladesh. Most forecasts see a gradual levelling off in global coal capacity over the next two decades, as decline in the West is offset by continuing growth in these markets and new ones in Africa. Over 140 GW of new coal capacity is currently under construction, and more is planned. Given the undeniable toll of coal-fired power generation on the environment, both in terms of climate change and impact on air and water quality, there is an urgent need to ensure the best available technologies are used for new and existing plants. Tough coal phase-out policies of the kind being implemented in many European countries are simply not feasible for economies with rapidly growing energy demand, especially where access to natural gas is limited. The recently built plants are therefore here to stay for at least a couple of decades, and need cleaning up. In the coal power industry, the contentious term ‘clean coal’ is being increasingly replaced by ‘HELE’ – high-
22 Energy World | December 2020
Like it or not, the outlook for coal and coal-fired power stations is very different in Asia than in Europe and North America. So it’s important that power plants there employ the least polluting and most efficient technology options, argues Toby Lockwood of the IEA Clean Coal Centre.
Shenergy-operated Waigaoqiao 3 has implemented a series of efficiency upgrading technologies to become one of the most efficient coal power plants in China Photo: IEA Clean Coal Centre
efficiency, low-emissions. Whatever the terminology, the focus is on more efficient power plants which generate less carbon dioxide (CO2) per kWh of energy generated, as well as on flue gas cleaning equipment which can scrub out pollution like sulphur dioxide (SO2), oxides of nitrogen (NOx), particulates, mercury and, ultimately, CO2. Bigger, hotter, more efficient plants Since the first coal power plant fired up in London nearly 140 years ago, the technology has got progressively bigger, hotter and more efficient – see Figure 1 and Table 1. Raising steam at higher
temperatures and pressures is the key to running turbines at higher efficiency and, since the 1960s, the best plants have used ‘supercritical steam’ – the phase of water which behaves somewhere between a liquid and a gas – allowing efficiencies of up to around 43%. Efforts to push the boundaries of coal plant efficiency have always been dictated by materials. In the early 1990s, new types of steel (Gr 91, then Gr 92) allowed a new generation of plants dubbed ‘ultrasupercritical’ or USC. Although steadily improved to reach up to 47.5% efficiency (600–620°C steam), this fundamental design still represents the state of the art in coal power, and is increasingly adopted even in lower-income economies such as Bangladesh, Indonesia, and Vietnam. India commissioned its first USC power plant last year, while the technology already represents nearly a quarter of China’s fleet. Although these efficiency improvements may seem incremental, such is the scale of global coal power, that raising the global average efficiency to the state of the art would equate to a CO2 saving of around 2bn tonnes. With steam conditions pushing steels to the limits of their capabilities, for around 20 years the obvious next step for coal power has been thought to require use of the nickel-based ‘superalloys’ used in jet engines, which could allow a leap to over 700°C steam and 50% efficiency. Unfortunately, developing these materials for use in the envisaged ‘advanced ultrasupercritical’ (AUSC) coal plant has been a slow
Fossil fuels
Table 1. Typical operating parameters of the different generations of coal power plant
and difficult process which has struggled against declining interest in coal in the EU and the US. More recently, India has taken up the baton of this research, and is looking to back development of a full-scale plant in the next few years. Perhaps more promisingly, efforts to make the jump to AUSC plant have also given rise to new steels and technologies which have unlocked a more incremental progression. GE typified this approach with its never-realised ‘SteamH’ design released in 2017, which used advanced steels and minimal nickel alloys to reach 650°C main steam temperature and over 49% efficiency. However, since GE’s recent exit from new coal, the market has been left largely to Chinese, Japanese and Korean manufacturers. In China, there is also a drive towards 650°C, as well as innovation in steam cycle design such as the idea of raising the turbine close to the top of the boiler (where the hottest steam is produced), thereby minimising pressure drops and the need for costly steam piping.
Coal remains, by some distance, the largest source of power generation worldwide, and it has increased more than any other source even over the last two decades
Shanghai-based company Shenergy is close to realising this concept on a 1,350 MW unit at Pingshan power plant, where an efficiency of over 49% is targeted. This unit also uses a double reheat cycle, in which steam is twice reheated and re-run through the turbine. This higher-efficiency design has been around for years, once breaking records at Denmark’s Nordjylland plant, but is currently experiencing a revival in China as a means of getting the most out of USC technology. Gasification options An alternative vision for coal power is to exploit the high efficiency of gas turbines by first converting the coal to syngas (a mix of carbon monoxide and hydrogen) in a gasifier. This can then be used to fuel a combined cycle gas turbine in an arrangement known as an integrated gasification combined cycle (IGCC). This concept has, again, struggled historically, as early demonstrations in the US and Europe in the 1990s were soon seen as costly and overly complex relative to advancing
Figure 1. The reduction in carbon dioxide emissions intensity with increasing efficiency
USC technology. Today, the technology lives on in Japan, where Mitsubishi is soon expected to commission two new 540 MW IGCC units in Fukushima. Designed to reach 48% efficiency, these plants are seen as well suited to dealing with coal containing low-melting point ash, which can damage conventional steam boilers. A more novel variant is being trialled at Japan’s Osaki Coolgen project, where coal-derived hydrogen will be fed to a highefficiency, solid oxide fuel cell. Smarter analytics Given the sheer scale of coal power deployed in the past decade, ensuring that the existing plants run as cleanly as possible is arguably of even greater importance than developing new designs. To this end, the coal power sector is making increasing use of ‘digitalisation’ – gathering more data and running ever-smarter analytics and control systems in order to keep power plants running at the sweet spot of high efficiency and low emissions. This has become even more essential as coal plants are increasingly required to ramp their output up and down as flexible back-up to wind and solar, presenting a complex and dynamic problem for control systems. Plant operators can now run ‘digital twins’ or simulations of plant processes to help optimise and explore the range of its capabilities. Greater connectivity is also allowing manufacturers to monitor and tune their equipment from remote control centres. In this respect, the coal technology business is increasingly a service industry. For major improvements in the efficiency of older, ‘subcritical’ plant types, changes not just to software, but to hardware are needed. Stringent efficiency standards for all coal units in China have driven in interest in ambitious unit upgrades, such as the Xuzhou project, where replacing key components of the boiler and turbine allowed an increase in temperature from Energy World | December 2020 23
Fossil fuels
538 to 600°C – essentially converting the unit to near-USC efficiency levels.
why a coal plant should pollute any more than a gas-fired plant.
Air quality issues Negative perceptions of coal power are mostly fuelled by its more visible, near-term impact on air quality, through emissions of harmful particulates and the acidic gases SO2 and NOx. As technologies to remove these pollutants from coal flue gas have existed for many years, the main challenge is to ensure they are as deployed as widely as possible. While most plants worldwide are equipped with electrostatic precipitators or bag filters to remove particulates, control measures for SO2 and NOx are only recently being legislated for in major coal-users such as India, Indonesia, and South Africa. Following a stringent crackdown on air pollution over the last decade, China has led the way in optimising existing flue gas desulphurisation and NOx removal technologies, with some plants achieving below 20 mg/m3 concentrations of both pollutants – compared with limits of 100–200 mg/m3 coming into force in the EU. On this front, there is no reason
Carbon capture and storage The ultimate goal for coal power is to properly tackle the problem of CO2 emissions with carbon capture and storage (CCS) technology, which could remove up to 98% of the greenhouse gas emitted (although 90% is a more common target). Despite a spate of international interest in applying CO2 capture to coal power plants around 2010, only two facilities were realised – Boundary Dam 3 in Canada and the Petra Nova project in Texas, which both benefit from the use of captured CO2 to boost oil well production. A recent revival in CCS has sought to reframe the technology as a solution for non-power sector emissions, but interest in coal power remains in the USA, where five new full-scale projects are currently in the design stage. While developments in China have so far been limited, the country’s recently announced aim of reaching net-zero by 2060 must surely require a major role for CCS.
the last 20 years. Just as coal power plants have multiplied across Asia, declining interest in Europe and North America has often helped put the brakes on development of the very technologies needed to address this growing problem. Technology developers in India and China have taken up the challenge, often going further than counterparts in the West, while Japan retains its role as an exporter of some of the most high-tech plants. However, unconstrained by OECD lending rules, China is also happy to build and finance less efficient plants in new markets such as Africa. There is a real danger in losing institutional expertise and technological capability as leading manufacturers and researchers leave the game, just as there is more need than ever for new solutions. l
Given the undeniable toll of coal-fired power generation on the environment, there is an urgent need to ensure the best available technologies are used for new and existing plants
Toby Lockwood is a Senior Analyst at the IEA Clean Coal Centre
From the US/Europe to Asia There is some irony in the story of coal technology development over
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