|The recently commissioned BoA 2&3 in Germany is seen as one of the most advanced lignite-fired power stations in the world
With 170,000 power generation units at more than 75,000 plant sites in over 230 countries around the globe, the energy industry accounts for 29 per cent of greenhouse gas emissions globally, according to European Environment Agency statistics. That figure is 11 percentage points more than the figure for road transport, the next largest sector for greenhouse gas emissions.
Legislation governing emissions from the power generation sector is now embedded in most countries, although it is being implemented at differing speeds. A global focus on carbon emissions is emerging, even if each country sets its own priorities. But, unlike sectors such as marine fuels, no overarching international legislation applies. National legislation, such at The Clean Air Act in the US, currently places a heavier burden on developed economies.
The three key factors that already – and will continue to – significant affect the global power generation industry are: carbon pricing, energy efficiency and renewable energy.
National and regional legislation sets deadlines for cutting carbon footprints. Most countries have a target of 15–25 per cent by 2020. Some jurisdictions, such as Europe, Mexico, Brazil, South Africa and South Korea, have set themselves much higher targets. But all countries are committed to reducing their respective carbon footprints by 80 per cent by 2050. These targets have been agreed in the knowledge that all countries aspire to grow and will need more energy to fuel that growth.
NOx, SO2 and mercury limits
Nitrogen oxides (NOx) are considered a pollutant and their emissions are limited. In Japan, NOx regulations are especially stringent, according to Hiroshi Suganuma, manager of the Boiler Planning Section at Mitsubishi Heavy Industries.
“We have to reduce NOx through low-NOx combustion systems, which consist of a low-NOx PM burner, in-furnace de-NOx system (MACT) and Mitsubishi rotary separator (MRS) mill. If NOx regulation becomes more stringent, we will additionally use SCR, which is a dry selective catalytic NOx removal system, located just downstream of the boiler.”
Meanwhile, all developed economies set limits on how much sulphur dioxide (SO2) power stations can emit. For coal-fired plants, legislation on mercury has also become an issue. Sal Esposito, global product manager at GE Water and Process Technologies, says: “Limits on mercury emissions in the US will take effect by 2015 and we expect other regions, particularly China, will soon follow”.
Law governing power generation around the world is both complex and controversial. The demand for low-cost electricity inevitably conflicts with the need to control exhaust gas emissions. Emission regulations have effectively brought construction of new coal facilities in Europe to a standstill.
Environmental legislation will continue to influence the power generation industry over the next eight to 38 years, as countries approach carbon footprint or greenhouse gas emission targets for 2020 and 2050, which could open an opportunity for OEMs and chemicals suppliers to provide energy-efficient solutions for existing and new power plants.
Shifting fuel trends
Nuclear energy is zero carbon, but the high cost of investment, along with post-Fukushima safety concerns and demands from private sector contractors for uneconomic subsidies, have undermined government support. The burning of fossil fuels shows no signs of abating. Energy diversification has become a key driver and coal is now the main power source supporting economic growth in Asia and other emerging markets.
Vast reserves of coal lie under regions such as China and Indonesia. Meanwhile, low-cost shale gas has reinvigorated the US energy market.
But new, clean energy sources such as solar and wind – which are uneconomic without subsidies – are intermittent and require boosting with other conventional forms of generation to meet demand. Collectively, they generate just over 1 per cent of global energy needs.
This all ensures fossil fuels will continue to dominate the landscape for at least the next generation. “Fossil fuels will remain the largest contributor to the energy mix in the decades to come, especially due to growth in China, India and Asia Pacific,” says Lothar Balling, head of gas turbine power plant solutions in the Fossil Power Generation Division of Siemens Energy.
Reliance on fossil fuels is underpinned by rising global demand for electricity to drive economic growth. “By the year 2030, annual electricity consumption worldwide is expected to rise from today’s level of 20,000 billion kWh to 37,000 billion kWh,” adds Balling.
Auto-generation and decentralised plants using reciprocating engines will also become more important, particularly in countries without an adequate transmission network, such as in Africa, where industries need to generate their own power for security of supply.
Kentaro Hosomi, general manager of the Business Development and Strategic Planning Department at Mitsubishi, believes the European economic downturn has slowed the installation of carbon dioxide (CO2) limiting technology: “When the European economy was growing, everybody thought this was coming very soon because countries could afford to pay for such technology, but now it seems that this is going to be delayed.”
Indeed, signs that economic support for renewables may be falling started to emerge in July when the UK government announced a 10 per cent reduction on subsidies for wind and other renewables, accompanied by a ‘dash for gas’ tax break. This and the lower cost per MW of combined-cycle gas turbines, promptly triggered an investment decision by British Gas/GDF Suez. Gas already accounts for 40 per cent of UK electrical energy generation and is now set to add 49 GW of additional capacity by 2020.
Current & future fuel preferences
The current reliance on fossil fuels among the leading nations in electricity generation from each fuel is shown in Figure 1. Generation from coal , gas and oil is displayed separately, revealing the clear dominance of coal and gas over oil, as well as the vast slice of global consumption contributed by China and the US. Japan shows the most diversified use of all three fuels. Russia is focused on gas and Germany on coal.
|Figure 1: How fossil fuels contribute to generation among the nations that use them most for power
Source: EIA International Energy Outlook 2011
Trends towards one fuel type over another are emerging in key regions. Jim Donohue, manager of thermal products marketing at GE Power, confirms the US trend towards gas. “With emissions and mercury legislation, new coal is almost impossible unless you have some type of carbon capture and sequestration, which adds another layer of cost and complexity. So natural gas becomes kind of the logical choice. So we’re optimistic that the gas turbine segment in the US is going to ramp up; it’s going to be a robust market as we go forward.”
This view is shared by Glen Carnavera, vice president of marketing at NAES, a major US-based O&M services provider, with 30 GW under contract. “The use of coal in the US is falling because gas is cheap and combined-cycle gas turbines are inexpensive and fast to build.” His view is shared by Mitsubishi’s Hosomi: “About 60 per cent of our turnover comes from the combined-cycle gas turbine business.”
But outside the US, GE sees coal as the driver. “If you look at the big drivers, the growth in the non-OECD countries in places like India, China, it’s just explosive growth and a huge population that is basically under-served from an electricity standpoint. What you’re seeing in a lot of those countries is they’re still installing huge amounts of coal capacity,” says Donohue
Jeffrey Goldmeer, fuel flexibility platform leader for F-Class heavy duty gas turbines at GE Power & Water, sums up the global picture: “It’s a regional plight – there are some places in the world where coal is more abundant and cheaper and therefore their power production tends to really rely on coal. Then there are other places where natural gas is very abundant and low cost and therefore you don’t see a large play from coal.
“China is a prime example of where coal is abundant and cheap, and China continues to look at ways to leverage its coal resources for power generation, versus, in the US, natural gas prices are currently at about $3. There are coal boilers switching from coal firing to natural gas firing in the US right now.”
Balling of Siemens confirms demand for coal: “Many countries have substantial coal reserves and coal will remain plentiful for years to come, however emissions and flexibility might shift power generation towards gas.”
David Martin, marketing manager at Fireside Chemical Treatment at Nalco, perceives a new trend in Europe towards biomass, which is theoretically zero net carbon as the carbon emitted is absorbed by new plant growth. “There is a strong push to convert a high percentage of electric generation from coal to biomass burning; that could be wood, various types of vegetation, agricultural goods or the related waste products.”
Future demand for electricity
The US Energy Information Administration (EIA) predictions support the views of industry suppliers that consumption of electricity will grow much faster in non-OECD than in OECD countries. This imbalance has a direct bearing on fuel types burned to generate this increased demand for power, as Figure 2 demonstrates.
|Figure 2: Non-OECD electricity consumption is set to outstrip power demand in developed nations
Source: EIA International Energy Outlook 2011
In summary, oil consumption for power generation will remain low in both OECD and non-OECD regions. Natural gas will almost double in the non-OECD region and grow by 50 per cent across OECD nations. But the most dramatic increase will be in the demand for coal, which will rise from its already high base by 43 per cent in non-OECD countries and remain the dominant fuel – mainly due to the surge in coal plants in China and India. Meanwhile, renewables will also expand exponentially in both regions.
This all has implications for OEMs and chemical suppliers, who will need to provide the technical solutions demanded by their power station customers in a landscape dominated by fossil fuels and renewables.
The cost of reduced emissions
Dr Mark Picton, commercial operations manager (Aberthaw) at RWE npower in the UK, sums up the cost impact of emissions reduction: “Environmental legislation is huge, by far the biggest challenge we face in the industry. At Aberthaw with the advent of the [European Union’s] IED [Industrial Emissions Directive] in 2016 we face major tightening limits on our operational NOx. We are looking at installing technologies to meet those new NOx requirements such as SCR [selective catalytic reduction]. No solution is less than several hundred million pounds.”
The price of gas is driving change in the US. Lower-cost electricity from gas means that coal-fired stations need less expensive coal. As a result, lower grade or ‘opportunity coals’, such as Northern Appalachian or Illinois Basin coals, are being burned.
|GE’s 7F heavy duty gas turbine is designed to run on syngas from carbon-based fuels such as coal
This problem is mirrored in Japan, says Mitsubishi’s Suganuma. But these coals can cause problems: “Indonesian coal has very high moisture, so the slagging and fouling properties – dirtiness in the furnace – are high”. Indonesian coal now represents 18 per cent of Japanese imports, according to Mitsubishi.
Esposito of GE puts the choices faced by some US coal plants succinctly: “For the first time in recent history you’ve got gas-fired generation that is more economical than coal and it’s pushing the coal plants further and further down the dispatch queue.”
Esposito describes it as a “survival mechanism” and says some coal plants face a stark choice: “For plants that are unable to burn these lower-cost coals, either because of their location [distance from the coal source] or other technical reasons, the cost of their generation is now at the point where it’s not economical to keep those plants online so we have a number of coal plants in the US that are actually beginning to shutdown.”
But this is not just a US phenomenon, he adds. “In China, the coal demand continues to increase and they have a huge demand for steel, so they want to divert the better grade coals to steelmaking and keep the cost of power generation as low as possible”.
Phil Ray, lead performance engineer at the EDF West Burton plant in the UK, confirms the trend: “Everything nowadays revolves around environmental compliance. We’re constantly looking for cheaper coals but that can affect efficiency and environmental compliance, it can give us challenges and output issues, if we can’t make the load.”
A UK plant manager confirms: “Coal varies hugely across the world – we could end up with coal that causes severe clinking in the pipes or with very high fines.” This view is echoed by Ken Riddle, supervisor of chemical processes at Lakeland Electric power plant in Florida, US. “Opportunity coals are higher in iron and slagging and harder to utilise.”
Valery Klyushkin, chief engineer of Krasnoyarsk in Russia, says impurities in coal – earth and sand – cause bottom ash to form and clog boiler furnaces. And Charles Soothill, senior vice president of technology at Alstom, agrees. “The secret is to understand how those liquid ashes behave and whether they will stick to the walls. That makes a big impact on how you design the plant. That’s why having a strong database of fuel is very important.”
Biomass can also cause its own problems: “Low-quality biomass fuel will produce a lot of sinter and dust in the furnaces which leads to more down time,” says Qinghua Wang of Guoxin Huaian biomass power plant in China.
Indeed, while the power generation sector’s future looks firmly set on the twin tracks of rising demand and growing environmental concern, the technical challenges this will bring are yet to be clarified.