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?Mauritius needs a secure power supply?
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?Mauritius needs a secure power supply?
● ?Gasification? is often cited as a means for Mauritius to reduce its dependence on fossil fuels. Yet very few people understand what it actually means. Could you explain this technology in layman?s terms?
Gasification is simply a way of converting a solid fuel, such as a biomass, into some kind of gas. This gas can then be used for other purposes and be cleaned in a way that solids can?t. If you use fuel like bagasse or cane trash, convert it into an energy carrier like a gas and then clean the contaminants, which were in the fuel originally, it makes it easier to use the gas in other applications where you need a clean gas, such as motor engines and, in this case, gas turbines. A gas turbine combined cycle, for example, combines a gas turbine, the exhaust gas from which goes a boiler, and a steam turbine which is driven by steam. This is the highest efficiency thermal cycle available. It?s a great advantage if you can go from a green fuel such as biomass, clean the gas and then use one of the most advanced power cycles available.
● A great advantage indeed! But how widely is this technology used?
At the moment, gasification has not reached the stage where the power generation in advanced cycles has been tested in more than two installations in the world. The commercial aim is to use the gas after some rudimentary cleaning to fire a coal-fired boiler. You can then use biomass to replace coal by placing the gasifier inside a coal-fired power station. This means you don?t need to install new boilers and turbines. So the existing infrastructure is put to use and you reduce the amount of fossil fuels while still getting good efficiency. Two installations are in operation in the power industry in Europe. Since the oil crisis thirty years ago, there have been four or five such installations in the paper and pulp industry. These don?t generate power but replace fuel oils in the limekilns.
● This technology sounds almost too good to be true. There must be a catch somewhere. How expensive is gasification?</B>
Nobody really knows. There?ve only been two small installations of four MW in the world. These turbines, which can be seen as prototypes, are about 50-100% more costly than conventional small biomass stations. There is talk however of building plants with an output 20 to 80 Megawatts for commercial use.
● Is it safe to say that we?re going to be seeing a lot more of gasification in the coming years?</B>
Yes, but it depends on the drivers. This technology allows you to get more efficiency out of the same quantity of biomass. The use of biomass is related to crop area. Gasification can give you 50% more power output from a given crop area. If you project costs for the long-term future there?s no evidence that it would be more costly than conventional biomass technology for an operation of the same size. Of course, long-term is a relative term. In the 1980s and 1990s, there was a big push by power companies, but the verdicts of operating two gas-cleaning prototypes in Sweden and the UK have been mitigated. To get the operating costs down these plants have to be used for several years and the experiences learned from. If there are many drivers, you can have a rapid succession of new plants. On the other hand, if the drivers are limited then the process could drag on for a long-time.
● Expensive fossil fuels, a push to cut carbon emissions. The necessary drivers seem to be present?</B>
The cost of fossil fuels is certainly a driver, as is the cost of power. There?s also a premium for using renewable energy. Increasingly, there are legal obligations, such as the Kyoto Protocol, to cut emissions. The drivers are reunited but carbon sequestration is a major issue. Carbon sequestration is the removal of carbon dioxide from coal-fired power stations and its deep-sea storage or whatever. There are moves to make it compulsory by 2020. In Europe, biomass accounts for a fairly small amount of energy production. Power companies tend to safeguard their assets by engaging in carbon sequestration. That?s one reason why there?s been a departure from the technology.
● You have extensive experience working in another big sugar-producing country, Brazil. What can Mauritius learn from the Brazilian experience?</B>
Brazil is expecting to increase its cane by 50% in the next five years. There are establishing new mills and cultivation areas. The new mills will have more advanced steam boilers with higher pressures for power cogeneration. In Mauritius, the harvest is done by burning the fields and cutting the stalks. In Sao Paolo state, for example, they are legally obliged to avoid doing this because of air pollution. Instead, they have mechanical harvesting and what doesn?t go to the mill is removed and used to extend cogeneration beyond the harvest. They already have the resources, logistics and know-how to exploit three types of biomass: palm oil, sugar cane and the forest industry.
<I>?If you project costs for the long-term future there?s no evidence that it would be more costly than conventional biomass technology for an operation of the same size.?</I>
● Is gasification a viable option for Mauritius? </B>
Most of the mills that are still in operation have already gone through the transition of being a sugar mill to being a cogeneration plant operating on coal and bagasse. The first step of energy efficiency has already been taken. This makes using gasification here more difficult because they are already on their way of using a different system. In Brazil, they have integrated projects that look at green harvesting, agronomics, weed control, fuel characteristics, and the integration of gasification in the plant. The indicators there are very positive. You can increase power to 300 kilowatts per ton of cane. A single power plant could generate 300 gigawatts/hour per year instead of 200 gigawatts/ hour per year from the same quantity of fuel. The problem is that there is no long-term performance data for this technology, whereas cogeneration technology is established and bankable. Because these plants are the first of their kind, the installation costs are higher. In Brazil, the mills received grants from the Global Environment Facility and the World Bank to reduce upfront costs to an economically viable level.
In the long-term, Mauritius has a need for a secure power supply. There will also probably be new obligations to reduce fossil fuel usage. This technology could assist in this process. I?ve been in gasification for most of my professional life and I promote it at every opportunity I get. Yet with time one discovers that expectations should be realistic. A state-of-the-art coal-fired power station, which can be operational within 18 months. With gasification this is not possible yet. Mauritius can still learn from using the technology on a smaller scale so that the country?s ready when the technology becomes commercially viable.
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