Tomorrow`s energy: Today`s challenge
Aware of its past and dealing with its problems in the present, the global power industry is poised to solve its future problems now
Dr. M.P. Boyce
Boyce Engineering International Inc.
In the great cosmic scale of things, the human species has been in existence on this planet for a very short geological span of time, but the effects of homosapiens` development and the inexorable march of modern science and technology have been truly global. Advances in agriculture and medicine now mean that more people are living longer and advances in every branch of industrial technology creates a correspondingly greater individual demand on the earth`s natural resources. Given the ability to exploit our available non-renewable energy resources to the point of total depletion, one of the greatest changes now facing our species is the development of new and renewable sources of energy and more immediately, the conservation of existing reserves by using them more efficiently.
In the beginning
By the beginning of the twentieth century, the effect of increased demand on natural resources had already become more noticeable in western nations where industrialization had gathered pace. Steam power was giving way to electricity as a prime source of energy, but it was largely generated by coal-fueled power plants and the impact on the environment increased dramatically. Little or no thought was given to the consequences of uncontrolled coal burning and even though gas had become a widely-used fuel for both domestic and industrial use, the coal-to-gas conversion process was itself a major source of pollution. Even less consideration was given to the future availability of energy from natural resources, as coal supplies were considered virtually inexhaustible.
Energy demand in the industrialized nations underwent explosive growth following World War II. During the post-war period, the fastest-growing industrialized nations had an annual gross national product growth rate reaching more than 10 percent throughout the 1960s. At the same time, there was a significant demographic shift towards urban areas and the national energy demand, particularly in population centers, grew dramatically.
Very little attention was given to the impact on the environment and as a result, cities became so polluted that the scale of pollution-related illness caused a major political upheaval, with drastic legislation taking place. New national anti-pollution laws were passed, forcing the power and energy industries in particular to adopt a completely new approach. Coal-burning power generation was phased out completely in some countries and replaced by low-sulfur, oil and natural gas-fueled thermal plants. Fuel and energy costs skyrocketed, but the cost to the environment and its political implications made the price worth paying.
It is interesting to note that these changes in national attitude to energy and power generation were taking place at a time when the use of natural gas as a source of `clean` energy was almost unknown in the United Kingdom and industrialized Europe.
Although the disastrous levels of pollution from lignite and orimulsion-fired power stations in eastern Europe have been forcefully brought to the notice of the industrialized West in recent years, it is only recently that we have started to clean up our own act. A staggering 80 percent of the UK`s baseload power is generated from the coal-fired thermal power stations, although a number have installed desulfurization equipment to reduce emissions.
In India and China where the speed and scale of industrial growth is creating an enormous demand for additional electrical power, the financial burden of building large new power stations has led to a drive to use existing plants more efficiently. The use of very long-distance power transmission systems using high-voltage, direct-current overhead lines is being widely adopted to dispatch power to distant urban population centers from large, existing generating plants. The technique is also being used to interconnect widely-separated regional grid networks and different types of power generating plant, to take advantage of regional variations in demand. Nevertheless, baseload generation in both India and China will continue to use coal-fired thermal plants on an increasing scale for the foreseeable future.
Although Asian countries are experiencing the fastest increase in demand for electrical power, the Western industrialized nations are also steadily increasing their own consumption. A continuously increasing drain on all fossil fuels is therefore occurring throughout the world and the once infinitely available resources of fuel are now recognized as being all too finite. At the current rate of consumption our major reserves of coal are forecast to last for just another 250 years. Natural gas reserves are dwindling even faster to give approximately 60 years of supply, while oil reserves will be exhausted in only 40 years` time.
A major and growing user of nuclear power to supply its energy needs, Japan generates approximately a quarter of its total requirement from nuclear power stations. Nuclear fission technology has provided a clean, efficient and non-pollution source of power generation for close to 40 years, but when accidents have occurred, they have had consequences on a global scale. The world`s worst and most recent incident took place at the Chernobyl reactor in the former Soviet Union, with perhaps the Three Mile Island accident in the United States running a close second in public perception of seriousness. An accidental discharge of radiation at one of the UK`s earliest generation of reactors at Windscale in Cumbria is now recognized to have been far more serious than was initially thought.
It is quite certain that a very large proportion of our total energy needs will eventually be met by nuclear-generated power and new reactors using the latest systems and technology are being constructed and entering service worldwide. However, public resistance to nuclear power is widespread, understandable and a major factor in planning new installations.
Stemming not just from the operational dangers of nuclear reactors but from concerns at local, national and international levels over the issues surrounding the disposal of highly toxic nuclear waste, the high degree of public awareness and concerns has forced the industry to adopt increasingly stringent safety standards at an ever-increasing cost. The latest 1,200-MW nuclear PWR power station in the United Kingdom now undergoing final commissioning at Sizewell in Suffolk uses an advanced version of the Westinghouse light water reactor first used for propulsion in nuclear submarines. This design now incorporates unprecedented levels of safety protection. In addition to the multiple steel and concrete layers within the double containment building of the reactor pressure vessel, two separate and independent protection systems have been installed.
Housed in separate buildings, connected by cabling in separate fire and explosion-proof ducting, the systems are themselves quite separate from the main station controls. Each of the two systems measures every safety parameter on four independent channels to give an effective quadruple safety back-up on a double system.
The depressing prospect of an energy-hungry world rapidly running out of natural resources while polluting itself to death is offset by an increasing awareness on a global scale of the need to conserve existing finite resources, while developing renewable energy options. Front runners in the renewable or alternative energy stakes are wind power, hydroelectric power, tidal and wave-energy, solar, geothermal and biomass-powered generation.
Despite objections on the grounds of noise and visual appearance, wind turbines have an impeccable environmental pedigree, the energy source being non-polluting and inexhaustible. But with a commercial and practical maximum capacity of 500 kW for each generator, they are relatively low-powered, expensive to install and control and have yet to win wide acceptance in mainstream electrical supply markets on economic grounds.
Hydroelectric power generation schemes are in operations worldwide and represent quite mature technology. Clean and non-polluting, they nevertheless have a major impact on the environment through the large-scale flooding of areas upstream of the power plant and cause significant changes in flow rates on the downstream side. The world`s largest hydroelectric scheme is being planned in the Peoples Republic of China at the Three Gorges complex on the Yangtse. When completed this project will provide 24 GW of power. Together with biomass-fueled generation, hydroelectric-power supplies nearly one-fifth of the world`s energy requirement.
Technology currently exists to construct a massive tidal barrage on the mouth of the Amazon and transmit enough bulk power over an high-voltage, direct-current link to supply the needs of a country the size of the United Kingdom for an the indefinite period. Unfortunately, due to political and financial restraints this type of project is not practical. At present, tidal and wave power, together with solar and geothermal power sources, supply a very small fraction of the total global energy requirement.
Measures to conserve energy and natural resources through improved plant efficiency and with the application of new technologies are gathering pace. Although the use of aero-derivative gas turbines in industrial power generation is far from new, developments in the application and control of turbomachinery are now providing major increases in both operational and thermal efficiency of generating plant.
Global gas turbines
On a world scale, by far the largest percentage of new power generating plants currently being planned and installed is gas turbine-powered. In the United Kingdom, the `dash for gas` is represented by the widespread and increasing installation of this form of power plant, both by the two major non-nuclear utilities, the regional electricity companies and by a growing number of other independent operators. Tailored to precise operating requirements, installations range from simple-cycle to complex cogeneration and very high efficiency combined-cycle power generation. The capacities of these plants range from a few megawatts to baseload stations of several hundred megawatts. The areo-derivative and industrial gas turbines which provide the prime motive energy are principally fueled by natural gas. However, they can also be powered directly and indirectly by a variety of other fuels including oil and coal.
Using the latest `green` coal gasification technology, finely pulverized coal, mixed with steam or water, is treated with pure oxygen to create oxidation at high temperature and pressure. Cooled and desulfurized, the resulting synthetic gas, which is a mixture of carbon monoxide and hydrogen, is fed directly to the gas turbine. Existing fossil-fueled thermal generating plants can also be up-rated by installing an additional gas turbine generator to directly increase the generated capacity. The hot exhaust gases are then fed to the existing heat-exchanger, supplementing the output and significantly increasing thermal efficiency.
No matter what form of plant or what type of fuel is used, it must operate reliably and efficiently to satisfy customer and operator requirements. At a time when an increasing number of state-owned utilities are entering the private sector, shareholder interests become of more than academic interest. Profits and commercial considerations are forcing former large, unwieldy monolithic organizations to split into efficient individual profit centers where costs and cash-flow are king. Any measures which can be taken at a modern, low emission gas turbine power plant to increase efficiency, availability and reliability and to reduce fuel-spend will literally pay dividends, as well as help conserve fuel and energy resources.
Real time monitoring
The latest generation of computer-based artificial intelligence systems now provide real-time condition monitoring of turbomachinery, supplying vital data for all those who operate, manage and maintain gas turbine power plants. The four principal processes undertaken in state-of-the-art, on-line condition monitoring equipment such as the DATM4 from Boyce Engineering International are monitoring, analysis, diagnosis and prognosis of the mechanical and aerothermal characteristics. By this means it is possible to reduce losses, improve operational efficiency and accurately analyze vibration and aerothermal parameters. These in turn enable incipient fault conditions to be pinpointed with extreme accuracy, allowing operators to make informed decisions and take remedial actions before a fault escalates into an emergency.
The more effective monitoring systems also have statistical packages built-in that automatically project a future date when remedial action will be required. This enables plant maintenance operations to be accurately forecast, predicting when shut-down will become necessary. Such systems can even display the remaining life of individual components within turbomachinery. It will, for instance, show the actual operating hours and remaining life in the hot gas path of four combustion turbines. This is based on clock-hours, temperature history, metallurgy and the total number of start-ups and trips. Armed with this information, plant management can efficiently schedule replacement or repairs to critical components, reducing stock-holding of spares, increasing plant availability and minimizing costs.
With generating plant bid-in times to the UK National Grid`s `pool` scheduled to change from the present frequency of 30 minutes to one hour, it will become even more important to predict and maintain high plant availability. The ability to immediately control operating losses within a turbine system utilizing a real-time performance monitoring system provides instant savings from improved efficiency and reduced fuel-burn. A one percent improvement in heat-rate on a 500-MW plant can represent an annual energy saving of more than (US)$1.5 million, thus helping to keep the world`s wheels turning just that bit longer.
Gas turbines are becomming the prime mover of choice, and large multi-unit plants like the one shown here may soon be the rule rather than the exception.
Controlling coal-fired plant emissions is critical to the future of this generating source.
Nuclear fission is clean, but political obsticals remain its biggest foe.
Meherwan P. Boyce, P.E., is chairman of the board and chief executive officer of Boyce Engineering International Inc. The company, founded in 1977, specializes in turbomachinery control and condition monitoring and is a pioneer in the development of completely integrated systems.