Advanced Energy Supply Technologies

Abstract

Fossil energy technologies. Sustainability principles indicate that fossil energy technologies should evolve towards the long-term goal of near-zero air pollutant and greenhouse gas emissions-without complicated end-of-

pipe control technologies. Near-term technologies and strategies should support this long-term goal. The technological revolution under way in power generation- where advanced systems are replacing steam turbine tech-nologies- supports this long-term goal. Natural-gas-fired combined cycles offering low costs, high efficiency, and low environmental impacts are being chosen wherever natural gas is readily available. Cogeneration is more cost-effective and can play a much larger role in the energy economy if based on gas turbines and combined cycles rather than on steam turbines. Reciprocating engines and emerging microturbine and fuel cell technologies are strong candidates for cogeneration at smaller scales. Coal gasification by partial oxidation with oxygen
to make syngas (mainly carbon monoxide, CO, and hydrogen, H2 ) makes it possible to provide electricity though integrated gasifier combined cycle plants with air pollutant emissions nearly as low as those plants using natural gas combined cycles. Today power from integrated gasifier combined cycle cogeneration plants can often compete with power from coal steam-electric plants in either cogeneration or power-only configurations.

Although synthetic liquid fuels made in single-product facilities are not competitive, superclean syngas-derived synthetic fuels that are produced in polygeneration facilities making several products simultaneously may soon be. Syngas can be produced from natural gas by steam reforming or other means or from coal by gasification with oxygen. Expanding markets for clean synthetic fuels are likely to result from toughening air pollution regulations. Synthetic fuels produced through polygeneration will be based on natural gas, if it is readily available. In natural-gas-poor, coal-rich regions, polygeneration based on coal gasification is promising.

The barriers to widespread deployment of advanced cogen-eration and polygeneration systems are mainly institutional. Most such systems will produce far more electricity than can be consumed on site, so achieving favourable economics depends on being able to sell coproduct electricity at competitive prices into electric grids. Utility policies have often made doing so difficult, but under the competitive market conditions towards which electric systems are evolving in many regions, cogeneration and polygeneration systems will often fare well.

Near-term pursuit of a syngas-based strategy could pave the way for widespread use of H2 as an energy carrier, because for decades the cheapest way to make H2 will be from fossil-fuel-derived syngas. Syngas-based power and H2 production strategies facilitate the separation and storage of carbon dioxidefrom fossil energy systems, making it possible to obtain useful energy with near-zero emissions of greenhouse gases, without large increases in energy costs. Successful development of fuel cells would, in turn, facilitate introduction of H2 for energy. Fuel cells are getting intense attention, because they offer high efficiency and near-zero air pollutant emissions. Automakers are racing to develop fuel cell cars, with market entry targeted for 2004-10.

Other advanced technologies not based on syngas offer some benefits relative to conventional technologies. But unlike syngas-based technologies, such options pursued in the near term would not offer clear paths to the long-term goal of near-zero emissions without significant increases in costs for energy services.

Nuclear energy technologies. World-wide, nuclear energy accounts for 6 percent of energy and 16 percent of electricity. Although it dominates electricity generation in some countries, its initial promise has not been realised. Most analysts project that nuclear energy''s contribution to global energy will not grow and might decline in the near future. Nuclear power is more costly than originally expected, competition from alternative technologies is increasing, and there has been a loss of public confidence because of concerns relating to safety, radioactive
waste management, and potential nuclear weapons proliferation.

Because nuclear power can provide energy without emitting conventional air pollutants and greenhouse gases, however, it is worth exploring whether advanced technologies might offer lower costs, restore public confidence in the safety of reactors, assure that nuclear programmes are not used for military purposes, and facilitate effective waste management.

In contrast to Chernobyl-type reactors, the light water reactors (LWRs) that dominate nuclear power globally have
had a good safety record, though this has been achieved at considerable cost to minimise the risk of accidents.

The potential linkage between peaceful and military uses of nuclear energy was recognised at the dawn of the nuclear age. Steps taken to create a non-proliferation regime through treaties, controls on nuclear commerce, and safeguards on nuclear materials have kept peaceful and military uses separate. But if there is to be a major expansion of nuclear power, stronger institutional and technological measures will be needed to maintain this separation both for proliferation by nations and theft of weapons-usable materials by subnational groups.
Reactor vendors now offer several evolutionary LWRs with improved safety features and standardised designs, and there is some ongoing work on new reactor concepts.

Limited supplies of low-cost uranium might constrain LWR-based nuclear power development after 2050. Plutonium breeder reactors could address the resource constraint, but keeping peaceful and military uses of nuclear materials separate would be more challenging with breeders. Other possibilities for dealing with the resource constraint are extraction of uranium from seawater and thermonuclear fusion. There are many uncertainties regarding such advanced technologies, and all would take decades to develop.

Radioactive waste by-products of nuclear energy must be isolated so that they can never return to the human environment in harmful concentrations. Many in the technical community are confident that this objective can be met. But in most countries there is no consensus on waste disposal strategies. The current stalemate regarding waste disposal clouds prospects for nuclear expansion.

The book chapter can be downloaded from the link below.