Innovation in Global Power - Parsons Brinckerhoff

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Renewables – The Risks, Concerns and Potential The exhaust gas emitted from a gas turbine in combined cycle mode is the same as from one in open cycle mode; however, the quantity of emissions for a notional level of output (CO2 per kWh) is greatly reduced owing to the higher power output of CCGT plant. Coal integrated gasification combined cycle (IGCC). Integrated gasification plants offer reduced environmental emissions, but at an increased capital cost when compared to more conventional combustion technologies. This technology allows the use of a wide range of fuel sources that would not typically be used in conventional thermal power. It is also one of the technologies associated with carbon capture and sequestration. 2 The synthetic gas that is derived from the fuel gasification can be cleaned prior to combustion, giving emissions comparable to those of natural gas plant and thermal efficiencies of up to 43 percent. Further, the technology enables the carbon fraction in the fuel to be removed prior to combustion, when there is a need for carbon capture and sequestration. Appropriate treatment of the by-product streams from the gasification process and ensuring a safe design means that the capital cost of such plants is high. Further, the operational experience of these plants is also relatively limited. Nuclear. In the UK, nuclear power plants currently account for just under 20 percent of total electricity demand, with most of this power coming from advanced gas-cooled reactors.The older Magnox reactors will have been shut down by 2010. Only one reactor, the pressurised water reactor at Sizewell B is planned to be in operation beyond 2024. The UK government’s Energy Review in 2003 declared that new nuclear plants would not be considered, although the option would be kept open. The main reason for this view was that the abundance of low-cost fossil fuel generation (predominantly gas) had led to low-cost base-load electricity prices. This was the situation in all countries that had access to low-cost fossil fuels. This backdrop has changed significantly with much higher oil and gas prices, with oil seemingly breaking high price records weekly, and the requirements in Kyoto signatory countries to reduce carbon emissions. Whilst these factors have changed, the issues of long-term solutions for the used nuclear fuel and the irradiated plant and equipment from the reactor remains, however, and continue to present significant political, social and financial challenges. A cost estimate of £1.5bn at the end of the operational life has been included in our evaluation to account for decommissioning. It should be noted that nuclear power plant costs 2 Please read “The Effect of Carbon Capture and Storage and Carbon Pricing on the Competitiveness of Gas Turbine Power Plants,” a preceding article by Dominic Cook, to learn about how carbon capture and storage works and what are its prospects in the electricity generation market. http://www.pbworld.com/news_events/publications/network/ are likely to be the most strongly contested values of all the power generation technologies and, therefore, the values used in our evaluation were considered to be conservative. Onshore wind. Development of onshore wind turbines has moved to a point where the plant is considered to be almost able to compete on a level playing field in terms of price with other more conventional technologies. Its viability remains highly dependent on the wind resource in each location, however, and this variability in the plant output continues to incentivise developments in electricity storage technologies. The installed cost of wind power projects has seen a rise over recent years due largely to the increase in wind turbine prices resulting from increases in energy costs and raw material costs (steel, copper and blade materials). Turbine manufacturers have also used the upturn in world demand to increase their margins on the back of a scarcity of turbine manufacturing capacity—the economics of supply and demand. Offshore wind. The trend continues towards larger turbines with larger rotor diameters. It is expected that these advancements will result in reductions in specific costs in the longer term, although the present trend is upwards owing to continued learning and competitive pressures from oil and gas industries for the vessels and personnel necessary for installation in a marine environment. Economies of scale are likely to be realised as the size of wind farm projects increases. Wave and Tidal. Wave and marine generation broadly encompasses five types of technology considered to be relevant to the UK: • Tidal barrages. Seawater flows through constructed barrages is used to power turbine generators. 3 • Offshore tidal current turbine. Energy in the currents created by tidal streams is used to generate electricity. • “Pelamis” sea snake. When floating on the sea, hinged joints between the snake’s semi-submerged articulated cylindrical sections move with the waves, powering hydraulic motors that then generate electricity. • Oscillating hydroplane. Energy in the currents created by tidal streams is used to generate electricity using the principle of an oscillating hydroplane. • Oscillating water column device (OWC). The OWC device comprises a partly submerged concrete or steel structure, open below the water surface. Air is trapped inside above the water-free surface. The oscillation of the internal free surface produced by the incident waves makes air flow through a turbine that drives an electric generator. Significantly, the present status of development of wave and tidal generation devices is summarised by the Carbon Trust as follows: “Overall, devices are at early stages compared to 3 Peter Kydd discusses tidal barrages in a following article, “Project Brief: Tidal Power.” PB Network #68 / August 2008 46
Renewables – The Risks, Concerns and Potential http://www.pbworld.com/news_events/publications/network/ other renewables and conventional plant, and crucially, optimal designs have yet to be converged upon. A few large-scale prototypes have been built and tested in real sea conditions, but no commercial wave and tidal stream projects have yet been completed.” Biomass BFB technology. Bubbling fluidised bed (BFB) is a well-proven technology suitable for small (less than 100 MWe) biomass power plants. (Biomass is plant or animal matter or biodegradable waste used as fuel.) The BFB provides thermal inertia that makes it suitable for combustion of fuels of high and variable moisture content and fuels that are difficult to pulverise effectively, such as woody materials. Base Comparison The base assumption is that the cost of carbon is based on the European Union Emission Trading Scheme and is based on a £25/tonne long-term cost. The quantity of allowances provided to the electricity generators is assumed to be phased out by 2018, 4 when they will need to purchase carbon certificates for their emissions. Comparison of the technologies with each other and in relation to the present expectation of market forward electricity pricing (Figure 1) reveals that there are two distinct groups of technologies: • Those that are viable (or marginally so) with the present market expectations • Those that will continue to require support from external mechanisms to continue their development towards commercial reality. Carbon costs are beginning to form a significant portion of the overall cost of generation for fossil fired power plants. As the allowances provided decrease and the carbon price increases, this effect will be more pronounced, with the gap between the fossil fired and renewable generation sources being reduced. This reduction alone is not sufficient to give the commercial incentives to build renewable plant, and there will be a continued need for support mechanisms— be it through feed-in tariffs, renewable obligation mechanisms or other such support schemes. Summary • Renewable generation will continue to need support mechanisms to ensure that the best use of the resources is made and that the “best value” is returned in terms of carbon reduction and energy delivered. • Nuclear plant continues to have uncertainty surrounding decommissioning costs and the need for a long-term solution for spent fuel from nuclear plant. The expectations are that any new build is likely to replace existing nuclear capacity only and, therefore, would not result in a net gain in carbon savings. • Conventional fossil-fired generation plants are likely to continue to “feel the pressure” through uncertainty surrounding future carbon allocation levels, carbon pricing, fuel pricing and security of supply. Figure 1: Comparative Costs of Generation. Dominic Cook has 20+ years of utility and consultancy experience in the power industry. He has been involved in regulatory audits and the development of power generation plant, and in providing advice to financial institutions. His publications included “Powering the Nation” in June 2006 and he is presently involved with the UK government on the carbon capture competition. 4 Phasing out assumed to be 90 percent to 2010; 50 percent between 2013 to 2017 and 0 percent from 2018 onwards. 5 Standby energy is the cost to provide replacement power when a plant suffers a forced outage. 47 PB Network #68 / August 2008
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Innovation in Global Power - Parsons Brinckerhoff

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