Wave power can be used for electricity generation, as well as water for desalination and pumping of water into reservoirs. Wave power is distinct from the diurnal flux of tidal power and the steady flow of ocean currents.
Waves are generated by wind passing over the surface of the sea. As long as the waves propagate slower than the wind speed just above the waves, there is an energy transfer from the wind to the waves. Both air pressure differences between the upwind
• The learning curves are based on price, rather than cost data.
• The factors that will drive the future cost reductions may be different from those of the past.
• The cost of bringing energy-efficient appliances to the market should take into account not only the bottom-up engineering models (which tend to overestimate
[2] Using a I0% discount rate. The actual global range may be wider. Wind and solar include grid connection cost.
[3] Costs in 2005 or 2006.
[4] Wide range. Costs of delivered biomass feedstock vary by country and region due to factors such as variations in terrain, labour costs and crop yields.
[5] Typical costs 20-40 US cents/kWh for low latitudes with high solar insolation of 2500 kWh/m2/ year. 30-50 cents/kWh (typical of southern Europe) and 50-80 cents for higher latitudes.
[6] Costs for parabolic trough plants. Costs decrease as plant size increases.
[7] No infrastructure required which allows for lower costs per unit installed.
(Source: “Deploying Renewables: Principles of effective Policies”, 2008, p. 80-83)
Potentially, there is a wide range of ways to reduce emissions of greenhouse gases. In the case of CO2, reductions can be achieved by: reducing the demand for energy; altering the way in which it is used and changing the methods of production and delivering energy. Demand for energy can be influenced by a number of means including fiscal measures and changes in human behaviour. However, in the technical area, there are a number of distinct types of options for reducing emissions, as illustrated in Fig. 9.1 which are:
• Improving energy efficiency,
• Switching to low carbon fuels,
• Switching to no-carbon fuels, and
[9] Flue gas clean-up.
In most cases, the first two options are cost-effective and will deliver useful reductions, but on their own, are unlikely to be enough. Greater reductions could be attained by switching to no-carbon fuels such as renewable and nuclear power; however, the world is presently heavily dependent on the exploitation and use of fossil fuels. For this reason, it is important that there should also be technology options that will allow for the continued use of fossil fuels. However, continued use of fossil fuels needs to be undertaken without substantial emissions of CO2. In this respect, one route forward would be the development and deployment of technologies for the capture and storage of CO2 produced by the combustion of fossil fuels.
[10] fertile conversion of thorium is more efficient in a thermal reactor.
• fewer non-fissile neutron absorptions and improved neutron economy.
• can be the basis for a thermal breeder reactor.
Renewable energy technologies are essential contributors to sustainable energy as they contribute to world energy security by reducing dependence on fossil fuel resources, and providing opportunities for mitigating greenhouse gases. The three generations of renewable technologies, reaching back more than 100 years are:
• First-generation technologies include hydropower, biomass combustion, and geothermal power and heat.
• Second-generation technologies include solar heating and cooling, wind power, modern forms of bioenergy, and solar photovoltaics.
[12] Third-generation technologies are still under development and include advanced biomass gasification, enhanced geothermal system, and marine energy.
First – and second-generation technologies have entered the markets. Third – generation technologies are not yet widely demonstrated or commercialized. They may have potential comparable to other renewable energy technologies (IEA, 2007).
Bioenergy or biofuel technologies being developed today, notably cellulosic ethanol biorefineries, could allow biofuels to play a much bigger role in the future. Crop residues, such as corn stalks, wheat straw and rice straw and wood waste and municipal solid waste are potential sources of cellulosic biomass. Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be sustainably produced in many regions of the United States.
Biomass gasification is potentially more efficient than direct combustion of the original fuel. Syngas can be burned directly in internal combustion engines, used to
[13] Virgin wood: from forestry, arboriculture activities or from wood processing;
• Energy crops: high yield crops grown specifically for energy applications;
[14] Tidal stream systems make use of the kinetic energy of moving water to power turbines.
• Barrages make use of the potential energy in the difference in height or head between high and low tides.
(NREL), funded by the Office of Fuels Development, a division of the US Department of Energy (Biopact, 2007).
