Green Energy Technology, Economics and Policy Part 5 pptx

Next generation green technologies 119 Ocean currents represent a significant, currently untapped, reservoir of energy. The total worldwide power in ocean currents has been estimated to be about 5,000 GW, with power densities of up to 15 kW/m 2 . In large areas with powerful currents, it would be possible to install water turbines in groups or clusters to create a marine current facility. Turbine spacing would be determined based on wake interactions and maintenance needs. A 30 MW demonstra- tion array of vertical turbines in a tidal fence is being investigated in the Philippines (WEC, 2001). However a number of potential problems need to be addressed, including avoidance of drag from cavitations (air bubble formation that creates turbulence and decreases the efficiency of current-energy harvest), prevention of marine growth build up, corrosion control, and overall system reliability. Because the logistics of maintenance are likely to be complex and the costs potentially high, system reliability is of high importance. Ocean currents flow relatively steadily throughout the year and in some cases the flow is considerable. An example is the Straits of Florida where the Gulf Stream flows out of the Caribbean Sea and into the North Atlantic on its way to northern Europe. The speed of the current is around 7.4 km/h at the surface, but it decreases with depth. There is a potential extractable power of 1 kW/m 2 near the surface. A 300 kW full-scale plant installed by Marine Current Turbines (MCT) has been operating at Lynmouth, Devon (UK) since May 2003. MCT has also been planning deep sea marine current systems, which could be constructed in large farms and thus use economies of scale both in construction and maintenance and in the infrastructure for bringing the electricity to shore. Another approach which has identified the potential of the Gulf Stream is the Gorlov helical turbine, a vertical-axis turbine which is being currently prototyped in South Korea. No currently operating commercial turbines are connected to an electric-power transmission or distribution grid; however, a number of configurations are being tested on a small scale. Because no commercial turbines are currently in operation, it is diffi- cult to assess the costs of current-generated energy and its competitiveness with other energy sources. Initial studies suggest that for economic exploitation, velocities of at least 2 m/s would be required, although it is possible to generate energy from velocities as low as 1 m/s. Major costs of these systems would be the cables to transport the electricity to the onshore grid. There are many similarities and common problems with tidal-current energy extraction. Potential environmental impacts of ocean current energy extraction include: • Impacts on marine ecology and conflicts with other potential uses of the same area of the ocean; • Resource requirements associated with the construction and operation; and • Protection of species, particularly fish and marine mammals. The slow blade velocities should allow water and fish to flow freely and safely through the structure. Protective fences and sonar-activated brakes could prevent larger marine mammals from harm. In the siting of the turbines, consideration of impacts on shipping routes, and present as well as anticipated uses such as commercial and recreational fishing and recreational diving, would be required. 120 Green Energy Technology, Economics and Policy The need to introduce possible mitigating factors, such as the establishment of fishery exclusion zones has to be considered. Concerns have been raised about risks from slowing the current flow by extracting energy. Local effects, such as temperature and salinity changes in estuaries caused by changes in the mixing of salt and fresh waters, would need to be considered for their potential impact on estuary ecosystems (Charlier and Justus 1993). Damage to seabed flora is also potentially dangerous and designs are being explored which are anchored to the seabed but operate at a distance, rather than having towers built on the bed. Since there are at present no firm plans for deployment of these devices, it is difficult to evaluate whether this will be a serious problem. 11.3.2 Ocean thermal energy Ocean thermal energy conversion (OTEC) uses the temperature difference that exists between deep and shallow waters to run a heat engine. The greatest efficiency and power is produced with the largest temperature difference. This temperature difference generally increases near the equator. The ocean surface contains a vast amount of solar energy, which can potentially be harnessed for human use. If this extraction could be made cost effective on a large scale, it could be a source of renewable energy (Avery and Wu, 1994). The technical challenge of OTEC is to generate significant amounts of power effi- ciently from this very small temperature ratio. Changes in efficiency of heat exchange in modern designs allow performance approaching the theoretical maximum efficiency. The earth’s oceans are continually heated by the sun and cover nearly 70% of the surface. This makes them the world’s largest solar energy collector and energy storage system. On an average day, 60 million km 2 of tropical seas absorb an amount of solar radiation equal in heat content to about 250 billion barrels of oil. The total energy available is one or two orders of magnitude higher than other ocean energy options such as wave power. But the small magnitude of the temperature difference makes energy extraction comparatively difficult and expensive, due to low thermal efficiency. Earlier OTEC systems had an overall efficiency of 1 to 3%. The theoretical maximum efficiency lies between 6 and 7%. Current designs under review will operate closer to the theoretical maximum effi- ciency. The energy carrier, seawater, is free, though it has an access cost associated with the pumping materials and pump energy costs. An OTEC plant can be configured to operate continuously to supply base load power. As long as the temperature between the warm surface water and the cold deep water differs by about 20 ◦ C, an OTEC system can produce a significant amount of power. The oceans are thus a vast renewable resource, with the potential to help us produce billions of watts of electric power. The cold, deep seawater used in the OTEC process is also rich in nutrients, and it can be used to culture both marine organisms and plant life near the shore or on land. This cold seawater is an integral part of the three types of OTEC systems: closed- cycle, open-cycle, and hybrid. To operate, the cold seawater must be brought to the surface. This can be accomplished through direct pumping. A second method is to desalinate the seawater near the sea floor; this lowers its density, which will cause it to rise up through a pipe to the surface. Next generation green technologies 121 Working fluid-Ammonia Pump Water in 15’C Water in 5’C Water out 10’C OTEC Condenser Turbine Vaporizer Ocean surface Depth - 1000 Metre Figure 11.3.1 Scheme of closed cycle OTEC plant Closed-cycle systems use fluid with a low boiling point, such as ammonia, to rotate a turbine to generate electricity. Warm surface seawater is pumped through a heat exchanger where the low-boiling-point fluid is vaporized. The expanding vapor turns the turbo-generator. Then, cold, deep seawater—pumped through a second heat exchanger—condenses the vapor back into a liquid, which is then recycled through the system (Fig 11.3.1). In 1979 the Natural Energy Laboratory (NEL) and several private-sector partners developed the mini OTEC experiment, which achieved the first successful at-sea pro- duction of net electrical power (Trimble and Owens, 1980). The mini OTEC vessel was moored 2.4 km off the Hawaiian coast and produced enough net electricity to illuminate the ship’s light bulbs, and run its computers and televisions. NEL in 1999 tested a 250 kW pilot closed-cycle plant. Open-cycle OTEC uses the tropical oceans’ warm surface water to make electricity. When warm seawater is placed in a low-pressure container, it boils. The expanding steam drives a low-pressure turbine attached to an electrical generator. The steam, which has left its salt and contaminants behind in the low-pressure container, is pure fresh water. It is condensed back into a liquid by exposure to cold temperatures from deep-ocean water. This method has the advantage of producing desalinized fresh water, suitable for drinking water or irrigation. In 1984 National Renewable Energy Laboratory developed a vertical-spout evapo- rator to convert warm seawater into low-pressure steam for open-cycle plants. Energy conversion efficiency of 97% was achieved for the seawater-to-steam conversion pro- cess. The overall efficiency of an OTEC system was few per cent. In 1993, an open-cycle OTEC plant at Keahole Point, Hawaii, produced 50 000 watts of electricity during a net power-producing experiment. Hybrid cycle combines the features of both the closed-cycle and open-cycle sys- tems. In a hybrid OTEC system, warm seawater enters a vacuum chamber where it is flash-evaporated into steam, similar to the open-cycle evaporation process. The 122 Green Energy Technology, Economics and Policy steam vaporizes the ammonia working fluid of a closed-cycle loop on the other side of an ammonia vaporizer. The vaporized fluid then drives a turbine to produce electri- city. The steam condenses within the heat exchanger and provides desalinated water. The electricity produced by the system can be delivered to a utility grid or used to manufacture methanol, hydrogen, refined metals, ammonia, and similar products. OCEES International, Inc. is working with the U.S. Navy on a design for a proposed 13 MW OTEC plant in Diego Garcia, which would replace the current power plant running diesel generators. The OTEC plant would also provide 1.25 MGD of potable water to the base. Another U.S. company has proposed building a 10 MW OTEC plant in Guam. Lockheed Martin’s Alternative Energy Development team is currently in the final design phase of a 10 MW closed cycle OTEC pilot system which will become oper- ational in Hawaii during 2012–2013. This system is being designed to expand to 100 MW commercial systems in the near future. OTEC has important benefits other than power production. The 5 ◦ C cold seawater made available by an OTEC system creates an opportunity to provide large amounts of cooling to operations that are related to or close to the plant. The cold seawater from an OTEC plant can be used in chilled-water coils to provide air-conditioning for buildings. OTEC technology also supports chilled-soil agriculture. When cold seawater flows through underground pipes, it chills the surrounding soil. The temperature difference between plant roots in the cool soil and plant leaves in the warm air allows many plants that evolved in temperate climates to be grown in the subtropics. Aquaculture can be a byproduct of OTEC. Deep ocean water contains high concentrations of essential nutrients that are depleted in surface waters due to bio- logical consumption. This “artificial upwelling’’ mimics the natural upwelling that is responsible for fertilizing and supporting marine ecosystems. Desalinated water can be produced in open- or hybrid-cycle plants using surface condensers. In a surface condenser, the spent steam is condensed by indirect contact with the cold seawater. Studies indicate that a 2 MWe net plant could produce about 4 300 m 3 of desalinated water each day. Hydrogen can be produced via electrolysis using electricity generated by the OTEC process. The steam generated can be used as a relatively pure medium for electrolysis with electrolyte compounds added to improve the overall efficiency. It will be possible to extract many elements contained in salts and other forms and dissolved in sea water. In the past, most economic analyses concluded that mining the ocean for trace elements dissolved in solution would be unprofitable, in part because much energy is required to pump the large volume of water needed. The Japanese recently began investigating the concept of combining the extraction of uranium dissolved in seawater with wave-energy technology. The economics of energy production today have delayed the financing of a perma- nent, continuously operating OTEC plant. OTEC is very promising as an alternative energy resource for tropical island communities that rely heavily on imported fuel. OTEC could provide the islands with much-needed power, as well as desalinated water and a variety of aquaculture products. Because OTEC systems have not yet been widely deployed, estimates of their costs are uncertain. One study estimates power generation costs as low as US $0.07 per kilowatt-hour, compared with $0.05–$0.07 for subsidized wind systems. Next generation green technologies 123 Future research needed to accelerate the development of OTEC systems include: • Characterization of cold-water pipe technology; • Advanced heat exchanger systems to improve heat transfer performance and decrease costs; and • Innovative turbine concepts for the large machines required for open-cycle systems 11.3.3 Salinity gradient power Salinity gradient power is the energy retrieved from the difference in the salt concen- tration between seawater and river water. Two practical methods for this are reverse electro-dialysis (RED) and pressure retarded osmosis (PRO). Both processes rely on osmosis with ion specific membranes. Osmotic pressure is the chemical potential of concentrated and dilute solutions of salt. All energy that is proposed to use salinity gradient technology relies on the evapo- ration to separate water from salt. Solutions with higher concentrations of salt have higher osmotic pressure. The technologies have been tested in laboratory conditions. They are being deve- loped on commercial scales in the Netherlands (RED) and Norway (PRO). Though the cost of the membrane is quite high, a new cheap membrane, based on an electrically modified polyethylene plastic, has been proposed. The world’s first osmotic plant with capacity of 4 kW was established in 2009 in Tofte, Norway. Other methods have been proposed and are currently under development include that based on electric double layer capacitor and vapor pressure difference technolo- gies. (Olsson et al, 1979; Brogioli, 2009). The osmotic pressure difference between fresh water and seawater is equivalent to 240 m of hydraulic head. Theoretically a stream flowing at 1 m 3 /s could produce 1 MW of electricity. The worldwide fresh to seawater salinity resource is estimated at 2.6 TW. This is comparable to the ocean thermal gradient estimated at 2.7 TW. Inland highly saline lakes have higher potential. The Dead Sea osmotic pressure differential corresponds to a head of 5 000 m, which is almost twenty times greater than seawater. Salinity gradient power is a specific renewable energy alternative that creates renew- able and sustainable power by using naturally occurring processes. This practice does not contaminate or release CO 2 emissions. Vapor pressure methods will release dis- solved air containing CO 2 at low pressure, but these non-condensable gases can be re-dissolved. In PRO, a membrane separates two solutions, salt water and fresh water. Only water molecules can pass the semi-permeable membrane. As a result of the osmotic pressure difference between both solutions, fresh water will diffuse through the membrane in order to dilute the solution. The pressure drives the turbines and powers the generator that produces the electrical energy (Brauns, 2007). RED is the salinity gradient energy retrieved from the difference in the salt con- centration between seawater and river water. A salt solution and fresh water are let through a stack of alternating cathode and anode exchange membranes. The chemical potential difference between salt and fresh water generates a voltage over each mem- brane and the total potential of the system is the sum of the potential differences over all membranes. 124 Green Energy Technology, Economics and Policy RED process works through difference in ion concentration instead of an electric field, which has implications for the type of membrane needed. As in a fuel cell, the cells are stacked. A module with a capacity of 250 kW has the size of a shipping container. In the Netherlands more than 3 300 m 3 fresh water runs into the sea per second on average. The membrane halves the pressure differences which results in a water column of approximately 135 meters. The energy potential is 4.5 GW. There has generally been a lack of systematic research and development activity in this area. Early technical advances were not considered promising, mainly because they relied on expensive membranes. Membrane technologies have advanced, but to date, they remain the technical barrier to economical energy production. Efforts are underway to address those issues and alternatively develop designs that eliminate mem- brane. Additional challenges include high capital costs and low efficiency (Jones and Rowley, 2003). Principal advantages are no fuel cost, no CO 2 emissions or other significant effluents that may interfere with global climate. Inefficient extraction would be acceptable as long as there is an adequate return on investment. Salts are not consumed in the process. Systems could be non-periodic, unlike wind or wave power. Systems can be designed for large or small-scale plants and could be modular in layout. 11.3.4 Tidal power Tidal power is a form of hydropower that converts the energy of tides into electricity or other useful forms of power. Tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power (Baker, 1991). Tidal power is the only form of energy which derives directly from the relative motions of the earth–moon system, and to a lesser extent from the earth–sun system. The tidal forces produced by the moon and sun, in combination with earth’s rotation, are responsible for the generation of the tides. For producing significant amount of energy out of tidal water turbines, range of tides should be high. Substantial amount of water should be there for pushing water through the turbine. Approximately 4 to 5 r meters range of tides is require producing significant amount electricity. It is significantly important to spot the appropriate place which provides suitable and sustainable conditions to produce tidal energy. There are plenty of places around the globe which provide good conditions for installing water turbines. The Bay of Fundy in Canada and the Bristol Channel between England and Wales are two particularly noteworthy examples. The magnitude of the tide at a location is the result of the changing positions of the moon and sun relative to the earth, the effects of earth rotation, and the local shape of the sea floor and coastlines. The stronger the tide, either in water level height or tidal current velocities, the greater the potential for tidal electricity generation (Hammons, 1993). Tidal power can be classified into three main types: • Tidal stream systems make use of the kinetic energy of moving water to power turbines. Next generation green technologies 125 Table 11.3.2 Operating and proposed tidal power facilities Capacity Country Facility Type (MW) Start year France La Rance Barrage 240 1966 Canada Annapolis Royal Generating Barrage 18 1984 Station, Nova Scotia Canada Race Rocks Tidal Power Tidal stream – 2006 Demonstration Project, Vancouver Island Russia Kislaya Guba on the Barrage 0.5 2006 Barents Sea Russia Penzhinskaya Bay Tidal stream – Proposed Russia Kislaya Guba Tidal stream 12 Under construction Republic of Korea Jindo Uldolmok Tidal Tidal stream 90 2009 Power Plant Republic of Korea Sihwa Lake Tidal Power Tidal stream 254 Under Plant construction Republic of Korea Islands west of Incheo Tidal stream 1 320 Proposed United Kingdom Strangford Lough in Tidal stream 1.2 2008 Northern Ireland. United Kingdom River Severn Barrage 8 000 (max) Proposed 2 000 (av) China Jiangxaia Tidal lagoon 3.2 1980 China Yalu river Tidal lagoon 300 Proposed Philippines San Bernardino Strait Tidal stream 2200 Proposed • Barrages make use of the potential energy in the difference in height or head between high and low tides. • Tidal lagoons can be constructed as self contained structures, not fully across an estuary. Tidal stream generators draw energy from currents in much the same way as wind turbines. Tidal stream turbines may be arrayed in high-velocity areas where natural tidal current flows are concentrated such as the west and east coasts of Canada, the Strait of Gibraltar, the Bosporus, and numerous sites in Southeast Asia and Australia. Some of the operating and proposed facilities are shown in Table 11.3.2. The higher density of water means that a single generator can provide significant power at low tidal flow velocities. Water velocities at about one-tenth of the speed of wind provide the same power for the same size of turbine system. However this limits the application in practice to places where the tide moves at speeds of at least 1m/s even at neap tides (Lecomber, 1979). Tidal stream generators are an immature technology. Only a few commercial scale production facilities are yet routinely supplying power. No standard technology has yet emerged as the clear winner. But large varieties of designs are being experimented with, some very close to large scale deployment. Several prototypes have shown promise, but they have not operated commercially for extended periods to establish performances and rates of return on investments. The 126 Green Energy Technology, Economics and Policy Table 11.3.3 Prototype tidal stream generators Device Principle/Description Examples Axial Turbines Similar to the concept of 1. Kvalsund, south of Hammerfest, traditional windmills; Norway with 300 kW capacity. operating under the sea 2. Seaflow, off the coast of Lynmouth, Devon, England with 300 kW capacity. 3. Verdant Power, in the East River between Queens and Roosevelt Island, NewYork City. 4. SeaGen, in Strangford Lough in Northern Ireland has connected 150 kW into the grid. 5. OpenHydro, being tested at the European Marine Energy Centre (EMEC), in Orkney, Scotland. Vertical and Deployed either vertically 1. Gorlov turbine being commercially horizontal axis or horizontally. piloted on a large scale in S. Korea; starting with cross-flow a 1 MW plant that started in May 2009 and turbines expanding to 90 MW by 2013. 2. Proteus, which uses a barrage of vertical axis cross flow turbines for use mainly in estuaries. 3. Turbine-Generator Unit (TGU) prototype at Cobscook Bay and Western Passage tidal sites near Eastport, Maine. 4. Trials in the Strait of Messina, Italy, started in 2001 of the Kobold concept. Oscillating No rotating component. 1. Stingray, tested off the Scottish devices Aerofoil sections which are coast with 150 kW capacity. pushed sideways by the flow. 2. Pulse Tidal, in the Humber estuary. Venturi effect Uses a shroud to increase the 1. Tidal Energy, commercial trials in the flow rate through the turbine. Gold Coast, Queensland (2002). Mounted horizontally or 2. Hydro Venturi, is to be tested in San Francisco vertically. Bay. devices could be classified into four, although a number of other approaches are also being tried (Table 11.3.3). The cost associated for developing tidal power station can vary depending on the capacity. Project Severn Estuary in UK cost US $15 billion which produces about 8000 MW. The proposed 2200 MW tidal power station project in San Berandino cost about US $3 billion. 11.3.5 Wave power 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 Next generation green technologies 127 20 30 100 70 50 40 40 20 10 20 40 50 100 70 50 40 30 30 20 15 15 15 10 20 30 50 40 20 15 15 40 40 60 70 50 20 15 40 40 20 100 100 50 30 40 50 60 100 Figure 11.3.2 Approximate global distribution of wave power levels (kW/m of wave fuel) and the lee side of a wave crest, as well as friction on the water surface by the wind causes the growth of the waves (Cruz, 2008). Wave height is determined by wind speed, the duration of time the wind has been blowing, fetch or the distance over which the wind blows and by the depth and topo- graphy of the seafloor. The depth and topography of the sea floor can focus or disperse the energy of the waves. A given wind speed has a matching practical limit over which time or distance will not produce larger waves. In general, larger waves are more powerful but wave power is also determined by wave speed, wavelength, and water density. When an object bobs up and down on a ripple in a pond, it experiences an elliptical trajectory. This oscillatory motion is highest at the surface and diminishes exponentially with depth. The waves propagate on the ocean surface, and the wave energy is also transported horizontally with the group velocity. The group velocity of a wave is the velocity with which the overall shape of the wave’s amplitudes propagates through space. The mean transport rate of the wave energy through a vertical plane of unit width, parallel to a wave crest, is called the wave energy flux or wave power (McCormick, 2007). Wave energy can be considered as a concentrated form of solar energy. Winds, generated by the differential heating of the earth, pass over open bodies of water, transferring some of their energy to form waves. The amount of energy transferred, and hence the size of the resulting waves, depends on the wind speed, the length of time for which the wind blows and the distance over which it blows. The useful worldwide resource has been estimated at >2 TW (WEC, 1993). The approximate global distribution of wave power levels is given in Fig. 11.3.2. Wave power generation is not currently a widely employed commercial technology although there have been attempts at using it since at least 1890. The world’s first commercial wave farm is based in Portugal, at the Aguçadoura Wave Park, which consists of three 750 kilowatt Pelamis devices. 128 Green Energy Technology, Economics and Policy There is a large amount of ongoing work on wave energy schemes. The devices could be deployed on the shoreline, near the shore and offshore: Shoreline Devices: These devices are fixed to or embedded in the shoreline itself. It has the advantage of easier maintenance and/or installation. These would not require deep water moorings or long lengths of underwater electrical cable. However, they would experience a much less powerful wave regime. This could be partially com- pensated by natural energy concentration. The deployment of such schemes could be limited by requirements for shoreline geology, tidal range and preservation of coastal scenery. One major class of shoreline device is the oscillating water column (OWC). It con- sists of a partially submerged, hollow structure, which is open to the sea below the water line. This structure encloses a column of air on top of a column of water. As waves impinge upon the device they cause the water column to rise and fall, which alternatively compresses and depressurizes the air column. If this trapped air is allowed to flow to and from the atmosphere via a turbine, energy can be extracted from the system and used to generate electricity (Falnes, 2002). Nearshore Devices: The main prototype device for moderate water depths (i.e. <20 m) is the OSPREY developed by Wavegen. This is a 2 MW OWC, with pro- vision for inclusion of a 1.5 MW wind turbine. Since there could be environmental objections to large farms of wind or wave energy devices close to the shore, this system aims to maximize the amount of energy produced from a given amount of near shore area (Thorpe, 1999). Offshore Devices: This class of device exploits the more powerful wave regimes available in deep water (>40 m depth) before energy dissipation mechanisms have had a significant effect. In order to extract the maximum amount of energy from the waves, the devices need to be at or near the surface and so they usually require flexible moorings and electrical transmission cables. More recent designs for offshore devices have also concentrated on small, modular devices. The McCabe wave pump, OPT wave energy converter, Pelamis and Archimedes wave swing are some of the examples. Some examples of wave power systems are given in Table 11.3.4. The major technical challenges in deploying wave power devices are: • The device needs to capture a reasonable fraction of the wave energy in irregular waves, in a wide range of sea states. • There is an extremely large fluctuation of power in the waves. The peak absorption capacity needs to be much (more than 10 times) larger than the mean power. For wave power the ratio is typically 4. • The device has to efficiently convert wave motion into electricity. Wave power is available at low speed and high force, and the motion of forces is not in a single direction. Most readily-available electric generators operate at higher speeds, and most readily-available turbines require a constant, steady flow. • The device has to be able to survive storm damage and saltwater corrosion. At present, the main stumbling block to deployment of wave energy devices is funding. The capital costs are the problem, as it is hard to get companies to invest in technologies that have not yet been completely proved. The position is similar to other forms of renewable energy sources. 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Conference on Greenhouse Gas Technologies, Vol I; peer reviewed Papers and Plenary Presentations, pp 58 3 59 2 Eds E.S Rubins, D.W Keith and C.F Gilboy, Pergamon, 20 05 Brauns, E (2008) Toward a worldwide sustainable and simultaneous large-scale production of renewable energy and potable water through salinity gradient power by combining reversed electrodialysis and solar power, Environmental Process and Technology,. .. industrial energy intensity defined as energy use per unit of industrial output During the period, 1971 and 20 05, energy use and CO2 emissions increased by 65% , i.e at the annual growth rate of about 1 .5% But the growth rates vary widely among different sectors – energy and feedstock use has doubled in the case of chemicals and petrochemicals sub-sector, whereas the growth was flat in the case of iron and. .. R.H., Regis, M and Leal, L.V (2001) ?A review of biomass integrated-gasifier/gas turbine combined cycle technology and its analysis for Cuba, Energy for Sustainable Development 5 (1) Lecomber, R (1979) The evaluation of tidal power projects, Tidal Power and Estuary Management Dorchester: Henry Ling Ltd 146 Green Energy Technology, Economics and Policy Lindeberg, E., J.-F Vuillaume and A Ghaderi (2009)... renewable energy from a salinity difference using a capacitor, Phys Rev Lett., Vol 103, pp 058 501.1– 058 501.4 CEC (2006) California Energy Commission http:/ /energy. ca.gov/geothermal/index.html Charlier, R.H and Justus, J.R (1993) Ocean Energies: Environmental, Economic and Technological Aspects of Alternative Power Sources Amsterdam: Elsevier Science Publishers Cohen, B.L (1990) The Nuclear Energy Option... Wave Energy – Current Status and Future Prospects Berlin: Springer Curtis, D and Langley, B (2004) Going With the Flow: Small Scale Water Power Powys: Centre for Alternative Technology Publications Algal biofuels 1 45 DOE (1993) Nuclear Physics and Reactor Theory DOE Fundamentals Handbook Volume 1 and 2 Washington, D.C.: Department of Energy DOE (2002) A Technology Roadmap for Generation IV Nuclear Energy. .. and conduction of heat from the Earth’s mantle and core, and Heat generated by the decay of radioactive elements in the crust, particularly isotopes of uranium, thorium, and potassium Local and regional geologic and tectonic phenomena play a major role in determining the location (depth and position) and quality (fluid chemistry and temperature) of a particular resource For example, regions of higher... 2% of the world’s 152 Green Energy Technology, Economics and Policy Industrial emissions can be drastically reduced by the application of CCS in the production of chemicals, iron and steel, cement, paper and pulp This option is still in the process of development Technological improvements to bring about savings in CO2 emissions vary from one industry to another For instance, the energy savings potential... of $200–$ 350 million Center for Geothermal Energy Excellence at the University of Queensland, has been awarded $18.3 million (AUS) for EGS research, a large portion of which will be used to develop CO2 EGS technologies Research conducted at Los Alamos National Laboratories and Lawrence Berkeley National Laboratories examined the use of supercritical 136 Green Energy Technology, Economics and Policy CO2 . 127 20 30 100 70 50 40 40 20 10 20 40 50 100 70 50 40 30 30 20 15 15 15 10 20 30 50 40 20 15 15 40 40 60 70 50 20 15 40 40 20 100 100 50 30 40 50 60 100 Figure 11.3.2 Approximate global distribution of wave power levels (kW/m of wave fuel) and the. as anticipated uses such as commercial and recreational fishing and recreational diving, would be required. 120 Green Energy Technology, Economics and Policy The need to introduce possible mitigating. Wave Park, which consists of three 750 kilowatt Pelamis devices. 128 Green Energy Technology, Economics and Policy There is a large amount of ongoing work on wave energy schemes. The devices could be