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Ocean thermal energy conversion
Ocean thermal energy conversion (OTEC) uses the temperature difference between cooler deep and warmer shallow or surface ocean waters to run a heat engine and produce useful work, usually in the form of electricity. OTEC is a base load electricity generation system, i.e. 24hrs/day all year long. However, the temperature differential is small and this impacts the economic feasibility of ocean thermal energy for electricity generation.
Systems may be either closed-cycle or open-cycle. Closed-cycle engines use working fluids that are typically thought of as refrigerants such as ammonia or R-134a. These fluids have low boiling points, and are therefore suitable for powering the system's generator to generate electricity. The most commonly used heat cycle for OTEC to date is the Rankine cycle using a low-pressure turbine. Open-cycle engines use vapour from the seawater itself as the working fluid.
OTEC can also supply quantities of cold water as a by-product. This can be used for air conditioning and refrigeration and the nutrient-rich deep ocean water can feed biological technologies. Another by-product is fresh water distilled from the sea.[1]
OTEC theory was first developed in the 1880s and the first bench size demonstration model was constructed in 1926. Currently the world's only operating OTEC plant is in Japan, overseen by Saga University.
- 1 History
- 2 Thermodynamic efficiency
- 3 Cycle types
- 4 Land, shelf and floating sites
- 5 Some proposed projects
- 6 Related activities
- 7 Political concerns
- 8 Cost and economics
- 9 Thermodynamics
- 10 Environmental impact
- 11 Technical difficulties
- 12 Cold air/warm water conversion
- 13 See also
- 14 Footnotes
- 15 References
- 16 Sources
- 17 External links
Attempts to develop and refine OTEC technology started in the 1880s. In 1881, Jacques Arsene d'Arsonval, a French physicist, proposed tapping the thermal energy of the ocean. D'Arsonval's student, Georges Claude, built the first OTEC plant, in Matanzas, Cuba in 1930.[2][3] The system generated 22 kW of electricity with a low-pressure turbine.[4] The plant was later destroyed in a storm.[5]
In 1935, Claude constructed a plant aboard a 10,000-ton cargo vessel moored off the coast of Brazil. Weather and waves destroyed it before it could generate net power.[4] (Net power is the amount of power generated after subtracting power needed to run the system).
In 1956, French scientists designed a 3 MW plant for Abidjan, Côte d'Ivoire. The plant was never completed, because new finds of large amounts of cheap petroleum made it uneconomical.[4]
In 1962, J. Hilbert Anderson and James H. Anderson, Jr. focused on increasing component efficiency. They patented their new "closed cycle" design in 1967.[6] This design improved upon the original closed-cycle Rankine system, and included this in an outline for a plant that would produce power at lower cost than oil or coal. At the time, however, their research garnered little attention since coal and nuclear were considered the future of energy.[7]
Japan is a major contributor to the development of OTEC technology.[8] Beginning in 1970 the Tokyo Electric Power Company successfully built and deployed a 100 kW closed-cycle OTEC plant on the island of Nauru.[8] The plant became operational on 14 October 1981, producing about 120 kW of electricity; 90 kW was used to power the plant and the remaining electricity was used to power a school and other places.[4] This set a world record for power output from an OTEC system where the power was sent to a real (as opposed to an experimental) power grid.[9] 1981 also saw a major development in OTEC technology when Russian engineer, Dr. Alexander Kalina, used a mixture of ammonia and water to produce electricity. This new ammonia-water mixture greatly improved the efficiency of the power cycle.In 1994 Saga University designed and constructed a 4.5 kW plant for the purpose of testing a newly invented Uehara cycle, also named after its inventor Haruo Uehara. This cycle included absorption and extraction processes that allow this system to outperform the Kalina cycle by 1-2%.[10] Currently, the Institute of Ocean Energy, Saga University, is the leader in OTEC power plant research and also focuses on many of the technology's secondary benefits.
The 1970s saw an uptick in OTEC research and development during the post 1973 Arab-Israeli War, which caused oil prices to triple. The U.S. federal government poured $260 million into OTEC research after President Carter signed a law that committed the US to a production goal of 10,000 MW of electricy from OTEC systems by 1999.[11]
In 1974, The U.S. established the Natural Energy Laboratory of Hawaii Authority (NELHA) at Keahole Point on the Kona coast of Hawaii. Hawaii is the best US OTEC location, due to its warm surface water, access to very deep, very cold water, and high electricity costs. The laboratory has become a leading test facility for OTEC technology.[12] In the same year, Lockheed received a grant from the U.S. National Science Foundation to study OTEC. This eventually led to an effort by Lockheed, the US Navy, Makai Ocean Engineering, Dillingham Construction, and other firms to build the world's first and only net-power producing OTEC plant, dubbed "Mini-OTEC"[13] For three months in 1979, a small amount of electricity was generated.
In 1993, a 250kW open-cycle OTEC pilot plant was designed by Dr. Luis Vega and constructed by the National Energy Laboratory of Hawaii (then called NELH) and the Pacific International Center for High Technology Research. The plant operated for six years and produced a record amount of 255kW of energy.[14]
In 2002, India tested a 1 MW floating OTEC pilot plant near Tamil Nadu. The plant was ultimately unsuccessful due to a failure of the deep sea cold water pipe.[14] Its government continues to sponsor research.[15]
In 2006, Makai Ocean Engineering was awarded a contract from the U.S. Office of Naval Research (ONR) to investigate the potential for OTEC to produce nationally-significant quantities of hydrogen in at-sea floating plants located in warm, tropical waters. Realizing the need for larger partners to actually commercialize OTEC, Makai approached Lockheed Martin to renew their previous relationship and determine if the time was ready for OTEC. And so in 2007, Lockheed Martin resumed work in OTEC and became a subcontractor to Makai to support their SBIR, which was followed by other subsequent collaborations[13]
In July 2011, Makai Ocean Engineering completed the design and construction of an OTEC Heat Exchanger Test Facility at the Natural Energy Laboratory of Hawaii. The purpose of the facility is to arrive at an optimal design for OTEC heat exchangers, increasing performance and useful life while reducing cost (heat exchangers being the #1 cost driver for an OTEC plant).[16] And in March 2013, Makai announced an award to install and operate a 100 kilowatt turbine on the OTEC Heat Exchanger Test Facility, and once again connect OTEC power to the grid.[17][18]
Ocean Thermal Energy Corporation (OTE) currently has plans to install two 10 MW OTEC plants in the US Virgin Islands and a 5-10 MW OTEC facility in The Bahamas. OTE has also designed the world's largest SDC plant which was planned for a resorted in The Bahamas, which will use cold deep seawater as a method of air-conditioning.[19] Unfortunately, this project was postponed due to schedule delays.[20]
In March 2013, Saga University with various Japanese industries completed the installation of a new OTEC plant.[21] Currently, this is the only operating OTEC plant in the world.
Thermodynamic efficiency[edit]
A heat engine gives greater efficiency when run with a large temperature difference. In the oceans the temperature difference between surface and deep water is greatest in the tropics, although still a modest 20 to 25 °C. It is therefore in the tropics that OTEC offers the greatest possibilities.[1] OTEC has the potential to offer global amounts of energy that are 10 to 100 times greater than other ocean energy options such as wave power[citation needed]. OTEC plants can operate continuously providing a base load supply for an electrical power generation system.[1]
The main technical challenge of OTEC is to generate significant amounts of power efficiently from small temperature differences. It is still considered an emerging technology. Early OTEC systems were 1 to 3 percent thermally efficient, well below the theoretical maximum 6 and 7 percent for this temperature difference.[22] Modern designs allow performance approaching the theoretical maximum Carnot efficiency and the largest built in 1999 by the USA generated 250 kW.
Cycle types[edit]
Cold seawater is an integral part of each of the three types of OTEC systems: closed-cycle, open-cycle, and hybrid. To operate, the cold seawater must be brought to the surface. The primary approaches are active pumping and desalination. Desalinating seawater near the sea floor lowers its density, which causes it to rise to the surface.[23]
The alternative to costly pipes to bring condensing cold water to the surface is to pump vaporized low boiling point fluid into the depths to be condensed, thus reducing pumping volumes and reducing technical and environmental problems and lowering costs.[citation needed]
Closed-cycle systems use fluid with a low boiling point, such as ammonia (having a boiling point around -33°C at atmospheric pressure), to power a turbine to generate electricity. Warm surface seawater is pumped through a heat exchanger to vaporize the fluid. The expanding vapor turns the turbo-generator. Cold water, pumped through a second heat exchanger, condenses the vapor into a liquid, which is then recycled through the system.
In 1979, the Natural Energy Laboratory and several private-sector partners developed the "mini OTEC" experiment, which achieved the first successful at-sea production of net electrical power from closed-cycle OTEC.[24] The mini OTEC vessel was moored 1.5 miles (2.4 km) off the Hawaiian coast and produced enough net electricity to illuminate the ship's light bulbs and run its computers and television.
Open-cycle OTEC uses warm surface water directly to make electricity. The warm seawater is first pumped into a low-pressure container, which causes it to boil. In some schemes, the expanding steam drives a low-pressure turbine attached to an electrical generator. The steam, which has left its salt and other contaminants in the low-pressure container, is pure fresh water. It is condensed into a liquid by exposure to cold temperatures from deep-ocean water. This method produces desalinized fresh water, suitable for drinking water, irrigation or aquaculture.[25]
In other schemes, the rising steam is used in a gas lift technique of lifting water to significant heights. Depending on the embodiment, such steam lift pump techniques generate power from a hydroelectric turbine either before or after the pump is used.[26]
In 1984, the Solar Energy Research Institute (now the National Renewable Energy Laboratory) developed a vertical-spout evaporator to convert warm seawater into low-pressure steam for open-cycle plants. Conversion efficiencies were as high as 97% for seawater-to-steam conversion (overall efficiency using a vertical-spout evaporator would still only be a few per cent). In May 1993, an open-cycle OTEC plant at Keahole Point, Hawaii, produced 50,000 watts of electricity during a net power-producing experiment.[27] This broke the record of 40 kW set by a Japanese system in 1982.[27]
A hybrid cycle combines the features of the closed- and open-cycle systems. In a hybrid, warm seawater enters a vacuum chamber and is flash-evaporated, similar to the open-cycle evaporation process. The 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 electricity. The steam condenses within the heat exchanger and provides desalinated water (see heat pipe).[citation needed]
Working fluids[edit]
A popular choice of working fluid is ammonia, which has superior transport properties, easy availability, and low cost. Ammonia, however, is toxic and flammable. Fluorinated carbons such as CFCs and HCFCs are not toxic or flammable, but they contribute to ozone layer depletion. Hydrocarbons too are good candidates, but they are highly flammable; in addition, this would create competition for use of them directly as fuels. The power plant size is dependent upon the vapor pressure of the working fluid. With increasing vapor pressure, the size of the turbine and heat exchangers decreases while the wall thickness of the pipe and heat exchangers increase to endure high pressure especially on the evaporator side.
Land, shelf and floating sites[edit]
OTEC has the potential to produce gigawatts of electrical power, and in conjunction with electrolysis, could produce enough hydrogen to completely replace all projected global fossil fuel consumption.[citation needed] Reducing costs remains an unsolved challenge, however. OTEC plants require a long, large diameter intake pipe, which is submerged a kilometer or more into the ocean's depths, to bring cold water to the surface.
Land-based and near-shore facilities offer three main advantages over those located in deep water. Plants constructed on or near land do not require sophisticated mooring, lengthy power cables, or the more extensive maintenance associated with open-ocean environments. They can be installed in sheltered areas so that they are relatively safe from storms and heavy seas. Electricity, desalinated water, and cold, nutrient-rich seawater could be transmitted from near-shore facilities via trestle bridges or causeways. In addition, land-based or near-shore sites allow plants to operate with related industries such as mariculture or those that require desalinated water.
Favored locations include those with narrow shelves (volcanic islands), steep (15-20 degrees) offshore slopes, and relatively smooth sea floors. These sites minimize the length of the intake pipe. A land-based plant could be built well inland from the shore, offering more protection from storms, or on the beach, where the pipes would be shorter. In either case, easy access for construction and operation helps lower costs.
Land-based or near-shore sites can also support mariculture or chilled water agriculture. Tanks or lagoons built on shore allow workers to monitor and control miniature marine environments. Mariculture products can be delivered to market via standard transport.
One disadvantage of land-based facilities arises from the turbulent wave action in the surf zone. OTEC discharge pipes should be placed in protective trenches to prevent subjecting them to extreme stress during storms and prolonged periods of heavy seas. Also, the mixed discharge of cold and warm seawater may need to be carried several hundred meters offshore to reach the proper depth before it is released, requiring additional expense in construction and maintenance.
One way that OTEC systems can avoid some of the problems and expenses of operating in a surf zone is by building them just offshore in waters ranging from 10 to 30 meters deep (Ocean Thermal Corporation 1984). This type of plant would use shorter (and therefore less costly) intake and discharge pipes, which would avoid the dangers of turbulent surf. The plant itself, however, would require protection from the marine environment, such as breakwaters and erosion-resistant foundations, and the plant output would need to be transmitted to shore.[28]
Shelf based[edit]
To avoid the turbulent surf zone as well as to move closer to the cold-water resource, OTEC plants can be mounted to the continental shelf at depths up to 100 meters (330 ft). A shelf-mounted plant could be towed to the site and affixed to the sea bottom. This type of construction is already used for offshore oil rigs. The complexities of operating an OTEC plant in deeper water may make them more expensive than land-based approaches. Problems include the stress of open-ocean conditions and more difficult product delivery. Addressing strong ocean currents and large waves adds engineering and construction expense. Platforms require extensive pilings to maintain a stable base. Power delivery can require long underwater cables to reach land. For these reasons, shelf-mounted plants are less attractive.[28][citation needed]
Floating OTEC facilities operate off-shore. Although potentially optimal for large systems, floating facilities present several difficulties. The difficulty of mooring plants in very deep water complicates power delivery. Cables attached to floating platforms are more susceptible to damage, especially during storms. Cables at depths greater than 1000 meters are difficult to maintain and repair. Riser cables, which connect the sea bed and the plant, need to be constructed to resist entanglement.[28][citation needed]
As with shelf-mounted plants, floating plants need a stable base for continuous operation. Major storms and heavy seas can break the vertically suspended cold-water pipe and interrupt warm water intake as well. To help prevent these problems, pipes can be made of flexible polyethylene attached to the bottom of the platform and gimballed with joints or collars. Pipes may need to be uncoupled from the plant to prevent storm damage. As an alternative to a warm-water pipe, surface water can be drawn directly into the platform; however, it is necessary to prevent the intake flow from being damaged or interrupted during violent motions caused by heavy seas.[28][citation needed]
Connecting a floating plant to power delivery cables requires the plant to remain relatively stationary. Mooring is an acceptable method, but current mooring technology is limited to depths of about 2,000 meters (6,600 ft). Even at shallower depths, the cost of mooring may be prohibitive.[citation needed]
Some proposed projects[edit]
OTEC projects under consideration include a small plant for the U.S. Navy base on the British overseas territory island of Diego Garcia in the Indian Ocean. Ocean Thermal Energy Corporation (formerly OCEES International, Inc.) is working with the U.S. Navy on a design for a proposed 13-MW OTEC plant, to replace the current diesel generators. The OTEC plant would also provide 1.25 million gallons[clarification needed] per day of potable water. This project is currently waiting for changes in US military contract policies. OTE has proposed building a 10-MW OTEC plant on Guam.
Lockheed Martin's Alternative Energy Development team has partnered with Makai Ocean Engineering[29] to complete the final design phase of a 10-MW closed cycle OTEC pilot system which will become operational in Hawaii in the 2012-2013 time frame. This system is being designed to expand to 100-MW commercial systems in the near future. In November, 2010 the U.S. Naval Facilities Engineering Command (NAVFAC) awarded Lockheed Martin a US$4.4 million contract modification to develop critical system components and designs for the plant, adding to the 2009 $8.1 million contract and two Department of Energy grants totaling over $1 million in 2008 and March 2010.[30] This effort was canceled when the Navy determined that the system was not viable.
On April 13, 2013 Lockheed contracted with the Reignwood Group to build a 10 megawatt plant off the coast of southern China to provide power for a planned resort on Hainan island.[31] A plant of that size would power several thousand homes.[32][33] The Reignwood Group acquired Opus Offshore in 2011 which forms its Reignwood Ocean Engineering division which also is engaged in development of deepwater drilling.[34]
Okinawa Prefecture has announced the start of the OTEC operation test at Kume Island on April 15, 2013. The main aim is to examine the expected fluctuation of electricity supply caused by changes in weather, season, and sea temperature. The testing and research will be conducted with the support of Saga University until the end of 2014. IHI Plant Construction Co. Ltd, Yokogawa Electric Corporation, and Xenesys Inc were entrusted to construct the 50 kilowattplant in the territory of the Okinawa Prefectural Deep Sea Water Research Center. The plant installation was finished in March and the first trial run was held on the 30th of March. The location was specifically chosen in order to utilize the existing intake pipe developed by the research center. The pipe had been used in the past for the intake of deep sea water for fishery and agricultural use.[35]
Related activities[edit]
OTEC has uses other than power production.
Desalinated water can be produced in open- or hybrid-cycle plants using surface condensers to turn evaporated seawater into potable water. System analysis indicates that a 2-megawatt plant could produce about 4,300 cubic metres (150,000 cu ft) of desalinated water each day.[36] Another system patented by Richard Bailey creates condensate water by regulating deep ocean water flow through surface condensers correlating with fluctuating dew-point temperatures.[37] This condensation system uses no incremental energy and has no moving parts.
Air conditioning[edit]
The 41 °F (5 °C) cold seawater made available by an OTEC system creates an opportunity to provide large amounts of cooling to industries and homes near the plant. The water can be used in chilled-water coils to provide air-conditioning for buildings. It is estimated that a pipe 1 foot (0.30 m) in diameter can deliver 4,700 gallons of water per minute. Water at 43 °F (6 °C) could provide more than enough air-conditioning for a large building. Operating 8,000 hours per year in lieu of electrical conditioning selling for 5-10¢ per kilowatt-hour, it would save $200,000-$400,000 in energy bills annually.[38]
The InterContinental Resort and Thalasso-Spa on the island of Bora Bora uses an OTEC system to air-condition its buildings.[39] The system passes seawater through a heat exchanger where it cools freshwater in a closed loop system. This freshwater is then pumped to buildings and directly cools the air.
In 2010, Copenhagen Energy opened a district cooling plant in Copenhagen, Denmark. The plant delivers cold seawater to commercial and industrial buildings, and has reduced electricity consumption by 80 percent.[40] Ocean Thermal Energy Corporation (OTE) has designed a 9800 ton SDC system for a vacation resort in The Bahamas.
Chilled-soil agriculture[edit]
OTEC technology supports chilled-soil agriculture. When cold seawater flows through underground pipes, it chills the surrounding soil. The temperature difference between roots in the cool soil and leaves in the warm air allows plants that evolved in temperate climates to be grown in the subtropics. Dr. John P. Craven, Dr. Jack Davidson and Richard Bailey patented this process and demonstrated it at a research facility at the Natural Energy Laboratory of Hawaii Authority (NELHA).[41] The research facility demonstrated that more than 100 different crops can be grown using this system. Many normally could not survive in Hawaii or at Keahole Point.[citation needed]
Aquaculture is the best-known byproduct, because it reduces the financial and energy costs of pumping large volumes of water from the deep ocean. Deep ocean water contains high concentrations of essential nutrients that are depleted in surface waters due to biological consumption. This "artificial upwelling" mimics the natural upwellings that are responsible for fertilizing and supporting the world's largest marine ecosystems, and the largest densities of life on the planet.
Cold-water delicacies, such as salmon and lobster, thrive in this nutrient-rich, deep, seawater. Microalgae such as Spirulina, a health food supplement, also can be cultivated. Deep-ocean water can be combined with surface water to deliver water at an optimal temperature.
Non-native species such as salmon, lobster, abalone, trout, oysters, and clams can be raised in pools supplied by OTEC-pumped water. This extends the variety of fresh seafood products available for nearby markets. Such low-cost refrigeration can be used to maintain the quality of harvested fish, which deteriorate quickly in warm tropical regions. In Kona, Hawaii, aquaculture companies working with NELHA generate about $40 million annually, a significant portion of Hawaii's GDP.[42]
The NELHA plant established in 1993 produced anaverage of 7,000 gallons of freshwater per day. KOYO USA was established in 2002 to capitalize on this new economic opportunity. KOYO bottles the water produced by the NELHA plant in Hawaii. With the capacity to produce one million bottles of water every day, KOYO is now Hawaii's biggest exporter with $140 million in sales.[43]
Hydrogen production[edit]
Hydrogen can be produced via electrolysis using OTEC electricity. Generated steam with electrolyte compounds added to improve efficiency is a relatively pure medium for hydrogen production. OTEC can be scaled to generate large quantities of hydrogen. The main challenge is cost relative to other energy sources and fuels.
Mineral extraction[edit]
The ocean contains 57 trace elements in salts and other forms and dissolved in solution. In the past, most economic analyses concluded that mining the ocean for trace elements would be unprofitable, in part because of the energy required to pump the water. Mining generally targets minerals that occur in high concentrations, and can be extracted easily, such as magnesium. With OTEC plants supplying water, the only cost is for extraction.[citation needed] The Japanese investigated the possibility of extracting uranium and found developments in other technologies (especially materials sciences) were improving the prospects.[citation needed]
Political concerns[edit]
Because OTEC facilities are more-or-less stationary surface platforms, their exact location and legal status may be affected by the United Nations Convention on the Law of the Sea treaty (UNCLOS). This treaty grants coastal nations 3-, 12-, and 200-mile (320 km) zones of varying legal authority from land, creating potential conflicts and regulatory barriers. OTEC plants and similar structures would be considered artificial islands under the treaty, giving them no independent legal status. OTEC plants could be perceived as either a threat or potential partner to fisheries or to seabed mining operations controlled by the International Seabed Authority.
Cost and economics[edit]
For OTEC to be viable as a power source, the technology must have tax and subsidy treatment similar to competing energy sources. Because OTEC systems have not yet been widely deployed, cost estimates 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.[44]
Beneficial factors that should be taken into account include OTEC's lack of waste products and fuel consumption, the area in which it is available,[citation needed] (often within 20° of the equator)[45] the geopolitical effects of petroleum dependence, compatibility with alternate forms of ocean power such as wave energy, tidal energy and methane hydrates, and supplemental uses for the seawater.[46]
A rigorous treatment of OTEC reveals that a 20 °C temperature difference will provide as much energy as a hydroelectric plant with 34 m head for the same volume of water flow. The low temperature difference means that water volumes must be very large to extract useful amounts of heat. A 100MW power plant would be expected to pump on the order of 12 million gallons (44,400 metric tonnes) per minute.[47] For comparison, pumps must move a mass of water greater than the weight of the Battleship Bismark, which weighed 41,700 metric tons, every minute. This makes pumping a substantial parasitic drain on energy production in OTEC systems, with one Lockheed design consuming 19.55 MW in pumping costs for every 49.8 MW net electricity generated. For OTEC schemes using heat exchangers, to handle this volume of water the exchangers need to be enormous compared to those used in conventional thermal power generation plants,[48] making them one of the most critical components due to their impact on overall efficiency. A 100 MW OTEC power plant would require 200 exchangers each larger than a 20 foot shipping container making them the single most expensive component.[49]
Variation of ocean temperature with depth[edit]
The total insolation received by the oceans (covering 70% of the earth's surface, with clearness index of 0.5 and average energy retention of 15%) is: 5.45×1018 MJ/yr × 0.7 × 0.5 × 0.15 = 2.87×1017 MJ/yr
We can use Lambert's law to quantify the solar energy absorption by water,
where, y is the depth of water, I is intensity and μ is the absorption coefficient. Solving the above differential equation,
The absorption coefficient μ may range from 0.05 m−1 for very clear fresh water to 0.5 m−1 for very salty water.
Since the intensity falls exponentially with depth y, heat absorption is concentrated at the top layers. Typically in the tropics, surface temperature values are in excess of 25 °C (77 °F), while at 1 kilometer (0.62 mi), the temperature is about 5–10 °C (41–50 °F). The warmer (and hence lighter) waters at the surface means there are no thermal convection currents. Due to the small temperature gradients, heat transfer by conduction is too low to equalize the temperatures. The ocean is thus both a practically infinite heat source and a practically infinite heat sink.[clarification needed]
This temperature difference varies with latitude and season, with the maximum in tropical, subtropical and equatorial waters. Hence the tropics are generally the best OTEC locations.
Open/Claude cycle[edit]
In this scheme, warm surface water at around 27 °C (81 °F) enters an evaporator at pressure slightly below the saturation pressures causing it to vaporize.
Where Hf is enthalpy of liquid water at the inlet temperature, T1.
This temporarily superheated water undergoes volume boiling as opposed to pool boiling in conventional boilers where the heating surface is in contact. Thus the water partially flashes to steam with two-phase equilibrium prevailing. Suppose that the pressure inside the evaporator is maintained at the saturation pressure, T2.
Here, x2 is the fraction of water by mass that vaporizes. The warm water mass flow rate per unit turbine mass flow rate is 1/x2.
The low pressure in the evaporator is maintained by a vacuum pump that also removes the dissolved non-condensable gases from the evaporator. The evaporator now contains a mixture of water and steam of very low vapor quality (steam content). The steam is separated from the water as saturated vapor. The remaining water is saturated and is discharged to the ocean in the open cycle. The steam is a low pressure/high specific volume working fluid. It expands in a special low pressure turbine.
Here, Hg corresponds to T2. For an ideal isentropic (reversible adiabatic) turbine,
The above equation corresponds to the temperature at the exhaust of the turbine, T5. x5,s is the mass fraction of vapor at state 5.
The enthalpy at T5 is,
This enthalpy is lower. The adiabatic reversible turbine work = H3-H5,s .
Actual turbine work WT = (H3-H5,s) x polytropic efficiency
The condenser temperature and pressure are lower. Since the turbine exhaust is to be discharged back into the ocean, a direct contact condenser is used to mix the exhaust with cold water, which results in a near-saturated water. That water is now discharged back to the ocean.
H6=Hf, at T5. T7 is the temperature of the exhaust mixed with cold sea water, as the vapour content now is negligible,
The temperature differences between stages include that between warm surface water and working steam, that between exhaust steam and cooling water, and that between cooling water reaching the condenser and deep water. These represent external irreversibilities that reduce the overall temperature difference.
The cold water flow rate per unit turbine mass flow rate,
Turbine mass flow rate,
Warm water mass flow rate,
Cold water mass flow rate
Closed Anderson cycle[edit]
Developed starting in the 1960s by J. Hilbert Anderson of Sea Solar Power, Inc. In this cycle, QH is the heat transferred in the evaporator from the warm sea water to the working fluid. The working fluid exits the evaporator as a gas near its dew point.
The high-pressure, high-temperature gas then is expanded in the turbine to yield turbine work, WT. The working fluid is slightly superheated at the turbine exit and the turbine typically has an efficiency of 90% based on reversible, adiabatic expansion.
From the turbine exit, the working fluid enters the condenser where it rejects heat, -QC, to the cold sea water. The condensate is then compressed to the highest pressure in the cycle, requiring condensate pump work, WC. Thus, the Anderson closed cycle is a Rankine-type cycle similar to the conventional power plant steam cycle except that in the Anderson cycle the working fluid is never superheated more than a few degrees Fahrenheit. Owing to viscous effects, working fluid pressure drops in both the evaporator and the condenser. This pressure drop, which depends on the types of heat exchangers used, must be considered in final design calculations but is ignored here to simplify the analysis. Thus, the parasitic condensate pump work, WC, computed here will be lower than if the heat exchanger pressure drop was included. The major additional parasitic energy requirements in the OTEC plant are the cold water pump work, WCT, and the warm water pump work, WHT. Denoting all other parasitic energy requirements by WA, the net work from the OTEC plant, WNP is
The thermodynamic cycle undergone by the working fluid can be analyzed without detailed consideration of the parasitic energy requirements. From the first law of thermodynamics, the energy balance for the working fluid as the system is
where WN = WT + WC is the net work for the thermodynamic cycle. For the idealized case in which there is no working fluid pressure drop in the heat exchangers,
so that the net thermodynamic cycle work becomes
Subcooled liquid enters the evaporator. Due to the heat exchange with warm sea water, evaporation takes place and usually superheated vapor leaves the evaporator. This vapor drives the turbine and the 2-phase mixture enters the condenser. Usually, the subcooled liquid leaves the condenser and finally, this liquid is pumped to the evaporator completing a cycle.
Environmental impact[edit]
Carbon dioxide dissolved in deep cold and high pressure layers is brought up to the surface and released as the water warms.[citation needed]
Mixing of deep ocean water with shallower water brings up nutrients and makes them available to shallow water life. This may be an advantage for aquaculture of commercially important species, but may also unbalance the ecological system around the power plant.[citation needed]
OTEC plants use very large flows of warm surface seawater and cold deep seawater to generate constant renewable power. The deep seawater is oxygen deficient and generally 20-40 times more nutrient rich (in nitrate and nitrite) than shallow seawater. When these plumes are mixed, they are slightly denser than the ambient seawater.[50] Though no large scale physical environmental testing of OTEC has been done, computer models have been developed to simulate the effect of OTEC plants.
Hydrodynamic Modeling Work[edit]
In 2010, a computer model was developed to simulate the physical oceanographic effects of one or several 100 megawatt OTEC plant(s). The model suggests that OTEC plants can be configured such that the plant can conduct continuous operations, with resulting temperature and nutrient variations that are within naturally occurring levels. Studies to date suggest that by discharging the OTEC flows downwards at a depth below 70 meters, the dilution is adequate and nutrient enrichment is small enough so that 100 megawatt OTEC plants could be operated in a sustainable manner on a continuous basis. [51]
Biological Modeling Work[edit]
The nutrients from an OTEC discharge could potentially cause increased biological activity if they accumulate in large quantities in the photic zone.[51] In 2011 a biological component was added to the hydrodynamic computer model to simulate the biological response to plumes from 100 megawatt OTEC plants. In all cases modeled (discharge at 70 meters depth or more), no unnatural variations occurs in the upper 40 meters of the ocean's surface.[50] The picoplankton response in the 110 - 70 meter depth layer is approximately a 10-25% increase, which is well within naturally occurring variability. The nanoplankton response is negligible. The enhanced productivity of diatoms (microplankton) is small. The subtle phytoplankton increase of the baseline OTEC plant suggests that higher-order biochemical effects will be very small.[50]
Environmental Impact Studies[edit]
A previous Final Environmental Impact Statement (EIS) for the United States' NOAA from 1981 is available,[52] but needs to be brought up to current oceanographic and engineering standards. Studies have been done to propose the best environmental baseline monitoring practices, focusing on a set of ten chemical oceanographic parameters relevant to OTEC.[53] Most recently, NOAA held an OTEC Workshop in 2010 and 2012 seeking to assess the physical, chemical, and biological impacts and risks, and identify information gaps or needs.[54] [55]
Technical difficulties[edit]
Dissolved gases[edit]
The performance of direct contact heat exchangers operating at typical OTEC boundary conditions is important to the Claude cycle. Many early Claude cycle designs used a surface condenser since their performance was well understood. However, direct contact condensers offer significant disadvantages. As cold water rises in the intake pipe, the pressure decreases to the point where gas begins to evolve. If a significant amount of gas comes out of solution, placing a gas trap before the direct contact heat exchangers may be justified. Experiments simulating conditions in the warm water intake pipe indicated about 30% of the dissolved gas evolves in the top 8.5 meters (28 ft) of the tube. The trade-off between pre-dearation[56] of the seawater and expulsion of non-condensable gases from the condenser is dependent on the gas evolution dynamics, deaerator efficiency, head loss, vent compressor efficiency and parasitic power. Experimental results indicate vertical spout condensers perform some 30% better than falling jet types.
Microbial fouling[edit]
Because raw seawater must pass through the heat exchanger, care must be taken to maintain good thermal conductivity. Biofouling layers as thin as 25 to 50 micrometres (0.00098 to 0.00197 in) can degrade heat exchanger performance by as much as 50%.[22] A 1977 study in which mock heat exchangers were exposed to seawater for ten weeks concluded that although the level of microbial fouling was low, the thermal conductivity of the system was significantly impaired.[57] The apparent discrepancy between the level of fouling and the heat transfer impairment is the result of a thin layer of water trapped by the microbial growth on the surface of the heat exchanger.[57]
Another study concluded that fouling degrades performance over time, and determined that although regular brushing was able to remove most of the microbial layer, over time a tougher layer formed that could not be removed through simple brushing.[22] The study passed sponge rubber balls through the system. It concluded that although the ball treatment decreased the fouling rate it was not enough to completely halt growth and brushing was occasionally necessary to restore capacity. The microbes regrew more quickly later in the experiment (i.e. brushing became necessary more often) replicating the results of a previous study.[58] The increased growth rate after subsequent cleanings appears to result from selection pressure on the microbial colony.[58]
Continuous use of 1 hour per day and intermittent periods of free fouling and then chlorination periods (again 1 hour per day) were studied. Chlorination slowed but did not stop microbial growth; however chlorination levels of .1 mg per liter for 1 hour per day may prove effective for long term operation of a plant.[22] The study concluded that although microbial fouling was an issue for the warm surface water heat exchanger, the cold water heat exchanger suffered little or no biofouling and only minimal inorganic fouling.[22]
Besides water temperature, microbial fouling also depends on nutrient levels, with growth occurring faster in nutrient rich water.[59] The fouling rate also depends on the material used to construct the heat exchanger. Aluminium tubing slows the growth of microbial life, although the oxide layer which forms on the inside of the pipes complicates cleaning and leads to larger efficiency losses.[58] In contrast, titanium tubing allows biofouling to occur faster but cleaning is more effective than with aluminium.[58]
The evaporator, turbine, and condenser operate in partial vacuum ranging from 3% to 1% of atmospheric pressure. The system must be carefully sealed to prevent in-leakage of atmospheric air that can degrade or shut down operation. In closed-cycle OTEC, the specific volume of low-pressure steam is very large compared to that of the pressurized working fluid. Components must have large flow areas to ensure steam velocities do not attain excessively high values.
Parasitic power consumption by exhaust compressor[edit]
An approach for reducing the exhaust compressor parasitic power loss is as follows. After most of the steam has been condensed by spout condensers, the non-condensible gas steam mixture is passed through a counter current region which increases the gas-steam reaction by a factor of five. The result is an 80% reduction in the exhaust pumping power requirements.
Cold air/warm water conversion[edit]
In winter in coastal Arctic locations, the delta T between the seawater and ambient air can be as high as 40 °C (72 °F). Closed-cycle systems could exploit the air-water temperature difference. Eliminating seawater extraction pipes might make a system based on this concept less expensive than OTEC. This technology is due to H. Barjot, who suggested butane as cryogen, because of its boiling point of −0.5 °C (31.1 °F) and its non-solubility in water.[60] Assuming a level of efficiency of realistic 4%, calculations show that the amount of energy generated with one cubic meter water at a temperature of 2 °C (36 °F) in a place with an air temperature of −22 °C (−8 °F) equals the amount of energy generated by letting this cubic meter water run through a hydroelectric plant of 4000 feet (1,200 m) height.[61]
Barjot Polar Power Plants could be located on islands in the polar region or designed as swimming barges or platforms attached to the ice cap. The weather station Myggbuka at Greenlands east coast for example, which is only 2,100 km away from Glasgow, detects monthly mean temperatures below −15 °C (5 °F) during 6 winter months in the year.[62]
See also[edit]
- ^ a b c DiChristina, Mariette (May 1995). "Sea Power". Popular Science: 70–73. Retrieved Nov 2011.
- ^ Chiles, James (Winter 2009). "The Other Renewable Energy". Invention and Technology 23 (4): 24–35.
- ^ "Power from the Sea" Popular Mechanics, December 1930, pp 881-882 detail article and photos of Cuban power plant
- ^ a b c d Takahashi, Masayuki Mac; Translated by: Kitazawa, Kazuhiro and Snowden, Paul (2000) [1991]. Deep Ocean Water as Our Next Natural Resource. Tokyo, Japan: Terra Scientific Publishing Company. ISBN 4-88704-125-X.
- ^ Avery, William H. and Chih Wu. Renewable Energy From the Ocean: A Guide to OTEC. New York: Oxford University Press. 1994.
- ^ US patent 3312054, J.H. Anderson, "Sea Water Power Plant", issued 1967-04-04
- ^ Avery, William H. and Chih Wu. Renewable Energy From the Ocean: A Guide to OTEC. New York: Oxford University Press. 1994.
- ^ a b Bruch, Vicki L. (April 1994). An Assessment of Research and Development Leadership in Ocean Energy Technologies (PDF). SAND93-3946. Sandia National Laboratories: Energy Policy and Planning Department.
- ^ Mitsui, T.; Ito, F.; Seya, Y.; Nakamoto, Y. (September 1983). "Outline of the 100 kW OTEC Pilot Plant in the Republic of Nauru". IEEE Transactions on Power Apparatus and Systems. PAS-102 (9): 3167–3171. doi:10.1109/TPAS.1983.318124.
- ^ Finney, Karen Anne. "Ocean Thermal Energy Conversion". Guelph Engineering Journal. 2008.
- ^ Daly, John (December 5, 2011). "Hawaii About to Crack Ocean Thermal Energy Conversion Roadblocks?". OilPrice.com. Retrieved 28 March 2013.
- ^ "Average Retail Price of Electricity to Ultimate Customers by End-Use Sector, by State". Energy Information Administration. September 2007.
- ^ a b L. Meyer, D. Cooper, R. Varley. "Are We There Yet? A Developer's Roadmap to OTEC Commercialization". Hawaii National Marine Renewable Energy Center. Retrieved 28 March 2013.
- ^ a b Avery, William H. and Chih Wu. Renewable Energy From the Ocean: A Guide to OTEC. New York: Oxford UniversityPress. 1994.
- ^ "Deep Pipelines for Ocean Thermal Energy Conversion". Retrieved 2009-02-16.
- ^ otecfoundation. "Makai Ocean Engineering's Heat Exchanger Test Facility opened". www.otecnews.org. Retrieved 28 March 2013.
- ^ Staff. "Makai Ocean Engineering working with Navy on Big Island OTEC project". Retrieved 28 March 2013.
- ^ IDEA. "Makai Ocean Engineering to add 100kW turbine generator to Kona, Hawaii OTEC test facility". International District Energy Association.
- ^ "Projects". Ocean Thermal EnergyPLC. Web. 24 June 2013. available at: http://www.oteplc.com/strategic_development.html
- ^ http://news.caribseek.com/index.php/caribbean-islands-news/bahamas-news/the-nassau-guardian-news/item/20288-eia-puts-otecproject-on-rocks
- ^ http://www3.nhk.or.jp/nhkworld/english/radio/asx/201307301430.asx
- ^ a b c d e Berger LR, Berger JA (June 1986). "Countermeasures to Microbiofouling in Simulated Ocean Thermal Energy Conversion Heat Exchangers with Surface and Deep Ocean Waters in Hawaii". Appl. Environ. Microbiol. 51 (6): 1186–1198. PMC 239043. PMID 16347076.
- ^ US patent 4311012, Warren T. Finley, "Method and apparatus for transferring cold seawater upward from the lower depths of the ocean to improve the efficiency of ocean thermal energy conversion systems", issued 1982-01-19
- ^ Trimble, L.C.; Owens, W.L. (1980). "Review of mini-OTEC performance". Energy to the 21st century; Proceedings of the Fifteenth Intersociety Energy Conversion Engineering Conference 2: 1331–1338. Bibcode:1980iece....2.1331T.
- ^ Vega, L.A. (1999). "Open Cycle OTEC". OTEC News. The GreenOcean Project. Retrieved 4 February 2011.
- ^ Lee, C. K. B.; Ridgway, Stuart (May, 1983), "Vapor/Droplet Coupling and the Mist Flow (OTEC) Cycle", Journal of Solar Energy Engineering 105
- ^ a b "Achievements in OTEC Technology". National Renewable Energy Laboratory.
- ^ a b c d "Design and Location". What is Ocean Thermal Energy Conversion?. National Renewable Energy Laboratory. Retrieved 22 January 2012.
- ^ "Lockheed Martin awarded another $4.4M for OTEC work in Hawaii". November 22, 2010. Retrieved December, 2010.
- ^ Coxworth, Ben (November 26, 2010). "More funds for Hawaii's Ocean Thermal Energy Conversion plant". Retrieved December, 2010.
- ^ Daniel Cusick (May 1, 2013). "CLEAN TECHNOLOGY: U.S.-designed no-emission power plant will debut off China's coast". ClimateWire E&E Publishing. Retrieved May 2, 2013.
- ^ David Alexander (April 16, 2013). "Lockheed to build 10-megawatt thermal power plant off southern China". Reuters. Retrieved April 17, 2013.
- ^ "Tapping Into the Ocean's Power: Lockheed Martin signs agreement for largest ever OTEC plant". Lockheed Martin. Retrieved April 17, 2013.
- ^ "Reignwood Ocean Engineering". Reignwood Group. Retrieved April 17, 2013.
- ^ http://www.otecnews.org/2013/05/otec-testing-in-okinawa/
- ^ Block and Lalenzuela 1985
- ^ U.S. Department of Energy, 1989
- ^ "YouTube video on the OTEC air-conditioning system used at the InterContinental Resort and Thalasso-Spa on the island of Bora Bora". Retrieved 2007-05-28.
- ^ Green Tech. "Copenhagen's SeawaterCooling Delivers Energy And Carbon Savings". 24 October 2012. Forbes.
- ^ us 7069689
- ^ Ponia, Ben. "Aquaculture Updates inthe Northern Pacific: Hawaii, Federated Sates of Mirconesia, Palau and Saipan". SPCFisheries Newsletter. July 2006. Web. 25 June 2013. available at: http://www.spc.int/DigitalLibrary/Doc/FAME/InfoBull/FishNews/118/FishNews11 8_58_Ponia.pdf.
- ^ Thomas, Daniel. "A Brief History of OTEC Research at NELHA". NELHA. August 1999. Web. 25 June 2013. available at: http://library.greenocean.org/oteclibrary/otecpapers/OTEC%20History.pdf
- ^ [1][dead link]
- ^ "NREL: Ocean Thermal Energy Conversion - Markets for OTEC". Nrel.gov. Retrieved 2012-06-12.
- ^ "NREL: Ocean Thermal Energy Conversion Home Page". Nrel.gov. Retrieved 2012-06-12.
- ^ Hartman, Duke (October 2011), "Challenge And Promise Of OTEC", Ocean News, retrieved June 2012
- ^ Da Rosa, Aldo Vieira (2009). "Chapter 4:Ocean Thermal Energy Converters". Fundamentals of renewable energy processes. Academic Press. pp. 139 to 152. ISBN 0-12-374639-6.
- ^ Eldred, M. last2=Landherr (July 2010), "Comparison Of Aluminum Alloys And Manufacturing Processes Based On Corrosion Performance For Use In OTEC Heat Exchangers", Offshore Technology Conference 2010 (OTC 2010), Curran Associates, Inc., doi:10.4043/20702-MS, ISBN 9781617384264, retrieved May 28, 2010
- ^ a b c Grandelli, Pat. "Modeling the Physical and Biochemical Influence of Ocean Thermal Energy Conversion Plant Discharges into their Adjacent Waters". US Department of Energy - Office of Scientific and Technical Information. Retrieved 27 March 2013.
- ^ a b Rocheleau, Greg; Pat Grandelli (22 September 2011). "Physical and biological modeling of a 100 megawatt Ocean Thermal Energy Conversion discharge plume". Institute of Electrical and Electronics Engineers: 3. Retrieved 27 March 2013.
- ^ "Final Environmental Impact Statement for Commercial Ocean Thermal Energy Conversion (OTEC) Licensing". U.S. Dept of Commerce, National Oceanic and Atmospheric Administration. Retrieved 27 March 2013.
- ^ L.Vega, C.Comfort. "Environmental Assessment of Ocean Thermal Energy Conversion in Hawaii". Hawaii National Marine Renewable Energy Center. Retrieved 27 March 2013.
- ^ "Ocean Thermal Energy Conversion: Assessing Potential Physical, Chemical, and Biological Impacts and Risks". National Oceanic and Atmospheric Administration, Office of Ocean and Coastal Resource Management. Retrieved 27 March 2013.
- ^ "Ocean Thermal Energy Conversion: Information Needs Assessment". National Oceanic and Atmospheric Administration (NOAA) Office of Response and Restoration (ORR) and the Environmental Research Group at the University of New Hampshire (UNH). Retrieved 27 March 2013.
- ^ deaeration
- ^ a b Aftring RP, Taylor BF (October 1979). "Assessment of Microbial Fouling in an Ocean Thermal Energy Conversion Experiment". Appl. Environ. Microbiol. 38 (4): 734–739. PMC 243568. PMID 16345450.
- ^ a b c d Nickels JS, Bobbie RJ, Lott DF, Martz RF, Benson PH, White DC (June 1981). "Effect of Manual Brush Cleaning on Biomass and Community Structure of Microfouling Film Formed on Aluminum and Titanium Surfaces Exposed to Rapidly Flowing Seawater". Appl. Environ. Microbiol. 41 (6): 1442–1453. PMC 243937. PMID 16345798.
- ^ Trulear, MG; Characklis, WG (September 1982). "Dynamics of Biofilm Processes". Journal of the Water Pollution Control Federation 54 (9): 1288–1301.
- ^ "Science: Cold Power". Time. 1929-04-22.
- ^ "Achmed Khammas - Das Buch der Synergie - Teil C - Temperaturgradient". Buch-der-synergie.de. 2007-10-25. Retrieved 2012-06-12.
- ^ "Denmark - Myggbuka". Globalbioclimatics.org. Retrieved 2012-06-12.
- http://otecfoundation.org/
- http://otecnews.com/
- http://www.ioes.saga-u.ac.jp/en/about_lab.html (Saga University OTEC Research Facility)
- http://www.OTEC.ws
- http://www.lockheedmartin.com/us/products/otec.html
- http://www.makai.com/e-otec.htm
- http://www.bluerise.nl/
- http://www.ocees.com
- Renewable Energy From The Ocean - A Guide To OTEC, William H. Avery, Chih Wu, Oxford University Press, 1994. Covers the OTEC work done at the Johns Hopkins Applied Physics Laboratory from 1970–1985 in conjunction with the Department of Energy and other firms.
External links[edit]
- OTEC News - OTEC News website
- Educational material about OTEC by the NOAA Ocean Exploration program
- Ocean Energy Council: How does OTEC work?
- nrel.gov - what is OTEC?
- US Department of Energy, Information Resources
- Wired Magazine's interview with John Piña Craven on the future of OTEC
- 2007 edition of the Survey of Energy Resources produced by the World Energy Council
- The Green Ocean Project - OTEC Library
- Plumbing the oceans could bring limitless clean energy
- [2] Maximum water flow capacity of steel pipes - dimensions ranging 2 - 24 inches
The Engineering Toolbox. for other types of ocean energy go to ((tidal energy))


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Blood pressure generally is higher in the winter and lower in the summer. That's because low temperatures cause your blood vessels to narrow — which increases blood pressure because more pressure is needed to force blood through your narrowed veins and arteries.
In addition to cold weather, blood pressure may also be affected by a sudden change in weather patterns, such as a weather front or a storm. Your body — and blood vessels — may react to abrupt changes in humidity, atmospheric pressure, cloud cover or wind in much the same way it reacts to cold. These weather-related variations in blood pressure are more common in people age 65 and older.
Other seasonal causes of higher blood pressure include weight gain and decreased physical activity in winter. If you have high blood pressure already, continue to monitor your blood pressure readings as the seasons change and talk to your doctor. Your doctor may recommend changing the dose of your blood pressure medication or switching to another medication. Don't make any changes to your medications without talking to your doctor.
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text:
Theme : On Location : Vintage Tassie 1975
SnapDot: Images printed onto round fabric wall dots
Introducing SnapDot
We are very excited about our first SnapDot, a round fabric wall decal that is a bit of retro ~ vintage from 1975 in picturesque Tasmania. Back Story An image taken back in the 70s when my parents visited Tasmania on one of dad's many cricketing trips. It looks rather painterly and would make a […]


text:
"Cisco Linksys E4200 Review - Worth buying!"
on by TeaParty2009Pros Range, speed, it works, features.
Cons High price, but it works!
Summary Well, we needed a wireless router for a second location and the E4200 is our third router in three days as the other two, first the Linksys E2000 and then the Netgear WNDR3700V2, just would not give the distance or signal strength. All three were to be used in a ranch style single family residence with no second floor and no basement. Further, only two computers would be hooked-up, a hardwired computer and a laptop. The intended use of all three is for basic internet use, email, downloading, and movie streaming of Hulu and Netflix. The distance is through the house and outside to the back porch for the wireless connection through two bedrooms, a kitchen, and to the porch where I spend most of my time on the laptop. I would guess the distance between the laptop and the router is around 40-60 feet.
The first router we purchased was the Linksys E2000 because we did not need anything fancy and we did not want to spend the kind of money we did for another location which we use a Linksys 610. We do not need to hook up a printer for wireless use or use a router with a USB connection, so The Linksys E1000 at around $50.00 was our first choice, but the E2000 was only $10.00 more on sale so we went with that. The setup of the E2000 from the hardwired computer was very simple and I was very excited and had high expectations, until I went to the porch and saw only one bar out of five for signal strength. At this Poor connection, the laptop would either connect, or it would not; and if it did connect, the signal would drop and the connection would be lost. Rebooted router and moved router around a little for best results, but no change. Therefore, we did some research on the hardwired computer for "The best wireless router" and instantly noticed the Netgear WNDR3700 as the "Best" and off we went to "do it right this time" and we exchanged the Linksys E2000 for the Netgear WNDR3700V2.
The Netgear WNDR3700V2 was easy to setup on the hardwired and I was again excited to go to the laptop and finally be able to surf the internet and watch movies, but a quick glance at the signal strength and I was again disappointed as the 2.4ghz was only at 2 of 5 bars of signal strength and the 5ghz was only at 1 of 5 bars of signal strength. Rebooted router and moved router around a little for best results, but no change. Our laptop would connect at 2.4ghz, but only at a severely decreased speed which was VERY noticeable and severely lagging. The laptop would not connect at the 5ghz connection at all. Ok, now we are upset and very tired of this.
More internet searching revealed the same problems with the Netgear WNDR3700 that we were experiencing, which forced us to wonder why the WNDR3700 could even be considered a "Best wireless router" if it can not even be used at a distance of 40-60 feet? Now there are only two routers left, both from Cisco-Linksys, the E3000 and the NEW E4200. Professional reviews online show the E4200 is vastly superior to both the E3000 and the WNDR3700, so we went with this router even though it is WAY past what we wanted to spend, but the WNDR3700 was also WAY past what we wanted to spend.
The setup of the E4200 was the same as the E2000 we returned and is just super easy. After setup on the hardwired, I now walked cautiously to the laptop as I have already been disappointed twice. I sat down at the laptop, looked at the signal strength and was floored at the signal strength of 4 of 5 bars of signal strength! Internet searching, downloading, email, and movie watching is no different between the hardwired and the wireless.
In summary, we love everything about the E4200 except the price. Actually, we didn't like the price of the WNDR3700V2 either. However, without the E4200, we would not even have a connection so maybe I should not complain? I will say $130.00 to $180.00 for a router is stupid priced and I do not like it one bit. I wish the E2000 worked because it was only $60.00 on sale. The WNDR3700V2 was $129.99 and the E4200 was $179.99. In the end, we spent WAY more money than we wanted too for a distance of only 40-60 feet and the E4200 is the ONLY router to accomplish this seemingly simple task. -
"Awesome router!"
on by SpacePorkerPros Very fast, no signal drops, and easy to set up. It's worth the price. I have nothing bad to say about the laptop-like power supply; it's nice to have a regularly-sized cord to plug into the wall or powerstrip instead of a giant AC adaptor.
Cons None so far. Will update.
Summary If you want to use the 5 GHz and 2.4 GHz bands simultaneoulsy at an equally impressive range, this is the router for you.
After using the router for two months, I have had no problems with it. If you put the 2.4GHz band on mixed mode (broadcasting b/g/n) the router runs a little on the warm side but runs at a perfectly normal temperature otherwise. Aside from this, I have not noticed anything concerning.
Updated on Feb 27, 2011
Great router. -
"It just works. Exactly as it is supposed to."
onPros Tons of features. I'm broadcasting 3 SSIDs one for A & N at 5 GHZ, one for B, G, & N at 2.4GHZ, and a 3rd guest SSID for B,G, & N at 2.4GHZ! Unlike my prior routers, the use of features doesn't seem to come at the expense of stability or relia
Cons I will miss the LCD display on my Belkin N1 Vision. Linksys, can we get throughput monitoring on the device or in the firmware interface? Else the device is the latest and greatest, sleek, stable, and very capeable.
"Awesome Media Router"
on by Slipstream85Pros Works great with media devices.
Gigabit Ethernet ports
450 Mbps speedsCons Cisco Connect is for beginners and barely customizable, prefer web setup over it.
Summary Works great with media devices, I used AirPort Extreme and Netgear WNDR3700 did not work great with iPhone YouTube was slow loading and unwatchable.
on by choochoo22Pros Compact with nice styling. They finally put guest networking in the web interface. The USB port supports NTFS so media files larger than 4GB are OK.
Cons Unable to stream media 50' through wood walls. Weaker signal at the far end of my house than with an E3000 under the same conditions. Modern high-end router should have USB3 port & printer support. Hot. Not wallmountable. Activity lights not visible.
Summary Real world experience with a Cisco E3000, E4200, and Netgear XAVNB2001:
The objective was to provide wi-fi coverage for an iPad & iPod throughout our home and take the opportunity to connect the TV in our living room to the router in the office for media streaming and internet access. I purchased a Linksys/Cisco E3000 and Samsung TV wi-fi adapter for this purpose. The E3000 worked fine for the iPods since our DSL is so slow anyway but the signal to the TV was weak and too slow to stream media at a distance of about 50' through wooden walls and a floor.
I was concerned and somewhat confused about CNET's conclusion that the E3000 lacked the "Power" to stream HD from the attached USB storage. I wanted to be sure the problem wasn't the USB. Transferring files from a nearby computer through a gigabit wire, the Resource Manager measured 55 Mbps writing and 45 Mbps reading. While far from a gigabit, it successfully handled two HD, or one HD and two SD streams simultaneously so I am still confused about what CNET found lacking.
To confirm the bottleneck was wi-fi range, I moved the E3000 with disk to the living room and played files from the attached disk. Having no means to measure the bitrate, HD played perfectly both with a wired connection and wi-fi so the hardware was up to the task at close range. More wi-fi range was needed.
Relying on CNET's review showing greater range and speed, I purchased an E4200. This was very disappointing. The E4200 signal strength was consistently 1 "bar" lower than the E3000 under the same conditions even after moving it around. The 5 GHz band was so weak it intermittently disappeared. Apparently a wired connection was needed to get the signal to the living room.
I purchased a Netgear XAVNB2001 powerline kit with a wi-fi port at the far end. With a cable connecting the TV to the XAVN2001 and streaming through the powerline from the computer, the Resource Monitor measured 10 Mbps, not quite enough for the 12 Mbps file and far short of the 56.2 Mbps measured by CNET. Connecting the TV to the XAVN2001 through the wi-fi link was substantially slower even at a 3' range which suggests that the wi-fi capability of the XAVN2001 is inadequate for HD regardless of the powerline bitrate. The XAVN2001 w/wi-fi connection did not seem any faster than the weak E3000 signal 47' further away.
At this point I gave up throwing money and time at this project. Everything but the E3000 for the iPad is being returned and a media connection for the TV will have to wait for better working products.
As a personal observation; it is ludicrous that real world and even lab tests of networking products fall VASTLY short of specs and everyone just accepts that. What happened to truth in advertising? If the XAVNB2001 for example, had performed at just 10% of its rated 200 Mbps it would have worked fine. Suppose you bought a car rated at 30 MPG and it got less than 3 MPG? Would you accept that? The box advertising on all of these products said they were designed to do exactly what they all failed to do.


text:
It's Hatched! 68 Bought
Get your clubs and golf shoes shined up and ready to play 18 holes at Kenduskeag Golf & Country Club. You'll be able to play two rounds on this 9-hole course in one day, complete with cart rental for just $15 instead of $30—that's a straight-shooting savings of 50%. The course is located along picturesque Kenduskeag Stream and is surrounded by trees on three sides. Sounds like a tranquil way to spend a day.
Kenduskeag Golf & Country Club's clubhouse was opened in 2005 and is an ideal venue for functions of any sort. They offer a menu with something for everyone, making it an excellent spot for lunch with family and friends.
$15 for 18 holes of golf for 1 plus cart rental ($30 value)
Kenduskeag Golf & Country Club
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text:
Curious what your fav apps are. That is, the non-stock ones you use the most.
For me:
Hill Climb Racing (wish I could stop this one)
Let me know of any joy that I'm missing!
Curious what your fav apps are. That is, the non-stock ones you use the most.
For me:
Hill Climb Racing (wish I could stop this one)
Let me know of any joy that I'm missing!
A few of my favorites are
-titanium backup
-drop box
-xbox smart glass
-the chive
Sent from my DROID RAZR HD using Xparent Cyan Tapatalk 2
"She leans into me and I keep my arms around her. I don't fool myself that I hold her together -- She does that on her own -- But holding her keeps me from flying apart."
angry birds, angry birds star wars, angry birds seasons, angry birds space, and angry birds rio!
(my phone) + (me) =
Useful Links
1. SBF To Root/Unroot | 2. Everything Root | 3. Root With Any OS | 4. Overclocking 101 | 5. Learning the Lingo | 6. Post -Root | 7. Task Killers | 8.Anything Else? | 9. ADB | 10. RSDlite | 11. New Users Click Me! | 12. SBF Flashing Guide
Have a Problem, Click here to Visit the Rescue Squad
So hard to just name 5.
1) Droid Forums (I get any brownie points?)
2) ClockSync
3) ROM Toolbox Pro
4) Root Checker Pro
5) Root Cleaner
6) BusyBoxPro
TB is a given, I am BIG on DEV SUPPORT
Last edited by KaChow; 01-04-2013 at 10:02 PM. Reason: Updated added links for Favorite Apps
- dropbox
- dropsync (probably my favorite, but I'm an automation / sync fanatic)
- netflix
- nova launcher
Last edited by jntdroid; 01-04-2013 at 02:40 PM.
"...life is 10% what happens to me and 90% how I react to it."
Guidelines of Conduct
The only dumb question is the one not asked.
For the most part I use the root apps, much like other apps, the difference is the amount of control. The one app listed as #2 ClockSync, it overrides Verizon's system time and replaces it with time collected from an Atomic clock. Usually the difference is 10ths of a second depending on the running length. The other app BusyBoxPro I can temp unroot which hides superuser and supersu, however leaves BusyBoxPro and still take OTA very safely. These apps are simply used as wanted, whether its installed and once, done or tweak this or that.
Since, you mention you haven't found a reason to root, here's an app that may be interesting and it does not require root. The app is All About Root . Enjoy.
1. WeatherBug Elite
2. Tapatalk (for Droid Forums, Android Central and Android Forums)
3. PYKL3 Radar
4. aCalendar
5. Dropbox
Power Amp Pro
Tune-In Radio Pro
Swift Key 3
I do not NEED anything else!
Like to keep it simple...


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© Copyright by the designer Photographs, if shown, may reflect homeowner modifications
Entering from the loggia of this 2 story home you find yourself in the spacious foyer, overlooked by a plant shelf. The kitchen-breakfast area features a built-in desk, pantry closet, and central island. The first floor master suite features a luxurious bath with garden tub, separate shower, and twin sinks.
First Floor Plan:


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The Arakhnê.org Foundation Classes (AFC) is a collection of Java libraries (based on Maven) that provides a collection of utilities that are not provided in the standard Java API. Many utility classes are provided: file filters, progress indicators, arrays, collections, VM utilities, text utilities, math tools (point, vector, matrix, shape, etc.), widgets for AWT, Swing, and Android, a platform-independent graphical API, and more.
jWatchdog delivers a simple watchdog to actively monitor your infrastructure and send you notifications in case something goes wrong. It is configured using a simple XML configuration file. This configuration file can be changed on-the-fly without a need to restart the watchdog. jWatchdog does not offer data collection itself. It assumes that you already collected the data on which you want to run jWatchdog. The de facto standard tool Collectd is recommended for data collection. jWatchdog assumes that you use the RRDTool collectd output plugin to store the collected data in RRD files, or use Graphite as a datasource.
Xtreme Download Manager is a advanced and powerful tool to increase download speed up to 500%, resume broken/dead downloads, capture FLV videos from any site, and schedule downloads. It uses a sophisticated dynamic segmentation algorithm, data compression, and connection reuse to speed up the download process. It supports HTTP, HTTPS, and FTP protocols, firewalls, proxy servers, file redirects, cookies, authorization, etc. It seamlessly integrates with Firefox on any operating system. It also integrates with any other browser to handle downloads automatically using advanced browser integration. It is entirely written in Java, so it runs on any operating system without even being installed.
FroZenLight interrelates line arts, mathematics, and cryptography. Circular shaped mirrors which are arranged in a grid-like manner reflect a light ray according to the reflection law of geometric optics. While random positions of the light source produce chaotic reflection patterns, it is possible to position the light source so that beautiful symmetric reflection patterns are created.
APF is a code generator that codes your software as you drag and drop code-abstracts on a canvas. It can be trained by the community to code almost anything. With automatic programming, it will sometimes code 50% to 100% of small or large software projects. APF has successfully shipped some real life software. But APF must produce more diverse software projects. You can help APF grow by picking re-usable code from any existing open source. 'Metacode' that code and submit it to the APF marketplace. APF feeds on re-useable code submitted by the community. This way, APF gets trained to auto code more and more. You can also improve the way APF assembles code, or the way its Canvas lets the user drag and drop code abstracts.
Inq is a scripting language for client/server systems. The server provides transaction, persistence, concurrency, and events support. The client is presently desktop only, though Web clients are planned. Inq uses a generic node structure throughout and reification techniques to obviate boilerplate code, especially in the areas of persistence and MVC.


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Monday, November 07, 2005
More Currency
Part of the attention is coming from Warren Buffet who is unwinding his bet against the dollar.
The dollar has had a very strong move. That the move is getting a lot of attention on CNBC now is interesting. The issues that confront the US point to a weaker dollar long term, from the category that's just how markets work. However this just creates an expectation. Expectations do not have to come to fruition but a continued rally in the dollar going into next year would have to overcome some very big headwinds. Possible, but unlikely.
5 comments:
- David Andrew Taylor said...
I actually am starting to think that the dollar is ready for a strong rally. Take a look at the late 1990's. Higher interest rates with good equity growth. These are the same circumstances that we have now. The earnings for the S&P 500 of late have been healthy. We are more likely to see a stronger dollar going forward. As for the trade deficit, that isn't an issue at all. We don't produce material items any more. We produce investment opportunities in the form of U.S. debt. Foreigners love that kind of stuff. - 12:10 PM
- Roger Nusbaum said...
Thanks for the comment! Higher rates as a function of more inflation (potential or real) and more debt supply (here I'm thinking of 30 year treasuries coming in Feb) means, to me, higher rates coming from a position of weakness; not good for the dollar.
Does this hold any water? - 12:20 PM
- David Andrew Taylor said...
We are going to see higher rates for three reasons: First, normalization. We are just about there. This was Greenspan's first priority. Second, inflation. I don't see headline doing anything but going back down while energy prices are falling like they are. Core will contnue at a reasonable pace. Then lastly: Katrina. More paper coming to the market means higer interest rates. But there is a limit to how much is coming to the market. Once this has been absorbed, we'll likely see a leveling to normal rates. Keep in mind, 30-year rates are still well below normal (Historic) rates. Economic growth will continue at reasonable levels. I still see the new Fed chief lowering rates somewhat at some point to get that fine "tweaking" down.
As for the dollar, the higher interest rates (compared to trade partners) will be very attracive. Once the interest rate differential settles down, we'll likely see the growth differential be the driving factor in currencies. Still, though, we'll have higher rates than the Euroarea and Japan. Add in higher growth factors comparatively, and you can paint a picture that is dollar positive. - 1:10 PM
- Jack Miller said...
I actually bought a couple hundred long bonds today. The yield to maturity was 4.91% and I borrowed the money at 4.75%; good thing I didn't buy for the spread. I bought because I agree with David about inflation (clearly my belief is a little different in regard to long rates). Core inflation is low and the headline numbers are headed down; wages simply cannot get out of hand in a world of global competition. The rate increases by the FOMC amount to "real interest rates" when measured against anything but headline CPI and money flows to where it earns real returns.
I see continuing strength in the dollar which will continue to export the pain of higher oil to our trading partners in a double whammy way; forcing other nations to consider increase in short rates and gradually slowing the world economy.
The US will likely see a moderately slower economy and strength in the dollar at the same time! This is possible because productivity in the US has been huge relative to Europe for the past 10 years. Even China is raising rates to fight inflation.
Another bump by the FOMC will be enough to cause more talk about a recession; long rates will trade down and by next spring the FOMC will have to reduce short rates! By then, equities will be "on fire". - 9:36 PM
- Roger Nusbaum said...
that would be great if you turn out to be right.


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hello pacific coast cruisers I'm debating between 2001 chaparral 260 cabin cruiser and 2003 larson cabrio 274 for ocean stability and towing
at this moment I have seen both boats and I like both I'm basing my decision on which boat handel south ca coast swells as I have a 9 and 6 years old kids better and easier to tow, I'm not planing on renting a slip so most of the time I will be towing the boat , please advise thanks
Hey ashash
As far as towing, be advised that the Larson has the Duo Delta Conic Hull, a stepped hull, and the trailer needs to be set up for that type of bottom. Otherwise, towing is going to be equally easy--percentage diffs in weight and beam here come down to your vehicle and local regs more than ease.
Running, you might find that the Larson's stepped hull proves more efficient--many stepped hulls are. However, stepped hulls have much of the running trim built-in. Trimming the drives to raise the bow while running in following seas has less effect.
The Chaparral is a conventional V-hull, and no special trim or trailer techniques are required.It may be a tad less fuel efficient. Maybe.
All of this depends upon power as well. Are they powered , geared and propped the same?
In closing, every used boat is an individual. Who owned it, how it was used and cared for has more to do with used boat "quality" than who built it. Our advice is always to sea trial a boat before you buy and to get a survey done by a marine surveyor associated with NAMS or SAMS.