Consultar ensayos de calidad


Naval nuclear propulsion



Naval nuclear propulsion


Nuclear-powered warships during World War II submarine was found that could be a decisive weapon, but he had a serious problem: their need to emerge after short periods to obtain air for the combustion of diesel engines that were based (the invention of the snorkel improved somewhat the problem but not solved). Admiral Hyman G. Rickover was the first thought that nuclear energy could help with this problem.
The development of nuclear reactors allowed a new type of engine with key advantages:

1.No need air to the engine operation, and not based on combustion.
2.A small mass of nuclear fuel allows a range of several months (even years) without refueling. For example, U.S. submarines do not require refueling during its lifetime.



3.A motor drive that can match any other, so that submarines could be built much larger than the existing so far. The largest submarine built to date are the Russian Akula class (48 000 tons displacement, 175 m in length).
These advantages led to ships reaching speeds over 25 knots, they can stay weeks in deep dive and they can also store huge quantities of munitions (nuclear or conventional) in their warehouses. In fact, the U.S. military, France and the UK have only used this submarine propulsion system.
In the submarines have been used pressurized water reactors, boiling water or molten salt. For reducing the weight of fuel in thesereactors is used with high levels of uranium enrichment (30 to 40% of the Russians or the Americans 96%). These reactors have the advantage that it is not necessary (although possible) to turn the steam generated by heat into electricity, but can be used directly on a turbine that provides movement to the propellers that drive the ship, dramatically improving performance.
They have built a variety of military ships that use nuclear engines and, in some cases, turn missiles carrying medium or long-range nuclear warheads

Cruises. As the USS Long Beach (CGN-9), 2 C1W type nuclear reactors built.
Destroyers. As the USS Bainbridge (CGN-25) was the nuclear powered ship ever built smaller, use 2 D2G reactors integrated type.
Aircraft carriers. The most representative is the USS Enterprise (CVN-65), built in 1961 and still operating, using for propulsion type A2W 8 nuclear reactors.


Ballistic submarines. Use nuclear energy for propulsion and missile long-range and medium weapons. Akula class are of this type, using 2-type nuclear reactor OK-650 and carrying, in addition to conventional weapons, nuclear missiles 20 RSM-52, each with 10 warheads of 200 kilotons each.
Attack submarines. As the USS Seawolf (SSN-21) Seawolf class nuclear reactor that uses an integrated S6W PWR type. It reaches a speed of 30 knots

fuel cell is a device that converts the chemical energy from a fuel into electricity through achemical reaction with oxygen or another oxidizing agent[1] .
Buses
In total there are over 100 fuel cell buses deployed around the world today. Most buses are produced by UTC Power, Toyota, Ballard, Hydrogenics, and Proton Motor. UTC Buses have already accumulated over 970,000 km (600,000 mi) of driving 80] Fuel cell buses have a 30-141% higher fuel economy than diesel buses and natural gas buses.[81] Fuel cell buses have been deployed around the world including in Whistler Canada, San Francisco USA, Hamburg Germany, Shanghai China, London England, Sao Paulo Brazil as well as several others.[82] The Fuel Cell Bus Club is a global cooperative effort in trial fuel cell buses. Notable Projects Include:
* 12 Fuel cell buses are being deployed in the Oakland and San Francisco Bay area of California.[82]
* Daimler AG, with thirty-six experimental buses powered by Ballard Power Systems fuel cells completed a successful three-year trial, in eleven cities, in January 2007.[83][84]
* A fleet of Thor buses with UTC Power fuel cells was deployed in California, operated by SunLine Transit Agency.[85]
The first Brazilian hydrogen fuel cell bus prototype in Brazil was deployed in Sao Paulo. The bus was manufactured in Caxias do Sul and the hydrogen fuel will be produced in Sao Bernardo do Campo from water through electrolysis. The program, called 'Ônibus Brasileiro a Hidrogênio' (BrazilianHydrogen Autobus), includes three additional buses.[86][87]
Forklifts
Fuel cell powered forklifts are one of the largest sectors of fuel cell applications in the industry.[88] Most fuel cells used for material handling purposes are powered by PEM fuel cells, although some direct methanol fuel forklifts are coming onto the market. Fuel cell fleets are currently being operated by a large number of companies, including Sysco Foods, FedEx Freight, GENCO (at Wegmans, Coca-Cola, Kimberly Clark, Sysco Foods, and Whole Foods), and H-E-B Grocers.[89]Fuel cell powered forklifts provide significant benefits over both petroleum and battery powered forklifts as they produce no local emissions, can work for a full 8 hour shift on a single tank of hydrogen, can be refueled in 3 minutes and have a lifetime of 8–10 years. Fuel cell powered forklifts are often used in refrigerated warehouses as their performance is not degraded by lower temperatures. Many companies do not use petroleum powered forklifts, as these vehicles work indoors where emissions must be controlled and instead are turning towards electric forklifts. Fuel cell forklifts offer green house gas, product lifetime, maintenance cost, refueling and labor cost benefits over battery operated fork lifts.[90
Cooking
Solar cookers use sunlight for cooking, drying and pasteurization. They can be grouped into three broad categories: box cookers, panel cookers andreflector cookers 56] The simplest solar cooker is the box cooker first built by Horace de Saussure in 1767.[57] A basic box cooker consists of an insulated container with a transparent lid. It can be used effectively with partially overcast skies and will typically reach temperatures of 90–150 °C.[58] Panel cookers use a reflective panel to direct sunlight onto an insulated container and reach temperatures comparable to box cookers. Reflector cookers use various concentrating geometries (dish, trough, Fresnel mirrors) to focus light on a cooking container. These cookers reach temperatures of 315 °C and above but require direct light to function properly and must be repositioned to track the Sun 59]
The solar bowl is a concentrating technology employed by the Solar Kitchen in Auroville, Pondicherry, India, where a stationary spherical reflector focuses light along a line perpendicular to the sphere's interior surface, and a computer control system moves the receiver to intersect this line. Steam is produced in the receiver at temperatures reaching 150 °C and then used for process heat in the kitchen.[60]
A reflector developed by Wolfgang Scheffler in 1986 is used in many solar kitchens. Scheffler reflectors are flexible parabolic dishes that combine aspects of trough and power tower concentrators. Polar tracking is used to follow the Sun's daily course and the curvature of the reflector isadjusted for seasonal variations in the incident angle of sunlight. These reflectors can reach temperatures of 450–650 °C and have a fixed focal point, which simplifies cooking.[61] The world's largest Scheffler reflector system in Abu Road, Rajasthan, India is capable of cooking up to 35,000 meals a day.[62] As of 2008, over 2,000 large Scheffler cookers had been built worldwide.[63]


A windmill is a machine which converts the energy of wind into rotational energy by means of vanes called sails or blades.[1][2] Originally windmills were developed for milling grain for food production. In the course of history the windmill was adapted to many other industrial uses 3] An important application was to pump water. Windmills used for generating electricity are commonly known as wind turbines. A windmill used to generate electricity is commonly called a wind turbine. The first windmills for electricity production were built by the end of the 19th century by Prof James Blyth in Scotland (1887) 29][30] Charles F. Brush in Cleveland, Ohio (1887–1888)[31][32][33] and Poul la Cour in Denmark (1890s). La Cour's mill from 1896 later became the local powerplant of the village Askov. By 1908 there were 72 wind-driven electric generators in Denmark from 5 kW to 25 kW. By the 1930s windmills were widely used to generate electricity on farms in the United States where distribution systems had not yet been installed,built by companies like Jacobs Wind, Wincharger, Miller Airlite, Universal Aeroelectric, Paris-Dunn, Airline and Winpower and by the Dunlite Corporation for similar locations in Australia. Forerunners of modern horizontal-axis utility-scale wind generators were the WIME-3D in service in Balaklava USSR from 1931 until 1942, a 100 kW generator on a 30 m (100 ft) tower 34] the Smith-Putnam wind turbine built in 1941 on the mountain known as Grandpa's Knob in Castleton, Vermont, USA of 1.25 MW[35] and the NASA wind turbines developed from 1974 through the mid 1980's. The development of these 13 experimental wind turbines pioneered many of the wind turbine design technologies in use today, including: steel tube towers, variable-speed generators, composite blade materials, partial-span pitch control, as well as aerodynamic, structural, and acoustic engineering design capabilities. The modern wind power industry began in 1979 with the serial production of wind turbines by Danish manufacturers Kuriant, Vestas, Nordtank, and Bonus. These early turbines were small by today's standards, with capacities of 20–30 kW each. Since then, they have increased greatly in size, with the Enercon E-126 capable of delivering up to 7 MW, while wind turbine production has expanded to many countries.
As the 21st century began, rising concerns over energy security, global warming, and eventual fossil fuel depletion led to anexpansion of interest in all available forms of renewable energy. Worldwide there are now many thousands of wind turbines operating, with a total nameplate capacity of 194,400 MW 36] Europe accounted for 48% of the total in 2009.
A wind turbine looking like a windmill is De Nolet in Rotterdam.
A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour, lumber or textile production, or metal shaping. Typically, water is diverted from a river or impoundment or mill pond to a turbine or water wheel, along a channel or pipe (variously known as a flume, head race, mill race, leat, leet 56] lade (Scots) or penstock). The force of the water's movement drives the blades of a wheel or turbine, which in turn rotates an axle that drives the mill's other machinery. Water leaving the wheel or turbine is drained through a tail race, but this channel may also be the head race of yet another wheel, turbine or mill. The passage of water is controlled by sluice gates that allow maintenance and some measure of flood control; large mill complexes may have dozens of sluices controlling complicated interconnected races that feed multiple buildings and industrial processes. By the early 20th century, availability of cheap electrical energy made the watermill obsolete in developed countries although some smaller rural mills continued to operate commercially into the 1960s.A few historic mills such as the Newlin Mill and Yates Mill (an example of an Oliver Evans mill) (both USA) and The Darley Mill Centre (Yorkshire, UK)) still operate for demonstration purposes to this day, or even maintain small-scale commercial production as at Daniels Mill, Shropshire , Little Salkeld and Redbournbury Mill (All UK). Some old mills are being upgraded with modern Hydropower technology, for example those worked on by the South Somerset Hydropower Group in the UK.
Wood fuel is wood used as fuel. The burning of wood is currently the largest use of energy derived from a solid fuel biomass. Wood fuel can be used for cooking and heating, and occasionally for fueling steam engines and steam turbines that generate electricity. Wood fuel may be available as firewood (e.g. logs, bolts, blocks), charcoal, chips, sheets, pellets and sawdust. The particular form used depends upon factors such as source, quantity, quality and application. Sawmill waste and construction industry by-products also include various forms of lumber tailings. Some consider wood fuel bad for the environment, however this is not the case if proper techniques are used 1] One might increase carbon emissions using gas powered saws and splitters in the production of firewood, but when wood heat replaces carbon-producing fuels such as propane, heating oil or electricity from a coal-burning plant, then wood burning has apositive impact on the carbon footprint. The use of wood as a fuel source for heating is much older than civilization and was used by neanderthals. Historically, it was limited in use only by the distribution of technology required to make a spark. Wood heat is still common throughout much of the world. Some firewood is harvested in 'woodlots' managed for that purpose, but in heavily wooded areas it is more usually harvested as a byproduct of natural forests. Deadfall that has not started to rot is preferred, since it is already partly seasoned. Standing dead timber is considered better still, as it is both seasoned, and has less rot. Harvesting this form of timber reduces the speed and intensity of bushfires. Harvesting timber for firewood is normally carried out by hand with chainsaws.
A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. There are geothermal hot springs in many locations all over the crust of the earth. The water issuing from a hot spring is heated by geothermal heat, i.e., heat from the Earth's mantle. In general, the temperature of rocks within the earth increases with depth. The rate of temperature increase with depth is known as the geothermal gradient. If water percolates deeply enough into the crust, it will be heated as it comes into contact with hot rocks. The water from hot springs in non-volcanic areas isheated in this manner.
In active volcanic zones such as Yellowstone National Park, water may be heated by coming into contact with magma (molten rock). The high temperature gradient near magma may cause water to be heated enough that it boils or becomes superheated. If the water becomes so hot that it builds steam pressure and erupts in a jet above the surface of the Earth, it is called a geyser. If the water only reaches the surface in the form of steam, it is called a fumarole. If the water is mixed with mud and clay, it is called a mud pot.
Note that hot springs in volcanic areas are often at or near the boiling point. People have been seriously burned and even killed by accidentally or intentionally entering these springs.
Warm springs are sometimes the result of hot and cold springs mixing but may also occur outside of volcanic areas, such as Warm Springs, Georgia (frequented for its therapeutic effects by paraplegic U.S. President Franklin D. Roosevelt, who built the Little White House there). Because heated water can hold more dissolved solids, warm and especially hot springs also often have a very high mineral content, containing everything from simple calcium to lithium, and even radium. Because of both the folklore and the claimed medical value some of these springs have, they are often popular tourist destinations, and locations for rehabilitation clinics for those with disabilities 19][





Política de privacidad