You don't. Cubic meters is a measure of volume; joules or gigajoules is a measure of energy.You don't. Cubic meters is a measure of volume; joules or gigajoules is a measure of energy.You don't. Cubic meters is a measure of volume; joules or gigajoules is a measure of energy.You don't. Cubic meters is a measure of volume; joules or gigajoules is a measure of energy.
1 gigajoule = 1000 megajoules. 1 megajoule = 1000 kilojoules. So 950 gigajoules = 950 x 106 kilojoules
21-22 gigajoules per ton
No, a megajoule is equal to 0.001 gigajoules. Alternately, a gigajoule equals 1,000 megajoules.
No, you can't just forget about amps. A Joule is a volt coulomb. To calculate coulombs you need amps
The "watt" ... (and also the milliwatt, Kilowatt, Megawatt, Gigawatt) ... are rates or speedsof producing or using energy.One Watt means 1 joule of energy per second.2000 MegaWatts means 2000 Megajoules of energy per second.That's the rate or speed at which it produces energy. Continuously.If it runs for 1 hour at 2000 MW, it produces 7,200 Gigajoules of energy.If it runs for 1 day at 2000MW, it produces 172,800 Gigajoules of energy.and so on.
A kiloton is a unit of measure which measures the energy of an atomic weapon's explosive power.One kiloton is equal to 1000 tons or 4.184 gigajoules.A kilotonne is a unit of weight (mass) measurement, equal to 1000 kilograms or 2,240 pounds UK (1.016 kg) or 2000 pounds US/CA (907 kg).
The bomb did not have tnt. The atomic power is measurred using tnt was the base. TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT, and a bomb with one kiloton has the blast compared to one ton of tnt.
Sorry, don't understand "arc reactor" OK i guess we are talking about the fictional character "tony stark" from iron man. the miniaturised reactor he builds to escape the terrorists gives out 3 gigajoules and the 2nd miniaturised reactor he builds to power his mark 2 armour (the silver one, the one that Obadiah takes) gives out 12
First off you would need to know the energy value of the oil, that is the amount of energy released during the combustion of a specified amount of the oil, eg kj/mol. The energy value for paraffin is around 46Mj/kg. 46 megajoules per kilogram, or 46million joules. One tonne is one thousand kilograms, so one tonne of paraffin would contain 46 thousand megajoules, or 46 gigajoules (46Gj).
The chemical energy in the fuel flows to the engines, which combine the carbon and hydrogen in the fuel with oxygen from the air, to produce heat, carbon dioxide and steam. The heat produces kinetic energy in the hot exhaust gases which leave the engine at high speed. The reaction drives the plane forward and it accelerates, gathering kinetic energy. After takeoff the aircraft rises and gathers potential energy as well as kinetic energy. A Boeing 737-800 with a mass of 85 tons flying at 35,000 ft has a potential energy of 9 Gigajoules. Flying at 400 kt its kinetic energy is 1.8 Gj.
First, a kilowatt is a power unit equal to 1000 Joules per second. Raising water temperature, without specifying a timeframe is a question of how much energy is needed. You need to specify how fast you want to raise the temperature to get power kW. A tonne is 1000 kilograms, which is 10^6 grams, so 480 tonnes is 4.8 x 10^8 grams. It takes 1 calorie to raise a gram of water by 1Â°C, so it takes 10 x (4.8 x 10^8) calories = 4.8 x 10^9 calories. Taking 1 calorie = 4.1868 joules, we have 2.009664 x 10^10 joules, or 20.09664 gigajoules.
If Jupiter hit the sun, there would be phenomenal release of energy. The energy is equivalent to 1/2 mv2 so since the mass of Jupiter is 1.89x1027 kg and the escape velocity of the sun (and thus the approximate speed of impact) is 617 km/s (6.17x105 m/s). Thus, the energy released would be 3.60x1038 J. At that speed, the collision would take about 4 minutes from the moment of the first contact to the moment all of Jupiter is at the surface of the sun. This would be around 1.5e36 W on average, or about 4 billiontimes brighter than the sun normally is. On Earth, areas in direct sunlight would receive 20 petajoules/m2 over that time period. By comparison, a 1 megaton nuclear bomb at 10 m (across the room) only releases 3.3 gigajoules/m2, less than 1/1000 of what this event would generate. Needless to say, nobody on the day side of Earth would survive, and the blast wave and earthquake would kill everyone on the night side.As for the sun itself, it would brighten considerably for a few years before returning to normal.
Since three factors affect muscular strength simultaneously and muscles never work individually, it is misleading to compare strength in individual muscles, and state that one is the "strongest". But below are several muscles whose strength is noteworthy for different reasons.In ordinary parlance, muscular "strength" usually refers to the ability to exert a force on an external object-for example, lifting a weight. By this definition, the masseter or jaw muscle is the strongest. The 1992 Guinness Book of Records records the achievement of a bite strength of 4,337 N (975 lbf) for 2 seconds. What distinguishes the masseter is not anything special about the muscle itself, but its advantage in working against a much shorter lever arm than other muscles.If "strength" refers to the force exerted by the muscle itself, e.g., on the place where it inserts into a bone, then the strongest muscles are those with the largest cross-sectional area. This is because the tension exerted by an individual skeletal muscle fiber does not vary much. Each fiber can exert a force on the order of 0.3 micronewton. By this definition, the strongest muscle of the body is usually said to be the quadriceps femoris or the gluteus maximus.A shorter muscle will be stronger "pound for pound" (i.e., by weight) than a longer muscle. The myometrial layer of the uterus may be the strongest muscle by weight in the female human body. At the time when an infant is delivered, the entire human uterus weighs about 1.1 kg (40 oz). During childbirth, the uterus exerts 100 to 400 N (25 to 100 lbf) of downward force with each contraction.The external muscles of the eye are conspicuously large and strong in relation to the small size and weight of the eyeball. It is frequently said that they are "the strongest muscles for the job they have to do" and are sometimes claimed to be "100 times stronger than they need to be." However, eye movements (particularly saccades used on facial scanning and reading) do require high speed movements, and eye muscles are exercised nightly during rapid eye movement sleep.The statement that "the tongue is the strongest muscle in the body" appears frequently in lists of surprising facts, but it is difficult to find any definition of "strength" that would make this statement true. Note that the tongue consists of eight muscles, not one.The heart has a claim to being the muscle that performs the largest quantity of physical work in the course of a lifetime. Estimates of the power output of the human heart range from 1 to 5 watts. This is much less than the maximum power output of other muscles; for example, the quadriceps can produce over 100 watts, but only for a few minutes. The heart does its work continuously over an entire lifetime without pause, and thus does "outwork" other muscles. An output of one watt continuously for eighty years yields a total work output of two and a half gigajoules.
Nuclear fusion is the process of joining two atomic nuclei (two sets of protons and neutrons) together. If the nuclei are smaller than iron or nickel nuclei, there is a net release of energy (more energy comes out of the new nucleus than was used to make it). If the nuclei are larger than that, there is a net loss of energy (it takes more energy to combine the nuclei than you get back out). Nuclear fusion is the process that powers stars and is what allows them to resist their own enormous gravity - they exist in a precarious equilibrium between being crushed and blowing themselves apart. In small stars like the sun the elements being fused are hydrogen isotopes, sometimes using carbon, nitrogen and oxygen as catalysts. The end product is helium and several other sub-atomic particles. Larger stars can fuse heavier elements - up to iron and nickel. Once the star has an iron core, fusion stops and the star collapses under its own weight. The outer layers bounce off the core and destroy the star in a supernova. In these events temperatures and pressures rise high enough for all the remaining heavy elements to be produced. Nuclear fusion on earth is achievable and several experimental reactors have produced power from fusion of hydrogen isotopes. Most notably, JET (Joint European Torus) in Oxfordshire, England, produced a world record of 16MW of fusion power for (I believe) six seconds. Currently being built, ITER in southern France has been designed to produce 500MW of power for 50MW input. Assembly of the reactor buildings is due to start in 2015 and the first plasma is due in 2019. If it is successful, a follow-up plant called DEMO will attempt to commercialise fusion power. Fusion is regarded as a cleaner source of energy than either fossil fuels (since there are no CO2 emissions) or conventional nuclear fission (no long-lived highly radioactive waste) but is not without problems. Foremost amongst those is the fact that even though the only waste product is helium gas, the reactor walls are badly damaged by the fast neutrons produced in the reaction and will need replacement every so often. The walls will become 'activated' by the neutron bombardement and will themselves need to be treated as radioactive waste. Fusion power as currently envisaged has another advantage - the fuels can be 'bred' within the reactor and extracted from seawater. Furthermore, since fusion is a nuclear process rather than chemical, the energy output per gram of fuel is orders of magnitude greater: one deuterium nucleus and one tritium nucleus together mass just 8.35x10^-27kg and produce 17.6MeV of energy. That means a total of 8.35kg of fuel will produce 2.8x10^15J or 2.8 million gigajoules of energy. In contrast, the same mass of oil would only produce 390 megajoules of energy (1 GJ = 1000 MJ). I recommend google and wikipedia for more information. Many of the pages are quite good as well as accessible. Konrad Harradine
In theory sending physical objects through time would work in one of several ways. 1) Deconstruct object at time period B, and send via a micro wormhole to time period A, then locate it at B and retrieve pictures or send back through the same wormhole via laser beam, etc. This works in the same way as a 3-D printer, with the exception that the object would materialise by reorganising existing atoms. Problem here is that (a) EVERY type of atom including the rare earths needs to be present in the immediate area at the Rx site or it won't work , and (b) the energy needed would be massive, not quite as bad as E=MC2 but still in the order of tens to hundreds of gigajoules per gram of mass. A variant of this method was used on "Timeline" by Michael Crichton. 2) Send the object whole through a wormhole. Needless to say even if the camera was fully solid state the eddy currents induced by the enormous magnetic and gravitational fields would toast the semiconductors and probably turn the lenses into powdered glass. (anyone ever seen a Lichtenberg figure?) Forget about shielding, this wouldn't help unless the shield blocked electromagnetic waves entirely which is very difficult and uses a lot of energy. See superconductor Meissner effect... Jc is low even for YBa2Cu3O6.5 at 77K. The wormhole itself would need exotic matter to hold it open, which is theorised to exist but has never been seen (yet!) although CERN are hoping to see some very shortly. Also this method would be subject to E=MC2 so 1 gram of mass = around 50 megatons nuclear energy equivalent. This method was used on "Back to the Future", "Star Trek" (2009), etc. 3) Send back the information only via high frequency evanescent radio waves through a wormhole. This would work by having someone in the past build the camera from instructions sent through time. The method is theoretically possible in much the same way as we can now build 3-D objects from plastics, liquid polymers etc. One way might be to exploit the (relatively simple) storage technique of excited quantum states in zinc sulphide disks which were known about in the early 1920's but at the time other methods such as mercury delay lines became commonplace instead due to the ease of manufacture. The information could be stored for a relatively long time if continuously rewritten, the last time I checked solid state SiC based green light emitters were made in 1922 and were noted then for their longevity. The only equipment needed would be a robust brushless motor which could be made using bismuth filled capillary tubes as the sensors and conventional magnets and coils (albeit very inefficient!) as well as an imaging device made from a Nipkow disk and sensor. Again, theoretically possible but would need a genius at the other end to assemble the device and make it reliable enough to survive nearly a century of buffering. A variant of this method was seen on "Frequency". Method 3) is more likely :-) Now for the nasty part, generating the wormhole. We believe that to generate one would require an energy in the collisions of between 6 and 200 TeV, but due to quantum effects it would be incredibly short lived, in the order of attoseconds. In order to keep one stable for any length of time it would need to be decelerated to a few cm per second, while bombarding it with radiation to prevent it from closing. Once stabilised, the signal would need to be sent through in such a way that quantum effects would not scramble the signal, so sending it multiple times would be needed. Current theories suggest that this might be possible... does this help?
Muscle (from Latin musculus, diminutive of mus "mouse") is the contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause either locomotion of the organism itself or movement of internal organs. Cardiac and smooth muscle contraction occurs without conscious thought and is necessary for survival. Examples are the contraction of the heart and peristalsis which pushes food through the digestive system. Voluntary contraction of the skeletal muscles is used to move the body and can be finely controlled. Examples are movements of the eye, or gross movements like the quadriceps muscle of the thigh. There are two broad types of voluntary muscle fibers: slow twitch and fast twitch. Slow twitch fibers contract for long periods of time but with little force while fast twitch fibers contract quickly and powerfully but fatigue very rapidly.Contents[hide] 1 Types2 Anatomy 2.1 Gross anatomy2.2 Microanatomy3 Physiology4 Nervous control 4.1 Efferent leg4.2 Afferent leg5 Exercise6 Disease 6.1 Atrophy 6.1.1 Physical inactivity and atrophy7 Strength 7.1 The "strongest" human muscle8 Efficiency9 Density of muscle tissue compared to adipose tissue10 Muscle evolution11 See also12 Footnotes13 References14 External links// TypesTypes of muscle There are three types of muscle:Skeletal muscle or "voluntary muscle" is anchored by tendons to bone and is used to effect skeletal movement such as locomotion and in maintaining posture. Though this postural control is generally maintained as a subconscious reflex, the muscles responsible react to conscious control like non-postural muscles. An average adult male is made up of 42% of skeletal muscle and an average adult female is made up of 36% (as a percentage of body mass). Smooth muscle or "involuntary muscle" is found within the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and the arrector pili in the skin (in which it controls erection of body hair). Unlike skeletal muscle, smooth muscle is not under conscious control.Cardiac muscle is also an "involuntary muscle" but is more akin in structure to skeletal muscle, and is found only in the heart.Cardiac and skeletal muscles are "striated" in that they contain sarcomeres and are packed into highly-regular arrangements of bundles; smooth muscle has neither. While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles (called intercalated discs). Striated muscle contracts and relaxes in short, intense bursts, whereas smooth muscle sustains longer or even near-permanent contractions.Skeletal muscle is further divided into several subtypes:Type I, slow oxidative, slow twitch, or "red" muscle is dense with capillaries and is rich in mitochondria and myoglobin, giving the muscle tissue its characteristic red color. It can carry more oxygen and sustain aerobic activity.Type II, fast twitch muscle, has three major kinds that are, in order of increasing contractile speed: Type IIa, which, like slow muscle, is aerobic, rich in mitochondria and capillaries and appears red.Type IIx (also known as type IId), which is less dense in mitochondria and myoglobin. This is the fastest muscle type in humans. It can contract more quickly and with a greater amount of force than oxidative muscle, but can sustain only short, anaerobic bursts of activity before muscle contraction becomes painful (often incorrectly attributed to a build-up of lactic acid). N.B. in some books and articles this muscle in humans was, confusingly, called type IIB.Type IIb, which is anaerobic, glycolytic, "white" muscle that is even less dense in mitochondria and myoglobin. In small animals like rodents this is the major fast muscle type, explaining the pale color of their flesh.AnatomyThe anatomy of muscles includes both gross anatomy, comprising all the muscles of an organism, and, on the other hand, microanatomy, which comprises the structures of a single muscle.Gross anatomyMuscles, anterior view (See Gray's muscle pictures for detailed pictures)Muscles, posterior view (See Gray's muscle pictures for detailed pictures)The gross anatomy of a muscle is the most important indicator of its role in the body. The action a muscle generates is determined by the origin and insertion locations. The cross-sectional area of a muscle (rather than volume or length) determines the amount of force it can generate by defining the number of sarcomeres which can operate in parallel. The amount of force applied to the external environment is determined by lever mechanics, specifically the ratio of in-lever to out-lever. For example, moving the insertion point of the biceps more distally on the radius (farther from the joint of rotation) would increase the force generated during flexion (and, as a result, the maximum weight lifted in this movement), but decrease the maximum speed of flexion. Moving the insertion point proximally (closer to the joint of rotation) would result in decreased force but increased velocity. This can be most easily seen by comparing the limb of a mole to a horse - in the former, the insertion point is positioned to maximize force (for digging), while in the latter, the insertion point is positioned to maximize speed (for running).One particularly important aspect of gross anatomy of muscles is pennation or lack thereof. In most muscles, all the fibers are oriented in the same direction, running in a line from the origin to the insertion. In pennate muscles, the individual fibers are oriented at an angle relative to the line of action, attaching to the origin and insertion tendons at each end. Because the contracting fibers are pulling at an angle to the overall action of the muscle, the change in length is smaller, but this same orientation allows for more fibers (thus more force) in a muscle of a given size. Pennate muscles are usually found where their length change is less important than maximum force, such as the rectus femoris.There are approximately 639 skeletal muscles in the human body. However, the exact number is difficult to define because different sources group muscles differently.Main article: Table of muscles of the human body MicroanatomyMuscle is mainly composed of muscle cells. Within the cells are myofibrils; myofibrils contain sarcomeres, which are composed of actin and myosin. Individual muscle fibres are surrounded by endomysium. Muscle fibers are bound together by perimysium into bundles called fascicles; the bundles are then grouped together to form muscle, which is enclosed in a sheath of epimysium. Muscle spindles are distributed throughout the muscles and provide sensory feedback information to the central nervous system.Skeletal muscle is arranged in discrete muscles, an example of which is the biceps brachii. It is connected by tendons to processes of the skeleton. Cardiac muscle is similar to skeletal muscle in both composition and action, being comprised of myofibrils of sarcomeres, but anatomically different in that the muscle fibers are typically branched like a tree and connect to other cardiac muscle fibers through intercalcated discs, and form the appearance of a syncytium.PhysiologyMain article: muscle contraction The three types of muscle (skeletal, cardiac and smooth) have significant differences. However, all three use the movement of actin against myosin to create contraction. In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the nerves, the motor nerves and motoneurons in particular. Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with. All skeletal muscle and many smooth muscle contractions are facilitated by the neurotransmitter acetylcholine.Muscular activity accounts for much of the body's energy consumption. All muscle cells produce adenosine triphosphate (ATP) molecules which are used to power the movement of the myosin heads. Muscles conserve energy in the form of creatine phosphate which is generated from ATP and can regenerate ATP when needed with creatine kinase. Muscles also keep a storage form of glucose in the form of glycogen. Glycogen can be rapidly converted to glucose when energy is required for sustained, powerful contractions. Within the voluntary skeletal muscles, the glucose molecule can be metabolized anaerobically in a process called glycolysis which produces two ATP and two lactic acid molecules in the process (note that in aerobic conditions, lactate is not formed; instead pyruvate is formed and transmitted through the citric acid cycle). Muscle cells also contain globules of fat, which are used for energy during aerobic exercise. The aerobic energy systems take longer to produce the ATP and reach peak efficiency, and requires many more biochemical steps, but produces significantly more ATP than anaerobic glycolysis. Cardiac muscle on the other hand, can readily consume any of the three macronutrients (protein, glucose and fat) aerobically without a 'warm up' period and always extracts the maximum ATP yield from any molecule involved. The heart, liver and red blood cells will also consume lactic acid produced and excreted by skeletal muscles during exercise.Nervous controlMind Map showing a summary of Upper Limb Muscle InnervationMind Map showing a summary of Lower Limb Muscle innervation Efferent legThe efferent leg of the peripheral nervous system is responsible for conveying commands to the muscles and glands, and is ultimately responsible for voluntary movement. Nerves move muscles in response to voluntary and autonomic (involuntary) signals from the brain. Deep muscles, superficial muscles, muscles of the face and internal muscles all correspond with dedicated regions in the primary motor cortex of the brain, directly anterior to the central sulcus that divides the frontal and parietal lobes.In addition, muscles react to reflexive nerve stimuli that do not always send signals all the way to the brain. In this case, the signal from the afferent fiber does not reach the brain, but produces the reflexive movement by direct connections with the efferent nerves in the spine. However, the majority of muscle activity is volitional, and the result of complex interactions between various areas of the brain.Nerves that control skeletal muscles in mammals correspond with neuron groups along the primary motor cortex of the brain's cerebral cortex. Commands are routed though the basal ganglia and are modified by input from the cerebellum before being relayed through the pyramidal tract to the spinal cord and from there to the motor end plate at the muscles. Along the way, feedback, such as that of the extrapyramidal system contribute signals to influence muscle tone and response.Deeper muscles such as those involved in posture often are controlled from nuclei in the brain stem and basal ganglia.Afferent legThe afferent leg of the peripheral nervous system is responsible for conveying sensory information to the brain, primarily from the sense organs like the skin. In the muscles, the muscle spindles convey information about the degree of muscle length and stretch to the central nervous system to assist in maintaining posture and joint position. The sense of where our bodies are in space is called proprioception, the perception of body awareness. More easily demonstrated than explained, proprioception is the "unconscious" awareness of where the various regions of the body are located at any one time. This can be demonstrated by anyone closing their eyes and waving their hand around. Assuming proper proprioceptive function, at no time will the person lose awareness of where the hand actually is, even though it is not being detected by any of the other senses.Several areas in the brain coordinate movement and position with the feedback information gained from proprioception. The cerebellum and red nucleus in particular continuously sample position against movement and make minor corrections to assure smooth motion.ExerciseExercise is often recommended as a means of improving motor skills, fitness, muscle and bone strength, and joint function. Exercise has several effects upon muscles, connective tissue, bone, and the nerves that stimulate the muscles.Various exercises require a predominance of certain muscle fiber utilization over another. Aerobic exercise involves long, low levels of exertion in which the muscles are used at well below their maximal contraction strength for long periods of time (the most classic example being the marathon). Aerobic events, which rely primarily on the aerobic (with oxygen) system, use a higher percentage of Type I (or slow-twitch) muscle fibers, consume a mixture of fat, protein and carbohydrates for energy, consume large amounts of oxygen and produce little lactic acid. Anaerobic exercise involves short bursts of higher intensity contractions at a much greater percentage of their maximum contraction strength. Examples of anaerobic exercise include sprinting and weight lifting. The anaerobic energy delivery system uses predominantly Type II or fast-twitch muscle fibers, relies mainly on ATP or glucose for fuel, consumes relatively little oxygen, protein and fat, produces large amounts of lactic acid and can not be sustained for as long a period as aerobic exercise. The presence of lactic acid has an inhibitory effect on ATP generation within the muscle; though not producing fatigue, it can inhibit or even stop performance if the intracellular concentration becomes too high. However, long-term training causes neovascularization within the muscle, increasing the ability to move waste products out of the muscles and maintain contraction. Once moved out of muscles with high concentrations within the sarcomere, lactic acid can be used by other muscles or body tissues as a source of energy, or transported to the liver where it is converted back to pyruvate. The ability of the body to export lactic acid and use it as a source of energy depends on training level.Humans are genetically predisposed with a larger percentage of one type of muscle group over another. An individual born with a greater percentage of Type I muscle fibers would theoretically be more suited to endurance events, such as triathlons, distance running, and long cycling events, whereas a human born with a greater percentage of Type II muscle fibers would be more likely to excel at anaerobic events such as a 200 meter dash, or weightlifting.Delayed onset muscle soreness is pain or discomfort that may be felt one to three days after exercising and subsides generally within two to three days later. Once thought to be caused by lactic acid buildup, a more recent theory is that it is caused by tiny tears in the muscle fibers caused by eccentric contraction, or unaccustomed training levels. Since lactic acid disperses fairly rapidly, it could not explain pain experienced days after exercise.Muscular, spinal and neural factors all affect muscle building. Sometimes a person may notice an increase in strength in a given muscle even though only its opposite has been subject to exercise, such as when a bodybuilder finds her left biceps stronger after completing a regimen focusing only on the right biceps. This phenomenon is called cross education.DiseaseMain article: Neuromuscular disease Symptoms of muscle diseases may include weakness, spasticity, myoclonus and myalgia. Diagnostic procedures that may reveal muscular disorders include testing creatine kinase levels in the blood and electromyography (measuring electrical activity in muscles). In some cases, muscle biopsy may be done to identify a myopathy, as well as genetic testing to identify DNA abnormalities associated with specific myopathies and dystrophies.Neuromuscular diseases are those that affect the muscles and/or their nervous control. In general, problems with nervous control can cause spasticity or paralysis, depending on the location and nature of the problem. A large proportion of neurological disorders leads to problems with movement, ranging from cerebrovascular accident (stroke) and Parkinson's disease to Creutzfeldt-Jakob disease.A non-invasive elastography technique that measures muscle noise is undergoing experimentation to provide a way of monitoring neuromuscular disease. The sound produced by a muscle comes from the shortening of actomyosin filaments along the axis of the muscle. During contraction, the muscle shortens along its longitudinal axis and expands across the transverse axis, producing vibrations at the surface.AtrophyThere are many diseases and conditions which cause a decrease in muscle mass, known as muscle atrophy. Examples include cancer and AIDS, which induce a body wasting syndrome called cachexia. Other syndromes or conditions which can induce skeletal muscle atrophy are congestive heart disease and some diseases of the liver.During aging, there is a gradual decrease in the ability to maintain skeletal muscle function and mass, known as sarcopenia. The exact cause of sarcopenia is unknown, but it may be due to a combination of the gradual failure in the "satellite cells" which help to regenerate skeletal muscle fibers, and a decrease in sensitivity to or the availability of critical secreted growth factors which are necessary to maintain muscle mass and satellite cell survival. Sarcopenia is a normal aspect of aging, and is not actually a disease state yet can be linked to many injuries in the elderly population as well as decreasing quality of life.Physical inactivity and atrophyInactivity and starvation in mammals lead to atrophy of skeletal muscle, accompanied by a smaller number and size of the muscle cells as well as lower protein content. In humans, prolonged periods of immobilization, as in the cases of bed rest or astronauts flying in space, are known to result in muscle weakening and atrophy. Such consequences are also noted in small hibernating mammals like the golden-mantled ground squirrels and brown bats. Representatives of the Ursid species make for an interesting exception to this expected norm.Bears are famous for their ability to survive unfavorable environmental conditions of low temperatures and limited nutrition availability during winter by means of hibernation. During that time Ursids go through a series of physiological, morphological and behavioral changes. Their ability to maintain skeletal muscle number and size at time of disuse is of a significant importance. During hibernation bears spend four to seven months of inactivity and anorexia without undergoing muscle atrophy and protein loss. There are a few known factors that contribute to the sustaining of muscle tissue. During the summer period, Ursids take advantage of the nutrition availability and accumulate muscle protein. The protein balance of bears at time of dormancy is also maintained by lower levels of protein breakdown during the winter time. At times of immobility, muscle wasting in Ursids is also suppressed by a proteolytic inhibitor that is released in circulation. Another factor that contributes to the sustaining of muscle strength in hibernating bears is the occurrence of periodic voluntary contractions and involuntary contractions from shivering during torpor. The three to four daily episodes of muscle activity are responsible for the maintenance of muscle strength and responsiveness in bears during hibernation.StrengthA display of "strength" (e.g. lifting a weight) is a result of three factors that overlap: physiological strength (muscle size, cross sectional area, available crossbridging, responses to training), neurological strength (how strong or weak is the signal that tells the muscle to contract), and mechanical strength (muscle's force angle on the lever, moment arm length, joint capabilities). Contrary to popular belief, the number of muscle fibres cannot be increased through exercise; instead the muscle cells simply get bigger. Muscle fibres have a limited capacity for growth through hypertrophy and some believe they split through hyperplasia if subject to increased demand.The "strongest" human muscleSince three factors affect muscular strength simultaneously and muscles never work individually, it is misleading to compare strength in individual muscles, and state that one is the "strongest". But below are several muscles whose strength is noteworthy for different reasons.In ordinary parlance, muscular "strength" usually refers to the ability to exert a force on an external object-for example, lifting a weight. By this definition, the masseter or jaw muscle is the strongest. The 1992 Guinness Book of Records records the achievement of a bite strength of 4,337 N (975 lbf) for 2 seconds. What distinguishes the masseter is not anything special about the muscle itself, but its advantage in working against a much shorter lever arm than other muscles.If "strength" refers to the force exerted by the muscle itself, e.g., on the place where it inserts into a bone, then the strongest muscles are those with the largest cross-sectional area. This is because the tension exerted by an individual skeletal muscle fiber does not vary much. Each fiber can exert a force on the order of 0.3 micronewton. By this definition, the strongest muscle of the body is usually said to be the quadriceps femoris or the gluteus maximus.A shorter muscle will be stronger "pound for pound" (i.e., by weight) than a longer muscle. The myometrial layer of the uterus may be the strongest muscle by weight in the human body. At the time when an infant is delivered, the entire human uterus weighs about 1.1 kg (40 oz). During childbirth, the uterus exerts 100 to 400 N (25 to 100 lbf) of downward force with each contraction.The external muscles of the eye are conspicuously large and strong in relation to the small size and weight of the eyeball. It is frequently said that they are "the strongest muscles for the job they have to do" and are sometimes claimed to be "100 times stronger than they need to be." However, eye movements (particularly saccades used on facial scanning and reading) do require high speed movements, and eye muscles are exercised nightly during rapid eye movement sleep.The statement that "the tongue is the strongest muscle in the body" appears frequently in lists of surprising facts, but it is difficult to find any definition of "strength" that would make this statement true. Note that the tongue consists of sixteen muscles, not one.The heart has a claim to being the muscle that performs the largest quantity of physical work in the course of a lifetime. Estimates of the power output of the human heart range from 1 to 5 watts. This is much less than the maximum power output of other muscles; for example, the quadriceps can produce over 100 watts, but only for a few minutes. The heart does its work continuously over an entire lifetime without pause, and thus does "outwork" other muscles. An output of one watt continuously for eighty years yields a total work output of two and a half gigajoules.EfficiencyThe efficiency of human muscle has been measured (in the context of rowing and cycling) at 18% to 26%. The efficiency is defined as the ratio of mechanical work output to the total metabolic cost, as can be calculated from oxygen consumption. This low efficiency is the result of about 40% effiency of generating ATP from food energy, losses in converting energy from ATP into mechanical work inside the muscle, and mechanical losses inside the body. The latter two losses are dependent on the type of exercise and the type of muscle fibers being used (fast-twitch or slow-twitch). For an overal efficiency of 20 percent, one watt of mechanical power is equivalent to 4.3 kcal per hour. For example, a manufacturer of rowing equipment shows burned calories as four times the actual mechanical work, plus 300 kcal per hour, which amounts to about 20 percent efficiency at 250 watts of mechanical output.Density of muscle tissue compared to adipose tissueThe density of mammalian skeletal muscle tissue is about 1.06 kg/liter. This can be contrasted with the density of adipose tissue (fat), which is 0.9196 kg/liter. This makes muscle tissue approximately 15% denser than fat tissue.Muscle evolutionEvolutionarily, specialized forms of skeletal and cardiac muscles predated the divergence of the vertebrate/arthropod evolutionary line. This indicates that these types of muscle developed in a common ancestor sometime before 700 million years ago (mya). Vertebrate smooth muscle was found to have evolved independently from the skeletal and cardiac muscles.See alsoLook up muscle in Wiktionary, the free dictionary. Wikimedia Commons has media related to: musclesAtrophyBodybuildingCross educationElectroactive polymers (materials that behave like muscles, used in robotics research)FasciaHand strengthList of muscles of the human bodyMuscle atrophyMuscle memoryMuscle tone (residual muscle tension)Musculoskeletal systemMyopathy (pathology of muscle cells)MyotomyPhonomyographyPreflexesRapid plant movementRohmert's law
Renewable energy is energy generated from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable (naturally replenished). In 2006, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood-burning and 3% from hydroelectricity. New renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels) accounted for 2.4% and are growing very rapidly. The share of renewables in electricity generation is around 18%, with 15% of global electricity coming from hydroelectricity and 3.4% from new renewables.Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 121,000 megawatts (MW) in 2008, and is widely used in European countries and the United States. The annual manufacturing output of the photovoltaics industry reached 6,900 MW in 2008, and photovoltaic (PV) power stations are popular in Germany and Spain. Solar thermal power stations operate in the USA and Spain, and the largest of these is the 354 MW SEGS power plant in the Mojave Desert. The world's largest geothermal power installation is The Geysers in California, with a rated capacity of 750 MW. Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18% of the country's automotive fuel. Ethanol fuel is also widely available in the USA.While most renewable energy projects and production is large-scale, renewable technologies are also suited to small off-grid applications, sometimes in rural and remote areas, where energy is often crucial in human development. Kenya has the world's highest household solar ownership rate with roughly 30,000 small (20-100 watt) solar power systems sold per year.Some renewable energy technologies are criticized for being intermittent or unsightly, yet the renewable energy market continues to grow. Climate change concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization. New government spending, regulation and policies helped the industry weather the 2009 economic crisis better than many other sectors.Contents[hide] 1 Main forms/sources of renewable energy 1.1 Wind power1.2 Hydropower1.3 Solar energy1.4 Biofuel 1.4.1 Liquid biofuel1.4.2 Solid biomass1.4.3 Biogas1.5 Geothermal energy2 Renewable energy commercialization 2.1 Economics2.2 Growth of renewables2.3 Wind power market2.4 New generation of solar thermal plants2.5 World's largest photovoltaic power plants2.6 Use of ethanol for transportation2.7 Geothermal energy prospects2.8 Wave farms expansion2.9 Developing country markets2.10 Industry and policy trends3 Constraints and opportunities 3.1 Availability and reliability3.2 Aesthetics3.3 Environmental, social and legal considerations 3.3.1 Land area required3.3.2 Hydroelectricity3.3.3 Wind farms3.4 Longevity issues3.5 Biofuels production3.6 Diversification3.7 Competition with nuclear power4 See also5 References6 External linksMain forms/sources of renewable energyThree energy sources 2008 worldwide renewable-energy sources. Source: REN21The majority of renewable energy technologies are powered by the sun. The Earth-Atmosphere system is in equilibrium such that heat radiation into space is equal to incoming solar radiation, the resulting level of energy within the Earth-Atmosphere system can roughly be described as the Earth's "climate." The hydrosphere (water) absorbs a major fraction of the incoming radiation. Most radiation is absorbed at low latitudes around the equator, but this energy is dissipated around the globe in the form of winds and ocean currents. Wave motion may play a role in the process of transferring mechanical energy between the atmosphere and the ocean through wind stress. Solar energy is also responsible for the distribution of precipitation which is tapped by hydroelectric projects, and for the growth of plants used to create biofuels.Renewable energy flows involve natural phenomena such as sunlight, wind, tides and geothermal heat, as the International Energy Agency explains:Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.Each of these sources has unique characteristics which influence how and where they are used.Wind powerSee also: Wind power, Wind energy conversion system, List of onshore wind farms, and List of offshore wind farms Vestas V80 wind turbines Airflows can be used to run wind turbines. Modern wind turbines range from around 600 kW to 5 MW of rated power, although turbines with rated output of 1.5-3 MW have become the most common for commercial use; the power output of a turbine is a function of the cube of the wind speed, so as wind speed increases, power output increases dramatically. Areas where winds are stronger and more constant, such as offshore and high altitude sites, are preferred locations for wind farms. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favourable sites.Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand. This could require large amounts of land to be used for wind turbines, particularly in areas of higher wind resources. Offshore resources experience mean wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy. This number could also increase with higher altitude ground-based or airborne wind turbines.Wind power is renewable and produces no greenhouse gases during operation, such as carbon dioxide and methane.HydropowerSee also: Hydroelectricity and Hydropower Energy in water (in the form of kinetic energy, temperature differences or salinity gradients) can be harnessed and used. Since water is about 800 times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts of energy. One of 3 Pelamis Wave Energy Converters in the harbor of Peniche, PortugalThere are many forms of water energy:Hydroelectric energy is a term usually reserved for large-scale hydroelectric dams. Examples are the Grand Coulee Dam in Washington State and the Akosombo Dam in Ghana.Micro hydro systems are hydroelectric power installations that typically produce up to 100 kW of power. They are often used in water rich areas as a Remote Area Power Supply (RAPS). There are many of these installations around the world, including several delivering around 50 kW in the Solomon Islands.Damless hydro systems derive kinetic energy from rivers and oceans without using a dam.Ocean energy describes all the technologies to harness energy from the ocean and the sea: Marine current power. Similar to tidal stream power, uses the kinetic energy of marine currentsOcean thermal energy conversion (OTEC) uses the temperature difference between the warmer surface of the ocean and the colder lower recesses. To this end, it employs a cyclic heat engine. OTEC has not been field-tested on a large scale.Tidal power captures energy from the tides.Wave power uses the energy in waves. Wave power machines usually take the form of floating or neutrally buoyant structures which move relative to one another or to a fixed point.Osmotic power or salinity gradient power, is the energy retrieved from the difference in the salt concentration between seawater and river water. Reverse electrodialysis (PRO) is in the research and testing phase.Vortex power is generated by placing obstacles in rivers in order to cause the formation of vortices which can then be tapped for energy.Solar energySee also: Solar energy, Solar power, and Solar thermal energy Monocrystalline solar cell In this context, "solar energy" refers to energy that is collected from sunlight. Solar energy can be applied in many ways, including to:Generate electricity using photovoltaic solar cells.Generate electricity using concentrating solar power.Generate electricity by heating trapped air which rotates turbines in a Solar updraft tower.Generate hydrogen using photoelectrochemical cells.Heat water or air for domestic hot water and space heating needs using solar-thermal panels.Heat buildings, directly, through passive solar building design.Heat foodstuffs, through solar ovens.Solar air conditioningBiofuelMain article: Biofuel Plants use photosynthesis to grow and produce biomass. Also known as biomatter, biomass can be used directly as fuel or to produce biofuels. Agriculturally produced biomass fuels, such as biodiesel, ethanol and bagasse (often a by-product of sugar cane cultivation) can be burned in internal combustion engines or boilers. Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work.Liquid biofuelInformation on pump, California. Liquid biofuel is usually either a bioalcohol such as ethanol fuel or an oil such as biodiesel or straight vegetable oil. Biodiesel can be used in modern diesel vehicles with little or no modification to the engine. It can be made from waste and virgin vegetable and animal oils and fats (lipids). Virgin vegetable oils can be used in modified diesel engines. In fact the diesel engine was originally designed to run on vegetable oil rather than fossil fuel. A major benefit of biodiesel use is the reduction in net CO2 emissions, since all the carbon emitted was recently captured during the growing phase of the biomass. The use of biodiesel also reduces emission of carbon monoxide and other pollutants by 20 to 40%.In some areas corn, cornstalks, sugarbeets, sugar cane, and switchgrasses are grown specifically to produce ethanol (also known as grain alcohol) a liquid which can be used in internal combustion engines and fuel cells. Ethanol is being phased into the current energy infrastructure. E85 is a fuel composed of 85% ethanol and 15% gasoline that is sold to consumers. Biobutanol is being developed as an alternative to bioethanol.Another source of biofuel is sweet sorghum. It produces both food and fuel from the same crop. Some studies have shown that the crop is net energy positive ie. it produces more energy than is consumed in its production and utilization.Solid biomassMain article: BiomassSugar cane residue can be used as a biofuel Solid biomass is most commonly used directly as a combustible fuel, in Biomass Fuelled Power Plants producing 10-20 MJ/kg of heat. Its forms and sources include wood fuel, the biogenic portion of municipal solid waste, or the unused portion of field crops. Field crops may or may not be grown intentionally as an energy crop, and the remaining plant byproduct used as a fuel. Most types of biomass contain energy. Even cow manure still contains two-thirds of the original energy consumed by the cow. Energy harvesting via a bioreactor is a cost-effective solution to the waste disposal issues faced by the dairy farmer, and can produce enough biogas to run a farm.With current technology, it is not ideally suited for use as a transportation fuel. Most transportation vehicles require power sources with high power density, such as that provided by internal combustion engines. These engines generally require clean burning fuels, which are generally in liquid form, and to a lesser extent, compressed gaseous phase. Liquids are more portable because they can have a high energy density, and they can be pumped, which makes handling easier. Solid biomass can however be converted to hydrogen, as the Hyvolution project shows.Non-transportation applications can usually tolerate the low power-density of external combustion engines, that can run directly on less-expensive solid biomass fuel, for combined heat and power. One type of biomass is wood, which has been used for millennia. Two billion people currently cook every day, and heat their homes in the winter by burning biomass, which is a major contributor to man-made climate change global warming. The black soot that is being carried from Asia to polar ice caps is causing them to melt faster in the summer. In the 19th century, wood-fired steam engines were common, contributing significantly to industrial revolution unhealthy air pollution. Coal is a form of biomass that has been compressed over millennia to produce a non-renewable, highly-polluting fossil fuel.Wood and its byproducts can now be converted through processes such as gasification into biofuels such as woodgas, biogas, methanol or ethanol fuel; although further development may be required to make these methods affordable and practical. Sugar cane residue, wheat chaff, corn cobs and other plant matter can be, and are, burned quite successfully. The net carbon dioxide emissions that are added to the atmosphere by this process are only from the fossil fuel that was consumed to plant, fertilize, harvest and transport the biomass.Processes to harvest biomass from short-rotation trees like poplars and willows and perennial grasses such as switchgrass, phalaris, and miscanthus, require less frequent cultivation and less nitrogen than do typical annual crops. Pelletizing miscanthus and burning it to generate electricity is being studied and may be economically viable.BiogasMain articles: Biogas and Anaerobic digestion Biogas can easily be produced from current waste streams, such as paper production, sugar production, sewage, animal waste and so forth. These various waste streams have to be slurried together and allowed to naturally ferment, producing methane gas. This can be done by converting current sewage plants into biogas plants. When a biogas plant has extracted all the methane it can, the remains are sometimes more suitable as fertilizer than the original biomass.Alternatively biogas can be produced via advanced waste processing systems such as mechanical biological treatment. These systems recover the recyclable elements of household waste and process the biodegradable fraction in anaerobic digesters.Renewable natural gas is a biogas which has been upgraded to a quality similar to natural gas. By upgrading the quality to that of natural gas, it becomes possible to distribute the gas to the mass market via the existing gas grid.Geothermal energyMain articles: Geothermal energy and geothermal heat pumpKrafla Geothermal Station in northeast Iceland Geothermal energy is energy obtained by tapping the heat of the earth itself, both from kilometers deep into the Earth's crust in some places of the globe or from some meters in geothermal heat pump in all the places of the planet . It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from heat in the Earth's core.Three types of power plants are used to generate power from geothermal energy: dry steam, flash, and binary. Dry steam plants take steam out of fractures in the ground and use it to directly drive a turbine that spins a generator. Flash plants take hot water, usually at temperatures over 200 °C, out of the ground, and allows it to boil as it rises to the surface then separates the steam phase in steam/water separators and then runs the steam through a turbine. In binary plants, the hot water flows through heat exchangers, boiling an organic fluid that spins the turbine. The condensed steam and remaining geothermal fluid from all three types of plants are injected back into the hot rock to pick up more heat.The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such geothermal power sources exist in certain geologically unstable parts of the world such as Chile, Iceland, New Zealand, United States, the Philippines and Italy. The two most prominent areas for this in the United States are in the Yellowstone basin and in northern California. Iceland produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.There is also the potential to generate geothermal energy from hot dry rocks. Holes at least 3 km deep are drilled into the earth. Some of these holes pump water into the earth, while other holes pump hot water out. The heat resource consists of hot underground radiogenic granite rocks, which heat up when there is enough sediment between the rock and the earths surface. Several companies in Australia are exploring this technology.Renewable energy commercializationMain article: Renewable energy commercialization EconomicsPercentage of renewables in primary energy consumption of EU-member states in 2005. Source: Primärenergieverbrauch und erneuerbare Energien in der EU, Fig 55 When comparing renewable energy sources with each other and with conventional power sources, three main factors must be considered:capital costs (including, for nuclear energy, waste-disposal and decommissioning costs);operating and maintenance costs;fuel costs (for fossil-fuel and biomass sources-for wastes, these costs may actually be negative).These costs are all brought together, using discounted cash flow, here. Inherently, renewables are on a decreasing cost curve, while non-renewables are on an increasing cost curve. In 2009, costs are comparable among wind, nuclear, coal, and natural gas, but for CSP-concentrating solar power-and PV (photovoltaics) they are somewhat higher.There are additional costs for renewables in terms of increased grid interconnection to allow for variability of weather and load, but these have been shown in the pan-European case to be quite low-overall, wind energy costs about the same as present-day power.Growth of renewablesFrom the end of 2004 to the end of 2008, solar photovoltaic (PV) capacity increased sixfold to more than 16 gigawatts (GW), wind power capacity increased 250 percent to 121 GW, and total power capacity from new renewables increased 75 percent to 280 GW. During the same period, solar heating capacity doubled to 145 gigawatts-thermal (GWth), while biodiesel production increased sixfold to 12 billion liters per year and ethanol production doubled to 67 billion liters per year.Selected renewable energy indicatorsSelected global indicators 2006 2007 2008 Investment in new renewable capacity (annual)63104120 billion USDExisting renewables power capacity, including large-scale hydro1,0201,0701,140 GWeExisting renewables power capacity,excluding large hydro207240280 GWeWind power capacity (existing)7494121 GWeBiomass heating~250 GWthSolar hot water/ Space heating145 GWthGeothermal heating~50 GWthEthanol production (annual)395067 billion litersCountries with policy targetsfor renewable energy use6673Wind power marketSee also: Wind farm and List of wind farms Wind power: worldwide installed capacity 1996-2008 At the end of 2008, worldwide wind farm capacity was 120,791 megawatts (MW), representing an increase of 28.8 percent during the year, and wind power produced some 1.3% of global electricity consumption. Wind power accounts for approximately 19% of electricity use in Denmark, 9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland. The United States is an important growth area and installed U.S. wind power capacity reached 25,170 MW at the end of 2008. As of September 2009, the Roscoe Wind Farm (781 MW) is the world's largest wind farm.As of 2009, the 209 megawatt (MW) Horns Rev 2 wind farm in Denmark is the world's largest offshore wind farm. The United Kingdom is the world's leading generator of offshore wind power, followed by Denmark.New generation of solar thermal plantsSolar Towers from left: PS10, PS20. Main article: List of solar thermal power stationsLarge solar thermal power stations include the 354 MW Solar Energy Generating Systems power plant in the USA, Nevada Solar One (USA, 64 MW), Andasol 1 (Spain, 50 MW), Andasol 2 (Spain, 50 MW), PS20 solar power tower (Spain, 20 MW), and the PS10 solar power tower (Spain, 11 MW).The solar thermal power industry is growing rapidly with 1.2 GW under construction as of April 2009 and another 13.9 GW announced globally through 2014. Spain is the epicenter of solar thermal power development with 22 projects for 1,037 MW under construction, all of which are projected to come online by the end of 2010. In the United States, 5,600 MW of solar thermal power projects have been announced. In developing countries, three World Bank projects for integrated solar thermal/combined-cycle gas-turbine power plants in Egypt, Mexico, and Morocco have been approved.World's largest photovoltaic power plantsMain article: List of photovoltaic power stations First Solar 40 MW PV Array installed by JUWI Group in Waldpolenz, Germany As of October 2009, the largest photovoltaic (PV) power plants in the world are the Olmedilla Photovoltaic Park (Spain, 60 MW), the Strasskirchen Solar Park (Germany, 54 MW), the Lieberose Photovoltaic Park (Germany, 53 MW), the Puertollano Photovoltaic Park (Spain, 50 MW), the Moura photovoltaic power station (Portugal, 46 MW), and the Waldpolenz Solar Park (Germany, 40 MW).Many of these plants are integrated with agriculture and some use innovative tracking systems that follow the sun's daily path across the sky to generate more electricity than conventional fixed-mounted systems. There are no fuel costs or emissions during operation of the power stations.Topaz Solar Farm is a proposed 550 MW solar photovoltaic power plant which is to be built northwest of California Valley in the USA at a cost of over $1 billion. Built on 9.5 square miles (25 km2) of ranchland, the project would utilize thin-film PV panels designed and manufactured by OptiSolar in Hayward and Sacramento. The project would deliver approximately 1,100 gigawatt-hours (GW·h) annually of renewable energy. The project is expected to begin construction in 2010, begin power delivery in 2011, and be fully operational by 2013.High Plains Ranch is a proposed 250 MW solar photovoltaic power plant which is to be built by SunPower in the Carrizo Plain, northwest of California Valley.However, when it comes to renewable energy systems and PV, it is not just large systems that matter. Building-integrated photovoltaics or "onsite" PV systems have the advantage of being matched to end use energy needs in terms of scale. So the energy is supplied close to where it is needed.Use of ethanol for transportationE95 trial bus operating in São Paulo, Brazil. See also: Ethanol fuel and BioEthanol for Sustainable TransportSince the 1970s, Brazil has had an ethanol fuel program which has allowed the country to become the world's second largest producer of ethanol (after the United States) and the world's largest exporter. Brazil's ethanol fuel program uses modern equipment and cheap sugar cane as feedstock, and the residual cane-waste (bagasse) is used to process heat and power. There are no longer light vehicles in Brazil running on pure gasoline. By the end of 2008 there were 35,000 filling stations throughout Brazil with at least one ethanol pump.Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and motor vehicle manufacturers already produce vehicles designed to run on much higher ethanol blends. Ford, DaimlerChrysler, and GM are among the automobile companies that sell "flexible-fuel" cars, trucks, and minivans that can use gasoline and ethanol blends ranging from pure gasoline up to 85% ethanol (E85). By mid-2006, there were approximately six million E85-compatible vehicles on U.S. roads. The challenge is to expand the market for biofuels beyond the farm states where they have been most popular to date. Flex-fuel vehicles are assisting in this transition because they allow drivers to choose different fuels based on price and availability. The Energy Policy Act of 2005, which calls for 7.5 billion gallons of biofuels to be used annually by 2012, will also help to expand the market.Geothermal energy prospectsSee also: Geothermal energy in the United States The West Ford Flat power plant is one of 21 power plants at The Geysers The Geysers, is a geothermal power field located 72 miles (116 km) north of San Francisco, California. It is the largest geothermal development in the world outputting over 750 MW.Geothermal power capacity surpassed 10 GW in 2008. The United States is the world leader, with some 120 projects under development in early 2009, representing at least 5 GW. Other countries with significant recent growth in geothermal include Australia, El Salvador, Guatemala, Iceland, Indonesia, Kenya, Mexico, Nicaragua, Papua New Guinea, and Turkey. As of 2008, geothermal power development was under way in more than 40 countries. Geothermal power accounted for 17 percent of the Philippines total power mix at the end of 2008, with installed capacity close to 2,000 megawatts.Geothermal (ground source) heat pumps represented an estimated 30 GWth of installed capacity at the end of 2008, with other direct uses of geothermal heat (i.e., for space heating, agricultural drying and other uses) reaching an estimated 15 GWth. As of 2008, at least 76 countries use direct geothermal energy in some form.Wave farms expansionMain article: Wave farm Portugal now has the world's first commercial wave farm, the Agucadoura Wave Park, officially opened in September 2008. The farm uses three Pelamis P-750 machines generating 2.25 MW. Initial costs are put at €8.5 million. A second phase of the project is now planned to increase the installed capacity to 21MW using a further 25 Pelamis machines.Funding for a wave farm in Scotland was announced in February, 2007 by the Scottish Government, at a cost of over 4 million pounds, as part of a £13 million funding packages for ocean power in Scotland. The farm will be the world's largest with a capacity of 3MW generated by four Pelamis machines.Developing country marketsMain article: Renewable energy in developing countries Renewable energy can be particularly suitable for developing countries. In rural and remote areas, transmission and distribution of energy generated from fossil fuels can be difficult and expensive. Producing renewable energy locally can offer a viable alternative.Renewable energy projects in many developing countries have demonstrated that renewable energy can directly contribute to poverty alleviation by providing the energy needed for creating businesses and employment. Renewable energy technologies can also make indirect contributions to alleviating poverty by providing energy for cooking, space heating, and lighting. Renewable energy can also contribute to education, by providing electricity to schools.Kenya is the world leader in the number of solar power systems installed per capita (but not the number of watts added). More than 30,000 very small solar panels, each producing 12 to 30 watts, are sold in Kenya annually. For an investment of as little as $100 for the panel and wiring, the PV system can be used to charge a car battery, which can then provide power to run a fluorescent lamp or a small television for a few hours a day. More Kenyans adopt solar power every year than make connections to the country's electric grid.In India, a solar loan program sponsored by UNEP has helped 100,000 people finance solar power systems in India. Success in India's solar program has led to similar projects in other parts of developing world like Tunisia, Morocco, Indonesia and Mexico.Industry and policy trendsSee also: Renewable energy industry and Renewable energy policy Global revenues for solar photovoltaics, wind power, and biofuels expanded from $76 billion in 2007 to $115 billion in 2008. New global investments in clean energy technologies expanded by 4.7 percent from $148 billion in 2007 to $155 billion in 2008. U.S. President Barack Obama's American Recovery and Reinvestment Act of 2009 includes more than $70 billion in direct spending and tax credits for clean energy and associated transportation programs. Clean Edge suggests that the commercialization of clean energy will help countries around the world pull out of the current economic malaise.Constraints and opportunitiesCritics suggest that some renewable energy applications may create pollution, be dangerous, take up large amounts of land, or be incapable of generating a large net amount of energy. Proponents advocate the use of "appropriate renewables", also known as soft energy technologies, as these have many advantages. Availability and reliabilityFurther information: Energy security and renewable technology and Intermittent power source There is no shortage of solar-derived energy on Earth. Indeed the storages and flows of energy on the planet are very large relative to human needs.Annual photosynthesis by the vegetation in the United States is 50 billion GJ, equivalent to nearly 60% of the nation's annual fossil fuel use.The amount of solar energy intercepted by the Earth every minute is greater than the amount of energy the world uses in fossil fuels each year.The energy in the winds that blow across the United States each year could produce more than 16 billion GJ of electricity-more than one and one-half times the electricity consumed in the United States in 2000.Tropical oceans absorb 560 trillion gigajoules (GJ) of solar energy each year, equivalent to 1,600 times the world's annual energy use.A criticism of some renewable sources is their variable nature. But renewable power sources can actually be integrated into the grid system quite well, as Amory Lovins explains:Variable but forecastable renewables (wind and solar cells) are very reliable when integrated with each other, existing supplies and demand. For example, three German states were more than 30 percent wind-powered in 2007-and more than 100 percent in some months. Mostly renewable power generally needs less backup than utilities already bought to combat big coal and nuclear plants' intermittence.Mark Z. Jacobson has studied how wind, water and solar technologies can provide 100 per cent of the world's energy, eliminating all fossil fuels. He advocates a "smart mix" of renewable energy sources to reliably meet electricity demand:Because the wind blows during stormy conditions when the sun does not shine and the sun often shines on calm days with little wind, combining wind and solar can go a long way toward meeting demand, especially when geothermal provides a steady base and hydroelectric can be called on to fill in the gaps.The challenge of variable power supply BE be readily alleviated by certain forms of grid energy storage such as pumped-storage hydro systems, hydrogen fuel cells, thermal mass and compressed air. Batteries are still far too expensive to have any impact.From detailed studies in Europe, Dr Gregor Czisch has shown that the variable power issue can be solved by interconnecting renewable across Europe the European super grid and using only existing storage hydro. The costs of power over the lifetime of the scheme are the same as today's conventional power supplies, indicating that the capital investment is roughly the same as the cost of fuel avoided over the projects 25 year lifetime.Lovins goes on to say that the unreliability of renewable energy is a myth, while the unreliability of nuclear energy is real. Of all U.S. nuclear plants built, 21 percent were abandoned and 27 percent have failed at least once. Successful reactors must close for refueling every 17 months for 39 days. And when shut in response to grid failure, they can't quickly restart. This is simply not the case for wind farms, for example.Wave energy and some other renewables are continuously available. A wave energy scheme installed in Australia generates electricity with an 80% availability factor.Sustainable development and global warming groups propose a 100% Renewable Energy Source Supply, without fossil fuels and nuclear power. Scientists from the University of Kassel have suggested that Germany can power itself entirely by renewable energy.AestheticsBoth solar and wind generating stations have been criticized from an aesthetic point of view. However, methods and opportunities exist to deploy these renewable technologies efficiently and unobtrusively: fixed solar collectors can double as noise barriers along highways, and extensive roadway, parking lot, and roof-top area is currently available; amorphous photovoltaic cells can also be used to tint windows and produce energy. Advocates of renewable energy also argue that current infrastructure is less aesthetically pleasing than alternatives, but sited further from the view of most critics. Environmental, social and legal considerationsWhile most renewable energy sources do not produce pollution directly, the materials, industrial processes, and construction equipment used to create them may generate waste and pollution. Some renewable energy systems actually create environmental problems. Land area requiredAnother environmental issue, particularly with biomass and biofuels, is the large amount of land required to harvest energy, which otherwise could be used for other purposes or left as undeveloped land. However, it should be pointed out that these fuels may reduce the need for harvesting non-renewable energy sources, such as vast strip-mined areas and slag mountains for coal, safety zones around nuclear plants, and hundreds of square miles being strip-mined for oil sands. These responses, however, do not account for the extremely high biodiversity and endemism of land used for ethanol crops, particularly sugar cane. In the U.S., crops grown for biofuels are the most land- and water-intensive of the renewable energy sources. In 2005, about 12% of the nation's corn crop (covering 11 million acres (45,000 km²) of farmland) was used to produce four billion gallons of ethanol-which equates to about 2% of annual U.S. gasoline consumption. For biofuels to make a much larger contribution to the energy economy, the industry will have to accelerate the development of new feedstocks, agricultural practices, and technologies that are more land and water efficient.The efficiency of biofuels production has increased significantly and there are new methods to boost biofuel production, although using bioelectricity, by burning the biomass to produce electricity for an electric car, increases the distance that a car can go from a hectare (about 2.5 acres) of crops by 81%, from 30,000 km to 54,000 km per year. However, covering that same hectare with photovoltaics (in relatively sunless Germany or England) allows the electric car to go 3,250,000 km/year, over 100 times as far as from biofuel.HydroelectricityThe major advantage of hydroelectric systems is the elimination of the cost of fuel. Other advantages include longer life than fuel-fired generation, low operating costs, and the provision of facilities for water sports. Operation of pumped-storage plants improves the daily load factor of the generation system. Overall, hydroelectric power can be far less expensive than electricity generated from fossil fuels or nuclear energy, and areas with abundant hydroelectric power attract industry. However, there are several major disadvantages of hydroelectric systems. These include: dislocation of people living where the reservoirs are planned, release of significant amounts of carbon dioxide at construction and flooding of the reservoir, disruption of aquatic ecosystems and birdlife, adverse impacts on the river environment, potential risks of sabotage and terrorism, and in rare cases catastrophic failure of the dam wall. (See Hydroelectricity article for details.)Large hydroelectric power is considered to be a renewable energy by a large number of sources, however, many groups have lobbied for it to be excluded from renewable electricity standards, any initiative to promote the use of renewable energies, and sometimes the definition of renewable itself. Some organizations, including US federal agencies, will specifically refer to "non-hydro renewable energy". Many laws exist that specifically label "small hydro" as renewable or sustainable and large hydro as not. Furthermore, the line between what is small or large also differs by governing body.Hydroelectric power is now more difficult to site in developed nations because most major sites within these nations are either already being exploited or may be unavailable for other reasons such as environmental considerations.Wind farmsWind power is one of the most environmentally friendly sources of renewable energy A wind farm, when installed on agricultural land, has one of the lowest environmental impacts of all energy sources: To generate the total electricity used in the UK annually, 6% of the land area would be utilised, an area of about 70 miles by 70 miles, and this would not preclude that land from being used for other purposes.Wind power occupies less land area per kilowatt-hour (kWh) of electricity generated than any other energy conversion system, apart from rooftop solar energy, and is compatible with grazing and crops.It generates the energy used in its construction in just 3 months of operation, yet its operational lifetime is 20-25 years.Greenhouse gas emissions and air pollution produced by its construction are low and declining. There are no emissions or pollution produced by its operation.In substituting for base-load coal power, wind power produces a net decrease in greenhouse gas emissions and air pollution, and a net increase in biodiversity.Modern wind turbines are almost silent and rotate so slowly (in terms of revolutions per minute) that they are rarely a hazard to birds.Studies of birds and offshore wind farms in Europe have found that there are very few bird collisions. Several offshore wind sites in Europe have been in areas heavily used by seabirds. Improvements in wind turbine design, including a much slower rate of rotation of the blades and a smooth tower base instead of perchable lattice towers, have helped reduce bird mortality at wind farms around the world. However older smaller wind turbines may be hazardous to flying birds. Birds are severely impacted by fossil fuel energy; examples include birds dying from exposure to oil spills, habitat loss from acid rain and mountaintop removal coal mining, and mercury poisoning.Longevity issuesThough a source of renewable energy may last for billions of years, renewable energy infrastructure, like hydroelectric dams, will not last forever, and must be removed and replaced at some point. Events like the shifting of riverbeds, or changing weather patterns could potentially alter or even halt the function of hydroelectric dams, lowering the amount of time they are available to generate electricity. Some have claimed that geothermal being a renewable energy source depends on the rate of extraction being slow enough such that depletion does not occur. If depletion does occur, the temperature can regenerate if given a long period of non-use.The government of Iceland states: "It should be stressed that the geothermal resource is not strictly renewable in the same sense as the hydro resource." It estimates that Iceland's geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW. Radioactive elements in the Earth's crust continuously decay, replenishing the heat. The International Energy Agency classifies geothermal power as renewable.Biofuels productionSee also: Ethanol fuel energy balance and Cellulosic ethanol commercialization All biomass needs to go through some of these steps: it needs to be grown, collected, dried, fermented and burned. All of these steps require resources and an infrastructure.Some studies contend that ethanol is "energy negative", meaning that it takes more energy to produce than is contained in the final product. However, a large number of recent studies, including a 2006 article in the journal Science offer the opinion that fuels like ethanol are energy positive. Furthermore, fossil fuels also require significant energy inputs which have seldom been accounted for in the past.Additionally, ethanol is not the only product created during production, and the energy content of the by-products must also be considered. Corn is typically 66% starch and the remaining 33% is not fermented. This unfermented component is called distillers grain, which is high in fats and proteins, and makes good animal feed. In Brazil, where sugar cane is used, the yield is higher, and conversion to ethanol is somewhat more energy efficient than corn. Recent developments with cellulosic ethanol production may improve yields even further.According to the International Energy Agency, new biofuels technologies being developed today, notably cellulosic ethanol, could allow biofuels to play a much bigger role in the future than previously thought. Cellulosic ethanol can be made from plant matter composed primarily of inedible cellulose fibers that form the stems and branches of most plants. Crop residues (such as corn stalks, wheat straw and rice straw), wood waste, and municipal solid waste are potential sources of cellulosic biomass. Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be sustainably produced in many regions of the United States.The ethanol and biodiesel production industries also create jobs in plant construction, operations, and maintenance, mostly in rural communities. According to the Renewable Fuels Association, the ethanol industry created almost 154,000 U.S. jobs in 2005 alone, boosting household income by $5.7 billion. It also contributed about $3.5 billion in tax revenues at the local, state, and federal levels.DiversificationThe examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page.The U.S. electric power industry now relies on large, central power stations, including coal, natural gas, nuclear, and hydropower plants that together generate more than 95% of the nation's electricity. Over the next few decades uses of renewable energy could help to diversify the nation's bulk power supply. Already, appropriate renewable resources (which excludes large hydropower) produce 12% of northern California's electricity.Although most of today's electricity comes from large, central-station power plants, new technologies offer a range of options for generating electricity nearer to where it is needed, saving on the cost of transmitting and distributing power and improving the overall efficiency and reliability of the system.Improving energy efficiency represents the most immediate and often the most cost-effective way to reduce oil dependence, improve energy security, and reduce the health and environmental impact of the energy system. By reducing the total energy requirements of the economy, improved energy efficiency could make increased reliance on renewable energy sources more practical and affordable.Competition with nuclear powerSee also: Nuclear power proposed as renewable energy Nuclear power continues to be considered as an alternative to fossil-fuel power sources (see Low carbon power generation), and in 1956, when the first peak oil paper was presented, nuclear energy was presented as the replacement for fossil fuels. However, the prospect of increased nuclear power deployment was seriously undermined in the United States as a result of the Three Mile Island, and in the rest of the world after the Chernobyl disaster. This trend is slowly reversing, and several new nuclear reactors are scheduled for construction.Physicist Bernard Cohen proposed in 1983 that uranium dissolved in seawater is effectively inexhaustible, and could therefore be considered a renewable source of energy. However, this idea is not universally accepted, and issues such as peak uranium and uranium depletion are ongoing debates.No legislative body has yet included nuclear energy under any legal definition of "renewable energy sources" for provision of development support, and statutory and scientific definitions of renewable energies normally exclude nuclear energy