Agriculture

Photovoltaic array – TDM Over IP Device – TDMoIP   by jekky

(1154, ‘Applications Urban uses In urban and suburban areas photovoltaic arrays are commonly used on rooftops to supplement power use often the building will have a connection to the power grid in which case the energy produced by the PV array can be sold back to the utility in some sort of net metering agreement Solar trees are arrays that as the name implies mimic the look of trees provide shade and at night can function as street lights A new option is the combination use of a solar array as a wall or roof feature replacing or complementing a standard wall as an integrated feature of the building rather than a retrofit Rural uses In more rural areas ground mounted PV systems are more common The systems may also be equipped with a battery backup system to compensate for a potentially unreliable power grid In agricultural settings the array may be used to directly power DC pumps without the need for an inverter In remote settings such as mountainous areas islands or other places where a power grid is unavailable solar arrays can be used as the sole source of electricity usually by charging a storage battery Together with a storage battery photovoltaics have become commonplace for certain low power applications such as signal buoys or devices in remote areas or simply where connection to the electricity mains would be impractical In experimental form they have even been used to power automobiles in races such as the World solar challenge across Australia Many yachts and land vehicles use them to charge on board batteries Space uses Solar panels on the Stardust spacecraft Main article Solar panels on spacecraft Satellites use solar arrays for their power In particular the International Space Station uses multiple solar arrays to power all the equipment on board Solar photovoltaic panels are frequently applied in satellite power Solar panels can be used on spacecraft particularly when they are in the inner part of the solar system They have been designed to pivot on spacecraft so that they will always be in the direct path of solar rays In order to optimize the amount of energy generated solar panels on spacecraft can be equipped with a Fresnel lens which concentrates sunlight Because of these efforts to maximize electric production and the fact that the Sun is mostly the only source of energy the construction of solar cells on spacecraft could be one of the highest costs When journeying to outer parts of the solar system or beyond nuclear reactors or radioisotope thermal generators are preferred as the Sun s rays are too weak at such extreme distances to power a spacecraft The ESA is researching the possibility of solar power satellites that would generate electricity in space and then beam it to Earth via laser or microwaves In addition solar power is being used as a propulsion power source for Ion propulsion in lieu of chemical propulsion Performance A solar panel on top of a parking meter Note that this particular installation is shaded and may not perform as desired At high noon on a cloudless day at the equator the power of the sun is about 1 kW m on the Earth s surface to a plane that is perpendicular to the sun s rays citation needed As such PV arrays can track the sun through each day to greatly enhance energy collection However tracking devices add cost and require maintenance so it is more common for PV arrays to have fixed mounts that tilt the array and face due South in the Northern Hemisphere in the Southern Hemisphere they should point due North The tilt angle from horizontal can be varied for season but if fixed should be set to give optimal array output during the peak electrical demand portion of a typical year Trackers and sensors to optimise the performance are often seen as optional but tracking systems can increase viable output by up to 100 PV arrays that approach or exceed one megawatt often use solar trackers Accounting for clouds and the fact that most of the world is not on the equator and that the sun sets in the evening the correct measure of solar power is insolation the average number of kilowatt hours per square meter per day For the weather and latitudes of the United States and Europe typical insolation ranges from 4kWh m day in northern climes to 6 5 kWh m day in the sunniest regions Typical solar panels have an average efficiency of 12 with the best commercially available panels at 20 citation needed Thus a photovoltaic installation in the southern latitudes of Europe or the United States may expect to produce 1 kWh m day A typical 150 watt solar panel is about a square meter in size Such a panel may be expected to produce 1 kWh every day on average after taking into account the weather and the latitude In the Sahara desert with less cloud cover and a better solar angle one can obtain closer to 8 3 kWh m day The unpopulated area of the Sahara desert is over 9 million km which if covered with solar panels would provide 630 terawatts total power citation needed The Earth s current energy consumption rate is around 13 5 TW at any given moment including oil gas coal nuclear and hydroelectric citation needed Other factors affect PV performance Many Photovoltaic cells electrical output is extremely sensitive to shading There are some non traditional solar cell manufacturers thin film a Si that have installed bypass diodes between each cell that minimize the effects of shading and only lose the power of the shaded portion of the array When even a small portion of a cell module or array is shaded while the remainder is in sunlight the output falls dramatically due to internal short circuiting the electrons reversing course through the shaded portion of the p n junction Therefore it is extremely important that a PV installation is not shaded at all by trees architectural features flag poles or other obstructions like continuously parked cars Sunlight can be absorbed by dust fallout or other impurities at the surface of the module This can cut down the amount of light that actually strikes the cells by as much as half Maintaining a clean module surface will increase output performance over the life of the module Module output and life are also degraded by increased temperature Allowing ambient air to flow over and if possible behind PV modules reduces this problem Effective module lives are typically 25 years or more See also Photovoltaics Battery Solar fan Hybrid vehicle Solar cell Solar tracker Solar vehicles Tribrid vehicle References a b c d Small Photovoltaic Arrays Research Institute for Sustainable Energy RISE Murdoch University http www rise org au info Applic Array index html Retrieved 5 February 2010 160 Solar Power Photovoltaic PV Agriculture and Agri Food Canada http www4 agr gc ca AAFC AAC display afficher do id 1187620075153 amp lang eng Retrieved 5 February 2010 160 Categories Photovoltaics Spacecraft componentsHidden categories Articles needing additional references from January 2010 All articles needing additional references Vague or ambiguous time All articles with unsourced statements Articles with unsourced statements from April 2008 Articles with unsourced statements from May 2008 Articles with unsourced statements from October 2009′)

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Andrew Goldstein, Agriculture & Agri-food Canada – ‘Issues affecting competiveness in agriculture’

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