A parabolic trough is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, with a polished metal mirror . The energy of sunlight which enters the mirror parallel to its plane of symmetry is focused along the focal line , where the objects are intended to be heated. For example, food for the food of a trough, which causes the food to be cooked when the trough is intended for the Sun is in its plane of symmetry. Further information on the use of parabolic troughs for cooking can be found in the article about solar cookers .
For other purposes, there is often a tube, frequently a Dewar tube , which runs the length of the trough at its focal line. The mirror is focused on the tube, which contains a fluidwhich is heated to a high temperature by the energy of the sunlight. The hot fluid can be used for many purposes. Often, it is piped to a heat engine , which uses the heat energy to drive machinery or to generate electricity. This solar energy collector is the most common and best known type of parabolic trough. The paragraphs below
The trough is usually aligned on a north-south axis, and rotated to track the sun as it moves across the sky each day. Alternatively, the trough can be aligned on an east-west axis; this Reduces the overall efficiency of the collector due to cosine loss goal only requires the trough to be aligned with the change in seasons , Avoiding the need for tracking motors. This tracking methodologies are effective at the spring and fall equinoxes with less accurate focus of the light at other times during the year. The daily motion of the sun in the sun also introduces errors, greatest at the sunrise and sunset and small at solar noon. Due to these sources of error, the seasonally adjusted parabolic troughsconcentration acceptance product .
Parabolic trough concentrators have a simple geometry, but their concentration is about 1/3 of the theoretical maximum for the same acceptance angle , which is, for the same general tolerances of the system to all kinds of errors, including those referenced above. The theoretical maximum is better Achieved with more elaborate concentrators based one primary-secondary designs using nonimaging optics   qui May dual Nearly the concentration of conventional parabolic troughs  and are used to Improve practical designs Such As Those with fixed receivers. 
Heat transfer fluid (usually thermal oil ) through the tube to absorb the concentrated sunlight. This increases the temperature of the fluid to some 400 ° C.  The heat transfer fluid is then used to heat steam in a standard turbine generator. The process is economical, for heating the pipe, thermal efficiency ranges from 60-80%. The overall efficiency from collector to grid, ie (Electrical Output Power) is about 15%, similar to PV (Photovoltaic Cells) but less than Stirling dish concentrators . 
A parabolic trough is made of a number of solar collector modules ( SCM ) fixed together to move as one solar collector assembly ( SCA ). A SCM could have a length up to 15 meters (49 ft) or more. About SCM make each SCA up to 200 meters (660 ft) length. Each SCA is an independently tracking parabolic trough.
A SCM can be made as a single-piece parabolic mirror or assembled with a number of smaller mirrors in parallel rows. Smaller modular mirrors requires smaller machines to build the mirror, reducing cost. Cost is also reduced in the case of the need for replacing a damaged mirror, like after an object hit (during bad weather or other causes).
In addition, V-type parabolic troughs exist which are made from 2 mirrors and placed at an angle to each other. 
In 2009, scientists at the National Energy Renewable Energy Laboratory (NREL) and SkyFuel are teaming up to increase the energy efficiency of their batteries by replacing glass-based models with a silver polymer sheet that has the same performance as the heavy glass mirrors, but at a much lower cost and much lower weight. It is much easier to deploy and install. The glossy film uses several layers of polymers, with an inner layer of pure silver. 
As this renewable source of energy is inconsistent by nature, methods for energy storage-have-been Studied, for instance the single-tank ( thermocline ) storage technology for large-scale solar thermal power plants. The thermocline tank approach uses a mixture of silica sand and quartzite rock to displace a significant portion of the volume in the tank. Then it is filled with the heat transfer fluid, typically a molten nitrate salt .
The enclosed trough architecture encapsulates the solar thermal system within a greenhouse-like glasshouse. The glasshouse creates a protected environment and the elements that can negatively impact the reliability and efficiency of the solar thermal system. 
Lightweight curved solar-reflecting mirrors are suspended within the glasshouse structure. A single-axis tracking system positions the mirrors to track the sun and focus its light onto a network of stationary steel pipes, also suspended from the glasshouse structure.  Steam is generated directly using oil field-quality water, as it flows through the length of the pipes, without heat exchangers or intermediate working fluids.
The steam produced is then fed directly to the field’s existing steam distribution network, where the steam is continuously injected into the oil reservoir. Sheltering the mirrors from the wind allows them to achieve higher temperatures and prevents dust from building up.  GlassPoint Solar , the company that created the Enclosed Trough design, states its technology can produce heat for about $ 5 per million. 
Early commercial adoption
In 1897, Frank Shuman , a US inventor, engineer and solar energy pioneer built a small demonstration solar engine that worked by reflecting solar energy on square boxes filled with ether, which has a lower boiling point than water, and was fitted internally with black pipes which in turn powered by steam engine. In 1908 Shuman formed the Sun Power Company with the intention of building larger solar power plants. He, along with his technical advisor ASE Ackermann and British physicist Sir Charles Vernon Boys , [ citation needed ]An improved system using solar energy collectors can be used instead of increasing energy efficiency. Shuman then constructed a full-scale steam engine powered by low-pressure water, enabling him to patent the entire solar engine system by 1912.
Shuman built the world’s first solar power station in Maadi , Egypt between 1912 and 1913. Shuman’s plant used parabolic troughs to power at 45-52 kilowatt (60-70 hp ) engine that pumped more than 22,000 liters of water per minute from the Nile River to adjacent cotton fields. Although the outbreak of World War I and the discovery of cheap energy in the 1930s, the advancement of solar energy, Shuman’s vision and basic design were resurrected in the 1970s with a new wave of interest in solar thermal energy.  In 1916 Shuman was quoted in the media advocating solar energy’s use, saying:
We have proved to be the most profitable product in the world.- Frank Shuman, New York Times, July 2, 1916 
Commercial plants Utilizing parabolic troughs May use thermal storage at night while Some Are hybrids and supporting natural gas as a secondary fuel source. In the US the amount of fossil fuel is limited to a maximum of 27% of electricity production, allowing the plant to qualify for renewable energy sources. [ citation needed ] Because they include cooling stations, condensers , accumulators and other things besides the solar collectors.
As of 2014, the Largest solar thermal power systems using parabolic trough technology include, the 354 MW SEGS plants in California, the 280 MW Solana Generating Station That features a molten salt heat storage , the 250 MW Genesis Solar Energy Project , That cam online in 2014, 200 MW Solaben Solar Power Station, the 200 MW Solnova Solar Power Station , and the Andasol 1 solar power station , using a Eurotrough – collector .  
- Parabolic reflector
- Solar cooker
- List of Solar Thermal Power Stations
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