Parabolic mirrors concentrate a lot of energy over the cross section of the energy collector and the intent is to drive the temperature as high as is safe. That means that the working fluid is the primary design constraint. These fluids go to 300 C plus and remain fluid under the temperature of boiling water.
That suggests that a gallon of hot working fluid is sufficient to carry enough heat to vaporize a gallon of water used in the power turbine. What is more, it pumps efficiently after cool down to under the temperature of boiling water.
An engineer can live quite happily with those types of numbers. And there is no special need to look further. Just do not grab any exposed pipes unless you feel like leaving your skin.
Dow Captures Solar Power With Fluid Technology
by Staff Writers
Midland MI (SPX) Jun 09, 2009
http://www.solardaily.com/reports/Dow_Captures_Solar_Power_With_Fluid_Technology_999.html
Dow Chemical is shedding light on Concentrating Solar Power systems (CSP) with DOWTHERM A heat transfer fluids which can collect, transport and store solar generated heat.
CSP technology uses mirrors to reflect and concentrate sunlight onto receivers that collect solar energy and convert it to heat. DOWTHERM A heat transfer fluids collect the heat energy and transport it to a power generating station. The transported heat converts water to steam, which in turn drives turbines to make electricity.
"We are committed to harnessing the vast potential of the sun to continue setting the standard for sustainability," said Neil Hawkins, Dow's vice president of sustainability.
"In addition to innovations in sustainable chemistry that result in products like DOWTHERM A, we've also made significant advancements in photovoltaic technology through the development of a game-changing residential solar shingle by the Dow Solar Solutions business. Our 2015 sustainability goals are driving innovation that is good for business and good for the world."
Dow has supplied, or is in the process of supplying, enough DOWTHERM A globally to generate more than 500 megawatts of electricity from the sun - positioning its Performance Fluids Business as the leading supplier of heat transfer fluids in the world for parabolic trough based solar systems.
Solar power producers in the United States, Middle East, Spain, Australia, India and other locations are tapping into Dow's technology and world-scale production and supply capabilities.
Recent projects in Spain will be using more than 5,000 metric tons of DOWTHERM A heat transfer fluids that will eventually generate enough electricity for about 120,000 households. These plants will also prevent the release of about 350,000 tons of carbon dioxide that would have otherwise been released into the aosphere had traditional fuels been used.
Dow has demonstrated its commient and leadership in energy efficiency all around the world. Over the last 14 years, Dow's efforts to conserve power globally have resulted in saving more than 1,600 trillion BTUs of energy and prevented the release of about 86 million metric tons of carbon dioxide.
http://www.dow.com/heattrans/prod/synthetic/dowtherm.htm
DOWTHERM™ A heat transfer fluid is a eutectic mixture of two very stable compounds, biphenyl (C12H10) and diphenyl oxide (C12H10O). The fluid is dyed clear to light yellow to aid in leak detection. DOWTHERM A fluid may be used in systems employing either liquid phase or vapor phase heating. Suitable applications include indirect heat transfer.
DOWTHERM G heat transfer fluid contains a mixture of di- and tri-aryl ethers that provide unequaled performance in liquid phase heat transfer systems. It is the most thermally stable low pressure liquid phase heat transfer fluid on the market today and has excellent flow characteristics at low temperatures.
DOWTHERM J heat transfer fluid is a mixture of isomers of an alkylated aromatic specially engineered for demanding low-temperature applications in liquid phase pressurized systems. DOWTHERM J fluid offers outstanding low-temperature pumpability and excellent thermal stability for protection against accidental overheating. Suitable applications include single fluid heating and cooling.
DOWTHERM MX heat transfer fluid is a mixture of alkylated aromatics designed for use as an alternative to hot oils in liquid phase heat transfer systems. DOWTHERM MX fluid is suitable for use in non-pressurized systems, its good low temperature properties allow for low temperature start-up and pumpability. Expansion Tank Design: Even though DOWTHERM MX fluid can be operated in a non-pressurized system, it is recommended that the tank have an inert atmosphere. Nitrogen padding should be used on the expansion tank to exclude oxygen from the heat transfer system. The presence of oxygen will cause accelerated fluid degradation, which will considerably shorten the life of the fluid.
DOWTHERM Q heat transfer fluid contains a mixture of diphenylethane and alkylated aromatics. Compared to hot oils, it exhibits better thermal stability, particularly at the upper end of hot oils' use range, and significantly better low-temperature pumpability. Suitable applications include use as an alternative to hot oils in liquid phase heat transfer applications.
DOWTHERM RP heat transfer fluid is a diaryl alkyl intended for use in applications that require liquid phase heat transfer. Unlike other low pressure fluids — including partially hydrogenated terphenyls and dibenzyl toluene fluids — DOWTHERM RP fluid degrades primarily to low molecular weight products. This reduces the need to remove high molecular weight material from the system, resulting in longer fluid life, reduced fluid makeup requirements, less system downtime, and lower fluid and maintenance expense over the life of the heat transfer system. Suitable applications include non-pressurized or low pressure liquid phase systems including polyester, nylon, and other synthetic fiber processing facilities.
DOWTHERM T heat transfer fluid is a mixture of C14-C30 alkyl benzenes intended for use in applications that require liquid phase heat transfer. Suitable applications: Non-pressurized liquid phase systems with a maximum temperature of 550°F (288°C).
DOWTHERM A (21KB PDF)
EuropeNorth AmericaLatin AmericaAsia-PacificIndia, Middle East & Africa
Oil & Gas, Plastic Processing, Chemical Processing, Solar Energy
Liquid phase: 15°C to 400°C (60°F to 750°F) Vapor phase: 257°C to 400°C (495°F to 750°F)
DOWTHERM G (19KB PDF)
EuropeNorth AmericaLatin AmericaAsia-PacificIndia, Middle East & Africa
Oil & Gas, Plastic Processing, Chemical Processing, Heat Recovery
29°C to 371°C (-20°F to 700°F)
DOWTHERM J (29KB PDF)
EuropeNorth AmericaLatin AmericaAsia-PacificIndia, Middle East & Africa
Pharmaceutical, Chemical Processing
-80°C to 315°C (-100°F to 600°F). Vapor Phase 181°C to 315°C (358°F to 600°F)
DOWTHERM MX (17KB PDF)
EuropeNorth AmericaLatin AmericaAsia-PacificIndia, Middle East & Africa
Chemical Processing
DOWTHERM Q (25KB PDF)
EuropeNorth AmericaLatin AmericaAsia-PacificIndia, Middle East & Africa
Oil & Gas, Chemical Processing, Heat Recovery
-35°C to 330°C (-30°F to 625°F)
DOWTHERM RP (26KB PDF)
EuropeNorth AmericaLatin AmericaAsia-PacificIndia, Middle East & Africa
Oil & Gas, Heat Recovery, Plastics and Chemical Processing
maximum bulk temperature of 350°C (660°F) and amaximum film temperature of 375°C (710°F)
DOWTHERM T (24KB PDF)
EuropeNorth AmericaLatin AmericaAsia-PacificIndia, Middle East & Africa
Chemical ProcessingOil & Gas
288°C (550°F) Bulk temperature of 315°C (600°F)
