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Molten salts vs Oil |
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Currently operating parabolic trough’s plants use a synthetic aromatic fluid as heat transfer fluid. This fluid is organic (benzene) based and as such cannot reach temperatures above 400ºC with acceptable performance, due to its degradation into unusable components at high temperatures. At temperatures higher than 400ºC, fluid becomes inoperable. As such, this limited temperature range is capping overall steam cycle efficiency.
To overcome this obstacle, Archimede Solar Energy and Consortium Solare XXI (www.solarexxi.com), are focusing on molten salts, an alternative fluid technology.
Molten salt, which is currently used as a heat storage medium, can be used as a working fluid without the 400ºC cap of regular Oil, reaching temperatures up to 550ºC. Using molten salt as heat transfer fluid enables a new plant configuration which can lead to savings at several levels:
1) storage system’s heat exchanger can be eliminated, since the fluid that goes from the solar field to the storage system is the same;
2) with operation at higher temperatures, the molten salt volume for the storage system can be reduced by 2/3 which also leads to a reduction in size of the storage tanks with an impact of 30% in costs. These savings represent an approximate 20% plant cost decrease when compared with normal Oil plants with storage. Also, due to the higher operating temperature plant efficiency can increase up to 6%.
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Molten salts work as sole fluid for both heat absorption and
storage allowing a simplified
design of the plant;
- Compared to traditional plants a
smaller thermal storage fully
compensate for solar
discontinuities;
- Standard turbines parameters
are matched by a higher
operating temperature;
- Unlike oil, molten salts are
environmentally friendly, non-flammable,
stable fluid, with no
degradation of the receiving tube.
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