Linear Fresnel Reflectors (LFR) are also based on solar collector rows or loops. However, in this case, the parabolic shape is achieved by almost flat linear facets. The radiation is reflected and concentrated onto fixed linear receivers mounted over the mirrors, combined or not with secondary concentrators. One of the advantages of this technology is its simplicity and the ability to use low cost components. Direct saturated steam systems with fixed absorber tubes have been operated at an early stage of use with LFR technology. This technology eliminates the need for HTF and heat exchangers. Increasing the efficiency depends on superheating the steam. Superheated steam up to 500°C has been demonstrated at pilot plant scale and the first large commercial superheated LFR plant has recently begun operation.
Since steam is the working fluid, LFR technology is usually fitted with a steam storage system. Molten salt storage systems can be also implemented. Furthermore, PCM storage systems are currently demonstrated at pilot plant scale.
There are almost more than 200 MW of LFR plants in operation or under construction. After a first pilot scale application in Australia, a few new pilot plants were developed and tested in Spain and the United States. In 2012, the first commercial 30 MW Puerto-Errado 2 plant began operating in Spain. France has already constructed two LFR pilot plants and is currently building two additional commercial plants with this technology. Sized 9 MW and 12 MW, and named Llo and Alba Nova 1, these plants are being built by CNIM and SOLAR EUROMED, respectively. In Australia, two plants are currently operating with this technology, sized 6 MW and 9.3 MW. A 44 MW plant is also under construction at Kogan Creek. In India, Reliance Power has completed and connected to the grid a 125 MW Compact LFR plant, designed and constructed by AREVA Solar, in November 2014 (see Case Study Dhursar).
More than 200 MW of LFR plants are currently operating or under construction. After a first pilot scale application in Australia, a few new pilot plants were developed and tested in Spain and the United States. In 2012, the first commercial 30 MW Puerto-Errado 2 plant began operating in Spain. France has already constructed two Linear Fresnel pilot plants and is currently building two additional commercial plants with this technology. Sized 9 MW and 12 MW, and named Llo and Alba Nova 1, these plants are being built by CNIM and SOLAR EUROMED, respectively. In Australia, two plants are currently operating with this technology, sized 6 MW and 9.3 MW. A 44 MW plant is also under construction at Kogan Creek. In India, Reliance Power has completed and connected to the grid a 125 MW Compact Linear Fresnel Reflector plant, designed and constructed by AREVA Solar. (see Case Study Dhursar)
Compared to other technologies, the investment costs per square meter of collector field using LFR technology tend to be lower because of the simpler solar field construction. Also, the use of direct steam generation promises relatively high conversion efficiency and a simpler thermal cycle design. The Fresnel design uses less expensive reflector materials and absorber components. It has lower optical performance and thermal output but this is offset by lower investment and operation and maintenance costs. The Fresnel system also provides a semi- shaded space, which may be particularly useful in desert climates for agriculture. Acting like a large, segmented blind it could shade crops, pasture and water bodies to protect them from excessive evaporation and provide shelter from the cold desert sky at night. Many improvements in the absorber tubes and the geometry are under development. Some of those ongoing improvement efforts relate to the shape and the disposition of mirrors to accommodate some of the peculiarities of this technology.
Therefore, LFR offers high thermal performance and low cost, as well as various cost competitive thermal energy storage solutions. Hence, LFR is becoming one of the STE technologies capable of achieving very low LCOE costs.
In addition to electricity generation, LFR technology is also quite useful for direct thermal applications, such as cooling or industrial process heat applications. Very low cost LFR collectors are providing 200°C-300°C steam solutions at a competitive cost for process heat applications such as desalination, food processing and pharmaceutical industries. Low cost LFR collectors are providing 250°C-500°C steam solutions at very competitive cost to hybrid STE – fuel fired combined cycle or Enhanced Oil Recovery applications.
