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Terraformer

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From: The Fortunate Isles

Registered: 2007-08-27

Posts: 3,906

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Compact Linear Fresnel Reflector

Wikipedia article

The reflectors are located at the base of the system and converge the sun's rays into the absorber. A key component that makes all LFR's more advantageous than traditional parabolic trough mirror systems is the use of "Fresnel reflectors". These reflectors make use of the Fresnel lens effect, which allows for a concentrating mirror with a large aperture and short focal length while simultaneously reducing the volume of material required for the reflector. This greatly reduces the system's cost since sagged-glass parabolic reflectors are typically very expensive.[2] However, in recent years thin-film nanotechnology has significantly reduced the cost of parabolic mirrors.[6]

A major challenge that must be addressed in any solar concentrating technology is the changing angle of the incident rays (the rays of sunlight striking the mirrors) as the sun progresses throughout the day. The reflectors of a CLFR are typically aligned in a north-south orientation and turn about a single axis using a computer controlled solar tracker system.[7] This allows the system to maintain the proper angle of incidence between the sun's rays and the mirrors, thereby optimizing energy transfer.

University of Sydney page

The array uses flat or elastically curved reflectors instead of costly sagged glass reflectors. The reflectors are mounted close to the ground, minimising structural requirements. The heat transfer loop is separated from the reflector field and is fixed in space thus avoiding the high cost of flexible high pressure lines or high pressure rotating joints as required in the trough and dish concepts.
The heat transfer fluid is water, and passive direct boiling heat transfer can be used to avoid parasitic pumping losses and the use of expensive flow controllers.
An inverted cavity receiver has been designed using steel boiling tubes which can be directly linked with an existing fossil fuel plant steam system. This is much cheaper than evacuated tubes used in trough plants. Direct steam generation is much easier with this absorber than with tubular absorbers in trough collectors.
Maintenance will be low because of ease of reflector access for cleaning, and because the single ended evacuated tubes can be removed without breaking the heat transfer fluid circuit.

May not be as efficient as trough systems, but if we're optimising for total cost rather than minimising land area (we have quite a bit of desert available), perhaps it has a significant advantage? The structural support requirements seem to be a lot lower, and the mirrors could be mass produced slats that can be easily transported and swapped in and out. IDK if it would be easier to mass manufacture in a factory vs other systems.

We could also potentially use the land in between the slats in a way not possible with heliostats and troughs. The University of Sydney page suggests the slats could be opened up for daylighting on cloudy days; with the slats providing shielding during the hottest part of the day, maybe the desert soil beneath could be used for growing things in the cooler early morning and evening sunlight when the plant isn't generating..m

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Use what is abundant and build to last

tahanson43206

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Registered: 2018-04-27

Posts: 19,422

Re: Compact Linear Fresnel Reflector

This post is reserved for an index to posts that may be created by NewMars members over time.

This interesting new topic has significant upside potential!

Best wishes to Terraformer for success!

(th)