Cavity Receivers for Parabolic Solar Troughs
A tubular heat-absorbing element partly enclosed in an insulating layer or jacket, has absorbing surface that is accessible to solar radiation. The thermal insulation is designed to provide entry to solar radiation by way of a cavity. The absorbing surface can be substantially planar.
1 . A method of capturing energy from solar radiation, comprising the steps of:
admitting solar radiation through a solar radiation admitting region, said solar radiation admitting region having an interior surface, at least a portion of said solar radiation admitting region being surrounded by substantially opaque thermal insulation, said solar radiation admitting region designed to allow transmission of at least a portion of said incident flux of solar radiation to be incident on a solar selective absorber present on a substantially planar region of an outer surface of a solar radiation absorbing element, said solar selective absorber being exposed to ambient atmospheric pressure, said solar radiation admitting region being symmetric with respect to a plane parallel to a length dimension of said solar radiation absorbing element, said plane oriented in a perpendicular direction to said substantially planar region of said outer surface of said solar radiation absorbing element;
absorbing at least a portion of the energy present in said admitted solar radiation in said solar selective absorber; and
transferring said absorbed energy from said solar selective absorber to a heat transfer medium present within said solar radiation absorbing element.
2 . The method of capturing energy from solar radiation of claim 1 , further comprising the steps of:
transporting said heat transfer medium containing said absorbed energy to a heat exchanger; and
extracting a portion of said absorbed energy from said heat transfer medium for later use.
3 . The method of capturing energy from solar radiation of claim 1 , further comprising the step of:
concentrating solar radiation by way of a reflector prior to the step of admitting solar radiation through a solar radiation admitting region.
4 . The method of capturing energy from solar radiation of claim 1 , further comprising the step of:
generating electricity with at least a portion of said absorbed energy.
5 . The method of capturing energy from solar radiation of claim 1 , further comprising the step of:
storing at least a portion of said absorbed energy for use at a later time.
6 . The method of capturing energy from solar radiation of claim 1 , wherein said first portion of said outer surface of said solar radiation absorbing element comprises a fraction in the range of 0.50 to 0.20 of an area of said outer surface of said solar radiation absorbing element determined on a per unit length basis.
7 . The method of capturing energy from solar radiation of claim 1 , wherein a glass cover encloses the solar radiation admitting region.
8 . The method of capturing energy from solar radiation of claim 4 , further comprising the step of introducing an inert gas into the radiation admitting region.
9 . The method of capturing energy from solar radiation of claim 1 , wherein said interior surface of said solar radiation admitting region forms a compound parabolic collector.
10 . The method of capturing energy from solar radiation of claim 1 , wherein said interior surface of said solar radiation admitting region comprises a reflective surface.
11 . The method of capturing energy from solar radiation of claim 1 , wherein said heat transfer medium is selected from the group consisting of a molten solar salt, a molecular silicone based fluid, and steam.
12 . The method of capturing energy from solar radiation of claim 1 , wherein said linear receiver has a thermal efficiency, said thermal efficiency is selected from the group consisting of 94 percent at 450 degrees Celsius and 92 percent at 500 degrees Celsius, 89 percent at 550 degrees Celsius, 85 percent at 600 degrees Celsius, 80 percent at 650 degrees Celsius.
13 . The method of capturing energy from solar radiation of claim 1 , in combination with an energy collection system configured to operate a Carnot cycle energy recovery machine.
14 . The method of capturing energy from solar radiation of claim 1 , in combination with a plurality of linear solar receivers, said linear solar receivers each including at least solar radiation absorbing elements, adjacent solar radiation absorbing elements forming a nearly continuous absorbing surface.
15 . The method of capturing energy from solar radiation of claim 1 , in combination with a plurality of linear solar receivers, a first one of said plurality of receivers operating at a first temperature and a second one of said plurality of receivers operating at a second temperature, said first receiver and said second of said plurality of receivers having different designs, said first and said second temperatures being different.
16 . The method of capturing energy from solar radiation of claim 1 , further comprising the step of providing a symmetric parabolic trough collector mirror structure having a rim angle of less than 75 degrees, said symmetric parabolic trough collector mirror structure focusing said incident flux of solar radiation on said solar radiation absorbing element, said linear solar receiver disposed between said symmetric parabolic trough collector mirror structure and the sun.
17 . The method of capturing energy from solar radiation of claim 1 , further comprising the step of providing a symmetric parabolic trough collector mirror structure, said symmetric parabolic trough collector mirror structure being held in a substantially rigid form with cable suspension.
18 . The method of capturing energy from solar radiation of claim 1 , wherein at least a portion of said absorbed flux of absorbed energy is used to perform an action chosen from the group consisting of generating electricity and completing an industrial process.
19 . The method of capturing energy from solar radiation of claim 1 , wherein said solar selective absorber is a plasmonic nanochain cermet structure.