A bifacial thermal absorber is used. 50% of the light falls on the front of the absorber. The rest is reflected to the back of the absorber with a mirror. The input aperture is 1m2, the radius of the absorber is 10mm, the average concentration level is 3087 with an optical geometric efficiency of 97% (excluding reflection/transmission/tip losses).
If only the front surface is used, then the optical efficiency drops to 87.3% for an average concentration level of 3080 (run fresnelx w1000 g2500 l10000 s1000 c870:9.5 r0). About 6% (after subtracting the reflective loss due to the mirror) more energy can be extracted by using both surfaces.
The heat from an array of these absorbers will be stored in graphite pebbles. The heat from the storage system will be used to produce mechanical work (Rankine, Ericsson, Stirling, Scroll, Brayton and rotary engines). Mechanical compressor can use this mechanical energy for cooling or heating purpose. The mechanical energy can be converted directly to AC electricity with a 3-phase induction motor (thus avoiding the cost of using an inverter).
The 1000mm square fresnel lens is available as part number BHPA1000-2 from http://www.bhlens.com/fresnel_lens.aspx
The higher the difference in temperature between the heat source and the heat sink, the greater the theoretical efficiency. Convection and conduction losses are insignificant at high concentration ratio. Since practical selective coatings only work up to 800K, they are irrelevant for high temperature concentrators.
run 'fresnelx w1000 g2500 l1000 s100 r51 c50:10 c97:10' first to calculate concentration levels
fresnelx w1000 g2500 l1000 s100 r51 13531 2677 v.2
887.65W/m2 refractive index at 589.2nm(1.492) m(20), eff(99.990%) SunHalfAngle(0.26657o)
Total input energy 888 Watts
Acrylic Fresnel Lens Width 1000mm x 0.150mm, Area 1.00m2, Focal Length 1000mm (f/1.000), 2500 grooves
Slice Radius Power Tot Tot QEff Ix Ax Area UV Blue Green Red NIR IR
390 492 622 760 1110 4000
mm W W % % cm2 % % % % % %
0 564.190 887.65 888 100.0 50.8 1.0 1.0 10000.00 5.6 13.0 19.6 18.2 27.5 16.0
Cell 1 Concentration Level 3531.000x, distance from lens 983.171mm, 0.9832f, nominal radius 9.495mm
1 0.200 17.57 18 2.0 65.9 157450.4 157450.4 0.00 8.3 7.5 0.0 17.4 66.8 0.0
2 0.400 18.06 36 4.0 66.3 53956.7 79839.5 0.00 8.0 7.3 0.0 17.2 67.4 0.0
3 0.600 18.19 54 6.1 66.7 32606.3 53599.7 0.01 8.0 7.4 0.0 17.4 67.2 0.0
4 0.800 18.40 72 8.1 67.2 23570.4 40462.2 0.01 7.9 7.4 0.0 18.0 66.7 0.0
5 1.000 18.05 90 10.2 67.5 17975.6 32367.2 0.01 8.0 7.7 0.0 21.2 63.0 0.0
6 1.200 17.42 108 12.1 67.8 14196.1 26814.5 0.01 8.3 8.2 0.0 28.7 54.8 0.0
7 1.400 16.76 124 14.0 67.2 11556.3 22766.6 0.02 8.7 8.8 0.0 35.1 47.4 0.0
8 1.600 17.24 142 16.0 68.7 10303.5 19845.6 0.02 8.4 8.9 0.0 32.3 50.4 0.0
9 1.800 18.46 160 18.0 71.3 9735.0 17723.7 0.02 7.9 8.7 0.0 28.3 55.1 0.0
10 2.000 19.25 179 20.2 73.5 9084.4 16082.3 0.02 7.5 8.7 0.0 25.7 58.0 0.0
11 2.200 20.04 199 22.5 75.7 8553.4 14775.6 0.03 7.2 8.9 0.0 24.0 59.8 0.0
12 2.400 19.04 218 24.6 66.4 7419.0 13600.5 0.03 7.6 10.0 0.1 25.2 51.6 5.4
13 2.600 19.39 238 26.8 51.5 6952.8 12617.1 0.03 7.5 10.5 0.7 23.2 34.6 23.5
14 2.800 21.27 259 29.2 37.2 7061.3 11851.8 0.03 6.8 10.3 1.1 19.5 21.4 41.0
15 3.000 20.76 280 31.5 31.6 6417.7 11151.4 0.04 6.9 11.4 1.5 18.6 14.8 46.7
16 3.200 16.95 297 33.4 36.8 4903.3 10394.8 0.04 8.4 15.3 2.4 21.5 16.0 36.5
17 3.400 21.78 319 35.9 27.9 5916.1 9883.4 0.04 6.5 13.1 2.3 16.1 11.2 50.8
18 3.600 19.18 338 38.1 30.7 4912.1 9346.4 0.04 7.3 16.6 3.1 17.1 11.5 44.4
19 3.800 15.78 354 39.8 36.6 3823.7 8780.4 0.05 8.8 22.8 4.2 19.3 12.7 32.2
20 4.000 14.76 368 41.5 38.7 3392.3 8255.0 0.05 9.3 28.1 5.1 18.8 12.3 26.4
21 4.200 14.49 383 43.1 39.9 3169.4 7782.2 0.05 9.3 34.3 5.7 17.5 11.4 21.8
22 4.400 15.21 398 44.8 40.2 3170.9 7372.6 0.05 8.8 42.0 6.0 15.0 9.9 18.4
23 4.600 20.87 419 47.2 41.7 4157.8 7099.1 0.06 5.7 53.2 8.2 11.7 8.2 12.9
24 4.800 28.99 448 50.5 47.4 5530.1 6971.0 0.06 1.6 31.5 23.2 16.0 14.7 13.0
25 5.000 25.46 473 53.3 48.0 4657.4 6789.7 0.06 1.7 24.8 25.6 17.4 16.3 14.2
26 5.200 23.66 497 56.0 48.4 4159.1 6591.2 0.06 1.8 21.7 27.0 17.8 17.0 14.6
27 5.400 22.24 519 58.5 48.6 3761.5 6385.5 0.07 1.9 19.2 28.3 17.9 17.7 15.0
28 5.600 21.18 540 60.9 48.8 3451.9 6179.7 0.07 2.0 17.7 29.4 17.4 18.2 15.3
29 5.800 20.27 561 63.2 49.0 3188.4 5976.9 0.07 2.0 16.0 30.6 17.3 18.6 15.5
30 6.000 19.41 580 65.4 49.1 2948.7 5778.4 0.07 2.1 14.8 32.0 16.4 19.0 15.7
31 6.200 18.71 599 67.5 49.1 2749.6 5586.2 0.08 2.1 13.7 33.8 15.4 19.1 15.9
32 6.400 18.10 617 69.5 49.1 2575.6 5400.9 0.08 2.2 12.8 36.0 13.7 19.2 16.1
33 6.600 17.31 634 71.4 49.1 2388.0 5221.1 0.08 2.2 11.1 36.6 14.2 19.4 16.4
34 6.800 16.85 651 73.3 49.0 2254.8 5049.2 0.08 2.3 10.8 36.7 14.3 19.4 16.5
35 7.000 16.21 667 75.2 49.0 2105.8 4883.4 0.09 2.3 9.5 37.1 14.8 19.5 16.8
36 7.200 15.75 683 76.9 48.9 1989.2 4724.8 0.09 2.3 8.9 37.3 15.0 19.4 17.0
37 7.400 15.21 698 78.7 48.8 1868.4 4572.5 0.09 2.4 7.8 37.7 15.4 19.5 17.3
38 7.600 14.76 713 80.3 48.6 1764.5 4426.7 0.09 2.4 7.1 37.8 15.7 19.5 17.5
39 7.800 14.29 727 81.9 48.5 1664.3 4286.8 0.10 2.5 6.2 38.2 16.0 19.5 17.8
40 8.000 13.90 741 83.5 48.4 1577.0 4153.0 0.10 2.5 5.4 38.4 16.3 19.5 18.0
41 8.200 13.48 755 85.0 48.6 1492.0 4024.8 0.10 2.5 4.5 38.6 16.6 19.8 18.1
42 8.400 13.17 768 86.5 48.7 1422.1 3902.3 0.10 2.5 3.7 38.7 16.8 20.1 18.1
43 8.600 12.81 781 87.9 48.9 1350.6 3785.0 0.11 2.5 2.9 38.9 17.0 20.5 18.1
44 8.800 12.49 793 89.4 49.2 1287.5 3672.8 0.11 2.5 2.3 39.2 17.3 20.8 17.9
45 9.000 12.14 805 90.7 49.5 1223.2 3565.2 0.11 2.5 1.6 39.4 17.6 21.3 17.7
46 9.200 11.80 817 92.1 49.8 1162.0 3461.8 0.11 2.5 0.8 39.7 17.9 21.7 17.4
47 9.400 11.47 829 93.3 50.1 1106.1 3362.6 0.12 2.5 0.1 39.9 18.2 22.1 17.1
48 9.600 11.15 840 94.6 50.5 1052.0 3267.4 0.12 2.5 0.0 39.6 18.5 22.6 16.8
49 9.800 10.84 851 95.8 50.8 1001.7 3175.8 0.12 2.5 0.0 39.1 18.8 23.1 16.5
50 10.000 10.55 861 97.0 51.2 955.5 3087.9 0.12 2.5 0.0 38.7 19.1 23.4 16.2
Cell 2 Concentration Level 677.000x, distance from lens 1038.433mm, 1.0384f, nominal radius 21.684mm
run 'fresnelx w1000 g2500 l1000 s100 r51 13531 28570.214' to calculate the radius and placement of the mirror. 8570.214 = (1000 / (1000 - (1038.433 + 983.171) / 2)) ^ 2
Visualisation of tracking error from 0 to 0.5 degree in step of 0.01 degree. The absorber is a double ended cone with a radius of 10mm and end to end height of 10mm. The heat transfer liquid will enter from the front center and exit at the back center. The image at the top right corner is the reflection of the back of the cone. The average concentration level over the entire absorber is 1380 = 1e6 * 0.97 / (2 * pi * 10 * sqrt(10^2 + 5^2))
StarRotor (Brayton Cycle). 45-60% efficiency. Have working compressor at 80% efficiency.
Stirling Energy Systems. SunCatcher, 25kW solar dish Stirling Cycle. 31% efficiency.
Capstone Turbine. Externally fired 65kW C65 Capstone Microturbine (Brayton Cycle). 29% efficiency.
Stirling Biopower. 38kW Stirling engine. 27-28% efficiency.
Infinia 3kW PowerDish Stirling Engine. 17% efficiency.
CSIRO 200kW Brayton Cycle Solar Tower. 11% efficiency.
BSR Solar Technologies. Medium Temperature Stirling Technology.
Solar Engine Corporation. Dual Shell Stirling Engine.
International Automated Systems (Point focus fresnel lens concentrator)
GrafTech. Synthetic graphite for thermal energy storage.
Last updated: 20 February 2011