Sunreign Reference: ParabolicThrough

Loss	Open trough	Closed trough	Comments
Cover reflection loss	1	0.95	Open trough has no cover. Closed trough has a cover with anti-reflection treatment.
Mirror reflectivity	0.93	0.93	Equal quality mirrors.
Glass tube reflection loss	0.95	0.95	Equal quality tubes, treated anti-reflection.
Intercept factor	0.98	0.98	Equal optical precision supposed.
Receiver absorptivity	0.95	0.95	Equal quality receiver surface.
Incidence angle cos effect	0.82	0.99	Open trough is horizontally installed, latitude 40°. Closed trough is optimally tilted north-south axis, with tilting angle adjusted 2 or 4 times a year.
End and join loss	0.9	1	Open trough has end loss and loss on receiver supporting structure. No such losses for closed trough.
Glass tube multiple travel	0.995	0.99	A small amount of light travels several times through the glass tube. This is slightly more important for the closed trough due to a glass tube of larger diameter.
Dust loss	0.94	0.98	Light to an open trough travels 3 times through dust-coverable surfaces. Only once for closed trough.
Row-to-row shading	0.98	0.95	Closed trough deliberately adopts a more condensed row-to-row distance, prompted by its lower cost, in order to reduce land use and piping cost. The data result from a computer simulation taking into account the atmospheric attenuation and the Sun's angle.
Thermal capacity	0.95	0.99	The big open trough has a thicker receiver, hence a higher thermal capacity per unit aperture area. Heat corresponding to the thermal capacity is lost after sunset or cloud coverage. The thermal capacity is 0.36Wh/m²·K, or 126Wh/m² for a temperature elevation of 350°C. Assuming an average collection of 2.5kWh/m² per period of sunshine, the loss represents 5%. This loss is 6 times less for the smaller closed trough.
Efficiency before thermal loss	52.8%	70.6%	Efficiencies above are multiplied; loss below is subtracted.
Thermal loss	10%	10%	Assume 800W average incoming light intensity and 80W/m² thermal loss for both cases.
Final efficiency	42.8%	60.6%	This is the efficiency with respect to direct normal insolation.

Sunreign Reference : ParabolicThrough