Archimedes Solar Energy Laboratory (ASEL)
Experimental investigation of the performance of a Parabolic Trough Collector (PTC) installed in Cyprus
Soteris A. Kalogirou Department of Mechanical Engineering and Materials Sciences and Engineering Parabolic Trough Collectors • Consists of a parabolic mirror and a receiver pipe
• Most mature system because of the SEGS systems installed in California since the mid eighties
Archimedes Solar Energy Laboratory (ASEL) System installed • The first of its kind in Cyprus • Problem to find a manufacturer selling a small system • The system most probably to be installed for CSP in Cyprus • Recently installed at Archimedes Solar Energy Laboratory-Various problems as assembly was done locally with distance support from manufacturer • Collector to be used for testing high performance absorber materials • To be used for low temperature cycles to produce power (ORC)
Archimedes Solar Energy Laboratory (ASEL) NEP-Solar Collector • The collector length = 12.2 m and consists of: ▫ galvanized steel mounts, ▫ lightweight, stiff and precise parabolic reflector panels manufactured from reinforced polymeric material, ▫ a structurally efficient galvanized steel torque tube, ▫ a tubular receiver and ▫ an accurate solar tracking system. • Characteristics are shown in the next Table
Archimedes Solar Energy Laboratory (ASEL) Collector Specifications Parameter Value Collector Length (6 sections) 1993 mm Collector width 1208 mm Parabola focal distance 647 mm Mirror reflectivity 93.5% Receiver material Stainless steel 304 L Receiver external diameter 28 mm Receiver internal diameter 25 mm Glass tube transmittance 0.89 Selective coating absorptance 0.93 Selective coating emittance 0.18 Maximum operating temperature 200°C Collector Photos – Focus position
Archimedes Solar Energy Laboratory (ASEL) Collector Photos – Parking position
Use of flexible connections
Tracking motor – limit switches Archimedes Solar Energy Laboratory (ASEL) Hydraulic Connections Hot water outlet
Note: For simplicity valves are not shown Hot water storage tank AUX (300 lt) Outlet Pump
From collector
To collector Cold water inlet AUX Inlet Expansion tank Archimedes Solar Energy Laboratory (ASEL) Photo of Hydraulic Circuit
Hot water outlet pipe
Hot water storage tank
Flow switch Solar pump
Expansion tank
Archimedes Solar Energy Laboratory (ASEL) Collector Thermal Efficiency Test
•
Archimedes Solar Energy Laboratory (ASEL) Thermal Efficiency Equations • At steady state conditions the instantaneous thermal efficiency is given by: mc (T T ) p o i AG aB • The useful energy from the collector is given by:
Qu mc p (T o T i )
• The useful energy collected from a concentrating solar collector is also given by:
Qu F R G B o A a A r U L (T i T a )
Archimedes Solar Energy Laboratory (ASEL) • Moreover, the thermal efficiency is obtained by
dividing Qu by the energy input (AaGB). Therefore: FU(TT) F R L i a Ro CG B • This plots as: η Intercept = FRηο
Slope = -FRUL/C
ΔΤ/GB Archimedes Solar Energy Laboratory (ASEL) • The heat loss coefficient UL in previous Equation is not constant but is a function of collector inlet and ambient temperatures. Therefore:
FR U L c 1 c 2 (T i T a )
• So Qu becomes:
2 Qu F R G Boa A A r1i c (T T a ) A r2i c (T T a ) (7)
• And the efficiency is given by second order performance equation: 2 c1 (T i T a ) c 2 (T i T a ) FRo CGBB CG
Archimedes Solar Energy Laboratory (ASEL) Results of Tests – First Order Performance Curve
0.8 y = -0.4832x + 0.6481 0.7
0.6
0.5
0.4 T
0.3 0.6481 0.4832 Thermal efficiency 0.2 GB
0.1
0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
2 (Ti-Ta)/GB [m °C/W]
Archimedes Solar Energy Laboratory (ASEL) Results of Tests – First Order Performance Curve
0.8 y = -2.7069x2 + 0.1887x + 0.6289 0.7 R2 = 0.9739 0.6
0.5
0.4 TT2 0.6289 0.1887 2.7069 0.3
GGBB Thermal efficiency 0.2
0.1 The circles shown represent the values given by the manufacturer 0 0 0.05 0.1 0.15 0.2 0.25 0.3
2 (Ti-Ta)/GB [m °C/W]
Archimedes Solar Energy Laboratory (ASEL) Conclusions • The collector installed at the Archimedes Solar Energy Laboratory is presented as well as the complete plumbing system. • The measurements performed concern the instantaneous values of solar beam radiation, ambient temperature, collector inlet and outlet temperatures, and mass flow rate. • The basic parameters obtained from the performance testing are the intercept and slope of the collector performance line. • A second order performance curve is also obtained from the same results. • Both show a satisfactory performance. • The results are considered as preliminary and more testing is planned in the next few months.
Archimedes Solar Energy Laboratory (ASEL) Archimedes Solar Energy Laboratory
Archimedes Solar Energy Laboratory (ASEL) Indoor testing of collectors and components • Testing of solar systems and components under controlled conditions • Consists of 20 lamps 575 W each-light close to solar spectrum • Can get up to 1200 W/m2 • Can move up and down and rotates from 0-90o • Individual lamp control and dimming control
Archimedes Solar Energy Laboratory (ASEL) Archimedes Solar Energy Laboratory (ASEL)
Thank you for your attention…. Any questions please….
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