Experimental investigation of the performance of a Parabolic Trough Collector (PTC) installed in Cyprus

Transcription

1 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

2 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

3 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)

4 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

5 Collector Specifications Parameter Collector Length (6 sections) Collector width Parabola focal distance Mirror reflectivity Receiver material Receiver external diameter Receiver internal diameter Glass tube transmittance Selective coating absorptance Selective coating emittance Maximum operating temperature Value 1993 mm 1208 mm 647 mm 93.5% Stainless steel 304 L 28 mm 25 mm C

6 Collector Photos Focus position

7 Collector Photos Parking position Use of flexible connections Tracking motor limit switches

8 Hydraulic Connections Hot water outlet Hot water storage tank (300 lt) Note: For simplicity valves are not shown AUX Outlet Pump Cold water inlet Expansion tank From collector To collector AUX Inlet

9 Photo of Hydraulic Circuit Hot water outlet pipe Hot water storage tank Flow switch Solar pump Expansion tank

10 Collector Thermal Efficiency Test

11 Thermal Efficiency Equations At steady state conditions the instantaneous thermal efficiency is given by: mc p(to T i) AG The useful energy from the collector is given by: The useful energy collected from a concentrating solar collector is also given by: Q mc (T T ) a B u p o i Q F G A A U (T T ) u R B o a r L i a

12 Moreover, the thermal efficiency is obtained by dividing Q u by the energy input (A a G B ). Therefore: FR U L(Ti T a ) FR o CG B This plots as: η Intercept = F R η ο Slope = -F R U L /C ΔΤ/G B

13 The heat loss coefficient U L in previous Equation is not constant but is a function of collector inlet and ambient temperatures. Therefore: So Q u becomes: FR UL c1 c 2(Ti T a) 2 Qu FR GB oaa Arc 1(Ti T a ) Arc 2(Ti T a) (7) And the efficiency is given by second order performance equation: c 1(Ti T a ) c 2(Ti T a ) FR o CG CG B B 2

14 Thermal efficiency Results of Tests First Order Performance Curve y = x T G B (Ti-Ta)/G B [m 2 C/W]

15 Thermal efficiency Results of Tests First Order Performance Curve y = x x R 2 = T T G G The circles shown represent the values given by the manufacturer B B 2 (Ti-Ta)/G B [m 2 C/W]

16 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.

17 Archimedes Solar Energy Laboratory

18 Indoor testing of collectors and 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/m 2 Can move up and down and rotates from 0-90 o Individual lamp control and dimming control components

19 Archimedes Solar Energy Laboratory (ASEL) Thank you for your attention. Any questions please.