Non-tracking Solar Thermal Technology and Its Applications

1. Non-tracking Solar Thermal Technology and Its Applications Bruce Johnston UC Solar University of California, Merced bombdog@sbcglobal.net

2. Objectives • The objective was to develop a non-tracking solar thermal system that would: • Operate at relatively high temperatures • Be easily adapted for practical use • Have a fairly low manufacturing cost

3. Result • XCPC design using MGVT • Relies on non-imaging optics • 60 degree acceptance angle • Consistently operates at 200C • Has the potential to operate at even higher temperatures (approaching 400C)

4. Significance of a Non-tracking System • Cost • Trackers are priced in the thousands of dollars • Each tracker requires a power supply • Ease of Maintenance • Few moving parts • Easier to keep clean • Stability • Sturdy, well anchored frame

5.  2R/sin slider R Collector Shape

6. Tube Design • Standard Tube-in-tube design • Commercially available • Reliable • Replacement rate is 2%-4% per year • U-tube design • Designed by our group • Slightly better performance than the tube-in-tube design

7. 1 Outer Glass 2 Absorber 3 Seal 4 Outlet Channel 5 Inlet Channel Tube-in-tube Configuration

8. U-tube Configuration

9. Collector Orientation • East West • Collectors are arranged horizontally or left to right • Better performing than North South configuration at higher temperatures • North South • Collectors are arranged vertically or up and down • Easy maintenance is a trade off for slightly lower performance

11. Efficiency with 60 degree Acceptance Angle

12. Parabolic Trough Improvements • Angular tolerance could be increased from 0.5° to 2.0° • Thermodynamic efficiency could improve significantly • Overall system costs will be reduced

13. Vacuum Tube Improvements • Improve tube design • Better flow path design • Better selective coatings • Better vacuum seals

14. Selective Coating Improvement • Low Emissivity (< 0.07 at 400C) • High Absorptivity (> 0.96) • Low reflectance (≈0) at wavelengths <= 2 microns • High reflectance (≈1) and wavelengths > 2 microns • Stability in a vacuum at 400C

15. Applications • Process heat (e.g. to dry fruit) • Desalination processes • Heating and cooling of structures • Absorption chillers • Single effect • Double effect

16. Solar Cooling Demonstration Project • UC Solar Project • First of its kind in the USA • Student designed • 23.5 KW system • 6.5 ton double effect absorption chiller • Cools a 700 sq. ft. structure

17. UC Solar Absorption Chiller • Broad 6.5 ton unit • Hot water or gas driven • COP approx. 1.2 • Made in China

18. Hot Water or Steam Absorption Chillers • COP • Single-effect chiller..............0.60 to 0.75 • 90C-150C • Double-effect chiller.............1.19 to 1.35 • > 150C

19. 23.5 KW Collector Array

20. Building and Array • 12’x57’ Office (approx 700 sq. ft.) • 23.5 KW array (52 sq. meters)

21. Dr. Roland Winston Kevin Balkowski Heather Poiry Key Project Members

22. Questions • Bruce Johnston • bombdog@sbcglobal.net • bjohnston3@ucmerced.edu • 209-228-2907