non-tracking solar thermal technology and its applications bruce johnston uc solar university of...

Non-tracking Solar Thermal Non-tracking Solar Thermal Technology and Its Technology and Its

ApplicationsApplications

Bruce JohnstonBruce JohnstonUC SolarUC Solar

University of California, MercedUniversity of California, Mercedbombdog@sbcglobal.netbombdog@sbcglobal.net

ObjectivesObjectives

The objective was to develop a non-The objective was to develop a non-tracking solar thermal system that tracking solar thermal system that would:would:– Operate at relatively high temperaturesOperate at relatively high temperatures– Be easily adapted for practical useBe easily adapted for practical use– Have a fairly low manufacturing costHave a fairly low manufacturing cost

ResultResult

XCPC design using MGVTXCPC design using MGVT Relies on non-imaging opticsRelies on non-imaging optics 60 degree acceptance angle60 degree acceptance angle Consistently operates at 200CConsistently operates at 200C Has the potential to operate at even Has the potential to operate at even

higher temperatures (approaching higher temperatures (approaching 400C)400C)

Significance of a Non-tracking Significance of a Non-tracking SystemSystem

CostCost– Trackers are priced in the thousands of Trackers are priced in the thousands of

dollarsdollars– Each tracker requires a power supplyEach tracker requires a power supply

Ease of MaintenanceEase of Maintenance– Few moving partsFew moving parts– Easier to keep cleanEasier to keep clean

StabilityStability– Sturdy, well anchored frameSturdy, well anchored frame

55

slider

R

Collector ShapeCollector Shape

2R/sin

Tube DesignTube Design

Standard Tube-in-tube designStandard Tube-in-tube design– Commercially availableCommercially available– ReliableReliable– Replacement rate is 2%-4% per yearReplacement rate is 2%-4% per year

U-tube designU-tube design– Designed by our groupDesigned by our group– Slightly better performance than the Slightly better performance than the

tube-in-tube designtube-in-tube design

Tube-in-tube ConfigurationTube-in-tube Configuration

1 Outer Glass1 Outer Glass 2 Absorber2 Absorber 3 Seal3 Seal 4 Outlet Channel4 Outlet Channel 5 Inlet Channel5 Inlet Channel

U-tube ConfigurationU-tube Configuration

Collector OrientationCollector Orientation

East WestEast West– Collectors are arranged horizontally or Collectors are arranged horizontally or

left to rightleft to right– Better performing than North South Better performing than North South

configuration at higher temperaturesconfiguration at higher temperatures North SouthNorth South

– Collectors are arranged vertically or up Collectors are arranged vertically or up and downand down

– Easy maintenance is a trade off for Easy maintenance is a trade off for slightly lower performanceslightly lower performance

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

-80.000 -60.000 -40.000 -20.000 0.000 20.000 40.000 60.000 80.000

Azimuth Angle

Effi ciency (PSolRad)

Efficiency with 60 degree Efficiency with 60 degree Acceptance AngleAcceptance Angle

Parabolic Trough Parabolic Trough ImprovementsImprovements

Angular tolerance could be increased from 0.5° to 2.0°

Thermodynamic efficiency could improve significantly

Overall system costs will be reduced

Vacuum Tube Vacuum Tube ImprovementsImprovements

Improve tube designImprove tube designBetter flow path designBetter flow path design

Better selective coatingsBetter selective coatings

Better vacuum sealsBetter vacuum seals

Selective Coating Selective Coating ImprovementImprovement

Low Emissivity (< 0.07 at 400C)Low Emissivity (< 0.07 at 400C) High Absorptivity (> 0.96)High Absorptivity (> 0.96) Low reflectance (Low reflectance (≈0) at wavelengths <= ≈0) at wavelengths <=

2 microns2 microns High reflectance (High reflectance (≈1) and wavelengths > ≈1) and wavelengths >

2 microns2 microns Stability in a vacuum at 400CStability in a vacuum at 400C

ApplicationsApplications

Process heat (e.g. to dry fruit)Process heat (e.g. to dry fruit) Desalination processesDesalination processes Heating and cooling of structuresHeating and cooling of structures

– Absorption chillersAbsorption chillers Single effectSingle effect Double effectDouble effect

Solar Cooling Demonstration Solar Cooling Demonstration ProjectProject

UC Solar ProjectUC Solar Project First of its kind in the USAFirst of its kind in the USA Student designedStudent designed 23.5 KW system23.5 KW system 6.5 ton double effect absorption 6.5 ton double effect absorption

chillerchiller Cools a 700 sq. ft. structureCools a 700 sq. ft. structure

UC Solar Absorption ChillerUC Solar Absorption Chiller

Broad 6.5 ton unitBroad 6.5 ton unit Hot water or gas Hot water or gas

drivendriven COP approx. 1.2COP approx. 1.2 Made in ChinaMade in China

Hot Water or Steam Hot Water or Steam Absorption ChillersAbsorption Chillers

COPCOP

Single-effect chiller..............0.60 to 0.75Single-effect chiller..............0.60 to 0.75

– 90C-150C90C-150C

Double-effect chiller.............1.19 to 1.35Double-effect chiller.............1.19 to 1.35– > 150C > 150C

23.5 KW Collector Array 23.5 KW Collector Array

Building and ArrayBuilding and Array

12’x57’ Office (approx 700 sq. ft.)12’x57’ Office (approx 700 sq. ft.) 23.5 KW array (52 sq. meters)23.5 KW array (52 sq. meters)

Key Project MembersKey Project Members

Dr. Roland WinstonDr. Roland Winston Kevin BalkowskiKevin Balkowski Heather PoiryHeather Poiry

QuestionsQuestions

Bruce JohnstonBruce Johnston bombdog@sbcglobal.netbombdog@sbcglobal.net bjohnston3@ucmerced.edubjohnston3@ucmerced.edu 209-228-2907209-228-2907