Thermal Performance of a Hybrid Photovoltaic-Thermal Collector with a Modified Absorber Presenter: Sameer Simms University of the West Indies Location: Palermo, Italy Date: November 25, 2015
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Thermal Performance of a Hybrid Photovoltaic-Thermal Collector
with a Modified Absorber
Presenter: Sameer SimmsUniversity of the West IndiesLocation: Palermo, ItalyDate: November 25, 2015
Outline of Presentation
Background of Jamaica
Introduction
Prototype Design and Components
Thermal Data Collection
Hydraulic Circuit Configurations
Results of Model Validation
Results of Thermal Assessment
Conclusion
Future Work for Improvement
Background of Jamaica
Small island developing state in the Caribbean (Area: 10,991 km²)
Population:2.7 million, GNI per capita:~€4,900 [3]
Heavy dependence on imported oil which is used to satisfy most of
the annual 4.1 TWh electricity demand [2]
Major industries are tourism, mining, agriculture, and services
The island is rich in natural resources (solar, wind, biomass,etc)
An area less than 3km2 (0.03% of total) receives enough energy from
sunlight to satisfy electricity demand
(Image source: http://www.wherevent.it/files/getbyid/jamaica_flag,554.png)
Introduction
Birth of research in the 1970's [4]
Hybrids categorized based on thermal fluid and geometry
i.e., air or liquid, flat plate or concentrating
Offer cooler operating temperatures for PV cells. This is
advantageus because PV cells have a negative
temperature coefficient of ~0.5%/oC [1]
Reduces the space requirements for heat and
electricity production
Hybrids have not been able to match the thermal
performance of flat-plate collectors
Prototype Design and Components
A flat-plate, water-based, sheet-and-tube collector was built from scratch. Several mechanical issues were encountered which resulted in a higher thermal resistance due to non-smooth contact surfaces.
Some specifications:
Dimensions: 0.71mx0.20m
# of PV cells: 7
PV cell type: polycrystalline
T/E Ratio*: 1.89
Riser diameter: 0.5”
Riser type: copper
Sheet type: aluminum
Picture of the solar energy collectors* Thermal to electrical energy ratio
Thermal Data Collection For model validation, data was collected on January 23, 2015 between
the hours of 9:58am and 1:52pm.
Glass, water inlet, and water outlet temperatures were recorded.
To determine the correlation coefficients, 235 points were used.
For thermal performance, data was collected during June 15-20, 2015.
Type K thermocouples were used to measure absorber and PV cell
temperatures.
Pipe-plug thermocouples were used to measure fluid temperatures.
An analog water flow meter was used to measure flow rate.
Fluid movement was achieved using a low-powered DCpump.
Data was recorded using a portable analog/digital datalogger
Thermal Data Collection
Picture of some measuring equipment used to measure and record data on the roof of the Department of Physics, Mona Campus, UWI (18.00N, 76.75W)
Hydraulic Circuit Configurations
Parallel Series (Booster)
Hydraulic Circuit Configurations
Hybrid-only SWH-only
Results of Model Validation
Both water temperatures were overestimated in the last hour. Glass temperature was underestimated for a majority of the period. Possible
overestimation of heat loss from glass to environment.
• correlation coefficient was 90.3%, 93.4%, and 96.3%• Real/model average temperature was 31.85oC/32.22oC, 32.17/32.27oC, and
41.07oC/39.66oC.
Weather data was fed into a 2D dynamic numerical model. In order of inlet, outlet, and glass:
Variation of the water inlet, water outlet, and glass temperatures for the real and simulated prototypes (in order, left to right).
Results of Thermal Assessment
Average and maximum data for parallel configuration
Collector Max/ oC Avg/ oC
PV 62.8 53.3
PVT 55.5 49.4
SWH 67.2 60.4
Inlet 46.1 41.3
PVT outlet 47.5 43.1SWH outlet 48.9 44.3
Tank 47.4 42.1
The hybrid's average fluid outlet temperature was only 1.2oC less than that of the SWH. This is a really small difference.
Temperature Variation for Parallel Configuration
Results of Thermal Assessment
Average and maximum data for hybrid-only configuration
Collector Max/ oC Avg/ oC
PV 65.8 55.9
PVT 56.4 50.6
SWH 87.9 72.5
Inlet 44.6 40.3
PVT outlet 48.0 41.8SWH outlet - -
Tank 45.0 40.2
The hybrid's average PV celltemperature was 5.3oC cooler than that of the PV module. Also, the maximum tank temperature was 45oC.
Temperature Variation for Hybrid-only Configuration
Results of Thermal Assessment
Average and maximum data for SWH-only configuration
Collector Max/ oC Avg/ oC
PV 62.5 52.5
PVT 61.7 53.0
SWH 67.0 58.9
Inlet - -
PVT outlet - -
SWH outlet 48.9 43.8
Tank 47.6 42.9
Temperature Variation for SWH-only Configuration
The SWH was able to heat water up to 47.6oC, 2.6oC more than the hybrid managed. Also, it is observed that in stagnation, the hybrid has similar temeperature to the PV module.
Results of Thermal Assessment
Collector Max/ oC Avg/ oC
PV 59.5 51.5
PVT 51.9 47.0
SWH 65.8 57.2
Inlet 47.7 42.6
PVT outlet 49.0 43.7
SWH outlet 50.5 44.8
Tank 49.1 43.7
Average and maximum data for series configuration
Temperature Variation for Series Configuration
This configuration produced the highest tank temperature of 49.1oC. This is just slightly above the threshold for the growth of Legionella bacteria.
Conclusion
The numerical model performed fairly well with correlation coefficients upwards of 90% with real data.
The hybrid unit was able to heat water in the reservoir up to 45.0oC while the flat plate collector managed 47.6oC.
The hybrid unit operated, on average, 5oC cooler than the PV module which corresponds to a 2.5% increase in electricity output (theoretical).
In booster configuration, the tank temperatures went up to a maximum of 49.1oC just exceeding the threshold for Legionella growth.
The hybrid collector had comparable thermal performance to the flat plate collector. A professionally-made prototype has the potential for better thermal performance.
Future Work for Improvement
To further increase the thermal performance of the hybrid unit, future work will include the use of:
• glass with anti-reflective technology to reduce optical losses
• Thicker absorber to improve lateral heat flow• Improved manufacturing method to reduce thermal
resistance• Increased insulation to reduce heat losses
Larger prototypes will be built and tested at a residential location
Electrical data will be measured and recorded.
References
1)Ibrahim, A.; Othman, M. Y.; Ruslan, M. H.; Alghoul, M. A.; Yahya, M.;Zaharim, A. & Sopian, K. “Performance of Photovoltaic ThermalCollector (PVT) With Different Absorbers Design”. WSEASTransactions on Environment and Development, vol. 5, pp. 321–330,2009.
2)“An Overview of Jamaica's Electricity Sector.“ Internet:http://mstem.gov.jm/?q=overview-jamaicas-electricity-sector, [Aug. 1, 2015].
3) “Jamaica:World Development Indicators.“ Internet:http://http://data.worldbank.org/country/jamaica, [Aug. 1, 2015].
4)H Zondag. Flat-plate PV-Thermal collectors and systems: A review. Renewable and Sustainable Energy Reviews, 12(4):891–959, May 2005. ISSN 13640321. doi: 10.1016/j.rser.2005.12.012. URL http://linkinghub.elsevier.com/ retrieve/pii/S1364032107000020.
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