Transcript Slide 1

Experiment Design of a
Photovoltaic/Thermal Hybrid
System
Maria Browne
Department of Civil, Structural and Environmental Engineering,
Trinity College Dublin
You Supervisors’ Names Here
Dr. Sarah McCormack
Prof. Brian Norton
15th February 2013
Effect of Temperature on Photovoltaics
• Photovoltaic (PV) cells produce thermal energy (85%) along with
electrical energy (15%) when exposed to sunlight
• Temperature effects are more pronounced in silicon solar cells,
excess of heat causes the PV cell to become less efficient (a
reduction of 0.5%/K)
• Research suggests in organic and some plastic solar cells an
increase in temperature increases their performance
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Phase Change Materials
• Phase Change Materials (PCM) can be used for thermal
control in building integrated photovoltaic, thereby
maintaining efficiency
• PCM can absorb large amounts of heat without changing
temperature-latent heat
• Various types of PCM; organic (fatty acids, paraffin wax),
inorganic (salt) and eutectic (mixture of compounds)
• The type of PCM applied to a system depends on the
following properties;
-phase change temperature (ºC)
-enthalpy of phase change (J)
-heat capacity (J/Kg)
-thermal conductivity (W/m K)
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Use of Phase Change Materials for Thermal
Control in Building Integrated Photovoltaics
• Previous research includes regulating the temperature of PV
cells by integrating PCM to maintain PV efficiency (Hasan,
2010)
• I am concentrating on thermal energy stored in the PCM and
using it for a suitable application e.g. water heating, space
heating
• Designed and currently installing a PV/thermal hybrid system
on the roof of Kevin Street, DIT
• Electrical energy is generated by the PV, thermal energy is
transferred from the PV to PCM and this thermal energy will
then be used to heat water
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Use of Phase Change Materials for Thermal
Control in Building Integrated Photovoltaics
Thermosyphon,
through which
the water will
flow
Thermosyphon
inserted in the
semi-complete
container
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Completed
container
attached to the
solar panel
Use of Phase Change Materials for Thermal
Control in Building Integrated Photovoltaics
• Phase Change material which will be used is a eutectic,
comprising of fatty acids, capric (75%) and palmitic (25%)
• Shown to be thermally stable
• Below is a table showing the properties
Capric/Palmitic Acid Properties
Melting point
22.4 ºC
Heat of Fusion
195 kJ/kg
Thermal Conductivity
0.139 W/ mºC (liquid)
0.143 W/ mºC (solid)
Specific Heat Capacity
2.4 KJ/kgK (liquid)
2.2 KJ/kgK (solid)
Density
0.79 kg/m³ (liquid)
0.87 kg/m³ (solid)
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What values are being analysed in the
system?
• The transfer of heat across the system will be measured
using a series of K-type thermocouples
• Twisted K-type thermocouples will be used
– back and front of the PV
– in the water cylinder
– ambient temperatures
• Stainless steel sheath thermocouples will be used to
measure
– the temperature of the water flow in the pipes
– The temperature of the PCM inside the container
• A thermal paste has been applied to the back of the PV
and the container to enhance thermal contact
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What values are being analysed in the
system?
• The following are measured in the electrical system
–
–
–
–
PV voltage
PV current
Battery voltage
Battery current
• Other values being
measured are
– Rate of flow
– Solar radiation
– Spectral radiation
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Use of Phase Change Materials for Thermal
Control in Building Integrated Photovoltaics
• Predicted Results
• Regulate the temperature of the system
• An increase in the temperature of the water in
the system
• Maintained efficiency of the thermal controlled
system
• Assess the value of heat loss to the surroundings
• Suggest ways to optimise the system
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Image of the complete
thermal/hybrid system
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Thank you for your attention.
Any questions?
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