Experiment Design of a Photovoltaic/Thermal Hybrid System

Maria BrowneDepartment of Civil, Structural and Environmental Engineering,

Trinity College DublinYou Supervisors’ Names Here

Dr. Sarah McCormackProf. 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

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• 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)

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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Thermosyphon, through which the water will

flow

Thermosyphon inserted in the semi-complete

container

Completed container

attached to the solar panel

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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

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Use of Phase Change Materials for Thermal Control in Building Integrated Photovoltaics

Capric/Palmitic Acid Properties Melting point 22.4 ºCHeat of Fusion 195 kJ/kgThermal 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)

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

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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