1. Experiment Design of a Photovoltaic/Thermal Hybrid System
Maria Browne
Department of Civil, Structural and Environmental Engineering,
Trinity College Dublin
Dr. Sarah McCormack
You Supervisors’ Names Here
Prof. Brian Norton
15th February 2013
Maria Browne
Trinity College Dublin
Today my talk will be on the design and installation of a PV/thermal hybrid system
My supervisors are Dr. Sarah McCormack and Prof. Brian Norton

2. 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
Give a bit of background
15% efficient that means that 15% of the solar energy is converted in to electrical and the remainder into heat, that’s a lot of heat remaining in the panel thereby increasing its temperature
Effects of increased temperature of a PV panel,
Important to try regulate the temperature because silicon, both poly and mono make up over 90% of solar panels sold globally
Research suggests organic and some plastic cells solar cells an increase in temperature increases their performance

3. 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)
Use PCM to regulate temperature, thereby maintaining efficiency
Go into PCM in a little bit of detail
Latent heat, can absorb large amounts of heat without changing temperature
Mainly use liquid to solid phase change as gas can be difficult to contain
Types of PCM available
Importance of the their thermal properties,
Melting temperature, must be in the range to enable charging and discharging
Enthalpy to ensure high rate of absorption of heat when changing phase, larger amounts of heat stored the more heat available for use
Heat capacity, changing temperature during sensible heating again more stored energy available for other applications
Thermal conductivity must be high so that the heat transfer from the panel through the PCM and into the water is efficient

4. 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
Explain the way in which the experiment works, the reference and the PV/PCM system, then the thermosyphons and the water tank, the transfer of heat, from the PV to the PCM to the water, measuring the temperature using thermocouples, initially was a BIPV system, now a hybrid unit, passive thermal control unit, regulating temperature of PV but also heating water,

5. Use of Phase Change Materials for Thermal Control in Building Integrated Photovoltaics
How thermosyphon was inserted into the container
The black pieces are to ensure the copper piping remains in place
Thermosyphon constructed in copper piping
Then can be seen in the semi-complete container and the way in which it was fixed in place
Finally, the completed sealed container is attached to the solar panel
There are six holes on the back of the container, thermocouples will be placed here will go into more detail later
Thermosyphon, through which the water will flow
Thermosyphon inserted in the semi-complete container
Completed container attached to the solar panel

6. 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)
Go through all the positives of the capric/palmitic fatty acid properties
Why better than RT20 just say?
Shown to be thermally stable following various thermal cycles
Corrosion, not a huge issue, unlike that of other PCMs such as salt hydrates
Initially, salt hydrate was chosen found to be very corrosive

7. 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
What are we going to measure?
The heat transfer across the system using thermocouples, see from the front of the PV through to the back
The front and back use twisted K-type thermocouples, all of which have been calibrated
The middle of the PCM uses stainless steel sheath thermocouples
I mentioned earlier the holes in the back of the container, they are for the compression glands as shown in the image onscreen, a thermocouple will then be inserted through the gland
To maximise the heat transfer from the PV to the container, thermal conductive paste has been applied between both surfaces

8. 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
As for the electrical aspect of the system, the current and voltages for the PV and battery in each system will be measured
As in the diagram you can see the electronic board,
Take the first system for example,
PV will be connected to the fuse, then shunt, through the switch and then on to the charge controller
The shunt is used to measure the current
Potential dividers which are not on the board have been attached to bring the voltage of the devices down to ensure no damage to the dataloggers
What does the charge controller do?? Allocate the power from the PV to the batteries or to the load
The battery will connect through the fuse, to the shunt, switch and then onto charge controller
The resistors are there to ensure that the power generated by the PV will be used when the battery is fully charged

9. 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
Go through expected results

10. Image of the complete thermal/hybrid system
Completed system
Hope to start testing this summer

11. Thank you for your attention. Any questions?
Thank you and any questions??