Continued+PV+calculations+16-6-2011


 * Date: ** 16th June 2011

Following on from the preliminary tests carried out on the Solar PV panel on 14th of June2011, and having found additional technical data on the panel from [|www.solarelectricsupply.com] the team decided to investigate the influence of Panel temperature on its performance.
 * Experiment: ** Effect of PV panel temperature on Voltage and Current

The purpose of this experiment was to examine the effects, if any, of a change in PV panel temperature on it's generated ﻿open circuit voltage (Voc) and short circuit current (Isc). In order to do this, all other factors that could influence the results were kept as constant as practicable. These factors were;
 * Methodology: **
 * Relative orientation of the panel to the sun
 * Tilt angle relative to the inclination of the sun
 * Shading of the panel eliminated
 * Total solar irradiance at the panel at the exact time that readings were taken for voltage and current.


 * Apparatus: **


 * BP solar PV panel
 * Instruments: **


 * Mac Solar E Solar Radiation Measuring Device.
 * Digital Multi-meter
 * Raytex infra-red Thermometer


 * Procedure: **


 * 1) The tilt angle of the panel was set at 35deg from the horizontal ensuring that the **direct** solar radiation would be as close to the Normal (Perpendicular to the panel) as possible.
 * 2) The panel was covered with reflective sheeting and positioned on the balcony directly facing the sun.
 * 3) A Digital multi meter was connected to the outputs located at the rear of the PV panel (DC Volts setting was selected).
 * 4) The Solar Radiation measuring device was held parallel to the PV Panel to deduce the solar irradiance in W/m².
 * 5) The temperature of the panel was recorded.
 * 6) When the solar radiation reading steadied at 1000 W/m² the panel was uncovered and Voc was recorded . The multimeter was configured to read current and Isc was recorded whilst ensuring that the panel was still receiving 1000 W/m².
 * 7) The panel temperature was allowed to increase until it peaked at 40deg C. At this point and with the solar radiation reading at 1000 W/m² the readings for Voc and Isc were recorded.


 * Observations: **


 * Date of Experiment: 16th June 2011 **
 * Time Frame of Experiment: 10am-1.30pm **

Despite every effort being made to ensure that the readings for Voc and Isc were taken **only** when all other variables were controlled, this proved very difficult in the case of the solar radiation level at the panel as the clouds were scattered and fast moving across the sun. Readings were therfore only taken when the level of solar radiation was relatively steady although errors would be expected in the time taken to reconfigure the multimeter from voltage to current.

Shading across the PV panel was eliminated on this occasion due to the orientation of the sun.


 * Results: **


 * Angle of Inclination || Irradiance (W/m2) || Open circuit Voltage (Voc) || Short Circuit Current (Isc) || Temperature ||
 * 35 || 1000 || 21.3 || 4.22 || 25 ||
 * 35 || 1000 || 20.63 || 4.28 || 40 ||


 * Calculations of predicted results: **

Given that the first set of readings for solar radiation and temperature were similar to those of Standard Test Conditions the actual readings for Voc and Isc can be directly compared.

In the case of the panel at 40°C, the temperature coefficients of Isc, Voc and Pmax are applied as follows.

Temperature of panel = 40 °C

Temperature at standard test conditions = 25°C

Temperature difference = __**15**__ **__ __**°**__C __**

// (source: //[])
 * Temperature coefficient of Isc = 0.065 **** % / **** °C **
 * Temperature coefficient of Voc = -80 mv / **** °C **
 * Temperature coefficient of Pmax = -0.5 % / **** °C **

When the panel is at 40 °C


 * Isc ** = 3.99 + (15 * (3.99 * 0.065%)) = **__4.029A__**
 * Voc ** = 22.1 – (15 * 0.08) = __**20.9**__ __** V **__
 * Pmax ** = 65 – (15 * (65 * 0.5%)) = __**60.125**__ __** W **__

When the **actual** readings were compared to the **predicted** readings an overall error was recorded for both current (0.23A) and voltage (0.8V). This may have been either in the calibration of the multimeter or human error in the time taken to read the instruments during fluctuating solar radiation levels. However is was seen that there was a change in both Voc and Isc and in the predicted directions. As the temperature rose, the voltage dropped by 0.67V, broadly inline with predictions and the current increased.
 * Conclusions: **

Using digital meters with no data logging capabilities leads to inaccurate readings and the solar PV panel should now be connected to the Power Monitor and displayed in Real Time using SCADA software.
 * Recommendations: **

Carrying on from tuesdays preliminary PV panel test experiment of 14th june, the team decided to take a few more calculations. With the aid of MET Eireanns website, an inclination angle of 35 degrees to the sun was agreed by the team and this was achieved by using set squares, protractor and spirit level. The strut used to protrude the PV panel to the correct angle of inclination was too short and with the help of the onsite technician, a new strut was manufactured to the correct lenght of 1055mm as per page 18 of the instruction manual.
 * Thursday 16th June**
 * New Procedure**

The mobile PV panel was placed on the balcony to obtain the optimum sunlight for that particular period of the morning. Amongst the equipment used was an insolation Macsolar device for obtaining when the required watts/m2 was available, raytex infra red thermometer and digital multimeter. It should be noted that there were problems with overcast weather and rain together with the sun moving as the day progressed. Two temperature readings were obtained as indicated in the table below;
 * Experiment carried out between 10:00am-1:30pm**

//The team plan to meet shortly to discuss the overall findings and then move on to the next aspect of the project.// //﻿//
 * Results**
 * Tilt Angle || Solar (W/M²) || Voc || Isc || Temperature ||
 * 35º || 1000 || 21.3 || 4.22 || 25 ||
 * 35º || 1000 || 20.63 || 4.28 || 40 ||