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  Solar & Renewable Energy Specialists.  
Specializing in Grid Connect, Solar Hybrid, Standalone Systems and Emerging Technologies.

Grid Connect Solar System

 

Understanding how a Grid Connect Solar PV System works

 

 

Trying to understand how a grid connected Solar PV system works can get very confusing. When trying to calculate the amount of energy a Solar System will produce, the figures will always be based on an average. Averages will include things like location, orientation, angles panels are mounted, system size etc. etc. Nobody that truly understands Solar PV will say that a system WILL produce this much electricity per day/year etc. So for anyone who is trying to investigate it for themselves it can be a daunting process.  We will try to make it as easy as possible and we will use figures take from an actual System to help make the process as easy as possible. We will also explain things is easy to understand layman’s terms.

Every day the production of the system will be different. The reasons for this is simple, panels work the best when they are 90 degrees from the sun and that is why it is so hard to give accurate figures on a systems production. Factors that can affect the performance of panels can include, time of year, time of sunrise & sunset, amount of clouds in sky, amount of rain, amount of fog, amount of shade on the panels and even smog or pollution can impact the production. The orientation and inclination of the panels and location. A simple thing to remember is they are Solar panels, the more sun the better they work. The flip side of that is that panels have a temperature range that they work best in and that can vary depending on the manufacturer of the panel. For most panels 25degrees Celsius ambient is the optimum temperature for production. They will lose production the hotter it gets and again that will vary on the manufacturer and type of panels.

To help understand a system as best as we can explain we will show some data from a 5.0kW System in Brisbane = 20 x 250 watts = 5000 watts = 5.0kWTrina Honey panels & an SMA SB 5000TL Inverter. 10 panels mounted facing East at 22 degree roof pitch = 2.5kW and 10 panels mounted facing West at 22 degree roof pitch = 2.5kW. This is what is known as a split system.

The below graph shows 2013 total monthly production figures.

Innolec Solar Power
January was the best month of total production as shown in the graph below.

Innolec Solar Power
The system produced 693.035kWs (kilo watts) with an average of 22.356kWs per day. Which for a 5kW System is daily average of 4.471kWhs per day. The best day of production was the 3rd which for a 5kW System produced 32.396kWs, a total of 6.479kWhs (kilo watt hours). The worst day that month was the 27th again 5kW system produced 2.882kWs for the whole day, a total of 0.576kWhs. This is why it is so hard to predict a systems production. Summers production is always best for a split system as the sun is higher in the sky and closer to 90deg. from the panels for longer.

June was the worst month for production as shown in the graph below.

Innolec Solar Power

The system produced 310.011kWs with an average of 10.334kWs. Again for a 5kW System is a daily average of 2.0667kWhs per day. The best day of production was 3rd which again for a 5kW System produced 15.312kWs a total of 3.0624kWhs. The worst day that month was the 21st again 5kW system produced 2.634kWs for the whole day, a total of 0.527kWhs.  Winters production is the worse as the sun is lower in the sky and thus rarely at 90deg from the panels.

August was the most consistent month for production as shown in the graph below.

Innolec Solar Power

The system produced 576.521kWs with an average of 18.597 average daily 3.719kWhs.  The best day of production was 21st which produced 21.317kWs a total of 4.263kWhs. The worst day that month was the 1st which produced 13.311kWs for the whole day, a total of 2.662kWhs. Very little clouds or rain for that month.

The total production for 2013 was 6,929.797kWs. Average daily production was 18.986kWs. The average was 3.797kWhs.

A split system that has an even number of panels on each side of the roof will lose approximately 13-14% production (depends on where the figures come from) of what a system of the same capacity facing north with the panels tilted at the same inclination. With this in mind if this was a north facing system the average kilo watt hours per day would have been 4.329kWhs.