It is worthwhile to take a look at the less commonly discussed factors that will impact solar panel electrical energy production, particularly in Brisbane. As we mentioned in the solar efficiency page, one of the factors that negatively impacts photo voltaic electric output is the temperature.
Two factors Related to Solar P.V. De-rating:
1. As a rough rule of thumb, many commonly used solar panels in Brisbane, have a so-called ‘de-rating’ factor of around 0.5% per degree above 25 degrees celcius. This means that for every 10 degrees Celsius above 25 degrees Celsius the panels will output approximately 5 percent less solar power – quite a significant amount! Using ‘de-rating’ factors is not electrical slight of hand – it is commonly used in most electrical and engineering specification processes and de-ratings appear on most electrical data sheets – often associated with a parameter being specified at ‘ambient‘ temperature.
2. The other factor to consider is that because of the construction and design of solar panels and their positioning (orientation and pitch), they will generally be significantly hotter than the ‘ambient’ or ‘air’ temperature. This increase in the panel operating temperature is not linear, meaning, for example at 30 C ambient temperature the solar panels may be operating at a temperature of around 50 C whereas on a very hot day, say a Brisbane summers day where temperatures can creep up to 40C, then the solar panel could well be operating at a temperature of 70C++
Example 1: Ok, lets say the ambient temperature today in brisbane is 30C. The panels are operating at 50c temperature. therefore the losses, associated with the temperature being above 25C would (approximately) be equal to 0.5 times 25 = 11% less solar power outputted due to temperature.
Example 2: lets take a very hot Brisbane day – say 40C – as discussed above the solar panels could well be ‘running’ at a temperature of 75-80C, (have you ever been on the roof of your house on a hot day??). Working off a panel temperature of 80C, potential power losses could reach 0.5 times 55 =27.5 percent less outputted solar electricity, than at 25C!!
Conclusion: When getting solar quotes for a solar system, we recommend getting monthly and annual estimates of generated solar electricity as part of the quotation. Having an understanding of the factors that can impact solar power production is helpful in, for example, understanding seasonal impacts on solar output. Clearly a sunny but cooler Brisbane day is more favourable to getting the maximum electricity out of the panels than a blazing hot 40+Celsius summers day in Brisbane!
The following video (part of a 6 video series) is interesting as they look at the effect of temperature on different types of solar panels (poly / mono / amorphous etc):