They start working every morning at dawn and continue through to sunset each evening. Ever wonder what impacts a solar panel’s ability to convert sunlight to electricity each day?
A lot of different factors add up to the answer. Some are dependent on the particular model of panel, and others on where the panel is located. The local climate factors into the equation, as does the surrounding landscape.
Every solar panel is made up of photovoltaic cells and these cells have an efficiency rating. Higher efficiency cells can convert more of the sunlight into electricity. Most current solar panel models have an efficiency range of 18 to over 21%.
This efficiency will degrade as the panels become older. The rate of degradation differs by manufacturer and model. The power rating of a panel can be reduced to anywhere between 85 and 92% of the original wattage over 25 years of service, an important design consideration.
Solar panels are also impacted by the surrounding air temperature. The power produced by a panel can be reduced by 0.2 to 0.3% per degree F rise in air temperature. Solar panels with a 400-watt rating at 77 F will have their production drop by 31 to 46 watts on a 115 F day in Phoenix, which is significant and needs to be factored into the design for generating the required electricity each year.
The tilt and direction of each panel, whether installed on a rooftop, ground mount or shade structure, is important when determining electricity production. Maximum annual production will result when a panel is tilted at an angle equal to the latitude of your location (Phoenix is at 33 degrees) and facing true south.
Every pitch on a roof, sun structures, parking covers and open ground all have the potential for the installation of solar panels. The angle and orientation of panels mounted on a sloped roof are generally assumed to be the same as the roof. For flat roofs, sun structures, parking covers and open ground the panels can be angled optimally for the latitude with tilted racking.
Ground mount systems also have the advantage of possibly being oriented south and tilted optimally for maximum exposure. Where available south-facing surfaces are restricted on a property, selection of a high wattage solar panel can be important.
Geographic location will determine the strength of the sun. Solar irradiance is the amount of solar energy that strikes a given area over a specific time and varies with latitude or the seasons. This is why the solar potential of a property is assessed over a 12 month period.
Solar energy is made up of direct irradiance, received directly from the sun, and diffuse irradiance, received after reflecting off particles in the atmosphere. Historic weather is used to predict future solar energy using data from previous months out of every past year which were considered average to build a typical metrological year.
So far, these factors assume that there is no shadowing of the solar panels from offset vegetation or buildings, sunrise to sunset. However, trees, cacti, chimneys, parapets, railings and roof vents can all cast shadows and reduce solar energy on panels.
All in all, there are some factors we must be prepared to work with, such as the location and design of our property. Other factors are within our control. These include the model and rating of the panel, where and how they are positioned, keeping them clean, trimming vegetation, and avoiding obstructions.
We can also look at new structures or ground areas where panel power production would thrive. We can’t change the weather in our region but we can design and maintain our solar array to capture and convert the most sunlight possible.
So, a day in the life of a solar panel is all about exposure and conversion. The best panel designs, orientation, and maintenance working with the arc, availability of the sun and temperature will all determine how much daily electricity can be produced. This will make sure the solar is hard at work every day!