Solar panels are characterised by their ability to produce electricity without moving, unlike the rotating machinery found in hydroelectric facilities and power plants fired by fossil fuels. As a result, solar panels are not subject to mechanical wear, and their maintenance requirements are much simpler than those of other generation systems.
You have surely noticed that photovoltaic arrays are modular: regardless of total capacity, the basic building blocks are solar panels, which typically have a rated output ranging from 250W to 330W. However, this value represents the instantaneous power produced under ideal testing conditions, not the actual electricity output in field applications. The electricity produced by one solar panel in a full year depends on several factors:
Since each project site is unique, you will find that identical solar systems in different locations show variations in their yearly output. Solar electricity production must be estimated for each project – there is no way to calculate solar generation without site-specific data. At best, you can estimate how much electricity the solar panel would produce in idealised laboratory conditions.
Although solar panels can be manufactured of any size, most photovoltaic installations use either 60-cell modules or 72-cell modules.
Assuming all other conditions are equal, a 300W solar module will deliver around 20% more electricity than a 250W module. However, solar panels do not perform at their rated power in actual projects, since site conditions differ from the ideal testing conditions.
Before explaining how much electricity is delivered by each solar panel, first we must describe the concept of peak sun hours. Solar panels do not have the same productivity throughout the day – they are more productive around noon and less productive close to sunrise and sunset. If you multiply the rated power of a solar panel and the full duration of a day, you would be overestimating the electricity production drastically.
The theoretical energy output of a solar panel under ideal conditions is obtained by multiplying its rated wattage and peak sun hours. However, in actual projects, solar panels normally deliver between 80% and 90% of their ideal output.
Assuming 2,000 PSH per year and a real electricity output of 85% with respect to the ideal output, we get the following result for the 250W and 300W modules.
The productivity of photovoltaic modules is strongly dependent on solar radiation, but you must also consider the physical conditions of each project site. Even if the site gets decent sunlight, some factors may prevent solar systems from operating at peak output.
Finding a spot where the sky is completely clear is very difficult – you would have to be in the middle of the ocean. In land-based locations, there are natural features such as trees and hills, and artificial obstacles like buildings and unipole signs. These obstacles block a portion of the available sunshine, so you cannot assume that PV panels will get all the solar radiation available.
The orientation of solar panels is also very important, since the incident solar radiation changes based on the direction they are facing:
Also keep in mind that the sun’s position in the sky changes throughout the day, and solar panels are more productive when they face the sun directly. This is only possible with a tracking mechanism, but in most cases a better option is simply making the solar array larger – trackers can be cost-effective when your space for solar panels is limited.
Solar power companies normally use software to simulate factors such as solar module orientation, moving shadows and the sun’s position in the sky. The calculations described described in this article only provide a broad estimate, but they can give you a general idea of what to expect. In general, Australia has excellent conditions for solar power – the landmass gets enough sunshine to meet the country’s energy demand 10,000 times.