here's a growing tide of interest in solar energy – a recent survey by Forbes revealed that almost half of Americans plan to outfit their homes with solar panels in the future. But even though consumer awareness of the benefits of solar has risen, many homeowners are still confused about how solar panels work and are unsure whether their homes are even suitable for solar. The first concern that most of them have is the availability of sunlight – people wonder if they have enough sun for solar in their area and whether it is necessary for the proper functioning of solar panels. Ahead, we're answering those questions about sunlight once and for all.
A crash course on solar: how do solar cells transform sunlight into energy?
For starters, it is essential to understand how solar panels interact with sunlight and convert it into electricity.
Solar panels are a group of solar cells that join together, also called photovoltaic cells. These solar cells are made of semiconductors - materials that, unlike conductors, allow electrons to flow only in one direction and only under certain conditions.
The first generation of solar panels was made of silicon, still the most widely used material in solar panel manufacturing. According to the U.S. Department of Energy, silicon is, by far, the most common semiconductor used in solar panels, representing approximately 95% of the panels sold today. But how come it is still pretty much unrivaled? Firstly, this is due to the fact that silicon is abundantly available in nature, for example, in rocks and desert sand. Secondly, silicon has fundamental physical properties necessary for the operation of solar panels, such as a narrow band gap – a quality that allows absorbing the maximum amount of sunlight. And thirdly, silicon is perfect for solar panel manufacturing as it provides the best combination of optimum efficiency, low thermal expansion coefficient, and low cost.
A solar cell – a basic element of a solar panel – consists of two layers of silicon with different doping that are joined together to make a p-n junction. In the area of their contact within a solar cell, an electric field is created. After reaching solar panels sunlight knocks the electrons within solar cells out of their standard positions and sets them in motion. The movement of these electrons within solar cells creates an electric current, which travels through the wires to the solar inverter that converts DC electricity generated by solar panels into AC electricity used by most home appliances.
Are solar panels sunlight dependent, or can an artificial light do the job?
As we said above, sunlight is what forces electrons to move and helps solar panels generate an electric current. But then a natural question arises: is sunlight a necessary requirement for the work of solar panels, and how sufficient artificial light would be? Both the sun and a light bulb emit energy in the form of photons, after all.
Well, technically, to generate electricity with solar panels sunlight is not critical since a solar panel can work with not just sunlight but basically with any other form of visible light. But it doesn't make sense because the amount of energy solar panels will receive with artificial light is extremely small. The thing is, sunlight has the broadest emission spectrum, while artificial light has a much more limited amount of wavelengths. Besides, artificial illumination is typically enclosed by barriers such as glass bulbs. And finally, running solar panels with artificial light would inevitably lead to significant power losses due to double energy conversion. Thus, to ensure the efficient work of solar panels sunlight is a requirement.
How much solar irradiance do solar panels need?
To reach the maximum output of solar panels sunlight must provide an input level of around 1000 Watts per square meter of a solar panel, which can be achieved only during peak sunlight hours with direct exposure to sunlight. In the US, the number of peak sunlight hours averages 4-6 hours, but this number varies significantly from state to state. For example, Arizona gets about 5-7 hours of peak sunlight, while West Virginia only has four peak sunlight hours.
Do solar systems work in cloudy weather?
Even if your area generally receives enough sunlight for solar panels, you will surely wonder what happens when direct sunlight is unavailable, for example, on overcast days. Solar panels do work in cloudy and rainy weather when sunlight is scarce, but they will perform worse. The solar panel efficiency drop depends on how thick the cloud coverage is, but generally, you can expect it to decrease by around 20%. So as you can see, to generate electricity with solar panels sunlight does not necessarily need be direct.
Does a solar panel work in the shade?
The same principle applies here: solar panels still work in the shade with a lack of sunlight, but not at full capacity. But the catch is that clouds will eventually clear and give way to sunlight, while shading will cut down your solar panel output every single day. Unless you install newer solar panels with half-cut cells or buy solar microinverters, your solar panel efficiency will be limited to a worst-performing cell. For example, if 50% of just one cell is shaded, the efficiency of the entire solar panel will be cut in half.
Can solar systems work at night?
As we've already established, in the case of traditional solar panels sunlight is crucial for efficient electricity generation. However, scientists have already figured out how to make a solar panel that produces power even at night. With these modified solar panels sunlight is no more necessary, as they operate on a different principle. During the day, the sun shines on a relatively cool solar panel, and this heat radiates back to outer space at night. The solar panel thus becomes even cooler than the air, and the temperature difference can be used to generate electricity. The efficiency of these nighttime solar panels is not yet sufficient for mass production, but it is already enough to charge a phone, for example.
Ways to ensure solar panels will receive enough sunlight
If you wonder how to make the best use of your solar panels sunlight is a crucial thing you need to take care of. And even though for the normal functioning of solar panels sunlight does not need to be direct, you should still make sure they receive as much sunlight as possible. Below there are a few tips on how to do that.
Choose the proper orientation and tilt for solar panels to capture more sunlight
Solar panels perform best when sunlight hits their surface at a perpendicular angle. In most cases, a tilt between 30 and 45 degrees will give you the best result. Plus, the sun usually shines directly over the Equator, so your solar panels should face true south to deliver the best output if you live in the northern hemisphere.
Pair your solar modules with solar microinverters
Regardless of the type of solar panels sunlight has to cover their entire surface to yield the best results. However, you can minimize the negative impact of partial shading by installing microinverters instead of a simple string inverter. Microinverters convert power from a single solar panel, which means if just one of them underperforms due to shading, it won’t affect the other panels.
Trim the trees around your solar panels
If you have trees on your property and dense vegetation obscures your solar panels sunlight may be unable to reach them. Even though cutting down trees that create a shadow on solar panels is sometimes inevitable, trimming back a few branches is usually enough to maximize the exposure to direct sunlight and avoid solar panel underperformance.
Get your solar modules cleaned systematically
Cleaning can also help increase the amount of absorbed sunlight. If much dust and dirt pile up on solar panels sunlight can't be fully absorbed, thus reducing the output. That’s why regular cleanup is a great way to boost the sunlight your solar panels receive.
To sum up: to run solar panels sunlight doesn’t have to be direct but necessarily sufficient
To take full advantage of solar panels sunlight is crucial. There is nothing to worry about if your solar panels don’t receive much direct sunlight for some time - they will still be able to generate electricity. But remember that to achieve the best performance of solar panels sunlight needs to be direct most of the time.