How Solar Panels work

How Solar Panels work

Solar panels are a leading development in renewable resources that is growing in popularity. Though they are somewhat expensive, no one will argue that the sun is an abundant resource that needs to be used.

Because of this more and more people will go solar and soak up these renewable resources. Solar panels are used in many places such as small portable electronic devices, pool heating, supplementing power to the home, and even becoming power independent with your own grid. There are more and more uses for solar panels as technology advances. More and more people will go solar once the benefits are widely known.

When looking at those large flat panels staring at the sun you might ask, how do solar panels work? The science behind solar panels is quite involved. Simply stated the sun showers the earth with photons that are then collected by the panels. Silicon is placed beneath a layer of non-reflective glass and absorbs the sun’s photons. The atomic structure of the silicon takes the photons and converts them into DC electrical power which is then converted in to AC by use of an inverter.

Solar Panels NASA Satellite

Choosing a Solar Panel

While technology is changing rapidly there are generally four different core kinds of solar panels at the moment.

The difference between them is how they’re made which ultimately affects their efficiency. “Efficiency” means the percentage of total light that hits the panel that can be changed into electricity.

Solar power panels are notoriously inefficient. There are lots of technical reasons for that that can be found elsewhere if inquiring minds want to know. Officially, “efficiency” is called the “sunlight conversion rate”. And, that rate can be anywhere from converting 5% to about 21% of the sunlight to electricity with today’s solar panels.  It’s pretty obvious that a 45 watt 5% sunlight conversion panel just isn’t going to perform as well as a 45 watt 18% sunlight conversion panel.  

So, no matter how something is built, look for the sunlight conversion rate, or efficiency rate. Since higher efficiency often costs more, you must decide if that increase is worth the difference. It isn’t always worth it depending on what you need and how you use them. But, conversely, sometimes the cost of solar panels isn’t that much higher for a much better panel, which would then be a better choice for the solar electric power you need.

Solar Panel Technology Explained: Monocrystalline vs Polycrystalline

To go further into detail, we need to look closer at the element that is doing the work. Silicon combined with phosphorus or boron creates a charge that is positive or negative. With silicon and phosphorus, a negative charge is created. With Silicon and Boron a positive charge is formed. When the sun strikes the silicon and phosphorus combination it floods it with extra negative charges. These charges are then drawn to the positive polarity of the silicon and boron combination. This flow of electrons creates electricity. The number of solar cells present in a panel along with the quality of the materials used will determine the total electric output of the panel.

The silicon and its partners (phosphorus and boron) are placed together to form the photovoltaic cell. With advances in technology, scientists will eventually create small and more efficient panels that can be used in a much wider range of applications.

Monocrystalline (or multi-crystal) silicon panels

These panels are made from one continuous sheet of silicon with metal attached to the edges increasing conductivity. Their efficiency rates are in the 14%-18% bracket. They’re more expensive and more efficient.
Polycrystalline silicon panels

These panels have an efficiency rate of around 12%-14% so they’re not quite as efficient as the above. But they’re good. They’re put together with individual PV cells, lots of them. Metal is also attached on the edges to aid in conduction and also hold the cells together. When an individual cell is damaged you could theoretically replace it without replacing the whole panel. Their cost is less than the monocrystalline panels.

The most efficient solar panels are still the monocrystalline silicon panels. Monocrystalline solar panels are more stable and they won’t lose efficiency as fast as polycrystalline. The polycrystalline panels are sometimes cheaper but offer a lower efficiency and they also won’t last as long, thereby increasing their overall lifetime cost.

Thin film and ribbon silicon technologies

The new batches of solar panels are the thin film and ribbon silicon technologies. These are just like the ones you see in calculators and watches. They are essentially polycrystalline cells which are either arranged or poured from molten silicon. They have the same limitations as the other types of polycrystalline panels.

String ribbon silicon panels

These are put together very much like the polycrystalline panels but with added technological differences. Some people put the efficiency rate at around 12%-14%, some considerably higher. The difference in technology does allow for a lower manufacturing cost than the polycrystalline solar panels which should translate into a lower market cost.

Amorphous silicon panels

Last and least are the amorphous silicon panels with a 5%-6% efficiency rate, the lowest of any type of solar panel. They’re made from a thin flat piece of conductive metal like copper with a thin layer of silicon film over the top. They’re inexpensive to produce, relatively cheap to buy but aren’t big on energy production. Of course, if you only want to run a couple of light bulbs, etc., these solar panels could be just the thing. Amorphous silicon is being used in new ways such as in a metal roof application which has very interesting possibilities.

Sizing Solar Panels

Physical Size

Solar panels come in all kinds of shapes, sizes and weights. Most are rigid but some semi-flexible ones are available, often related to a specific activity like camping/hiking in the wilderness. Solar panels don’t necessarily go up in size and weight with increasing wattage so, for instance, you can’t assume a smaller wattage panel will actually be smaller in physical size. Two panels of equal wattage may be quite different in physical size and weight. And, a solar panel can be a weighty bulky item. Will you be moving it? Frequently? Storing it in a hard to get at spot? Consider the size and the weight.  For example, maybe two 50 watt panels would be a better choice as they’re easier to move around than one large 100 watt panel. Only you know.

Other “size” measurements: Watts

Solar panels are rated in watts. The watt rating is how much power a panel will produce in full sunlight at 77 degrees F.  (These are ideal conditions. In real life the wattage is less by 10%-15%. ) The watt size range of a singular panel could be anywhere from 1 watt to 300+ watts.

Most solar panels up to 135 watts are 12 volt panels. Many with wattage over 135 are of a higher voltage but designed mainly for grid tie applications. Most 12 volt panels operate at a higher voltage when working; as high as 17 volts. It’s an intentional boost for reasons you can find explained elsewhere if you really want to know.

The general rule of how many watts you might need in relationship to your battery size is approximately 1 watt of solar panel for every amp hour of battery. So a 100 amp hour battery for instance, could indicate that a panel(s) 75 to 130 watts would be in the right range. But, again, this depends on how you use it, what you use it for, what you can afford, what kind of space you have, how much sunlight your area gets and so on.  

Price per watt

Compare solar panel pricing by price per watt. It’s the only way to get around the variations between them taking their features into consideration.

Advantages of Solar Energy

Although installing solar panels in your home requires an initial investment, the advantages of solar energy make that investment worthwhile. Solar power is more environmentally-friendly than other fuels such as oil and natural gas, since it uses only sunlight to generate energy and doesn’t produce any harmful waste or run-off. Solar power is a completely renewable form of alternative energy. It isn’t subject to supply and demand or the ups and downs of the market. Unlike oil, we will never run out of solar power, nor do we have to worry about the long-term, irreversible damage it may be doing to the environment.

Over time, a solar panel installation can pay for itself in the drastic reduction of electricity a household uses from the national grid.

Solar energy is virtually free, and many electrical companies will even buy any extra energy a home produces but doesn’t use. This concept is known as “net metering” and can give you a credit on your account with the local energy company. (It’s a good idea to check ahead of time, however, as this might not be offered by all companies in all areas). There are even some tax incentives for homeowners who use solar panels; you can consult a tax accountant about taking advantage of this offer.

Another of the advantages of solar energy is that it is a completely independent source of alternative energy. Solar energy doesn’t make your household dependent on an outside company and neither will you have to worry about outages due to downed power lines, lightning strikes, equipment malfunctions, or fossil fuel shortages. Because solar panels are independent of power grids, they are also useful in remote, rural areas. Some solar panels are even built to be portable for use during camping trips or to power laptops, outdoor photography/video equipment, and other devices.

Solar panels have further advantages over other alternative energy sources because they are very low-maintenance. They don’t have moving parts that need to be cleaned, repaired, or ever replaced, so your solar panel will never break down. There are various sizes of solar panels available, so that a home of any square footage can benefit from solar panels in the yard or on the roof.

The advantages of solar energy far outweigh the disadvantages, of which there are relatively few. Solar power is a clean, safe, reliable source of energy every household should take advantage of.

How Long Do Solar Panels Last?

Solar panels last a long time and lose a minimum amount of effectiveness (1% to 2% a year).  For instance, a common warranty on a wind turbine might be 3 years. On a solar panel, 30 years wouldn’t be unusual. Also, solar panels hold their value very well.

One of the hardest aspects of answering the question is actually finding a decent amount of actual domestic solar panels which have been around for longer than 20 years and are still being used today. Believe me, there aren’t many out there. Of the few that have been  we found ourselves, we found that the majority of the systems assessed are still producing electricity at around 80% of their original power output.

This includes a large sample of systems in California which were installed in the 1970’s, an amazing result!

Solar Panel Warranties

According to studies on rooftop solar panel systems it has been found that all types of solar panels lose about 0.5 – 1% efficiency per year. These findings are consistent with the observations of older installations showing that systems 20-30 years old which are still running at around 80% output have dropped efficiencies within this range.

The majority of solar roof panels come with 25 year warranties. While this is more than enough for most folks, it is becoming a well-known fact that your solar panels will last a lot longer than this if you look after them right. It’s just not practical to give warranties longer than 25 years due to the drop in efficiency.