Lately we have been swamped with questions about which solar panels are the best and which the person in question should settle for for their home.
In all honesty, we can’t answer these questions seriously. Firstly, because we are no solar panel/alternative electricity source experts, and secondly because choosing the right solar panels for your home depends on various (environmental and structural) factors, and we just can’t make a responsible judgement call from afar.
What we can do, however, is give you the tools to know what the professionals you absolutely need to consult to make such a decision are talking about in the first place, and introduce you at least to the broad options there are before you even walk into your first meeting.
Generally speaking, we at Housessive absolutely endorse making use of alternative energy sources, and among those available, solar panels are by far the most reliable, cost-efficient and durable on the market at the moment.
An additional plus for solar panels is the fact that they do not only store the sun’s energy and generate ecologically friendly electricity (depending on your choices and the infrastructure available to you, there’s even a good chance that you produce more energy than you can use up on your own, and you might end up feeding your “harvested” green energy into the general electricity supply of your community!), but can also be used to generate the warm water supply you and your family need, both for heating, as well as for actual water usage.
In terms of types of solar panels available, you can broadly put them in three separate categories:
1st Generation Solar Panels
1st generation solar panels are basically the traditional type that is most commonly used. These panels are made out of mono- or polycrystalline silicon.
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Monocrystalline Solar Panels (Mono-SI)
Mono-SI solar panels are easily recognised by their uniform dark look and their rounded edges. They come by their shape due to being made out of cylindrical silicon ingots which are then cut off at all four sides to create solar wafers.
They use silicone with the highest purity, which means that they are the type of solar panel with the highest efficiency rates (up to 20+% in the latest ones on the market).
This, however, also means that Mono-SI panels are the most expensive. On the plus-side, though, these panels occupy the least space and generally hold up better against high temperatures (as compared to polycrystalline panels).
- Highest efficiency rates! Since they are made out of the highest-grade silicon their efficiency rates typically lie at around 15-20%.
- Space-efficient! Since Mono-SI panels have the highest power outputs, you need comparatively less of them to generate the same amount of efficiency. In other words: You need less Mono-SI panels to produces the same amount of energy as with any other solar panel.
- Longest lifespan! On average, Mono-SI panels come with a 25-year warranty.
- Better performance at low-light conditions! (compared to similarly rated polycrystalline panels)
- The most expensive. Acquisition costs are higher than with any other type of solar panel on the market.
- Can be problematic in certain circumstances. There’s a good chance of the entire circuit being negatively affected when the solar panel is partially covered with shade, dirt, or snow.
- Waste of silicon. Due to their production, quite a lot of silicon is cut off the original cylinders, which then is basically thrown away as waste.
- Most efficient in warm, but not hot, weather. The solar panel’s performance suffers the further temperatures go up. However, Mono-SI panels suffer way less efficiency-loss than polycrystalline solar panels. And for most homeowners too high temperature is not really a concern.
Polycrystalline Solar Panels (Poly-SI)
Poly-SI panels can be recognised by their perfectly square form. Unlike Mono-SI panels, this type of solar panel is not cut from silicon cylinders, but is made by melting raw silicon before pouring it in square moulds to cool off. As a final step, the silicon is cut into perfectly square wafers.
This process, obviously, is a much faster and cheaper mode of production, which leads to a lower final price.
On the downside, though, Poly-SI panels have a lower efficiency rate (at around 15%), a shorter lifespan, and are more affected by high temperatures (in comparison with Mono-SI panels).
That being said, the differences between Mono- and Poly-SI panels in terms of energy production are not that big that they should have too much of an impact should you choose the slightly cheaper option.
- Smaller cost! Due to cheaper production methods, the end-price is lower as well for prospective buyers.
- Less silicon waste! Due to the easier mode of production, the amount of wasted silicon is significantly less than in Mono-SI production.
- Lower efficiency rate. The efficiency of Poly-SI panels typically lies between 13 and 16% due to lower silicon purity.
- Less space-efficiency. In order to generate the same amount of power as with a Mono-SI, you generally need to cover a larger surface-area. (Note however that this does not mean that every Mono-SI panel automatically performs better than a high-quality Poly-SI panel!)
- Lower heat tolerance. Technically, Poly-SI panels hold up worse against hot temperatures than Mono-SI panels. However, this effect is minor in most environments, so it won’t need to be a concern for most homeowners.
- Looks. Depending on your preferences, the speckled blue colour of Poly-SI panels might not mesh with your aesthetic sensibilities as well as the more uniform look of Mono-SI or Thin-Film solar panels.
2nd Generation Solar Panels
The next generation of solar panels is based on thin film solar cells, and is mainly used for smaller solar power systems, full-scale photovoltaic power stations, and as integrated parts of buildings.
In other words, they are very versatile. And, on top of that, they are typically the less expensive option when compared to the 1st generation of. solar panels.
Thin-Film Solar Cells (TFSC)
As mentioned above, TFSCs are typically a cheaper option, which is due to their mode of production.
Thin-film solar cells are produced by placing one or more films of photovoltaic material onto a substrate. And this is it.
As you can imagine, this type of solar panels is the easiest to produce and this makes them particularly cost-effective as well as being able to produce large scale with just little material input.
Speaking of material, thin-film solar cells are categorised by which photovoltaic material is placed on the substrate:
- Amorphous silicon (a-Si)
- Cadmium telluride (CdTe)
- Copper indium gallium selenide (CIS/CIGS)
- Organic photovoltaic cells (OPC)
Depending on technology and material used, TFSC panels reach efficiencies between 7 and 13%, a number which is hoped to be increased to 10 to 16% in future.
On top of that, TFSCs open up a number of new opportunities for application since they are flexible and less affected by high temperatures than their predecessors.
On the downside, Thin-film solar cells tend to need a lot of space covered in order to generate the same amount of energy as Mono- or Poly-SI panels, which typically makes them challenging to use in private single residences.
Additionally, they come with the shortest warranty of all other products due to their considerably shorter lifespan in comparison to, for example, 1st generation solar cells.
- Cheaper! Due to the simply fact that mass-production is fairly easy, they are lower in cost than crystalline-based solar cells.
- Visually appealing! Their homogenous appearance gives them a marked advantage in the looks department.
- Flexible! Their flexibility opens up many new potential applications.
- Good, consistent performance! Both high temperatures and shading have less impact on the overall energy output.
- Need a lot of space. Thin-film solar panels are in general not the first pick in most (single) residential situations. However, when space is. not an issue, utilising TFSCs absolutely does make sense.
- Increased equipment-cost. While it is true that TFSCs are on the lower end of the pricing scale by themselves, their low space-efficiency also means that the costs of additional equipment like support structures and cables will increase accordingly.
- Shorter warranty. This type of solar panels tends to degrade faster than Mono- and Polycrystalline solar panels. This noticeably shorter lifespan also translates in a shorter warranty.
Amorphous Silicon Solar Cell (A-Si)
Do the words “solar powered pocket calculator” bring back memories of your schooldays? If so, you have seen A-Si solar cells before, albeit in a smaller scale than we generally think of when hearing “solar panels”.
Such small-scale useages, indeed, are exactly the main domain of application for this type of solar panels.
Even though A-Si solar panels make use of triple layered technology, they take the overall idea of “thin-film” to the next level – typically, these solar panels come at a thickness of around 1 micrometre.
This fact alone makes them just perfect for use in smaller sized projects. However, with only about 7% efficiency rate, and the resulting low power output, amorphous silicon based solar cells have traditionally only been used in small appliances, like the aforementioned calculator.
On the upside, both production and the silicon used in it are relatively cheap, which makes A-Si panels highly cost efficient.
- Small amounts of silicon used! Since amorphous silicon is a direct-bandgap material, production requires just about 1% of the silicon used in the production of crystalline-silicon based solar cells.
- Inexpensive bases! Even the substrates used to plant the silicon on can be made out of easily available and low-cost materials such as glass, stainless steel and plastic.
- A (potentially) great future! It is nothing but a thought so far, but the aforementioned reasons are basis for the idea that A-Si solar cells have a great potential for one day becoming a cheaper alternative to mono- and polycrystalline solar cells.
- Flexible and lightweight! As they are both flexible and lightweight, A-SI thin-film modules allow for creative applications. For example, they could easily be incorporated into clothing and accessories at some future date, which makes them a desirable material to experiment with for outdoor-wear and -equipment companies.
- Good performance! As you might remember from your maths classes, A-Si solar cells perform relatively well under poor lighting conditions and are not particularly affected by shading issues.
- Low efficiency rates. At the moment efficiency rates leave something to be desired, but they are thought to increase with technological breakthroughs in the (near) future. Contemporary A-Sis would require an enormous amount of covered space to generate the same amount of energy as their competitors.
- Shorter lifespans. Just as with the TFSCs above, this type of solar panel tends to degrade faster than Mono- and Poly-SIs.
Cadmium Telluride Solar Cell (CdTe)
As the name suggests, CdTe solar cells are based on a rather low cost production out of Cadmium Telluride, which also translates into an incredibly short payback time of less than a year. This, and the fact that CdTe cells require the least amount of water during production, makes CdTe solar cells the perfect choice for you if you are mindful of your carbon footprint.
Additionally, CdTe solar technology is the only thin-film tech that has managed to surpass the cost-efficiency of crystalline silicon solar panels.
On the downside, the one big disadvantage of CdTe solar cells is the fact that Cadmium Telluride is toxic when ingested or inhaled. This makes for a big barrier to overcome, particularly in Europe, since many customers are wary of settling for solar cells that could potentially be harmful (mostly for workers during production; the risk of exposure when using the end-product is negligible).
In terms of efficiency, CdTe solar panels typically operate in the range between 9 and 11% of energy output.
Copper Indium Gallium Selenide (CIS/CIGS) Solar Cells
A relatively young type of solar cells, CIGS panels have shown the biggest potential in terms of efficiency. Their conversion/output rated typically range at around 10 to 12%.
Another plus for this flexible type of thin film solar panels is the simple fact that they use less toxic materials than are needed in the production of CdTe cells.
3rd Generation Solar Panels
The third generation of solar panels is largely made up of thin film technologies that are still (mostly) in the research or development phase.
They generate electricity by using both organic and inorganic materials, and show incredible potential both in sustainability as well as in efficiency.
Concentrated PV Cell (CPV and HCPV)
Concentrated PV cells are not a new system of generating electrical energy, nor do they make use of previously unused materials. They do differ in one very important way: (H)CPVs used curved mirror surfaces, lenses, and (sometimes) cooling systems to most effectively bundle the sun’s rays and thus significantly increase the efficiency of these solar cells.
Put into numbers, these type of solar panels boast incredible efficiency rates of up to 41%, which is by far the highest of all photovoltaic systems on the market.
In order to achieve these high rates, though, you will need to make sure that the panels face the sun at a perfect angle at all times. Usually a solar tracker inside the solar panels, respectively on their mount, is responsible for following the sun at all times.
Biohybrid Solar Cell
This type of solar cell is still very much in the research phase.
Thought up by a team of experts at the Vanderbilt University, the Biohybrid solar cell aims to emulate the natural process of photosynthesis.
Many of the materials used in these cells are similar to traditional methods, but have a much more effective rate of energy output (up to 1.000 times more) due to their use of multiple layers of the protein Photosystem 1.
Want more information?
For a way more detailed explanation of the various types of solar panels, take a look at this article in the American Journal of Optics and Photonics!