If you are interested to find out information about:
- Various types of solar panels used in real deployments for home, business, and mobile applications,
- What kind of solar photovoltaic panels to choose for your solar project and how to select them,
- Any risks of using secondhand or homemade photovoltaic solar panels,
You’ve come to the right place.
This is practical information, with no theoretical stuff, so let’s begin!
Nowadays, the most commonly used photovoltaic solar panels in practical solar power installations are:
- monocrystalline solar panels
- polycrystalline solar panels
- thin-film (amorphous) solar panels
Each solar panel type has its own:
- price point
- ability to convert solar energy into electricity also known as efficiency
- installation area required per generated DC electricity, also known as the necessary area for installation of 1 kWp (1kWp = 1,000Wp).
These three main factors translate into two main key performance indicators used to compare different types of solar panels:
- $/Wp or price per installed Wp in USD
- the area needed for installation of 1kWp
Let’s focus on three essential parameters of the different types of solar panels, which determine the price point of the solar panel and installation area needed for a solar array.
These three parameters are:
- the conversion efficiency of solar panels
- the temperature’s impact on solar panel efficiency
- the impact of the irradiance changes on efficiency – for example, the difference between solar performance in a sunny day and a cloudy one, in the winter, etc. due to these changes.
The conversion efficiency of solar panels
Different types of solar panels have different ability to convert sunlight into electricity or conversion efficiency:
Type of Solar Panel Conversion Efficiency
Mono-crystalline Silicon 12.5-16%
Poly-crystalline Silicon 11-14%
Copper Indium Gallium Selenide (CIGS) 10-13%
Cadmium Telluride (CdTe) 9-12%
Amorphous Silicon (a-Si) 5-7%
It should be noted that the conversion efficiency of a solar cell is usually higher than the efficiency of the solar panel itself.
According to Fraunhofer ISE: Photovoltaics Report (2014) updated: 28 July 2014:
the record lab cell efficiency is 25% for mono-crystaline and 20.4% for multi-crystaline silicon wafer based technology.The highest lab efficiency in thin film technology is 19.8% for CIGS and 19.6% for CdTe Solar cells
Temperature’s impact on solar panel efficiency
Another essential key performance indicator of solar panels reveals how their ability to produce solar power efficiently is affected by temperature increase and hot environmental conditions.
This indicator is known as ‘temperature coefficient of power’ of a solar panel.
Solar panels have a negative temperature coefficient which means that the solar panel’s performance declines as cell temperature increases.
As you know, the solar panel rated output power is defined under the Standard Test Conditions (STC):
- 1,000W/m2 of sunlight
- 25°C cell temperature
- Spectrum at air mass of 1.5
Typically at positive temperatures of the surrounding area, the cell temperature is about 15°C higher than the ambient one, as a result of the solar panel encapsulation.
For example, if the temperature coefficient of a specific solar panel is -0.5%/°C and the ambient temperature is 40°C, the cell temperature is expected to be roughly 15°C higher than the ambient one, as a result of the solar panel encapsulation.
In this case, the loss in the solar panel power output at 40°C is:
In other words, a panel rated at 100W under the STC (25°C cell temperature) would produce only 85 W at 40°C ambient temperature.
Generally, the temperature coefficient of thin-film panels is less negative compared to one of the crystalline solar panels.
This means that they may produce more power than crystalline panels under hot temperatures.
The impact of irradiance changes on solar panels efficiency
Solar irradiance is related to climate conditions.
It changes throughout the day and the year and one is different for different places.
Therefore, the second important factor in choosing the best type of solar panel is the prevailing climate condition at your location.
As we already know, the performance parameters of solar panels are given under the STC conditions and any deviation from those conditions determines the corresponding losses.
The definition of the STC conditions reveals the main factor contributing to the production losses:
- temperature conditions
- any deviation in respect to Irradiance level of 1000W/m2, which correspond to most common sunny noon day.
We have already described above the temperature influence on solar panel’s conversion efficiency.
However, one of the most overlooked parameters is the influence of the irradiance level on solar panels productivity.
Usually, the lower the irradiance with respect to 1000W/m2, the lower the efficiency of a solar cell.
You can expect lower irradiance levels early in the morning, during a cloudy day or in winter.
Surprisingly, the amorphous silicon thin-film solar panels, which are considered a lower grade and a cheaper version of mono- and polycrystalline solar panels, show better performance in lower irradiance conditions than more expensive crystalline ones.
Therefore, the photovoltaic panel type that could be the best fit for your solar project in most cases should be carefully chosen by weighing the pros against the cons of the above-mentioned factors and parameters.
Being aware of these pros and cons you can help you make an informed decision which panels will be the best option for you.
Different types of solar panels explained
Monocrystalline Solar Panels
Monocrystalline panels are the most efficient type of solar panels but also the most expensive ones. They come in blue or black color.
The fewer solar panels you need to produce a certain amount of power, the higher the efficiency.
Generally, if there is not enough free space on your roof, you choose panels with higher efficiency.
The main disadvantage of monocrystalline solar panels is their higher intolerance to shading and dirt.
Even the shading of only one solar cell can reduce their performance by about 20%.
Polycrystalline Solar Panels
Polycrystalline panels are slightly less efficient and cost 30-50% less than monocrystalline ones when intended to produce the same amount of power.
Polycrystalline panels have a lifecycle of about 25 years. The practice has shown, however, that polycrystalline panels installed more than 25 years ago are still perfectly operational.
Polycrystalline panels are typically blue and can be easily distinguished by their multifaceted, kind-of-shimmering appearance.
Thin-film (amorphous) panels
Thin-film panels are the least expensive panels with the lowest efficiency – usually twice lower than the efficiency of monocrystalline panels.
Therefore, to generate the same amount of power you need twice more thin-film panels than monocrystalline ones
Thin-film panels have a dark surface – usually colored in brown, grey or black.
Thin-film panels are used in solar calculators.
Under the group of thin-film panels are classified the following solar panel types:
- Amorphous-Si (a-Si)
- Tandem a-Si/microcrystalline
- CIGS (Copper Indium Gallium Selenide)
- CdTe (Cadmium Telluride)
- Dye-sensitized (TiO2)
The efficiency of amorphous-Si is about 6-7%.
The efficiency of CIGS thin-film panels, however, is about 16-18% with a recent record of 20.8% in laboratory conditions.
Despite their high efficiency, CIGS thin-film panels failed to compete concerning the lowest cost per produced Watt of electricity.
Another important issue worth mentioning is that thin-film (amorphous) silicon photovoltaic panels are affected by the so-called ‘Staebler-Wronski’ effect.
This effect causes a reduction in panel efficiency over time.
The main reason for this to occur is the defect amorphous silicon density increasing under sunlight exposure.
About six months after installation, however, this effect reaches equilibrium and practically does not cause any further degradation of solar panel’s output power.
Therefore, during the first year of operation thin-film (amorphous) silicon panels produce about 10-15% higher energy.
After about six months of operation, they settle down to their usual yield which they sustain over the rest years.
Thin-film solar panels have lower losses or in other words perform better in:
- hot climates and higher temperatures
- low irradiation conditions, i.e. early in the morning, at sunset and in cloudy weather
- partial shading conditions
Due to these benefits combined with low cost, low weight and high durability to mechanical impacts, thin-film solar panels are often selected for small mobile photovoltaic systems for campers, motorhomes, RV and caravans, where panel’s efficiency is not a great concern.
These panels are also more suitable for non-standard mounting conditions on facades.
Crystalline (mono- or poly-) photovoltaic panels are the most common solar panels for home and business solar photovoltaic systems.
Due to their high efficiency, they are also preferred a good choice for medium-scale mobile solar panel systems where free space on the caravan’s roof is limited.
Nowadays, these types of solar panels account for 90 % of the photovoltaics market share.
In contrast, the thin-film solar panels have about 10% market share.
Crystalline panels come in a variety of size and shapes. The rectangular shape is the most common one.
Each solar panel has nominal power rated in ‘watts-peak’ (Wp) or ‘kilowatts-peak’ (kW), also known as installed Wp DC power or watts-peak direct current power.
Here is a comparison between solar panel efficiency according to the area needed to install a solar panel of nominal power = 1 kWp:
PV cell material Panel efficiency Area needed for 1 kWp
Monocrystalline silicon 13-16% 7 m2 (75 sq.feet)
Polycrystalline silicon 12-14% 8 m2 (86 sq.feet)
Amorphous silicon 6-7% 15 m2 (161 sq.feet)
Other important things to look when choosing the best solar panel are:
- solar panel’s manufacturer reputability
- quality of the manufacturing process, namely whether the manufacturer controls each stage of the manufacturing process, i.e. Silicon Material-Wafer-Cell-Solar Panel-Solar Panel-Solar System
- materials used to produce the solar panels
The video below sheds more light on this:
Before choosing the best solar panel type for your application, the following variables should be considered:
- The prevailing climate conditions influencing the temperature’s impact on solar panel efficiency and the impact of the irradiance changes on efficiency,
- The available mounting area which determines the conversion efficiency of a solar panel. This is particularly valid for mobile solar panels systems on motorhomes,
- Whether the solar panels are to be mounted on a roof (of a house or a motorhome) or are going to be deployed somewhere on the ground, as mobile units,
- The solar panel warranty conditions and its manufacturer reputation,
- Your budget available and your plans for future expansion of your solar power system.
As you see, there is no obvious winner among the different types of solar panels. What is more, under different circumstances the winner changes.
Every advertised remarkable parameter of the given type of solar panel not regarded under the context of the above-mentioned variables could lead you to a wrong decision.
After all, you don’t buy performance parameters but rather you better productivity regarding the kWh/kWp generated power provided at the lowest possible cost.
Why is it important to know more not only about the solar panels but also about the rest building blocks of a photovoltaic power system and the system as a whole?
The efficiency of solar panels to convert sunlight into electricity plays an important role and plays a crucial role in delivering solar-generated electricity.
To produce the electricity used by your appliances a solar system needs not only solar panels but also additional components.
The usage of such components introduces unavoidable additional losses in the system, which in turn reduces the amount of electricity produced by the solar panels.
By carefully designing the solar system and skillfully selecting all its building block these losses could be minimized.
Moreover, upon everything else being equal, by using special building blocks you may squeeze more power up to 30% more from the solar system while maintaining its price relatively the same.
You can discover more in-depth practical and money-saving information about photovoltaic solar panels in the paperback or Kindle editions of our best selling book ” The Truth About Solar Panels-The book that Solar Manufacturers, Vendors, Installers and DIY Scammers Don’t Want You to Read”.
This best selling book in the solar category at Amazon Books is packed with more secrets and useful tips about solar panels that will save you a lot of time and money.
The book is available at any Amazon shop WorldWide.
What kind of solar panels to select?
Monocrystalline solar panels are the most efficient ones.
Their efficiency is within the range of 12-25 % with a typical value of 18%.
Use monocrystalline panels if either your space is limited or installing large PV panels would be too expensive.
Polycrystalline panels are similar to monocrystalline ones but:
- Compared to monocrystalline panels, need a slightly larger area to produce the same amount of electricity,
- Cost less,
- Are less efficient than monocrystalline solar panels with an efficiency range of 12-25% with a typical value of 15%. However, polycrystalline panels are less expensive than monocrystalline ones and are the most widely used type of solar panels today.
Despite these differences, both monocrystalline and polycrystalline panels are a good choice both for residential and mobile solar panel systems.
Apart from the high performance and the self-cleaning ability, they are always preferred where space is an issue – and this is valid both for houses and motorhomes.
Thin-film panels usually need a twice larger area to produce the same amount of electricity, compared to mono- and polycrystalline panels.
They are the least expensive type of PV panels with the following most common varieties:
- Cadmium Telluride (CdTe) thin-film panels
- Copper Indium Gallium Selenide (CIGS) thin-film panels
- Amorphous silicon (a-Si) thin-film panels.
Choosing thin-film panels would mean that you have:
- A rather limited budget,
- Quite a large area to install the PV array, and/or
- High solar panel efficiency is not important for you. This is especially valid in case of small solar power systems.
Therefore, unless you have the above concerns, it does not seem quite reasonable to select PV panels with efficiency twice less as common.
The risks of using secondhand or home-made panels
There are plenty of websites claiming it is possible to launch and run a home solar electric system for just $200-$300.
Moreover, you could find plenty of websites offering you cheap and secondhand panels or individual solar cells.
Don’t trust these websites since they provide you with either wrong or misleading information!
Furthermore, any credits and rebates you could apply for before the government institutions are NOT valid for home-built solar electric systems and their components.
For this reason, launching a solar electric system built of home-made panels could be a violation of local electric regulations.
You might not be allowed even to install such home-made panels, let alone operate them.
In many countries, it is illegal to export power to the grid by a solar system built of non-approved solar generation equipment.
It is possible to build a solar system for around $200.
Such a system, however, is going to be of low power output – about 100 Wp – which is certainly not enough to power an entire house.
Rather cheap solar panels, unless they are Chinese-made or home-made, are usually rejected by their manufacturers – either because they are physically damaged or because their characteristics differ from the stated ones. If you use such panels, it might be possible that neither of the stated values can be achieved during operation.
It should be noted that the relatively high price of solar panels is related to the stringent and therefore expensive processes of manufacturing.
Such processes require both expensive equipment to perform some special operations and stringent room conditions (with regards to room temperature, cleanness, pressure, etc.).
The reason why the manufacturing processes are so expensive is hidden in the fact that solar panels are not only designed to ensure maximum performance upon converting solar energy into electricity but also to withstand tough weather conditions – cold, rain, snow, ice and heat.
Using cheap panels to build a solar system is the same as plugging an electrical device you know nothing about into a live electrical network. What you should do is just pray not to see your home on fire!
Click here to discover how to choose, find and select the best solar panels in terms of price and and performance and how to squeeze more power from your solar power system while saving even more money on electricity. Act Now!
You also may like:
1. Boxwell, Michael. 2012. Solar Electricity Handbook, Greenstream Publishing, Amazon Kindle Edition
2. Pop, Lacho, Dimi Avram (2014-11-26). The Truth About Solar Panels: The Book That Solar Manufacturers, Vendors, Installers And DIY Scammers Don’t Want You To Read The Truth About Solar Panels (Kindle Locations 483-490). Kindle Edition.
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