In this article you will discover the important actionable and money saving information about the different types of solar panels installed today , many practical tips about how to choose the best type of solar panel suitable for your solar project and how to select the best solar panel model belonging to this type.
Nowadays, the most used photovoltaics 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 different:
- price point
- ability to convert solar energy into electricity also known as efficiency
- required installation area per generated DC electricity also known as necessary area for installation of 1 KWp (1KWp=1000Wp).
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
- area needed for installation of 1KWp
Let’s focus on three important parameters of the different types of solar panels which determine the price point of the solar panel and installation area needed for solar array.
These three parameters are:
- conversion efficiency of solar panels
- 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 and etc. due to these changes
Conversion efficiency of solar panels
Different type 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 must be noted that conversion efficiency of the solar cell is usually higher than the one 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 important key performance indicator of solar panels reveals how their ability to produce efficiently solar power is affected by temperature increase and hot environmental conditions.
This indicator is known as solar panel temperature coefficient of power.
Solar panels have a negative temperature coefficient which means that the solar panel’s performance declines when cell temperature increases.
As you know the solar panel rated output power is defined under Standard Test Conditions (STC).
- 1,000W/m2 of sunlight
- 25°C cell temperature
- Spectrum at air mass of 1.5
Please have in mind that generally for the positive temperatures of the surrounding area the cell temperature is about 15°C higher than the ambient one due to solar panel encapsulation .
For example, if the temperature coefficient of given solar panel is -0.5%/°C and the ambient temperature is 40°C then the cell temperature is expected to be roughly 15°C higher than the ambient one due to panel encapsulation.
In this case, the loss in solar panel power output at 40°C is :
In other words, a panel rated at 100W under 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 for choosing the best type of solar panel is the prevailing climate condition at your place.
As we already know, the performance parameters of solar panels are given under STC conditions and any deviation from those conditions determines the amount of corresponding losses.
The definition of 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’ve already described above the temperature influence on solar panel’s conversion efficiency.
However, one of the most overlooked parameters is the influence of irradiance level on solar panels productivity.
Usually, the lower the level of irradiance with respect to 1000W/m2 the lower the solar cell efficiency.
You can expect lower irradiance levels early in the morning , during cloudy day or during winter.
Surprisingly, the amorphous Si thin film solar modules, which are considered as a lower grade and cheaper version of the mono and poly crystalline types of solar panels, show better performance in lower irradiance conditions than most expensive crystalline ones.
Therefore, the solar panel type that could be a best fit for your solar project in most cases must be carefully chosen by weighing the pros against cons of the above mentioned factors and parameters.
By knowing these pros and cons you can make an educated decision which panels will be the best choice 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 less solar panels you need to produce certain amount of power, the higher the efficiency. Normally if there is not enough free space on your roof, you choose panels with higher efficiency.
The other 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 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. 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 less than monocrystalline panels’ efficiency. This means that 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 modules 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-sensitised (TiO2)
The efficiency of amorphous-Si is about 6-7% however the efficiency of CIGS thin film panels is about 16-18% with a recent record of 20.8% in laboratory conditions.
Despite of the their high efficiency for the time being CIGS thin film panels failed to compete in terms of lowest cost per produced Watt electricity.
Another important thing worth mentioning is that thin-film (amorphous) silicon solar panels are affected by the so called Staebler-Wronski effect.
This effect causes a reduction of module efficiency over time. The main reason for this to occur is the defect density of amorphous silicon increasing under sunlight exposure.
About six months after installation however this effect reaches equilibrium and practically does not cause any further degradation of solar module’s output power.
Therefore, you should have in mind that during the first year of operation thin-film (amorphous) silicon modules produce about 10-15% higher energy.
After about six months of their 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 , during sunset and cloudy weather
- partial shading conditions
They are more suitable for non standard mounting conditions on facades as well.
Crystalline (mono- or poly-) PV panels are the most common solar panels for home and business photovoltaic systems. Nowadays, these types of solar panels account for 90 % of 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. Rectangular shape is the most common.
Every solar panel has nominal power rated in ‘watts-peak’ (Wp) or ‘kilowatts-peak’ (kW), also known as installed WpDC 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 Module-Solar System
- materials used to produce the solar panels
The video below sheds more light on this:
Before choosing the best type solar panel for your application the following variables must be taken into account:
- the prevailing climate conditions influencing the temperature’s impact on solar panel efficiency and the impact of the irradiance changes on efficiency
- available mounting area which determines the conversion efficiency of chosen solar panel
- solar panel warranty conditions and its manufacturer reputation
- your available budget 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 the a wrong decision.
After all, you don’t buy performance parameters you buy a better productivity in terms of kWh/kWp generated power provided at lower possible cost.
Why is it important to know more not only about the solar panels but also about the rest building blocks of a solar 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 key role in delivering solar electricity.
To produce the electricity used by your appliances a solar system needs not only solar panels but also additional components. 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 buildings blocks you may squeeze more power up to 30% more from the solar system while maintaining its price relatively the same.
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