How to Increase Solar Panel Efficiency? What Makes A Solar Panel More Efficient?
When scientists started to explore this technology in 1839, they forecast that the efficiency of solar cells would reach 1% efficiency by 1948 – this was considered to be good. Today we have solar cell technologies reaching 40% efficiency or more, but with a big cost and generally used for specialist endeavors like NASA’s space exploration.
But what about us down on earth?
There are three common methods used to maximise solar panel efficiency: Solar concentrators which concentrate sunlight more intensely, solar mirrors which reflect more light onto the solar panel area and auto-tracking, which follows the sun as it moves across the sky.
What are solar cells made of and how do they work?
The solar panel, also known as solar module, is technically termed PV or photovoltaic. It is made up of a number of individual solar cells. These solar cells define the type of solar panel.
Some panels are black and some blue in color. Some have diamond white shapes in between the horizontal and vertical lines and some don’t have those diamonds.
The color, the design and the size of solar panel depends on the type of solar cell used. The shape of solar panel is designed to get the maximum use of available area and the rectangle shape just makes it more “handy” and cheaper to manufacture.
Basically, the core of electricity generation from a solar installation is the solar cell.
There are many types of solar cells. The main three types which are being used and are available in the market today are:
- Mono-crystalline or single silicon crystal
Poly-crystalline or multi-silicon crystal
Thin-film (can be amorphous silicon or other substances like cadmium, copper and gallium etc)
The efficiencies of these three types of solar cells are:
- Mono-crystalline : 22%
- Poly-crystalline: 15%
- Thin-film: 10%
|
TYPE |
Monocrystalline |
Polycrystalline |
Thin Film |
|
COMPOSITION |
One crystal |
Multiple crystals |
Thin silicon layers |
|
EFFICIENCY |
Up to 22% |
About 15% |
Maximum of 10% |
|
LIFETIME DURATION |
25 to 30 years |
20 to 25 years |
15 to 20 years |
|
COST |
Expensive |
Cheaper |
Expensive |
Even the highest efficiency of monocrystalline solar panels is not too good from a lay-man’s perspective. Why so low? In these highly technological times it seems incredible that we can’t have super-efficient photovoltaic cells to use in out homes.
Why are solar panels so inefficient?
These solar cells are so inefficient because of the manufacturing process, the material they are made of and the process by which these materials generate electrical power.
The sun’s light is also made up of packets or photons of energy. These photons strike the solar panel and exchange their energy with electrons in the material which start flowing across silicon P-N junctions and start generating current.
The process of energy conversion and the loss of energy within the process depends on the type of solar material (silicon) used to make the solar cells.
In the case of silicon material based solar cells, when they receive sun’s energetic photons of light, they loose 23% of their energy because they are not energetic enough to energize electrons in the silicon crystal lattice.
A further 33% are so energetic that when they strike solar material, energy is lost in form of heat.
Around 16% is lost by the electrons themselves during the process. Theoretically, solar cells made from silicon can reach maximum efficiency of about 33% but for practical purposes practically the maximum efficiency for commercial solar panels is 22%.
Silicon-based solar cells have been recorded at 40% efficiency in laboratory conditions and other materials do exist that have photovoltaic properties. These are too expensive at the moment so silicon solar cells are the only game in town for the moment.
NASA’s Glenn Research Centre has developed a hybrid solar cell made up of silicon, thin-film materials and selenium with efficiencies ranging from 30% – 40%.
If the cost of production is brought down, this could be the future of solar cells with double the efficiency of existing solar cells.
What Is Irradiance And Insolation?
The efficiency of electricity production from a solar panel also depends on the amount of sunlight falling on its surface.
Two solar terms used are important in understanding the solar energy falling on Earth and how we measure it. It’s a way of measuring or calculating how much electricity we can generate from our solar panel.
- Irradiance is the power (amount of energy per unit time) of sunlight per unit area (Watt/sq. m or W/m2).
- Insolation is the energy of sunlight per unit area over time (kilo Watt hour / sq. m or kWh/m2).
When insolation is high, the higher the electricity production from solar panels and better efficiency. For fixed solar panels this does not happen continuously as they do not face the sun throughout the day.
This is the reason fixed solar panels are inefficient during either side of mid day, even if the solar panel array is placed at exactly the best angle from the ground and is facing south (if in Northern hemisphere).
How to make solar panels more efficient using a solar concentrator
The use of a solar concentrator for solar panels can increase their efficiency up to 40%. Some companies have commercialized this technology and it is quite efficient, if a little expensive.
A lens called a ‘Fresnel lens’ is used to concentrate sunlight onto solar cell. These solar cells are made depending on the concentration level of the lens. Low concentration lenses work with silicon cells and do not require tracking or cooling.
Medium strength concentration lenses work with silicon, cadmium and telluride solar cells which require some cooling and tracking.
High concentration lens work with multi-junction or multi-material cell and require extensive cooling and tracking.
Concentrating solar panels are made in a specific way – they are not like traditional solar panels. The sunlight concentrates on a very small area where the solar cell is placed.
Concentrating sunlight on a traditional solar panel is not much use and can harm the solar panel with excess irradiance leading to heat, which also reduces overall efficiency anyway.
Increasing solar panel efficiency with mirrors – solar reflector panels
Research is underway, and it is very promising, for improving solar panel systems. Various researchers in the USA and India have tried adding mirrors adjacent to the solar panels. These mirrors when kept at specific angles tend to increase electricity production from panels up to 30%.
Over-heating of solar panels is to be avoided if this technology is to be commercialized but it will be a blessing for colder regions with high insolation levels. One work published in IEEE’s Journal of Photovoltaic’s proves the successful use of mirrors as reflectors in solar farms to increase its energy output.
How to increase solar panel power by optimizing panel’s angle
Ideally the solar panel should face the sun perpendicularly and this happens when it is placed at a specific angle with relation to the ground. For a fixed solar panel at a specific angle from the ground, the sun’s energy striking a solar panel is maximum only during mid day.
If you are in Northern hemisphere, the solar panel should face south and if in Southern hemisphere it should face North. The angle of solar panel at which it should be inclined from the Earth’s surface is different for different locations on Earth.
There are number of calculations to get to the exact angle of solar panel to get maximum efficiency for a particular location. Even so, fixed orientation of the panel is not optimum for reaching maximum power generation. These calculations are either done manually or using algorithms.
The simplest is keeping the tilt angle +15o of latitude of the location for winter and -15o for summer. Also the tilt angle can be changed four times in a year to get maximum efficiency from a fixed solar panel.
However, it is best to keep tracking the sun’s movement and to generate maximum energy all time of the year, which is expensive but brings much higher returns on the investment for the tracking equipment.
Seasonal and regional differences in irradiation or insolation levels
A free source for checking regional variations in insolation levels is provided by from NASA as the Power Data Access Viewer. Getting some basic information about yearly insolation level at your location can give you a good idea about the potential of solar energy and how much electricity you could generate per square meter of solar panels.
How to increase solar panel output by automatic solar tracker
We cannot stop the clouds blocking the sun, so we obviously lose out there but when sun is tracked by the solar panel like a sunflower does it is operating at its maximum efficiency.
The two types of tracking – single axis and dual axis.
Single axis tracking boosts the power output from solar panel by 20% and dual axis tracking boosts it by 30%.
The graph below published in a study done on efficiency of single and dual axis tracking shows the comparison of single and dual axis tracking panels to that of fixed panels.
The comparison of fixed mount solar panel with single tracker on left graph and dual tracker on right graph can be seen above.
The early peaks at 8 in the morning and 6 in the evening clearly indicate the potential of dual tracker to increase the efficiency of solar panels across daylight hours. If our solar panels can be made to track the sun through dual axis rotation, it’ll be the best thing to do to increase efficiency.
A couple of motors and radiation sensor makes it easily possible and should be considered for all domestic solar installations.
How to measure solar panel power output
The solar panel should be getting full sunlight from facing the sun at the optimum angle and then you find out the wattage of the solar panel at that particular instance.
- Wattage = Amps x Voltage
To calculate wattage of a solar panel you need to get amperage and voltage from the multimeter and multiply them together.
Check the back or side of the panel to find its open circuit voltage (Voc) and operating current as (Imp). Taking these as reference you can check the solar panel by connecting its wires to the multimeter and optimize it to check current and voltage.
Discover your solar saving potential
A good way to test a solar panel watts output across its range is to have a means of short-circuiting the leads (it won’t be damaged) and sweep the voltage up to it’s maximum in steps while measuring amps x volts at each step.
This is a great way to derive a power output curve and will show any discrepancies in output power for different loads. Short-circuit current (Isc) is very close to full power rating current anyway, so it isn’t harmful to the panel.
Related Questions
Why do solar panels face south?
Solar panels should face South in the Northern hemisphere as the sun tracks across the sky in that direction. In the Southern hemisphere solar panels should face North.
How are solar panels manufactured?
Monocrystalline solar panels are manufactured by connecting individual solar cells grown from a single tubular ingot of silicon. Polycrystalline solar panels are manufactured by cutting silicon slices form a large silicon crystal and connecting them together.
How do I maximise the efficiency of solar panel?
There are three common methods used to maximise solar panel efficiency: Solar concentrators which concentrate sunlight more intensely, solar mirrors which reflect more light onto the solar panel area and auto-tracking, which follows the sun as it moves across the sky.
