Efficiency of a 40w solar panel is an important factor when using it as a viable power source – the higher the efficiency then the more cost-effective installation will be . Constant research is bringing results however, and development of this technology and improving efficiency of solar cells is the main area in focus.
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.
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.
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%
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.
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).
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.