Solar Energy Efficiency

When dealing with Solar Energy and related solar systems, whether Photovoltaic or Solar Thermal, one of the factors and attributes which will of concern would be their Energy Efficiency. Solar Energy efficiency, SEE, concerns the manufacturers as well as the end users, the home or business owners. It is a coefficient and a factor which plays a significant role in the selection process of a solar system. Solar Panel efficiency is a factor which affects the selection of solar panels.

In order to understand the meaning and importance of Solar Energy Efficiency, SEE, we should understand the related terms so that we would have a common understanding and foundations.

Energy Efficiency

Energy efficiency in simple terms is the result of an effort for using less energy in order to provide the same product or service. We often talk about the energy efficiency of a system or a device or a machine. Energy efficiency should not be confused with energy conservation since energy conservation implies reducing or eliminating the need of a service in order to save energy.

The Energy Efficiency formula is simply: (Output Energy/Input Energy) x 100 and the energy efficiency term given as a percentage.

There are many examples of Energy Efficiency efforts. Insulating a house means that we will need less energy to heat it and cool it and this result to the saving of energy and money.  The action or the effort in this example is the insulation and this results to the need of less energy to bring the house to the same desired temperature. In the case of homes there are special programs which perform energy audits in order to identify energy efficiency improvements. In the US and in many parts of the world there are specialists and solar companies who do home energy evaluations.

Energy Rating

Energy rating refers to effort and initiatives to rate systems, products and appliances in regards to their energy efficiency. Improving energy efficiency results to significant benefits both financial and environmental as it reduces running costs for households and businesses and at the same time reduces the impact on the environment with less gas emissions. Devices, products and appliances carry the Energy Rating Label, ERL, which indicates their efficiency conformance and efficiency. For houses we have the House Energy Rating which is an index of the house’s thermal performance, which is the house’s heating and cooling requirement.

Solar Energy Efficiency

If we strictly take a look at the energy efficiency formula we can deduce that any energy we manage to have from a solar system as an output is a gain since the input to a solar system is from a Renewable Energy Source, RES, which is wasted if not used. So any amount of energy is used from the Sun is a gain and helpful to mankind and the environment. It should be noted that the solar energy falling on earth for about 20 minutes if collected would be enough to power the whole earth for a year!!

In order to maximize solar energy efficiency there has been research and improvement of the efficiency of the solar panels which collect the solar energy and they either convert it to electricity, Photovoltaic, PV, Panels, or heating, Solar thermal panels.

There are two widely accepted methods of measuring the Photovoltaic Solar Panel efficiency.

  • The first method is the percentage of solar energy which is converted into electricity and the figure is given as a percentage number with the most efficient PV panel having around 15% efficiency. The theoretical limit of silicon and indium-tin-oxide solar cells is 33.7%. 15% efficiency may be considered low and for this reason there are Concentrated PV, CPV, systems which may achieve 40% efficiency but they are too costly and they are not widely used yet.
  •  The other method of measuring PV efficiency is by measuring the energy density of the panel. Energy density is measured in Watts per square foot which is essentially the electrical output of the solar panel per unit area. The most efficient panels have energy density of around 14W/ft2

The recent explosion of 3D printing and its use in solar cell manufacturing may help in the increase of efficiency of the solar panels by at least 20% while at the same time decrease the cost by 50%. There is a belief that 3D printing may revolutionize the PV panel industry as it does for other sectors since it helps manufacturers overcome certain manufacturing issues and would be able to produce 3D solar panels.

There is no doubt that Solar Energy Efficiency needs to improve if we are to capture the Sun’s full potential. Research and Development is in that direction and given the fact that solar energy is a renewable energy source the benefits for achieving high efficiency rates will be multiple and beyond the financial arena.