Photovoltaic systems of Solar PV systems do not emit greenhouse gases while operating either, making it a much cleaner alternative energy source. However, the main reasoning behind why solar power hasn’t over run traditional energy sources is because of its dependence on an energy input that isn’t available 24/7 - the sun.

What is Photovoltaic Solar Energy?

There are two main types of solar energy technology: photovoltaics (PV) and solar thermal. Solar PV is what you see on the rooftops of homes and businesses. This type of technology produces electricity directly from solar energy. Solar thermal technology generates heat by using the sun’s energy, which them generates into electricity.

According to the Director of the Centre for Sustainable Energy Systems (CSES), Andrew Blakers, “Australia receives thousands of times more solar energy from the sun each year than all fossil fuel use combined. We directly use only about one millionth of this at the moment as commercial energy.”

How does Photovoltaic (PV) Technology Work?

In a photovoltaic cell, sunlight detaches electrons from their host silicon atoms. Electrons capture tiny packets of light energy called photons. These photons impart enough energy to kick the electron free of its host atom. There is a ‘one way membrane’ called a pn-junction near the upper surface of the cell and is formed by diffusing tiny quantities of phosphorus to a depth of approximately one micrometre into a thin wafer of silicon. A negative voltage will appear on the surface facing the sun once a free electron crosses the pn-junction, and a positive voltage on the rear surface. The front and rear surfaces can be connected via an external circuit in order to extract current, voltage and power from the solar cell.

Solar cells are stored behind glass to form PV modules, which have typical service lives of 20 to 40 years.

Is Solar Economically Viable?

PV modules on building rooftops can generally produce as much electricity as the building consumes. A typical module will generate about 200 kilowatt hours (AC) per square meter per year. So, to power a reasonable energy efficient home in Australia, an area of 25-50m2 is needed.

According to the University of Melbourne’s Energy Research Institute, solar energy costs will compare favourably with traditional fossil fuel technology in the very near future.

The report, the Renewable Energy Technology Cost Review May 2011, was commissioned by government climate advisor Ross Garnaut. During this study, leading researcher Patrick Hearps said, “We found that the current cost of technology such as solar and wind today are already cheaper than the data that is currently used by Australian Government and industry planning. Not only that, the cost of solar and wind are expected to drop quite significantly over the next decade.”

Evidently, solar power will be capable of displacing fossil fuels when energy storage becomes cheap. When the cost of generating, storing and retrieving one kWh of solar energy becomes less than the cost of generating it with natural gas or coal, it is predicted to become the main energy source used by society.

Energy Storage Systems for Solar Power

Finding a cost-effective energy storage system that allows solar energy to be used during night time or on cloudy days, without increasing its cost drastically, is still a key challenge to overcome. Another thing to keep in mind with energy storage systems is that they also have financing, operation and maintenance costs, which must be added to the kilowatt-hour price.

Many energy storage technologies have already been installed successfully, including pumped-storage hydroelectricity, lithium-ion batteries and thermal storage. However, each case is different, so an analysis is necessary to determine the best energy storage system to complement solar power.

Pumped-storage hydroelectricity (PSH) is the term used for a hydroelectric power plant that is built between reservoirs of water at different elevations. Water is pumped upwards with surplus energy from another generation system, and the facility generates electricity with turbines as needed. Normally, the turbine and generator sets are reversible, which means they can operate as motors and pumps, which combines equipment. The cost of PSH can vary significantly and is financially viable only when site conditions are very favourable.

Lithium-ion batteries are probably the most promising source at the moment, since they have two qualities that have made solar power successful. These qualities are a modular design that allows flexibility in system capacity, and having very little dependence on site conditions. Lithium-ion batteries are viable in places with very expensive electricity during peak demand hours, such as Australia, making them an attractive investment for homeowners.

Thermal energy storage is application-specific. If you need hot water at night, you can use left-over energy from a solar PV system to heat the water and then store it in an insulated tank. For cooling applications, the same concept applies. Left-over solar energy can be used to chill ice for the night, reducing dependence on air conditioning or other cooling appliances.

Conclusion

Solar power has demonstrated to be economically viable and does pay for itself. However, there are several variables that determine economic viability, remembering that each situation is different. These include the level of sunlight and efficiency of your cells and ROI (return on investment), the initial cost of buying the cells and installing, how energy efficient your home is, how much energy you use and your energy needs now and in the future.

In conclusion, solar is a viable alternative clean energy source. Although it may not be affordable for everyone, if the costs of solar technology drops, the existing energy costs rise, or solar panels become more efficient, than solar energy will be viable for many more people in the future.