Solar PV technology is not without its flaws. There exist shortcomings that prevent it from achieving its full potential as a source of renewable energy.
Solar Resource
A region’s solar resource refers to the average amount of solar radiation it receives on any given day. Also, known as insolation, this value differs between regions, and is often greater in dryer, more southern areas. The more solar radiation an area is exposed to, the more electrical energy that can be generated by PV cells. This puts regions with less solar resource at a disadvantage, as PV installations in those regions suffer from reduced capacity for generating electricity. [1]
Image via Solar Maps. (n.d.). Retrieved from nrel
Sun Intensity
The amount of solar radiation available at any given time is also dependent on the sun intensity. The time of day influences how much solar radiation is currently reaching a given area of land, the magnitude of which tends to be higher at noon than in the early morning or late afternoon. Furthermore, clouds and other weather effects can diminish the amount of solar radiation reaching ground level [2].
The time of day poses an especially significant problem for PV technology. The electricity generation by a PV cell is an active, flowing current. Since storing this energy results in energy losses, the usefulness of a PV installation is heavily dependent on the time of day at which the energy is being used. In the United States, electrical energy use tends to peak during the afternoon, when the sun intensity is reduced. This results in a disparity between energy demand and PV productivity.
Sun Angle and Positioning
An important point of consideration for designing PV power systems is ensuring that the cell arrays are facing towards the sun. In a region where the sun tends to shine from the south, a solar array that is oriented to face towards the north would provide little to no practical capability for producing electricity. In addition, the angle of the sun changes with the time of year, and can lessen a PV array’s generation capacity if it is not sufficiently angled to effectively receive the oncoming solar radiation.
To accommodate this phenomenon, PV modules can sometimes be installed on trackers that allow the module to continuously follow the sun. Such a system can yield an increase in energy production of up to 40% annually, in comparison to a typical fixed array [2]. However, this comes with the catch of driving up the already high cost of PV power systems.
Efficiency
Despite the immense amount of energy contained within the sun’s rays, solar PV technology is capable of harnessing only a small fraction of it. Even though the amount of energy produced does not make PV technology insufficient for meeting current energy demands, rising future energy needs will necessitate more efficient PV technologies. Currently, the most efficient PV cells are capable of achieving about 20% efficiency. Thankfully, PV technology is developing and advancing at an incredibly rapid pace, making the future for PVs promising.
Author: Rick Cerretani
Editor: Hannah Goldstein, Abby Studen, Kevin Jackson
Sources:
[1] Solar Maps. (n.d.). Retrieved from http://www.nrel.gov/gis/solar.html
[2] Patel, M. (2006). Wind and Solar Power Systems: Design, Analysis, and Operation (2nd ed.). Boca Raton, FL: Taylor & Francis.