For centuries humans have surrounded their entire cultural and technological advancement on the back of fossil fuels such as oil, petroleum, coal, and natural gas. However, as fossil fuels continue to be consumed at alarming rates in order to fuel today’s heavily electric society, so has the concentration of greenhouse gasses, mainly carbon dioxide, which has been a leading cause of man-made climate change. Climate change is caused when excess gasses in the Earth’s atmosphere traps the sun’s light, heating the planet in the process.
This heating of the planet can result in catastrophic weather patterns that can prove un-beneficial for the species who inhabit it. In order to combat this growing issue, scientists have created and continue to improve upon alternative energy solutions, the chief among them being solar cell, which captures the sun’s rays and converts them into electricity. Reason being, the sun is a great resource and will be around for millions of years.
Although solar cells are environmentally friendly, they are not the most efficient when compared to fossil fuels, however, scientists are looking for ways to improve upon them and are also searching for other methods of harnessing solar energy.
Solar cells are comprised of two types of semiconducting layers, called the n-type and p-type silicon, with the n-type silicon overlaying the p-type silicon. The n-type silicon carries a negative charge since it carries phosphorus atoms and phosphorous atoms contain one more valence electron on its outer shell than silicon. Once phosphorous binds to its silicon neighbors, an electron remains to wander the silicon structure.
(ACS, 2015). The p-type silicon, which carries either boron or gallium atoms, is positively charged because boron has one less valence electron than silicon and once its bonded it creates a ‘hole’. Near the joining of the two layers, electrons move from the n-type to the p-type layer to fill these ‘holes.’ Once sunlight shines on the cell, photons bombard the surface and carry their energy through the cell. Then photons release their energy to the electrons in the p-type layer, and the electrons use this energy to jump across the border into the n-type layer and escape out into a circuit. This provides the energy needed to power any system.
Although many individuals have made the migration towards solar cells for commercial or recreational use, inefficiencies still linger (IISD, n.d.). The major issue that infects the further growth of solar cells is the loss of efficiency at higher temperatures. Photovoltaic cells, as mentioned earlier, use semiconducting silicon to convert the energy from photons into electricity, however, they cannot utilize heat, a form of electromagnetic radiation. This heat from unused sunlight accounts for a loss of more than 50 percent of the initial solar energy (2010). In order to remedy this, a group at Stanford University has developed a technology, called PETE, that weds thermal and solar cell technology; by coating a gallium arsenide semiconductor with a thin layer of the metal cesium, it made the material able to use both light and heat energy to generate electricity. Moreover, while silicon solar cells have become impotent as temperature increases, the PETE device doesn’t hit peek inefficiency until its well over 200 degrees Celsius. Another limiting factor in the development of solar power is cost, but the PETE system is cheap to produce because of the amount of semiconductor needed is quite small when compared to its silicon counterparts.
Another method that is currently being invested in are concentrated solar plants. Concentrated solar plants utilizes the suns energy by using mirrors to focus the sun’s energy onto a small area which generates heat that is directly transferred to a molten salt. The molten salt then heats a ‘working’ fluid to create steam to drive a turbine that generates electricity. Concentrated solar plants run on thermal energy without producing any of the harmful greenhouse gasses, unlike fossil fuel power stations that do produce harmful greenhouse gasses. Moreover, they can harness great amount of sunlight that can be stored and dispatched on demand at any time, unlike their solar cell counterpart. Alternatively, they do not work well on cloudy days and are very costly since they take up incredible amounts of land and require lots of maintenance. Luckily, a team at Purdue University is experimenting with zirconium carbide and tungsten to replace stainless steel heat exchangers, which transfer heat from the molten salt to the ‘working’ fluid. These compounds that they are experimenting with can generate even more electricity with the same amount of heat. This option could help lower the cost and increase energy input.
There are currently solutions to the inefficiencies that burden solar cells. There are materials that can substitute the current one’s that produce more electricity with minimal cost. Other methods involve a concentrated solar plant that can harness great amounts of sunlight that can compete with fossil fuel power stations in terms of energy production. Hopefully, through the implementation of solar power, the human race can help to minimize greenhouse gas emissions and in doing so slow down climate change.