Photosynthesis vs. Semiconductor based solar cell.
Instructor: Meri Stanec
April 24th, 2011
What is Photosynthesis?
Photosynthesis simply means the conversion of light energy into chemical energy by living organisms. In photosynthesis, the raw materials are water and carbon dioxide. Energy is taken from sunlight and the end products give out glucose and oxygen. It is the most important, naturally occurring process of life because all living organisms depend on it. In this process, plants use solar energy to produce sugar. then during cellular respiration, these sugars are converted into ATP. ATP is the fuel that is used by all living organisms. The conversion of the unused sunlight energy into usable chemical energy is associated with the actions of the green pigment chlorophyll. In this process, water is used and oxygen is released that we absolutely need to stay alive. we can write the over all reaction of this process as: 6 Water molecule’s + 6 CO2 molecule’s + light → 1 Glucose molecule + 6 oxygen molecule’s
How is solar energy transformed into electrical energy?
Solar energy is what keeps us all alive. The earths temperature is retained from the light and heat taken from the sun. how easily solar energy is converted into light energy is important. The Photovoltaic effect is a process through which the PV cells transfers light into electricity. sunlight is made of photons. these photons contain different amounts of energy. When they strike a PV cell, they reflect, absorb and pass right through. when a photon is absorbed, it turns into electrical energy. This energy is transferred to an electron in the semiconductor. then the escaped electron becomes a part of the electrical circuit which then provides the necessary voltage needed to drive electrical current into a light bulb. We all know that the new technologies will bring us more methods to conserve solar energy into large plants with facilities to store energy. At present cost and technology issues prohibit us to use solar energy abundantly.
How is a Semiconductor based solar cell similar to Photosynthesis? Both photosynthesis and semi-conductor based solar cells have many similarities. They both harvest light, water molecules and produce energy. In photosynthesis, sunlight is harvested through direct contact whereas in semi-conductor, it is done through photovoltaic panels. Just like chlorophyll harvests sunlight in plants through photosynthesis, the same way a semi-conductor absorbs sunlight. Both of these systems are of great value to us because the outcome of the outcome. Photosynthesis gives oxygen and other elements of life such as fossil fuels, petroleum, natural gas and coal. The light reaction in photosynthesis is also very similar to how electricity is created by solar cells. Light energy is captured in a solar cell, then it is transformed into a high level of energy where they are wired to run in semi-conductor motor (Virtual Biology). In both process electrons are lost which makes them similarly close. The lost electrons get replenished after the completion of the electrical circuit. This process is very similar to the electrons that are replenished by the splitting water in photosynthesis.
Differences between a Semiconductor based solar cell and Photosynthesis? Even though there are very similarities between the two systems, they also have many differences as well. Some of the differences are price, output and absorption. When comparing prices of the two, photosynthesis is a far superior process. Photosynthesis is everywhere and it’s inexpensive. The main component of photosynthesis is the plants. These plants are made of water, minerals and carbon. There is no labor required because plants essentially create themselves. on the other hand, a semi-conductor solar cells are very expensive and they are usually very limited. The Photovoltaic solar panels are made of silicon. Silicon is very expensive to make therefore making this process very costly. There is also a very dramatic difference in the outcome of both processes. In photosynthesis, plants use sunlight as the source of energy input to perform energy conversion, which turns carbon dioxide into organic matter(Hunter, 2004). On the other hand, a semiconductor based solar cells allow immediate conversions of sunlight to electricity. a greater transfer of photons to electrons happens in photosynthesis. The Photovoltaic materials in a Semiconductor based solar cell can absorb energy from a broader portion of the color spectrum gathering more photons whereas in photosynthesis plants can only absorb light from the blue and red sections of the color spectrum resulting in tiny portions of photons.
The Laws of Thermodynamics:
The laws of thermodynamics describe the relationship between heat, work, and energy. Conservation of energy: This law states that energy cannot be created or destroyed. Energy can only be changed (Cliff Notes, 2010). In photosynthesis, this law is expressed because energy is not created by plants here, it is only transformed from sun’s energy into food when it produces oxygen and carbohydrates. This law expresses the same dynamics in a semiconductor based solar cells production of electricity. The energy of the sun is not created. It is only transferred by Photovoltaic panels to the semiconductor and there it is changed into electricity. Entropy: This law states that the quantity of the energy stays the same and the quality of the energy deteriorates because of the lost energy in the environment (Physics Planet, 2004). Further investigation into both of these processes indicates that the absorbed heat from the sun cannot be expelled in the air. Absolute Zero: This law states that it is not possible to reach absolute zero. it relates to these two processes in the same way because as the sun’s temperature decreases, it gets closer to absolute zero conversion and extraction of energy grows increasingly challenging therefore; creation is not possible without heat and energy.
In conclusion, both of these processes have many similarities and differences when processing energy. In contrast, they are identical in accurately reflecting the laws of thermodynamics. i believe both processes are great ways to go green and necessary to sustain life.
Mader, S. (2010) The Energy For Life. Essentials of Biology, (pp 85-98). McGraw publishing. Strayer University 2009 custom edition.
Virtual Biology Course is an on-line A-to-Z reference of biology maintained by Dr. Paul Decelles and is part of the Johnson County Community College website. The goal is to cover the major concepts of biology. The website covers a variety of topics ranging from evolution to human organ systems and classification. (http://staff.jccc.net/pdecell/photosyn/solar.html). CliffsNotes.com. (2010, October 25) Laws of Thermodynamics. Retrieved from http://www.cliffsnotes.com/study_guide/topicArticleId-23791,articleId-23691.html Hunter, P. (2004, May 14). The promise of artificial photosynthesis. Prosper Magazine. Energy Bulletin. Retrieved from http://www.energybulletin.net/node/317
Physics Planet is an on-line A-to-Z reference of physics. The goal is to educate visitors on various aspects of physics. The website covers a variety of topics ranging from astrophysics to forces and scientist. (http://www.physicsplanet.com/articles/three-laws-of-thermodynamics).
Hunter, P. (2004, May 14). The promise of artificial photosynthesis. Prosper Magazine. Energy Bulletin. Retrieved from http://www.energybulletin.net/node/317