Photosynthesis Vs Photovoltaic - Essay Example

Photosynthesis Vs Photovoltaic According to Dictionary of Botany (n.d Photosynthesis is “the sequence of reactions, performed by green plants and photosynthetic bacteria, in which light energy from the sun is converted into chemical energy and used to produce carbohydrates and ultimately all the materials of the plant.” The basic photosynthesis process is divided into two stages: Light Reaction and Dark Reaction. In the Light reaction, energy is captured in the cells which produce energy carrier molecules that are further used in dark reaction.

In the dark reaction, products of the light reaction are used to make C-C covalent bonds of carbohydrates. The photochemical reaction is as follows: 6H2O + 6CO2 + Light ---------> C6H12O6 + 6O2 Solar cells or PV cells are made up of a semi-conductor material like silicon etc. The incident sunlight is absorbed by the material; the solar energy knocks out electrons from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting photons to electrons is called the photovoltaic (PV) effect.

When we cast a glance at the structure and functioning of both the plant and solar cells, we come across various similarities and differences. The prime similarity in both the cells is the excitation of electrons to a higher energy level by the incoming photon of sunlight. In plant cell, it is done within a chlorophyll molecule whereas in solar cell, it occurs within a semi-conducting material like silicon. Both the plant and solar cells absorb sunlight and convert it into useful form. In plant cell, sunlight is utilized to synthesize carbohydrates and form a basis for sustaining the life processes of all plants.

In solar cell, incident sunlight is converted into electricity which is an essential need of human beings on Earth. The plant cell contains a green pigment called Chlorophyll which serves two functions. It is used to absorb the sunlight and then utilize this light to excite the electrons. In solar cell, an organic dye is used which is coated on the crystals and it serves the same function as the chlorophyll in the plant cells i.e. it absorbs the light and produce an electron flow. As like similarities, there are differences too between plant and solar cell.

The primary difference is that plant cell stores sunlight during light reaction and can even synthesize carbohydrates during night time. Whereas solar cell is only effective when direct sunlight is incident on it. Its efficiency is almost negligible during cloudy season. Plant cell converts sunlight into chemical energy by the photosynthesis process and solar cell converts it directly into electrical energy which is then used by humans. Photosynthesis is a natural process which is automatically carried out in all plants but electricity generation by solar cells is an artificial procedure.

Solar cells need to be installed for this purpose and it requires much investment. Therefore, they are much expensive as compared to plant cell. Another significant difference between both cells is that the bad photosynthetic cell can repair itself whereas there is no such provision in case of solar cells. Both photosynthesis and photovoltaic energy conversion systems deal with transfer and conversion of heat energy into another form. Thus both systems should show compatibility with the Laws of Thermodynamics.

The first law of thermodynamics accounts for the energy conservation of heat systems i.e. energy cannot be created nor destroyed, it only transforms from one form to another. According to (Cengel & Boles, 2006), “A change in the internal energy of a closed thermodynamic system is equal to the difference between the heat supplied to the system and the amount of work done by the system on its surroundings”. Both plant and solar cells do not create energy but rather convert one form (solar irradiation) of energy into another (chemical or electrical).

The second law of thermodynamics explains the phenomenon of irreversibility in nature. A certain amount of "transformation energy" will be used as the molecules of the "working body" do work on each other when they change from one state to another. During this transformation, there will be a certain amount of heat energy loss or dissipation due to intermolecular friction and collisions; energy that will not be recoverable if the process is reversed. We know that both photosynthesis and photovoltaic energy conversion systems are not 100% efficient and dissipate heat energy during their respective processes which is according to the second law.

References: Photosynthesis. (n.d.). In Dictionary of Botany. Retrieved from http://botanydictionary.org/photosynthesis Pierret, R. F. (1996). Semiconductor Device Fundamentals (2nd Ed.). Boston, MA: Addison Wesley. Cengel, Y. A., & Boles, M. A. (2006). Thermodynamics: An Engineering Approach (5th Ed.). New Delhi, India: McGraw-Hill. Gunning, B. E., & Steer, M. W. (1996). Plant Cell Biology: Structure And Function. Burlington, MA: Jones Bartlett Learning.