Photosynthesis vs. Solar Cells: Producing

Photosynthesis vs. solar cells: Producing natural and human-Generated energy

Photosynthesis, an organically-occurring chemical process, is used to sustain essential life forces. Without the ability to convert light into energy, plants (and in some forms of bacteria and simple organisms known as protistans) would not be able to create the necessary sugar compounds required for them to grow and flourish. Without plants, animal life on the earth would not exist as we know it. This is because one of the byproducts released in photosynthesis is oxygen, while plants 'feed' off carbon dioxide to complete the chemical reactions of photosynthesis (Farabee 2007).

Photosynthesis in plants converts the light of the sun into a usable source of energy for living organisms in a natural fashion. Solar cells likewise convert the natural light of the sun into energy. However, the use of semiconductor-based solar cells, while useful, is a non-necessary, human-generated process designed to increase the convenience of modern life at relatively low cost. One common example of this technology is found in solar-powered calculators. Solar cells also convert the sun's heat into electrical energy. Because the conversion is not a chemical process like photosynthesis, no necessary gases are released and no food is generated for the organism.

It should be noted that in photosynthesis some electrical transfers do occur. "The first two steps of photosynthesis involve capturing photons released from the sun and using that energy to create a flow of electrons. From there, photosynthesis involves using that electrical energy to create chemical energy, from which ultimately the products of photosynthesis are created" in the form of glucose (Stier 2009). Solar energy captures the same photons and uses the energy to create a flow of electrons that generate heat (Stier 2009). To enable solar cells to trap energy, the cells are constructed with two layers of semiconductor material, one of which has positively-charged material with a low electron concentration, the other of which has negatively-charged material with a high electron concentration. "The space where these two layers come in close contact is known as the p-n junction. As light heats these sensitive semiconductor layers, a flow of electrons is ignited, resulting in a direct current which ultimately results in electricity" that generates enough energy to power a device or can be used to heat an entire home (Stier 2009). In contrast, in the process of photosynthesis, energy is trapped by the plant's physical structures known as chloroplasts, which contain chlorophyll. Chloroplasts are similarly constructed of layers of material like a solar cell: the grana and the stroma that make up the structural unit of the chloroplast, the thylakoid. "The areas between grana are referred to as stroma….the chloroplast has three [membranes] forming three compartments" (Farabee 2007).

Solar cells are usually manufactured from silicon, a 'naturally' occurring material. However, unlike chlorophyll, silicon cannot be used for energy-generation in its raw state, and must be processed by humans. Silicon is favored "because it remains a good conductor of electricity even after it has been heated. In order for silicon to be used for solar cells, it must be heavily heated to separate it from oxygen so that it can be further processed" (Stier 2009). Although solar energy is widely touted as a 'green' technology, the actual manufacture of silicon cells is relatively labor-intensive and results in the burning of a considerable amount of fossil fuels. In contrast, the photosynthesis that takes place in plants is truly 'green' (no pun intended). "Plants are able to create their 'solar panels' relatively inexpensively, so much so that in seasonal climates they regularly shed their leaves and rebuild them the following year using a clean, low-power energy source; out of locally-available and life-friendly materials; and which decompose into nutrients that sustain soil organisms whose by-products ultimately support the continuing growth of plants" (Stier 2009). Plant solar energy is thus naturally part of the 'circle' of life on earth and plants naturally recycle the cells used in photosynthesis.