The global energy demand is increasing with the increasing population. In contrary, the fossil fuel reserves are being exhausted day by day. Fossil fuel meets about 80% of the world’s energy demand. As these sources of energy are limited and cannot be reused, our planet is going to face energy crisis. In addition, the emission produced by the combustion of fossil fuels also contributes to air pollution & global warming. To meet the ever increasing global demand for energy, there has been substantial interest in developing renewable biologically produced fuel.
Here, the approach of BPV holds a promising future. BPV stands for Bio-Photo-Voltaic. The appeal of BPV lies in its ability to harness a natural process that takes place all around us. BPV devices generate electricity from light energy by exploiting the photosynthesis of living organisms such as cyanobacteria, moss, algae and vascular plants. Photosynthesis is a process which uses carbon dioxide and water, in presence of chlorophyll, to make glucose and releases oxygen. A general equation for photosynthesis is given below:
6CO2 + 12H2O + photons C6H12O6 + 6O2 + 6H2O
Biophotovoltaics (BPV) devices are biological solar cells that generate electricity from photosynthetic activity of living microorganisms such as algae. In the presence of sunlight, algae undergoa series of chemical reactions, splitting water into protons or Hydrogen ions, electrons and oxygen. These are the main ingredients for transforming carbon dioxide and other inorganic materials into carbohydrate & proteins which also promote algal growth. BPVs exploit this charge separation to generate electrical energy. This is achieved by placing algae inside one of the two electrodes-containing chambers separated, by a membrane that only allows protons to pass. Electrons produced during photosynthesis flow through external circuit in order to recombine with protons and oxygen at the reductive cathode, forming water. The resultant current flowing in external circuit can be used to power electronic devices.
Algae, the bio-electrical catalysts, require only water and sunlight for their survival & generating electricity. The oxygen produced at the anode escapes into the atmosphere, while the water produced at cathode can be harvested or left to evaporate. No harmful chemical waste is produced during the process, and other than algae, lily and lotus pads and moss can also be used for generating electricity. BPV technology uses also include desalination of water and co-generation of chemicals as formic acid which can be further used for fuel along with the production of hydrogen. Low-cost BPV devices are likely to become alternatives to silicon-base photovoltaic cells, because the algae need to be kept in water &, also along with this, algal material is self-renewing over a long period of time, which means that BPV cells will be useful in a different set of applications than traditional solar cells, and may even open up some radically new approaches to the generation of green electricity.