FEASIBILITY STUDY OF BACTERIA POWERED SOLAR CELL FOR FUTURE POWER GENERATION
Contents
6.2 Dependence of costs on different factors 14
INTRODUCTION
1.1 Energy
Energy is the fundamental source of life. It is present everywhere, however, it needs to be converted to particular forms in order to make it usable by humans. Energy accessible to humans is broadly divided into two types depending upon the availability of the amount of the source. Some forms of energy are in-exhaustible and will be available for practically unlimited period of time while others are very limited and may end up soon on excessive usage. These two broad categories are renewable and non-renewable sources of energy. Out of it, the area of interest is the non-renewable sources of energy since they are sustainable and cheaper than its counterpart. As such, it is a need to harness these sources and convert them into usable form. The technology to convert different forms of energy such as wind energy, solar energy, tidal energy etc. into the usable form of electrical energy has evolved continuously in the past hundred years with improvements in the design and the results being an increase in the efficiency during this process to get maximum amount of electrical energy. [7]
1.2 Solar Energy
Sun is the biggest and most easily accessible renewable source of energy. As such, solar energy has the biggest potential to replace fossil fuels for the generation of electrical energy. The UN said in its World Energy Assessment in 2000, that Solar energy can potentially provide 1,500 - 50,000 EJ of energy annually whereas the required demand is only 600 EJ in 2012. Hence, this sector deserves utmost attention for its technological development through research and analysis. If achieved, it will cut down the environmental pollution due to burning of fossil fuels completely, provide essentially never exhausting source of energy, cut down costs of energy production and benefit the entire global population in numerous other ways. [2]
1.3 Electricity Generation
WORKING OF A SOLAR CELL
2.1 Solar cell
2.2 Photovoltaic effect
2.3 How is electricity produced
Solar cells use three processes to produce electricity. These are:
Light absorption through the surface of the material, creating electron-hole pairs: The sunlight contains photons which have momentum due to the velocity of light, and hence can displace electrons in suitable materials from their position in the material creating an electron hole. This hole will then be filled by a positively charged ion.
ROLE OF BACTERIA IN PRODUCTION OF CURRENT
3.1 Functions of bacteria
Oxidation of water: The cyanobacteria used for this process produces hydrogen gas as a by-product, by oxidising pure water, especially free from nitrogen containing organic compounds. By this decomposition, electrons are released at the anode which is separated from the system using a semi-permeable thin film. This is transferred at the cathode with higher potential to complete the circuit.
Reduction of anode: This type of solar cell utilizes replaceable anode sections for creating the oxidation reactions using sunlight as the source of energy for the photosynthesis. Again, electrons are produced as a result of this reaction and are transferred at the other end of the circuit to achieve electricity flow.
PREVIOUS ATTEMPTS
Biological Photovoltaic (BPV)
cells: These are biological electrochemical cells which are used to
convert light energy into electricity. It works by the photolysis of
water at the anode and a high potential generating chemical reaction at
the cathode in the presence of living organisms, thereby creating a
potential difference and generating electricity. Since the bio-organisms
are able to regenerate themselves, these type of cells can potentially
be used to generate electricity indefinitely using the sunlight as a
source of energy for photosynthesis.
As an example of these type of cells, we can study the biological photovoltaic fuel cell, which uses water and sunlight as the only input. In the anode side, water is oxidised to its components and electrons are released. The higher potential at cathode then drives these electrons in an external circuit resulting in flow of electricity. If water can somehow be regenerated, it will only need sunlight as input. Also, at cathode, the protons released can be combined to release hydrogen gas which will be useful by product of the process.
NEW BIOGENIC SOLAR CELL
5.1 Type 1
Biogenic solar cells are evolving continuously with each advancing year in an effort to increase the efficiency and feasibility. A recent study in 2018 developed solar cells with double the production of electricity than the existing ones. The study was carried out by researchers from the University of British Columbia (UBC). [4]
This newly developed technology utilizes biologically engineered bacteria with advances setup to produce higher amount of electricity. The bacteria which was used is the readily available E. coli bacteria. It was modified genetically to mimic the carotenoid biosynthetic pathway existing in plants. This modification produced a strain in the bacteria which results in the overproduction of a pigment named ‘lycopene’. It is a photoactive pigment which is also present in tomatoes and watermelon and is responsible for their bright red colour. The activated pigment producing cells are then coated with a thin film of TiO2 through a super molecular interface. These cells are used to make the anode of the solar cell. The medium used for the cell to transfer electricity is an iodine based dye. [13][14]
5.2 Type 2
ECONOMY
6.1 Measurement of feasibility
The economic feasibility of any electricity source is the most important factor which decides the level of importance it will be given for future research and development. This is because a very well performing and highly efficient energy source will not be of much use if it costs a major part of a country’s economy to run its systems. The output of an electricity source is generally measured in terms of kilowatt-hour or megawatt-hour. These include the costs of the system setup, subsidies provided by the government, fuel costs and the cost of maintenance of the setup.
The standard used for measuring the feasibility of different energy sources is the Levelized cost of energy (LCOE). It is calculated by dividing the average total cost required to setup and maintain an electricity production unit over its lifetime by the total amount of energy produced by the system over its lifetime.
6.2 Dependence of costs on different factors
As can be seen, the net result is that the solar energy is the cheapest of all, especially once the installation process is complete owing to the fact that it requires little to no maintenance and fuel for its operation.
6.3 Data from studies
Comparison of costs for different energy sources is done every few years by organisations such as Lazard, Bloomberg and IRENA. The latest November 2018 data from Lazard shows that renewable energy sources have now become cheaper than the traditional fossil fuels. Energy generated through wind energy farms was calculated to cost $29/MWh while the cost of solar energy production units was $36/MWh. This was lesser than or equal to the costs of fossil fuel using systems which was $36/MWh. This is because of the decrease in the costs through advancement in technology. The price of solar energy systems has fallen by 17% while wind systems have fallen by 7% from the last year. Also, provided the government gives subsidies to promote this renewable source of energy, the costs of solar systems were as low as $32/MWH and that for wind was $14/MWh. [9]
ENVIRONMENTAL FACTOR
7.1 Benefits
Cost: Once installed successfully, solar panels are very low maintenance setups. Whether in the form of large fields of solar panels, or the more distributed private roof top panels, they last long and only require occasional cleaning. The significant initial investment can be further reduced by advancement in technology for setting up the structures. Also, subsidies and government help initiatives make it affordable for private households thereby significantly reducing the dependence on traditional electricity sources. As such, the costs of setting up a system has halved in the past three years.
Safety and human health: The solar energy installations are completely safe to be present in human societies unlike any other energy production installations. There is no risk of radiations, toxic gas emissions or loud noise production.
7.2 Disadvantages
Hazardous materials during manufacture: The solar cell panels are made of semiconductor material, after a rigorous process of mining, purification, extraction and manufacture. All these process involves use of a number of chemicals depending upon the type of solar cell to be manufactured. These processes naturally produce a lot of hazardous waste as well as toxic emissions from the industries. Dumping of the by-products in the environment and improper recycling of the chemicals used for manufacturing affects the nearby locality and may even spread in large areas. Even with proper landfilling methods, the area maybe be rendered useless for agriculture, or even for residential purposes.
Carbon emission during manufacture: After installation, the solar cells produce almost zero carbon emission because there is no by-product. However, during other processes of the lifecycle of the solar cell, carbon is emitted in the environment. This is mainly during the mining process for its raw components such as silica and from industries which manufacture the parts for the solar energy setups. Most studies average the carbon emission to be 0.08 to 0.2 pounds CO2 per kilowatt-hour of energy produced. However, this is much lower than natural gas (which is 0.6-2 pounds/kWh) and the non-renewable coal (1.4-3.6 pounds/kWh), and as such is the best alternative to replace the non-renewable sources of energy. However, the carbon footprint maybe further minimized through the use of biogenic solar cells instead of the conventional synthetic photovoltaic cells since the former uses only few parts to be manufactured industriously while most of the components are organic in nature. Also, the raw materials used are non-hazardous and can be recycled easily to form new systems.