Integration of Renewable Energy Sources with Smart Grid. Группа авторов

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Figure 1.9 Proton exchange membrane (PEM) fuel cell.

      1.1.3.3 Alkaline Fuel Cell

      AFCs were the widely used fuel cells in space industry. Alkaline fuel cell is also called as “Bacon fuel cell” as it was invented by Francis Thomas Bacon. It is one of the considered fuel cell design. It is similar to PEM fuel cell except for the use of alkaline membrane instead of acid membrane. It uses a solution of potassium hydroxide in water as the electrolyte and non-precious metal as a catalyst at the anode and cathode. It uses hydrogen as fuel and pure oxygen to produce water and electricity. Because of its efficiency greater than 60%, it is used in space industries.

      1.1.3.4 Phosphoric Acid Fuel Cell

      It was the first commercial fuel cell in the mid-1960s. PAFC uses phosphoric acid as an electrolyte. The electrolyte is a pure or concentrated liquid phosphoric acid (H₃PO₄) in a silicon carbide matrix. It operates in the temperature range between 150°C and 210°C. Electrodes are made of carbon paper coated with platinum catalyst. It is used in buses and in stationary power generators in the range of 100 to 400 kW.

      1.1.3.5 Molten Carbonate Fuel Cell

      The conventional source–based power plants use MCFC for industrial and military applications. The electrolyte used in MCFC is a molten carbonate salt mixture immersed in ceramic matrix of beta alumina solid electrolyte. Because of its high operating temperature, metals are used as catalyst at the anode and cathode. It offers better efficiency when compared to PAFC which is around 65%. PAFC’s efficiency is only 30% to 40%.

      Solid oxide fuel cell (SOFC) and reversible fuel cells are the other types of fuel cell that are generally employed for various applications.

       1.1.4 Biomass Energy

The energy derived from the organic matter of the living organism is the biomass. It is a RES that produces electricity with minimum cost. The organic material produced from plants and animals, crops and algae are used in biomass energy production. The global cumulative biomass energy generation is shown in Figure 1.10. When biomass is burned, heat is generated and the thermal energy is converted into electrical energy. This biomass can either be burned directly or converted into liquid biofuels or biogas. The conversion methods for biomass energy production include chemical, thermal, and bio-chemical [9].

Figure 1.10 Cumulative bioenergy generation.

      Initially, direct combustion method was employed with wood as a fuel to produce energy. In the recent times, chemical treatments such as pyrolysis, fermentation, and anaerobic processes are implemented to convert these sources into a usable form such as ethanol. During pyrolysis treatment, coal is obtained as a product that strengthens the matter by burning it in the absence of oxygen.

      The sources of biomass energy generation include the following:

      1.1.4.1 Energy Production From Biomass

      Solid biomass, such as wood and garbage, can be burned directly to produce heat. Biomass can also be converted into a gas called biogas or into liquid biofuels such as ethanol and biodiesel. These fuels can then be burned for energy production.

Biogas is formed when paper, food scraps, and yard waste are decomposed in landfills; it can also be produced by processing sewage and animal manure in special vessels called digesters. Ethanol is extracted from crops such as corn and sugar-cane by fermentation process. Biodiesel is produced from vegetable oils and animal fats and can be used in vehicles and as heating oil.

      The current availability of biomass in India is estimated at about 500 million metric tonnes per year [10]. Studies from the Ministry has estimated surplus biomass availability of about 120–150 million metric tonnes per annum covering agricultural and forestry residues corresponding to a potential of about 18,000 MW. Apart from this, it is predicted that about 7,000-MW additional power could be generated through co-generation process.

       1.1.5 Hydro-Electric Energy

      As water is a never depleted source and the pressure of water is used to generate energy, hydro-electric power plants gained its significance in renewable energy industry. The energy of flowing water is converted into mechanical energy using a turbine and the coupled generator produced electricity from the mechanical energy.

Figure 1.11 shows hydro-electric power plant. The generator generates electricity by converting the input mechanical energy produced from the energy of water flow. Whenever a magnet moves past a conductor, it causes electricity and the flow of current exists. In a large generator, the electromagnets are made by circulating direct current through wire loops which is wound on steel laminations. These are called as poles, which are held on the outer surface of the rotor. The rotor rotates at a fixed speed as it is connected to the turbine shaft. As the rotor rotates, it cuts the flux produced and induces an emf, and thus, a potential is developed across the generator output.