Mechanical engineering should focus on construction and maintenance of the alternative forms of generating electrical power.
Consideration of precisely why mechanical engineering out to focus on the construction and maintenance of alternative forms of generating electrical power demands the discussion and careful examination of the various alternatives available in producing electrical power. What is clear is that caring for the environment has become one of the most crucial subjects of our everyday life in the past few years. All the papers, bottles, and waste, and we purchase more eco-friendly vehicles, but not many know the amount of electrical energy we consume and the amount of pollution we cause the environment.
A single UK citizen uses about 6000 kWh annually. The costs of electricity is up to five times as much as natural gas in the UK. This is why we should be considering the use of gas as a primary source of heating and electrical energy. Nowadays, electrical energy is produced in a highly centralized way. This means that, in Germany, there are only a handful of power plants that produce energy. This mode of centralisation presupposes that energy needs to be transmitted for thousands of kilometer. In this process, about 3-7% of energy is wasted. To make matters worse, these power plants are run all year long and this results in the production of at least 50-70% of nominal exhaust heat (Reiner 1996, p 12.). One way to make the distribution and transmission more clean and economical is to transfer the source of the electrical energy so that it is nearer the consumer and to utilize natural gas or biogas as the main source of energy. Biogas has been proven to be environment friendly when used as fuel cells.
This essay will examine alternative methods of energy production such as the Sterling Engine, the Gas Turbine + Steam Engine, Fuel Cell + Micro Gas Turbine. It is beyond the scope of this essay to examine every alternative energy method available and hence the most exciting methods have been studied in this essay.
Most of the systems found today can reacquire wasted exhaust heat. As stated in the last paragraphs, this is achieved through the use of heat exchangers, boilers, or recuperators. These methods have been utilized for several years and their effectiveness is already renowned. Another option is the use of a Sterling engine. This engine is made of a piston and a cylinder, similar to a combustion engine (Williams and Larson 1996, p. 152). Air or hydrogen fills the cylinder and, when the cylinder is externally heated, the temperature rises, the gas increases, and this drives the piston. Then, through a gas cooling system, the engine achieves a continually reciprocating movement. The latest concept is to incorporate a mix of a Sterling engine and a microturbine. Since the temperature of the microturbine waste exhaust is about 500 degrees Celsius, the Sterling engine can draw its energy from it. A benefit in using this system is that the total effectiveness is made dramatically higher than that of a single gas turbine. The Sterling engine’s efficiency for electrical energy increases to 31%, while that of the engine’s is about 10% (Axelsson, Harvey, Asblad, and Berntsson 2003, p. 32). Another significant benefit is that the Sterling engine almost does not produce any pollution. With the use of a regenerator, the effectiveness of the Sterling cycle reaches an ideal level and results to a more advantageous fuel economy than the current IC engines. Additionally, the engine is also quiet and simple. (Axelsson, Harvey, Asblad, and Berntsson 2003, p. 42)
Gas Turbine + Steam Engine
This concept is founded on one system utilizing two turbines. The idea behind a gas turbine has been set out above. In this method, the waste exhaust from the gas turbine can be utilized to heat the water and, thus, gives out steam. This steam can be applied to move the blades of the steam turbine. The system’s efficiency is increased to 55%. Plus, the heated steam produced by the steam turbine can be utilized in a central heating system for homes, and this raises the efficiency to 85% (Wildi 2000, p. 32).
Fuel Cell + Micro Gas Turbine
This system is a hybrid made up of a mix of two technologies—a microturbine powered by gas and a solid oxide fuel cell. Since this is a new technology, there is not much to be said about the efficiency of the entire system, but the system operators believe that this technology can achieve up to 70% electrical efficiency. However, there are two significant disadvantages to the utilization of these cells. First, the cost of production of this fuel cell, and maintenance, is significantly more than that of a gas turbine or combustion engine. Second is the huge size and high weight of the fuel cells (Soares 2007, p 221). The concept behind this system is based on a solid oxide fuel cell driven by natural gas, with the heated waste exhaust gasses applied to drive a microturbine. The producers of this technology state that “producing an efficiency of around 53%, believed to be a world record for the operation of a fuel cell using natural gas.” With some improvements, the efficiency of this system can achieve up to 60% for diminutive systems and more than 70% for bigger systems (Ho, Chua, Chou 2004, p. 1125).
Microturbines mixed with gas is arguably one of the best alternative energy production methods. Cleanness and low prices are achieved with gas while microturbines guarantee high system efficiency. Existing solutions include turbines that produce over 30kW or a turbine with a lower power output, at 3-5kW. Currently, there are zero manufacturers that produce a turbine with a low power output of 3-5kW as a source of energy, while several advantages can be seen with the use of microturbines instead of a combustion engine, such as lesser maintenance, lesser vibrations, cleaner exhaust gasses, and a lighter weight (Hwang 2004, p. 820). Unfortunately, there are a couple of glitches to be solved: the high cost of production and the design of an efficient high speed generator. The mechanical engineering turbines manufactured today use ceramic technology that allows electrical efficiency of up to 40% (Hwang 820). This means that the efficiency of microturbines is lesser compared to larger, more traditional plants while the costs of operation and the total pollution produced is dramatically more superior. The makers of microturbines attempt to avoid talking about the efficiency of their microturbines; however, they choose to show the total efficiency achieving up to 50-70% when applied in a CHP. The savings that can be achieved currently by utilizing microturbines are not significant. Lastly, gas turbines offer the greatest efficiency and the least emissions of all the combustion power generation technology that is currently offered.
Decher, R. 1996. Direct Energy Conversion: Fundamentals of Electric Power Production. Oxford University Press.
Williams R, Larson E. 1996. Biomass Gasifier Gas Turbine Power Generating Technology, Biomass and Bioenergy Vol. 10. No. 2-3, 1996, pp. 149-166.
Axelsson H, Harvey S, Asblad A, Berntsson T,. 2003. Potential for greenhouse gas reduction in industry through increased heat recovery and/or integration of combined heat and power, Applied Thermal Engineering, 23 (1), pp. 65-87.
Wildi, T. 2000. Electrical Machines, Drives, and Power Systems, 4th ed. Englewood Cliffs, N.J.: Prentice-Hall.
Soares, C. 2007, Microturbines Application for Distributed Energy System, Oxford: Elsevier.
Ho J. C., Chua K. J, and Chou S.K, 2004, Performance study of a Microturbine system for cogeneration application, Renewable Energy, 29 (7), pp. 1121-1133.
Hwang Y,. 2004, Potential energy benefits of integrated refrigeration system with microturbine and absorption chiller, International Journal of Refrigeration, 27 (8), pp. 816-829.