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Thursday, 20 December 2012 00:00
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Unilorin don champions course on energy conversion

OlorunmaiyeEngineering is the profession in which knowledge of mathematics and natural science is applied with judgment and responsibility to invent, design, construct, operate and maintain machines, structures and systems utilizing the materials and forces of nature economically for the benefit of mankind.

Mechanical Engineering is the branch of engineering concern with the generation, transmission and utilization of heat and mechanical power, and with the production and operation of tools, machinery, and their products. Mechanical Engineers have the following areas of interest.

Energy conversion from natural sources to other useful forms of energy;
Designing and producing machines to make human work easier;
Processing of raw materials to obtain useful products; and
Relationship between technology & society.

Energy is the capacity forms of a body or a system to do work. The different forms of energy can be divided into six groups as shown in Table 1. The transitional and stored electrical forms of energy are considered high grade energy because they can be converted to thermal energy efficiently grade energy because its conversion to other forms of energy is limited by the second law of thermodynamics. Mechanical Engineers are particularly concerned with generation, transmission, utilization and conversion of thermal energy.

The changing of energy from one form to another is behind everything that happens around us. Man has fulfilled the mandate to subdue the earth given by God in Genesis 1:28 by inventing many devices for transforming energy from one form to another – energy conversion systems. What man has able to do with energy conversion is captured in the lyrics of a gospel song by B.J. Thomas.

Man hands
And his plans
Have made this land
What it is today
We’ve built sky high
Shiny towers
And fill our earth
With highways
Moving mountains
Not with faith
But with machines
And we’ll always
Be looking for ways
To fulfill our
Earthly dreams

Energy consumption involves degradation of energy ultimately to thermal energy in the ambient air. In the history of man, advances in civilization have usually been accompanied by increase in the rates of energy consumption. Energy consumption by the early man was estimated to be 8 – 11 KJ per capital daily. During the period of primitive agriculture society, the rate of energy consumption rose to 50,000 KJ per capital per day.

Between 1850 and 1870, at the peak of industrial revolution, energy consumption per capital per day was about 290,000 JK in Western Europe and USA. Nowadays, in developed countries, the rate of energy consumption is between 900,000 – 110,000 KJ per capital per day.

Man as a power source is weak and inefficient. Unlike conventional engines which can give constant power output, the power output for human beings tend to decrease with time.
The relationship between rate of doing work, metabolic rate an heat exchange between man and his environment in which he is doing work is given by the equation:    M – W = Q + S
Where     M = metabolic rate i.e. rate at which the body is producing energy
W = rate of doing work
Q = rate of heat loss from man’s body by convection, radiation and evaporative heat losses
S = rate of heat storage in man’s body which is either positive or negative
For condition of equilibrium, S = 0 and rate of heat loss from the body
Q=M-W=M(l- η)
Where η = thermal efficiency which has a maximum value of about 20% according to Arora.

The carbohydrates, fats and proteins in food consumed by man are oxidized in the body to release chemical energy. Lijedahl et al reported that human beings are limited to less than 0.1 KW for continuous power output. Thus man operates better as a controller of power rather than as a power source and hence the need for man to device energy conversion systems.

Figure 2 shows the block diagram of a generalized energy conversion system. The input depends on the type of energy conversion system being used. For example it may be fossil fuel or bio fuel or a mixture of the two. It may also be some other forms of renewable energy source like wind or solar radiation.

Fossil Fuel,
Renewable
Energy input,
Electrical
Energy,
Nuclear Fuel
Propulsion energy
Energy
conversion
Electrical power
Other forms of
Mechanical Energy
Electromagnetic
Chemical Energy
Thermal Energy

FIGURE 2: BLOCK DIAGRAM OF THE GENERALIZED ENERGY CONVERSION SYSTEM
The output from the energy conversion process or processes may be one more of the possible different types of output indicated in figure 2. The energy conversion process or several conversion processes from one energy form to several other forms in succession.
Energy usage in a nation is commonly broken down into the following five categories:
Electrical energy generation;
Residential usage;
Commercial usage;
Industrial usage;
Transportation.

Although electrical energy generation is put in a separate category, it is not an end use of energy since most of it goes into residential, commercial and industrial usage and a little into transportation.

A country attains economic development when there is enormous subsidy of human enterprise of the population can produce, process and distribute the food they need, thereby allowing the greater percentage of the population to produce goods and services in the other sector of the economy

The Problem of Electric Power Supply in Nigeria
Among the various forms of energy, electricity is the most preferred because of its cleanliness when being converted to other energy forms, unlimited degree of divisibility and the convenience of transporting it from one place to another using cable.

Nigeria with a current estimated population of 167 million and a total installed electricity generation capacity of 8815 MW in 2010 according to CBN annual report, was only able to generate 4,000 MW in September 2011 according to Nnaji. This is grossly inadequate and the effort made to raise it to 6,000 MW has not been successful.

Even then a lot of this energy is wasted, for example, by leaving lights on during the day where they are not necessary, leaving lights on in unoccupied rooms at night, using inefficient incandescent light bulbs instead of compact florescent lamps (CFLs) or light emitting diode efficient. It is the practice in developed countries to design buildings to use minimum amount of energy for example using daylight rather than artificial light in spaces in the building where possible.

• To be continued

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