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Energy sources

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الكلية كلية الهندسة/المسيب     القسم هندسة الطاقة     المرحلة 2
أستاذ المادة واثق ناصر حسين الشمري       01/05/2017 17:36:29
References
1-Steam plant operation by Everett B. Woodruf et al
2-HANDBOOK OF ENERGY ENGINEERING by Albert Thumann et al
Energy
Energy is the capacity to do work. Energy comes in various forms, such as motion, heat, light, electrical, chemical, nuclear energy, and gravitational. Total energy is the sum of all forms of the energy a system possesses. The classification
of energy into different ‘‘types’’ often follows the boundaries of the fields of study in the natural sciences. For example, chemical energy is the kind of potential energy stored in chemical bonds, and nuclear energy is the energy stored in interactions between the particles in the atomic nucleus. Microscopic forms of energy are related to the molecular structure of a system and they are independent
of outside reference frames.
Hydrogen represents a store of potential energy that can be released by fusion of hydrogen in the Sun. Some of the fusion energy is then transformed into sunlight, which may again be stored as gravitational potential energy after it strikes the earth. For example, water evaporates from the oceans, may be deposited on elevated parts of the earth, and after being released at a hydroelectric dam, it can drive turbines to produce energy in the form of electricity. Atmospheric phenomena like wind, rain, snow, and hurricanes, are all a result of energy transformations brought about by solar energy on the atmosphere of the earth. Sunlight is also captured by plants as chemical potential energy in photosynthesis, when carbon dioxide and water are converted into carbohydrates, lipids, and proteins. This chemical potential energy is responsible for growth and development of a biological cell.
In order for an energy resource to be reliable, it must, first of all, deliver the service that the consumer expects. Secondly, it must be available in the quantity desired, when
the consumer wishes to consume it (whether this is electricity from a wall outlet or gasoline dispensed from a filling station). Lastly, the resource must be available at a
price that is economically affordable


The basic unit of energy in the metric system is the joule (J), which is equivalent to the exertion of 1 N of force over a distance of 1 m. Thus
1 J = 1 N•m
The basic unit of power, or flow of energy per unit of time, is the watt (W), which is equivalent to the flow of 1 J of energy per second. Therefore
1 W = 1 J/s
A convenient alternative measure of energy is the flow of 1 W for an hour, which is denoted 1 watthour (Wh). A commonly used measure of electrical energy is the
kilowatthour, which is abbreviated kWh and consists of 1000 Wh. Since both joules and watthours are units of energy, it is helpful to be able to convert easily between the two. The conversion from watthours to joules is calculated as follows:

The quantity of energy in an electrical current is a function of the current flowing, measured in amperes (A), and the change in potential, measured in volts (V). The transmission of 1 W of electricity is equivalent to 1 A of current flowing over a change in potential of 1 V, so
1 W = 1 VA

The unit voltampere (VA) may be used in place of watts to measure electrical power.

Example 1-1. A portable electric generator that is powered by diesel fuel produces 7 kWh of electricity during a single period of operation. (A) What is the equivalent amount of energy measured in MJ? (B) Suppose the fuel consumed had an energy content of 110 MJ. If the device were 100% efficient, how much electricity would it produce?

Solution
(A) 7 kWh × 3.6 MJ/kWh = 25.2 MJ
(B) 110 MJ/3.6 MJ/kWh = 30.6 kWh


Table 2.1 Some energy units and definitions


Figure 1.4 shows the energy consumption


While figure 1.5 shows the energy consumption for selected countries

Sources of energy

Conventional sources of energy are those that have been well-established and form a significant portion of world energy production. Alternative sources are those that have been proposed but are not yet significant producers. Renewable forms of energy are those that are or can be replenished through naturally-occurring processes. Sustainability is another way of looking at the energy usage and depletion problem. Resilience is a term that is also being used in this area to refer to the time-response with respect to an external man-made or natural disturbance.
Or can be categorized such as
1.primary energy
Primary energy is the energy extracted or captured directly from the environment.
Three distinctive groups of primary energy are:
• Nonrenewable energy (fossil fuels): coal, crude oil, natural gas, nuclear fuel.
• Renewable energy: hydropower, biomass, solar energy, wind, geothermal, and
ocean energy.
• Waste.
Primary sources of energy consisting of petroleum, coal, and natural gas amount to about 85% of the fossil fuels in primary energy consumption in the world [13, 37].
Projected energy use in the world shows that petroleum, coal, and natural gas will still be the dominant energy sources by 2035 (Fig. 2.2). The principle of supply
and demand suggests that as fossil fuels diminish, their prices will rise and renewable energy supplies, particularly biomass, solar, and wind resources, will become sufficiently economical to exploit [13, 37]. Figure 2.3 shows the primary energy flow in the US. The energy content may be converted to ton of oil equivalent (TOE): 1
TOE = 11630 kWh = 41870 MJ.
2. Secondary Energy
The primary energy is transformed to secondary energy in the form of electrical energy or fuel, such as gasoline, fuel oil, methanol, ethanol, and hydrogen [3]. The primary energy of renewable energy sources, such as sun, wind, biomass, geothermal energy, and flowing water is usually equated with either electrical or thermal energy produced from them. Final energy is often electrical energy and fuel, which is referred to as useful energy. The selected four types of final energy are electrical, thermal, mechanical, and chemical energy. These types of final
energy set a boundary between the energy production and the consumption sectors
[7, 14, 33].



المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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