Environment & Energy Introduction Valentim M B Nunes Unidade Departamental de Engenharias Instituto Politécnico de Tomar, February, 2015.

Environment & Energy

IntroductionValentim M B Nunes

Unidade Departamental de Engenharias

Instituto Politécnico de Tomar, February, 2015

Objectives

The Curricular Unit aims the acquisition of skills in the following areas: Understanding energy-environment relations from a sustainability point of view; Analysis of the main energy production, storage and conversion systems; Development of technical and economic analysis capacities of the most common energy systems.

Program

•Introduction. The use of energy in modern societies and environmental impact. Energy resources: primary, secondary, and final. Energy and the environment: greenhouse effect, ozone layer and acid rain. Global energy statistics and situation in Portugal.•Energy conversion systems. Thermodynamic principles. Different forms of energy. First and Second laws of thermodynamics. Thermal cycles: Carnot cycle, Rankine, Brayton Joule, Otto and Diesel. •Nuclear Energy. Radioactivity. Effects of radiation. Nuclear Reactors. Management of wastes. The nuclear fusion.• Storage and transmission of energy. Electromechanical transformation of power. Transmission of energy. AC/DC Converters. Properties of energy storage systems.•Renewable energies. Wind energy. Hydropower and mini-hydropower systems. Solar thermal and photovoltaic systems. Geothermal and ocean energy. Brief reference to sources of biomass.•Bioenergy. Fuel production from biomass. Biogas, bioethanol and biodiesel. Environmental aspects.

Energy, Civilization and the EnvironmentModern societies are characterized by a substantial consumption of fossil and nuclear fuels required for the functioning of infrastructures which these societies depend on: food production and drinking water, clothing, housing, transportation, communications, and other goods and services essential to human activity.

The amount of energy used and the concentration of their use in urban areas, have caused environmental impacts, such as the deterioration in the quality of water, air, and local and regional-scale ecosystems, as well as adverse effects on the health of human populations.

Fay, J., Golomb, D.S., Energy and the Environment, Oxford University Press and Open University, Oxford, UK, 2004

But…..

Our life depends on the production, conversion, transport and storage of energy!!

Energy resources: primary, secondary and Final

The primary energy source, also known as natural energy source, is a source of energy that exist in natural form in nature and can generate energy directly, these include coal, oil and natural gas, hydropower, solar and wind power, biomass, geothermal and ocean. Energy sources can be classified into renewable and non-renewable. Renewable energy sources are an infinite generator source even if they are used by man, possessing the ability to regenerate naturally. For example solar energy, hydro and wind power, biomass, geothermal and ocean. As non-renewable energy sources, such as petrochemical and nuclear fuel, are formed underground from remains of animals and plants that took millions of years to turn into fuel. These cannot be quickly recovered and their quantities become increasingly reduced resulting from their consumption in human activities.Secondary energy sources are transformed from primary energy sources, such as electricity, gasoline, diesel, coal tar, steam, among others.

Final energy refers to the energy as it is received by the user in the different sectors, whether in the primary or secondary form.

Fundamental concepts

One of the fundamental laws of nature is the principle of conservation of energy. During an interaction energy can change form, but the total amount remains constant, i.e. the energy cannot be created or destroyed.

In Newtonian mechanics:

constante PEKEE

Notes about units and dimensions

Any physical quantity can be characterized by dimensions. Certain basic dimensions as the mass, m, the length, L, the time, t and temperature, T, are primary or fundamental dimensions. Others, such as the speed, v, energy, E, or the volume, V, are secondary units.

There are various systems of units. There are two many common systems in practice: the system USCS (United States Customary System) and the SI (International System). The SI is a simple and logical system based on decimal ratio between the various units and is used in scientific and engineering work in most industrialized nations. The United States are the only industrialized nation not yet fully converted to SI!

In 1960 the CGPM (General Conference on weights and measures) produced the SI based on six fundamental quantities (metro, m, kilogram, kg, second, s, ampere, A, kelvin, K, and candela, cd) to which was added in 1971 the mole, mol. Even in the United States, the industry involved in international trade and engineering students are adopting SI.

Dimension Unit

Length meter (m)

Mass kilogram (kg)

Time second (s)

Temperature kelvin (K)

Electric current ampere (A)

Luminosity candela (cd)

Quant of matter mole (mol)

Multiple Prefix

1012 tera, T

109 giga, G

106 mega, M

103 quilo, kg

102 hecto, h

101 deca, da

10-1 deci, d

10-2 centi, c

10-3 mili, m

10-6 micro, µ

10-9 nano, n

10-12 pico, p

International System

1 tep = 107 kcal = 4,18 ×1010 J

Force, energy and powerThe force its a secondary dimension whose unit is derived from Newton's second law:

maF In the SI the unit of force is the newton (N)

2mskg 1 N 1

The work, is a form of energy, that can be difined as force x distance, having units of N.m that we call the joule (J)

m N 1 J 1

In the english system the unit of energy is the Btu (British Thermal Unit)

kJ 1.055 Btu 1

Other equivalencies:

PowerThe work done by unit of time is called power and it is defined by:

dt

dEP

The SI unit for power is the Watt, W.

There are other units fo power. For instance: CV, hp, erg/s, Btu/h, Cal/h……

J/s 1 W 1

For the purposes of energy accounting is necessary to convert to the same unit the consumption or production of all forms of energy. The unit usually used for this purpose is the ton oil equivalent which, as the name implies, is the energy content of one tone of oil undifferentiated.

The unit of the International System is the Joule (J). The relation between the two units is: 1 tep = 41.86 x109 J

In the case of electrical energy, the energy is usually accounted in "kilowatt hour" (kWh); the relation between the two units is:

1 tep = 11 628 kWh

Tep: ton of oil equivalent

BibliographyY. Cengel, M. Boles, Termodinâmica, 3ª ed., McGraw Hill, Lisboa, 2001

Fay, J., Golomb, D.S., Energy and the Environment, Oxford University Press and Open University, Oxford, UK, 2004