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Unit 6 : Sources of Energy in the World

  • Unit 6 : Sources of Energy in the World

    Key unit Competence

    Evaluate the energy sources in the world

    My goals

    By the end of this unit, I will be able: 
    * identify sources of energy in Rwanda.

    * outline the basic features of renewable and non renewable energy 
    sources.

    * evaluate energy uses and availability in Rwanda.

    * identify various advantages and disadvantages of various energy 
    sources.

    * be aware of the moral and ethical uses associated with use of energy.

    Introductory activity 
    At hospital, during patient treatment, doctors recommend to patients to take 
    a balanced diet. That is true because as a patient takes medicines and eat 

    very well, it yields a quick recovery and one gets strong.

    Questions:
    1.What do you think is contained in food that we eat?

    2.Discuss why it is very important to take a sunbath when a person is sick?

    3.Discuss other different sources of energy in environment?

    Introduction

    Origins of the power used for transportation, for heat and light in dwelling 
    and working areas, and for the manufacture of goods of all kinds, among other 
    applications. The development of science and civilization is closely linked 
    to the availability of energy in useful forms. Modern society consumes vast 
    amounts of energy in all forms: light, heat, electrical, mechanical, chemical, 
    and nuclear. The rate at which energy is produced or consumed is called power, 
    although this term is sometimes used in common speech synonymously with 
    energy.

    Activity 1
    Answer these questions.
    a) What do you think when you hear the word “energy”? Give 
    its definition and that of the term “energy source”.
    b) Among scientists and energy professionals, a standard list 
    of current energy sources would include: biomass (plant 
    matter), nuclear, coal, oil, geothermal, solar, hydro (rivers), 
    wave or tidal, natural gas, wind. Add other sources of 
    energy which you may know.
    c) From the list given in (b) what is the major category of 
    renewable energy? 
    d) d) Between renewable and non-renewable energy which 
    one produces a little or no pollution or hazardous waste and 
    pose few risks to public safety? How the other produces it? 
    e) e) Discuss in groups this consequence above.
    f) f) List as many as you can uses of renewable energy 

    sources.

    Read carefully these key terms in the table below then give answers to related 

    questions.

    Key Terms 

    Biomass energy Energy released from plants (wood, corn, etc) 

                                      through combustion or other chemical process 

    Fossil fuel  A non-renewable energy resource that began to 
                            form millions of years ago from the remains of 
                            once living plants and animals. Its current forms 

                           include petroleum, coal and natural gas. 

    Geothermal energy Heat energy from the earth.

    Hydropower Transformation of the energy stored in a depth of 

                                water into electricity.

    Non renewable energy 
    Resources, such as fossil fuels that cannot be 

    replaced by natural processes at the same rate it is consumed.

    Photovoltaic A chemical process that releases electrons from a 
                                semi-conductor material in the presence of sunlight 

                               to generate electricity.

    Renewable energy Resources, such as wind and water that can be 
                                             recycled or replaced at a rate faster than they are 

                                            consumed.

    Solar Energy Energy from the sun; often captured directly 
                                 as heat or as electricity through a photovoltaic 

                                 process. 

    Uranium An element that releases heat as it undergoes 
                        radioactive decay.

    Wind energy Energy transferred with the motion of air in the 
                                lower atmosphere that arises from differential 
                                heating of the earth. The energy in the wind can be 
                                extracted as mechanical energy to do work such as 
                                grind grains (a wind mill) or generate electricity 

                               (wind turbine). 

    Wave energy Wave power captures the energy of ocean surface 
                                waves, and tidal power. Converting the energy 
                                of tides, are two forms of hydropower with 
                               future potential; however, they are not yet widely 

                               employed commercially. 

    Worldwide, wood is the largest source of biomass for non-food energy, but 
    other sources are also used, including municipal wastes and crop wastes. 
    Crops such as sugar cane are used to make alcohol for transportation fuel. 
    In many developing countries, wood is the most important energy source. 
    Global resources of geothermal energy (the heat contained below Earth’s 
    surface) are so immense that they are usually considered to be renewable. 
    But this classification is not strictly correct, since the heat stored in any given 
    volume of rock or underground water is depletable. In addition, the most 
    easily accessed geothermal resources, natural hot springs and geysers, will 
    not last for more than a few decades if exploited for energy on a large scale. 
    Estimates vary widely as to how long fossil fuels, oil, coal, and natural gas 
    will last. These estimates depend on assumptions about how much fossil fuel 
    remains in the ground, how fast it will be used, and how much money and 
    effort will be spent to recover it. However, most estimates agree that, if present 
    rates of consumption continue, proven oil and natural gas reserves will run 
    out in this century, while coal reserves will last more than 200 years. Once 

    they are used, these energy sources cannot be replaced.

    Fossil fuel

    Fossil fuels are fuels formed by natural processes such as anaerobic 
    decomposition of buried dead organisms. The age of the organisms and their 
    resulting fossil fuels is typically millions of years, and sometimes exceeds 
    650 million years. Fossil fuels contain high percentages of carbon and include 

    coal, petroleum and natural gas. 

    C

    C

    Rwanda’s main fossil fuel resource is methane gas. It is estimated that there 
    are 50 billion cubic metres of exploitable methane, which is the equivalent 
    of 40 million tons of petrol (TOE) laying at the bottom of the Lake Kivu 
    under 250 metres of water. Of the 55 billion cubic metres (cum) Standard 
    Temperature and Pressure, STP) of methane gas reserves, 39 billion cum 
    (STP) are potentially extractable. This represents a market value of USD 16 
    billion, equivalent to 31 million Ton Oil Equivalent (TOE). The technical and 
    economic feasibility of methane gas exploitation has been clearly demonstrated 
    since 1963 by the small methane extraction pilot unit at Cape Rubona with a 
    capacity of 5000 cum of methane per day at 80 % purity. The resource is 
    estimated to be sufficient to generate 700 mW of electricity for 55 years with 

    Rwanda’s share being 350 mW.

    C

    Nuclear fuel

    Nuclear fuel is a material that can be ‘burned’ by nuclear fission or fusion to 

    derive nuclear energy. 

    C

    Most nuclear fuels contain heavy fissile elements that are capable of nuclear 
    fission. When these fuels are struck by neutrons, they are in turn capable of 
    emitting neutrons when they break apart. This makes possible a self-sustaining 
    chain reaction that releases energy with a controlled rate in a nuclear reactor or 

    with a very rapid uncontrolled rate in a nuclear weapon.

    “…Rwanda should choose a path to renewable energy—although nuclear is 
    the best other alternative; Rwanda does not have the technology to generate 

    nuclear energy.

    Even if Rwanda was ready to develop it despite the international laws and 
    regulations, nuclear energy poses a great danger especially, Rwanda being 
    located in a volcanic region. Nuclear energy for Rwanda in my opinion is a no 

    go option”. New times May 21, 2015

    Renewable sources

    Renewable energy is generally defined as energy that comes from resourcesthat 
    are not significantly depleted by their use, such as sunlight, wind, rain, 
    tides, waves and geothermal heat. Renewable energy is gradually replacing 
    conventional fuels in four distinct areas: electricity generation, hot water/

    space heating, motor fuels, and rural (off-grid) energy services.

    C

    Generally, Rwanda is well endowed with renewable energy resources, but most 
    potential still remains untapped. Micro hydro-power in particular constitutes 
    a significant potential for rural power supply with many areas having ample 
    rainfall and most streams and rivers unexploited. Solar irradiation is high - 
    between 4-6 kWh/m2/day - but diffusion is hampered by high initial cost and 
    limitations on high load usage. Biogas is promising for thermal energy needs 
    for farms and small institutions, especially considering the large number of 

    households that own cows and other livestock.

    Geothermal
    Geothermal energy is from thermal energy generated and stored in the Earth. 

    Thermal energy is the energy that determines the temperature of matter. 

    C

    According to a study by Geothermal Energy Association, geothermal potential 
    in Rwanda ranges from 170 - 340 MW. In Rwanda geothermal is a main
    energy policy priority and forms a significant part of the 7-year electricity 
    development strategy including a very ambitious action plan targeting 150 
    MW of generation capacity by 2017 (which represents up to 50% of total 
    generation). A Geothermal Act and a geothermal exploration and development 
    paper have been drafted although a proposal for a feed-in-tariff for geothermal 
    still needs to be developed. Three sites (Rubavu, Karongi and Rusizi) were 
    identified already in the 1980’s with resource temperatures in excess of 150°C 
    which could be suitable for geothermal power generation. In early 2012, test 
    drilling commenced to explore possibilities to harness energy in Rubavu, 
    Karisimbi, Kinigi located in western region as well as Bugarama in southern 
    region. The Government has self-financed and contracted the first exploratory 

    drilling in 2013.

    Biomass and biofuels 
    Biomass is biological material derived from living, or recently living 
    organisms. It most often refers to plants or plant-derived materials which 
    are specifically called lignocellulosic biomass. As an energy source, biomass 
    can either be used directly via combustion to produce heat, or indirectly after 
    converting it to various forms of biofuel. Conversion of biomass to biofuel can 
    be achieved by different methods which are broadly classified into: thermal, 

    chemical, and biochemical methods.

    C

    In Rwanda, It has been observed that if an average household used 1.8 tonnes 
    of firewood in a year to satisfy its cooking needs with a traditional stove, the 
    same household would use 3.5 tonnes of wood if it were to switch to charcoal 
    with an improved stove. The use of charcoal in urban areas, in combination 
    with high urban growth rates, therefore is a worrisome phenomenon that 
    accelerates pressure on wood resources. Peat is also a resource the government 
    intends to promote use of. It is estimated that there exists in Rwanda estimated 
    reserves of 155 million tons of dry peat spread over an area of about 50,000
    hectares. About 77% of peat reserves are near Akanyaru and Nyabarongo 
    rivers and the Rwabusoro plains Potential for Peat-to-Power Generation. Peat 
    in the Rwabusoro marshland and around the Akanyaru river can fuel 450 mW 
    of electricity generation for 25 years. Currently, a cement plant and some 

    prisons utilize peat for cooking

    C

    Biogas has been introduced in the country many years ago and Rwanda 
    has gained international recognition for its program in prisons and large 
    institutions. The Government in 2008 announced a policy to introduce biogas 
    digesters in all boarding schools (estimated at around 600 schools), large 
    health centres and institutions with canteens to reduce the consumption of 
    firewood. This process started in 2010 but until today the focus has been 
    mainly on installations for schools. In total, about 50 large biogas digesters 
    have been constructed in institutions in Rwanda and the biogas systems that 
    have been installed in the prisons over the last decade have reduced firewood 

    consumption by up to 40% and improved hygienic conditions.

    C

    Activities in the domestic biogas sector started much later. It is estimated that 
    over 120,000 households have dairy cows that are kept under zero grazing 
    conditions to reduce soil erosion and also due to lack of grazing areas. These 
    numbers are increasing due to the governments programs to increase the 

    number of families with dairy cows.

    C

    Solar energy (photovoltaic cells and solar heating panels)

    Photovoltaic Cells

    Solar energy, radiant light and heat from the sun, is harnessed using a range of 
    ever-evolving technologies such as solar heating, photovoltaic, concentrated 

    solar power, solar architecture and artificial photosynthesis. 

    C

    The Rwandan government is set to commission the first utility-scale solar 
    photovoltaic (PV) plant at eastern Rwanda’s Rwamagana district in August 
    2014 The project, with a production capacity of 8.5 mW, has commenced 
    testing, stated local reports. Dutch company Gigawatt Global is the developer 
    of the project, while Norwegian firm Scatec Solar has agreed to operate and 

    maintain the plant.

    C

    Solar Heating Panels

    A solar thermal collector collects heat by absorbing sunlight. A collector is 
    a device for capturing solar radiation. Solar radiation is energy in the form 
    of electromagnetic radiation from the infrared (long) to the ultraviolet (short) 

    wavelengths. 

    C

    The term “solar collector” commonly refers to solar hot water panels, but may 
    refer to installations such as solar parabolic troughs and solar towers; or basic 

    installations such as solar air heaters.

    Hydroelectric power, wind power and wave power

    Hydroelectricity

    C

    Energy in water can be harnessed and used. Since water is about 800 times 
    denser than air, even a slow flowing stream of water, or moderate sea swell, 
    can yield considerable amounts of energy. Hydroelectricity is the term 
    referring to electricity generated by hydropower; the production of electrical 
    power through the use of the kinetic energy of falling or flowing water. It is 
    the most widely used form of renewable energy, accounting for 16% of global 

    electricity consumption.

    C

    The country currently has about 57 MW installed hydropower generating 
    capacity. Hydroelectric power is mainly from the northern and southern parts 
    of the country (Musanze , Rubavu and Rusizi) namely from the following 
    power plants: Ntaruka, Mukungwa , Rubavu, Gihira as well as Rusizi 1 and 
    Rusizi 2. A number of new sources are supposed to come on line within 
    the coming years adding a capacity of 232 MW by 2013. This includes the 
    hydropower site Nyaborongo with 27.5 MW in Muhanga and Ngororero 
    Districts planned to come on line by February 2013 but currently experiencing 
    delays, and numerous mini/micro hydro plants adding up to 35 MW. The 
    new hydropower plant, Rukarara located in Nyamagabe district, Southern 
    Province, with 9.5 MW and costs of US$ 23.5 million was commissioned in 

    January 2011. Construction for this plant had already started in 2007. 

    Wind Power 

    Airflows can be used to run wind turbines. Modern utility-scale wind turbines 
    range from around 600 kW to 5 MW of rated power, although turbines with 
    rated output of 1.5–3 MW have become the most common for commercial 
    use; the power available from the wind is a function of the cube of the wind 
    speed, so as wind speed increases, power output increases up to the maximum 

    output for the particular turbine.

    C

    Wind Potential in Rwanda has not been fully exploited for power generation 
    although potential wind power that Rwanda has in some areas may provide 
    with possible solutions such as water pumping, windmill and electricity 
    generation. A study of wind speed distribution has been made. (In this study, 
    the results have been found for the average wind speeds and directions for 3 

    stations (Kigali, Rubavu and Huye) from 1985 to 1993.

    These results can be summarised as follows:

    • Direction of wind varies from 11 to 16°.

    • Wind speed varies from 2 to 5.5m/s

    The analysis of the wind energy possible solution for energy supply in rural 
    areas of Rwanda, was undertaken to estimate the wind power potential. In 
    total data from 4 stations (Kamembe, Huye, Nyagatare and Rubavu) have 
    been analysed by the National Meteorological Division in 1989. Once again, 
    the data from 3 synoptic sites (Kigali, Huye and Rubavu) are analysed by the 
    Weibull function. The considered data has been used to evaluate the annual 
    frequency of wind speed and the direction of wind, yearly variation of the 
    monthly average, annual and daily variation, and vertical profile of wind 
    energy potential. Nevertheless more detailed data is still required. In 2010 a 
    wind system was put in place to serve the Rwanda office of information RBA 
    on Mount Jali overlooking Kigali. This is the same site for the 250KW solar 
    system feeding to the grid. There is need for more thorough assessment of the 

    wind potential in the country.

    Wave Power 
    Wave power captures the energy of ocean surface waves, and tidal power, 
    converting the energy of tides, are the two forms of hydropower with future 

    potential; however, they are not yet widely employed commercially. 

    Activity 2

    Energy Source research 

    Purpose

    Although most of the energy consumed in Rwanda comes from fossil fuel 
    sources, there are many other potential sources of energy available. In all 
    cases, there are pros and cons (advantages and disadvantages) to our use of 
    these sources. Some of the energy sources are limited by their availability 
    or environmental impact; others need technological improvements before 
    they can become widely used. For scientists and engineers, research is the 

    best way to learn about unknown topics. 

    In this section, we will examine information about energy sources and 
    how those sources are used to produce electrical energy. We can use this 
    information to help us understand the various pros and cons that affect 
    our use of different energy sources. In this activity, each group of students 
    will begin to become an expert on one aspect of each source of energy and 

    report their findings back to the class. 

    Procedure 
    1. Break into a group of 2-3 learners. 
    2. Choose or accept an assignment to research one particular question 
    about each source of energy. 
    3. Using the provided information packet, find the answer to your 
    question for all seven energy sources.
    4. Once you have answered your question for all seven sources, answer 
    the two conclusion questions. 

    As a class, we will fill in the energy sources chart based on your findings.

    Research Questions 
    1. What is this energy source? Where can we find it in Rwanda? 
    2. How do we harness the energy? (How does it work?) 
    3. Are there different types or uses of this source? If yes, what are 
    the differences? 
    4. How is this energy source currently used? For example: At farms, 
    in industry etc. Could this source be used in a family home? 

    Note: Prepare a report summarizing your research and present the report 

    to the class.

    Primary energy sources take many forms, including nuclear energy, fossil 
    energy-like oil, coal and natural gas - and renewable sources 
    like wind, solar, geothermal and hydropower. These primary sources are 
    converted to electricity, a secondary energy source, which flows through 
    power lines and other transmission infrastructure to your home and business.

    Activity 3

    Discussion Questions 

    1. If you had to choose an energy system to tell your community about 
    based only on the aspect you researched, which system would you 
    choose? Why? 
    2. Why do we as a nation depend so much on fossil fuels? AND what do 

    you think we could do to reduce this dependence on fossil fuels?

    Note: Prepare a report summarizing your research and present the report 

    to the class.

    C

    While listening to the other groups in your class present their information, list 
    some “pros” and “cons” (advantages and disadvantages) of using their energy 
    source to solve your problem. While listening to the students in your group 
    present their information, list some “pros” and “cons” of using that energy 

    source to solve the energy problem. 

    Advantages and disadvantages of renewable and non-renewable energies

    Activity 6 

    Do research in the library or internet and complete the task below

    1. Complete the chart below about the basic types of renewable energy 

    resources.

    C

    2. List those energy sources that are fossil fuels.
    _____________________________________________________
    _____________________________________________________

    _____________________________________________________

    3. What main advantage do fossil fuels have over the renewable 
    energy resources? 
    _____________________________________________________
    _____________________________________________________

    _____________________________________________________

    4. What are two main disadvantages of fossil fuels compared to 
    renewable energy?
    _____________________________________________________
    _____________________________________________________

    _____________________________________________________

    The sun, prime source of world energy

    Solar energy comes from thermonuclear fusion; 30% of solar energy arriving 
    on higher layers of atmosphere are reflected in space. 47% of that energy are 
    absorbed by the ground and oceans during daytime and become the Earth’s 
    internal energy. The remaining 23% of solar energy are used in evaporation 
    of water of oceans. When it rains, a part of energy is transformed into 
    potential gravitational energy, stocked in mountains, lakes, which are the 
    sources of hydroelectric power. About 0.2% is used by convection currents 
    in atmosphere and creates wind energy. Finally 0.02% is absorbed by plants 

    during photosynthesis and is stocked by them in form of chemical energy. 

    Plants are sources of biomass. Photovoltaic cells transform solar energy in 

    electrical energy.

    The table below show the summary of energy sources

    C

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    Extraction and creation of renewable and non-renewable energy sources 

    Activity 5

    Creation of renewable and non renewable energy
    From what you have already learned, you’ll do also research and tell 
    how these energies are created: Solar energy, hydropower, wind energy, 
    geothermal energy, and biomass. Try to find or to formulate how they are 

    extracted.

    C

    Creation

    Non-renewable resources 

    A non-renewable resource (also called a finite resource) is a resource that 
    does not renew itself at a sufficient rate for sustainable economic extraction 
    in meaningful human time-frames. An example is carbon-based, organically-
    derived fuel. The original organic material, with the aid of heat and pressure, 

    becomes a fuel such as oil or gas.

    Earth minerals and metal ores, fossil fuels(such as coal, petroleum, and natural 
    gas), nuclear fuels, and groundwater in certain aquifers are all non-renewable 

    resources.

    Natural resources such as coal, petroleum (crude oil) and natural gas take 
    thousands of years to form naturally and cannot be replaced as fast as they are 
    being consumed. Eventually it is considered that fossil-based resources will 
    become too costly to harvest and humanity will need to shift its reliance to 

    other sources of energy. These resources are yet to be named. 

    Renewable resources

    Natural resources, known as renewable resources, are replaced by natural 
    processes and forces persistent in the natural environment. There 
    are intermittent and reoccurring renewable and recyclable materials, which are 
    utilized during a cycle across a certain amount of time, and can be harnessed 

    for any number of cycles.

    The production of goods and services by manufacturing products in
    economic systems creates many types of waste during production and after 
    the consumer has made use of it. The material is then incinerated, buried in 
    a landfill or recycled for reuse. Recycling turns materials of value that would 

    otherwise become waste into valuable resources again.

    The natural environment, with soil, water, forests, plants and animals are 
    all renewable resources, as long as they are adequately monitored, protected 
    and conserved. Sustainable agriculture is the cultivation of plant and animal 
    materials in a manner that preserves plant and animal ecosystems over the 
    long term. The overfishing of the oceans is one example of where an industry 
    practice or method can threaten an ecosystem, endanger species and possibly 
    even determine whether or not a fishery is sustainable for use by humans. 
    An unregulated industry practice or method can lead to complete resource 

    depletion.

    Extraction

    Resource extraction involves any activity that withdraws resources from 
    nature. This can range in scale from the traditional use of preindustrial societies, 
    to global industry. Extractive industries are, along with agriculture, the basis 
    of the primary sector of the economy. Extraction produces raw material 
    which is then processed to add value. Examples of extractive industries are 
    hunting, trapping, mining, oil and gas drilling, and forestry. Natural resources 
    can add substantial amounts to a country’s wealth, however a sudden inflow 
    of money caused by a resource boom can create social problems including 
    inflation harming other industries (“Dutch disease”) and corruption, leading 

    to inequality and underdevelopment, this is known as the “resource curse”.

    C

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    END UNIT ASSESSMENT

    1. Differentiate between renewable and non-renewable energy 

    resources?

    2. Using a table to distinguish renewable and nonrenewable resources: 

    Sun, coal, water, natural gas, wood; petroleum; wind; nuclear 

    fission; biomass

    3. Which instrument is used to measure a wind energy? 

    4. What kind of energy will people be using in the future? Why?

    5. What are benefits of renewable energy?

    6. Why don’t people use more renewable energy now?

    7. Are there reasons to use more renewables now rather than wait until 

    the non-renewables run out?

    ◄Unit 5 : Kirchhoff ’s Laws and Electric CircuitsUnit 7 : Projectile and uniform circular motion►