Physics

* 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.

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”?

b) Give the definition of the word “energy” and the term “energy source.”

c) 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.

d) Read carefully these key terms in the table below then give answers to related questions.

Key Terms

Use definitions in the table and decide which of energy sources in (c), include what you added, are renewable and which are non-renewable.

e) From the list given in (c) what is the major category of renewable energy?

f) 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?

g) Discuss in groups this consequence above.

h) List as many as you can uses of renewable energy sources.

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.

Activity 2

Renew-A-Bead In this activity, you will be given a bag of “energy beads.” Each bag contains energy provided by both renewable (white beads) and non-renewable (black beads) sources. You will “use” the energy provided by both types of sources by randomly picking beads from a bag – some of the “energy” you use will be renewable, some will be non-renewable. You will see what happens to the renewable/non-renewable energy sources that remain after many years of energy use.

Materials

* One plastic bag containing 100 beads. The black beads represent non-renewable energy resources and the white beads represent renewable energy resources. (The ratio of white beads to black beads will vary depending on group)

• Group 1= 90 black beads and 10 white beads.

• Group 2= 80 black beads and 20 white beads.

• Group 3= 70 black beads and 30 white beads.

* Small Cloth

* Extra plastic bag

* Calculator

* Pencil

Procedure

1. Split into groups of 2-3 learners.

2. Collect all equipment and materials necessary to carry out the activity.

Part 1: Simulate the annual consumption of energy - constant rate of energy use

3. Have one person from each group pick out 10 “energy beads” from the bag, without looking. These 10 beads represent the energy that is used in one year.

4. Count the black and white beads and record the number on the attached data collection sheet for Year 1.

5. The black beads represent energy from non-renewable energy sources, so when a black bead is picked it cannot be returned to the bag (place it in the extra plastic bag). The white beads are renewable energy beads, so they should be put back into the bag each turn after counting them.

6. Let another person from the group pick 10 beads to represent energy use in Year 2.Fill in the number of black and white beads on the chart, and return the white beads as in step 5.

7. Repeat the process, returning all white beads to the bag after each person’s turn, until 20 years have passed or until all the black energy beads are gone.

Part 2: Simulate the annual consumption of energy - increasing rate of energy use

8. Consider the increasing use of power and energy over time. Repeat steps 3 through 7, but increase the amount of energy use by picking out 5 additional “energy beads” each year (pick 10 beads in year 1, 15 beads in year 2, 20 beads in year 3, etc.). Record information on the attached data collection sheet.

9. Complete the discussion questions.

Discussion Questions

1. How many years did it take for the non-renewable energy sources to run out when you used 10 energy beads per year? How many years did it take for the non-renewable energy sources to run out when you increased the rate of consumption each year (part 2)? What conclusion can you draw from this about our energy use habits?

2. What are some examples of renewable and non-renewable energy sources?

3. What does this activity demonstrate about our consumption of resources - what will happen if we keep using non-renewable resources?

4. Describe what happens to the proportion of renewable vs non-renewable energy sources that remain available, as energy is used over time.

5. Compare the results from teams with different energy mixes. If each bag represents a country, what can you say about countries that currently use a greater fraction of renewable energy? Will they be able to continue to provide for their country’s energy needs?

Data collection for Renew-A-bead

Part 1: 10 energy beads used each year

Data collection for Renew-A-bead

Part 2: Increasing use of energy each year

Activity 3

Learn more about sources of energy

Read these following notes, they talk more about energy sources and some sources of energy related to Rwanda. Understand them because the understanding will help you to do other activities. About different topics, you could also do research on internet. You’ll do also research about advantages and disadvantages of those sources of energy.

Procedure

The learning will be always done in groups. Each member of the group has to make sure that he/she has understood the content read. The explanation must be in terms of discussion in group. For the research on internet or in the library it can be done separately then discussed in groups.

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.

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.

Nuclear fuel

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

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 resources that 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.

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.

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.

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.

How it works - Burning landfill or digester gas to make power

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.

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.

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.

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.

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.

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

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.

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.

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 4

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 5

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.

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.

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.

Extraction and creation of renewable and non-renewable energy sources

Activity 7

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.

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”.