Textbook reference pages: p in Science 30. The Sun is the ultimate source of energy for everything on planet Earth.

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1 Science 30 Unit D Energy and the Environment Outcome 2: Students will describe the sun as Earth s main source of energy and explain the functioning of some conventional and alternative technologies that convert solar, nuclear, tidal and other energy sources into useable forms. Specific Outcome 2.2: Contrast the proportion of solar energy that creates wind and drives the water cycle with the small proportion captured by photosynthesis as chemical potential energy. Specific Outcome 2.3: Describe the conversion of solar energy into renewable forms and non-renewable forms and further conversion into electrical and thermal energy. Specific Outcome 2.12: Explain the source of tides, in terms of gravitational attraction and the relative motions of the sun, moon and Earth. Specific Outcome 2.4: Describe the functioning of renewable energy technologies and assess their advantages and disadvantages, including active and passive solar-heating technologies, wind turbines, hydroelectric power, biomass energy, geothermal energy, hydrogen fuel cells. Specific Outcome 2.13: Describe the energy transformations involved in converting tidal energy to electrical energy and compare tidal power to hydroelectric power. Textbook reference pages: p in Science 30 The Sun is the ultimate source of energy for everything on planet Earth. Through nuclear fission, the Sun converts about 4 billion kilograms of mass into energy every second. Only about one billionth of the energy that the Sun produces per year actually reaches Earth. Of the solar energy that does reach Earth, less than 1% is used in the process of photosynthesis. The land, water and atmosphere absorb a large percentage of incoming solar energy Solar energy drives the water cycle, causes wind and is one of the factors that affect tides. 1

2 ALTERNATIVE ENERGY SOURCES GEOTHERMAL ENERGY caused by the decay of unstable isotopes in Earth s core, which maintains the core at 5000 o C heat collects at boundaries between crustal plates, or where the crust is thin currently used for heat or electricity generation in over thirty countries makes up over a quarter of the Philippines electricity the US is aiming to use geothermal energy for 10% of its power in the western states by 2020 PROS steam is heated without the need for fossil fuels renewable resource generation of energy is cheap and efficient CONS H2S(g) and CO2(g) emissions can result in acid deposition in the area only cost effective in areas close to a geological hotspot Practice Problem The two downsides of geothermal energy are that it can contribute to acid deposition, and that it is only effective in specific locations. List the energy sources you believe share the same downsides. Causes Acid Deposition Geothermal Coal Only effective in Specific Locations Geothermal Tidal Hydro Wind TIDAL ENERGY tides are the result of the interplay between the Earth and the gravitational field of the moon to harness tidal energy, a tidal station uses the difference in Ep(grav) of water between high and low tide in order to spin a turbine and generate electricity 2

3 water on Earth s surface closest to the moon is subject to the strongest gravitational force, g1 water in the Earth s centre is subject to a smaller force, g2 this distorts the shape of the Earth s water surface, forming a tidal bulge water on the far side of the Earth is subject to the smallest force, g3 Earth s centre is actually being pulled away from the water s surface, forming a second tidal bulge as Earth spins, each part of the planet along a sea coast moves through two areas of high tide and two areas of low tide it takes 24 hours for the Earth to rotate once it takes 50 minutes for the moon to move to its highest point There are 2 high tides and 2 low tides per day it is 12h25min between each high tide it is 6h12.5min between high and low tide How do the moon cycles relate to tidal variation? When the sun and moon are aligned during the full moon and new moon the gravitational pull is greater causing very high tides and very low tides called spring tides. When the moon and the sun are not aligned in the first and third quarters of the lunar cycle their gravitational forces partially cancel each other out 3

4 the tides range is less called neap tides. PROS renewable does not produce harmful emissions does not require fossil fuels CONS need a minimum of a 5m difference between high and low tide, which occurs in only a few places tides vary with moon cycle, so energy production is variable can interfere with aquatic ecosystems SOLAR ENERGY nearly all organisms on Earth require solar energy, either directly (by photosynthesis) or indirectly (by consuming other organisms) Passive solar energy Solar energy absorbed by a large object and distributed to other areas by conduction convection radiation Passive solar energy is the delivery of solar energy when it is transmitted through windows and absorbed by dark surfaces No special equipment is needed, but input only occurs when the sun is shining. The heat will remain if the interior is insulated. e.g. in a house, the sun s radiation hits the roof, walls and windows and the heat is then transferred to the rest of the house Active solar energy uses a solar heat collector, which absorbs radiant solar energy converts it into thermal energy this energy is carried by a fluid, and pumped throughout a building 4

5 Practice Problem Looking at the line closely, we can note that the price of natural gas rises and falls each year. What is the biggest factor that explains that rise and fall? The rise and fall correspond to the seasons. Prices rise in the winter due to high demand. Would you expect the cost of active solar heating to fluctuate to the same degree? Why or why not? One would not expect solar heating to fluctuate to the same degree as the sun does not operate on supply and demand The spike in prices in was due to the North American financial crisis. What occurred in 2011 to explain Japan s next spike in cost? The incline after 2011 was a result of Japan losing its main source of nuclear power after the Fukishima earthquake. PHOTOVOLTAIC CELLS converts EMR directly into electricity at the atomic level the material in the cell exhibits a property known as the photoelectric effect that causes the atoms to absorb photons of light and release electrons. when these free electrons are captured, an electric current results that can be used as electricity. a single voltaic cell produces a weak current that is only strong enough to power a small electronic device like a calculator connecting several photovoltaic cells in series (called an array) provides more power but requires a large area 5

6 Practice Problem Traditional solar panels only collected visible light, but new panels are able to collect a wider range of EMR, giving them an improved efficiency of about 35-40%. This is similar to the efficiency of a coal power plant, which we explained by noting the number of energy transformations that occur in the coal-firing process. Is the explanation for the poor efficiency of solar panels also due to these transformations? No, solar panels convert solar energy directly into electricity, so there is only one transformation instead of the five seen with coal. What happens to the 60% of the solar energy that is not converted into electricity? Some of it is waste heat, but most of it is simply reflected back off the panel itself. PROS renewable clean currently being improved to decrease cost and improve efficiency CONS don t work in the dark so batteries are needed for cloudy days and through the night produce DC electricity but most home appliances run on AC, so an inverter is needed to convert DC AC not very efficient expensive to produce, and require toxic heavy metals such as As(s) and Cd(s) HYDROELECTRIC POWER recall, moving water has kinetic energy that kinetic energy can be used to turn a turbine and converted into electrical energy the original energy source for hydro is the Sun, since the water needs heat to form the convection currents that make it move dams are used to concentrate and control the water, which allows a height difference of more than 200m 6

7 hydro power supplies: 19% of world s electricity 95% of Québec s electricity (they sell their excess to the USA) only 5% of Alberta s, the lowest of all the provinces Yangtze River, China PROS CONS huge environmental impact due to renewable clean, for both air and water little waste heat is produced over 80% efficient kw h costs are quite low the size and construction specifications of the water reservoir may require entire communities to be relocated locations must be geologically stable Practice problem: State three similarities and three differences between tidal and hydro. Similarities Both powered by gravitational potential energy of moving water No carbon emissions Both can cause aquatic habitat destruction Differences Tidal is driven by the moon, and hydro by the sun Tidal plants are built on the ocean, hydro plants are built along rivers Hydro power is consistent, whereas tidal is variable The environmental impact of hydro is larger 7

8 Wind energy solar energy creates air currents, which can be converted into electrical energy by wind turbines in southern Alberta, where winds are steady and powerful, wind power has become an important energy source fastest growing form of electricity generation in Canada PROS renewable clean versatile - can be used to power an entire community, or a single home CONS only some areas are suitable can be variable from day to day not very efficient (only about 30%) requires large area of land (though it can be shared for crops or livestock) visual and noise pollution poses a danger to bats and birds BIOMASS plant matter or agricultural waste used as fuel most common form is burning wood biomass can be sustainable, because the CO2 produced from combustion is taken up by the next generation of plants sometimes called a carbonneutral energy source 8

9 PROS fuels are readily available no complex technology is required can be converted into biofuels biofuels burn much cleaner than gasoline CONS not very energy efficient other harmful byproducts besides CO2 are not taken up again biofuel production requires yeast for fermentation process but high concentrations of ethanol is toxic to micro-organisms requires large areas of land and irrigation to make enough organic matter Biofuels organic matter is fermented to make ethanol (C2H5OH) the ethanol can then either be blended with gasoline, or burned directly conventional engines can run on up to 10% ethanol special models can run on up to 85% ethanol Biodiesel 9

10 recall from unit B, biodiesel is a mixture of organic acids obtained from the conversion of waste cooking oil cooking oil is an ester made of large organic acid molecules connected together often contains impurities like H2S(g) which can corrode a car engine Biogas collected during the decomposition of garbage in a landfill the main gas produced during decomp is methane, which is the principal ingredient in natural gas the Cloverbar Landfill in northeast Edmonton collects enough biogas to heat their buildings and warm their composting machines Practice Problem List the eight energy sources we have studied into the following Venn diagram. Fossil fuels Geothermal Solar (PV) Wind Solar Hydro Biomass Tidal Renewable Nuclear 10

11 ALTERNATIVE TO The ALTERNATIVES Hydrogen fuel cells similar in design to a voltaic cell, in that it contains: an electrolyte solution, two electrodes connected to an external circuit H2(g) and O2(g) react to produce water, during which electrons are transferred, creating an electric current used as the power source for space shuttles application of hydrogen fuel cell technology is currently limited by the high cost of the catalysts used size of the cells needed PROS very energy efficient only one emission, water vapour CONS limited supply of elemental hydrogen can be extracted by CH4 or H2O, but both processes require energy this means hydrogen fuel cells may not be considered to be a renewable resource 11

12 Practice Problem: Place the following advantages into this Venn diagram: 1. Available for purchase 2. Long range ( km) 3. Short refueling time 4. Zero emissions 5. Quiet operation 6. Quick and smooth acceleration 7. High fuel efficiency 8. Purchase incentives 9. Changing our resource economy we currently operate on a carbon economy, which means we rely on fossil fuels as our primary source of energy due to its non-renewable nature, the carbon economy is not sustainable 12

13 Investment in renewable energy exploding but not in Canada: Bob McDonald New report shows worldwide investment in alternative energy exceeded investment in new fossil fuel projects Bob McDonald CBC News June 3, 2016 A new report by the Renewable Energy Policy Network has found that, for the first time, worldwide investments in alternative energy have exceeded investments in new fossil fuel projects. It's a sign that the world is taking positive steps toward a clean energy future. But Canada is still behind the major players. The report by the United Nations-sponsored international non-profit association suggests that renewable energy provided roughly 19.2 per cent of global energy consumption in 2014, with 147 Gigawatts of renewable capacity added in That's the largest annual increase ever. An estimated 8.1 million people were employed in the renewable energy sector, not including large-scale hydro, with solar photo-voltaic and biofuels providing the largest numbers of jobs. This is the sixth consecutive year renewables outpaced fossil fuels for net investment in power capacity. Leading the changeover are China, Brazil, the United States and India, with many developing countries following suit. Canada, while not in the top five, scored well in 13

14 hydro power which provides more than half of the country's electricity but has its own set of environmental impacts as well as production of biofuels. But we are still well behind other countries when it comes to investments in wind, solar, geothermal and other renewable energy sources. Cost of alternatives falling The milestone for renewable energy investment is impressive, considering how the bottom has fallen out of the price of oil, making it more economically attractive. But the cost of alternatives has come down as well, and the investment community sees the opportunity for growth. Banks and international investment firms are providing mainstream financing as well as devices such as green bonds and securities. In other words, the private sector believes going green can make money, as well as improve the environment. Canada is in a position to improve our standing on renewables. We have the technical skills to do it, and there is no shortage of clean energy in this vast country of ours: energy that falls from the sky, blows on the wind, even flows in our tides. All we have to do is tap into it. One shining example is the northern community of Colville Lake, N.W.T., located above the Arctic Circle. The town has installed solar panels to provide electricity, especially during the 24 hours of daylight in the summer. Remote communities are usually powered by expensive diesel generators, which also pollute the air. This new hybrid system, which switches to solar whenever the sun is shining, has reduced the town's diesel consumption by 40 per cent. This project is part of a national task force to reduce diesel consumption in remote communities across the country. Why aren't we seeing more of this type of action in larger communities in the south? Canada is in an odd position because we are an oil-producing country. Our fossil fuel resources are huge and in demand by countries like China. So, it is hard to give up the golden goose when it is such a big driver of the economy. But we could still be increasing our investments in renewables at the same time, so that when the popularity of fossil fuels diminishes, which it eventually will, we will not only be energy self-sufficient, but we could also have alternative energy products that would be exportable in that expanding market. It's time Canada caught up to the forward-looking thinking that is happening in the rest of the world. 14