Transcript Chapter 13
Chapter 13 Achieving Energy Sustainability Moon Power • More commonly known as Tidal Energy • Uses the moon’s gravitational force which interacts with Earth’s to create tides twice a day near coastlines and near mouths of rivers. • Kinetic energy of the moving water can be captured and converted into a usable form as the water flows through turbines in a similar way to “windmills” or large dams. • Tides move in and out, so you can harness the energy in both directions. RITE Project • Roosevelt Island Tidal Energy • • Located in the East River in New York. Typical fossil fuel plant produces 500 MW. At full capacity, with 30 turbines, the RITE project will produce 1 MW. • Does this however with little environmental impact: no water diversion, no dams for water storage, mesh enclosures protect fish, invisible from the shore, operates silently. • Even though it will contribute only a small portion of our energy needs, it could be a part of a sustainable energy plan. What is renewable energy? Renewable energy can be rapidly regenerated, and some can never be depleted, no matter how much of them we use. Two types: Potentially renewable: wood and biofuel Nondepletable (no matter how much we use today it won’t affect our tomorrow): wind, solar, hydroelectric, geothermal There are also nonrenewable resources (because we use them faster than they can replenish): Fossil fuels (coal, natural gas, petroleum/oil) and nuclear fuel. U.S. Energy • In the U.S. about 7% of our energy comes from renewable energy. World Ave. U.S. Average How can we use less energy? Energy conservation- finding ways to use less energy. For example, lowering your thermostat during the winter or driving fewer miles. Energy efficiency- getting the same result from using a smaller amount of energy. A truly sustainable approach to energy must incorporate both! Using both are the least expensive way to for maximizing our energy needs…and are fairly simple ways rather than conversion to a new system. Government Involvement • What are some top down approaches to achieving sustainability? • Improve the availability of public transportation • Higher taxes to discourage excess use. • Rebates or tax credits. • Tiered rate system Reducing energy use: There are many ways individuals can reduce their energy consumption. Benefits of Conservation and Efficiency Many energy companies have an extra backup source of energy available to meet the peak demand, the greatest quantity of energy used at any one time. Variable price structure- utility customers can pay less to use energy when demand is lowest and more during peak demand. Second Law of Thermodynamics: as energy is converted, it loses some of that energy as unusable heat… So for us to reduce our electricity use by 100 KWh we may actually be conserving 300 KWh of energy resource such as coal. Sustainable Design Improving the efficiency of the buildings we live and work in. Passive Solar Energy Using passive solar energy can lower your electricity bill without the need for pumps or other mechanical devices. Building the house with windows along a south-facing wall which allows the Sun’s rays to warm the house would be an example. As would… Window shades, using materials with a high thermal inertia, building into a side of a hill or a green roof, better insulation. California Academy of Sciences • • Incorporates a variety of passive solar techniques: radiant heating, solar panels, skylights. Saves 30% on the energy it is actually allowed via building code. BIOMASS Biomass is energy from the Sun The Sun is the ultimate source of almost all types of energy Biomass is energy from the sun. Most types of renewable energy are also derived from the sun and cycles driven by the sun. Biomass accounts for 10% of the world’s energy consumption. Can be refined or processed into liquid fuel (biodiesel and ethanol: known collectively as biofuels) U.S. Energy Consumption 0ther sources 96.5% 2/3 wood 1/6 msw Biomass 3.5% 1/6 biofuels Modern Carbon vs. Fossil Carbon Many people are confused how burning biomass such as wood is better then burning coal. The carbon found in biomass was in the atmosphere as carbon dioxide, taken in by the tree, and by burning it we put it back into the atmosphere (it was taken out more recently) No net increase in Carbon (known as carbon neutral). Burning coal is carbon that has been buried for millions of years and was out of circulation until we began to use it. This results in a rapid increase in the concentration of carbon dioxide in the atmosphere. Biomass Wood, Charcoal and Manure- used to heat homes throughout the world. Removing timber faster than it can grow is a nonsustainable process. Leads to deforestation, may release carbon from the soil (deep in the a and b horizons), erosion, increased water temperatures in nearby rivers and streams, fragmentation of the forest habitats, may harm species that are reliant on old-growth forest habitat. Charcoal is lighter than wood and contains approximately twice as much energy per unit weight. In areas where wood is scarce, people often rely on animal manure. • Biofuels: Ethanol and biodiesel Ethanol and Biodiesel (biofuels)- used as substitutes for gasoline and diesel fuel. • Ethanol is the same alcohol used in alcoholic beverages. • • • More than 90% of the ethanol created in the US comes from corn and corn by-products. Biodiesel is a substitute for regular petroleum diesel. US government is encouraging use of Ethanol and Biodiesel as a way to relieve our dependence on foreign oil while supporting US farmers U.S • The US is the leader in ethanol production, manufacturing approximately 34 billion liters in (9 bill gal.) 2008 • May, 2009-Barack Obama issued a directive to accelerate US investment in and production of biofuels. • Brazil- second largest producer of ethanol (from sugarcane). • Replanted only every 6 years and harvested by hand. Implications for greenhouse gas emissions? • Gasohol Ethanol is usually 10% of a gas/ethanol mixture. • • • Higher oxygen content than gasoline, so less pollution, but also gets less MPG. E-85: 85% ethanol/15%gasoline • Flex-fuel vehicles Other possible alternative: Switchgrass (less sugars, needs more refining) or woodchips Biodiesel • A direct substitute for petroleum diesel. • Typically diluted to B-20, a mixture of 80% petroleum/20% biodiesel. • SVO:Straight Vegetable oil: made from waste vegetable oil that is strained and recycled in an SVO facility. Works with commercially sold kits. • Most biodiesel comes from soybean oil or processed vegetable oil. • Alternatives may be algae. The kinetic energy of water can generate electricity Hydroelectricity- electricity generated by the kinetic energy of moving water. This is the second most common form of renewable energy in the world. 7% of the electricity in the US…more than ½ of this is in the states of CA, WA, OR China is the world’s leader in hydroelectricity followed by Brazil and the US. Captures kinetic energy and uses it to turn a turbine. Amount of electricity depends on the distance it falls or the flow rate or both. Types of hydroelectric power systems Run-of-the-river systems- water is held behind a dam and runs through a channel before returning to the river. Water impoundment- water is stored behind a dam and the gates of the dam are opened and closed controlling the flow of water. Tidal systems- the movement of water is driven by the gravitational pull of the Moon. Is hydroelectric sustainable? • Dams are expensive to build, however… • Minimal amount of fossil fuels. • Large quantities of electricity without air pollution, waste products, Co2 emissions. • Less expensive for the consumer. • Can provide recreational and economic opportunities in the reservoir behind the dam. • Downstream flood control. (Three Gorges Dam) Downsides of Hydro • Three Gorges Dam: Displaced 1.3 Million people, submerged ancient cultural and archaeological sites as well as large areas of farmland. • Impounding water makes it unsuitable for organisms that depend on free flowing which is colder and more oxygen rich. • Some human parasites become more abundant. • Sandbars are created. • Migration patterns/life cycles are disrupted. Capturing the sun’s Energy The Sun’s energy can be captured directly Solar energy: dependent upon cloudiness, time of day, season and geographic location. Passive solar heating-no pumps or mechanics to move the heat. Active solar energy- capturing the energy of sunlight with the use of a pump or photovoltaic cell and generating electricity. Solar water heating systems, photovoltaic systems (PV), Concentrated Solar thermal electricity generation (CST). Solar water heating A solar domestic hot water system. A nonfreezing liquid is circulated by an electric pump through a closed loop of pipes. This circulating liquid moves from a water storage tank to a solar collector on the roof, where it is heated, and back to the tank, where a heat exchanger transfers the heat to water. Photovoltaic solar energy In this domestic photovoltaic system, photovoltaic solar panels convert sunlight into direct current (DC). An inverter converts DC into alternating current (AC), which supplies electricity to the house. Any electricity not used in the house is exported to the electrical grid. Benefits • • • • and No air pollution No water pollution No CO2 production Drawbacks • • • Produce electricity when it is needed most: hot sunny days. • • Initial cost to set up PV panels are expensive Manufacturing PV requires a great deal of energy and water and involves a variety of toxic metals and industrial chemicals. End-of-life reclamation of PV solar cells is a source of environmental contamination Life span <20-30 years Earth’s internal heat produces geothermal energy Geothermal energy- using the heat from natural radioactive decay of elements deep within Earth as well as heat coming from Earth. Wherever magma comes close enough to ground water, the ground water is heated. Where it does not rise to the surface naturally (Yellowstone geysers, etc.) humans may be able to reach it by drilling. US, China, and Iceland have substantial geothermal resources and are the largest producers of geothermal energy. Iceland: 87% of their home heating, 20% of it’s electricity. US 5% of its renewable energy. Can be installed anywhere regardless of whether there is geothermal energy Wind energy is the most rapidly growing source of electricity Wind energy- using a wind turbine to convert kinetic energy into electrical energy. Wind is a result of the unequal heating of Earth. Widely used in some countries and making a comeback in others. Wind energy capacity: Us has the largest capacity, followed by Germany, China, India, and Italy. US only produces 1% of its energy via wind. Denmark: largest user at 21% of their electricity Under average wind conditions: Wind turbine on land may produce electricity 25% of the time, creating 2,000-3,000kW (enough to supply 400 homes a year. Funny comic I found • • • • • • • • • Pros and cons For political and regulatory reasons it is most practical to have wind farms (or parks). Fastest growing source of electricity worldwide. Fossil fuels mostly only used during construction. No pollution, greenhouse gases. Can share land with other uses (farm, cattle land). Rely on batteries to store electricity. Noisy. Ugly??? Some say yes, others say no. Bird/bat migration and flying paths (40,000 birds per year in US) FUEL CELLS Hydrogen fuel cells have many potential applications Fuel cell- a device that operates like a common battery where electricity is generated by a reaction between two chemicals. Main difference: In a fuel cell the reactants are added continuously, so the cell continues to provide energy as long as the fuel is added. 2H2 + O2 energy + 2 H2O Supplying Hydrogen is a challenge because free hydrogen is rare in nature and explosive. 80% efficient H2O only byproduct Electrical grid • The US electricity distribution system is outdated and subject to overloads and outages, which cost the US economy over $100 Billion per year. • Scientists in the US maintain that because we do not have a cost-effective, reliable means of storing energy, that depending on intermittent energy sources would cause the grid to br risky and unstable. • • Smart grid Efficient, self-regulating electricity generating distribution source. • Coordinates energy use with availability. Some experts maintain that a better system would consist of a large number of small scale electricity generating “parks” that rely on a mix of fossil fuel and renewable energy. • Would save money because it would transfer energy over shorter distances leading to less loss (2nd law of thermodynamics) and they would be safer from breakdown and sabotage. They would also cause less large scale outages.