Topic 6 – Alternative Sources of Energy A – The Search for Options B – High Intensity Sources C – Low Intensity Sources
A. The Search for Options Emergence of Alternative Sources Fuel Efficiency The Dominance of the Automobile
1. Emergence of Alternative Sources • Alternative energy • Supplement / replace an energy source with a new source: • The existing energy source judged to be no longer sustainable. • New source judged more convenient than the previous, but comes with its own drawback. • Have always existed: • Wood to coal. • Whale oil to petroleum. • From non-renewable to renewable. • Received increasing attention since the first oil crisis in 1973: • Attention varies with fluctuations in the price of oil. • Since 2005, renewed attention because of a surge in oil prices (e.g. wind, solar).
1. Emergence of Alternative Sources • Stocks and flows • Stock: Existing capital accumulation. • Flows: The nature and extent of new capital investments. • Fossil fuels stocks • Dominate energy supply markets. • Dominance likely to remain on the years to come. • Alternative energy flows • Receiving a growing quantity of flows. • These will eventually expand the alternative energy stocks.
1. Global Carbon Dioxide Emissions from Fossil Fuel Burning by Fuel Type, 1900-2009
1. Average Global Temperature and World Carbon Emissions From Fossil Fuel Burning, 1800-2009
2. Energy Efficiency • Transportation • Minimize traveling distances (commuting, leisure freight). • Improve fuel economy of vehicles. • Shift from petroleum. • Buildings • Temperature control systems (heating, cooling, ventilation). • Insulation. • Lighting and appliances. • Industry • Product life cycle. • Re-use and recycling. • Improve industrial processes.
2. Average Gasoline Consumption for New Vehicles, United States, 1972-2009 (in miles per gallon)
B. High Intensity Sources Hydrogen and Fuel Cells Biomass
1. Hydrogen and Fuel Cells • Hydrogen • Considered to be the cleanest fuel. • Compose 90% of the matter of the universe. • Non polluting (combustion emits only water and heat). • Highest level of energy content. • Almost three times more than methane. • Nuclear fusion • Currently researched but without much success. • It offers unlimited potential. • Not realistically going to be a viable source of energy in the foreseeable future.
1. Hydrogen and Fuel Cells • Fuel cells • Convert fuel energy (such as hydrogen) to electric energy. • No combustion is involved. • Composed of an anode and a cathode. • Fuel is supplied to the anode. • Oxygen is supplied to the cathode. • Electrons are stripped from a reaction at the anode and attracted to form another reaction at the cathode. Hydrogen Oxygen Fuel Fuel Cell Catalytic conversion Water Electricity
1. Hydrogen and Fuel Cells • Storage issues • Hydrogen is a highly combustive gas. • Find a way to safely store it, especially in a vehicle. • Delivery issues • Distribution from producers to consumers. • Production and storage facilities. • Structures and methods for transporting hydrogen. • Fueling stations for hydrogen-powered applications.
1. Hydrogen and Fuel Cells • Hydrogen production • Not naturally occurring; secondary energy resources. • Producing sufficient quantities to satisfy the demand. • Extraction from fossil fuels: • From natural gas. • Steam reforming. • Electrolysis of water: • Electricity from fossil fuels not a environmentally sound alternative. • Electricity from solar or wind energy is a better alternative. • Pyrolysis of the biomass: • Decomposing by heat in an oxygen-reduced atmosphere. Fossil Fuels Steam Reforming Water Electrolysis Biomass Pyrolysis
1. Hydrogen and Fuel Cells • Main potential uses • Transportation: • Most likely replacement for the internal combustion engine. • Efficiency levels are between 55% and 65%. • Stationary power stations: • Connected to the electric grid; supplemental power and backup. • Grid-independent generator. • Telecommunications: • Reliable power for telecom systems (e.g. cell phone towers, internet servers). • Micro Power: • For consumer electronics (e.g. cell phones and portable computers).
2. Biomass • Nature • Biomass energy involves the growing of crops for fuel rather than for food. • Crops can be burned directly to release heat or be converted to useable fuels such methane, ethanol, or hydrogen. • Has been around for many millennia. • Not been used as a large-scale energy source: • 14% of all energy used comes from biomass fuels. • 65% of all wood harvested is burned as a fuel. • 2.4 billion people rely on primitive biomass for cooking and heating. • Important only in developing countries. • Asia and Africa: 75% of wood fuels use. • US: 5% comes from biomass sources.
2. Biomass • Biofuels • Fuel derived from organic matter. • Development of biomass conversion technologies: • Alcohols (ethanol) and methane the most useful. • First generation biofuels: • Food-based. • Plant materials like corn, starch or sugar from cane. • Second generation biofuels: • Cellulosic based. • Waste materials like plant stalks composed of cellulose. • Requirements for sustainable biomass use • Production of biomass through low input levels: • Labor, fuel, fertilizers and pesticides. • Production of biomass on low value land. • Low energy of conversion into biofuels.
2. Biomass • Potential and drawbacks • Competing with other agricultural products for land. • Could contribute to reducing carbon emissions while providing a cheap source of renewable energy: • Burning biofuels does create carbon emissions. • The burned biomass is that which removed carbon from the atmosphere through photosynthesis. • Does not represent a real increase in atmospheric carbon. • Genetic engineering: • Create plants that more efficiently capture solar energy. • Increasing leaf size and altering leaf orientation with regard to the sun. • Conversion technology research: • Seeking to enhance the efficiency rate of converting biomass into energy. • From the 20-25% range up to 35-45% range. • Would render it more cost-competitive with traditional fuels.
C. Low Intensity Sources Solar Energy Wind Power Geothermal Energy
1. Solar Energy • Definition • Radiant energy emitted by the sun. • Large amount of solar energy reaching the Earth’s surface. • 10 weeks of solar energy equivalent to all known fossil fuel reserves. • Advantages • Widely available energy source. • Limited environmental footprint. • Limited maintenance. • Affordable. • Drawbacks • Limitations in temporal availability (e.g. night). • Reconversion of existing facilities. • Can be capital intensive for large projects.
1. Solar Energy Level of insolation (latitude & precipitation) Sun Solar cells Mirrors Concentration Water Evaporation Conversion Steam Turbine Electricity
1. Solar Energy • Photovoltaic systems • Semiconductors to convert solar radiation into electricity. • Better suited for limited uses that do not require large amounts of electricity. • Costs have declined substantially: • 9-10 cents per kilowatt-hour. • Compared to about 3-5 cents for coal fired electrical power. • Economies of scale could then be realized in production of the necessary equipment. • Roofs of buildings (e.g. warehouses) suitable locations to effectively install solar panels.
1. Solar Energy • Solar thermal systems • Parabolic reflectors to focus solar radiation onto water pipes: • Concentrating the sunlight 1000 times. • 212-750F (100-400C), Generating steam that then power turbines. • Require ample, direct, bright sunlight. • Drawback of the solar thermal systems is their dependence on direct sunshine, unlike the photovoltaic cells. • Limitations • Inability to utilize solar energy effectively. • A record of 25% efficiency rate reached in 2008. • Low concentration of the resource. • Need a very decentralized infrastructure to capture energy.
2. Wind Power Sun Heat Air Pressure differences Major prevalent wind systems Wind Wind mills Site suitability Fans Turbine Electricity
2. Wind Power • Potential use • Growing efficiency of wind turbines. • 75% of the world’s usage is in Western Europe: • Provided electricity to some 28 million Europeans in 2002. • Germany, Denmark (18%) and the Netherlands. • New windfarms are located at sea along the coast: • The wind blows harder and more steadily. • Does not consume valuable land. • No protests against wind parks marring the landscape. • United States: • The USA could generate 25% of its energy needs from wind power by installing wind farms on just 1.5% of the land. • North Dakota, Kansas, and Texas have enough harnessable wind energy to meet electricity needs for the whole country.
2. Wind Power • Farms are a good place to implement wind mills: • A quarter of a acre can earn about $2,000 a year in royalties from wind electricity generation. • That same quarter of an acre can only generate $100 worth or corn. • Farmland could simultaneously be used for agriculture and energy generation. • Wind energy could be used to produce hydrogen. • Limitations • Extensive infrastructure and land requirements. • 1980: 40 cents per kwh. • 2001: 3-4 cents per kwh. • Less reliable than other sources of energy. • Inexhaustible energy source that can supply both electricity and fuel.
2. Cumulative Installed Wind Power Capacity in Top Ten Countries and the World, 1980-2011 (Megawatts)
2. Cumulative Installed Offshore Wind Power Capacity by Country, 2009 (Megawatts)
3. Geothermal Energy • Geothermal plants • 2-4 miles below the earth's surface, rock temperature well above boiling point. • Some areas where the natural heat of the earth’s interior is much closer to the surface and can be more readily tapped. • Closely associated with tectonic activity. • Hydrogeothermal: • Taping the aquifer. • Fracturing the rocks, introducing cold water, and recovering the resulting hot water or steam which could power turbines and produce electricity. • Injection well: • In situations where there is no aquifers (hot dry plants). • Drilling a pipe to about 5,000 meters (16,000 feet). • Injecting a liquid (often water) through the pipe.
3. World Geothermal Power in Installed Capacity, 1950-2011 (in megawatts)
3. Geothermal Energy • Geothermal heat pumps • Promising alternative to heating/cooling systems. • Ground below the frost line (about 5 feet) is kept around 55oF year-round. • During winter: • The ground is warmer than the outside. • Heat can be pumped from the ground to the house. • During summer: • The ground is cooler than the outside. • Heat can be pumped from the house to the ground. Winter House 5 feet 55o F Summer House 5 feet 55o F
Renewable sources of energy are also dependent on non-renewable resources • Photovoltaic cells consume non-renewable resources. • Solar-thermal plants consume land and water from aquifers (arid areas). • Geothermal power consumes water from aquifers. • Wind energy consumes land, concrete, steel and rare earths (gearboxes). • All energy supplies require distribution systems (electric wires) that consume land and resources. • The term renewable energy is therefore misleading.