Green energy Physics Unit 5.

Green energy Physics Unit 5

Classification Renewable/ non conventional Non renewable/ conventional

How much solar energy? The surface receives about 47% of the total solar energy that reaches the Earth. Only this amount is usable.

Direct Conversion into Electricity
Photovoltaic cells are capable of directly converting sunlight into electricity. A simple wafer of silicon with wires attached to the layers. Current is produced based on types of silicon (n- and p-types) used for the layers. Each cell=0.5 volts. Battery needed as storage No moving partsdo no wear out, but because they are exposed to the weather, their lifespan is about 20 years.

A proper metal contacts are made on the n-type and p-
A proper metal contacts are made on the n-type and p- type side of the semiconductor for electrical connection Working: When a solar panel exposed to sunlight , the light energies are absorbed by a semiconduction materials. Due to this absorded enrgy, the electrons are libereted and produce the external DC current. The DC current is converted into 240-volt AC current using an inverter for different applications. PH Unit-5 Lecture-2

First, the sunlight is absorbed by a solar cell in a solar panel.
Mechanism: First, the sunlight is absorbed by a solar cell in a solar panel. The absorbed light causes electrons in the material to increase in energy. At the same time making them free to move around in the material. However, the electrons remain at this higher energy for only a short time before returning to their original lower energy position. Therefore, to collect the carriers before they lose the energy gained from the light, a PN junction is typically used. PH Unit-5 Lecture-2

A PN junction consists of two different regions of a
A PN junction consists of two different regions of a semiconductor material (usually silicon), with one side called the p type region and the other the n-type region. During the incident of light energy, in p-type material, electrons can gain energy and move into the n-type region. Then they can no longer go back to their original low energy position and remain at a higher energy. The process of moving a light- generated carrier from p-type region to n-type region is called collection. These collections of carriers (electrons) can be either extracted from the device to give a current, or it can remain in the device and gives rise to a voltage. PH Unit-5 Lecture-2

The electrons that leave the solar cell as current give
The electrons that leave the solar cell as current give up their energy to whatever is connected to the solar cell, and then re-enter the solar cell. Once back in the solar cell, the process begins again: PH Unit-5 Lecture-2

The mechanism of electricity production- Different stages
Conduction band High density Valence band Low density E The above diagram shows the formation of p-n junction in a solar cell. The valence band is a low-density band and conduction band is high-density band. PH Unit-5 Lecture-2

Stage-1 When light falls on the semiconductor surface, the electron from valence band promoted to conduction band. Therefore, the hole (vacancy position left by the electron in the valence band) is generates. Hence, there is a formation of electron-hole pair on the sides of p-n junction. Conduction band High density Valence band Low density E PH Unit-5 Lecture-2

Stage-2 In the stage 2, the electron and holes are diffuse across the p-n junction and there is a formation of electron-hole pair. Conduction band High density Valence band Low density E junction PH Unit-5 Lecture-2

Stage-3 In the stage 3, As electron continuous to diffuse, the negative charge build on emitter side and positive charge build on the base side. Conduction band High density Valence band Low density E junction PH Unit-5 Lecture-2

Stage-4 When the PN junction is connected with external circuit, the current flows. Conduction band High density Valence band Low density E junction Power PH Unit-5 Lecture-2

A solar panel (or) Solar array
Single solar cell The single solar cell constitute the n-type layer sandwiched with p-type layer. The most commonly known solar cell is configured as a large-area p-n junction made from silicon wafer. A single cell can produce only very tiny amounts of electricity It can be used only to light up a small light bulb or power a calculator. Single photovoltaic cells are used in many small electronic appliances such as watches and calculators PH Unit-5 Lecture-2

Single Solar cell N-type P-type PH Unit-5 Lecture-2

Solar panel (or) solar array (or) Solar module
The solar panel (or) solar array is the interconnection of number of solar module to get efficient power. A solar module consists of number of interconnected solar cells. These interconnected cells embedded between two glass plate to protect from the bad whether. Since absorption area of module is high, more energy can be produced. PH Unit-5 Lecture-2

PH Unit-5 Lecture-2

Types of Solar cell Monocrystalline silicon cells
Based on the types of crystal used, soar cells can be classified as, Monocrystalline silicon cells Polycrystalline silicon cells Amorphous silicon cells The Monocrystalline silicon cell is produced from pure silicon (single crystal). Since the Monocrystalline silicon is pure and defect free, the efficiency of cell will be higher. In polycrystalline solar cell, liquid silicon is used as raw material and polycrystalline silicon was obtained followed by solidification process. The materials contain various crystalline sizes. Hence, the efficiency of this type of cell is less than Monocrystalline cell. PH Unit-5 Lecture-2

Amorphous silicon was obtained by depositing silicon film
Amorphous silicon was obtained by depositing silicon film on the substrate like glass plate. The layer thickness amounts to less than 1µm – the thickness of a human hair for comparison is µm. The efficiency of amorphous cells is much lower than that of the other two cell types. As a result, they are used mainly in low power equipment, such as watches and pocket calculators, or as facade elements. PH Unit-5 Lecture-2

Comparison of Types of solar cell
Material Efficiency (%) Monocrystalline silicon 14-17 Polycrystalline silicon 13-15 Amorphous silicon 5-7 PH Unit-5 Lecture-2

Advantage, disadvantage and application of Solar cell
It is clean and non-polluting It is a renewable energy Solar cells do not produce noise and they are totally silent. They require very little maintenance They are long lasting sources of energy which can be used almost anywhere They have long life time There are no fuel costs or fuel supply problems PH Unit-5 Lecture-2

Solar power can’t be obtained in night time
Disadvantage Solar power can’t be obtained in night time Solar cells (or) solar panels are very expensive Energy has not be stored in batteries Air pollution and whether can affect the production of electricity They need large are of land to produce more efficient power supply PH Unit-5 Lecture-2

WIND POWER What is it? How does it work? Efficiency

WIND POWER - What is it? All renewable energy (except tidal and geothermal power), ultimately comes from the sun The earth receives 2 x 1017 watts of power (per hour) from the sun About 2 percent of this energy is converted to wind energy Differential heating of the earth’s surface and atmosphere induces vertical and horizontal air currents that are affected by the earth’s rotation and contours of the land  WIND. ~ e.g.: Land Sea Breeze Cycle

Wind is slowed by the surface roughness and obstacles.
A wind turbine obtains its power input by converting the force of the wind into a torque (turning force) acting on the rotor blades. The amount of energy which the wind transfers to the rotor depends on the density of the air, the rotor area, and the wind speed. The kinetic energy of a moving body is proportional to its weight. In other words, the "heavier" the air, the more energy is received by the turbine.

KidWind Project | www.kidwind.org

Wind Turbines LARGE TURBINES:
Able to deliver electricity at lower cost than smaller turbines, because foundation costs, planning costs, etc. are independent of size. Well-suited for offshore wind plants. In areas where it is difficult to find sites, one large turbine on a tall tower uses the wind extremely efficiently.

SMALL TURBINES: Local electrical grids may not be able to handle the large electrical output from a large turbine, so smaller turbines may be more suitable. High costs for foundations for large turbines may not be economical in some areas. Landscape considerations

Wind Turbines: Number of Blades
Most common design is the three-bladed turbine. The most important reason is the stability of the turbine. A rotor with an odd number of rotor blades (and at least three blades) can be considered to be similar to a disc when calculating the dynamic properties of the machine. A rotor with an even number of blades will give stability problems for a machine with a stiff structure.

Wind Turbine Generators
Wind power generators convert wind energy (mechanical energy) to electrical energy. The generator is attached at one end to the wind turbine, which provides the mechanical energy. At the other end, the generator is connected to the electrical grid. The generator needs to have a cooling system to make sure there is no overheating.

Power of Wind *No other factor is more important to the amount of power available in the wind than the speed of the wind The power in wind is proportional to the cubic wind speed ( v^3 ). 20% increase in wind speed means 73% more power Doubling wind speed means 8 times more power WHY? ~ Kinetic energy of an air mass is proportional to v^2 ~ Amount of air mass moving past a given point is proportional to wind velocity (v)

Calculation of Wind Power
Power in the wind Effect of air density,  Effect of swept area, A Effect of wind speed, V Power in the Wind = ½ρAV3 R This is the equation for the power in the wind. (Don’t fear – there are only 2 equations in this presentation.) Each of the terms in this equation can tell us a lot about wind turbines and how they work. Lets look at wind speed (V), swept area (A), and density (Greek letter “rho,” ) one at a time. First, let’s look at wind speed, V. Because V is cubed in the equation, a small increase in V makes for a increase in power. (illustrated on next slide) (Click on the links at the bottom to get the values of both k and .) Swept Area: A = πR2 Area of the circle swept by the rotor (m2).

Environmental benefits
No emissions No fuel needed Distributed power Remote locations

Limitations of Wind Power
Power density is very low. Needs a very large number of wind mills to produce modest amounts of power. Cost. Environmental costs. material and maintenance costs. Noise, birds and appearance. Cannot meet large scale and transportation energy needs.

The Future of Wind Energy
Future of wind energy can be bright if government policies subsidize and encourage its use. Technology improvements unlikely to have a major impact. Can become cost competitive for electricity generation if fossil energy costs skyrocket.

Ocean Energy From waves From tides
Thermal energy-OTEC(Ocean Thermal Electric Conversion) Mechanical energy From waves From tides

Wave Facts: Mechanical energy-From waves
Waves are caused by a number of forces, i.e. wind, gravitational pull from the sun and moon, changes in atmospheric pressure, earthquakes etc. Waves created by wind are the most common waves. Unequal heating of the Earth’s surface generates wind, and wind blowing over water generates waves. Wave energy is an irregular and oscillating low-frequency energy source that must be converted to a 50-Hertz frequency before it can be added to the electric utility grid.

Three Basic Kinds of Systems
Offshore (so your dealing with swell energy not breaking waves) Near Shore (maximum wave amplitude) Embedded devices (built into shoreline to receive breaking wave – but energy loss is occurring while the wave is breaking)

3 basic systems for ocean wave energy devices
1. Channel systems that funnel waves into reservoirs 2. Float systems that drive hydraulic pumps 3. Oscillating water column systems that use waves to compress air within a container mechanical power either directly activates a generator, or transfers to a working fluid, water or air, which then drives a turbine/generator

Wave Power Designs Wave Surge or Focusing Devices-Channel System These shoreline devices, also called "tapered channel" systems, rely on a shore-mounted structure to channel and concentrate the waves, driving them into an elevated reservoir. These focusing surge devices are sizable barriers that channel large waves to increase wave height for redirection into elevated reservoirs.

Floats or Pitching Devices These devices generate electricity from the bobbing or pitching action of a floating object. The object can be mounted to a floating raft or to a device fixed on the ocean floor.

Oscillating Water Columns (OWC) These devices generate electricity from the wave-driven rise and fall of water in a cylindrical shaft. The rising and falling water column drives air into and out of the top of the shaft, powering an air-driven turbine. 17-42 42

-Advantages and Disadvantages-
The energy is free – no fuel needed, no waste produced Not expensive to operate and maintain Can produce a great deal of energy Disadvantages Depends on the waves – sometimes you’ll get loads of energy, sometimes almost nothing Needs a suitable site, where waves are consistently strong Some designs are noisy. But then again, so are waves, so any noise is unlikely to be a problem Must be able to withstand

Tidal Power Tidal power generators derive their energy from movement of the tides. Has potential for generation of very large amounts of electricity, or can be used in smaller scale.

The interaction of the Moon and the Earth results in the oceans bulging out towards the Moon (Lunar Tide). The sun’s gravitational field pulls as well (Solar Tide) As the Sun and Moon are not in fixed positions in the celestial sphere, but change position with respect to each other, their influence on the tidal range (difference between low and high tide) is also effected. If the Moon and the Sun are in the same plane as the Earth, the tidal range is the superposition of the range due to the lunar and solar tides. This results in the maximum tidal range (spring tides). If they are at right angles to each other, lower tidal differences are experienced resulting in neap tides. Tides

How do tides changing = Electricity?
As usual, the electricity is provided by spinning turbines. Two types of tidal energy can be extracted: kinetic energy of currents between ebbing (tide going out) and surging tides(tide coming in) and potential energy from the difference in height (or head) between high and low tides. The potential energy contained in a volume of water is E = xMg where x is the height of the tide, M is the mass of water and g is the acceleration due to gravity.

Two types: 1.) Tidal Barrage Single basin system Double-basin system
Utilize potential energy Tidal barrages are typically dams built across an estuary or bay. consist of turbines, sluice gates, embankments, and ship locks. Two types: Single basin system Double-basin system Basin

Single basin system- Ebb generation: During flood tide basin is filled and sluice gates are closed , trapping water. Gates are kept closed until the tide has ebbed sufficiently and thus turbines start spinning and generating electricity. Flood generation: The basin is filled through the turbine which generate at flood tide. Two way generation: Sluice gates and turbines are closed until near the end of the flood tide when water is allowed to flow through the turbines into the basin creating electricity. At the point where the hydrostatic head is insufficient for power generation the sluice gates are opened and kept open until high tide when they are closed. When the tide outside the barrage has dropped sufficiently water is allowed to flow out of the basin through the turbines again creating electricity.

Double-basin system There are two basins, but it operates similar to en ebb generation, single-basin system. The only difference is a proportion of the electricity is used to pump water into the second basin allowing storage.

Ocean Thermal Energy Conversion
Ocean thermal energy conversion (OTEC) is a method for generating electricity which uses the temperature difference that exists between deep and shallow waters

The ocean stores thermal energy
Each day, the tropical oceans absorb an amount of solar radiation equal to the heat content of 250 billion barrels of oil The ocean’s surface is warmer than deep water Ocean thermal energy conversion (OTEC) is based on this gradient in temperature Closed cycle approach = warm surface water evaporates chemicals, which spin turbines Open cycle approach = warm surface water is evaporated in a vacuum and its steam turns turbines Costs remain high and no facility is commercially operational 17-52

OTEC: What is it? Thermal energy- form of energy that manifests itself as an increase of temp. Method for generating electricity. Runs a heat engine- a physical device that converts thermal energy to mechanical output Uses temp. difference that exists b/w deep & shallow waters. Temperature difference between warm surface water and cold deep water must be >20°C (36°F) for OTEC system to produce significant power.

Ocean Thermal Energy Conversion (OTEC)
Ocean Thermal Energy Conversion produces electricity from the natural thermal gradient of the ocean, using the heat stored in warm surface water to create steam to drive a turbine, while pumping cold, deep water to the surface to re-condense the steam.

Closed Cycle OTEC In closed-cycle OTEC, warm seawater heats a working fluid, such as ammonia, with a low boiling point, such as ammonia, which flows through a heat exchanger (evaporator). The ammonia vapor expands at moderate pressures turning a turbine, which drives a generator which produces energy.

OTEC: Closed Cycle The vapor is then condensed in another heat exchanger (condenser) by the cold, deep-ocean water running through a cold water pipe. The working fluid (ammonia) is then cycled back through the system, being continuously recycled.

Ocean Thermal Energy Conversion
(OTEC) There is no OTEC facility currently producing electricity at Keahole Point. However, cold seawater is being used directly to air condition (cool) the administration and laboratory buildings. The seawater provides about 50 tons of air conditioning, offsetting the equivalent of 200 kW of peak electrical demand. Using the cold seawater for air conditioning saves NELHA nearly $4000 per month in electricity cost - and the system requires much less maintenance than traditional compressor systems.

Open Cycle OTEC In an open-cycle OTEC plant, warm seawater from the surface is the working fluid that is pumped into a vacuum chamber where it is flash- evaporated to produce steam at an absolute pressure of about 2.4 kilopascals (kPa). The resulting steam expands through a low-pressure turbine that is hooked up to a generator to produce electricity. The steam that exits the turbine is condensed by cold, deep-ocean water, which is returned to the environment. If a surface condenser is used, the condensed steam remains separated from the cold ocean water and can be collected as a ready source of desalinated water for commercial, domestic or agricultural use.

OTEC Open Cycle System In an open-cycle plant, the warm water, after being vaporized, can be re-condensed and separated from the cold seawater, leaving behind the salt and providing a source of desalinated water fresh enough for municipal or agricultural use.

OTEC Hybrid Cycle System
Hybrid plants, combining benefits of the two systems, would use closed-cycle generation combined with a second-stage flash evaporator to desalinate water.

OTEC limited applications
Very costly Limited suitable sites can’t justify for electricity – must also desalinize, sustain aquaculture, etc…

Geothermal Energy

Sources of Earth’s Internal Energy
70% comes from the decay of radioactive nuclei with long half lives that are embedded within the Earth Some energy is from residual heat left over from Earths formation. The rest of the energy comes from meteorite impacts. Geothermal energy Renewable energy is generated from deep within the Earth Radioactive decay of elements under extremely high pressures deep inside the planet generates heat This heat rises through magma, fissures, and cracks Geothermal power plants use heated water and steam for direct heating and generating electricity

Different Geothermal Energy Sources
1.Hydrothermal resources: a)Hot Water Reservoirs: As the name implies these are reservoirs of hot underground water. There is a large amount of them in the US, but they are more suited for space heating than for electricity production. b)Natural Stem Reservoirs: In this case a hole dug into the ground can cause steam to come to the surface. This type of resource is rare in the US.

2.Geopressured Reservoirs: In this type of reserve, brine completely saturated with natural gas in stored under pressure from the weight of overlying rock. This type of resource can be used for both heat and for natural gas. Normal Geothermal Gradient: At any place on the planet, there is a normal temperature gradient of +300C per km dug into the earth. Therefore, if one digs 20,000 feet the temperature will be about 1900C above the surface temperature. This difference will be enough to produce electricity. However, no useful and economical technology has been developed to extracted this large source of energy. 3.Molten Magma: No technology exists to tap into the heat reserves stored in magma. The best sources for this in the US are in Alaska and Hawaii.

4. Hot Dry Rock: This type of condition exists in 5% of the US
4.Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to Normal Geothermal Gradient, but the gradient is 400C/km dug underground. The simplest models have one injection well and two production wells. Pressurized cold water is sent down the injection well where the hot rocks heat the water up. Then pressurized water of temperatures greater than 2000F is brought to the surface and passed near a liquid with a lower boiling temperature, such as an organic liquid like butane. The ensuing steam turns the turbines. Then, the cool water is again injected to be heated. This system does not produce any emissions. US geothermal industries are making plans to commercialize this new technology.

Geothermal energy is renewable in principle
But if a geothermal plant uses heated water faster than groundwater is recharged, the plant will run out of water Operators have begun injecting municipal wastewater into the ground to replenish the supply 17-67

We can harness geothermal energy for heating and electricity
Geothermal ground source heat pumps (GSHPs) use thermal energy from near-surface sources of earth and water The pumps heat buildings in the winter by transferring heat from the ground into buildings In the summer, heat is transferred through underground pipes from the building into the ground Highly efficient, because heat is simply moved 17-68

Use of geothermal power is growing
Currently, geothermal energy provides less than 0.5% of the total energy used worldwide It provides more power than solar and wind combined But much less than hydropower and biomass Commercially viable only in British Columbia In the right setting, geothermal power can be among the cheapest electricity to generate 17-69

Geothermal power has benefits and limitations
Reduces emissions It does emit very small amounts of gases Limitations: May not be sustainable, as CO2 can be released Water is laced with salts and minerals that corrode equipment and pollute the air Limited to areas where the energy can be trapped 17-70

Biomass Biomass is a renewable energy source that is derived from living or recently living organisms. Biomass includes biological material, not organic material like coal. Energy derived from biomass is mostly used to generate electricity or to produce heat. Thermal energy is extracted by means of combustion, torrefaction, pyrolysis, and gasification. Biomass can be chemically and biochemically treated to convert it to a energy-rich fuel.

Biomass Resources Energy Crops Waste Products Woody crops
Agricultural crops Waste Products Wood residues Temperate crop wastes Tropical crop wastes Animal wastes Municipal Solid Waste (MSW) Commercial and industrial wastes Biomass Resources Biomass resources include any organic matter available on a renewable basis, including dedicated energy crops and trees, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, animal wastes, municipal wastes, and other waste materials. Material handling, collection logistics and infrastructure are important aspects of the biomass resource supply chain. Resources Herbaceous Energy Crops Herbaceous energy crops are perennials that are harvested annually after taking two to three years to reach full productivity. These include such grasses as switchgrass, miscanthus (also known as Elephant grass or e-grass), bamboo, sweet sorghum, tall fescue, kochia, wheatgrass, and others. Woody Energy Crops Short-rotation woody crops are fast growing hardwood trees harvested within five to eight years after planting. These include hybrid poplar, hybrid willow, silver maple, eastern cottonwood, green ash, black walnut, sweetgum, and sycamore. Industrial Crops Industrial crops are being developed and grown to produce specific industrial chemicals or materials. Examples include kenaf and straws for fiber, and castor for ricinoleic acid. New transgenic crops are being developed that produce the desired chemicals as part of the plant composition, requiring only extraction and purification of the product. Agricultural Crops These feedstocks include the currently available commodity products such as cornstarch and corn oil; soybean oil and meal; wheat starch, other vegetable oils, and any newly developed component of future commodity crops. They generally yield sugars, oils, and extractives, although they can also be used to produce plastics and other chemicals and products. Aquatic Crops A wide variety of aquatic biomass resources exist such as algae, giant kelp, other seaweed, and marine microflora. Commercial examples include giant kelp extracts for thickeners and food additives, algal dyes, and novel biocatalysts for use in bioprocessing under extreme environments. Agriculture Crop Residues Agriculture crop residues include biomass, primarily stalks and leaves, not harvested or removed from the fields in commercial use. Examples include corn stover (stalks, leaves, husks and cobs), wheat straw, and rice straw. With approximately 80 million acres of corn planted annually, corn stover is expected to become a major biomass resource for bioenergy applications. Forestry Residues Forestry residues include biomass not harvested or removed from logging sites in commercial hardwood and softwood stands as well as material resulting from forest management operations such as pre-commercial thinnings and removal of dead and dying trees. Municipal Waste Residential, commercial, and institutional post-consumer wastes contain a significant proportion of plant derived organic material that constitute a renewable energy resource. Waste paper, cardboard, wood waste and yard wastes are examples of biomass resources in municipal wastes. Biomass Processing Residues All processing of biomass yields byproducts and waste streams collectively called residues, which have significant energy potential. Residues are simple to use because they have already been collected. For example, processing of wood for products or pulp produces sawdust and collection of bark, branches and leaves/needles. Animal Wastes Farms and animal processing operations create animal wastes that constitute a complex source of organic materials with environmental consequences. These wastes can be used to make many products, including energy.

Conversion Technologies
A wide variety of technologies is deployed for energy production from biomass →Production of heat , electricity and transport fuels is possible through a portfolio of technologies

Conversion technologies: power and heat
Digestion : Biogas is released with the digestion of organic material Combustion: Because heat releases with the combustion of biomass, electricity can be aroused using a steam turbine Gasification: high heating of organic material, releases biogas Production of bio-oils

Conversion technologies: biofuels for the transport Sector
Extraction and production of esters from oilseeds Fermentation: production of ethanol Methanol, hydrogen and hydrocarbons via Gasification

ENVIRONMENTAL ADVANTAGES
Renewable resource Reduces landfills Protects clean water supplies Reduces acid rain and smog Reduces greenhouse gases Carbon dioxide Methane

BIOMASS AND CARBON EMMISIONS
Biomass emits carbon dioxide when it naturally decays and when it is used as an energy source Living biomass in plants and trees absorbs carbon dioxide from the atmosphere through photosynthesis Biomass causes a closed cycle with no net emissions of greenhouse gases

GEOGRAPHIC AREAS Comes from the forest
Can also come from plant and animal waste Wood and waste can be found virtually anywhere Transportation costs

Introduction: What is Biodiesel?
A diesel fuel replacement produced from vegetable oils or animal fats through the chemical process of transesterification Mono-alkyl esters Biodiesel can be used in any diesel motor in any percent from 0-100% with little or no modifications to the engine Not the same as straight vegetable oils, oils are converted to methyl esters BXX = volume XX% biodiesel

Why make biodiesel? Biodiesel
Diesel fuel injectors are not designed for viscous fuels like vegetable oil Glycerin (thick)

The Chemistry of Biodiesel
All fats and oils consist of triglycerides Glycerol/glycerine = alcohol 3 fatty acid chains (FA) Transesterification describes the reaction where glycerol is replaced with a lighter and less viscous alcohol e.g. Methanol or ethanol A catalyst (KOH or NaOH) is needed to break the glycerol-FA bonds

Transesterification (the biodiesel reaction)
Methanol (or Ethanol) Biodiesel Triglyceride Glycerol One triglyceride molecule is converted into three mono alkyl ester (biodiesel) molecules Fatty Acid Chain

Vegetable Oil as Feedstocks
Oil-seed crops are the focus for biodiesel production expansion Currently higher market values for competing uses constrain utilization of crops for biodiesel production Most oil-seed crops produce both a marketable oil and meal Seeds must be crushed to extract oil The meal often has higher market value than the oil

Soybeans Canola/Rapeseed
Primary source for biodiesel production in U.S. Approximately 2 billion gallons of oil produced annually Canola/Rapeseed Rapeseed is a member of the mustard family Canola is a variety of rapeseed bred to have low levels of erucic acid and glucosinolates (both of which are undesireable for human consumption) Good oil yield

Camelina Sunflowers Camelina sativa is a member of mustard family
Wide geographical range for production Market value is high for edible oil and seeds, birdseeds Second largest biodiesel feedstock in the EU Camelina Camelina sativa is a member of mustard family Summer annual crop suited to grow in semi-arid climates and northern U.S.

Advantages of Biodiesel
Biodegradable Non-toxic Favorable Emissions Profile Renewable Carbon Neutrality Requires no engine modifications (except replacing some fuel lines on older engines). Can be blended in any proportion with petroleum diesel fuel. Can be made from waste restaurant oils and animal fats

Disadvantages of biodiesel
Lower Energy Content 8% fewer BTU’s per gallon, but also higher cetane #, lubricity, etc. Poor cold weather performance This can be mitigated by blending with diesel fuel or with additives, or using low gel point feedstocks such as rapeseed/canola. Stability Concerns Biodiesel is less oxidatively stable than petroleum diesel fuel. Old fuel can become acidic and form sediments and varnish. Additives can prevent this. Scalability Current feedstock technology limits large scalability Btu/lb Btu/gal No. 2 Diesel 18, ,050 B , ,170 (12.5% less) (8% less)

Fuel Cells

PEM Fuel Cell

Parts of a Fuel Cell Anode Cathode Electrolyte Catalyst
Negative post of the fuel cell. Conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. Etched channels disperse hydrogen gas over the surface of catalyst. Cathode Positive post of the fuel cell Etched channels distribute oxygen to the surface of the catalyst. Conducts electrons back from the external circuit to the catalyst Recombine with the hydrogen ions and oxygen to form water. Electrolyte Proton exchange membrane. Specially treated material, only conducts positively charged ions. Membrane blocks electrons. Catalyst Special material that facilitates reaction of oxygen and hydrogen Usually platinum powder very thinly coated onto carbon paper or cloth. Rough & porous maximizes surface area exposed to hydrogen or oxygen The platinum-coated side of the catalyst faces the PEM.

Fuel Cell Operation Pressurized hydrogen gas (H2) enters cell on anode side. Gas is forced through catalyst by pressure. When H2 molecule comes contacts platinum catalyst, it splits into two H+ ions and two electrons (e-). Electrons are conducted through the anode Make their way through the external circuit (doing useful work such as turning a motor) and return to the cathode side of the fuel cell. On the cathode side, oxygen gas (O2) is forced through the catalyst Forms two oxygen atoms, each with a strong negative charge. Negative charge attracts the two H+ ions through the membrane, Combine with an oxygen atom and two electrons from the external circuit to form a water molecule (H2O).

Proton-Exchange Membrane Cell
How a fuel cell works: In the polymer electrolyte membrane (PEM) fuel cell, also known as a proton-exchange membrane cell, a catalyst in the anode separates hydrogen atoms into protons and electrons. The membrane in the center transports the protons to the cathode, leaving the electrons behind. The electrons flow through a circuit to the cathode, forming an electric current to do useful work. In the cathode, another catalyst helps the electrons, hydrogen nuclei and oxygen from the air recombine. When the input is pure hydrogen, the exhaust consists of water vapor. In fuel cells using hydrocarbon fuels the exhaust is water and carbon dioxide. Cornell's new research is aimed at finding lighter, cheaper and more efficient materials for the catalysts and membranes.

Fuel Cell Energy Exchange
Hydrogen and oxygen can be combined in a fuel cell to produce electrical energy. A fuel cell uses a chemical reaction to provide an external voltage, as does a battery, but differs from a battery in that the fuel is continually supplied in the form of hydrogen and oxygen gas. It can produce electrical energy at a higher efficiency than just burning the hydrogen to produce heat to drive a generator because it is not subject to the thermal bottleneck from the second law of thermodynamics. It's only product is water, so it is pollution-free. All these features have led to periodic great excitement about its potential, but we are still in the process of developing that potential as a pollution-free, efficient energy source (see Kartha and Grimes).

PEM Fuel Cell Schematic
Figure 5. In a proton−exchange−membrane fuel cell, hydrogen and oxygen react electrochemically. At the anode, hydrogen molecules dissociate, the atoms are ionized, and electrons are directed to an external circuit; protons are handed off to the ion−exchange membrane and pass through to the cathode. There, oxygen combines with protons from the ion−exchange membrane and electrons from the external circuit to form water or steam. The energy conversion efficiency of the process can be 60% or higher.

Hydrogen Fuel Cell Efficiency
40% efficiency converting methanol to hydrogen in reformer 80% of hydrogen energy content converted to electrical energy 80% efficiency for inverter/motor Converts electrical to mechanical energy Overall efficiency of 24-32%

Auto Power Efficiency Comparison
Technology System Efficiency Fuel Cell 24-32% Electric Battery 26% Gasoline Engine 20% Maybe you are surprised by how close these three technologies are. This exercise points out the importance of considering the whole system, not just the car. We could even go a step further and ask what the efficiency of producing gasoline, methanol or coal is. Efficiency is not the only consideration, however. People will not drive a car just because it is the most efficient if it makes them change their behavior. They are concerned about many other issues as well. They want to know: Is the car quick and easy to refuel? Can it travel a good distance before refueling? Is it as fast as the other cars on the road? How much pollution does it produce? This list, of course, goes on and on. In the end, the technology that dominates will be a compromise between efficiency and practicality.

Other Types of Fuel Cells
Alkaline fuel cell (AFC) This is one of the oldest designs. It has been used in the U.S. space program since the 1960s. The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized. Phosphoric-acid fuel cell (PAFC) The phosphoric-acid fuel cell has potential for use in small stationary power-generation systems. It operates at a higher temperature than PEM fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars. Solid oxide fuel cell (SOFC) These fuel cells are best suited for large-scale stationary power generators that could provide electricity for factories or towns. This type of fuel cell operates at very high temperatures (around 1,832 F, 1,000 C). This high temperature makes reliability a problem, but it also has an advantage: The steam produced by the fuel cell can be channeled into turbines to generate more electricity. This improves the overall efficiency of the system. Molten carbonate fuel cell (MCFC) These fuel cells are also best suited for large stationary power generators. They operate at 1,112 F (600 C), so they also generate steam that can be used to generate more power. They have a lower operating temperature than the SOFC, which means they don't need such exotic materials. This makes the design a little less expensive.

Advantages/Disadvantages of Fuel Cells
Water is the only discharge (pure H2) Disadvantages CO2 discharged with methanol reform Little more efficient than alternatives Technology currently expensive Many design issues still in progress Hydrogen often created using “dirty” energy (e.g., coal) Pure hydrogen is difficult to handle Refilling stations, storage tanks, …

What is a Gas Hydrate? A gas hydrate is a crystalline solid; its building blocks consist of a gas molecule surrounded by a cage of water molecules. It is similar to ice, except that the crystalline structure is stabilized by the guest gas molecule within the cage of water molecules. Suitable gases are: carbon dioxide, hydrogen sulfide, and several low-carbon-number hydrocarbons. Most gas hydrates , however are Methane Hydrates.

What are Methane Hydrates?
Methane Hydrates are one example of ‘clathrates’ Clathrates are compounds which consist of a ‘cage structure’, in which a gas molecule is trapped inside a cage of water molecules Methane (CH4) is trapped in Water (H2O) forming an “ICE”

1 m3 of hydrate -> ~170 m3 methane gas (STP)
Grey=carbon Green=hydrogen in CH4 Red = oxygen White= hydrogen in H2O 1 m3 of hydrate -> ~170 m3 methane gas (STP)

Hydrate Samples Gas hydrates in sea-floor mounds Here methane gas is actively dissociating from a hydrate mound. Gas hydrate can occur as nodules, laminae, or veins within sediment.

Gas Hydrate on the Sea floor
Beasties!

Origin of natural methane
Bacterial degradation of organic matter in low-oxygen environments within sediments Thermal degradation of organic matter, dominantly in petroleum (e.g., Gulf of Mexico)

Where do clathrates occur? How much clathrate is there?
Methane and water must be available (organic matter: produced by biota; in oceans: close to continents) Clathrate must be stable (ice): cold and/or high pressure High latitudes (permafrost) In medium deep sea sediments ( m)

How much hydrate is there?
Estimates vary widely: globally 600,000 to 2,000,000 Tcf (trillion cubic feet) 1 Tcf ~ 1 quadrillion Btu (quad) World energy use (2000): about Quad = 500 Tcf hydrate gas per year US gas hydrates: estimated at about 100,000 to 600,000 Tcf Gas hydrates abundant in oil-poor countries (Japan, India) VERY MUCH !

Why are CH4 Hydrates a good energy resource
The gas is held in a crystal structure, therefore gas molecules are more densely packed than in conventional or other unconventional gas traps. Hydrate forms as cement in the pore spaces of sediment and has the capacity to fill sediment pore space and reduce permeability. CH4 - hydrate-cemented strata thereby act as seals for trapped free gas Production of gas from hydrate-sealed traps may be an easy way to extract hydrate gas because the reduction of pressure caused by production can initiate a breakdown of hydrates and a recharging of the trap with gas

A Proposed Method For the gas production from hydrates and the seabed stability after the production, we proposed a new concept. The figure illustrates the molecular mining method by means of CO2 injection in order to extract CH4 from gas hydrate reservoirs. The concept is composed of three steps as follows; 1) injection of hot sea water into the hydrate layer to dissociate the hydrates, 2) produce gas from the hydrate, 3) inject CO2 to form carbon dioxide hydrate with residual water to hold the sea bed stable

CH4 Hydrates and Climate Change
Methane is a very effective greenhouse gas. It is ten times more potent than carbon dioxide. There is increasing evidence that points to the periodic massive release of methane into the atmosphere over geological timescales. Are these enormous releases of methane a cause or an effect of global climate change?

Global warming may cause hydrate destabilization through a rise in ocean bottom water temperatures. The increased methane content in the atmosphere in turn would be expected to accelerate warming, causing further dissociation, potentially resulting in run away global warming. Sea level rise, however, during warm periods may act to stabilize hydrates by increasing hydrostatic pressure, thereby acting as a check on warming. Hydrate dissociation may act as a check on glaciations, whereby reduced sea levels may cause seafloor hydrate dissociation, releasing methane and warming the climate.

CH4 Hydrates and the Atmosphere
An important aspect of methane hydrates and their affect on climate change is their potential to enter the atmosphere Methane concentration in seawater is observed to decrease by 98% between a depth of 300m and the sea surface as a result of microbial oxidation. The flux of methane into the atmosphere is thus lowered 50-fold (Mienert et al., 1998) However during catastrophic events such as large–scale sediment slumping much higher proportions of methane would be released.

The Future of Methane Hydrates
Worldwide gas production in the next years Areas with unique economic and/or political motivations could see substantial production within 5-10 years We need to better understand the mechanisms of hydrate disassociation and its role in global warming, either as an accelerator or and inhibitor

Carbon Capture and Sequestration

Carbon Dioxide Emission: 24 billion tons per year
86% of global primary energy consumption is fossil fuels (coal, petroleum oil and natural gas).

CARBON CAPTURE AND STORAGE
Carbon capture and storage is mostly used to describe methods for removing CO2 emissions from large stationary sources, such as electricity generation and some industrial processes, and storing it away from the atmosphere.

Carbon Capture Technology
Post- combustion capture React the flue gas with chemicals that absorb CO2 and then heat the chemicals to release CO2. NOTE: Flue gas : Mixture of nitrogen , water vapor and 15 % of Carbon dioxide .

Pre- combustion capture Remove carbon before combustion. By gasifying the coal through the reaction with more oxygen, it is possible to a mix of mostly CO2 and hydrogen.

Oxy-fuel combustion Use pure oxygen to support the fossil fuel combustion. The flue gas is then mostly CO2 and water making it to separate easily. NOTE: But extracting oxygen from air is very expensive and consumes energy and combustion with pure oxygen occur at higher temperature.

Transportation Many point sources of captured CO2 would not be close to geological or oceanic storage facilities. In these cases, transportation would be required. The main form of transportation pipeline. Shipping The main complication with CO2 transport is that CO2 behaves differently under varying pressures and temperatures and therefore transport of CO2 must be carefully controlled to prevent solidification and blockages occurring. Pipelines would require a new regulatory regime to ensure that proper materials are used (CO2 combined with water, for instance, is highly corrosive to some pipeline materials) and that monitoring for leaks and health and safety measures are adequate. However, these are all technically possible, and pipelines in general currently operate in a mature market.

CO2 storage Various forms have been conceived for permanent storage of CO2. These forms include gaseous storage in various deep geological formations (including saline formations and exhausted gas fields), liquid storage in the ocean, and solid storage by reaction of CO2 with metal oxides to produce stable carbonates

Carbon Storage technology
Geological storage Oceanic storage After we collect and transport all that carbon dioxide (CO2), we're going to need somewhere to put it. There are two places we've found to store CO2 -- underground and underwater. In fact, estimates project that the planet can store up to 10 trillion tons of carbon dioxide. This would allow 100 years of storage of all human-created emissions

Geological storage Geological storage can take place in oil and gas reserves, deep saline aquifers and unminable coal beds. The injection of CO2 at pressure into these formations, generally at depths greater than 800m, means that the CO2 remains a liquid and displaces liquids, such as oil or water, that are present in the pores of the rock. Researchers have found that when they inject CO2 into basalt, it eventually turns into limestone -- essentially converting to rock.

Oceanic Storage Two storage mechanism has been proposed
Dissolving CO2 at mid-depth. Injecting the CO2 at depths in excess of 3 km , where it would form lakes of liquid CO2 . Bellow 3 km liquid CO2 would be denser than sea water and would sink to the ocean floor. In addition to underground storage, we're also looking at the ocean for permanent CO2 storage. Some experts claim that we can safely dump CO2 directly into the ocean -- provided we release it at depths greater than 11,482 feet (3500 meters). At these depths, they think the CO2 will compress to a slushy material that will fall to the ocean's floor. Ocean carbon storage is largely untested, and there are many concerns about the safety of marine life and the possibility that the carbon dioxide would eventually make its way back into the environment.

Carbon Storage Concerns
CCS technologies actually require a lot of energy to implement and run transporting captured CO2 by truck or ship, require fuel. Creating a CCS-enabled power plant also requires a lot of money. What happens if the carbon dioxide leaks out underground? We can't really answer this question. Because the process is so new, we don't know its long-term effects. Slow leakage would lead to climate changing. Sudden catastrophic leakage is dangerous, and causes asphyxiation. The more CO2 an ocean surface absorbs, the more acidic it becomes, higher water acidity adversely affects marine life.

What might Carbon Capture and Storage look like?
Methane gas (also called natural gas) is produced from offshore gas fields, and is brought onshore by pipeline. Using existing oil-refinery technology, the gas is 'reformed' into hydrogen and CO2. The CO2 is then separated by a newly-designed membrane, and sent offshore, using a corrosion-resistant pipeline. The CO2 goes to an oilfield, which is near to the end of its normal life of oil production. But, like many fields, more than 30% of the oil is still un-produced. The CO2 makes the remaining oil easier to produce - partly paying for the operation. The CO2 is stored in the oilfield, several km below sea level, instead of being vented into the atmosphere from the power station. The diagram is from a BP news release from the abandoned Miller project, UK North Sea, which is no longer available online.

FutureGen FutureGen is a public-private partnership to build a first-of-its-kind coal-fueled, near-zero emissions power plant. It will use cutting-edge technologies to generate electricity while capturing and permanently storing carbon dioxide deep beneath the earth. The plant will also produce hydrogen and byproducts for possible use by other Proposed site :Mattoon, Illinois The Mattoon Site consists of 444 acres in Mattoon Township, Coles County, Illinois. Most of the site is currently used for agricultural purposes. The site has rail access immediately adjacent to the northeast site boundary, and has adjacent 138 kV power lines and a 345 kV substation 16 miles away. The site proposers intend to use the combined effluent from the municipal wastewater treatment plants in Mattoon, Illinois and Charleston, Illinois for cooling water. A natural gas pipeline is less than one-half mile away. The CO2 injection well for the Mattoon site is proposed to be on the site, therefore, no CO2 corridor is necessary. Time line :The FutureGen Industrial Alliance plans an aggressive development schedule that includes beginning construction in 2009 and initiating full-scale plant operations in 2012.

HYDROGEN the "forever fuel" that we can never run out of
Water + energy hydrogen + oxygen Hydrogen oxygen water + energy

Why is hydrogen so important?
Hydrogen is ~75% of the known universe On earth, it’s not an energy source like oil or coal Only an energy carrier like electricity or gasoline — a form of energy, derived from a source, that can be moved around The most versatile energy carrier - Can be made from any source and used for any service - Readily stored in large amounts

Sources of Hydrogen Sources that Hydrogen can be extracted from:
Natural Gas, Water, Coal, Gasoline, Methanol, Biomass Other sources being researched include the uses of solar energy, photosynthesis, decomposition, and fuel cells themselves can tri-generate electricity, heat, and hydrogen.

Is it safe?: A primer on Hydrogen safety
All fuels are hazardous, but… Hydrogen is comparably or less so, but different: Clear flame can’t sear you at a distance; no smoke Hard to make explode; can’t explode in free air; burns first 22× less explosive power Rises, doesn’t puddle Hindenburg myth (1937) – nobody was killed by hydrogen fire Completely unrelated to hydrogen bombs

Where Does Hydrogen Come From?
currently most energy efficient Steam Reforming Fossil Fuels requires improvements Partial Oxidation not cost effective Electrolysis Water requires high temperatures Thermochemical requires improvements Gasification Biomass Microbial slow kinetics 95% of hydrogen is currently produced by steam reforming

Hydrogen carries energy
Most of the energy we use today—94% comes from fossil fuels… Fossil fuels are oil, coal, and natural gas and have developed over thousands of years from decomposing prehistoric plants and animals…since these plants and animals no longer exist, making new fossil fuels cannot happen. Only 6% of the energy we use comes from renewable energy sources… But people want to use more renewable energy. It is usually cleaner and can be replenished in a short period of time compared to fossil fuels. The problem is that renewable energy sources—like solar and wind—can’t produce energy all the time… The sun doesn’t always shine. The wind doesn’t always blow. Sometimes the sun and wind provide more energy than we need at that moment. Hydrogen can store and carry the energy until it’s needed and can be moved to where it’s needed.

Why are Energy Carriers good?
Every day, we use more energy, mostly coal, to make electricity. Electricity is an energy carrier. Energy carriers can store, move, and deliver energy to consumers. We convert energy source like coal and natural gas to electricity because it is easier for us to move and use. Electricity gives us light, heat, hot water, cold food, TVs, and computers. Life would be really hard if we had to burn the coal, split the atoms, or build our own dams. Energy carriers make life easier. Hydrogen is an energy carrier like electricity. It can be used in places where it’s hard to use electricity. Electricity requires wires and poles, like you see along the highway and in your neighborhood, to be delivered to a home. Hydrogen can be shipped by a pipeline or produced at the home directly.

How does Hydrogen turn into useable Electricity?
Hydrogen cannot directly make the lights turn on, the water run, or the heat work. It must be converted into electricity. This happens in a fuel cell. The only waste product is water Fuel Cells combine hydrogen gas with oxygen. A catalytic reaction separates an electron—electric power—from the hydrogen molecule; the by-products are water and heat….. This is a real live fuel cell

Uses for Hydrogen Energy
NASA uses hydrogen as an energy carrier; it has used hydrogen for years in the space program. Hydrogen fuel lifts the space shuttle into orbit. Hydrogen fuel cells power the shuttle’s electrical systems. The only by-product is pure water, which the crew uses as drinking water. Hydrogen fuel cells are very efficient, but expensive to build. Small fuel cells can power electric cars. An engine that burns pure hydrogen produces almost no pollution. It will probably be many years, though, before you can walk into a car dealer and drive away in a hydrogen-powered car.

HYDROGEN IN TRANSPORTATION

Options for Storing Hydrogen Today

HYDROGEN STORAGE OPTIONS
PHYSICAL STORAGE Molecular H2 REVERSIBLE COMPRESSED GAS HYBRID TANKS LIQUID HYDROGEN

Compressed Storage Prototype vehicle tanks developed
Efficient high-volume manufacturing processes needed Less expensive materials desired carbon fiber binder Evaluation of engineering factors related to safety required understanding of failure processes

Liquid Storage Prototype vehicle tanks developed Reduced mass and especially volume needed Reduced cost and development of high-volume production processes needed Extend dormancy (time to start of “boil off” loss) without increasing cost, mass, volume Improve energy efficiency of liquefaction

Hybrid Physical Storage
Compressed cryogenic temperatures H2 density increases at lower temperatures further density increase possible through use of adsorbents – opportunity for new materials The best of both worlds, or the worst ?? Concepts under development

HYDROGEN STORAGE OPTIONS
PHYSICAL STORAGE Molecular H2 CHEMICAL STORAGE Dissociative H2  2 H REVERSIBLE REVERSIBLE NON-REVERSIBLE REFORMED FUEL HYDROLYZED FUEL DECOMPOSED FUEL COMPRESSED GAS HYBRID TANKS LIQUID HYDROGEN CONVENTIONAL METAL HYDRIDES COMPLEX METAL HYDRIDES LIGHT ELEMENT SYSTEMS

Non-reversible On-board Storage
On-board reforming of fuels has been rejected as a source of hydrogen because of packaging and cost energy station reforming to provide compressed hydrogen is still a viable option Hydrolysis hydrides suffer from high heat rejection on-board and large energy requirements for recycle On-board decomposition of specialty fuels is a real option need desirable recycle process engineering for minimum cost and ease of use

Reversible On-board Storage
Reversible, solid state, on-board storage is the ultimate goal for automotive applications Accurate, fast computational techniques needed to scan new formulations and new classes of hydrides Thermodynamics of hydride systems can be “tuned” to improve system performance storage capacity temperature of hydrogen release kinetics/speed of hydrogen refueling Catalysts and additives may also improve storage characteristics

The Future of Hydrogen Before hydrogen becomes a significant fuel energy picture, many new systems must be built. We will need systems to make hydrogen, store it, and move it. We will need pipelines and economical fuel cells. And consumers will need the technology and the education to use it.

Green energy Physics Unit 5.

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