GSC 1620 Chapter 15

Energy Resources – Alternatives to the Fossil Fuels

Alternative Energies Recall from the previous chapter that the

U.S. derives approximately 82% of the energy it consumes via fossil fuel combustion

The world energy production by source is very similar (see slides)

U.S. Energy Consumption Profile (2012) Oil ~36.5% Natural Gas ~27.3% Coal ~18.3% Nuclear ~8.5% Biomass ~4.5% Hydroelectric ~2.8% Wind ~1.4% Solar ~0.25% Geothermal ~0.12%

TraditionalFossil Fuels (~82%)

Renewable Fuels (9.0%)

Source: U.S. Department of Energy statistics

World energyproduction bysource, 2008

Fossil fuelcontributionequals 84.4%

Alternative Energies Uncertainties, political and natural, about the

future supply of fossil fuels, especially oil, has renewed interest in the development of fossil fuel alternative energies

Fossil fuel alternatives will likely supply a greater proportion of future world energy needs, especially since the world demand for energy is projected to increase substantially (see slide)

International Energy Outlook, 2008

Alternative Energies Although the U.S. and world total reliance

on fossil fuels is quite similar, not all countries are as dependent upon the fossil fuels as the U.S. (see slide)

2009

Alternative Energies Remember, the fossil fuels, especially oil, are

easily transported, “flexible” (multi-use) fuels The challenge facing proponents of alternative

energies in the U.S. is the development of competitively priced alternative energies suitable to meet the country’s nonuniform energy needs (see slide)

1999

Alternative Energies

Alternative energies consist of renewable (e.g., wind, solar) and nonrenewable (e.g., nuclear fission) forms

We’ll discuss those that are currently making the biggest contribution in the U.S. and worldwide

U.S., 2011

Alternative Energies (Nuclear Fission) In the U.S., alternative energies to the fossil

fuels currently contribute approximately 18% to the U.S. energy consumption profile

The most commonly employed fossil fuel alternative energies in the U.S. include nuclear power, biomass and hydroelectric power with very minor contributions from geothermal, solar and wind power

Alternative Energies (Nuclear Fission) Conventional nuclear reactors generate electricity

via fission (splitting) of radioactive uranium atoms (U-235)

Radioactivity - spontaneous transformation of a mechanically unstable atom structure that results in production of heat, nuclear radiation, and one or more new elements with a lower atomic mass than the original radioactive atoms (see figure, animation and demonstration)

Example of Radioactive Decay

http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/radioactivedecay.htm

Nuclear Fission

+ heat and nuclear radiation

Alternative Energies (Nuclear Fission) Nuclear radiation - portions of the original atom

structure mass cast outward at various speeds. Why is exposure to nuclear radiation something we should minimize?

Conventional nuclear power plants harness the heat generated from a controlled splitting of the uranium atoms to boil water; the boiled water is flashed to steam and the steam used to turn electrical turbine blades

Nuclear Reactor Schematic

Alternative Energies (Nuclear Fission) Ongoing nuclear fission depletes the

available uranium atoms necessary to sustain an adequate level of heat generation, therefore the “spent” (depleted) uranium fuel rods need to be periodically replaced

Remember: nuclear fission power only produces electricity

Alternative Energies (Nuclear Fission)

The U.S. currently hosts 104 nuclear power plants - about 25% of the world total (see figure) and in 2006 these plants generated about 20% of the nation’s electricity; 20.2% in 2009

New, traditional nuclear power plants cost about8 billion dollars and at least five years to build

Alternative Energies (Nuclear Fission) In addition, if the U.S. quadruples its nuclear fission

power capabilities its known reserves of U-235 would be significantly depleted by 2020! This increase would still supply less than 25% of U.S. projected energy needs.

Is nuclear fission power the sole solution to our future energy supply problems?

The uranium supply issue could be partially addressed by the reprocessing of depleted uranium fuel rods to extract and concentrate their remaining uranium and the building of “breeder” reactors that generate additional fuel (see slide)

Plutonium: 0.5 grams,ingested or inhaled,can cause death.

No “breeder” reactors operatein the U.S., onlya few operativeworldwide.

Nuclear Energy Safety Concerns Many people don’t support

increased nuclear fission power development because of safety concerns, including:

1) Core meltdown: may result from loss of reactor core coolant water or power surge to reactor – fuel and core materials deteriorate into a molten mass that may rupture the containment building and release high levels of radiation (e.g., Chernobyl, Ukraine 1986, Fukushima, Japan 2011)

Three Mile Island Nuclear Power Plant, PA

Nuclear Energy Safety Concerns

2) Fuel handling: safety of uranium miners and fuel processors; possible theft of transported fuel or stored waste to create a “radioactive dirty bomb”

FOXNews.com

Nuclear Energy Safety Concerns 3) Uranium mine waste: mine tailings

slightly enriched in radioactive material can be a source of air, soil, surface and groundwater contamination; uranium mine tailings were erroneously used in construction aggregate (Grand Junction, Colorado)

Nuclear Energy Safety Concerns 4) Radioactive waste storage: no permanent solution

to this problem for commercial facilities; currently highly radioactive waste is stored at each nuclear power plant

5) Decommissioning of old (see figure) nuclear power plants: nuclear power plants have a 35-50 year life expectancy – What should be done with the structurally weakened and radioactive plant construction materials?

Costs of decommissioning a power plant may exceed $200 million per facility

World, 2011

Nuclear Energy Safety Concerns 6) Terrorist sabotage of nuclear power

plant resulting in massive radiation release or theft of bomb-grade nuclear waste

Note: a nuclear power plant can’t be made to explode like a nuclear bomb

Nuclear Energy Safety Concerns 7) The high numbers (dozens) of

Chernobyl-style reactors in Eastern Europe: Russian designed reactors have a graphite core (no water surrounding the fuel rods) and a limited containment building – if a malfunction occurs the fuel rods and core can fuse into a molten mass that is more likely to produce a core meltdown

All of these safety concerns have increased in Eastern Europe since the breakup of the USSR. Why? 2010

Alternative Energies (Nuclear Fission

Possible future course of nuclear power? Use thorium, not U-235 as the basic fuel

Thorium is more abundant and is more difficult to manipulate into bomb-grade material (see figure)

Source: Geotimes: June, 2008

Alternative Energies (Nuclear Fusion) Know the difference between nuclear

fission and nuclear fusion Nuclear fusion - combination of atomic

structures accompanied by the production of one or more new elements and the release of tremendous energy with virtually no radiation

Alternative Energies (Nuclear Fusion)

Nuclear fusion is the process of matter conversion that happens in the core of stars (like the Sun) at temperatures approaching 20-30 million degrees C and pressures about 250-300 billion times greater than Earth’s atmosphere

Example: 11 H + 1

1 H + 11 H +

11 H---> 4

2He + tremendous energy + 2 e+ (positrons)

Our Sun

Alternative Energies (Nuclear Fusion) Nuclear fusion power is often viewed as a

panacea, however, we haven’t been able to economically recreate the necessary conditions for more than a few milliseconds!

Regardless, the U.S. and other nations are still investigating nuclear fusion power

Alternative Energies (Hydroelectric Power) Future significant (> 2-3 x current

capacity) increases in hydroelectric power (using dammed waters to generate electricity) output in the U.S. unlikely - most rivers capable of generating significant electricity are already dammed. Dams also require periodic dredging and have the potential for catastrophic failure (see figures)

Geotimes: May, 2008

Benefits and disadvantages of dam construction?Global climate change consequences for western U.S. dams?

Alternative Energies (Hydroelectric Power) Obviously then hydropower production is a

site-specific resource concentrated where streamflow is plentiful (see slide) and its generating capacity is threatened by drought

There’s also considerable public support west of the Mississippi for dam demolition (see figure). Why?

Approximately80,000 large dams(> 7.6 meters high)exist in the U.S.

Alternative Energies (Geothermal Power) Geothermal energy is also used to generate electricity A conventional geothermal site overlies a subsurface

body of cooling molten material where water in a porous and permeable rock, overlain by impermeable material, is heated (see figure); geothermal sites produce high-temperature steam, hot waters or both

The steam or high-temperature waters (flashed to steam) can be used to turn electric turbine blades and generate electricity

Alternative Energies (Geothermal Power) Unfortunately, most of the world’s

geothermal sites are associated with divergent (Iceland) or subduction zone (New Zealand) plate tectonics; the site-specific nature of this resource limits its applicability (see slides)

Krafla Geothermal Power Station, Iceland

Alternative Energies (Geothermal Power)

The sites also lose heat with time (15-30 years) if the cold water return outpaces the resupply of subterranean heat and there are limited water pollution concerns from certain dissolved substances in the geothermal waters

Alternative Energies (Solar and Wind) Solar and wind power often touted as free and

nonpolluting but this statement is misleading The large-scale development of solar and wind

power is hampered because: 1) These resources are nonuniformly distributed; 2) These resources are variable in intensity; and 3) The raw resources can’t be effectively stored

(current battery technology is inefficient).

Alternative Energies (Solar Power) Solar power typically employed in “active”

or “passive” systems; passive systems - no motorized equipment necessary; active systems - motorized equipment necessary

Greenhouses and some homes are partially heated by passive solar systems; roof-based, water-filled solar panels used for space heating an example of an active solar system (see figures)

A and B = examplesof passive solarheating

C = example of activeSolar heating

Alternative Energies (Solar Power) Solar energy can also be used to directly

generate electricity via photovoltaic (PV) cells; photo (light), volt (measure of electric energy) - Incident light strikes special semiconductor materials and sets electrons into motion - the flow of electrons is electrical current (see figure)

Schematic of a Photovoltaic Cell

Alternative Energies (Solar Power)

Common applications?

Alternative Energies (Solar Power)

Calculator Landscape Light

Alternative Energies (Solar Power) The best photovoltaic cells are still only

about 20-25% efficient; a large area of panels is required to generate a reasonable amount of electricity

A map of solar energy distribution in the U.S. (see figure) suggests that perhaps only the Southwest could currently cost efficiently develop solar PV electricity

Solar Energy DistributionMap (numbers = watts persquare meter absorbedenergy)

Alternative Energies (Solar Power) Construction of large solar panel arrays would

require significant resources (land, concrete, steel) and the semiconductors contain arsenic and gallium (both toxic)

Solar PV panel efficiency is improving and making this option of electricity generation more viable; photovoltaic applications have also greatly benefited remote regions, especially in poor countries

Photovoltaic roof shingles and roof –mounted cells are now available! (see figures)

Alternative Energies (Solar Power)

A) Photovoltaic panel use in mountainous Alaska B) Photovoltaic panel use in remote U.S. West

A B

photovoltaic roof shingles

roof-mounted photovoltaic cells

Thin-film photovoltaic materials may have numerous future applications – including the solar purse described in the figure to the right!

Source: Associated Press,printed in the Harrisburg Patriot News, 26 December, 2005, pageB3.

Alternative Energies (Solar Power) Solar electricity may also be produced by a

technology called ‘solar thermal energy’ Scan the next three figures to see how this

technology indirectly generates electricity by concentrating solar energy into heat

11/17/05

Wall Street Journal: 11/17/05

Solar Thermal Energy Construction of the world’s

largest solar thermal energy facility, with a capacity to meet the electrical needs of 140,000 homes, was recently finished in California’s Mojave Desert

Total project costs exceeded $2 billion and the project went online in early 2014

Alternative Energies (Wind Power)

The energy (E) of wind varies as a cube of the wind speed; e.g., E = speed3, therefore if the wind speed doubles the wind energy increases by a factor of eight

Alternative Energies (Wind Power) Wind can be used to generate electricity

via wind-driven turbines placed atop windmill type structures (see figure)

Alternative Energies (Wind Power)

Electrical Wind Farm, California

Alternative Energies (Wind Power) The most consistent, highest velocity winds blow

about one mile off the Earth’s surface - Can you imagine constructing one-mile-high windmills?

In flatter, low-elevation areas the turbine needs to be about 250 feet above ground level

Subsequently, the largest current “wind farms” are in high-elevation areas like the mountain pass shown in the previous figure

Alternative Energies (Wind Power) Inspection of a U.S. wind energy

distribution map (see figure) illustrates that only portions of the Northern and Central Plains and mountainous areas could likely make substantial use of this energy type in the near future

US Wind Energy Potential

Alternative Energies (Wind Power)

However, technological improvements are increasing the potential for more wide-scale use of wind power (~ 5 – 10 years in the future)

Wind power is currently the fastest-increasing use alternative energy in the United States

Wind power electricity in some settings can be generated for 4 cents per kilowatt hour – equal to or less than other methods

One Megawatt of wind-generated electricity powers 250-300 averagehomes

Discover Magazine, 2006

The U.S. became the world’s number one producer of windpower in 2008, passed by China in 2010 but reclaimed first in 2012

60,000 MW in 2010

Alternative Energies (Wind Power)

Some nations (e.g., Netherlands, United Kingdom, Canada) are constructing, or planning, offshore marine wind farms – the coastal winds are more energetic and consistent

Potential objections, concerns in the United States?

Netherlands Marine Wind Farm

Alternative Energies (Wind Power)

The Interior Department did approve an offshore wind project (Cape Wind) for Massachusetts in 2010 but opponents are still trying to derail the project.

However, note that the Maine coast was the location of North America’s first offshore wind turbine in 2013.

Alternative Energies (Wind Power)

Recently, Scandia (a Norwegian and Danish conglomerate) has proposed an extensive wind farm about 3-4 miles off the western shore of Lake Michigan

Critics say it will spoil the beauty of the Great Lakes and make the nearshore region look like an industrial park

Alternative Energies (Biomass) Biological Materials (“biomass” – wood, plant residue,

human and animal waste, etc.) can be burned to produce heat and electricity; carbon dioxide is still a product

Biomass can also be converted into biofuels (e.g., ethanol from corn)

Biomass-fueled power plants are rare; more people are turning to wood pellet stoves for indoor heating

Perhaps more promising is the future development of biofuels

Alternative Energies (Biofuels) Much publicity has been devoted to biofuels – fuels

sourced from biological matter (e.g., ethanol produced from corn which mixed with traditional gasoline can power a “flexible fuel” vehicle; biodiesel – soybean residue, fats, other organic waste used to power an engine

Consider: a 2006 study suggested that conversion of the entire U.S. corn crop to ethanol would still only supply enough fuel to satisfy 7% of the energy consumed by U.S. motorized vehicles currently powered by gasoline

Can ethanol be cheaply made from cellulosic sources? (e.g., switch grass)

Energy Consumption Trends Based on what you’ve learned, does it

appear that any one or two fossil fuel alternatives will satisfy the bulk of our nation’s future energy needs?

Energy Consumption Trends The following slide illustrates that the consumption of

electricity in the U.S. is increasing substantially – unfortunately the further the electrical current has to be transferred from the power plant the greater the proportion of energy lost as heat

This is why sources of electrical power (e.g., nuclear power plants) need to be located close to the electricity users

Usually 2/3 of the energy consumed in generating electricity is lost (not delivered as electricity to end user)!

Residential and Commercial Energy Consumptionin the U.S.

Alternative Energies Superconductivity – the transfer of

electrical energy without loss How would the creation of ambient-

temperature superconductors influence the utilization of fossil fuels and their alternatives?

Bonus If we have time, let’s examine fuel cell

technology – many scientists and politicians are touting these sources as a means to reduce our energy supply concerns

If class time isn’t available you can use the following notes as a reference

Alternative Energies (Fuel Cells) Fuel cells – electrochemical devices that convert a

fuel’s chemical energy to electrical energy Fuel cells were first developed in 1839! At least six fuel cell types have been developed; type

implied by President Bush’s 2002 State of the Union address: Proton Exchange Membrane Fuel Cell (PEMFC)

In a PEMFC, the fuel is hydrogen gas, supplied directly or extracted from a hydrocarbon (e.g., methane gas or propane) or an alcohol (e.g., methanol)

Alternative Energies (Fuel Cells) An electrolyte catalyst that blocks electrons is

used to transform hydrogen gas, in the presence of oxygen, to hydronium (hydrogen) ions and electrons

The liberated electrons flow from the cell’s anode to its cathode completing an electric circuit

At the cathode the hydronium ions, electrons and oxygen gaseous ions combine to form water and release heat (see figure)

Fuel Cells Reactions: Anode: 3 H2(g) + O2(g)

2 H3O1+(g) + 2e-

Cathode: 2 H3O1+(g) +

O2-(g) 3 H2O(g) +

heat

H3O1+ = Hydrogen ions

Fuel Cells for Vehicles Development Problems? 1) Source of hydrogen and method of delivery to cell; use

of a Reformer (device that extracts hydrogen from hydrocarbons or alcohols) lowers the cell’s efficiency from ~ 80% to 24-32% (fuel isn’t pure)

2) Development of fuel distribution infrastructure 3) Size and weight of cells necessary to power an

automobile 4) Mechanical effectiveness (e.g., acceleration speed)

compared to gasoline combustion engine 5) Cost competitiveness compared to gasoline engines

Fuel Cells My opinion: prior to large-scale

commercial development of fuel cell vehicles, I think it more likely we’ll see an increase in gasoline/electric hybrid vehicles or electric vehicles (Nissan Leaf, Chevrolet Volt) biodiesel engines and more efficient diesel and gasoline engines

Summary question: does it appear from our review of fossil fuel alternative energies that any one, or even few, alternative energies are currently capable of fully replacing the fossil fuels?