Chapter 12: Renewable Energy and Nuclear Power

Nevada's History of Nuclear Energy

Nevada Test Site (1951-1992): Location of 900 nuclear tests.`

Three Mile Island

A 50% meltdown of reactor core caused the most serious reactor accident in US in 1979. The containment building kept radiation from escaping, and no substantial environmental damage nor human casualties occurred. It took 12 years and $1 billion to repair the accident. The event elevated public fear of nuclear energy and led to the cancellation of many new plants in the U.S.

Uranium

A high-energy metallic element that must be mined and enriched to make fuel for nuclear power.

Photovoltaic Solar Cells (Solar Panels) (Active)

A wafer or thin film made of semiconductor materials (computer chips). Sunlight hits cells, electrons are knocked loose from atoms, electrons flow through the cell, generating electricity. No pollution and minimal maintenance, can be used on any scale (i.e. lighted road sign or entire building).

Indirect Solar Sources

All other forms of renewable energy are considered to be indirect solar sources. They use sunlight energy indirectly for their production: biomass, wind, hydropower.

Demand/Cost of Electrical Power

Alternative power sources are becoming competitive with traditional power sources. Some power plant sources are better at generating base load power - constant background power demand. Often nuclear and coal but can be renewable. Peaking power - for high demand times such as afternoon and summer (often natural gas).

Meltdown (Safety Issues in Nuclear Power Plants)

At high temperatures the metal encasing the uranium fuel can melt, releasing radiation. The probability of meltdown is low, but the public perception is that nuclear power isn't safe.

Isotope

Atom where the number of neutrons is greater than the number of protons. It can be stable or unstable in nature.

Active Solar Energy

Collects and absorbs the sun's energy and uses pumps or fans to distribute the collected heat. In a home it can be used to power a hot water heater (8% of energy in the US is used to heat water).

Atom

Composed of: Nucleus: Comprised of protons (+ charge) and neutrons (neutral) and electrons (- charge) orbit around nucleus.

Yucca Mountain, NV

Contains 70,000 tons of high-level radioactive waste from 43 states. Earthquake potential identified. Currently not a viable storage solution.

Biomass

Contains energy from sun via photosynthesizing plants. It includes plant materials, such as wood, crop wastes and animal waste, used as fuel. Oldest known fuel to humans, still used by half the world's population. Renewable when used no faster than it can be produced. Can also be converted to biogas or liquids.

Bioconversion

Conversion of organic materials (plant or animal waste) into usable products or energy sources by biological processes (require microorganisms).

Geothermal Energy Cont.

Most common application uses geothermal heat pumps. Used to heat/cool buildings. Difference in temperature between surface and subsurface -> heat transfer. Expensive installation. For electricity: use steam from naturally-occurring sources.

Hydropower Cons

Ecological disruption (i.e. downstream: sediments at dam, fish migration halted; in reservoirs: flooding, sediment retention, pollution) Disruption of people, loss of cultural resources, risk of failure, high rates of evaporative losses.

Geothermal Energy

Energy from the Earth's interior (magma) is found in hydrothermal reservoirs below ground. Their locations are also seismically active (volcanoes). Geothermal is an enormous energy source. (1% of heat in the upper 6 miles of earth crust is equal to 500X the earth's fossil fuel sources!)

Nuclear Energy

Energy released by either nuclear fission or fusion. Nuclear power plants use nuclear fission, which splits an atomic nucleus into two smaller fragments, releasing a large amount of energy.

Attitudes Towards Nuclear Power

Generally a major case of mistrust on the part of the public towards pro-nuclear power scientists and politicians. (NIMBY) Citizens to not want a nuclear facility or waste disposal site near their home. "Decide, Announce, Defend" (DAD): Pronuclear advocates, based on science, not fear. The driving forces behind public distrust are difficult to resolve.

Hydropower

Hydropower supplies 19% of world's energy as the world's main renewable source of electricity. It is the most efficient energy source (90%). Traditional hydropower is suited only to large dams, but new technology utilizes low flow systems.

Wind Energy Pros

It causes few environmental problems and can kill birds and bats. There is no waste involved, and it is the cleanest form of energy.

Active Solar Cons

It does not work at night without storage (battery). Cloudy weather can make solar energy unreliable during the day although still functional under these conditions. It can be expensive and require a lot of land area.

Nuclear Fusion

Joins two lightweight atomic nuclei into a single, heavier nucleus, releasing a large amount of energy. It takes very high temperatures (millions of degrees) to make atoms fuse. Scientists have yet to be able to create energy from fusion.

Nuclear Energy Pros

Less of an immediate environmental impact compared to fossil fuels. There is low land use, air pollution, climate change risk. It is a carbon-free source of electricity and may be able to generate hydrogen fuel.

Nuclear Energy Cons

Nuclear energy generates radioactive waste and many steps require fossil fuels (mining and waste disposal). It is expensive and has a potential link to nuclear weapons. There is a high risk from catastrophic accidents.

Atomic Number

Number of protons per atom. Each element has its own atomic number. (Carbon=6)

Fukushima Daiichi

On March 11, 2011, a 9.0 magnitude earthquake and ensuing tsunami disrupted power systems that pump cooling water to reactor cores and spent fuel rods. It increased radiation in local water and food supplies. The repercussions could limit seafood catches for decade.

Chernobyl, Ukraine

One or two explosions destroyed the nuclear reactor that released large amounts of radiation into the atmosphere deeming this the worst nuclear accident in history in 1986. Radiation was unpredictable and uneven as it spread across large portions of Europe. Four thousand deaths were attributed to plant explosion, mostly due to cancer.

High-level Radioactive Waste

Primarily spent fuel rods and assemblies. Gives off large amounts of ionizing radiation.

Low-level Radioactive Waste

Produced by power plants, research labs, hospitals and industry. Gives off small amounts of ionizing radiation.

Solar Thermal Electric Generation (Active)

Produces electricity by concentrating the sun's energy by mirrors or lenses and heats a fluid-filled pipe or drives an engine. It is more efficient than other solar technologies because it does not cause air pollution nor contribute to global warming or acid precipitation.

Radioactivity

Radioactive isotopes are unstable and undergo radioactive decay. Energetic particles are emitted over time (i.e. Uranium (U-235) decays over time to Lead (Pb-207) Each isotope decays based on its own half-life, the time required to lose half of atoms. It can range from days (Iodine-131) to thousands of years (Plutonium-239).

Biomass Pros

Reduces dependence on fossil fuels. Often uses waste materials. If trees are planted at the same rate that biomass is combusted, there will not be a net increase in atmospheric CO2.

Tidal Energy

Relies on the ebb/flow of tides to generate electricity. The typical difference between high, low tide is 1-2 feet. Narrow bays may have greater variation Potential energy difference between low and high tide can be captured with: a dam across a bay or a turbine similar to a wind turbine.

Biomass Cons

Requires land, water and fossil fuel energy. It can lead to deforestation, desertification, and soil erosion.

Safety Issues in Nuclear Power Plants

Sites of major nuclear accidents: Three Mile Island, PA Chernobyl, Ukraine ukushima Daiichi, Japan

Active Solar Pros

Solar energy is inexhaustible. It is more economical in rural areas and can be incorporated into building materials such as roofing shingles, tile, window glass.

Hydropower Pros

Source of electrical, mechanical power. Irrigation, navigation, flood control. Recreation: fishing, swimming, boating.

Atominc Mass

Sum of the protons and neutrons in an atom. (Carbon=12)

What to do with high-level radioactive waste?

Temporary storage solutions in nuclear plant facility (require high security), under water storage, above ground concrete and steel casks. Need approved permanent options soon.

Wind Energy Cons

The biggest constraints of wind energy are cost and public resistance (NIMBY or "Not In My Back Yard").

Solar Energy

The sun is a direct source. It is perpetually available and varies with latitude, season, time of day, and cloud cover. It can be used passively or actively.

Nuclear Proliferation

Thirty-one countries use nuclear energy to create electricity. While having nuclear power alone does not provide materials for weapons, these countries have access to materials needed to produce enriched plutonium or uranium for nuclear weapons. Nuclear proliferation, safe storage and handling of weapons is a concern (i.e. Iran: Country of concern)

Nuclear Power: How Electricity is Produced

Uranium is assembled into concentrated fuel rods which are then used to heat water in the core of a nuclear reactor that creates steam. Steam is used to move a turbine and produce electricity. It produces hot waste water that then needs to be cooled, as well as radioactive nuclear waste.

Passive Solar Energy

Uses the sun's energy without requiring mechanical devices to distribute the collected heat. Certain design features can enhance passive solar energy's heating potential of buildings, water. Features: South facing windows (in N. hemisphere), well-insulated buildings, attic vents, overhangs and solar sunspaces.

Wind Energy

Wind results from sun warming the atmosphere, and it is the world's fastest growing source of energy. Wind creates surface air currents and varies in direction and magnitude. New wind turbines harness wind efficiently. It is most profitable in rural areas with constant wind.