cive230 lec 14 - energy, renewables

major negative environmental byproducts of electricity production from fossil fuels

PM, SO2, NOx

PM mitigation

• Particulates are removed from power plant emissions through the use of Electrostatic Precipitators (ESP)

• The emission gas is bombarded with negative ions as it flows between two positively charged plates. The PM becomes negatively charged and is attracted to the plates at a speed of w (m/s)

SO2 mitigation

• Chemical methods known as scrubbers are used to remove the SO2

  from FFPP emissions. A limestone (CaCO3 ) slurry is sprayed into the

  output flow

• The outputs of this equation are carbon dioxide and gypsum

NOx mitigation

• Oxides of nitrogen from emission gases are converted to Nitrogen through the introduction of ammonia (NH3) and oxygen

nuclear energy

Energy derived from splitting (fission) of specific uranium isotopes ( 92U235 )

how much of extracted material is usable

0.05-0.3%

what is the remainder material (non uranium) extracted from uranium mining

phosphate based rock, used for production of fertilizer

how much uranium does canada produce

22% of global production (2016) - 85% exported, 15% used for reactors in Ontario and New Brunswick

Environmental, Social, and Economic factors of nuclear energy production

environmental

• The only GHG emissions of a Nuclear power plant are from mining the fuel and materials, transportation, etc

• Disposal of spent fuel has associated long term environmental contamination

social

• Disposal of spent fuel has associated long term health risks

• Health risks are associated with plant operations

economic

• Requires too much investment ($7 Billion), construction, permitting time (10 years)

nuclear energy sustainability considerations

• The ability to appropriately judge the “sustainability” of nuclear energy depends on one’s ability to assess risk of environmental damage associated with nuclear operations and disposal over very long periods of time.

• The analysis period for radioactive waste has been estimated at 10,000 to 1,000,000 years by the US National Research Council. Further, the scope of a risk analysis must include large geographic areas, often over national borders

• In order to prevent human exposure to radiation derived from spent nuclear fuels, interim and long term storage facilities must be constructed

• Typically, concrete (approximately 1 m thickness) and water (3 meter thickness) are used to contain spent fuel. A long-term disposal method known as “Deep Geological Disposal” has long been considered as a means to treat nuclear waste.

Chernobyl disaster

• The accident occurred as a result of an unexpected powe surge, causing a reactor vessel to rupture and a series of steam explosions, leading to fire in the reactor.

• When the plant exploded, it released large quantities of radioactive particles into the atmosphere that spread over much of the USSR and Europe.

• The disaster resulted in the evacuation and resettlement of more than 350,000. Although only 31 deaths are directly associated with the accident, one Russian publication estimates that nearly a million premature cancer deaths occurred between 1986 and 2004 were due to radioactive contamination from the reactor fire.

Fukushima Daiichi Nuclear Failure

• Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a nuclear accident on 11 March 2011.

• All three cores largely melted in the first three days – high radioactive release.

• After two weeks the three reactors (units 1-3) were stable with water addition but no proper heat sink for removal of decay heat from fuel. By July they were being cooled with recycled water from the new treatment plant. Reactor temperatures had fallen to below 80ºC at the end of October, and official 'cold shutdown condition' was announced in mid December.

• There have been no deaths or cases of radiation sickness from the nuclear accident, but over 100,000 people had to be evacuated from their homes to ensure this. Government nervousness delays their return.

Acts related to nuclear energy in Canada

• nuclear safety and control act (regulation)

• nuclear energy act (nuclear r&d)

• nuclear fuel waste act (waste)

• nuclear liability and compensation act (liability)

solar energy

• Each solar cell consists of a semi-conducting surface (like silicon dioxide in thin films) to receive the sun’s photons and convert them into electrons of current (the photoelectron effect).

• Electronic circuits are fitted on the back of the cell to carry the electricity away.

• The circuits can be of various designs including flexible plastic substrates (organic electronic devices, thin film technology).

types of solar energy

• solar photovoltaic (PV) - photons strike a semiconductor and generates electrons to produce electric current

• solar thermal - photons strike another fluid or material to heat it (solar to thermal)

potential solar energy in US in 1 year

2000x annual production from coal

Rating of PV system/PV output

Solar PV panels are rated by their theoretical maximum capacity. A 2-kW

PV panel would produce 2 kW of electricity at its maximum output,

which would be during peak solar radiance.

Annual Solar PV Output = Rated capacity x avg. daily peak sun hrs x 365

Environmental, Social, and Economic factors of solar energy production

environmental

• solar power produces essentially no GHG emissions

• use of potentially harmful materials, limits disposal options

social

• land requirement

economic

• unlimited supply of source energy

• high costs of construction and lack of competent storage technology limit economic feasibility

hydro energy

Hydropower is energy in moving water - People have a long history of using the force of water flowing in streams and rivers to produce mechanical energy.

factors for available energy in water

volume of water flow and change in elevation

largest hydroelectric power station

three gorges dam (china)

geothermal energy

• Geothermal energy is the energy stored in the form of heat beneath the earth's surface.

• Requires intense heat or steam and typically is found near active volcanoes and geysers.

geothermal regions

often found near tectonic plate boundaries, volcanic areas, or where Earth’s crust is relatively thin

how does geothermal power work

• Hot water is pumped from deep underground through a well under high pressure

• When the water reaches the surface, the pressure is dropped, which causes the water to turn into steam.

• The steam spins a turbine, which is connected to a generator that produces electricity.

• The steam cools off in a cooling tower and condenses back to water.

• The cooled water is pumped back into the Earth to begin the process again.

geothermal heat pumps

Geothermal heat pumps transfer heat by pumping water or a refrigerant (a special type of fluid) through pipes just below the Earth's surface, where the temperature is a constant 10 to 15°C.

• Water or a refrigerant moves through a loop of pipes.

• When the weather is cold, the water or refrigerant heats up as it travels through the part of the loop that is buried underground.

• Once it gets back above ground, the warmed water or refrigerant transfers heat into the building.

• The water or refrigerant cools down after its heat is transferred. It is pumped back underground where it heats up again.

• In warmer seasons, the system can run in reverse

biomass

• Fuelwood harvesting

• Willows and grass cultivated as fuels

• Waste products from other industries

  • Forest product residues like sawdust, wood chips are burned for electricity

  • Bagasse – waste fiber from sugarcane for heat and electricity

biofuels (ethanol and biodiesel)

• Ethanol obtained by fermentation of corn, wheat, sugarcane and used as a transportation fuel (10% ethanol and 90% gasoline)

• Biodiesel from chemical conversion of fats and vegetable oils used in diesel engines

environmental, social, and economic impacts of biomass and biofuels

environmental

• low GHG emissions

• water footprint and water pollution

social

• land requirement

economic

• impact on crop prices

• economic viability of 1st generation biofuels questionable

• needs subsidies

engineers contribution to energy sustainability

• Designing appropriate technologies based on the needs and available renewable resources and reserves

• Modifying systems to increase the efficiency and reduce the production costs

• Modifying systems to reduce the amount of pollutants generated by a process

• Identifying and capturing pollutants for disposal through a formal waste

  management system

• Treating waste to reduce its impacts before it is disposed of in the open

  environment

• Controlling regulation

fusion energy

• Nuclear Fusion is the process of combining two light atomic nuclei (often isotopes of hydrogen) to form a heavier nucleus releasing energy

• Fusion reactions need to take place in a plasma state of matter requiring temperatures in the millions of degrees Kelvin.

environmental, social, and economic impacts of fusion energy

environmental

• Fusion Fuel is extremely abundant and able to last us for millions of years

• emits no carbon or greenhouse gases

social

• land requirement

economic

• fusion could generate 4x more energy per kg than nuclear, and four million times more than oil or coal

• a 1000 to 1500 MW plant could cost anywhere from 2.7 to 9.7 billion US dollars