Env Sci II

Sustainability

A system or process that can be continued indefinitely without depleting materials or energy resources required to keep it running

What does most of our energy go towards

Most energy usage is ELECTRICITY and HEAT

How do we generate electricity?

• Turbine electricity generator

• kinetic energy - energy in motion

  • harness kinetic energy

  • ex: steam, gas water, etc

Where does most of our energy come from?

80% comes from natural gas, oil, and coal

What are the two key elements of sustainable energy consumption?

Efficiency

• reducing energy lost as waste per unit input

Conservation

• reducing demand for energy

What is cogeneration?

It converts waste heat emitted during electricity production into useful heat

• fuel input → generator → heat recovery (from exhaust, gases, or steam)

What are fossil fuels?

• they are ancient organic material buried underground

  • hundreds of millions of years old

  • burned for energy

• three main types:

  • coal, oil, natural gas

What is coal?

• ancient plants (300 mya) compressed into sedimentary rock laters by heat and pressure

• extracted via mining

• to make coal, plants must not have decomposed quickly, how?

  • nutrients stored in plants but now decomposing fast enough

  • carboniferous conditions were great for plants, not good for decomposing

• U.S. has the most coal reserves

• coal was the first fossil fuel to emerge around the 1850s

What is oil and natural gas?

• ancient marine organisms buried in the ocean floor and compressed by heat and pressure

• gas and oil deposits form together, ration depends on the type of organic material and conditions

• highly concentrated in petro states: along Arabian peninsula, Venezeula, etc

  • their economies depend on oil

What is fracking?

• fluid blasted deep into the earth

• pipe drilled horizontally to make more contact with rock

• fractures in the earth let gas flow into the pipe

• potential for fracking to cause instability and lead to earthquakes, sinkholes, and leakages

How is nuclear energy made?

• unstable nucleus

• unstable atom, add more unstable parts until it breaks apart and creates a lot of energy

• fission chain reaction

  • what makes nuclear so powerful

• fuel rod: made of enriched uranium

• control rod: moderate pace of the reaction

how does nuclear energy work?

• harness energy produced by fission reaction to generate steam and power a generator

• powerful, versatile, and reliable

  • high capacity factor

• clean (essentially no carbon emissions)

• has the highest capacity factor

what is a capacity factor?

Capacity factor is a measure of how often a power plant runs at full capacity

What are the cons of nuclear energy

• safety

  • ex: 3 Mile Island and Charnobyl

• cost

  • cost has increased over time

  • high cost in terms of up front investments

• waste

  • a lot of nuclear waste

What is risk?

• the probability of a hazard causing harm, account for likelihood of occurrence and vulnerability of subject

• Risk = Probability of Hazard (for nuclear, this is extremely low) x Vulnerability

What metal is used in nuclear energy?

Uranium

How do we store waste?

• nuclear waste lasts tens of thousands of years

• need to consider

  • environmental impact

  • proximity to people

  • national security

    • by-product can be used in nuclear weapons

• our best solutions (far): bury it in a geological formation FAR AWAY from life

Renewable Energy

• energy sources are replenished at a rate faster than they are depleted

• several (diverse) types:

  • hydropower

  • solar

  • wind

  • biomass

  • geothermal

What is solar energy?

Sunlight hitting metal in a photovoltaic cell cause electrons to be emitted when light is absorbed

Pros of solar energy

• pros:

  • low cost (both initial and recurring)

  • produce little pollution

  • can exist in remote areas

Cons of solar energy

• intermittent energy source

  • duck-curve problem

• space intensive

What is the duck-curve problem?

• not using as much energy during the peak hours of solar energy production

• using the most in the evening, bit in morning, big drop midday

What is hydropower?

Water flows through penstock from high elevation to low elevation, pushing turbine

Pros of hydropower

• stable energy source

• provides freshwater source

Cons of hydropower

• expensive

• interrupts flow of river systems

  • note the salmon canon

• susceptible to droughts

What is Wind Energy

Turbine pushed by wind, kinetic energy of spinning turbines converted to electricity

What is wind?

Cool air over the water moves in → land heats up faster than water → war air over the land rises

Pros of wind energy

• lost cost, especially onshore

• land efficient, especially offshore

• solar and wind energy are cheaper than fossil fuels

Cons of wind energy

• noise and aesthetic makes people rlly mad

• limited to windy places, intermittent

• risk posed to migrating species and marine life

  • only .23 of birds die by wind turbines

  • compared to outdoor cats with 2,400 & building collisions with 599

What is biomass?

organic material burned for fuels

Pros of biomass

• highly available, can make waste productive

• extremely low cost

Cons of biomass

• air pollution source

• carbon neutrality is complicated

What is Geothermal?

Steam generation by pumping water down below earth’s surface

Pros of geothermal

• very stable energy source

• small land footprint

• safe

Cons of geothermal

• expensive

• highly location dependent

• require drilling into the Earth

Future renewables?

• other sources of kinetic energy..

  • earths tides

  • nuclei merging together (nuclear fusion)

    • clean

  • static energy in water vapor

  • seismic activity (earthquakes)

• these solutions don’t scale currently, but may in the future

What are the four ways of measuring energy?

Primary Energy, Secondary Energy, Final Energy, and Useful Energy