Alternative Energies

Active solar energy: photovoltaic cells

converts sunlight into electricity using semiconductor / (typically) silicon semiconductor creates electric field to direct flow of electrons / active solar electrons bump over panels / high initial costs

Active solar energy: solar thermal energy

using a mirror array that focuses light on water to heat up a liquid

Wind energy

turbines convert kinetic energy of wind to create mechanical energy, then it transforms to electricity by a generator / no pollutants / no water usage / bad wildlife impact risk, inconsistent (depends on wind levels)

Geothermal energy

not weather-dependant / uses heat from beneath the Earth / wells drilled to access steam or hot water -> steam drives turbines -> generator -> electricity / low emissions compared to fossil fuels / high upfront cost, location specific, hydrogen sulfide can be released during drilling

Wave and tidal energy

predictable, not consistent / uses kinetic energy and rise and fall of surface waves / oscillating water column captures wave energy through movement of air in chamber (WAVE) / underwater turbine captures energy from tidal currents (TIDAL) / high costs, potential negative environmental impact

Active energy ex.

an array of mirrors using light to heat up water

Passive energy ex.

a roof being built to shade the house interior in the summer, and warm it in the winter

OTEC and earth loops

difference in temperature between ocean/land surface and underneath

Biofuel notes

net increase of CO2 in atmosphere is less than other fuels (not great, but best of worst)

Hydrogen fuel cell notes

electricity splits electrons → reacts with O2 gas to form water → on the way to this reaction electrons create an electric current

Three Gorges Dam

many important cultural sites were lost due to flooding

Mono Lake case study

water diversion in California that affected Mono Lake's ecosystem → court ruled in favor of preserving the lake's levels, highlighting the conflict between water rights and environmental conservation.

Aral Sea case study

environmental disaster caused by excessive irrigation and water diversion → dramatic shrinking of the sea, impacting local ecosystems and economies / 60% of volume lost since 1960