Energy Sustainability Notes

Energy conservation and efficiency are the most cost-effective and environmentally friendly ways to maximize energy resources.
- Energy conservation: Finding and implementing ways to use less energy.
- Energy efficiency: Using technology to require less energy for the same service.
Tiered rate system: A billing system where customers pay higher rates as their energy usage increases.
Peak demand: The greatest quantity of energy used at any one time.

Sustainable design improves the efficiency of buildings and communities.
Energy-efficient homes utilize proper solar orientation and insulated windows, walls, and floors.
In the Northern Hemisphere, a southern exposure maximizes direct sunlight in winter.
Passive solar design: Construction designed to take advantage of solar radiation without active technology.
Thermal mass: A property of a building material that allows it to maintain heat or cold.
Passive solar energy use can lower electricity bills without mechanical devices.
Building with south-facing windows exemplifies passive solar design.
Roof overhangs utilize seasonal changes in the Sun’s position to reduce energy demand for heating and cooling.
- In winter, low sun shines directly into windows, heating the house.
- In summer, high sun is blocked by overhangs, keeping the room cool.
High-efficiency windows and materials with high thermal inertia are also components of passive solar design.

Renewable energy is either potentially renewable or non-depletable.
- Potentially renewable: An energy source that can be regenerated indefinitely if not overharvested.
- Non-depletable: An energy source that cannot be used up.
- Renewable energy: An energy source that is either potentially renewable or non-depletable.
Renewable energy sources account for approximately 13% of global energy use.
In the United States, only about 7% of energy comes from renewable sources.
Composition of renewable energy:
- Hydroelectric: 15 %
- Solar, wind, geothermal: 8 %
- Combustible renewables and waste: 77 %

Biomass includes waste, agricultural residues (straw, palm kernel shell, corn and cotton stover, bagasse), wood (round wood, chips, saw dust, bark, forest residues), recycled paper (old corrugated containers, office waste, newspaper) ,and energy crops (short rotation coppice, switchgrass, Algae).

Biofuel: Liquid fuel created from processed or refined biomass.
Modern carbon: Carbon in biomass that was recently in the atmosphere.
Fossil carbon: Carbon in fossil fuels.
Carbon neutral: An activity that does not change atmospheric $CO_2$ concentrations.

Wood, charcoal, and manure are used to heat homes worldwide.
In the developing world, people often cannot afford or access fossil fuels.
Net removal: The process of removing more than is replaced by growth, typically referring to carbon.
Use of wood is unsustainable if forest growth does not keep up with forest use.
Charcoal is lighter than wood, contains twice the energy per unit of weight, and produces less smoke.
In regions where wood is scarce, dried animal manure is used for indoor heating and cooking, causing indoor air pollution.

Liquid biofuels can substitute for gasoline and diesel.
Ethanol: Alcohol made by converting starches and sugar from plant material into alcohol and $CO_2$ .
Biodiesel: A diesel substitute produced by extracting and chemically altering oil from plants.
Flex-fuel vehicle: A vehicle that runs on either gasoline or a gasoline/ethanol mixture.
Algae can be used as biofuel.

The kinetic energy of water can generate electricity.
Hydroelectricity: Electricity generated by the kinetic energy of moving water.
Run-of-the-river: Hydroelectricity generation with little or no water retained behind a dam.
Water impoundment: The storage of water in a reservoir behind a dam.
Tidal energy: Energy from the movement of water driven by the gravitational pull of the moon.
Water impoundment allows for on-demand electricity generation by controlling water flow.

Hydroelectric projects bring renewable energy to rural residents worldwide.
Hydroelectricity does not create air pollution, waste products, or $CO_2$ emissions.
However, electricity generated from hydroelectricity can be very expensive.
Reservoirs create recreational opportunities.
Negative environmental consequences include:
- Flooding agricultural land or places of archeological significance, forcing relocation.
- Impounding rivers can interfere with organisms dependent on free-flowing rivers.
- Downstream ecosystems are affected.
- Siltation: The accumulation of sediment (primarily silt) on the bottom of a reservoir.