Study Guide Chapter 18

“If the United States wants to save a lot of oil and money and increase national security, there are two simple ways to do it: stop driving Petropigs and stop living in energy sieves.” Amory Lovins

Energy efficiency  what is it and how can it save both resources & money? Energy efficiency  the % of total energy input that does useful work How can it save resources?  if you waste less, you use less. How can it save money? $570,000 per minute is wasted in U.S. due to energy inefficiency Using electricity of heating is one of the most wasteful uses of energy

Life cycle costs – what does it mean? How can long term energy efficiency offset the high initial purchase price of energy efficient products? Life cycle costs  initial costs + lifetime operating costs How is the initial high price offset? Saving money in the long run Ex: superinsulated house = 5% more  $300,000 house x.05 = $15,000 so the house costs $315,000. But the total costs for the “life” of the house will be $50,000-$100,000 less because of reduced heating costs.

How does the net energy of a source relate to the number of steps for processing the energy? Which law of thermodynamics does that resemble? Net energy  the total useful energy available from the resource over its lifetime minus the amount of energy used, automatically wasted and unnecessarily wasted in finding, processing, concentrating, and transporting it to users. Relation to # of steps  the more steps, the more energy goes in so that the NET energy goes down. Ex: nuclear energy is pretty low because of the trouble it takes to extract, process, convert it + build, run & decommission the plants & store the wastes. Example: oil is found, pumped from the ground, refined, transported, then burned 2 nd Law of Thermodynamics It takes energy to get energy; every time we use energy, some of it gets degraded as heat

How does the “negawatt revolution” save energy? Negawatt revolution  demand-side management companies encourage customers NOT to use energy. Cash rebates, free energy audits, loans for weatherization How does it save E? Customers use less energy (mainly electricity) so companies don’t have to supply it OR build new plants because the demand is low.

What are some of the more fuel efficient technologies that we buy and use? Fuel efficient technologies  Electric cars reduce our dependence on oil (but cause “elsewhere pollution”) Trains and ships vs. trucks and planes Aerodynamic design, radial tires Fluorescent light bulbs

What kinds of thermal mass can be used in passive solar systems? Thermal mass  the ability to store heat in walls and floors by substances such as concrete, adobe, brick, stone, salt-treated lumber, used tires + dirt. Used in passive solar  collects sunlight shining through and maintains it so that it can slowly be released.

Terms and Definitions: Solar Heating Systems Active: moves water or air with pumps and blowers Passive: moves water or air with natural convection currents or gravity

Active or passive?

Active or Passive?

Active or passive?

How are passive and active solar energy systems for solar heating different? The same? Similarities  both collect the sun’s energy, both of initial costs but pay themselves back, quick to install, no CO2, low env. Degradation Differences  active involves fan or pump as well. Moderate net E (active) vs. High net E (passive), built into structures (passive), mounted on top (active), active is more $$ because of material and replacement costs

How can earthtubes be used to cool? Earthtubes  PVC pipes are inserted into the ground (3-6 m)used for indoor cooling Cooling?  the ground stays cool and cool air enters the house (like an open window almost).

Earthtubes

Solar thermal systems Solar power towers use HELIOSTATS to focus sunlight on a CENTRAL HEAT-COLLECTION TOWER. In solar thermal plants, sunlight is focused on OIL-FILLED PIPES, PARABOLIC DISH COLLECTORS and NON-IMAGING OPTICAL SOLAR CONCENTRATORS capture and intensify sunlight.

The Solar-trough Collector

Power Tower

Solar Dish Engine System

How do photovoltaic cells work? Photovoltaic cells  convert sunlight striking silicon atoms into a flow of electrons. Many cells (sheets of silicon wafers) must be wired together.

How does a turbine generate electricity? What can be used to turn a turbine (which traditional/nonrenewable and renewable sources)? Turbines generate electricity  the turbine spins, which spins a magnet within metal. Electrons from the metal atoms are affected by the magnet and are harnessed. Nonrenewables that turn  steam from boiling water, that was boiled by burning: coal, oil, natural gas or nuclear fission Renewables that turn  falling water, wind, tides, water boiled by the sun, burning biomass/fuel/gas

What are some of the associated problems with hydroelectric dams? Problems  will flood farmland, factory areas, displace people and animals from their homes, increase pollution of water, trigger landslides & earthquakes; destruction of habitats

What is biomass? How is it used to produce electricity? Biomass  organic matter in plants produced through photosynthesis Production of electricity  burned directly or converted into biofuels or biogas and then burned…boil water to produce steam to spin turbines to make electricity.

Which of the renewable sources of energy directly use solar energy? How do the others indirectly use solar energy? Remember, 99% of the energy used to heat the earth comes from the sun Wind Hydropower (falling or flowing) Biomass (photosynthesis) Hydrogen can be split from water by using solar energy as the energy source for electricity first.

Renewable-energy Use in the United States