Sustainable Energy

Conservation--Still the best plan of action!

Most of our options to oil take a lot ot energy to create and are not nearly as concentrated.

 

Solar:

  • .1% of the electricity in US produced through solar panels.
  • Constant, free energy supply
  • Amount of solar energy reaching the earth's surface is 10,000 times all the commercial energy used each year.
  • Until this century it was too diffuse and low in intensity to use except for environmental heating and photosynthesis.

Passive Solar Heat

Heat homes naturally through absorbing the heat rather than any mechanical heating device. Much of passive solar heat is simply orientating your home toward the sun and having lots of windows.

Indirect gain: Absorption-using natural materials or absorptive structures with no moving parts to simply gather and hold heat.

  • Old Method: Thick-walled stone and adobe dwellings that slowly collect heat during the day and gradually release heat during the night.  After cooling at night, they maintain a comfortable daytime temperatures while still absorbing external warmth.
  • New Method: glass-walled "sunspace" or greenhouse on the south side of a building. Uses massive energy-storing materials such as brick walls, stone floors, or barrels of heat-absorbing water to collect heat to be released at night.

Direct gain: Use a roof overhang that blocks the direct sunlight in the summer, but lets the sun in when its at a lower angle in the winter.

Active Solar Heat

Solar panels- Photovoltaic Cells-capture solar energy and convert it directly to electrical current by separating electrons from their parent atoms and accelerating them across a one-way electrostatic barrier formed by the junction between two different types of semiconductor material. This is known as the photovoltaic effect.

  • They used to be too expensive for practical use but prices are falling.
  • In 2001 prices were approaching $5 per watt.
  • By 2020 it will be down to about $1 per watt and nuclear energy will cost twice as much.
  • World market for solar energy is expected to grow rapidly in the near future, especially in remote places where conventional power isn't available.
  • Already used in watches, solar-powered calculators and toys
  • Solar energy could mean being able to build a house anywhere and have a cheap, reliable, clean, quiet source of energy with no moving parts to wear out, no fuel to purchase, and little equipment to maintain.
  • Can sell electricity back to the "grid" and make money!

Pro:

No pollution, unlimited resource, can store energy during the day and release it at night, cost going down- decreased by a factor of ten in 2 years!

Con:

Needs a storage system like deep cell batteries, not efficient if climate too cloudy or sunlightis limited, high costs for purchasing solar panels and have limited life span, Visual pollution, efficiency between 10 and 25%.

Solar water heaters

Generally pump a heat-absorbing, fluid medium through a relatively small collector instead of passively collecting heat.

  • Can be located next to or on top of buildings.
  • Flat, black surface sealed with a double layer of glass makes a good solar collector.
  • A fan circulates air over the hot surface and into the house through ductwork, like standard forced-air heating.
  • A simple flat panel of 5 square meters can provide enough hot water for an average family of four.
    What about when it's not sunny?
    1. For climates where sunless days are rare- small, insulated water tank makes a good solar energy storage system.
    2.  For winter months-A large, insulated bin containing a heat-storing mass, such as stone, water, clay provides solar energy storage.

 

Fuel Cells:

  • Devices that use an ongoing electrochemical reaction to produce an electric current.
  • Discovered by William Grove in 1839 during his study of electrolysis.
  • Fuel cells consist of a cathode (positive electrode) and an anode (negative electrode) and are separated by an electrolyte.
    • An electrolyte is a material that allows ions (positively charged atoms) to pass through but not electrons.

How a fuel cell works: hydrogen passes over the anode and a catalyst on the anode takes an electron from each hydrogen atom, creating a positive hydrogen ion. The ion can pass through the electrolyte to the cathode, but not the electron. The electron then passes through an  external circuit going into the cathode creating an electrical current. Then, at the cathode the electrons and positive ions rejoin and combine with oxygen creating water.  

Pro:

Emits water as waste! No pollution, minimal environmental impact- considered the cleanest source of energy, easily transported, not explosive when stored in compounds.

Con:

Takes energy to produce hydrogen (more so than the energy produced), changing from fossil fuels to hydrogen would take a lot of money to build the infrastructure, hydrogen gas is explosive which is inconvenient- how could we store it in a car?

 

Biofuels:

Biofuels are produced from burning living organisms. It produces 15% of the world's energy, 4% of that energy is used by the U.S (.1% electricity). 

  • Types of materials biofuels include switchgrass, woodchips, corn, manure, sawdust, wood residue, any kind of wood or plant material. Lately algae has been considered as a smart choice.
  • Biomass plantations would be an effective use of marginal cropland that cant grow much else.
  • Biomass (plants, wood, etc.) converted into a liquid form making storage and transportation easier. Gasohol is 90% gasoline and 10% ethanol

Pro:

  • It is a renewable resource if used in moderation
  • Biofuel could produce 1/2 of the world's electrical needs if managed properly; many marginal areas of the world could support biomass plantations with plants like cottonwoods, populars, sycamores and shrubs
  • Its inexpensive, and the burning of biofuels produce less SOx and NOx then coal.

Con:

  • Deforestation and soil erosion can occur, requires fertilization and water.
  • It is expensive to transport and can cause the loss of wildlife and habitats.
  • Some methods of burning biomass causes air pollution such as CO2 emission. Also the use of corn to produce ethanol takes more energy than it creates and is driving the price of corn up for the poor who depend on it for food (ex. Mexicans). One bushel of corn (about 60 ears) creates 2 1/2 gallons of ethanol.
  • Expensive to transport because heavy.
  • When biofuels are converted to electricity, 70% of the energy is lost!

 

Hydroelectric Power:

  • Dams trap water which is then released and channeled through turbines which generate electricity.
  • 10% of USA's electricity, 3% worldwide.
  • There are 2000 dams in the US.

    Pro:

    • Good because there's no pollution, low operation costs and they control flooding downstream.
    • They also have a high to moderate energy yield and a long life span.
    • Water can be used to irrigate crops.

    Con:

    • Dams create large floods, which uproot people, destroy habitats, and disrupt natural soil fertilization of agricultural land downstream.
    • Sediments eventually need to be dredged from the reservoir because of silt build up.
    • Also dams upset fish migration patterns (salmon!) and the natural beauty of rivers.
    • Dams are extremely expensive to build.
    • Could be destroyed by earthquakes or excessive flooding
    • Can have a lot of water loss through evaporation and seepage through rock beds.

 

Tidal and Wave Energy:

The natural movement of tides spin turbines which generate electricity. Very few plants exist- only in US, France and Scotland.

Pro:

No pollution, moderate energy yield, minimal environmental impact, cheap to maintain.

Con:

      Costs a lot to construct, few suitable sites. Plants get hurt by corrosion from salt and storms.
    

Wind Power:

Large blades of wind mills spin create electricity.

Now makes less than .1% of electricity in US but growing!

Pro:

  • Fastest growing renewable energy resource today- up 30% year
  • No pollution
  • Very promising
  • Unlimited source (quick fact: all electrical needs of the US could be met by wind in North Dakota, South Dakota and Texas!)
  • Wind farms can be built quickly and can be placed on sea platforms.
  • Maintenance is low and automated
  • Moderate to high net-energy yield
  • Production of wind turbines would be a boost to economy
  • Land underneath turbines can be used for agriculture

Con:

  • Initial cost to build it high
  • Steady wind is required to make it economical. Back up systems needed when wind is not blowing
  • Visual Pollution- ugly
  • Noise pollution
  • May interfere with communications (radio, TV, Microwave, cell phones)
  • Might kill some birds if on migrational pattern

Geothermal Power:


Two kinds:

    • Heat contained in underground rocks and and fluids from magma are used to warm home
    • Or just the stable subsurface ground temperature is used to heat air in winter and cool it in summer.
  • Geothermal energy supplies less then 1% of energy needs in the U.S.
  • It is being utilized in Hawaii, Iceland, Japan, Mexico, New Zealand, Russia and California

Pro:

  • Moderate net-energy yield
  • Limitless and reliable source if managed
  • Little air pollution
  • Competitive cost

Con:

  • Reservoir sites for hot geothermal power are scarce
  • Source can be depleted if not managed
  • Drilling is expensive
  • Noisy
  • Odor
  • Land damage involved for pipes and roads- can cause land sinks (subsidence) .
  • Can degrade ecosystems due to hot water wastes and corrosive or saline water

Energy Conservation

CAFE standards: Corporate Average Fuel Economy

The goal of these laws are to increase the fuel economy of cars and light trucks. The goal is to have cars reach 54.5 miles per gallon by 2025 (presently the average is 27.5 mi/gal). This can be done by improving :

  • Engine design
  • Efficiency
  • Weight Reduction

Hybrid electric vehicles

These vehicles combine the usual internal combustion engine with an electric propulsion system. One of the coolest features are regenerative brakes where just the act of braking can charge the car battery!!!

Mass transit

Using buses, subways, ferries, and railroads would reduce our air pollution and gasoline comsumption. The US is woefully low in mass transit use compared to the rest of the world.