Chapter 13 Achieving Energy Sustainability

What is renewable energy? Renewable energy can be rapidly regenerated, and some can never be depleted, no matter how much of them we use.

How can we use less energy? Energy conservation- finding ways to use less energy. For example, lowering your thermostat during the winter or driving fewer miles. Energy efficiency- getting the same result from using a smaller amount of energy.

Benefits of Conservation and Efficiency Many energy companies have an extra backup source of energy available, usually natural gas fired generators, to meet the peak demand, the greatest quantity of energy used at any one time. Variable price structure- utility customers can pay less to use energy when demand is lowest and more during peak demand. Called tiered rate system.

Sustainable Design Improving the efficiency of the buildings we live and work in.

Passive Solar Energy Using passive solar energy can lower your electricity bill without the need for pumps or other mechanical devices. Building the house with windows along a south-facing wall which allows the Sun’s rays to warm the house would be an example.

Technology An energy efficient house features: -earth tubes: PVC pipes 4-6 in diameter, 3-6 m deep, 2 feet apart (ground is o year round in a northern climate) -deciduous shrubs block sun in summer only -trombe wall (made from thermal mass) -solar collectors for domestic hot water -passive vs active systems (active uses pumps) -payback time is 3-7 years

Appliances 84% of all commercial energy in the US is wasted life cycle cost = initial cost + lifetime operating costs (low in high efficiency appliances)

Inefficient Appliances Incandescent light bulbs Tungsten filament gets “white hot” to give off light. Heat is wasted energy. Switch to CFLs (mercury?), LEDs Internal combustion vehicles Waste heat from engine block, exhaust pipe Nuclear power plants Construction, processing fuel

Energy saving appliances 1) compact fluorescent bulbs, LEDs 2) heat pumps 3) tankless instant water heaters (hot water on demand) 4) high efficiency refrigerators 5) microwave clothes dryer 6) front loading washing machine uses 50% less energy

Biomass is energy from the Sun The Sun is the ultimate source of almost all types of energy

Modern Carbon vs. Fossil Carbon Many people are confused how burning biomass such as wood is better then burning coal. The carbon found in biomass was in the atmosphere as carbon dioxide, taken in by the tree, and by burning it we put it back into the atmosphere Burning coal is carbon that has been buried for millions of years and was out of circulation until we began to use it. This results in a rapid increase in the concentration of carbon dioxide in the atmosphere.

Biomass Wood, Charcoal and Manure- used to heat homes throughout the world. Ethanol and Biodiesel (biofuels)- used as substitutes for gasoline and diesel fuel.

Biomass e.g. trees, agricultural waste, “bagasse”, dung 1. Can be used to produce biofuels a) biogas (60% methane, 40% CO 2 ) b) biogas digesters use anaerobic bacteria 2. Ethanol (from sugar and grain by fermentation and distillation) 3. Gasohol (contains 10-23% ethanol), 4. Ethanol (from natural gas)

The kinetic energy of water can generate electricity Hydroelectricity- electricity generated by the kinetic energy of moving water. This is the second most common form of renewable energy in the world.

Types of hydroelectric power systems Run-of-the-river systems- water is held behind a dam and runs through a channel before returning to the river. Water impoundment- water is stored behind a dam and the gates of the dam are opened and closed controlling the flow of water. Tidal systems- the movement of water is driven by the gravitational pull of the Moon.

Pros 1. Pumped storage hydropower a) stored at night) b) done at Conowingo dam on Susquehanna 2. Controls flooding 3. Less CO 2 4. Long life span a) 2-10 times longer than coal and nuclear 5. Provides irrigation

Cons 1) Construction of new dams flood huge areas a) destroys habitats 2) Displaces people 3) Blocks nutrient flow and siltation downstream 4) Fish harvest is decreased below dam 5) Blocks spawning migration

The Sun’s energy can be captured directly Active solar energy- capturing the energy of sunlight with the use of a pump or photovoltaic cell and generating electricity.

Solar thermal systems (High Temperature) 1) power tower 2) solar thermal plant (oil filled pipes running through parabolic solar collector mirrors) 3) parabolic dish collector 4) solar cookers

Single Solar Cell Boron-enriched silicon Junction Sunlight Cell Phosphorus- enriched silicon DC electricity

Photovoltaic Cells 1. Produces direct current, DC a) appliances use AC 2. Inverter is used to change from DC ---> AC 3. Pros a) lasts years b) low maintenance c) works in cloudy weather d) no CO 2

More Pros 1.currently up 26 cents/kw-hr ---> goal 6-12 cents /kw-hr a) mass production lowers cost b) best for rural areas 2. Germany subsidizes solar industry. 3. solar electric windows are produced in Germany a) can be used in shingles

Cons 1. lots of water pollution, toxic metals in production 2. production and installation costs are high 2. night energy ---> batteries (expensive)

Earth’s internal heat produces geothermal energy Geothermal energy- using the heat from natural radioactive decay of elements deep within Earth as well as heat coming from Earth.

Thermodynamic principles Compression of a gas and condensation (gas to liquid) are exothermic Give off heat Expansion and vaporization are endothermic Absorb heat

Wind energy is the most rapidly growing source of electricity Wind energy- using a wind turbine to convert kinetic energy into electrical energy.

Wind Farm

Wind Power 1) Technology is called wind turbines 2) Wind farms in California produce 1% of power

Wind Power 1) Pros: a) no CO 2 b) land below can still be used - Newsweek article c) modular 2) Cons: a) requires fairly constant wind so limited sites available, b) can interfere with bird migration

Hydrogen fuel cells have many potential applications Fuel cell- a device that operates like a common battery where electricity is generated by a reaction between two chemicals.