XVI - Energy Efficiency & Renewable Energy Resources Flashcards
Energy Efficiency
the percentage of total energy input that does useful work in an energy conversion system
Energy efficiency examples
fuel cell 60% steam turbine 45% human body 20-25% fluorescent light 22% internal combustion engine 10% Incandescent light 5%
Net energy efficiency
determined by the efficiency of each step
in the energy conversion process
Net energy efficiency in passive solar
sunlight 100%
10% waste hear
90% transmission
Net energy efficiency in uranium
uranium
Energy waste
43% of the energy used in the U.S. is unnecessarily wasted by using inefficient methods to produce electricity, heat our homes, & drive our cars
What is the importance of reducing energy
- nonrenewable fuels last longer
- time to phase in renewable energy resources
- decrease dependence on oil imports
- reduce local & global environmental damage
- slow global warming
- save money
Ways to improve energy efficiency
Cogeneration
Energy conservation & use of energy efficient lighting & appliances
Better insulated homes
Increases in fuel efficiency of motor/ use of alternative fuel vehicles
Passive solar heating
Sunlight is captured directly within a structure & converts it into low–temperature heat for space heating
Where is heat released throughout the day?
Heat is stored in walls & floors made of materials like concrete, brick, stone, or tires & is released slowly throughout the day
Where can passive solar & superinsulated design the cheapest?
A passive solar & superinsulated design is the cheapest way to heat a home in regions where sunlight is available more than 60% of daylight hours.
Active solar heating
solar collectors absorb solar energy & a fan or pump supplies the building’s space or water heating needs
Pros solar heating
• solar energy is free • net energy yield is high for passive & moderate for active • technology is well developed & easily installed • takes up little land space • does not emit polluting or greenhouse gases
Cons solar heating
• need to secure solar rights • solar collectors are ugly to some people • active systems are costly
How can solar energy be used to produce electricity?
Converted directly into electrical energy by photovoltaic cells
Sunlight striking silicon atoms creates an electrical current
Stored in batteries
Components of solar energy
Power lines Photovoltaic panels Inverter To breaker panel Battery bank
Inverter
Converts DC to AC
Battery bank
located in shed outside house due to explosive nature of battery gases
Mass generation of solar energy
Solar tower power
Solar thermal plant
Methods of producing electricity from water
Hydroelectric dams
Tides & waves
Ocean thermal energy conversion & solar ponds
Pros of hydropower
No emission/ pollution
High net energy yields for dams
Moderate yields for ponds
Cons of hydropower
Flood upstream habitats & alter downstream habitats
Limited areas
Thermal energy from bodies of water can’t compete economically
Pros producing energy from wind
- unlimited source of energy at favorable sites
- moderate to high net energy yield
- easy to build & expand
- emit no pollutants or greenhouse gases
- land can also be used for agriculture
Cons producing energy from wind
• economical only in areas with steady winds
• back–up energy sources are necessary
• mass production takes up a great deal of land
space
• noise pollution
• may interfere with migrating birds
Using wood pros
• a potentially renewable
energy resource
• high net energy yield if
burned near source
Using wood cons
• currently exploited in nonrenewable & unsustainable ways • single–species biomass plantations reduce biodiversity • burning wood produces air pollutants such as particulates
What can be considered as biomass?
Wood Charcoal Agricultural waste Timbering wastes Animal waste Aquatic plants Urban wastes
What can energy be produced from biomass?
Direct burning
Conversions to gaseous & liquid biofuels
Gaseous biofuels
Synthetic natural gas
Wood gas
Liquid biofiels
Ethanol
Methanol
Gasinol
Solar hydrogen revolution
Producing energy using combustion of water
The benefit of using hydrogen
• the source of hydrogen, water, is plentiful
• when burned, hydrogen produces no carbon dioxide,
but instead water vapor & nitrogen oxides
• using hydrogen for fuel would eliminate most air
pollution problems & reduce greenhouse gas emissions
The problem
• hydrogen is really only a way to store energy; requires
energy source to split hydrogen from water
• currently nonrenewable energy sources are used to
produce hydrogen, negating many benefits
Solution
• use renewable sources of energy, most notably solar,
to produce hydrogen for combustion
• currently it costs more to use solar energy than other
energy sources, but could be phased in over time
