- The term energy efficiency refers to the measure of the useful energy.
- The 2nd Law of Thermodynamics states that in any spontaneous change, the entropy of the universe must increase; which means that the quality of energy deteriorates gradually over time.
- Input is all components (matter and/or energy) entering the system.
- Throughput is the flow of all components within the system.
- Output is all components leaving the system.
- The efficiency of a product can be measured by:% efficiency = (output ÷ input) x 100
- Negative feedback: reverses the direction of the flow.
- Positive feedback: changes the rate of the throughput, but not the direction.
- A high throughput economy is one that has a high output.
- A Low Throughput economy is one that has a balance of input and output.
- industry accounts for about 42% of u.s. energy consumption.
- we can save energy i building by getting heat from the sun, super insulating them, and using plan covered green roofs.
- pros of solar heating are: energy is free, quick installation, o carbon dioxide emissions.
- cons of solar heating are: need access to the sun 60% of the time, high cost, no heat storage system.
- pros of solar energy: moderate net energy, no co2 emissions, fast construction and moderate environmental impact.
- Cons of solar energy: low efficiency, high costs, high land use.
- Pros of Solar cells: fail high net energy, work on cloudy days and quick installation.
- cons of solar cells: need access to sun, Low efficiency and high costs.
- Pros of hydro power: Moderate to high net energy, high efficiency and long life span.
- Cons of Hydro power: high cons, danger o collapse, uproots people.
- Advantages of wind power: High efficiency, Low electricity cost and quick constructions
- disadvantages of wind power: steady winds needed, visual pollution and high land use for wind farm.
- advantages/ of hydrogen low environmental impact, no co2 emissions if produced from water, easier to store than electricity.
- disadvantages of hydrogen: not found in nature, negative net energy and no energy neeed to produce fuel