Science 10Aim: Efficiency, Energy and us.

AgendaEfficiency, Energy and usStudy Guide – HomeworkQuizzes back on MondayNext class

The initial energy source applied to a machine is called the energy input (think electricity)

The desired energy needed to do work is called the useful output energy

The work done by the machine is called the useful work output

Energy and work that is not useful are called waste energy and waste work

Useful Energy and Efficiency

A measurement of how effective a machine is at converting energy input into useful energy output.

Car engine efficiency = 12-15%Electric engine = Up to 95%Steam reciprocal engine = 50-75%Steam turbine engine = Up to 40%

Efficiency

Conversion of total mechanical energy to useful mechanical energy

Or

A crane lifts a load of construction materials from the ground to the second floor of a building. In the process, the crane does 2.30 x 104 J of work or mechanical energy input, while doing 8.00 x103 J of useful work or mechanical energy output in lifting the load. What is the mechanical percent efficiency of the crane?

Question

In heating a pot of water, 2.00x103 J of heat was supplied by the stove element. If only 5.00x102 J of heat was actually gained by the water (heat output), what was the percent efficiency of the stove element?

Transfer of total thermal energy to useful thermal energy

For devices that convert heat to mechanical energy use

For devices that convert mechanical energy to heat use

Conversion of total thermal energy to useful mechanical energy or vice versa

Energy supply broken down into two types1. Solar energy sources2. Non-solar energy sources

Renewable and Non-renewable Energy sources

Renewable – Continually and infinitely available.

Non-renewable – limited an irreplaceable

Energy Applications

Historically, our ancestors used only renewable resources like solar energy wood or biomass.

This is only a fraction of what is used today.There is a high demand placed on energy

sources now. Amount of energy used per person has

increased exponentially The world population has increased as well. Many societies use non-renewable resources

rather than renewable resources.

Energy Demand

The high demands of fossil fuels has led to a strain on existing supplies

Searching for and extracting new supplies have led to damaging effects on the ecosystem.

The effects of energy use

At the rate we are using oil, coal, and natural gas, it is projected that our supply will run out in ~40, ~216, and ~62 years respectively.

Decreasing the rate at which we use these fuels does not stop the problem, but only delays the result.

Energy Consumption and Conservation

Switching Energy Sources is an alternative to using all of the fossil fuels up.

Unfortunately this is very expensive, and is difficult to implement into society.

Until we find an alternative source, our best bet is to conserve what we have now.

Alternative Energy Sources

The process in which industries use the waste material from one process to power a second process.

Ex. Using the steam from thermal power stations to heat nearby buildings before being heated again in the thermal power station.

Cogeneration

Turn off unused appliances Turn down thermostat (where more

clothes) Car pool, or take public transport Avoid energy wasting appliances and

gadgets. Reduce water consumption (in shower,

sink, watering lawns, etc..)

How could you conserve energy?

Economic Development that meets current needs without compromising the ability of future generations to meet their needs.

Sustainable Developement