Zusammenfassung der Ressource
P1.2.1 Energy transfers and efficiency
- When energy is transferred only part of it may be usefully transferred, the rest is 'wasted'
- this wasted energy is eventually transferred to the surroundings, which become warmer
- the wasted energy becomes increasingly spread out (it's dissipated)
- and so becomes less useful
- useful energy eventually transfers to the surroundings too
- key principles
- Energy can be transferred usefully, stored or dissipated
- but cannot be created or destroyed
- the Conservation of Energy
- energy is only useful- when it can be converted from one form to another
- All energy transfers taking part in a process can be summarised with a Sankey diagram
- All energy processes taking part in a process can be summarised with a Sankey Diagram
- to calculate the efficiency of a device
- use one of the two equations on the P1 equations sheet
- the greater the percentage of the energy that is usefully transferred in a device, the more efficient the device is
- you need to think about cost-effectiveness
- when choosing new appliances
- low energy light bulbs
- is about 4 x more efficient than an ordinary lightbulb
- are also more expensive
- but, as they last longer, are energy-saving/efficient light bulbs are generally more cost-effective
- LED light bulbs are even more efficient than low-energy bulbs
- and last even longer than them (long)
- but are more expensive
- and give out less light than the other two types
- light bulbs
- replacing old appliances with energy efficient ones
- new, efficient appliances are cheaper to run
- but are more expensive
- to work out if a appliance is cost effective, work out its
- payback time
- the time it takes for the annual
saving on energy bills to equal
the initial cost
- = initial cost/ annual saving
- and efficiency
- making waste energy useful
- heat exchangers
- 1) Pump a cool fluid through the escaping heat
- 2) The temperature of this fluid rises as it gains heat energy
- 3) This heat energy can then be converted into a useful form
- 4) either in the original appliance or for another function
- e.g. heat from a car's engine can be transferred to the air in the
passenger compartment- thus warming it
- Ultimately, all energy ends up as heat energy
- If you use an electric drill, it gives out various types of energy, but they all quickly end up as heat
- Meaning, an electric heater is perhaps
the only appliance that is 100% efficient
- as all the electricity is given out as 'useful' heat
- types of energy
- chemical energy
- is energy stored in fuel (inc food. this energy is released when chemical reactions take place
- kinetic energy
- is the energy of a moving object
- gravitational potential energy
- the energy of an object due to its position
- elastic potential energy
- the energy stored in a springy object when we stretch or squash it
- these types of energy are forms of stored energy
- e.g. they are waiting to be turned into another form
- electrical energy
- energy transferred by an electric current