Keeping homes warm
Efficiency and payback time
- The efficiency of a device is the proportion of the energy supplied that is transferred in useful ways
- Energy efficiency is not just about heating homes. Everything that transfers energy wastes some of the energy as heat to the surroundings
- Energy can be transferred usefully, stored or dissipated. It cannot be created or destroyed.
- You must know this equation in order to be able to work out efficiency
efficiency = useful energy output (x100) ÷ total energy input
- It looks like the one below which is for an filament lamp, sankey diagrams show energy transformation, therefore the energy efficiency is shown
- The width of each arrow depends on the amount of energy transferred to each element
- The energy transfer to light energy is the useful transfer, the rest is ‘wasted’
- To be able to calculate the payback time you must know this equation
payback time (years) = cost of insulation (£) ÷ annual saving (£)
- As we know homes lose energy so to reduce the energy loss the uninsulated homes need to be insulated which could be quite expensive
- This means that it will cost you money in order to save money thus the equation helps you workout the in how many years you will be given back the money you spent on the insulation
- Payback time calculation helps us to work out the most cost-effective type of insulation.
- Heat energy can be lost from homes in many different places but there are ways of reducing these losses.
- There are three…