P1.5 (Origins of the universe) (U-values and SPH) Flashcards
What does a U-Value do?
A U-Value is the measure the effectiveness of a material as an insulator
What is specific heat capacity?
Specific Heat Capacity is the amount of thermal energy required to change a unit by one degree in temperature
What is SPH measured in?
j/kg*c *=degrees
How do you relate SPH to energy transfer?
E = m x c x 0
energy transferred in joules = mass (kg) x SPH x temperature change in degrees celcius
What does a lower U-value mean?
The lower the u-value the better the material is as an insulator
Would a solid brick wall have a U-value of 5.0 W/m2 or 2.0 W/m2
2.0 w/m2
Which is the better insulator? A cavity wall ( u-value: 1.6 w/m2) or a double glazed window (u-value: 2.8 w/m2)?
A cavity wall as it’s u-value is lower
What is payback time?
How long it takes for an expensive energy saving unit eg double glazed windows to earn you your money back in savings.
How do you calculate payback time?
Payback time ( years ) = cost of installation (£) / savings per year in fuel costs (£)
How do you achieve the shortest payback time?
if there is a low cost of installation and high savings
The double glazing for a house costs £3,000 but saves £150 per year in fuel costs. What is its payback time?
3000/150= 20 years
How do solar panels work?
They use the heat from the sun to heat up water
Why are they dark in colour?
Because dark colours are the best at absorbing heat
What are advantages of solar power?
Solar power is renewable
No harmful gases are produced
What are disadvantages of solar power?
They may only work in very sunny areas
They do not work at night
