Payback Time, U - Values and Specific Heat Capacity Flashcards
How do you calculate payback time?
payback time (years) = cost of installation (£) ÷ savings per year in fuel costs (£)
What do U-Values do?
Measure the effectiveness of a material as an insulator.
What does the Specific Heat Capacity of an substance allow us to do?
Calculate the amount of energy needed to heat it up.
How do we know if a material is a good insulator?
It has a low U-Value.
What are solar panels useful for?
Not generating electricity, but heating up water.
What are the advantages and disadvantages of solar energy?
Solar energy is renewable.
No harmful, polluting gases are produced.
Solar panels may only produce very hot water during very sunny climates.
Cooler areas may need to be supplemented with a conventional boiler.
Warm water can be produced on cloudy days, but solar panels do not work at night.
What is temperature?
A measure of how hot something is.
What is heat?
A measure of the thermal energy contained in an object.
When heat energy is transferred to an object, what does the temperature increase depend on?
The mass of the object.
The substance the object is made of.
The amount of energy transferred to the object.
What is the Specific Heat Capacity of a substance?
The amount of energy needed to change the temperature of 1kg of the substance by 1 degrees Celsius.
Water has a high Specific Heat Capacity, why is this useful?
Because it means it can store heat energy. It also means it can be moved around the home by central heating pipes.
What is the equation to calculate Specific Heat Capacity?
E = m × c × θ
E is the energy transferred in joules, J
m is the mass of the substances in kg
c is the specific heat capacity in J / kg °C
θ (‘theta’) is the temperature change in degrees Celsius, °C
