Architects need to know how well different materials will insulate the building they design. To help them with this they need to know the U-values of different materials.
A U-value of 1 W/(m2 oC) means a 1 metre square area of the material with a 1 oC temperature difference across the material will conduct heat at a rate of 1 joule per second.
U-values measure how effective an insulator something is. The lower the U-value the better the material is at insulating.
These heat water using the energy from the Sun. The hot water provided can be used to heat homes or to provide domestic hot water.
Specific heat capacity
This is a measure of the amount of energy required to raise the temperature of 1kg of a material by one degree Celsius.
heat transfered = mass x specific heat capacity x temperature change
(joules, J) (kilogram , kg) ( joules / kilogram oC) (degrees Celsius, oC)
Example; How much energy is needed to raise the temperature of 1 kg of water by 30 oC. The specific heat capacity of water is 4200 J/kgoC.