Residential annual energy use. For a house with: Air exchange rate of 0.5 h−1 Cp = 1000 J/kg.K Density of air = 1.2 kg/m3 Roof area = 144 m2; opaque wall area = 96 m2; window area = 24 m2; volume = 360 m3 Conductivity of Uwall = 0.60 W/(m2-K); Uwin = 3.0 W/(m2-K); Uroof = 0.40 W/(m2-K) Heating system efficiency of 0.85 Heating degree days (HDD) of 3500 K-days Calculate the Ktot for this house. Calculate the annual energy used to heat this house (in GJ).

Compare the masses and volumes of water, concrete, sand, and wood needed to store 106 Btu of heat if the operating temperatures are Tc = 85F and Th = 180F. In each case, calculate the edge length of a square storage unit with a height of 8 ft.

1   Which of the following produces pure water day and night? a. Passive solar water still b. Solar dryer c. Forced circulation water heater d. Active solar water still

A heat pump supplies heat energy to a house at the rate of 140,000 kJ/h when the house is maintained at 25°C. Over a period of one month, the heat pump operates for 100 hours to transfer energy from a heat source outside the house to inside the house. Consider a heat pump receiving heat from two different outside energy sources. In one application the heat pump receives heat from the outside air at 0°C. In a second application the heat pump receives heat from a lake having a water temperature of 10°C. If electricity costs $0.105/kWh, determine the maximum money saved by using the lake water rather than the outside air as the outside energy source.