
392 Principles of Sustainable Energy Systems
© 2008 Taylor & Francis Group, LLC
The monthly °C-days for Denver are taken from the U.S. NWS and given in Table 7.9.
The energy demand is calculated as
Energydemand
day
C-days=× ×°UA
B
24
The monthly energy demand is given in Table 7.9.
If the annual energy demand of 62.9 GJ is delivered by a 65% efcient gas furnace,
then the
Averageannual purchased energy =
62.9
GJ GJ= 96 8.
7.5.4 Service Hot Water Load Calculation
Service hot water loads can be calculated precisely with the knowledge of only a few vari-
ables. The data required for calculation of hot water demand are
Water source temperature (T
s
)
Water deliv ...