Building Services Engineering 5th Edition Handbook

48 Energy economics
annual cost = useful energy required
= 33 612 GJ
year × £7.20
GJ
= £242 006 p.a.
GJ
year × cost £
useful GJ
EXAMPLE 2.11
An initial energy audit of a hospital revealed the data shown in Table 2.7. The data were
for a month that had 260 degree days, and the energy manager required energy use
performance factors of total cost per square metre of floor area, heating system energy
used per degree day and electrical energy used per person per hour. All gas consumed was
for the heating system and cost 1.85 p/kWh plus £750 per month standing charge and
£550 per month for maintenance.
Electricity cost was 10 p/kWh and maintenance costs amounted to £550 per month.
Table 2.7 Energy audit data for Example 2.11.
Location Electricity (kWh) Gas (kWh) Floor (m 2 ) Usage (h) Occupants
Medical 12 000 000 13 000 000 45 000 670 2300
Administration 1 500 000 1 000 000 3500 350 220
Engineering 150 000 250 000 1000 400 23
Totals 13 650 000 14 250 000 49 500 1420 2543
Energy use performance factor of total cost per square metre of floor area for the month,
EUPF 1 :
electricity cost = 13 650 000 kWh × 10
= £1 365 550
gas cost = 14 250 000 × 1.85
= £264 925
£1 365 550 + £264 925
EUPF 1 =
49 500 m 2
= £32.94 per m 2 floor area
p
kWh × £1
100 p + £550
p
kWh × £1 + £750 + £550
100 p
EUPF 2 gas heating system energy used per degree day:
EUPF 2 =
14 250 000 kWh
260 degree days
= 54 808 kWh/degree day