(6.51) prevents direct burning of natural gas to meet the cooling load if AC for this
purpose has not been purchased.
RHeat i,m,d,h,u ¼ 0 8i, m, d, h if u= 2U i
ð Þ
ð6:48Þ
EGen i,m,d,h,u ¼ 0 8i, m, d, h if u 2 space heating water heating
f
gð6:49Þ
PGas m,d,h,u ¼ 0 8m, d, h if u 2 electricity only
f
g
ð6:50Þ
PGas m,d,h,u DCCap Á DC 8m, d, h if u 2 cooling
f
g
ð6:51Þ
PElec m,d,h,u ¼ 0 8m, d, h if u 2 space heating water heating
f
g
ð6:52Þ
A constraint is set to prohibit the customer from simultaneously buying and
selling energy (Eq. 6.53).
ESal i,m,d,h ¼ 0
if
X
u
X
i
EGen i,m,d,h,u <
X
u
Cload m,d,h,u 8i, m, d, h if u 2 electricity only
f
g
ð6:53Þ
According to contact with electric utilities, electricity purchases cannot be lower
than a specific percentage of the total requirements (Eq. 6.54).
X
m
X
d
X
h
X
u
PElec m,d,h,u ! θ Á
X
m
X
d
X
h
X
u
PElec m,d,h,u
þ
X
i
EGen i,m,d,h,u þ λ u Á OElec m,d,h,u
ð6:54Þ
In addition, operational experience shows that frequent starting and stopping will
accelerate equipment deterioration. Here, the cost coefficient is associated with
starting and stopping generation. Using the following equations, the frequency of
starting and stopping is expected to be minimized.
D i,m,d,hþ1 À D i,m,d,h ¼ FStart i,m,d,h À FStop i,m,d,h 8i, m, d, h
ð6:55Þ
X
u
EGen i,m,d,h,u þ IElec i,m,d,h þ Esal i,m,d,h À M Á D i,m,d,h 0 8i, m, d, h ð6:56Þ
132
H. Ren and W. Zhou