Page 151 - Materials Chemistry, Second Edition

7.3 Results and discussion 147
Weight vector –50% scope +50% scope
50
45
40
35
Weight (%) 25
30
20
15
10
5
0
Total cost NOx SO 2 CO CO 2 Other Technical Mentality Heating
merits effect charge
Criteria
FIG. 7.5 The FWS with 50% interval constraints using uniform distribution on each criterion for evaluation of
the DH systems.

smaller than 0.01 (Tervonen and Lahdelma, 2007). The confidence factors, holistic acceptabil-
ity, and rank acceptability indices are shown in Table 7.2. All rank acceptability indices and
average utilities of each DH system are also illustrated graphically in Fig. 7.6. Here the aver-
age utility is defined as the central-weighted average utility function value based on the
criteria PVs. Central weight vectors and the cross confidence factors are shown in Fig. 7.7
and Table 7.3. Note that there is no central weight vector for DH systems having zero confi-
dence factors.
According to Table 7.2, coal- and oil-fired HOBs can be rejected from the most qualified DH
systems, because their confidence factors are zero. This means that they never obtain the first
rank even considering uncertainties. Similarly, solar energy HP is currently not a good choice
for DH because of its nearly zero confidence factor and very low holistic acceptability index.
GSHP has a 4.87% confidence factor, which is also deemed too small to be the best alternative,
but it still can be a compromise DH system, especially if a weight vector close to its central
weights is used. However, coal-fired CHP has a high confidence factor of 75.75%, followed by

h
c
r
TABLE 7.2 Confidence factors (p ), holistic (a ) and rank acceptability indices (b ) in percentage.
DH system p c a h b 1 b 2 b 3 b 4 b 5 b 6 b 7
Coal-fired CHP 75.75 73.7 51.2 24.9 13.3 10.0 0.5 0 0
Gas-fired HOB 57.43 72.5 39.2 48.8 10.8 1.3 0 0 0
WSHP 18.92 45.7 8.3 20.3 54.2 17.1 0.1 0 0
GSHP 4.87 31.0 1.4 5.9 21.6 69.5 1.7 0 0
Solar energy HP 0.02 12.5 0.001 0 0.1 1.5 68.5 27.7 2.3
Oil-fired HOB 0 6.6 0 0 0 0.1 18.6 55.6 25.7
Coal-fired HOB 0 2.9 0 0 0.1 0.6 10.8 16.6 72.0