Page 150 - Materials Chemistry, Second Edition

146 7. MCDM for sustainability ranking of district heating systems considering uncertainties

7.3 Results and discussion

7.3.1 The case of seven DH systems in a city of north China
The seven DH systems are planned based on the same DH area in Baoding, a city in the
2
north of China (Wei et al., 2010). The floor heating area is 251,746m with a design heat load
of 16.6MW. Space heating season is 120days a year and the average outdoor air temperature
is 1.6°C. The design indoor and outdoor air temperatures are 18°C and 9°C respectively.
Assume that all DH systems provide the same DH capacity for this area, and then the
properties of economy, environment, and energy for the seven DH systems are shown in
Table 7.1 (Wei et al., 2010).
There are both quantitative and qualitative criteria in Table 7.1. The uncertainty of eco-
nomic indices is assumed as 10% (Hokkanen et al., 2000); because the emission data has large
flexibility, so an uncertainty of 20% is used for the environmental criteria. However, for the
qualitative (ordinal) energy criteria, the uncertainty will be handed by SMAA-O automati-
cally using the Monte Carlo simulation. The uncertainty in weighting is considered by an
FWS in this chapter. The FWS is obtained by giving 50% linear constraints using uniform
distribution (Wang et al., 2015) to each criterion based on the weight vector elicited by Wei
et al. (2010). The FWS can cover more possible preference information, indicated in Fig. 7.5.

7.3.2 Results of stochastic multicriteria acceptability analysis

The criteria PVs of the seven DH systems in Table 7.1 should be normalized first before
being used in SMAA. In this study, we used 100,000 Monte Carlo iterations to calculate
the statistic variables in the simulation (Wang et al., 2016), and this will result in error limits

TABLE 7.1 Properties of the seven DH systems.
Coal-fired Gas-fired Oil-fired Coal-fired Solar
Criteria CHP HOB HOB HOB energy HP WSHP GSHP
Total cost per floor 26.96 46.85 78.40 32.19 67.88 54.95 62.27
2 a
area (¥/m )
2 b
NO x (g/m ) 588.0 92.9 116.0 840.0 91.9 78.4 87.8
2 b
SO 2 (g/m ) 179.0 94.0 127.0 255.7 162.0 138.1 154.8
2 b
CO (g/m ) 8.9 1.9 3.5 40.9 1.14 0.85 0.95
2 b
CO 2 (g/m ) 40871 31920 40314 58224 24054 20504 22985
2 b
Other (g/m ) 73.9 27.1 18.1 105.6 22.2 19.0 21.3
Technical merits c Good Good Good Little bad Neutral Good Good
Mentality effect c Better Good Good bad Good Good Good
Heating charge c Better Neutral Bad Better Bad Little bad Neutral
a
Includes the annuity of initial investment and annual operating cost, ¥ means Chinese currency RMB yuan.
b
Emission is calculated based on the floor heating area.
c
These three properties are deemed as qualitative (ordinal) criteria.