Page 144 - Materials Chemistry, Second Edition

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

choosing the most suitable DH system for a specific area is very important to decision makers
(DMs) and managers (Cao, 2002). The evaluation of DH systems is not a single objective prob-
lem; on the contrary, it is a typical multicriteria decision making (MCDM) problem, and the
use of MCDM method in heating ventilating and air conditioning (HVAC) systems are of
more importance ( Jiang et al., 2007). It can help the DMs make more consistent decisions
by considering all important factors, which often include conflicting criteria and usually have
some uncertainties (Troldborg et al., 2014; Shan et al., 2013; Gang et al., 2015).
In this chapter, seven popular DH systems (Wei et al., 2010) are evaluated with more em-
phasis on the uncertainties in criteria performance values (PVs) and the weighting. These DH
systems cover a wide range: (1) coal-fired CHP; (2) gas-fired HOB; (3) oil-fired HOB; (4) coal-
fired HOB; (5) solar energy HP; (6) water source heat pump (WSHP); and (7) ground source
heat pump (GSHP). Most of the data for these DH systems are based on real-life existing DH
installations.
Some previous studies have been carried out to develop multicriteria evaluation methods
for choosing the optimal DH systems or heating technologies from the standpoints of tech-
nology, economy, and environment. Ghafghazi et al. (2010) have done a multicriteria evalu-
ation for choosing the energy sources of a DH system in Vancouver, Canada; possible energy
sources are natural gas, wood pellets, sewer heat, and geothermal heat. The evaluation
criteria are: GHG emissions, particulate matter emissions, maturity of technology, traffic load,
and local source. Kontu et al. (2015) carried out a multicriteria evaluation of heating systems
including many renewable energy forms for a sustainable residential area in southern Fin-
land. In their study, altogether 11 alternative heating systems were evaluated in terms of
15 criteria. The stochastic multicriteria acceptability analysis (SMAA) method was also used
to analyze this problem, but the study did not take into account the uncertainty in weighting.
Soltero et al. (2016) developed a framework to evaluate the potential for natural gas cogen-
eration to reach decarbonization economy in Spain. The evaluation was implemented by en-
vironmental, economic, and regulatory analyses at four levels, including national, regional,
municipality, and district, using a proposed top-down/bottom-up methodology. Li et al.
(2016) evaluated the CCHP systems for hotels, offices, and residential buildings in Dalian,
China, from energetic analysis, economic operation, and environment effect viewpoints.
They use fuzzy optimum selection theory to evaluate the integrated performances of CCHP
systems with various operation strategies, but the uncertainties in weighting the process are
not well defined. The abovementioned methods worked well in the application-oriented case
studies, but it could be better if uncertainties in criteria and weighting were considered in
their studies.
In general, different kinds of uncertainties in criteria PVs and in subjective judgments
(Zarghami and Szidarovszky, 2009; Durbach and Stewart, 2012) as well as policy and tech-
nology uncertainties (Tylock et al., 2012) are very common and thus should be treated care-
fully. In this study, we adopt the stochastic multicriteria acceptability analysis (SMAA) model
to evaluate the DH systems, because it can handle the uncertainties by using a probability
distribution function (PDF) and a Monte Carlo simulation (Wang and Haves, 2014). More-
over, we also propose to use the “feasible weight space” (FWS) but not a deterministic weight
vector in MCDM, because the weights should indicate all DMs’ preference information
(Wang et al., 2015). In fact, FWS is a union of all weight vectors obtained from DMs’ judgment
matrices.