Evaluation of sustainable useful index (SUI) by fuzzy approach for energy producing processes

Energy Sustainability Analysis (ESA) of Energy-Producing Processes: A Case Study on Distributed H2 Production

“…As previously introduced in [27], the ESA methodology applied to a given technology is based on the concept of viability, resembling the feature of living organisms of harnessing energy to sustain and reproduce themselves [46]. Hence, a viable technology or an energy sustainable technology should be able to produce an energy surplus, useful energy, which is able to feed society after the direct and indirect energy costs of the process itself are discounted.…”

“…The following step in the ESA is the rationalization of all energy quotas that are present in the process/technology under analysis, besides the produced energy and direct energy. Following [27], a suitable way to perform this step is through the use of the AM, used typically in LCA studies for the inventory analysis [51], combined with a bottom-up approach. The AM comprehends a careful look at the process, within the chosen boundaries, to calculate the energy contributions (E ind,i ) of the indirect energy (E ind ) using Equation 2, where n represents the number of the considered components in the analysis (see Table 1).…”

“…Although economic analyses are often believed to capture all relevant features of a given technology [27,28], in a finite resource scenario, more complex evaluation tools are required, due to the potential negative externalities which cannot be included in price-schemes, such as the depletion of energy sources or the reduction of useful energy which is delivered to society to satisfy energy services. A simple fundamental idea, suggested by Hubbert in 1956 [29], states: if extraction of fuel requires more energy than the fuel provides, no economical argumentation can overpass this physical limit.…”

“…Hence, energy sustainability should be evaluated in primis due to its hierarchical importance in the quantification of the useful energy that can be diverted from societal uses into sustainable solutions, innovations and policies. As noted in [27], it is the flow of useful energy which allows society to divert attention from endosomatic life-sustaining needs towards exosomatic needs, such as health care, arts, education, research, and innovation. Energy sustainability could be one of the most important criteria to select among different technologies which harvest resources to store energy and to use energy as a pillar in the design of technologies and/or process configurations which enable sustainable energy services [31].…”

“…Contrary to ecological models which address flow-fund models applied simultaneously to matter and energy and, therefore, resort to entropic levels of terrestrial resources, ESA avails itself of different indicators, which are often used in economic analysis, but adapted to energy flows and funds. The first energy sustainability indicator, which can be used for fast screening, is the energy sustainability index (ESI) [27]. This indicator compares the main flow of produced energy with the flow of direct energy input to the process (flow resources), without considering the indirect energy expenditures (fund resources).…”