Neumayer, Eric and Plümper, Thomas Skip to main content Accessibility help We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Designing for robustness is a common goal across many disciplines that deal with systems, for example design theory and methodology. The continued application of ecosystem robustness to human systems will provide more insights into developing a holistic approach to assess sustainability of human systems that accounts for both the system form and function, energy conservation and system organization.
No, PLOS is a nonprofit 501(c)(3) corporation, #C2354500, based in San Francisco, California, US, https://doi.org/10.1371/journal.pone.0226993.
Ecological pathway efficiency and thermal efficiency positively correlate among a single set of power cycle modifications, and although increases in thermal efficiency tend to reduce system robustness, the relationship is not a general one.
Similarly in ecosystems, pathway redundancy prevents AMI from ever reaching H. One difference however is that, for all the modified power cycles considered here, H changes but the Carnot efficiency remains the same as the basic version. No, Is the Subject Area "Shannon index" applicable to this article? The uncertainty that researchers face in specifying their estimation model threatens the validity of their inferences. The two sets of Rankine cycle variations, with open feedwater heaters and with reheat and open feedwater heaters, both show an initial negative relation between ASC/DC and thermal efficiency from the first modification to the second resulting in much lower R2 values of 0.22 and 0.59 respectively. Intended and unintended modifications can both cause system development and evolution. https://doi.org/10.1371/journal.pone.0226993.s001. The compressor draws in air from the atmosphere and compresses it, resulting in an increase in temperature and pressure.
These threats suggest that human systems can benefit from mimicking ecosystem robustness levels, preventing efficiency focused design decisions that result in highly streamlined pathways causing the system to be vulnerable to disturbances. Irreversibility, the difference between maximum possible output and the actual output, arises due to entropy generation and prevents the thermal efficiency of these power cycles from ever reaching their Carnot efficiency. Focusing on each dimension of model uncertainty in separate chapters, the authors provide a systematic overview of existing tests and develop many new ones.
Investigation,
Although network robustness is not usually considered in the design of these cycles, they provide an opportunity to compare network modifications made to increase work output with the evolution seen in naturally sustainable ecosystems.
Eric Neumayer, Thomas Plümper, "Robustness Tests for Quantitative Research" 2017 | ISBN-10: 1108401384, 1108415393 | 268 pages | PDF | 2 MB Data curation, Answering this question will enable a broader application of ENA metrics and ecosystem characteristics to engineering and energy systems design. Brayton and Rankine cycles produce power by using energy in the working fluid, water and air respectively, via thermodynamic processes. Formal analysis,
Biological ecosystems and industrial resource networks (networks of interacting industries) both represent a collection of entities (species and industries respectively) that exchange material and energy. These metrics are calculated using information about the network structure (the presence or absence of a directed connection between two species) and network flow information (the magnitude of material/energy in those connections). Both Figs 4 and 5 show the corresponding linear trend lines.
Robustness for ecosystems on the other hand is well defined with a detailed quantitative formulation that considers both those attributes.
Their results suggested that increases in thermal efficiency, indicating efficiency improvements in the use of input energy, correlated with higher cyclicity values, a characteristic of biological ecosystems.
Investigation, Methodological Tools in the Social Sciences. Yes Two basic thermodynamic systems are used here: Rankine and Brayton power cycles. Fig 5 shows ecological robustness (Fig 5) for the thermodynamic power cycles with respect to increasing thermal efficiency. A basic Brayton cycle consists of three components: compressor, combustor and turbine. The enthalpies, work, and heat for the cycles were calculated using Engineering Equation Solver (EES) version V8.881-3D. The negative trend between thermal efficiency and ecological robustness, which is considered a measure of sustainability for ecosystems, also points out a possible incompatibility between the energy conservation perspective [5, 28, 29] and the network perspective of sustainability.
Ecological network efficiency however, measures the efficiency of the network structure in terms of the number of pathways available for any given unit of flow.
The Brayton cycle B1 has the lowest ASC/DC and B7 has the highest, 0.56 and 0.80 respectively, resulting in a high R2 value of 0.95 that suggests a strong connection between increases in thermal efficiency and increases in ecological pathway efficiency. Thermodynamic cycles provide good examples of human systems where simple and clearly defined modifications can be made to increase efficiency.
The source and sink temperatures of each cycle are kept constant across all the variations investigated here to ensure accurate comparisons, Table 1. This method is also useful when a series of data points are highly desirable within a particular demographic.
The modifications on the basic Brayton cycle include the addition of regeneration, intercooling and reheat, creating a total of 8 different Brayton cycles with increasing efficiencies. The relationships between thermodynamic efficiency and four ecological flow metrics, robustness (R), ASC/DC, AMI and H, are processed for twenty three Rankine and Brayton cycles (one set of variations was done on the Brayton cycle and two are done for the Rankine cycle). The ratio ASC/DC (or AMI/H) represents the degree of system order on a scale of zero to one [23], presenting a dimensionless measure of pathway efficiency. The results clearly show that the power cycles are able to increase their ecological robustness and their thermal efficiency at times, these +/+ scenarios upon investigation can be seen to be points where value (in the form of energy) remaining in the working fluid that originally was dumped to the surroundings is cleverly circulated back into the power cycle using components such as heat exchangers, intercoolers, reheaters and open feedwater pumps. (8) Sustainable ecosystems have been found to cluster around what is known as the “window of vitality” (highlighted in Fig 3), that encompasses the maximum ecological robustness value of R = 0.367 or 1/e) [11, 12, 37].
https://doi.org/10.1371/journal.pone.0226993.g002, Total system throughput (TSTp, Eq 6) is the sum of all the flows interacting with the system.
(10)
The ASC/DC values of the basic Brayton and Rankine cycles are highlighted by the red and blue dotted lines. Human networks often experience disturbances analogous to ecosystems: for example, weather changes and variations in supply and demand. Robustness in Statistics contains the proceedings of a Workshop on Robustness in Statistics held on April 11-12, 1978, at the Army Research Office in Research Triangle Park, North Carolina. In regression analyses of observational data, the 'true model' remains unknown, and researchers face a choice between plausible alternative specifications.
The peak of the curve corresponds to a R value of 0.368 and an ASC/DC value of 0.368.
Copyright: © 2019 Panyam, Layton.
https://doi.org/10.1371/journal.pone.0226993.g003. Cyclicity increases can thus be understood to quantify improvements in how a system uses the materials and energy available. Human networks and engineered systems are traditionally designed to maximize efficiency. Fig 5 also highlights a significant difference in the ecological robustness values of the basic versions of the Rankine (R = 0.166) and the Brayton (R = 0.317) power cycles (red and blue dotted lines cutting the vertical axis).
https://doi.org/10.1371/journal.pone.0226993.g001, https://doi.org/10.1371/journal.pone.0226993.t001, The energy exchanges between any two components in the cycle can be calculated using the enthalpy of the working fluid entering and exiting the components.
Writing – original draft,
The first addresses an issue that some ecologists have brought up regarding the existing discordant theories for the study of ecosystems [13, 29].
ENA metrics, these included, are derived from information theory. An ASC/DC value closer to one indicates a more streamlined network structure with less pathway diversity. The ENA of power cycles here considers each component in the thermodynamic cycles an actor. Natural systems have been found by ecologists as having up to 25% redundancy [22]. Figure used with permission from [26]. Fig 6 shows the relationship between thermal efficiency and AMI. This initial modification increasing both ηI and R is not seen for either of the two Rankine cycle modification sets and can be conceptually explained by looking at how the modification changes the structure of the cycle. https://doi.org/10.1371/journal.pone.0226993, Editor: Liao Zuwei,
All the flows are measured in [kJ/kg] of energy. Efficiency and redundancy in ecological network pathways have been extensively investigated in the past two to three decades [12, 13]. Focusing on each dimension of model uncertainty in separate chapters, the authors provide a systematic overview of existing tests and develop many new ones. Shannon Index (H) quantifies the total capacity for organization in an ecosystem. Methodology, Modifications to the Rankine cycle were similar but were carried out as two sets of variations, creating a total of 15 Rankine cycles: 1) adding an increasing number of open feedwater heaters to the simple Rankine cycle (RO1 adds one open feedwater heater and RO2 adds two) and 2) adding reheat and open feedwater heaters to the simple Rankine cycle (RRO1 adds reheat and one open feedwater heater, RRO2 adds reheat and two open feedwater heaters, etc.). The second benefits the current efforts in the field of industrial ecology by providing norms for strengthening the analogy between ecological and human systems. Fig 2 shows a flow matrix for the basic Rankine cycle of Fig 1. This discovery is especially important for systems that might have vulnerable customers or unstable weather for example. Water passes through the different components, converting from a liquid state to a vapor state and back. This highly accessible book presents the logic of robustness testing, provides an operational definition of robustness that can be applied in all quantitative research, and introduces readers to diverse types of robustness tests. The analogy’s application is based on the hypothesis that when industrial systems mimic features of ecosystems they are able to approach the sustainable and efficient functional characteristics of biological ecosystems. [T] is a (N+3) x (N+3) matrix that contains quantitative flow magnitudes for all of the internal interactions from node i to node j, inputs, outputs and dissipation for an ecosystem network [11]. Translating this flow-based ecosystem robustness into an engineering context supports the creation of new robust and sustainable design guidelines for engineered systems. UNILAB Research Center for Chemical Reaction Engineering, CHINA, Received: July 21, 2019; Accepted: December 10, 2019; Published: December 31, 2019.
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