Thermal efficiency calculated using Eq 4 uses the information in Table 2. This method is also useful when a series of data points are highly desirable within a particular demographic. (7) ISBN 9781108415392. The addition of components such as feed-water heaters (FWHs), reheaters, and intercoolers increases the thermodynamic efficiency of the Rankine and Brayton cycles [31]. B represents the basic Brayton cycle and B1 has added regeneration B2 has added intercooling and reheat (resulting in 2 turbines), and B3 is the same as B2 but with 3 turbines.

Neumayer, Eric and Plümper, Thomas The formulation of ecological robustness (R) weights redundancy slightly more than efficiency, placing the peak robustness value at ASC/DC = 0.368. In this paper, we follow the stream of research to propose a quantitative approach for verifying the statistical robustness of tail-dependent law invariant risk measures.

Yes Fig 5 shows ecological robustness (Fig 5) for the thermodynamic power cycles with respect to increasing thermal efficiency. The first addresses an issue that some ecologists have brought up regarding the existing discordant theories for the study of ecosystems [13, 29]. All the flows are measured in [kJ/kg] of energy. PLOS ONE promises fair, rigorous peer review, You can write a book review and share your experiences. 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. Natural systems have been found by ecologists as having up to 25% redundancy [22]. First law efficiency (ηI) measures the net energy output in terms of the total input energy for a thermodynamic system. Robustness testing allows researchers to explore the stability of their main estimates to plausible variations in model specifications. Pathway efficiency, referred to as simply “efficiency” in ecological literature, should be noted to be different from engineering efficiency, as will be discussed later. Methodological Tools in the Social Sciences. Energy in the form of heat and work input to and output from the system are calculated from Eqs 1–3. Writing – review & editing. Values of ASC/DC closer to zero indicate more pathway diversity, or a higher number of pathways available for any given unit of flow. PLoS ONE 14(12): Once again though this trend is not the rule, at least one variation in both the Rankine and Brayton cycles have higher ecological robustness as well as higher thermal efficiencies than their basic configurations. Redundancy in these systems/networks is usually traded for efficiency and profit maximization by optimizing the network configuration. Copyright: © 2019 Panyam, Layton. For more information about PLOS Subject Areas, click here. Conceptualization, These components harness the energy left over in the exhaust gases, usually in the form of waste heat, sending it back to earlier stages in the system where heat is required. This provides an opportunity to test the results of well understood network modifications for energy efficiency on the resultant response of ecosystem metrics. Thermodynamic efficiency represents the efficiency with which the total available energy is used [28]. The red dotted square indicates system boundary. Successful ecosystems are those that are both efficient and robust [ 11 ], with flow path redundancy that enables them to deal with disturbances [ 12 ]. Yes Most ecosystems evolve due to such externally imposed requirements. Many considerations go into defining sustainability of systems, including their social, economic, and environmental aspects [2–4]. The R2 values for the correlation between H and ηI (Fig 7) are 0.88, 0.72 and 0.87 for the modified B, RO and RRO series, respectively. https://doi.org/10.1371/journal.pone.0226993.g008. Whether it be uncertainty about the population or sample, measurement, the set of explanatory variables and their functional form, causal or temporal heterogeneity, or effect dynamics or spatial dependence, this book provides guidance and offers tests that researchers from across the social sciences can employ in their own research. here. This increase can be attributed to the structural changes that are meant to increase the thermal efficiency adding redundancy that increases the robustness. Flow is documented as going from rows to (i) to columns (j).

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Twenty-three variations on the Brayton and Rankine cycles are used to understand the relationship between design decisions that maximize a system’s efficient use of energy (measured by thermodynamic first law efficiency) and ecological measures of robustness and structural efficiency. Cyclicity increases can thus be understood to quantify improvements in how a system uses the materials and energy available. The second benefits the current efforts in the field of industrial ecology by providing norms for strengthening the analogy between ecological and human systems.

The file will be sent to your Kindle account. A benefit to the analysis presented here is that these purposeful design changes have clear effects. No, Is the Subject Area "Power engineering" applicable to this article? Converted file can differ from the original. These subsequent modifications in both the Rankine and Brayton cycles increase the thermal efficiency but decrease both the pathway redundancy and the ecological robustness. Unlike ecosystem robustness (R) and its dependent variable ASC/DC, the AMI and H for power cycles were found to strictly increase with increasing thermal efficiency (Figs 6 and 7). https://doi.org/10.1371/journal.pone.0226993.g004. Hence, connecting ecological robustness, and the balance between pathway efficiency and redundancy that define ecological robustness, with energy efficiency may provide designers and decision makers with a fundamental thermodynamics based understanding of ENA metrics. Click through the PLOS taxonomy to find articles in your field. This comparison suggests that design decisions made to increase ηI in thermodynamic power systems mimic a minimization of pathway diversity, resulting in a system that is significantly more streamlined in structure than what is found on average in ecosystems. The results are listed in Table 3. The red dotted square indicates system boundary. The B1 to B7 Brayton cycles show an increasing trend between ASC/DC and thermal efficiency, as seen in Fig 4. A Chesapeake Bay ecosystem was found to have an ASC/DC of 0.60 [35] and a South Florida Everglades ecosystem had an ASC/DC of 0.55 [36]. The application of these ecological metrics to thermodynamic power cycles provided a quantitative engineering-based understanding.

Robustness testing allows researchers to explore the stability of their main estimates to plausible variations in model specifications. S1–S5 Figs provide additional illustrations of flow diagrams and flow matrices for the first cycle in each modified series of the Brayton and Rankine cycles. Yes Writing – original draft, The three types of power cycle modifications have suggested that the possibility of designing systems that have redundancy in their structure without sacrificing engineering efficiency may be realized using bio-inspiration, resulting in systems that improve both their robustness and their energy efficiency. A basic Brayton cycle consists of three components: compressor, combustor and turbine. Brayton and Rankine cycles produce power by using energy in the working fluid, water and air respectively, via thermodynamic processes. These modifications decrease the amount of total heat energy required for system functioning. State point data for the basic Rankine cycle of Fig 1 is given in Table 2. Investigation, UNILAB Research Center for Chemical Reaction Engineering, CHINA, Received: July 21, 2019; Accepted: December 10, 2019; Published: December 31, 2019. 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. https://doi.org/10.1371/journal.pone.0226993.g005, https://doi.org/10.1371/journal.pone.0226993.g006, https://doi.org/10.1371/journal.pone.0226993.g007. (a) Energy flow diagram, (b) Ecological flow matrix. Currently, there are no standard system level measures of robustness and sustainability for human networks that take into account both the topology and flow organization. Designing for robustness is a common goal across many disciplines that deal with systems, for example design theory and methodology. The strong correlations between thermal efficiency and the ecological measures AMI and H suggest that similar fundamental principles may govern the development of ecosystems and human systems. No, Is the Subject Area "Shannon index" applicable to this article? Competing interests: The authors have declared that no competing interests exist. All of the thermodynamic cycles investigated here in contrast have higher values of ASC/DC, ranging from 0.57 to 0.81. Their is also a precedent for their use to help understand engineering meaning in ecosystem characteristics in a past publication [30]. The extra component added to the basic Brayton cycle, as seen in Fig 8, does not require any additional energy input (the new actor ii—heat exchanger, going from Fig 8a to 8b). Generally increasing and decreasing trends are seen for ASC/DC and R, respectively, with increasing efficiencies, with some exceptions. Translating this flow-based ecosystem robustness into an engineering context supports the creation of new robust and sustainable design guidelines for engineered systems. The uncertainty that researchers face in specifying their estimation model threatens the validity of their inferences. Pathway efficiency and redundancy are measured by the ENA metrics ascendency (ASC) and development capacity (DC) (given by Eqs 8 and 10). Whether it be uncertainty about the population or sample, measurement, the set of explanatory variables and their functional form, causal or temporal heterogeneity, or effect dynamics or spatial dependence, this book provides guidance and offers tests that researchers from across the social sciences can employ in their own research. (4) This inconsistent trend in the Rankine cycle modifications, one that is not seen for the Brayton cycles, could be due to the relatively small increases in thermal efficiency between the different Rankine cycles. All the thermodynamic cycles investigated here lie to the right of the window, suggesting that they have a lower robustness compared to ecosystems resulting from relatively high pathway efficiency (higher ASC/DC values).
Robustness is zero when the ratio ASC/DC is zero and one. These ecosystems however are vulnerable to disturbances: every pathway is crucial and if lost will result in some consumer need not being met. (11). 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. After this first modification though the relationship is positive. The process is set up to result in the creation of an thermodynamics-based understanding of these ecosystem measures.

The file will be sent to your email address. 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. 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).
Discover a faster, simpler path to publishing in a high-quality journal. 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). broad scope, and wide readership – a perfect fit for your research every time.