scholarly journals Total System Performance Ratio—A Systems Based Approach for Evaluating HVAC System Efficiency

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5108
Author(s):  
Supriya Goel ◽  
Michael Rosenberg ◽  
Juan Gonzalez ◽  
Jérémy Lerond
Keyword(s):  
System Performance ◽  
Software Tool ◽  
The United States ◽  
Performance Ratio ◽  
System Evaluation ◽  
Total System ◽  
Hvac System ◽  
System Efficiency ◽  
Heating And Cooling ◽  
Code Structure

The prescriptive path is the most widely used approach for commercial code compliance in the United States. Though easy to implement, prescriptive approaches do not typically discriminate between minimally compliant, high-performing and poorly performing HVAC system configurations. Hence, to meet aggressive energy and carbon reduction goals, it is clear that energy codes will need to transition from prescriptive to performance-based approaches, a transition that is riddled with several challenges. This paper discusses a new HVAC system-based performance approach (HVAC System Performance) which provides a simpler solution to HVAV system evaluation compared to whole building performance, while keeping tradeoffs limited to specific building systems. The Total System Performance Ratio (TSPR) is a metric for evaluation of overall system efficiency instead of individual component efficiency, a solution which could also eventually facilitate the transition to a 100% performance-based code structure. TSPR is a ratio that compares the annual heating and cooling load of a building to the annual energy consumed by the building’s HVAC system. A calculation software tool has been developed for determining a building’s TSPR. Already incorporated into the 2018 Washington State Energy Code, this approach is also being evaluated by ASHRAE Standard 90.l Project Committee and has the potential to provide a comprehensive performance-based approach for HVAC system evaluation and analysis.

Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

2009 ◽  
Author(s):  
Michael B. Rannow ◽  
Perry Y. Li
Keyword(s):  
Hydraulic System ◽  
Check Valve ◽  
Fluid Flows ◽  
Soft Switching ◽  
Total System ◽  
System Efficiency ◽  
Hydraulic Systems ◽  
Controlled Systems ◽  
Flow Through ◽  
Hydraulic Valve

A method for significantly reducing the losses associated with an on/off controlled hydraulic system is proposed. There has been a growing interest in the use of on/off valves to control hydraulic systems as a means of improving system efficiency. While on/off valves are efficient when they are fully open or fully closed, a significant amount of energy can be lost in throttling as the valve transitions between the two states. A soft switching approach is proposed as a method of eliminating the majority of these transition losses. The operating principle of soft switching is that fluid can temporarily flow through a check valve or into a small chamber while valve orifices are partially closed. The fluid can then flow out of the chamber once the valve has fully transitioned. Thus, fluid flows through the valve only when it is in its most efficient fully open state. A model of the system is derived and simulated, with results indicating that the soft switching approach can reduce transition and compressibility losses by 79%, and total system losses by 66%. Design equations are also derived. The soft switching approach has the potential to improve the efficiency of on/off controlled systems and is particularly important as switching frequencies are increased. The soft switching approach will also facilitate the use of slower on/off valves for effective on/off control; in simulation, a valve with soft switching matched the efficiency an on/off valve that was 5 times faster.

Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Michael B. Rannow ◽  
Perry Y. Li
Keyword(s):  
Hydraulic System ◽  
Check Valve ◽  
Fluid Flows ◽  
Soft Switching ◽  
Total System ◽  
System Efficiency ◽  
Hydraulic Systems ◽  
Controlled Systems ◽  
Flow Through ◽  
Hydraulic Valve

A method for significantly reducing the losses associated with an on/off controlled hydraulic system is proposed. There has been a growing interest in the use of on/off valves to control hydraulic systems as a means of improving system efficiency. While on/off valves are efficient when they are fully open or fully closed, a significant amount of energy can be lost in throttling as the valve transitions between the two states when the switching times are not negligible. A soft switching approach is proposed as a method of eliminating the majority of these transition losses. The operating principle of soft switching is that fluid can temporarily flow through a check valve or into a small chamber while valve orifices are partially closed. The fluid can then flow out of the chamber once the valve has fully transitioned. Thus, fluid flows through the valve only when it is in its most efficient fully open state. A model of the system is derived and simulated, with results indicating that the soft switching approach can reduce transition and compressibility losses by 81% and total system losses by 64%. The soft switching approach has the potential to improve the efficiency of on/off controlled systems and is particularly beneficial as switching frequencies are increased. The soft switching approach will also facilitate the use of slower on/off valves for effective on/off control; in simulation, a valve with soft switching matched the efficiency of an on/off valve that was 4.4 times faster.

Investigation of Accumulator Parameters for a Novel Hybrid Architecture

2020 ◽  
Vol 32 (5) ◽  
pp. 876-884
Author(s):  
Seiji Hijikata ◽  
Kazuhisa Ito ◽  
Hubertus Murrenhoff ◽  
◽  
Keyword(s):  
Hybrid System ◽  
Energy Savings ◽  
Combustion Engine ◽  
Pressure Level ◽  
Operating Costs ◽  
Hybrid Architecture ◽  
Total System ◽  
System Efficiency ◽  
Pressure System ◽  
Gas Volume

An open center system (OC-System), which is one of the major hydraulic architectures for excavators, has been improved in the world to reduce fuel consumption for global environment conservation and lower operating costs. However, the total system efficiency, including the internal combustion engine (ICE), has not been thoroughly considered. In contrast, a constant pressure system (CP-System) enabling the engine to be driven optimally is developed, but is not accepted in the industry owing to the complexity of the required components. Thus, in this research, a hybrid system combining an OC-System with a CP-System is proposed to improve the total system efficiency. An accumulator, which is used to provide flow rate to actuators, is essential for the new hybrid system, and it is vital to consider the nominal gas volume and pressure level for the accumulator in terms of energy savings and initial cost. Therefore, the influences of accumulator volume and pressure level are discussed in this paper.

Simulation of Utilisation of Pressure Propagation for Increased Efficiency of Secondary Controlled Discrete Displacement Cylinders

2012 ◽  
Vol 233 ◽  
pp. 3-6 ◽  
Author(s):  
Rico H. Hansen ◽  
Anders Hansen ◽  
Torben O. Andersen
Keyword(s):  
Power Systems ◽  
Energy Efficient ◽  
Discrete Control ◽  
Total System ◽  
System Efficiency ◽  
Discrete Variation ◽  
Minimum Loss ◽  
Fluid Power Systems ◽  
Fixed System ◽  
Pressure Propagation

A key component of upcoming secondary controlled fluid-power systems for e.g. wave energy is the implementation of discrete force control of cylinders by discrete variation of the cylinder displacement. However, as the discrete control is implemented by shifting between fixed system pressures in multiple cylinder chambers using on/off valves, the energy efficiency of the performed shifts is essential for the total system efficiency. However, pressure shifting on a volume, where the dynamics of pressure propagation in the pipelines is negligible have been proved to have an unavoidable minimum loss due to the compressibility of the fluid. This paper performs a simulation study, showing that an improved energy efficient shift may be implemented by utilising the pressure propagation in the line between valve and cylinder chamber.

scholarly journals Fuel Utilization Effects on System Efficiency and Solid Oxide Fuel Cell Performance in Gas Turbine Hybrid Systems

2017 ◽  
Author(s):  
Nor Farida Harun ◽  
Lawrence Shadle ◽  
Danylo Oryshchyn ◽  
David Tucker
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Cell Length ◽  
Inlet Temperature ◽  
Total Efficiency ◽  
Total System ◽  
System Efficiency ◽  
Fuel Utilization ◽  
Fuel Cell Performance

The simulation work presented herein characterizes the performance of a recuperated gas turbine (GT) hybrid systems in response to different levels of fuel utilization (Uf) by the SOFC. The SOFC performance was compared with and without anode recycle (AR), operating at 90% total stack Uf (Uf.stack). A study at 65% Uf was also considered as a reference case for the hybrid power system without anode recycle, i.e. using single-pass cell fuel utilization (Uf.cell). All three cases in this paper were evaluated at design points for a 550 MW hybrid system using coal-derived syngas feed with zero methane. A previously developed one-dimensional (1D) fuel cell model was used to simulate the distributed profile of thermal and electrochemical properties along the fuel cell length. Fuel cell total current density, average solid temperature, and cathode inlet temperature were maintained identical at each fuel utilization to avoid confounding the results with the impacts of SOFC degradation. The maximum system efficiency of 71.1% was achieved by SOFC/GT non-recycle systems at 90% Uf.cell (with 90% Uf.stack). The case at 65% Uf.cell (with 65% Uf.stack) demonstrated 70.7% total efficiency, only 0.4% point lower than at 90% Uf.cell. However, integrating anode recycle to the system significantly reduced the maximum total efficiency to 55.5%. Although the distributed SOFC performance across the cell length for 65% Uf.cell with AR at 90% Uf.stack was similar to the 65% Uf.cell (with 65% Uf.stack), recycling anode off-gas resulted in lower fuel cell Nernst potential that caused further drop in both stack and total system efficiency.

Reworks: A robust system efficiency measure

2018 ◽  
Vol 18 (3) ◽  
pp. 183-191 ◽  
Author(s):  
Ralph Renger ◽  
Brain Keogh ◽  
Andrew Hawkins ◽  
Jirina Foltysova ◽  
Eric Souvannasacd
Keyword(s):  
Standard Operating Procedure ◽  
Technology Leadership ◽  
System Evaluation ◽  
System Efficiency ◽  
Efficiency Measure ◽  
Think Tank ◽  
Evaluation Theory ◽  
Universal System ◽  
Efficiency Measures ◽  
Proxy Measure

The article reports on the inaugural Australian-American system evaluation summit convened in Wyoming, USA, focusing on the application of system evaluation theory (SET). The think tank noted SET’s efficiency principles and published illustrations are emergency response sector specific and pondered whether efficiency measures could be identified for systems targeting complex social problems. The article describes how the think tank used the concept of system waste as a springboard to identify reworks as a universal system efficiency measure. Reworks were defined as repeating all or part of a system standard operating procedure (SOP) or adding additional steps to the SOP to satisfy externalities to the primary purpose. The article then describes the think tank conclusions regarding the utility of reworks as a proxy measure for the four SET factors influencing system efficiency: training, information technology, leadership and culture. The think tank concludes with a discussion of the cautions evaluators should observe when interpreting reworks.

scholarly journals Thermodynamic analysis of air refrigerator on exergy graph

2006 ◽  
Vol 10 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Vladimir Nikulshin ◽  
Margaret Bailey ◽  
Viktoria Nikulshina
Keyword(s):  
Thermodynamic Analysis ◽  
Exergy Efficiency ◽  
Total System ◽  
Individual Element ◽  
System Efficiency ◽  
Innovative Method ◽  
Loss Models ◽  
The Relationship ◽  
Exergy Losses ◽  
Intensive System

Improving mechanical system efficiency is the goal of many engineers and scientists. Commonly, the solutions to these types of problems are uncovered using thermodynamic analysis and optimization. An innovative method for the thermodynamic analysis of a complex energy-intensive system with an arbitrary structure is described in this paper. The method is based on a novel general equation to calculate the total system exergy efficiency using an exergy flow graph proposed by the authors. Discuss in this paper exergy efficiency and exergy loss models as well this approach allows a user to obtain not only the exergy losses and efficiency of the total system, but also to show the relationship between the exergy efficiency of an individual element and that of the entire system. An example is provided that employs this method to the thermodynamic analysis of an air refrigerator.

Illustrating the Evaluation of System Feedback Mechanisms Using System Evaluation Theory (SET)

2016 ◽  
Vol 16 (4) ◽  
pp. 14-20 ◽  
Author(s):  
Ralph Renger
Keyword(s):  
Evaluation Criteria ◽  
System Evaluation ◽  
Cardiac Care ◽  
System Efficiency ◽  
Evaluation Theory ◽  
Feedback Mechanisms ◽  
Key Factor ◽  
Response Systems ◽  
Post Hoc ◽  
Care Response

This article describes how system evaluation theory (SET) guided the evaluation of cardiac care response systems efficiency in seven rural United States. Specifically, the article focuses on the approach and methods used to evaluate system feedback mechanisms; one key factor affecting system efficiency. Mixed methods were applied to evaluate five criteria of system feedback efficiency: frequency, timeliness, credibility, specificity, and relevance. Examples from the cardiac care response system evaluation are used to illustrate each of the evaluation criteria. The discussion contrasts the role of the evaluator in system versus program evaluation, notes the post-hoc support of SET system attributes in affecting system efficiency, and offers additional consideration in evaluating system feedback mechanisms.

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