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Group Model Building on Qualitative WEF Security Nexus Dynamics
Published in Aries Purwanto, Grasping the water, energy, and food security nexus in the local context, 2021
WEF security definitions used in this study refers to the availability, accessibility, and quality of those three sectors. In principle, resource availability is the existence of the resources physically at a certain minimum level to meet demand, while resource accessibility is defined as the ease of accessibility of the resources by people in a region at an affordable price. Furthermore in terms of quality, water quality defined as water that meets water quality standards locally. Energy quality means that the energy generated can be utilized continuously and safely regarding the impact to the environment. Three principles of nexus approach by Hoff (2011) namely investing to sustain ecosystem services, creating more with less, accelerating access and integrating the poorest are employed in this research as the main concept in modelling qualitatively the existing condition of the study area.
In the Beginning: Soft Energy Paths
Published in David B. Brooks, Oliver M. Brandes, Stephen Gurman, Making the Most of the Water We Have: The Soft Path Approach to Water Management, 2009
Using technologies that match energy quality to end-use needs has relevance to both efficiency improvements and energy planning. This can be demonstrated by looking at the fact that a large portion of society’s end-use needs is for low quality energy in the form of low-temperature heat. (Think about raising room temperatures to comfortable levels, a matter of tens of degrees in most cases.) Using electricity generated thermally (eg, in coal- or gasfired power plants) – a high-quality form of energy – to provide these services, greatly reduces efficiency in terms of the thermodynamic potential of the fuel.
The optimal defrosting condition of an air source heat pump based on entropy analysis
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Wei Dong, Yongcun Li, Shenghua Zou
Entropy generation is a measure of irreversibility in the system. The heat exchanger is used as a thermal device that transfers energy. There is irreversibility in the heat transfer process, which causes decrease in energy quality. For the perspective of reducing the irreversible loss in the heat transfer process of the heat exchanger, the operating conditions of the heat exchanger with the least irreversible heat transfer during the operation of the system can be studied, which can effectively reduce the energy consumption of the heat exchanger during heat transfer. Therefore, the operating conditions of the heat exchanger with the least irreversible heat transfer can be studied from the viewpoint of reducing the irreversible loss in the heat transfer process of the heat exchanger. The energy loss of the heat exchanger in the heat transfer process can be effectively reduced to achieve efficient operation of the heat exchanger in low temperature environment.
Exergy Analysis and Thermodynamic Optimization of a steam power plant- Based Rankine cycle system Using Intelligent Optimization Algorithms
Published in Australian Journal of Mechanical Engineering, 2022
Samad Elahifar, Ehsanolah Assareh, Rahim Moltames
First Law of Thermodynamics is the same principle of energy conservation that the internal energy change in a closed system is the added temperature minus net work is done by machine. The first law of thermodynamics covers various forms of energy and states that the reactions of work and heat in a thermodynamic cycle cause changes in that cycle. The second law essentially states that it is not possible to obtain a process in which unique effect is a fraction of a positive heat from one source and power production is positive. Energy is followed by entropy and moves from its source. As the effect of work on changing the state of a system is greater than the influence of heat on that system, the value of work in second law of thermodynamics is more than the heat value. It means that in a thermodynamic system, the effect of work is more useful than the effect of heat. In an actual thermodynamic cycle, converting work to heat is possible but converting heat to work is very difficult and limited. (Bejan 2006). As a result, potential, ability, and talent of energy to produce useful work is the energy quality. In other words, the work potential for a certain amount of energy is defined as the maximum useful energy that energy can be achieved from it in a certain environment. The environment is considered as the basis for measuring work potential (Çengel and Boles 2002). In the context of thermodynamics, it is sometimes stated that the energy degree has been reduced that means the talent and the potential for a certain amount of energy have been fallen during that process. Due to this, the first and second law of thermodynamics are defined as the total amount of energy always remains constant and is reduced potential to produce useful work, respectively (Bejan 2006).
Investigation of the ratio of exergy consumption to energy consumption for building energy efficiency
Published in International Journal of Green Energy, 2018
Ping Wang, Guangcai Gong, Liqun Cai, Huahui Xie, Siyue Gong
The building energy system includes a lot of subsystems such as the envelope, cooling and heating resource, the air conditioning terminal, indoor air subsystem and energy supply and so on (Qinsheng 2005). The energy consumed by the building energy system is mainly coal, gas, electricity. The energy consumed by the building energy system has a dominant share in the total society energy use and causes serious environmental problems. So far a lot of researchers devoted themselves to the energy efficiency assessment of the building energy system with energy analysis method (Chandel, Sharma, and Marwaha 2016; Liu et al. 2015a). But the energy analysis for the building energy efficiency is limited in its ability to handle the quality of energy, which can be addressed by “exergy” (Schlueter and Thesseling 2009). Compared with energy analyses, exergy analyses can enable us to articulate the quality and quantity of the energy. Now the exergy method has been widely used in the study of the building energy systems (Sogut 2015). What is more, there exists lots of research studying the building energy system with both energy and exergy methods (Al Ali and Dincer 2016; Yildiz and Güngör 2009; Yucer and Hepbaslia 2011; Sakulpipatsin et al. 2010; Velmurugan and Kalaivanan 2015). Based on the energy and exergy methods, the energy quality coefficient (Jiang and Liu et al. 2004) and energy grade balance coefficient (Ki, 1996; Zhou and Gong et al. 2013) have been derived to evaluate the quality of various energy resources and energy systems. Although the energy and exergy methods are widely used in the study for the building energy efficiency, few papers combined the energy method and exergy method to bring out a comprehensive parameter to evaluate the building life cycle energy efficiency. This paper strives to find a dimensionless parameter with energy and exergy method to provide an overall assessment of the building energy efficiency, so the Ratio of Exergy consumption to Energy consumption (REXE) of the building is proposed.