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## Investigation of a Geothermal-Based CCHP System from Energetic, Water Usage and CO2 Emission Viewpoints | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Gas Processing Journal | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

مقاله 4، دوره 7، شماره 1، فروردین 2019، صفحه 41-52 اصل مقاله (841.72 K)
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شناسه دیجیتال (DOI): 10.22108/gpj.2019.118131.1058 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

نویسندگان | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Mahmoud Mohsenipour^{*} ؛ Farzin Ahmadi؛ Amir Mohammadi؛ Mohammad Ebadollahi؛ Majid Amidpour
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^{}Department of Energy Systems, Mechanical Eng. Faculty, K. N. Toosi University of Technology, Tehran, Iran | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

چکیده | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Renewable heat sources are a sustainable and clean way to produce power, heating, and cooling. Combined cooling, heat, and power (CCHP) systems are very promising for producing demands simultaneously. In the present study, a CCHP system with the geothermal source has been investigated, and heat loads are designed for the micro-scale application. To determine the feasibility of the system, energy analysis is carried out, and results are reported after optimization. Also, the genetic algorithm method is presented for optimization. The sub-objectives of this study are the calculations of water usage and CO_{2 }emission in the manufacturing process. For this matter, energy efficiency, water usage, and CO_{2} emission after optimization have been examined as three significant parameters. The efficiency of the system, water usage, and CO_{2} emission are reported as 46.4%, 688151.2 (lit) and 13439 respectively. The total purchase cost is 43121 $. Moreover, the results show that between components the maximum water usage in manufacturing and CO_{2} emission is belonged to vapor generator with 242010 (lit) and 4701 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

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Geothermal؛ Energy Efficiency؛ Water Usage؛ Carbon DIoxide Emission؛ CCHP؛ Genetic Algorithm؛ Optimization | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

اصل مقاله | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

Energy efficiency has been a great deal of attention because of increased energy prices, shortage of resources, and environmental limitations [1]. International Energy Agency examines different scenarios based on energy technologies, which presented that energy efficiency has a significant role in all choices concerning carbon dioxide reduction [2]. Thus, energy efficiency has an essential part of sustainability development. Multi-generation systems consider as a promising energy-efficient technology; which concludes the simultaneous production of two or more energy agent in a specific integrated process. Combined cooling, heat, and power (CCHP) is one type of multi-generation systems so-called tri-generation. CCHP indicates that power and valuable heat are produced at the same time, along with cooling, which is possible by utilizing the additional surplus heat that would be wasted in conventional technologies. For this reason, Yi In the present paper, the optimization of a CCHP with the combination of ORC, ERC, and geothermal heat source has been studied. In literature, the lack of research on the relations between the water and CO
The CCHP system with R134a as its working fluid driven by the geothermal source has consisted of two subsystems: (i) the heat source and (ii) the CCHP subsystem. The schematic illustration of the integrated system is demonstrated in Fig. 1. In the heat source subsystem, the LTW (Low-Temperature Well) of Sabalan geothermal has been used as the primary heat source for the vapor generator. The inlet temperature and pressure of this stream are 438 K and 700 kPa respectively [26].
The CCHP consists of these components: vapor generator, turbine, evaporator, heater, regenerator, condenser, ejector, feed pump, and throttling valve. In the vapor generator, the working fluid at the liquid phase is evaporated to super-heated vapor via absorbing heat from the geothermal source. Then, it divides to three streams: one outlet enters the heater for the heating purpose, other flows through the supersonic nozzle of the ejector while the other expands by the turbine for generating power. A high vacuum can be formed by the rapid flow at the nozzle terminal while taking a secondary flow from the evaporator into the chamber. Two streams are mixed in the chamber then flow throughout the diffuser of the ejector. Then, Exhaust of the turbine and Outlet stream of the ejector are combined into the mixer (2) before flowing through the condenser. In the condenser, the fluid is condensed to a saturated liquid by rejecting heat into the ambient. One branch of the exit condenser flows throughout a throttle valve and inserts to the evaporator, while the other one flows across the mixer (1) after being pumped. Afterward, the liquid is pumped to the vapor generator to complete a whole cycle. Generally, the present CCHP system could be operated under three different conditions. In a warm climate like summer, when the need for cooling and power are presented, the heating branch is not operating, and the system works as a combined cooling and power (CCP). In winter, the system can be switched to the combined heating and power (CHP) mode, which cuts off the cooling branch. In some applications, when neither heating nor cooling needed, the system could produce only power.
In this section, the mathematical modeling of the examined CCHP is described with details. The energy balances in the components, the mass flow rate balances, and the outputs definitions are specified. Furthermore, all the assumptions are clarified to model the proposed system from thermodynamics viewpoint in a convenient way. Following considerations have been made in this investigation to simulate the cycle appropriately: - · All components operate at a steady-state condition.
- · The ambient temperature and pressure have been considered at 298.15 K and 1.01 bar, respectively.
- · Isentropic efficiency of the turbine and pump are assumed to be 95% and 90% respectively.
- · The thermal efficiency of the heat exchanger is presumed to be 80%, and terminal temperature difference in heat exchangers is presumed 10 K.
- · The kinetic energy in the inlet and outlet of the control volumes are neglected.
- · The ideal gas model with constant properties has been used inside the ejector in an adiabatic process.
- · Outlet streams of the evaporator, heat exchangers and condenser are taken into account as saturated fluids.
- · Inlet water enters the condenser assumed to be in ambient condition.
A control volume for each component is taken into consideration, and the first law of thermodynamics applied to assure the mass and energy conservation laws. For this matter, mass and energy balance relations can be stated as follows:
The following equations give the energy balances in the heater, condenser, and evaporator:
The following equation explains the heat exchanger operation:
The turbine is responsible for power generation. This power is taken from the generator for electricity production. Eq. (7) describes the isentropic efficiency definition of the turbine, while Eq. (7) presents the work produced by the turbine.
Pump expands energy in order to compress and pressurize fluids. Eq. (9) describes the isentropic efficiency definition of the turbine, while Eq. (10) presents the work produced by the turbine.
The ejector has the capability of transportation and compressing a bulk of induced fluid from the suction pressure to the exit pressure. Liu
: Suction efficiency, : Primary nozzle efficiency = Diffuser efficiency, : Secondary flow pressure,
In order to assess the validity of the ejector’s simulation, the experimental data extracted from Ref. [28] for ejector parameters using R134a as working fluid is performed on the constructed mathematical representation and results are compared in Table 2. Eqs. (21) and (22) have been employed to calculate the relative error and Root Mean Square (RMS) error. Based on Table 2, the ARD errors are under 8%, which shows a good agreement with the experimental results.
Where and denote for the values of the selected parameter obtained at the chosen reference and present research, respectively.
The throttling valve is assumed as ideal, which means that the enthalpy is constant. Eq. (23) describe this assumption:
The overall efficiency of the trigeneration system is as explained in Eq. (24):
The logarithmic mean temperature difference (LMTD), and the overall heat transfer coefficient (U
The overall heat transfer coefficient for heat exchangers has been reported in Table 3.
In order to assess the component costs, the cost functions for each - are extracted from literature (see Table 4).
*Absolute relative difference for 𝜔 **Absolute relative difference for critical temperature
A proper mathematical code is written in the engineering equation solver (EES) software in order to simulate the examined system regarding the assumptions that had been described earlier. The energy analysis with the aim of the first law of thermodynamics has been examined. Genetic algorithm has been widely implemented for optimizing energy systems [32]. Thus, the genetic algorithm has been employed in this study for finding the optimum state. The parameters of the genetic algorithm method are shown in Table 5. The thermal efficiency of the system is considered as the objective function. While vapor generator pressure , evaporator pressure , heater pressure , a thermal temperature difference of vapor generator , condenser , heater , and evaporator are specified as the decision variables as described in Table 6, respectively. It has to be noted, the main goal of this optimization is the maximization of the thermal efficiency by considering a single parameter as an objective function [30].
To calculate the water usage and CO
The present study aims to investigate the energy analysis of the present CCHP system with the geothermal source by EES software. The assumptions have been made as described in Section (3) for modeling the system more accurately. For a cold environment, the demand for heat and cooling set to be 150 and 15 kW, respectively. After executing the results, a genetic algorithm has been indicated for optimizing the thermal efficiency, as explained in the previous section. The thermal efficiency of the CCHP system before and after optimization is 42.1% and 46.4% respectively. The results of the energy simulation have been reported in Table 7. With the optimized written code, the thermodynamic and mass flow rates of each state have been derived (see Table 8). The specifications of each component were calculated from modeling and energy analysis of this system. The size and material of each component are required for finding the weight of constructions. For the water usage (WU) and CO
The results of the WU and CE indicate the vapor generator as the maximum WU and CE of the system and the evaporator as the minimum. The reported WU and CE for vapor generator are 24210 litter and 4701 . While this amounts for the evaporator are 16990 litter and 330.1 respectively (Table 9). Cost evaluation is applied for different components of this system (see Table 10). According to the results, the turbine has the highest purchase cost. The system purchase cost is 43121.65 $.
A parametric study is applied to investigate the impact of , heat source temperature, and evaporator and vapor generator pressures. With increasing , the heat recovery of the vapor generator decreases, therefore, will be decreased which has a greater impact on than (Fig. 2). Similarly in case of heat source temperature, since the turbine inlet stream has more thermal energy, turbine power will be increased while heat source temperature arises. But as is shown in Fig. 3, decreased for the same reason. With increasing P
Energy efficiency depicts a significant role in the growth of sustainability. Polygeneration is a promising energy-efficient technology; the basic form of polygeneration is CHP and CCHP systems. In this paper, a CCHP system with the geothermal source has been investigated. To determine the feasibility of the system, according to energy assessment outcomes, the efficiency of the system is increased from 42.1% to 46.4% after optimization. The whole purchase cost of the system is 43121.65 $. One of the sub-purposes of this research is the calculations of water usage and CO | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

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