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Abstract In this paper, a novel configuration of microgrid with incorporation of turbo-expander (TE) has been presented. The cooling and electrical energy recovered by TE are used to supply the microgrid demand. The purification and preheating processes are imbedded on the inlet gas, which, according to the need, provide and control the recovery of electrical energy and cooling. Due to the unique features and limitations of TE, determination of type and optimal size of energy resources in this microgrid is special; so an innovative optimal capacity sizing (OCS) method was presented. For determination of optimal size of TE, the constraints and needs of the local natural gas (NG) network should also be considered, which, differentiates it from other energy sources. Another key feature of the proposed OCS method is optimization of inlet NG temperature passing through TE. Performance and economic evaluation of the TE-based microgrid was compared with the traditional microgrid without TE. Analysis showed that O&M and emission costs of the TE-based microgrid were reduced significantly (about 27% and 30%, respectively) culminating in low prices for the generated energies. In addition, net present value and internal rate of return of the TE-based microgrid were higher (38.5% and 6%, respectively).

Abstract In this paper, a novel configuration of microgrid with incorporation of turbo-expander (TE) has been presented. The cooling and electrical energy recovered by TE are used to supply the microgrid demand. The purification and preheating processes are imbedded on the inlet gas, which, according to the need, provide and control the recovery of electrical energy and cooling. Due to the unique features and limitations of TE, determination of type and optimal size of energy resources in this microgrid is special; so an innovative optimal capacity sizing (OCS) method was presented. For determination of optimal size of TE, the constraints and needs of the local natural gas (NG) network should also be considered, which, differentiates it from other energy sources. Another key feature of the proposed OCS method is optimization of inlet NG temperature passing through TE. Performance and economic evaluation of the TE-based microgrid was compared with the traditional microgrid without TE. Analysis showed that O&M and emission costs of the TE-based microgrid were reduced significantly (about 27% and 30%, respectively) culminating in low prices for the generated energies. In addition, net present value and internal rate of return of the TE-based microgrid were higher (38.5% and 6%, respectively).

Abstract This study presents an optimal power management for a microgrid (MG) in distribution market environment. The MG operator is able to have interactions with the distribution market operator (DMO) and adjacent MG (AMG) operator to supply its local loads. The DMO regulates the electricity market, and assigns the electricity price and power profile for the MG. The motivation behind the use of The DMO is that it works as an entity between MG and independent system operator (ISO) in order to guarantee a flexible operation by reducing power fluctuation and reduce the unintentional peak loads in low market price hours. The unused power capacity in AMG is used during the islanded hours through an additional interconnection point connected to the MG. Using this method reduces the need for installing new generation resources, which will be a practical and economical solution for MG developer. This MG which is able to provide power from distribution market and the AMG with two interconnection points is named dependent MG (DMG). A market-based stochastic model containing distribution market constraints and AC power flow formulations employs conditional value at risk (CVaR) methodology to capture the loads and wind uncertainties. The effectiveness of the presented model is evaluated on a 20 kV test system using different case studies. In this test system, the operator is the owner of all generation units. The numerical analysis explicate that presented model reduces the operation cost of DMG with the aim of responsive loads, unused power capacity, energy storage system (ESS) and power generation units. The market-based scheduling also provides operational flexibility for distribution system by adjusting flexibility limit of market constraints. It is also shown that changing risk preferences level changes the power generation pattern in ESS and causes a costly operation of resources in risk-averse strategy. The competence of this model is significant when the preventive maintenance (PM) program is carried out, and the DMG should rely on its flexible resources and AMG’s available power capacity, which could reduce the load shedding.

Abstract This study presents an optimal power management for a microgrid (MG) in distribution market environment. The MG operator is able to have interactions with the distribution market operator (DMO) and adjacent MG (AMG) operator to supply its local loads. The DMO regulates the electricity market, and assigns the electricity price and power profile for the MG. The motivation behind the use of The DMO is that it works as an entity between MG and independent system operator (ISO) in order to guarantee a flexible operation by reducing power fluctuation and reduce the unintentional peak loads in low market price hours. The unused power capacity in AMG is used during the islanded hours through an additional interconnection point connected to the MG. Using this method reduces the need for installing new generation resources, which will be a practical and economical solution for MG developer. This MG which is able to provide power from distribution market and the AMG with two interconnection points is named dependent MG (DMG). A market-based stochastic model containing distribution market constraints and AC power flow formulations employs conditional value at risk (CVaR) methodology to capture the loads and wind uncertainties. The effectiveness of the presented model is evaluated on a 20 kV test system using different case studies. In this test system, the operator is the owner of all generation units. The numerical analysis explicate that presented model reduces the operation cost of DMG with the aim of responsive loads, unused power capacity, energy storage system (ESS) and power generation units. The market-based scheduling also provides operational flexibility for distribution system by adjusting flexibility limit of market constraints. It is also shown that changing risk preferences level changes the power generation pattern in ESS and causes a costly operation of resources in risk-averse strategy. The competence of this model is significant when the preventive maintenance (PM) program is carried out, and the DMG should rely on its flexible resources and AMG’s available power capacity, which could reduce the load shedding.

Abstract In this study, the potential of developing 5 MW gird-connected PV power plants in eight selected cities in the southern coast of Iran is evaluated from technical, financial and environmental viewpoints. Different sun-tracking modes including fixed tilt, 1-axis and 2-axis systems are investigated. A sensitivity analysis is conducted to examine the impact of different important parameters and identify when investment is more profitable. The results demonstrate that development of proposed PV plants is very promising in all cities and using 1-axis tracking system is the most economical option. Under current guaranteed feed-in tariff (FIT) in Iran, the levelized cost of electricity for fixed tilt, 1-axis and 2-axis tracking modes PV plants for all cities are obtained in the range of 112.3–125.6 $/MWh, 103.0–117.3 $/MWh and 107.2–122.5 $/MWh, respectively. The analysis shows that other financial incentives such as a bank loan and carbon credit substantially improve the economic attractiveness of the project. The calculated CO2 emission abatement and external cost saving due to employment of the PV plants demonstrate that the proposed PV projects have appealing environmental benefits. This study shows that the southern coast of Iran has a huge potential and actual market opportunities for investors to develop grid-connected PV projects.

Abstract In this study, the potential of developing 5 MW gird-connected PV power plants in eight selected cities in the southern coast of Iran is evaluated from technical, financial and environmental viewpoints. Different sun-tracking modes including fixed tilt, 1-axis and 2-axis systems are investigated. A sensitivity analysis is conducted to examine the impact of different important parameters and identify when investment is more profitable. The results demonstrate that development of proposed PV plants is very promising in all cities and using 1-axis tracking system is the most economical option. Under current guaranteed feed-in tariff (FIT) in Iran, the levelized cost of electricity for fixed tilt, 1-axis and 2-axis tracking modes PV plants for all cities are obtained in the range of 112.3–125.6 $/MWh, 103.0–117.3 $/MWh and 107.2–122.5 $/MWh, respectively. The analysis shows that other financial incentives such as a bank loan and carbon credit substantially improve the economic attractiveness of the project. The calculated CO2 emission abatement and external cost saving due to employment of the PV plants demonstrate that the proposed PV projects have appealing environmental benefits. This study shows that the southern coast of Iran has a huge potential and actual market opportunities for investors to develop grid-connected PV projects.

Diminishing fuel resources and stringent emission mandates have demanded cleaner combustion and increased fuel efficiency. Three water addition rates, i.e., 2, 4, and 6 wt% in biodiesel-diesel blend (B5) was investigated herein. Combustion characteristics of the emulsified fuel blends were compared in a naturally-aspirated diesel engine at full load and different engine speeds. More specifically, biodiesel was produced from waste cooking oil (WCO) and to further increase waste utilization, recycled biodiesel wastewater was used as additive in B5. The result obtained showed that low-level water addition (i.e., 2 and 4 wt%) in B5 led to different results from those obtained using higher water addition rates (i.e., >5 wt%) reported by the previous studies. In more details, the findings of the present study revealed that low level water addition in B5 could considerably reduce CO, HC, CO2, and NOx emissions. Among water-containing B5 fuel emulsions, the optimal water addition level in terms of engine performance parameters and emissions was found at 4 wt%. In particular, the emitted CO2, HC, and NOx were decreased by over 8.5%, 28%, and 24%, respectively, at maximum speed of 2500 rpm.