فصلنامه مهندسی و مدیریت انرژی
سال سیزدهم شماره 1 (پیاپی 47، بهار 1402)

This paper presents a platform for power autonomous wireless energy meter device using piezoelectric energy harvesters. This device can be mainly used for measuring the share of heat energy consumption in a fair manner in building complex with central heat energy system. In the suggested device, the piezoelectric energy harvester is also used as a flow-meter to reduce the power consumption of the device which facilitates power autonomous operation of the device. The performance of the devices is investigated based on a prototype which is used under a test condition with flow rate from 100 up to 200 liters per hour. Comparing the test results with those of recorded based on a standard hall-effect flow meter as a reference sensor verifies the multi-function operation of piezoelectric energy harvester as a flow sensor within the device.

This paper deals with the control and stability enhancement of a wind power generation system feeding active load with constant power characteristic. The under study system is a combined wind-battery generation system with permanent magnet synchronous generator (PMSG) supplying active load by using interfaced power electronics converters. The employed active load is indeed an active rectifier behaving such as a constant power load (CPL). Since CPLs from the small-signal point of view behave such as negative resistances, they result in stability margin reduction and even system instability at higher load power penetration. In this paper, as the novelty, a control approach is presented resulting in system stability at presence of active loads. In other words, by using the proposed control method, the output impedance of the load-side converter at low frequencies converge to zero, and this in turn results in system stability margin improvement under presence of active loads. At the end, performance of the study system with active loads is examined by time domain simulations and with/without proposed control method.

This article is an introduction of a new topology of current source inverter (CSI) which can be alternatively implemented in low/medium power applications. This configuration is organized from series connected sub-multilevel inverters blocks. The basis of the recommended multilevel topology is the connections of many cell units in a decent scheme with the help of H-bridge inverter. The suggested inverter produces desired DC current levels with the value of positive and negative. In the recommended configuration, the number of DC current sources, switches and the related gate drive circuits in comparison with the traditional multilevel inverters are lowered. Consequently, cost and volume is decreased in the suggested topology. In order to investigate the suggested structure of the multilevel inverter, the simulation and experimental results for a single-phase 7-level inverter are prepared and indicated.

In this paper, a new method for detection and fault location and classification in MTDC solar microgrid is presented. Some issues such as expanding renewable energy sources and DC loads and efforts to increase power quality and reduce the environmental impact of electricity generation have led to the expansion of solar networks. Identifying the types and locations of faults is important to ensure service continues and to prevent further breakdowns and the increasing the protection’s selectivity characteristic. In this method, an orbital kit is connected to the network. In the fault occurrence time in the network, the fault is detected by passing a current through the connected kits and measuring the traveling waves derived from the fault current, and applying it to a mathematical morphological filter The location of the error is determined using orbital equations and flow calculations. Mathematical morphology filter output and signal energy analysis were used to determine the type of faults. The method presented in an MTDC microgrid connected to energy storage and renewable sources was tested with many faults. The results indicate the accuracy of the proposed method. This method is resistant to changes in arcs resistance (up to 100 ohms), and has a very good performance in high impedance faults conditions(up to 1000 ohms).

In this paper, an effective method for fault detection and classification in a double-circuit transmission line compensated with TCSC is proposed. The mutual coupling of parallel transmission lines and presence of TCSC affect the frequency content of the input signal of a distance relay and hence fault detection and fault classification face some challenges. One of the most effective methods for fault detection and classification in a compensated line is pattern-recognition methods. Prerequisites for the optimal using of these methods are the extraction and selection of appropriate features to feed the classifier. In this paper, wavelet transform as a signal processing tool to extract features is used. Due to variety of mother wavelets, firstly the best mother wavelet is identified by using a new method and the feature vector is made by the coefficients obtained from the best mother wavelet. After this stage, decision tree, support vector machines, and k-nearest neighbor as the classifies are trained by feeding the feature vector. Then, their accuracies are evaluated against different simulation scenarios to select the best classifier which has the best performance among others. In this paper, the sample system and the proposed method is implemented in MATLAB environment.

This paper investigates the connection of a single-phase multilevel inverter structure to an existing power grid. The applied voltage source inverter is able to generate a near sinusoidal voltage waveform with an amplitude six times the input voltage by using a single DC input power supply. A proportional-resonant (PR) controller regulates the injected current into the grid. While the EPLL is used to ensure the synchronization of the phase and frequency of the output voltage with the grid. The performance of the grid-connected inverter under different loading conditions was simulated in MATLAB software. Finally, the simulation results were compared with the experimental ones. In addition, the behavior of the inverter in standalone operating mode supplying a local load as well as its performance in the grid-tied with a constant and variable current reference was evaluated. The correct operation of the inverter in all operating modes an achieving 96.9% efficiency along with the self-voltage balancing of the capacitors, makes it suitable for grid-integration of the low voltage renewable energy sources’ applications.

Employing non-conventional water resources using treatment and recycling is considered as the main resource in addressing future water scarcity. Although non-conventional water recycling has been investigated in details in the literature, its impacts on irrigation-fertilizing systems have not been discussed using thermoeconomic analysis.  In this case study, using a hydroponic greenhouse system for rose cultivation, exergoeconomic cost was investigated in a recycling process by comparing three system including: open cycle, open cycle considering exergy abatement cost, and close cycle (nutrition water recycling). Results show that the exergoeconomic cost for producing 212,500 rose cut-flowers in a 6-months cold period, where heat was supplied by boiler for the above mentioned scenarios were about 15,760 $, 16,525 $ and 14,718 $, respectively. Also, the thermoeconomic indicator of the unit exercoeconomic costs for above mentioned scenarios were 74.2, 77.8 and 69.3 $Gj-1, respectively. In the close cycle, drainage water recycling decreased total exergy losses by 4.02 Gj.yr-1, of which 1.24 Gj.yr-1 reduction was due to the reduced inlet water and 1.91 Gj.yr-1 for the inlet fertilizer reduction, while that increased by the system electricity consumption was 1.12 Gj.yr-1. Water quality pyramid presented based on the unit exergoeconomic cost indicated 459.9 Gj.yr-1 for the nutrition feed  as the highest peak value and zero for the wastewater at the base of the pyramid.

A complete understanding of the limits, barriers, and equipment available for the use of national energy resources is essential. This will increase the use of existing regional energy potential and pave the way for sustainable development. In this study, the Green Cottage power management system from a renewable energy source was designed and evaluated using a decision-making algorithm. Thirteen scenarios were extracted to Zero-energy building. The results show: If the penetration of renewable energy is 24% with an average daily fossil fuel consumption of 1.11 liters per year, the energy produced by the Hybrid renewable energy systems (HRES) is equal to 1697 kWh / yr and the net present value (NPV) is $ 5553.68 and the Internal rate of return (IRR) equals 21.49% with a payback period (PP) of 15.71 years. With the increase of renewable energy penetration to 54%, fossil fuel consumption became 0.694 liters and the annual production energy was equal to 1652 kWh / yr and the NPV was 19.5% with a PP of 17.61 years. Zero-energy building Energy Management with 100% renewable energy penetration, 1933 kWh / yr per year without emissions of environmental pollutants, and the NPV equal to -372.09 dollars. From the point of view of energy policy, if the feed-in tariff of renewable energy increases to more than $ 0.06, the implementation of this scenario will be economic.

In order to improve the thermal management system for cooling an electric vehicle battery pack, the thermal performance of the battery pack in two states of charge and discharge in different working conditions by using a copper sheath around the batteries and a copper sheath, as well as a stair channel on top of the battery pack and using of nanofluid as cooling fluid, has been studied using numerical simulation. The thermal model for the battery pack with 71 cylindrical lithium-ion batteries, model 18650, has been investigated. To develop this model, the thermal behavior of the battery set has been studied and the effect of variables such as electric current rate on both charge and discharge processes, fluid flow rate, addition of copper oxide nanoparticles to water-based fluid, change of contact surface between neighboring batteries and creation The wave channel for the batteries has been investigated. Numerical simulation results confirm the useful effect of the cooling system. The simulation results show that increasing the electric current rate increases the temperature and decreases the uniformity of temperature distribution in the battery pack. For this purpose, some changes have been made to improve the thermal performance of the battery. Increasing the volume percentage of nanoparticles causes a decrease in the maximum temperature and temperature difference in the battery assembly and leads to an improvement in the thermal performance of the cooling system. Also, increasing the fluid flow rate reduces the maximum temperature and improves the temperature uniformity in the battery pack. With increasing coolant inlet flow rate, 7.7% and 12.5% decrease in maximum temperature and temperature difference in the charge discharge process are observed in the battery pack, respectively. Finally, increasing the contact surface between the batteries and the wave channel from 37 degrees to 57 degrees can reduce the temperature difference and maximum temperature in the battery set by 5.2 and 52.3 percent, respectively, but the temperature uniformity in the set has an adverse effect.

In this study, the influence of type and structure of different roofing systems were investigated using computational fluid dynamic method. The considered roofing systems include beam and block types (clay brick, light weight concrete block, polystyrene) and Uboot slab which were designed for 6m and 8m span. To simulate the fluid flow and heat transfer, the computational fluid dynamic method was employed based on control volume scheme. Heat transfer inside air cavities is carried out via free convection and radiation while heat transfers via conduction within solid walls. The thermal simulation of the roofing systems was analyzed for both summer (downward heat flow) and winter (upward heat flow). Two dimensional natural heat transfer was considered to be transient with laminar and incompressible flow inside cavities. To assess the thermal performance of the flooring systems, equivalent thermal conductivity, decrement factor and time lag were studied. Finally, the best roofing system was introduced in terms of heat transfer and thermal mass efficiency. The results showed that the roof with polystyrene block has the lowest value of equivalent thermal conductivity and Uboot system has the highest heat loss among the studied cases.