Daily Power Research Articles

Numerical study on the thermal and electrical performance of a novel MCHP PV-Trombe wall system

Most of existing photovoltaic (PV)-Trombe wall systems use a single coolant which has the drawbacks of low utilization efficiency and unreasonable heat distribution of space heating. In order to address these problems, a novel micro-channel heat pipe PV-Trombe wall system is proposed in this paper. The system uses heat pipe and Trombe wall to cool the PV collector decreasing its operating temperature and thus improving the overall efficiency. Moreover, an air-cooled condenser is used to control the thermal energy transfer in the room to improve the thermal comfort. The mathematical model of the system under different operation modes is verified to investigate the performance of the system in Lhasa, Beijing and Nanjing. The results show that: (ⅰ) during the space heating mode, the average room temperature of 20.36 °C, 19.80 °C and 20.18 °C can be reached while the daily total power generation of 0.86 kWh, 0.81 kWh, 0.72 kWh can be achieved in Lhasa, Beijing and Nanjing, respectively; (ⅱ) during the hot water mode, the water temperature in the tanks increases only by 8.08°C–12.76 °C and the total power generation is around 0.20 kWh-0.23 kWh in the three cities while the indoor temperature increases by less than 0.1 °C due to the lowest facade solar radiation in summer.

Environmental Impact Assessment of PEM Fuel Cell Combined Heat and Power Generation System for Residential Application Considering Cathode Catalyst Layer Degradation

Recently, fuel cell combined heat and power systems (FC-CGSs) for residential applications have received increasing attention. The International Electrotechnical Commission has issued a technical specification (TS 62282-9-101) for environmental impact assessment procedures of FC-CGSs based on the life cycle assessment, which considers global warming during the utilization stage and abiotic depletion during the manufacturing stage. In proton exchange membrane fuel cells (PEMFCs), platinum (Pt) used in the catalyst layer is a major contributor to abiotic depletion, and Pt loading affects power generation performance. In the present study, based on TS 62282-9-101, we evaluated the environmental impact of a 700 W scale PEMFC-CGS considering cathode catalyst degradation. Through Pt dissolution and Ostwald ripening modeling, the electrochemical surface area transition of the Pt catalyst was calculated. As a result of the 10-year evaluation, the daily power generation of the PEMFC-CGS decreased by 11% to 26%, and the annual global warming value increased by 5% due to the increased use of grid electricity. In addition, when Pt loading was varied between 0.2 mg/cm2 and 0.4 mg/cm2, the 10-year global warming values were reduced by 6.5% to 7.8% compared to the case without a FC-CGS.

A novel integrated system of hydrogen liquefaction process and liquid air energy storage (LAES): Energy, exergy, and economic analysis

With the global positive response to environmental issues, cleaner energy will attract widespread attention. To improve the flexible consumption capacity of renewable energy and consider the urgent need to optimize the energy consumption and cost of the hydrogen liquefaction process, a novel system integrating the hydrogen liquefaction process and liquid air energy storage (HLP–LAES) is proposed. The operating strategy of the system ensures that it can produce liquid hydrogen and has the function of energy storage and power generation. A 3E study (energy, exergy, and economics) is carried out to evaluate the techno-economic performance of the proposed energy-intensive process. After optimization of key parameters, when the daily output of liquid hydrogen is 50 tons, the maximum daily power generation can reach 131.3 MWh, accounting for 1.21% of the daily electricity consumption of urban and rural residents in Qinghai Province, China. The round-trip efficiency of the proposed process is 58.9%, the specific energy consumption of liquid hydrogen is 7.25 kWh/kgLH2, and the total exergy efficiency is 53.2%. The payback period will be reduced to 1.7 years when the liquid hydrogen is sold at 7.0 $/kgLH2. If the proposed process is retrofitted from a stand-alone hydrogen liquefaction plant, the shortest retrofitting payback period is 9.2 years. The charging and discharging processes of the LAES are innovatively redesigned to better match the hydrogen liquefaction process, while achieving deep coupling and good synergy between the systems. This work aims to provide a reference for the efficient consumption of renewable energy, grid load balancing, and commercialization of the combination of liquid air energy storage and hydrogen liquefaction plants.

Design and Simulation of a PV Solar System with Silicon Hetero-Junction Technology (HJT) for a Residential Stand-Alone "off Grid" System with Batteries Using PV Syst Software in Iraq/Baghdad

Recently, the environment has been negatively impacted by the excessive CO2 emissions caused by the wide usage of fossil fuels in electricity generation. If this continued, it is predicted that the temperature of the atmosphere would rise, causing an increase in storms, hurricanes, droughts, dust, and floods. Therefore, as renewable energy produces little to no emissions, there is an urgent need to adapt it in recent times. Meanwhile, The PV sector has experienced rapid growth in recent years. The PV sector is embracing new technology, and the cell efficiency has been rising rapidly like Silicon Hetero- junction technology HJT which has offered additional benefits: It offers a well-suited application to reach efficiencies above 23% with process temperatures below 200°C. HJT solar panels have >90% module bifaciality and a low temperature coefficient (-0.3 %/C°), and provide additional benefit to the Levelized Cost of Energy LCOE and output power for PV systems. This study intends to assess the efficiency of a residential off-grid system with (HJT) PV panels at a total power of 2.0 kWh and the daily power close to 10 KWh/day with a 48V system in Iraq/Baghdad. PVsyst (7.2.11 version) software has been used for the analysis to calculate the energy output, and enhancing the system design. The characteristics, solar radiation, and ambient temperature are also included in the meteorological data used for evaluation, which is taken from PVsyst's database.

Design of Control System for Multistage Distillation Seawater Desalination Device Driven by Photovoltaic-Thermal

This research proposes a seawater desalination system driven by photovoltaic and solar thermal energy for remote regions such as islands and seaside villages where fresh water is not accessible. The performance of this system is demonstrated through experiments, and the main concerns are the output of the photovoltaic power generation system, power quantity, water yield, and the loads under different solar irradiance and temperature. In this system, a PLC is used as the controller to adjust the water pump by the collection and processing of sensor data. A load switching time system is designed to select different operating schemes under different environments in order to save energy. The control method of this system is developed to ensure that the photovoltaic power generation system does not undervoltage while maintaining the normal operation of the desalination system. An improved Perturbation and Observation (P&O) algorithm is also proposed as a new Maximum Point Power Tracking (MPPT) method to solve the problem of misjudgment and oscillation after tracking the maximum power point (MPP) in the traditional P&O algorithm. The simulation test in the MATLAB/Simulink environment shows that when external irradiance changes, the improved P&O algorithm can track the MPP faster than the traditional P&O algorithm, and the amplitude of oscillation on the MPP is smaller. The hardware experiments show that this system can operate stably and flexibly, and it is capable of producing 5.18 kWh of electric energy and 335.81 kg of freshwater per day. The maximum yield of the unit can reach 565.75 kg per day and the maximum daily power generation is 8.12 kWh.

Wind Farm Power Prediction Considering Layout and Wake Effect: Case Study of Saudi Arabia

The world’s technological and economic advancements have led to a sharp increase in the demand for electrical energy. Saudi Arabia is experiencing rapid economic and demographic growth, which is resulting in higher energy needs. The limits of fossil fuel reserves and their disruption to the environment have motivated the pursuit of alternative energy options such as wind energy. In order to regulate the power system to maintain safe and dependable operation, projections of current and daily power generation are crucial. Thus, this work focuses on wind power prediction and the statistical analysis of wind characteristics using wind data from a meteorological station in Makkah, Saudi Arabia. The data were collected over four years from January 2015 to July 2018. More than twelve thousand data points were collected and analyzed. Layout and wake effect studies were carried out. Furthermore, the near wake length downstream from the rotor disc between 1 and 5 rotor diameters (1D to 5D) was taken into account. Five robust machine learning algorithms were implemented to estimate the potential wind power production from a wind farm in Makkah, Saudi Arabia. The relationship between the wind speed and power produced for each season was carefully studied. Due to the variability in the wind speeds, the power production fluctuated much more in the winter. The higher the wind speed, the more significant the difference in energy production between the five farm layouts, and vice versa, whereas at a low wind speed, there was no significant difference in the power production in all of the near wake lengths of the 1D to 5D rotor diameters downstream from the rotor disc. Among the utilized prediction models, the decision tree regression was found to have the best accuracy values in all four utilized evaluation metrics, with 0.994 in R-squared, 0.025 in MAE, 0.273 in MSE, and 0.522 in RMSE. The obtained results were satisfactory and provide support for the construction of several wind farms, producing hundreds of megawatts, in Saudi Arabia, particularly in the Makkah Region.

Influence of the Long-Range Transport of Siberian Biomass Burnings on Air Quality in Northeast China in June 2017.

Biomass burning (BB) emits a large volume of trace gases and aerosols into the atmosphere, which can significantly affect the earth's radiative balance and climate and has negative impacts on air quality and even human health. In late June 2017, an intense BB case, dominated by forest and savanna fires, occurred in Siberia, and it affected the air quality of Northeast China through long-range transport. Here, multisatellite remote-sensing products and ground-based PM2.5 measurements are used to evaluate the influence of the Siberian smoky plume on Northeast China. The results show that the BB was intense at the early stage when the daily fire count and average fire radiative power exceeded 300 and 200 MW, respectively. The maximum daily fire count reached 1350 in Siberia, and the peak value of instantaneous fire radiative power was as high as 3091.5 MW. High concentrations of CO and aerosols were emitted into the atmosphere by the BB in Siberia. The maximum daily mean values of the CO column concentration and aerosol optical depth (AOD) increased by 3 × 1017 molec·cm2 and 0.5 compared with that during the initial BB stage. In addition, the BB released a large number of absorptive aerosols into the atmosphere, and the UV aerosol index (UVAI) increased by five times at the peak of the event in Siberia. Under the appropriate synoptic conditions and, combined with pyroconvection, the smoky plume was lifted into the upper air and transported to Northeast China, affecting the air quality of Northeast China. The daily mean values of CO concentration, AOD, and UVAI in Northeast China increased by 6 × 1017 molec·cm2, 0.5, and 1.4, respectively, after being affected. Moreover, the concentration of the surface PM2.5 in Northeast China approximately doubled after being affected by the plume. The results of this study indicate that the air quality of Northeast China can be significantly affected by Siberian BBs under favorable conditions.

Reduction method for multi-period time series scenarios of wind power

In the planning and operation of power systems containing wind power, it is of great significance to use a small number of representative wind power time series scenarios to accurately portray the stochastic characteristics of wind power. With the increase of the number of scenarios, how to form representative typical scenarios to balance computational efficiency and accuracy is an urgent problem to be solved. In this study, a bi-directional optimization method is proposed to generate daily wind power time series scenarios based on a single-period optimal scenario generation strategy and a multi-period scenario reduction strategy. First, the Wasserstein probability distance index is used to form a scenario model that is best approximated to the probability distribution of wind power, and the optimal scenarios of each period are generated. Secondly, a wind power scenario reduction strategy that integrates spatial distance and stochastic features is proposed. The improved taboo search method is used to selectively connect the representative scenarios of each period to form the representative daily wind power time series scenarios. Finally, the effectiveness and practicality of the proposed wind power time series scenario generation method are verified by simulations.

Experimental analysis of the fixed flat-plate solar collector with Sn-Al2O3 selective absorber and gravity water flow

To improve solar collector efficiency, a variety of designs and materials have been introduced into production practice. Studies describing solar collector specifics, therefore, are particularly valuable to the scientific community as they contribute to the overall body of knowledge and constant improvement the in the scientific field. In that regard, the study presented in this paper analyses the thermal performance of the fixed flat-plate collector with an Sn-Al2O3 selective absorber. The fixed flat-plate collector design utilizes gravity water flow in an open loop system. A two-month study was conducted to perform the analysis. The experiment was based on measurements of water flow in the fixed flat-plate col-lector, the water temperature at the fixed flat-plate collector inlet and outlet, and solar radiation intensity on a horizontal surface. Results for three randomly selected measurement days have shown that fixed flat-plate collector can achieve relatively satisfactory values for average daily specific heat power, thermal efficiency, and inlet-outlet water temperature gradient, respectively: June 29 (381.78 W/m2, 60.67%, and 9.06?C), June 30 (364.33 W/m2, 59.43%, and 7.46?C), and July 15 (373.06 W/m2, 59.85%, and 8.69?C). Apart from the relatively good measurement results, this type of solar collector does not require circulating pumps for operation, which brings a double advantage: energy saving and energy production.

Optimization of the Placement and Size of Photovoltaic Source

This paper presents a new optimization study of the placement and size of a photovoltaic source (PVS) in a distribution grid, based on annual records of meteorological parameters (irradiance, temperature). Based on the recorded data, the production output as well as the daily average power (24-h vector) of the PVS is extracted over the year. When a power vector is available, it can be used as an input when searching for the optimal size of the PVS. This allows to take into account the constraint of the variation of the power generated by this source considering the variation of the power consumed by the electrical loads during the whole day. A multi-objective fitness function has been considered. The latter minimizes the active losses and maximizes the voltage stability index during the day, while considering the constraints of the system, that is, the security, technical, geographical, and meteorological constraints. This problem was solved using the Non-dominated Sorting Genetic Algorithm NSGA-II optimization technique under MATLAB 2021. It was applied to the distribution network of Ghardaïa of 59 nodes.

DEVELOPING A SUN TRACKING SYSTEM IN THE DISCRETE MODE OF SOLAR STATIONS

A solar tracking system in discrete control mode has been developed and tested for solar stations. It has been shown that the use of short positioning stops leads to a reduction in the power consumption of the rotary device several times, while the daily power generation decreases slightly.

A Three-Port Energy Router for Grid-Tied PV Generation Systems With Optimized Control Methods

In grid-tied photovoltaic (PV) generation systems, intelligent energy management is required to maximize its performance. In this article, a novel three-port energy router with optimized control is proposed for this application. The proposed converter can interface among three ports (PV source, battery, and dc-link) with high integration. The PV panel is connected to the battery through an interleaved boost structure on the primary side. The primary-side PV-battery system and secondary-side dc-link are connected through a dual-active-bridge (DAB) converter. The battery operates as an energy buffer to compensate for the power mismatch due to the intermittent nature of the PV source. According to the daily power profile and intelligent power management between the grid and battery, six operating modes are possible. Optimized control strategies are customized in different operating modes. The maximum-power-point-tracking (MPPT) of the PV panel can be always realized. The zero-voltage-switching (ZVS) condition for all <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, reducing circulating current over a wide range, and flexible energy flow among three ports are all taken into considerations in the design. To verify the proposed concept, a 500 W rated prototype is designed. The designed prototype exhibits high efficiency in various operating modes. The experimental results agree well with the theoretical analysis.

Energy Consumption Analysis and Optimization of Electric Submersible Pump System

Electric submersible pumps account for a considerable proportion in the development of the Bohai Oilfield. Improving the system efficiency of the electric submersible pump wells, ensuring that the units operate in the high-efficiency zone, is essential. Analysis shows that the efficiency of the electric submersible pump system depends on the wear and tear of each component of the submersible pump equipment, the setting of operational parameters, and more importantly, the production status and daily management level of the oil well. Therefore, improving the structural performance of the submersible pump product, optimizing the parameters setting of the oil well, strengthening daily management, establishing a scientific management system, and improving the production management process and system can effectively improve the production efficiency and economic benefits of the oil well, and further achieve the goal of energy saving and emission reduction. In addition, it is necessary to actively promote the concept and technology of energy saving and emission reduction, encourage oilfield enterprises to explore effective measures to reduce the energy consumption of the electric submersible pump system by strengthening the scientific management system, and achieve a green, low-carbon, and high-quality development of oilfield production to achieve the unity of economic benefits, social benefits, and environmental benefits. This article applies the above measures in the P oilfield to achieve energy optimization of submersible electric pump systems, reducing the daily power consumption of single well submersible electric pump systems by 371 kWh per day, increasing the submersible electric pump's lifespan by 200 days, generating considerable project benefits.

Comparative Analysis of Energy Storage Methods for Energy Systems and Complexes

The daily non-uniform power demand is a serious problem in power industry. In addition, recent decades show a trend for the transition to renewable power sources, but their power output depends upon weather and daily conditions. These factors determine the urgency of energy accumulation technology research and development. The presence of a wide variety of energy storage mechanisms leads to the need for their classification and comparison as well as a consideration of possible options for their application in modern power units. This paper presents a comparative analysis of energy storage methods for energy systems and complexes. Recommendations are made on the choice of storage technologies for the modern energy industry. The change in the cost of supplied energy at power plants by integrating various energy storage systems is estimated and the technologies for their implementation are considered. It is revealed that in the large-scale power production industry, the most productive accumulation methods for energy systems and complexes are the following: pumped hydroelectric energy storage systems, thermal and thermochemical accumulations, and hydrogen systems. These methods have the best technical and economic characteristics. The resulting recommendations allow for the assessment of the economic and energy effect achieved by integration of storage systems at the stage of designing new power units.

Analysis of energy potential for grid-tied solar energy systems for medium industrial applications

This research investigated the potential of using solar photovoltaic (PV) energy to support small-to-medium size industries without the need for energy storage. The peak industrial production hours from morning to evening were investigated and the average daily power required was compared with the available solar power, in order to determine the amount of power that can be recouped from solar-grid hybridization over one year. The available zero-upfront cost plans in Kenya were investigated and the payback rate and benefits to both the buyer and the investor were analyzed. The peak hour power demand and solar potential were compared to determine to what extent battery elimination can be used efficiently during production. The solar power without batteries was found sufficient to be used interchangeably with utility power maximizing on the times of peak solar power. The purpose of the derived report is to help in saving running costs since the cost of battery banks can be partially eliminated and reliance on grid power can be minimized. It also helps an investor to make an informed decision on the zeroupfront cost plan. It was found that, on average, a saving of 8.9% is feasible, with a potential of 23% – 30% if the maximum dependence on PV is employed. The cost of the 15kW plant was found to be recoverable in an average of 10 years for the full power uptake

Rolling optimization based on holism for the operation strategy of solar tower power plant

Solar tower power plants (STP) with thermal energy storage have the ability to temporally shift power generation, regulate peak load and modulate frequency. The power production of such systems not only depends on the available solar resources, but also on the operation strategies, such as the operational thresholds used to control when the equipment starts or stops in certain conditions. Currently, most of the operational thresholds are determined by operators’ experience or the rated parameters given by the equipment manufacturers, which are usually unoptimized fixed values. Therefore, to guide the optimal operations of STP, optimization methods are developed in this work to optimize the daily operational thresholds according to the solar radiation at present and in the future. Firstly, a well-validated in-house model with easy-to-tune operation strategies for STP is developed to optimize the thresholds. Then, five operational thresholds affecting the power generation of STP are identified. Finally, an optimization algorithm is proposed to optimize the operational thresholds. The proposed optimization algorithm uses a rolling optimization based on holism to enhance regular particle swarm optimization (R-PSO). The power generation of a 50 MW STP under three different operation strategies is compared: (1) unoptimized operation strategy, (2) operation strategy optimized by regular PSO algorithm, and (3) operation strategy optimized by R-PSO algorithm. The average daily power generation under the three operation strategies is 451.16 MWh, 490.25 MWh, and 511.63 MWh, respectively. The results show that the proposed R-PSO could increase averaged daily power production by 13.4 % and 4.36 % when compared with cases with no optimization and PSO optimization, respectively. Therefore, the power production of STP can be significantly improved by optimizing the identified daily operational thresholds using the R-PSO algorithm.

Thermal performance analyses and optimization of data center centralized-cooling system

In this study, the factors that influence the power consumption of a data center centralized-cooling system were investigated from both the indoor thermal environment and chilled water mass flow rate perspectives to maximize the free cooling utilization potential. First, a cooling load model is proposed and verified. Subsequently, based on a typical centralized-cooling system that combines free cooling devices and chillers, mathematical analyses were conducted on its thermal performance, considering different climate regions and heat dissipation densities related to the IT equipment. The results indicated that up to 83.5 % and 75.3 % of the annual cooling demand could be recovered by free cooling in Harbin and Beijing, respectively. However, during actual operations, this value is reduced because of the mixture of cold and hot air and inappropriate chilled water flow rates. To achieve the lowest annual or daily power consumption of the cooling system, the chilled water flow rates were optimized. Under optimal conditions, Power Usage Effectiveness (PUE) can be improved by 4.5 to 30.6 % compared to the worst case scenario under discussion.

Research on Distributed Resource Aggregation Technology Based on Hierarchical Agglomerative Clustering Analysis

With the rapid development of distributed resources such as wind turbines and photovoltaics in the power system, intermittency and volatility will directly impact the security and stability of the power grid and power transactions. This paper combines the principal component analysis method and hierarchical agglomerative clustering algorithm to analyze the output characteristics of distributed resources. According to the Davies-Bouldin index to evaluate the clustering results, the typical characteristic output curves of distributed resources are obtained. Then the typical curve is used to represent the distributed resources for aggregation. Based on daily peak-valley difference and power fluctuation index, the comprehensive results are judged and the optimal solution is selected. Finally, an example with eight distributed resources is given to verify the effectiveness of the proposed method.

Research on Optimizing Transmission Efficiency and Illumination Distribution of Tubular Daylighting System

Although building lighting is paid more and more attention now, due to the limited areas illuminated by typical lighting, such as windows and skylights, especially the lack of sunlight irradiance and uneven distribution of sunlight often occur deep inside the room. The light pipe can effectively solve this kind of problem and transmit sunlight directly to the room. The light pipe with the inner diameter of 250mm was fixed, and the working efficiency of light pipes with different shapes and sizes was simulated by computer with illumination angles of 15, 45 and 90. Through simulation, it is found that the illumination angles of light pipes with different shapes and sizes are different at the maximum efficiency. It can match the suitable regional environment according to shape and size characteristics, meet daily office needs, and reduce the assistance of artificial lighting during the day, thus reducing the use of artificial lighting in buildings during the day and reducing the daily power consumption.

Building Power Demand Estimation on Unusual Days Considering Facility Operation Status and Number of Occupants

To optimally conduct capital investment and energy management for buildings with storage batteries and photovoltaic (PV) generation, it is essential to accurately predict the electricity demand not only on weekdays but also on holidays and event days. However, predicting the building power demand on holidays and event days is difficult because facility operations and the number of occupants in a building are different from weekdays. In this paper, we propose a method to estimate unusual power demand by considering the power demand structure of existing buildings. The proposed method is an application of disaggregation techniques based on linear regression. First, a power demand structure model is developed by calculating the facility status demand contribution and number of occupants from weekday operational data. Second, the daily power demand is estimated with high accuracy by applying hypothetical operational scenarios, such as holidays, to the model. Experimental data from real offices confirm that the proposed method could estimate the power demand during weekends and vacation periods when the attendance rate is reduced by half.