Multi-Time Scale Optimal Scheduling of a Photovoltaic Energy Storage Building System Based on Model Predictive Control

Building emission reduction is an important way to achieve China’s carbon peaking and carbon neutrality goals.Aiming at the problem of low carbon economic operation of a photovoltaic energy storage building system,a multi-time scale optimal scheduling strategy based on model predictive control(MPC)is proposed under the consideration of load optimization.First,load optimization is achieved by controlling the charging time of electric vehicles as well as adjusting the air conditioning operation temperature,and the photovoltaic energy storage building system model is constructed to propose a day-ahead scheduling strategy with the lowest daily operation cost.Second,considering inter-day to intra-day source-load prediction error,an intraday rolling optimal scheduling strategy based on MPC is proposed that dynamically corrects the day-ahead dispatch results to stabilize system power fluctuations and promote photovoltaic consumption.Finally,taking an office building on a summer work day as an example,the effectiveness of the proposed scheduling strategy is verified.The results of the example show that the strategy reduces the total operating cost of the photovoltaic energy storage building system by 17.11%,improves the carbon emission reduction by 7.99%,and the photovoltaic consumption rate reaches 98.57%,improving the system’s low-carbon and economic performance.

An Accurate Dynamic Forecast of Photovoltaic Energy Generation

The accurate forecast of the photovoltaic generation(PVG)process is essential to develop optimum installation sizing and pragmatic energy planning and management.This paper proposes a PVG forecast model for a PVG/Battery installation.The forecasting strategy is built on a Medium-Term Energy Forecasting(MTEF)approach refined dynamically every hour(Dynamic Medium-Term Energy Forecasting(DMTEF))and adjusted by means of a Short-Term Energy Forecasting(STEF)strategy.The MTEF predicts the generated energy for a day ahead based on the PVG of the last 15 days.As for STEF,it is a combination between PVG Short-Term(ST)forecasting and DMTEF methods obtained by selecting the least inaccurate PVG estimation every 15 minutes.The algorithm results are validated by measures taken on a 3 KWp standalone PVG/Battery installation.The proposed approaches have been integrated into a management algorithm in order to make a pragmatic decision to ensure load supply considering relevant constraints and priorities and guarantee the battery safety.Simulation results show that STEF provides accurate results compared to measures in stable and perturbed days.The NMBE(Normalized Mean Bias Error)is equal to-0.58%in stable days and 26.10%in perturbed days.

Evaluation of the Performance of Lithium-Ion Accumulators for Photovoltaic Energy Storage

In a context of climate change exacerbated by the increasing scarcity of fossil fuels, renewable energies, in particular photovoltaic solar energy, offer a promising alternative. Solar energy is non-polluting, globally available and the most widely distributed resource on Earth. However, the intermittency of this energy source considerably limits its expansion. To solve this problem, storage techniques are being used, in particular, electrochemical storage using lithium-ion batteries. In this article, we will evaluate the performance of lithium-ion batteries when integrated into a photovoltaic grid. To do this, modelling and simulation of a photovoltaic system connected to a lithium-ion battery storage system will be carried out using MATLAB/Simulink software. A diagnostic of the energy consumption of the Kaya Polytechnic University Centre will be carried out, and the data will then be used in the simulator to observe the behaviour of the PV-Lion system. The results obtained indicate that lithium-ion batteries can effectively meet the centre’s energy demand. In addition, it was observed that lithium-ion batteries perform better under high energy demand than the other battery technologies studied. Successive storage systems with the same capacity but different battery technologies were compared. It was found that these storage systems can handle a maximum power of 4 × 105 W for lead-acid batteries, 6.5 × 105 W for nickel-cadmium batteries, 8.5 × 105 W for nickel-metal-hydride batteries, and more than 10 × 105 W for lithium-ion technology.

Stochastic maximum power point tracking of photovoltaic energy system under partial shading conditions

A large portion of the available power generation of a photovoltaic (PV) array could be wasted due to partial shading, temperature and irradiance effects, which create current/voltage imbalance between the PV modules. Partial shading is a phenomenon which occurs when some modules in a PV array receive non-uniform irradiation due to dust, cloudy weather or shadows of nearby objects such as buildings, trees, mountains, birds etc. Maximum power point tracking (MPPT) techniques are designed in order to deal with this problem. In this research, a Markov Decision Process (MDP) based MPPT technique is proposed. MDP consists of a set of states, a set of actions in each state, state transition probabilities, reward function, and the discount factor. The PV system in terms of the MDP framework is modelled first and once the states, actions, transition probabilities, and reward function, and the discount factor are defined, the resulting MDP is solved for the optimal policy using stochastic dynamic programming. The behavior of the resulting optimal policy is analyzed and characterized, and the results are compared to existing MPPT control methods.

Bi-level Optimal Planning of Voltage Regulator in Distribution Systems Considering Maximization of Incentive-based Photovoltaic Energy Integration

This paper focuses on optimal voltage regulator(VR)planning to maximize the photovoltaic(PV)energy integration in distribution grids.To describe the amount of dynamic PV energy that can be integrated into the power system,the concept of PV accommodation capability(PVAC)is introduced and modeled with optimization.Our proposed planning model is formulated as a Benders decomposition based bi-level stochastic optimization problem.In the upper-level problem,VR planning decisions and PVAC are determined via mixed integer linear programming(MILP)before considering uncertainty.Then in the lower-level problem,the feasibility of first-level results is checked by critical network constraints(e.g.voltage magnitude constraints and line capacity constraints)under uncertainties considered by time-varying loads and PV generations.In this paper,these uncertainties are represented in the form of operational scenarios,which are generated by the Gaussian copula theory and reduced by a well-studied backward-reduction algorithm.The modified IEEE 33-node distribution grid is utilized to verify the effectiveness of the proposed model.The results demonstrate that a PV energy integration can be significantly enhanced after optimal voltage regulator planning.

Research on Virtual DC Generator-Based Control Strategy of DCMicrogrid with Photovoltaic and Energy Storage

With the penetration of a large number of photovoltaic power generation units and power electronic converters,the DC microgrid shows low inertia characteristics,which might affect the stable operation of the microgrid in extreme cases.In order to enhance the“flexible features”of the interface converter connected to the DC bus,a control strategy of DCmicrogrid with photovoltaic and energy storage based on the virtual DC generator(VDCG)is proposed in this paper.The interface converters of the photovoltaic power generation system and the energy storage system simulates the inertia and damping characteristics of the DC generator to improve the stability of the DC bus voltage.The impedance ratio of DC microgrid was obtained by establishing the small-signal model of photovoltaic power generation system and energy storage system,and the Nyquist curves was applied to analyze the small-signal stability of the system.Finally,the simulation results were verified with MATLAB/Simulink.The results show that the proposed control strategy can slow down the fluctuation of bus voltage under the conditions of photovoltaic power fluctuation and load mutation,thus enhancing the system stability.

Three dimensional photovoltaic fibers for wearable energy harvesting and conversion

As the development of smart electronics, self-powered sources have been attracting increasing attention.This review summarizes research progress of photovoltaic fibers and their integrated power sources with multi-stage energy conversion. Recent development of three dimensional photovoltaic fibers is glanced with special attention to structure design and materials of typical photovoltaic types（inorganic, organic,dye/quantum dot sensitized and perovskite solar cells）. The application of carbon materials in fiber energy is focused as it is a hot topic recently. The hybrid energy systems based on fiber solar cells and fiber supercapacitors, fiber batteries and fiber nanogenerators are summarized together with hybrid energy textiles. This review provides a macroscopic view of novel energy fibers and will attract research interest in flexible/wearable fiber electronics and energy textiles.

Application and Research of Photovoltaic New Energy in Electrical Energy Conservation

At present,the increasing consumption of electrical energy is accompanied by the increasing pressure on natural environment,excessive discharge of waste gas,and accelerated rate of global warming.Photovoltaic new energy plays an important role in reducing costs and improving resource utilization.The leading power industries should come up with new designs of equipment that is in line with the green concept,improve the utilization of photovoltaic energy,and realize sustainable economic development.In view of this,this paper mainly analyzes the application of photovoltaic new energy in electrical energy conservation.

A Scientometric Approach to Analyze Scientific Development on Renewable Energy Sources

Purpose: This paper aims to point out the scientific development and research density of renewable energy sources such as photovoltaic, wind, and biomass, using a mix of computational tools. Based on this, it was possible to verify the existence of new research trends and opportunities in a macro view regarding management, performance evaluation, and decision-making in renewable energy generation systems and installations.Design/methodology/approach: A scientometric approach was used based on a research protocol to retrieve papers from the Scopus database, and through four scientometric questions, to analyze each area. Software such as the Science Mapping Analysis Software Tool(Sci MAT) and Sci2 Tool were used to map the science development and density.Findings: The scientific development of renewable energy areas is highlighted, pointing out research opportunities regarding management, studies on costs and investments, systemic diagnosis, and performance evaluation for decision-making in businesses in these areas.Research limitations: This paper was limited to the articles indexed in the Scopus database and by the questions used to analyze the scientific development of renewable energy areas.Practical implications: The results show the need for a managerial perspective in businesses related to renewable energy sources at the managerial, technical, and operational levels, including performance evaluation, assertive decision making, and adequate use of technical and financial resources.Originality/value: This paper shows that there is a research field to be explored, with gaps to fill and further research to be carried out in this area. Besides, this paper can serve as a basis for other studies and research in other areas and domains.

Comparative Study of the Moroccan Power Grid Reliability in Presence of Photovoltaic and Wind Generation

The photovoltaic sector in Morocco is a serious option for the future. The integration of this type of energy into the grid has a considerable effect on the adequacy of the grid. The objective of this work is to assess the reliability of the Moroccan power grid at the hierarchical level I (HLI: load coverage under the assumption of infinite node) using a non-sequential Monte Carlo simulation in which photovoltaic generation is introduced. In order to lead such a study, a model was used in order to calculate the hourly solar radiation and to determine the time evolution of the electrical power produced by photovoltaic power plants. Finally, we also compared the impact of both PV and wind generations in terms of adequacy of the Moroccan electrical supply.

Advances in Cost-Efficient Thin-Film Photovoltaics Based on Cu（In,Ga）Se2

In this article, we discuss the leading thin-film photovoltaic （PV） technology based on the Cu（ln,Ga）Se2 （CIGS） compound semiconductor. This contribution includes a general comparison with the conventional Si-wafer-based PV technology and discusses the basics of the CIGS technology as well as advances in world-record-level conversion efficiency, production, applications, stability, and future developments with respect to a flexible product. Once in large-scale mass production, the CIGS technology has the highest potential of all PV technologies for cost-efficient clean energy generation.

Design of the Mobile Phone Charging Device based on Human Motion Energy and Light Energy

This paper designs a mechanical swing of placementing mobile phone, which is inspired by the mechanical watch automatic winding process. The use of the kinetic energy generated by human body motion drives the wheel swing and the generator, it can carry out mobile phone additional charge through the electronic components rectifier and DC/DC converter regulator, the use of human motion and light energy can extend a fixed charge mobile phone standby time. The human motion power uses electromagnetic coupling technique and collects energy by using foot swing, solar power generation uses DSP chip in TMS320F28927 control a plurality of charging circuit, inverter circuit and solar maximum power point tracking by sampling and multiple output PWM wave. Finally, charging process has the basic constant current process discovered by device testing, the design of human motion and light energy mobile phone charger can satisfy the need of mobile phone rechargeable lithium batteries.

Two Axes Solar Tracker Based on Solar Maps, Controlled by a Low-Power Microcontroller

There are actually several solutions for two axis solar tracking systems using electromechanical devices, in which a controller detects the Sun apparent position, and controls the position of the structure supporting the panels toward the sun by enabling the engines movement. This work studies the solution of two axis solar tracking system based on solar maps, which can predict the exact apparent position of the Sun, by the latitude＇s location, thereby avoiding the need to use sensors or guidance systems. To accomplish this, it is used a low-power microcontroller, suitably programmed, to control two electric motors to ensure that the panels supporting structure is always oriented towards the sun.

Modelling and Coordinated Control of Grid Connected Photovoltaic,Wind Turbine Driven PMSG,and Energy Storage Device for a Hybrid DC/AC Microgrid

In a DC/AC microgrid system,the issues of DC bus voltage regulation and power sharing have been the subject of a significant amount of research.Integra-tion of renewable energy into the grid involves multiple converters and these are vulnerable to perturbations caused by transient events.To enhance the flexibility and controllability of the grid connected converter(GCC),this paper proposes a common DC bus voltage maintenance and power sharing control strategy of a GCC for a DC/AC microgrid.A maximum power point tracking algorithm is employed to enhance the power delivered by the wind turbine and photovoltaic module.The proposed control strategy consists of primary and secondary as-pects.In the primary layer control,the DC bus voltage is regulated by the GCC.In the secondary layer,the DC bus voltage is maintained by the energy storage device.This ensures reliable power for local loads during grid failures,while power injection to the grid is controlled by an en-ergy management algorithm followed by reference gen-eration of inductor current in the GCC.The proposed control strategy operates in different modes of DC voltage regulation,power injection to the grid and a hybrid op-erating mode.It provides wide flexible control and en-sures the reliable operation of the microgrid.The pro-posed and conventional techniques are compared for a 15.8 kW DC/AC microgrid system using the MATLAB/Simulink environment.The simulation results demonstrate the transient behaviour of the system in different operating conditions.The proposed control technique is twice as fast in its transient response and produces less oscillation than the conventional system.Index Terms—Wind energy,photovoltaic energy,DC/AC microgrid,battery energy storage system,co-ordinated control.

Numerical Simulation of Tandem Using ZnS as a Buffer Layer Cu I(1-x) CaxSe2/CuGaSe2

In the global context of diversification of usable energy sources, the use of renewable energies, in particular solar photovoltaic energy, is becoming increasingly important. As such, the development of a new generation of photovoltaic cells based on the CIGS material is promising. Indeed, the efficiency of these cells has exceeded 20% in recent years. Thus, our work consists in the modeling of a tandem solar cell based on Cu(In,Ga)Se2 (CGS/CIGS). The goal is to optimize its physical and geometrical parameters in order to obtain a better photovoltaic conversion efficiency compared to other research works on tandem in the past. We used AMPS-1D software for the simulation. When we realize the tandem, the least efficient cell (CGS) imposes the current and the shape of the J-V characteristic of the tandem. We obtained a theoretical efficiency of 39.30% which is significantly higher than the efficiencies obtained in the past by other researchers with a short circuit current of 34.60 mA/cm2, an open circuit voltage of 1.74 V and a form factor of 65.20%. The simulation also showed that the high defect density in the material strongly impacts the performance of the tandem.

Estimation of Equivalent Model of Photovoltaic Array Using Unscented Kalman Filters

This paper proposes the use of the unscented Kalman filter to estimate the equivalent model of a photovoltaic(PV)array,using external measurements of current and voltage at the inverter level.The estimated model is of interest to predict the power output of PV plants,in both planning and operation scenarios,and thus improves the efficient operation of power systems with high penetration of renewable energy.The proposed technique has been assessed in several simulated scenarios under different operating conditions.The results show that accurate estimates are provided for the model parameters,even in the presence of measurement noise and abrupt variations under the external conditions.

A comprehensive analysis of future solar energy potential variations using a CMIP6 multi-model ensemble approach in Colombia

Climate change is predicted to significantly impact solar energy generation,which is particularly concerning given that photovoltaic(PV)energy is critical to the global transition to clean energy in underdeveloped countries.This study analyses the PV potential variations in Colombia using a Coupled Model Intercomparison Project Phase 6(CMIP6)multi-model ensemble approach under two shared socio-economic pathway scenarios for the near(2025-50)and far(2051-2100)future.During the near-future period,the Pacific,Andean and Orinoquía regions are expected to experience a decrease in PV potential ranging from 10%to 23%for all shared socio-economic pathways.It will be particularly noticeable during the March/April/May and June/July/August seasons.On the other hand,CMIP6 estimations indicate a 1-4%increase in PV potential across the Amazon region during the June/July/August and September/October/November seasons.For the far future,it has been projected that the Pacific,Andean and Orinoquía regions may experience a significant decline in solar power generation due to increased cloud cover and reduced sunshine.The decrease in PV potential during the June/July/August season could range from 8%to 27%for all considered scenarios,with the Pacific region being the most affected.The Pacific region is projected to experience a decrease ranging from 10%to 35%for all seasons.It is worth noting that there are noticeable differences in PV potential across various regions,which can result in changes in cloud cover and atmospheric aerosols.Overall,the study provides valuable insights into the PV potential in Colombia and highlights the importance of considering regional variations and climate change scenarios in future energy planning.

Wide spectrum solar energy harvesting through an integrated photovoltaic and thermoelectric system

This paper proposes a power system concept that integrates photovoltaic （PV） and thermoelectric （TE） technologies to harvest solar energy from a wide spectral range. By introduction of the ＇spectrum beam splitting＇ technique, short wavelength solar radiation is converted directly into electricity in the PV cells, while the long wavelength segment of the spectrum is used to produce moderate to high temperature thermal energy, which then generates electricity in the TE device. To overcome the intermittent nature of solar radiation, the system is also coupled to a thermal energy storage unit. A systematic analysis of the integrated system is carried out, encompassing the system configuration, material properties, thermal management, and energy storage aspects. We have also attempted to optimize the integrated system. The results indicate that the system configuration and optimization are the most important factors for high overall efficiency.

Renewable Energies in Africa, Context and Socio-Economic Challenge

In this paper, we have shown that Africa has an enormous wealth of renewable energy resources among the most important in the world such as the strong sunshine, Congo and Nile Rivers respectively among the most powerful and the longest in the world. We have underlined the presence of important forests, rich subsoil in mineral elements, and strong winds. In addition to a rapidly growing human capital, Africa, therefore, has at its disposal all the factors enabling it to initiate sustainable and inclusive socio-economic development. We have shown that the transformation of these renewable energies is an opportunity for Africa to reach its socio-economic challenges. The development of renewable energies in Africa will be a source of many financial benefits and advantages both in terms of improving living conditions and carrying out activities. The electrical supply of rural areas of Africa represents a considerable issue, which can be a propellant factor in long-term socio-economic development if the conditions of use of clean fuel and cooking technologies, especially sanitary are taken into account. The provision of modern energy services can contribute to the creation of jobs for young people upstream. Among other things, we can note the development of local skills, the creation of income-generating activities, and the improvement of hygiene and health measures which are necessary conditions for family and social well-being. This requires a policy focused, on research in general and in particular on semiconductors that participate in the transformation of photovoltaic solar energy. We have stressed that Africa which is currently experiencing a period of economic growth and sustained transformation must be very looking at in its energy policy and give pride of place to renewable energies to initiate sustainable socio-economic development, equitable and inclusive different social strata both in rural areas and urban areas.

Modelling of photovoltaic production and electrochemical storage in an autonomous solar drone

A simple,efficient simulator has been developed to predict the generation of photovoltaic energy and its storage in Li-ion batteries,for an autonomous drone with four wings covered by solar panels based on thin-film gallium arsenide photovoltaic cells(III–V).This simulator allows prediction of the effective photovoltaic power produced by the solar panels as well as the battery pack voltage when the drone is flying.Flight parameters such as irra-diance,sun inclination angles,and drone Euler angles are considered as input parameters.The measured photovoltaic power and battery pack voltage are in good agreement with the simulated values,making practical use by the XSun company possible.This parametric study shows the effects of climatic and geographic conditions on drone autonomy.In optimal weather conditions on a sunny day,drone flight can last 12 h.