Multi-criteria fuzzy algorithm for energy management of a domestic photovoltaic panel

This paper presents a fuzzy algorithm which makes decision so as to connect domestic apparatus on either the electrical grid or a photovoltaic panel (PVP). The decision is made in real time with respect to multi-energy save criteria and upon the PVP maximum available power and apparatus states. The algorithm is validated on a 1 kW peak (kWp) PVP and domicile apparatus of different powers installed at the Energy and Thermal Research Centre (CRTEn) in the north of Tunisia. Criteria are verified on the system behaviour during days covering the different seasons of the year. The power audit, established using measures, confirms that the energy save during daylight reaches 90% of the PVP available energy.     

Daily energy planning of a household photovoltaic panel

This paper puts forward an energy planning approach which offers a daily optimum management of a household photovoltaic panel generation (PVG) without using storage equipment. The approach considers the PVG of the last 10 days to estimate the one of the next day, using a Neuro-Fuzzy algorithm. The estimated PVG is planned according to the consumer’s needs so as to use the maximum of the generated energy. The algorithm decides by means of fuzzy rules the connection times of appliances, having different powers, to the photovoltaic panel (PVP) output during the day. The decision is made on the basis of optimization criteria with respect to different user operation modes. The approach is validated on a 260 Wp PVP and a set of four appliances of 30 W, 40 W, 60 W and 75 W. The system is installed at the National Engineering School, University of Sfax (ENIS) – Tunisia. The daily energetic assessment confirms that the PVG planning makes use of the estimated available energy in between 70% and 80%.     

Controlling of grid connected photovoltaic lighting system with fuzzy logic

In this study, DC electrical energy produced by photovoltaic panels is converted to AC electrical energy and an indoor area is illuminated using this energy. System is controlled by fuzzy logic algorithm controller designed with 16 rules. Energy is supplied from accumulator which is charged by photovoltaic panels if its energy would be sufficient otherwise it is supplied from grid. During the 1-week usage period at the semester time, 1.968 kWh energy is used from grid but designed system used 0.542 kWh energy from photovoltaic panels at the experiments. Energy saving is determined by calculations and measurements for one education year period (9 months) 70.848 kWh.     

Optimum energy management of a photovoltaic water pumping system

This paper presents a new management approach which makes decision on the optimum connection times of the elements of a photovoltaic water pumping installation: battery, water pump and photovoltaic panel. The decision is made by fuzzy rules considering the battery safety on the first hand and the Photovoltaic Panel Generation (PVPG) forecast during a considered day and the load required power on the second hand. The optimization approach consists of the extension of the operation time of the water pump with respects to multi objective management criteria. Compared to the stand alone management method, the new approach effectiveness is confirmed by the extension of the pumping period for more than 5 h a day.     

Thermal control influence on energy efficiency in domestic refrigerator powered by photovoltaic

This paper studies the importance of temperature control in household refrigerator on the environmental and economic plan. Refrigerator energy consumption is greatly affected by room temperature, door opening and thermostat regulation. A household refrigerator powered by photovoltaic energy was tested in laboratory to determine the effect of thermal regulation on energy consumption. Our investigation reveals that there is a difference in minimal average temperature between the thermostat and the evaporator for three different thermostat positions. This difference in temperature was justified by three parameters: the bad contact between the thermostat bulb and the surface of the evaporator, thermostat thermal inertia and the error due to the mechanical control of the thermostat. Finally, this work allows us an estimate of the energy saving by the kWh electricity price in the Middle East and North Africa region (MENA) Vs Europe region depending on the number of refrigerators. The energy optimization decreases the aggressive methods of electricity production. The Energy Efficiency and Solar Energy present an important alternative on the three planes Energy, Economic and Environmental (3E).     

An ANP-based approach for the selection of photovoltaic solar power plant investment projects

In this paper the Analytic Network Process (ANP) is applied to the selection of photovoltaic (PV) solar power projects. These projects follow a long management and execution process from plant site selection to plant start-up. As a consequence, there are many risks of time delays and even of project stoppage.In the case study presented in this paper a top manager of an important Spanish company that operates in the power market has to decide on the best PV project (from four alternative projects) to invest based on risk minimization. The manager identified 50 project execution delay and/or stoppage risks.The influences between the elements of the network (groups of risks and alternatives) were identified and analyzed using the ANP multicriteria decision analysis method. Two different ANP models were used: one hierarchy model (that considers AHP as a particular case of ANP) and one network-based model. The results obtained in each model were compared and analyzed. The main conclusion is that unlike the other models used in the study, the single network model can manage all the information of the real-world problem and thus it is the decision analysis model recommended by the authors. The strengths and weaknesses of ANP as a multicriteria decision analysis tool are also described in the paper.     

Functional requirements for component films in a solar thin-film photovoltaic/thermal panel

The functional requirements of the component films of a solar thin-film photovoltaic/thermal panel were considered. Particular emphasis was placed on the new functions, that each layer is required to perform, in addition to their pre-existing functions. The cut-off wavelength of the window layer, required for solar selectivity, can be achieved with charge carrier concentrations typical of photovoltaic devices, and thus does not compromise electrical efficiency. The upper (semiconductor) absorber layer has a sufficiently high thermal conductivity that there is negligible temperature difference across the film, and thus negligible loss in thermal performance. The lower (cermet) absorber layer can be fabricated with a high ceramic content, to maintain high solar selectivity, without significant increase in electrical resistance. A thin layer of molybdenum-based cermet at the top of this layer can provide an Ohmic contact to the upper absorber layer. A layer of aluminium nitride between the metal substrate and the back metal contact can provide electrical isolation to avoid short-circuiting of series-connected cells, while maintaining a thermal path to the metal substrate and heat extraction systems. Potential problems of differential contraction of heated films and substrates were identified, with a recommendation that fabrication processes, which avoid heating, are preferable.     

Intelligent photovoltaic farms for robust frequency stabilization in multi-area interconnected power system based on PSO-based optimal Sugeno fuzzy logic control

Currently, the grid-connected large PV farms are extensively installed in power systems. Nevertheless, in addition to the load change, the intermittent power output of PV farms may lead to the serious problem of the system frequency fluctuation. To handle this problem, this paper proposes a new design of Sugeno fuzzy logic controller based on particle swarm optimization (PSO-SFLC) of intelligent PV farms for the frequency stabilization in a multi-area interconnected power system. To handle various scenarios, the frequency deviations and solar insolations are used as input signals of the PSO-SFLC. The output signal of the PSO-SFLC is a command signal for adjusting PV output power. The output power of PV is controlled by the PSO-SFLC to meet the load demand so that the system frequency fluctuation can be suppressed. Without the difficulty of trial and error, the optimal input and output membership functions, and control rules of PSO-SFLC are automatically achieved by PSO. Simulation study in a three-area loop interconnected power system with large PV farms elucidates that the frequency stabilizing performance and robustness of the PV equipped with the PSO-SFLC is much superior to that of the PV with the SFLC and the PV with the maximum power point tracking control in scenarios with various solar insolations and loading conditions.     

Financial analysis of utility scale photovoltaic plants with battery energy storage

Battery energy storage is a flexible and responsive form of storing electrical energy from Renewable generation. The need for energy storage mainly stems from the intermittent nature of solar and wind energy sources. System integrators are investigating ways to design plants that can provide more stable output power without compromising the financial performance that is vital for investors. Network operators on the other side set stringent requirements for the commissioning of new generation, including preferential terms for energy providers with a well-defined generation profile. The aim of this work is to highlight the market and technology drivers that impact the feasibility of battery energy storage in a Utility-scale solar PV project. A simulation tool combines a battery cycling and lifetime model with a solar generation profile and electricity market prices. The business cases of the present market conditions and a projected future scenario are analyzed.     

Priority load control algorithm for optimal energy management in stand-alone photovoltaic systems

In stand-alone PV System facilities no grid connection exists, therefore the solar generator and battery bank have to be carefully sized in order to supply the energy demand for a given period of time. Batteries are considered as a weak component of the system, comprising an important part of the total cost and are usually replaced one or two times during PV system lifetime. A priority load control algorithm has been developed in order to gain an optimal energy management over system loads and the battery storage, and therefore provides a better energy management efficiency and guarantee the energy supply for critical loads. This will increase the reliability of the system and the end-user satisfaction. This article describes a stand-alone PV system model used for the development of a priority load control algorithm and explains and implements the algorithm. The results of several test scenario simulations are shown and discussed.     

Ancillary services and optimal household energy management with photovoltaic production

This article presents a project designed to increase the monetary value of photovoltaic (PV) solar production for residential applications. To contribute to developing new functionalities for this type of PV system and an efficient control system for optimising its operation, this article explains how the proposed system could contract to provide ancillary services, particularly the supply of active power services. This provision of service by a PV-based system for domestic applications, not currently available, has prompted a market design proposal related to the distribution system. The mathematical model for calculating the system's optimal operation (sources, load and exchanges of power with the grid) results in a linear mix integer optimisation problem in which the objective is to maximise the profits achieved by taking part in the electricity market. Our approach is illustrated in a case study. PV producers could gain by taking part in the markets for balancing power or ancillary services despite the negative impact on profit of several types of uncertainty, notably the intermittent nature of the PV source.     

Optimization of a photovoltaic pumping system based on the optimal control theory

This paper suggests how an optimal operation of a photovoltaic pumping system based on an induction motor driving a centrifugal pump can be realized. The optimization problem consists in maximizing the daily pumped water quantity via the optimization of the motor efficiency for every operation point. The proposed structure allows at the same time the minimization the machine losses, the field oriented control and the maximum power tracking of the photovoltaic array. This will be attained based on multi-input and multi-output optimal regulator theory. The effectiveness of the proposed algorithm is described by simulation and the obtained results are compared to those of a system working with a constant air gap flux.     

A model for optimal sizing of photovoltaic irrigation water pumping systems

The previous methods for optimal sizing of photovoltaic (PV) irrigation water pumping systems separately considered the demand for hydraulic energy and possibilities of its production from available solar energy with the PV pumping system. Unlike such methods, this work approaches the subject problem systematically, meaning that all relevant system elements and their characteristics have been analyzed: PV water pumping system, local climate, boreholes, soil, crops and method of irrigation; therefore, the objective function has been defined in an entirely new manner. The result of such approach is the new mathematical hybrid simulation optimization model for optimal sizing of PV irrigation water pumping systems, that uses dynamic programming for optimizing, while the constraints were defined by the simulation model. The model was tested on two areas in Croatia, and it has been established that this model successfully takes into consideration all characteristic values and their relations in the integrated system. The optimal nominal electric power of PV generator, obtained in the manner presented, are relatively smaller than when the usual method of sizing is used. The presented method for solving the problem has paved the way towards the general model for optimal sizing of all stand-alone PV systems that have some type of energy storage, as well as optimal sizing of PV power plant that functions together with the storage hydroelectric power plant.     

Methodology for optimal sizing of stand-alone photovoltaic/wind-generator systems using genetic algorithms

A methodology for optimal sizing of stand-alone PV/WG systems is presented. The purpose of the proposed methodology is to suggest, among a list of commercially available system devices, the optimal number and type of units ensuring that the 20-year round total system cost is minimized subject to the constraint that the load energy requirements are completely covered, resulting in zero load rejection. The 20-year round total system cost is equal to the sum of the respective components capital and maintenance costs. The cost (objective) function minimization is implemented using genetic algorithms, which, compared to conventional optimization methods such as dynamic programming and gradient techniques, have the ability to attain the global optimum with relative computational simplicity. The proposed method has been applied for the design of a power generation system which supplies a residential household. The simulation results verify that hybrid PV/WG systems feature lower system cost compared to the cases where either exclusively WG or exclusively PV sources are used.     

Test facility in Port Said-Egypt for photovoltaic solar generators

In framework of an applied research project a test facility for evaluating the performance of photovoltaic (PV) solar generators has been implemented at the Faculty of Engineering in Port Said-Egypt. The goals of the project is to perform the different required tests on photovoltaic (PV) solar generators in order to verify the fulfillment of the international standard specifications and to verify the characteristics given by the manufacturer. This will be achieved determining the electrical, the thermal and the mechanical characteristics of the module. This test can be considered to be a preparation for Egyptian PV market helping for propagation and harmonisation of standards. The developed test facility is including the main tests of PV systems, e.g. the electrical output under normal operating conditions and the influence of different environmental factors.     

A system dynamics approach for the photovoltaic energy market in Spain

The goal of this paper is to contribute to understanding the behaviour of the photovoltaic (PV) sector in Spain and its expectations under possible scenarios. Currently, PV solar energy is not a profitable sector by itself. Therefore, the Spanish government, like the governments of other countries, has stimulated investment with subsidies. The spectacular increase of PV facilities exceeded all forecasts and the government decided to curb the trend. The present hypothesis is that continuing with this support to PV energy, the technological advances and the economy generated from the production of panels would be able to make the sector profitable in the future without the necessity of subventions. Based on this hypothesis, a computer simulation model was built using the system dynamics methodology. To test its utility, the model was challenged to fit the historical data and to explore several futures over the next few years. The model allows an understanding of the sector's behaviour under the latest policies of the Spanish government, thus helping to design future public policies. The simulation results are different depending on the adopted policy and the scenario. Therefore, these factors will determine the success or failure of the investments in this type of energy.     

Life cycle assessment of photovoltaic electricity generation

The paper presents the results of a life cycle assessment (LCA) of the electric generation by means of photovoltaic panels. It considers mass and energy flows over the whole production process starting from silica extraction to the final panel assembling, considering the most advanced and consolidate technologies for polycrystalline silicon panel production. Some considerations about the production cycle are reported; the most critical phases are the transformation of metallic silicon into solar silicon and the panel assembling. The former process is characterised by a great electricity consumption, even if the most efficient conversion technology is considered, the latter by the use of aluminium frame and glass roofing, which are very energy-intensive materials. Moreover, the energy pay back time (EPBT) and the potential for CO₂ mitigation have been evaluated, considering different geographic collocations of the photovoltaic plant with different values of solar radiation, latitude, altitude and national energetic mix for electricity production.     

Multiobjective Particle Swarm Optimization for the optimal design of photovoltaic grid-connected systems

Particle Swarm Optimization (PSO) is a highly efficient evolutionary optimization algorithm. In this paper a multiobjective optimization algorithm based on PSO applied to the optimal design of photovoltaic grid-connected systems (PVGCSs) is presented. The proposed methodology intends to suggest the optimal number of system devices and the optimal PV module installation details, such that the economic and environmental benefits achieved during the system’s operational lifetime period are both maximized. The objective function describing the economic benefit of the proposed optimization process is the lifetime system’s total net profit which is calculated according to the method of the Net Present Value (NPV). The second objective function, which corresponds to the environmental benefit, equals to the pollutant gas emissions avoided due to the use of the PVGCS. The optimization’s decision variables are the optimal number of the PV modules, the PV modules optimal tilt angle, the optimal placement of the PV modules within the available installation area and the optimal distribution of the PV modules among the DC/AC converters.     

Modelling of a double-glass photovoltaic module using finite differences

A simulation model of finite differences describing a double-glass multi-crystalline photovoltaic module has been developed and validated using experimental data from such a photovoltaic module. This simulation model is based on various thermal hypotheses, particularly concerning the convective transfer coefficients: thus, various hypotheses found in the literature have been tested and the best one has been accepted. Using this modelling procedure, the cell temperature is estimated with a root mean square error of 1.3 °C.     

Modeling and control of photovoltaic and fuel cell based alternative power systems

Photovoltaic (PV) systems and fuel cells (FCs) represent interesting solutions as being alternative power sources with high performance and low emission. This work presents a modeling and control study of two power generators; photovoltaic array and fuel cell based systems. An MPPT approach to optimize the PV system performances is proposed. The PV system consists of a PV array connected to a DC-DC buck converter and a resistive load. A maximum power point tracker controller is required to extract the maximum generated power. Based on Incremental Conductance (INC) principle, the idea of the proposed control is to use a Fuzzy Logic Controller (FLC) that allows the choice of the duty cycle step size which is used to be fixed in conventional MPPT algorithms. The variable step is computed according to the value of the PV power-voltage characteristic slope. The second working system comprises a controlled DC-DC converter fed by a proton exchange membrane fuel cell (PEMFC) and supplies a DC bus. The mathematical model of the PEMFC system is given. The converter duty cycle is adjusted in order to regulate the DC bus voltage. Obtained simulation results validate the control algorithms for both of studied power systems.