Optimisation and techno-economic analysis of autonomous photovoltaic–wind hybrid energy systems in comparison to single photovoltaic and wind systems

A techno-economic analysis for autonomous small scale photovoltaic–wind hybrid energy systems is undertaken for optimisation purposes in the present paper. The answer to the question whether a hybrid photovoltaic–wind or a single photovoltaic or wind system is techno-economically better is also sought. Monthly analysis of 8 year long measured hourly weather data shows that solar and wind resources vary greatly from one month to the next. The monthly combinations of these resources lead to basically three types of months: solar-biased month, wind-biased month and even month. This, in turn, leads to energy systems in which the energy contributions from photovoltaic and wind generators vary greatly. The monthly and yearly system performances simulations for different types of months show that the system performances vary greatly for varying battery storage capacities and different fractions of photovoltaic and wind energy. As well as the system performance, the optimisation process of such hybrid systems should further consist of the system cost. Therefore, the system performance results are combined with system cost data. The total system cost and the unit cost of the produced electricity (for a 20 year system lifetime) are analysed with strict reference to the yearly system performance. It is shown that an optimum combination of the hybrid photovoltaic–wind energy system provides higher system performance than either of the single systems for the same system cost for every battery storage capacity analysed in the present study. It is also shown that the magnitude of the battery storage capacity has important bearings on the system performance of single photovoltaic and wind systems. The single photovoltaic system performs better than a single wind system for 2 day storage capacity, while the single wind system performs better for 1.25 day storage capacity for the same system cost.     

Monitoring,modelling and simulation of PV systems using LabVIEW

This paper presents a detailed characterization of the performance and dynamic behaviour of photovoltaic systems by using LabVIEW real-time interface system. The developed software tool integrates several types of instruments into a single system which is able to offer online measurements all data sources and comparison simulation results with monitored data in real-time. Comprehensive monitoring and analyzing of PV systems play a very important role. The proposed method is a low-cost solution to provide fast, secure and reliable system by making the system database-ready for performance analysis of PV systems. The proposed method is also applied to a grid connected PV system in the Centre de Developpement des Energies Renouvelables (CDER) in Algeria. The results show that there is a good agreement between the measured and simulation results values. The integration methodology of robust simulation and monitored data in real-time can be extended to study the fault diagnosis of a PV system.     

Performance analysis of a PV-powered health clinic with multi-stagedual priority regulator

The performance of a photovoltaic powered health clinic system designed, built, and evaluated at the University of Lowell is investigated. This system uses two separate batteries, one to power a vaccine refrigerator and the other to power auxiliary loads. The two batteries were sized according to the demand of their loads. The power control system utilizes a five-stage dual priority controller to charge the two separate batteries from a single modular photovoltaic array. The main refrigerator battery always has priority over the auxiliary battery; therefore, the use of auxiliary loads will never jeopardize the reliability of the critical load. This system provides power for auxiliary loads while utilizing the same number of photovoltaic modules as systems which power only a vaccine refrigerator. The performance of this system was evaluated using a data acquisition system, and the experimental results are compared with theoretical values     

Performance of stand-alone photovoltaic systems using measured meteorological data for Algiers

In order to estimate the performance of photovoltaic (PV) systems, we develop a real time expert system based on central microcomputer used as microserver and easily consultable with different automatic stations. We present in this paper, the principles and specificities of the measurement system and of the automatic data measuring device and its sensors, and also some aspects of the database and expert system developed for this application. We propose a method based on the determination of the loss-of-load probability (LLP), which allows the estimation of the optimum combination of battery capacity (C_s) and photovoltaic array peak power (P_c). The problem consists of determining the combination which corresponds to a minimum total system cost.     

Design and development of a data acquisition system for photovoltaic modules characterization

Testing photovoltaic generators performance is complicated. This is due to the influence of a variety of interactive parameters related to the environment such as solar irradiation and temperature in addition to solar cell material (mono-crystalline, poly-crystalline, amorphous and thin films). This paper presents a computer-based instrumentation system for the characterization of the photovoltaic (PV) conversion. It based on a design of a data acquisition system (DAQS) allowing the acquisition and the drawing of the characterization measure of PV modules in real meteorological test conditions.     

The potential for integration of hydrogen for complete energy self-sufficiency in residential buildings with photovoltaic and battery storage systems

This paper presents an analysis of energy production in a pilot building located in Slovenia, which is a typical residential house with an installed photovoltaic (PV) system and pilot battery storage system. Energy management system gathers data from smart meters every 15 min. As the pilot building location is in central Europe, complete energy self-sufficiency cannot be provided. The most problematic period of energy production with photovoltaic systems is winter. Solar radiation during the winter is much lower than in the summer and sometimes snow covers photovoltaic panels and disables energy production. Energy production and energy consumption are analyzed for one year. This study shows that complete self-sufficiency can be achieved by supplementing photovoltaic systems with hydrogen fuel cells. The amount of hydrogen, which would suffice for complete self-sufficiency for the whole period, is calculated according to the analyzed data. A synergy between photovoltaic system and hydrogen fuel cells is a step forward to complete self-sufficiency with renewable energy sources. The share of self-sufficiency of a hybrid PV fuel cell system would be 62.13%, meaning that there is no possibility for complete self-sufficiency from the pilot system. The shortage of hydrogen is 144.24 kg for one year and for achieving complete energy self-sufficiency, PV system should be bigger. A hybrid system with photovoltaic system, battery storage system and hydrogen fuel cells can be a solution for complete self-sufficiency. From an economic point of view, such systems are accessible for commercial use. The initial investment is relatively high, because of the high cost of the hydrogen storage tank.     

Status of flat-plate photovoltaic systems for applications in developing countries

This paper discusses the status of flat-plate photovoltaic (PV) system technology, performance and cost for applications in developing countries. Comparison of key electrical service performance factors is made between PV and conventional generating systems. PV module reliability results from 23 field tests are summarized and the effect of failure on system performance is discussed. Cost algorithms, drawn from historial data, are defined and applied to obtain PV system selling price as a function of worst-month insolation and for several values of loss-of-energy-probability, (LOEP), an index of performance. Comparison is made of levelized energy cost between PV and diesel-generator systems. Projections of PV system selling price, major component costs and system levelized energy cost to the mid-1980s and 1990s are displayed and the implications discussed. It was concluded that PV system technical viability had been confirmed and commercial development is well advanced. PV system electrical service performance is generally superior to service performance provided by the electric grid or diesel in rural and remote areas. At present, for many applications having an annual electrical demand of up to 4 to 10 MWH, the levelized energy cost of PV systems in regions of good insolation is less than for diesel generators. Within 20 yr, if cost projections are borne out, photovoltaics will become the least expensive and most reliable source for most decentralized electric power in the developing world.     

Improvement of photovoltaic pumping systems based on standard frequency converters by means of programmable logic controllers

Photovoltaic pumping systems (PVPS) based on standard frequency converters (SFCs) are currently experiencing a growing interest in pumping programmes implemented in remote areas because of their high performance in terms of component reliability, low cost, high power range and good availability of components virtually anywhere in the world. However, in practical applications there have appeared a number of problems related to the adaptation of the SFCs to the requirements of the photovoltaic pumping systems (PVPS). Another disadvantage of dedicated PVPS is the difficulty in implementing maximum power point tracking (MPPT). This paper shows that these problems can be solved through the addition of a basic industrial programmable logic controller (PLC) to the system. This PLC does not increase the cost and complexity of the system, but improves the adaptation of the SFC to the photovoltaic pumping system, and increases the overall performance of the system.     

Loss-of-load probability of photovoltaic water pumping systems

This paper presents a method for estimating the loss-of-load probability (LLP) of a photovoltaic water pumping system. The study has been carried out for a constant profile, using a tank with a two day autonomy capacity and two pumping heads applied to a centrifugal pump. The method developed in this paper gives a simple tool for LLP calculation. The procedure can also be used to draw LLP maps with normalised parameters using long term observed or generated sequences of meteorological data. This technique gives a generalised and practical graphical tool for systems sizing. Some examples from Algeria are used. But the method can be applied to any geographical area.     

Low light conditions modelling for building integrated photovoltaic (BIPV) systems

The low irradiance efficiency of photovoltaic modules is important to the optimization of BIPV systems. When photovoltaic modules are integrated into a building, architectural design considerations compete with maximizing photovoltaic energy production. As a result, BIPV arrays are often not facing south and are frequently mounted vertically. Under these conditions, a greater portion of the total sunlight striking the array is diffuse or at high angles of incidence. In northern latitudes a significant amount of the total yearly energy is produced at low light levels.A grid-connected array of BIPV modules integrated into the BCIT Technology Centre building in Burnaby, B.C. was used for assessing the accuracy of an energy performance model developed for BIPV systems. The BIPV system uses AC modules and a computerized data acquisition system for monitoring the performance of modules and inverters. The performance model was developed from analysis of the open circuit voltage, maximum power point voltage and maximum power point current of the individual modules comprising the BIPV array.The algorithm for calculating power output of the photovoltaic array is derived from the ideal diode equation using the single diode model of a photovoltaic cell. An empirically derived parameter modifies the equation. Once the parameters for different module technologies are established, it is possible to compare their annual performance in a BIPV system.     

Systematic procedures for sizing photovoltaic pumping system,using water tank storage

In this work, the performances of the photovoltaic pumping destined to supply drinking water in remote and scattered small villages have been studied. The methodology adopted proposes various procedures based on the water consumption profiles, total head, tank capacity and photovoltaic array peak power. A method of the load losses probability (LLP) has been used to optimize sizing of the photovoltaic pumping systems with a similarity between the storage energy in batteries and water in tanks. The results were carried out using measured meteorological data for four localities in Algeria: Algiers and Oran in the north, Bechar and Tamanrasset in the south. The results show that the performance of the photovoltaic pumping system depends deeply on the pumping total head and the peak power of the photovoltaic array. Also, for the southern localities, the LLP method shows that the size of the photovoltaic array varies versus LLP on a small scale. On the other hand, for the northern localities, the sizing of the photovoltaic array is situated on a large scale power. Because of the current high crud-oil price, the photovoltaic pumping still to be the best adopted energy resource to supply drinking water in remote and scattered villages.     

Dynamic modeling and sizing optimization of stand-alone photovoltaic power systems using hybrid energy storage technology

Economic and environmental concerns over fossil fuels encourage the development of photovoltaic (PV) energy systems. Due to the intermittent nature of solar energy, energy storage is needed in a stand-alone PV system for the purpose of ensuring continuous power flow. Three stand-alone photovoltaic power systems using different energy storage technologies are studied in this paper. Key components including PV modules, fuel cells, electrolyzers, compressors, hydrogen tanks and batteries are modeled in a clear way so as to facilitate the evaluation of the power systems. Based on energy storage technology, a method of ascertaining minimal system configuration is designed to perform the sizing optimization and reveal the correlations between the system cost and the system efficiency. The three hybrid power systems, i.e., photovoltaic/battery (PV/Battery) system, photovoltaic/fuel cell (PV/FC) system, and photovoltaic/fuel cell/battery (PV/FC/Battery) system, are optimized, analyzed and compared. The obtained results indicate that maximizing the system efficiency while minimizing system cost is a multi-objective optimization problem. As a trade-off solution to the problem, the proposed PV/FC/Battery hybrid system is found to be the configuration with lower cost, higher efficiency and less PV modules as compared with either single storage system.     

Assessment of a photovoltaic pumping system in the areas of the Algerian Sahara

We present a methodology to analyze the performance of a photovoltaic system of pumping installed in an isolated site at Ghardaïa (southern of Algeria). A computer program which simulates the electric operation of the system (irradiation and production of water) on the hourly basis was developed while being based on the data of irradiation of the site of year 2005, measured with a step of 5 min. This work allows to evaluate the economic interest of the system which will have to satisfy an average daily volume of 60 m³ throughout the year compared to another very widespread energy system in the area, the diesel genset (DG), by using the method of the life cycle cost (LCC). Considering the economic realities of the Algerian market where the price of the fuel is very low, it makes it difficult to other energy processes to emerge.     

Optimal sizing of photovoltaic pumping system with water tank storage using LPSP concept

This paper recommends an optimal sizing model, to optimize the capacity sizes of different components of photovoltaic water pumping system (PWPS) using water tank storage. The recommended model takes into account the submodels of the pumping system and uses two optimization criteria, the loss of power supply probability (LPSP) concept for the reliability and the life cycle cost (LCC) for the economic evaluation.With this presented model, the sizing optimization of photovoltaic pumping system can be achieved technically and economically according to the system reliability requirements. The methodology adopted proposes various procedures based on the water consumption profiles, total head, tank capacity and photovoltaic array peak power. A case study is conducted to analyze one photovoltaic pumping project, which is designed to supply drinking water in remote and scattered small villages situated in Ghardaia, Algeria (32°29′N, 3°40′E, 450 m).     

Economic analysis of PV/diesel hybrid system with flywheel energy storage

This paper analyzes a hybrid energy system performance with photovoltaic (PV) and diesel systems as the energy sources. The hybrid energy system is equipped with flywheel to store excess energy from the PV. HOMER software was employed to study the economic and environmental benefits of the system with flywheels energy storage for Makkah, Saudi Arabia. The analysis focused on the impact of utilizing flywheel on power generation, energy cost, and net present cost for certain configurations of hybrid system. Analyses on fuel consumption and carbon emission reductions for the system configurations were also presented in this paper.     

Terrestrial concentrating photovoltaic power system studies

Studies aimed at defining the role of sunlight concentration in reducing the cost of electrical energy generated by terrestrial photovoltaic systems are described. These studies use computer modelling to (a) compare silicon cells and gallium arsenide cells in concentrating systems, (b) investigate the operation of photovoltaic systems in low insolation locations and (c) evaluate the effect of wind dependent thermal conductances on performance of passively cooled systems. Optimum fixed energy costs occur at higher aperature to cell area ratios for GaAs systems compared to silicon systems due to the better high temperature performance and increased costs of GaAs. Results based on currently available data show that concentrating systems should not be ruled out relative to fixed flat unconcentrated arrays even for low solar irradiation locations such as Cleveland. The wind dependent thermal conductance studies show that for precise modeling the effect of wind speed should be considered in locations having large wind speed deviations from the yearly mean. However, with the present uncertainties in cost inputs, the use of average values is quite appropriate.     

ANFIS-based modelling for photovoltaic power supply system: A case study

Due to the various seasonal, monthly and daily changes in meteorological data, it is relatively difficult to find a suitable model for Photovoltaic power supply (PVPS) system. This paper deals with the modelling and simulation of a PVPS system using an Adaptive Neuro-Fuzzy Inference Scheme (ANFIS) and the proposition of a new expert configuration PVPS system. For the modelling of the PVPS system, it is required to find suitable models for its different components (ANFIS PV generator, ANFIS battery and ANFIS regulator) that could give satisfactory results under variable climatic conditions in order to test its performance and reliability. A database of measured climate data (global radiation, temperature and humidity) and electrical data (photovoltaic, battery and regulator voltage and current) of a PVPS system installed in Tahifet (south of Algeria) has been recorded for the period from 1992 to 1997. These data have been used for the modelling and simulation of the PVPS system. The results indicated that the reliability and the accuracy of the simulated system are excellent and the correlation coefficient between measured values and those estimated by the ANFIS gave a good prediction accuracy of 98%. Additionally, test results show that the ANFIS performed better than the Artificial Neural Network (ANN), which has also being tried to model the system. In addition, a new configuration of an expert PVPS system is proposed in this work. The predicted electrical data by the ANFIS model can be used for several applications in PV systems.     

Renewable electrolytic hydrogen potential in Algeria

The present paper deals with the assessment of the renewable hydrogen production potential in Algeria. The studied system produces hydrogen by electrolysis of water; electricity is supplied by a photovoltaic generator. Adequate mathematical models were used to calculate the electrolytic hydrogen production. Detailed hourly simulations were used to assess the potential for the entire country and to draw it maps. Throughout this study, the influence of the tilt angle of a photovoltaic generator has been investigated. It has been observed that the tilt angle has an impact on solar energy received by the photovoltaic generator, the produced solar electrical power and the rate of hydrogen production. We have calculated the optimal angles to maximize each element. We were particularly interested in the optimal angle to maximize hydrogen production. We found that the solar hydrogen potential for Algeria varies from 0.10 Nm³/m²/d to 0.14 Nm³/m²/d. This potential is quite significant, especially in the arid region of southeastern Algeria. The lowest potential is located in the northeast region. For stand-alone systems, it is important to assess the minimum available level, as their sizing takes into account the most unfavorable case. This level is between 0.07 Nm³/m²/d and 0.13 Nm³/m²/d. This shows that, even for a stand-alone system, the potential is quite high. Finally, we provide robust correlations that allow calculating the potential and the angle of inclination maximizing it for the whole of Algeria.     

Investigating the effects of solar modelling using different solar irradiation data sets and sources within South Africa

When designing a solar photovoltaic (PV) system, the main aim of the designer is to optimise the system through the correct choice in sizing of system components (i.e.: size of PV array versus number of batteries for storage), whilst at the same time keeping the overall systems costs as low as possible. The choice of data provider and method for measuring the solar irradiance data in W/m² for a specific geographical location is therefore a critical determinant to ensure maintenance of the desired level of accuracy for the system design. The use of a data set which either over predicts or under predicts the amount of available solar irradiation at a specific location will therefore affect the electrical performance of the system, as the real world conditions may differ considerably to the data set used in the modelling of the system design. This paper specifically deals with the modelling of an off-grid photovoltaic power supply system using three different sources of solar irradiance data for two specific geographical locations within South Africa. The principal aim of the paper is to show that satellite data over-estimates solar irradiance and hence underestimates the initial cost of a solar PV system needed to meet the load in question.