The aim of the present work is to investigate the efficiency of flat-plate solar panels in Greece for delivering solar energy. In this study, the solar panels are mounted on a two-axis tracker, which follows the daily path of the sun. In this context, the annual energy sums are estimated on such surfaces from hourly solar horizontal radiation values at forty-three locations, covering all of Greece. The solar horizontal radiation values are embedded in the typical meteorological years of the sites obtained from the PVGIS tool. All calculations use near-real surface-albedo values for the sites, and isotropic and anisotropic models are used to estimate the diffuse-inclined radiation. The analysis provides non-linear regression expressions for the energy sums as a function of time (month, season). The annual energy sums are found to vary between 2247 kWhm−2 and 2878 kWhm−2 under all-sky conditions with the anisotropic transposition model. Finally, maps of Greece showing the distribution of the annual and seasonal solar energy sums under all- and clear-sky conditions are derived for the first time, and these maps constitute the main innovation of this work.
In the present study, the most prevalent space heating (SH) systems are assessed by means of probabilistic economic method, for Athens (Greece) under the ongoing energy crisis. The examined SH systems are the air source heat pump, the natural gas boiler and the oil boiler. An apartment of 85 m2 living area is chosen as the standard Athenian dwelling type for the assessment of the SH systems. In addition, two economic scenarios are set related to the annual energy inflation rate, the pessimistic and the optimistic. Simulations are executed in TRNSYS for the physical system and in MATLAB for the economic analysis. The economic analysis is carried out with the combination of the Monte Carlo simulations and the Life Cycle Cost (LCC) method. It turned out that, the LCC (as net present value) for all systems is much higher than the pre-crisis cost and is not feasible under the existing obscure economic period. It was proved that, the energy cost subsidy may be a solution on the volatility of the energy market, however, this can be achieved with rather high subsidy rates. The air source heat pump system was found to obtain better economy than the conventional fuel-based systems and the pairing of the heat pump with the PV system proved as the only economic feasible solution. The developed methodology can be utilized for evaluating the investment risk associated with the uncertain of the future cost of energy.
A three-dimensional steady-state model has been developed to study the phenomena that occurs during Proton Exchange Membrane Fuel Cell’s (PEMFC) operation. Electrochemical and transport phenomena on both the anode and cathode sides were investigated. Particular emphasis has been given to the composition and structure of the catalyst layers (CLs), considering parameters such as the metal loading, the most effective specific metal surface, the agglomeration, and the particle size. In this context, two types of CLs were investigated. The first type concerns conventional CLs consisting of Pt/C, while the second type refers to bimetallic CLs consisting of Pt-Ru/C. In both cases, the CLs were examined for various loadings of Pt, Ru, and C to define the optimum atomic ratio for an enhanced PEMFC performance, while, in parallel, possible challenges are intedified. The mathematical model for simulating the entire phenomena and the method for modeling the bimetallic catalyst layers are presented. The results show a good agreement between the model and the experimental data reported in the literature. Additionally, the scenario of bimetallic CLs consisting of Pt-Ru/C with a ratio of 50-50 (Pt-Ru) significantly improved the overall PEMFC electrochemical performance.
Solar azimuth may become indefinite at sunrise and sunset. This discrepancy is corrected in the present work. The correction concerns application of Fourier–series analysis to the solar paths over a site during days when the problem arises. The result is the derivation of a new curve that is fitted with great accuracy to the daily solar azimuth values, thus bridging the gap of the discontinuity. A demonstration for the solar azimuth correction is given for 3 sites around the world (Athens, Stockholm, and Sydney). The correction can be applied to any solar geometry code; in this work the algorithm of the XRONOS code is selected without (XRONOS.bas, a BASIC programme) and with (XRONOS.m, a MATLAB code) the correction proposed. A corrected expression for the atmospheric refractive index at various altitudes is given in Appendix A as the refraction of solar right is treated in XRONOS.
The main categories of solar water heating systems (SWHSs) are the thermosyphon and the forced circulation (FC). This paper presents an experiment carried out with the aim to compare the energy performance of the FC with a thermosyphon SHWS. Identical SWHSs were installed side by side at the University of West Attica in Athens, Greece. Domestic hot water load was applied to both systems via a microcontroller-based dispensing unit which mimics the demand profile. The trial period comprised the last two months of spring (April and May). For the first law assessment, two energy indicators were utilized: the solar fraction (SF) and the thermal efficiency of the system (ηth). On days with distinctive weather conditions, both systems obtained approximately equal SF and ηth values, without a specific preference between the ambient conditions and the type of SWHS. Regarding a four-day nonstop operation, the FC overperformed the thermosyphon system at both energy indicators. Namely, for the FC and the thermosyphon SWHS, the SF was calculated to be 0.62 and 0.48, and the ηth was 68.2% and 53.3%, respectively.
The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies. Like any technology, fuel cells face drawbacks that scientific society has been focused on to improve and optimize the overall technology. Thus, the cost is the main inhibitor for this technology due to the significantly high cost of the materials used in catalyst layers. The current discussion mainly focuses on the fundamental electrochemical half-cell reaction of hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) that are taking place in the catalyst layers consisting of Platinum-based and Platinum-non noble metals. For this purpose, studies from the literature are presented and analyzed by highlighting and comparing the variations on the catalytic activity within the experimental catalyst layers and the conventional ones. Furthermore, an economic analysis of the main platinum group metals (PGMs) such as Platinum, Palladium and Ruthenium is introduced by presenting the economic trends for the last decade.
Hydrogen (H2) can be a promising energy carrier for decarbonizing the economy and especially the transport sector, which is considered as one of the sectors with high carbon emissions due to the extensive use of fossil fuels. H2 is a nontoxic energy carrier that could replace fossil fuels. Fuel Cell Electric Vehicles (FCEVs) can decrease air pollution and reduce greenhouse gases when H2 is produced from Renewable Energy Sources (RES) and at the same time being accessible through a widespread network of Hydrogen Refueling Stations (HRSs). In this study, both the sizing of the equipment and financial analysis were performed for an HRS supplied with H2 from the excess electrical energy of a 10 MW wind park. The aim was to determine the optimum configuration of an HRS under the investigation of six different scenarios with various numbers of FCEVs and monthly demands, as well as ascertaining the economic viability of each examined scenario. The effect of the number of vehicles that the installation can refuel to balance the initial cost of the investment and the fuel cost in remote regions was investigated. The results showed that a wind-powered HRS could be a viable solution when sized appropriately and H2 can be used as a storage mean for the rejected wind energy. It was concluded that scenarios with low FCEVs penetration have low economic performance since the payback period presented significantly high values.
Fuel cells are promising energy conversion devices exhibiting high electrical efficiencies and zero emissions when green hydrogen is employed as a fuel feedstock, with applications in both the mobility and stationary sectors. This paper presents a comprehensive review on anode and cathode layer macroscopic modelling studies for proton exchange membrane fuel cells (PEMFCs) that incorporate in a coupled manner both the electrochemical and transport (mass, heat and momentum) phenomena taking place at each compartment. The reviewed models have been classified according to their spatial dimensions into one-dimensional, two-dimensional and three-dimensional, giving particular emphasis on the examination of both catalyst layers. For each examined case, valuable information is provided regarding the modelling technique applied, the assumptions that have been made, and the validation procedure followed. This review includes essential information regarding the suitability of each simulation method to understand the impact of electro-catalysts’ physicochemical properties on the overall PEMFC electrochemical performance. In this sense, the requirement to simulate PEMFCs operation by investigating several alternative electrode material composites is underlined to provide a credible pathway to improve cell performance and minimize or even eliminate the incorporation of costly materials such as platinum or platinum group metals (PGM) in the anode and cathode electrodes.
To help stakeholders plan, research, and develop Hybrid Renewable Energy Systems (HRES), the elaboration of numerous modelling techniques and software simulation tools has been reported. The thorough analysis of these undoubtedly complex systems is strongly correlated with the efficient utilisation of the potential of renewable energy and the meticulous development of pertinent designs. In this context, various optimisation constraints/targets have also been utilised. This specific work initially carries out a thorough review of the modelling techniques and simulation software developed in an attempt to define a commonly accepted categorisation methodology for the various existing HRES simulation methods. Moreover, the widely utilised optimisation targets are analysed in detail. Finally, it identifies the sensitivity of two commercial software tools (HOMER Pro and iHOGA) by examining nine case studies based on different wind and solar potential combinations. The results obtained by the two commercial tools are compared with the ESA Microgrid Simulator, a software developed by the Soft Energy Applications and Environmental Protection Laboratory of the Mechanical Engineering Department of the University of West Attica. The evaluation of the results, based on the diversification of the renewable energy potential used as input, has led to an in-depth assessment of the deviances detected in the software tools selected.
The energy cost fluctuations along with the gradual decrease of natural resources (i.e. oil, natural gas, coal) and the environmental issues raised by the extended use of fossil fuels, leads to the urgent development of advanced and clean energy systems. On top of that, the European Union requests new climate and energy targets to be supplied from Renewable Energy Sources until 2030. One of the main barriers to reach these targets is the stochastic character of RES combined with the demand fluctuations during the operation of the energy systems. In this direction, hydrogen technology can contribute as an energy carrier that can be produced by supplying electricity from RES to electrolysis modules without emitting hazardous gasses and then storing it at the metal hydride canisters for future use via fuel cell (FC) systems. Modeling these systems is important for achieving optimal sizing and being beneficial in both energy and economic aspects, while at the same time RES penetration is increased. For the accurate understanding of the hydrogen systems and especially FCs, it is important to comprehend the operating principles and both thermodynamic and electrochemical phenomena. In the present study, an integrated mathematical model is proposed concerning the electrical and thermal behavior of the FC. The model developed is able to simulate the operation of FC by using FC’s technical specifications. The reliability of the model was validated under three different hydrogen flow patterns applied in the experimental configuration NEXA 1.2 kW. The proposed model was applied to a specific case study for optimum sizing of a FC system in terms of maximum hydrogen absorption under a hydrogen production pattern from electrolysis utilizing excess energy from a wind park installed in an autonomous grid island network.
A typical meteorological year (TMY) is a set of meteorological and solar radiation parameters usually consisting of hourly values in a year for a given geographical location. Such TMYs have been derived in many countries for various applications. In Greece, TMYs have been generated mainly for Athens. The present work derives TMYs for 33 locations in Greece distributed all over the country and covering its 4 climatic zones defined for energy purposes. The TMYs are based on meteorological data collected from the Hellenic National Meteorological Service network in Greece in the period 1985–2014. The solar radiation needed in the generation of the TMYs is derived by using the meteorological radiation model. The TMY at every one of the 33 locations is provided in 5 versions to adapt to the applications of meteorology-climatology, bio-meteorology, agro-meteorology-hydrology, photovoltaics, and energy design of buildings. The 5 versions of the TMYs are generated following the modified Sandia National Laboratories method. After their generation, each version of the TMYs at any of the 33 locations is compared with the annualand monthly-averaged values of the selected parameters of the initial 30-year database. The comparison shows that the errors (differences) do not usually exceed 5%, thus supporting the fact that the so-derived TMYs are representative of the sites selected. Also, the distribution of the errors follows the normal distribution curve.
The objective of the present work is the medium, short and very short-term prognosis of load demand (LD) for the small-scale island of Tilos in Greece. For this purpose, Artificial Neural Network (ANNs) models were developed to forecast the LD of Tilos for different prediction horizons and time intervals, these covering the cases of 24 h ahead in hourly intervals (medium term prognosis), 2 h ahead in 10-min intervals (short term prognosis) and 10-min ahead in 1-min intervals (very short term prognosis). At the same time, stochastic/persistence autoregressive (AR) models were also developed and compared with the respective ANN models with regards to the LD prediction results obtained. For the training of the developed ANNs, meteorological data covering the period 2015 e 2017 were used, which had been recorded in 1-min intervals by two meteorological masts installed on the island Tilos. Furthermore, the biometeorological human thermal comfort-discomfort index, known as the cooling power index (CP), was also estimated and introduced in the training procedure of the forecasting models, while, for the evaluation of both AR and ANN forecasting models, well established statistical evaluation indices were applied. To this end, results show that in all cases covered, i.e. for both medium and short-term prognoses, the developed ANN forecasting models present a remarkable ability to predict the local LD of the island with high accuracy, enabling in this way the development of advanced energy management tools for both end-users and the system operators.
The rapid increase of world energy demand over the past decades has led to an extensive exploitation of the planet’s natural resources. Given that the population growth will continue for the next decades, there is an urgent need for a switch to Renewable Energy Sources (RES). One of the promising solutions to the energy problem is the geothermal energy which consists of stored energy in the earth in the form of water or steam at high pressure and temperature. Countries located in seismic zones possess a high geothermal potential due to their position at destructive and constructive plate margins. Greece is one of the countries with a remarkable potential in geothermal energy of medium and high enthalpy fields. Interest in the exploitation of geothermal fields for electricity generation is mainly focused on non-interconnected Greek islands, where energy is produced from oil-based generators with high energy cost and low-quality electricity, mainly during the summer months which is a period of high energy demand. In this respect, the present study investigates the possibility of combining a geothermal power plant with a concentrated solar array to provide energy to an autonomous island grid. Since the productivity of geothermal fields is gradually decreasing over the years, the combination of solar with geothermal energy source aims to the extension of the productive lifetime of the field, achieved by reheating the geothermal fluid during reinjection to the injection well. The thermal energy, generated by concentrated solar collectors, increases the temperature of the geothermal brine and reduces the energy degradation of the field. In this study, the energy efficiency of different reheat values are studied in order to achieve the combination of a geothermal power plant and a concentrated solar field that can meet specific targets for lifetime energy production. According to the results, the proposed installation can merely contribute to the energy autonomy of the island grid during periods of low demand and provide energy security in periods of high energy consumption.
Assessment of the electricity generation status for Non-Interconnected Islands (NIIs) of the Aegean Sea region, excluding the electricity systems of Crete and Rhodes, is undertaken in the current study. The authors focus on the long-term analysis of thermal power generation characteristics and also on the challenges so far limiting the contribution of Renewable Energy Sources (RES) in covering the electricity needs of the specific area. According to the present analysis, due to the existing technical limitations, the annual RES shares in the electricity balance of NIIs of the Aegean Sea have since 2010 stagnated in the range of 15% to 18%. Moreover, the performance of thermal power stations for all 30 NII systems is evaluated on the basis of their utilization factor, associated fuel consumption and electricity production costs. The vast majority of these stations is characterized by low capacity factors in combination with high specific fuel consumption and high operational expenses that in the case of smaller scale island regions could even exceed 600€/MWh. At the same time, the authors discuss on the alternatives and encourage further investigation of novel, intelligent energy solutions, such as the smart microgrid and battery-based hybrid power station that are currently developed on the island of Tilos under the implementation of the TILOS Horizon 2020 program.
The European Union’s 2020 climate and energy package (known as “20–20–20” targets) requests, among other key objectives, 40% of the electricity production in Greece to be supplied from Renewable Energy Sources by 2020. The main barriers for reaching this target is the intermittency of renewable energy sources combined with the penetration limits in the local electrical grids and the high seasonal demand fluctuations. In this context, the introduction of energy storage systems, comprises one of the main solutions for coping with this situation. One of the most promising technologies for storing the excess energy, that would be otherwise lost, is the production and storage of hydrogen through water electrolysis. Hydrogen can be used for supporting the electricity grid during periods of high demand but also as transportation fuel for hydrogen-based automobiles (e.g. fuel cell vehicles). For this purpose, a simulation algorithm has been developed, able to assess the specifications of the optimum sizing of hydrogen production storage systems. For the application of the algorithm, the area of the Aegean Sea has been selected, owed to the considerable renewable energy sources curtailments recorded in the various non-interconnected islands in the region. More specifically, the developed algorithm is applied to an autonomous electricity network of 9 islands, located at the SE area of the Aegean Sea and known as the “Kos-Kalymnos” electricity system. The results obtained designate the optimum size of the hydrogen-based configuration, aiming to maximize the recovery of otherwise curtailed renewable energy production.
The European Union’s 2020 climate and energy package (known as “20-20-20” targets) requests, among other key objectives, 40% of the electricity production in Greece to be supplied from Renewable Energy Sources (RES) by 2020. The main barriers for reaching this target is the intermittency of RES combined with the penetration limits in the local electrical grids and the high seasonal demand fluctuations. In this context, the introduction of energy storage systems (ESSs), comprises one of the main solutions for coping with this situation. One of the most promising technologies for storing the excess energy, that would be otherwise lost, is the production and storage of hydrogen through water electrolysis. Hydrogen can be used for supporting the electricity grid during periods of high demand and as transportation fuel for H 2 -based automobiles (e.g. fuel cell vehicles). For this purpose, a simulation algorithm has been developed, able to assess the specifications of the optimum sizing of hydrogen production storage systems. For the application of the algorithm, the area of the Aegean Sea has been selected, owed to the considerable RES curtailments recorded in the various non-interconnected islands in the region. More specifically, the developed algorithm is applied to an autonomous electricity network of 9 islands, located at the SE area of the Aegean Sea and known as the “Kos-Kalymnos” electricity system. The results obtained designate the optimum size of the hydrogen-based configuration, aiming to maximize the recovery of otherwise curtailed RES production.
Autonomous photovoltaic systems have already been proved as one of the most reliable ways to handle the electrification requirements of remote consumers in isolated areas. The technology improvement in the field of building integrated photovoltaic systems, along with the governmental financial incentives for boosting the corresponding energy sector, have increased the interest of installing small scale photovoltaic systems not only in remote dwellings but also in grid-connected households. The penetration of photovoltaic systems in densely populated areas has made people even more familiar with them and therefore people with environmental consciousness are more likely to adopt the specific technology. In this context, the present work aims in highlighting the capabilities of building integrated photovoltaic systems along with battery storage devices in covering the electrical needs of a typical dwelling using real electricity demand and meteorological data based on Typical Meteorological Year time series. The system is simulated on an hourly basis by using an integrated numerical code that has been developed by the Soft Energy Applications & Environmental Protection Laboratory of the Mechanical Engineering Dept. of Piraeus University of Applied Sciences in Greece. The proposed solution guarantees zero load rejections under different solar potential schemes investigating also the possibilities of minimizing the storage system capacity.
The realization of Renewable Energy Sources (RES) for power generation as the only environmentally friendly solution, moved solar systems to the forefront of the energy market in the last decade. The capacity of the solar power doubles almost every two years in many European countries, including Greece. This rise has brought the need for reliable predictions of meteorological data that can easily be utilized for proper RES-site allocation. The absence of solar measurements has, therefore, raised the demand for deploying a suitable model in order to create a solar map. The generation of a solar map for Greece, could provide solid foundations on the prediction of the energy production of a solar power plant that is installed in the area, by providing an estimation of the solar energy acquired at each longitude and latitude of the map. In the present work, the well-known Meteorological Radiation Model (MRM), a broadband solar radiation model, is engaged. This model utilizes common meteorological data, such as air temperature, relative humidity, barometric pressure and sunshine duration, in order to calculate solar radiation through MRM for areas where such data are not available. Hourly values of the above meteorological parameters are acquired from 39 meteorological stations, evenly dispersed around Greece; hourly values of solar radiation are calculated from MRM. Then, by using an integrated spatial interpolation method, a Greek solar energy map is generated, providing annual solar energy values all over Greece.
Human thermal comfort sensation is defined as the conditions in which human expresses satisfaction with the thermal environment, absence of thermal discomfort, or conditions in which a great percentage of the population (more than 80%) do not express dissatisfaction. The assessment of these conditions can be accomplished by the application of a large number of theoretical and empirical indices estimated using meteorological parameters such as air temperature, wind speed, air humidity and solar radiation. The aim of this work is to investigate the human sensation of heat stress in 30 different sites across the Greek territory, during the warm period of the year, for the period 1995-1999. For that purpose, one of the widely used thermal index, Heat Index (HI), which was adopted by the USA’s National Weather Service, is calculated. HI is an index that is also called "apparent temperature". This index is a measure of how hot someone feels when relative humidity is added to the actual air temperature. For the estimation of HI values, hourly values of air temperature and relative humidity were used. The aforementioned meteorological data have been recorded by the network of meteorological stations of the Hellenic National Meteorological Service. Results indicate a great variability of heat stress conditions, at the same time in different regions across Greece, within the warm period of the year. Furthermore, it seems that the height above sea level, geographical coordinates and the distance from the sea plays an important role in the establishment of asychronous heat stress conditions. In general terms, during the warm period of the year neutral human thermal conditions along the Greek territory are prevailing. These conditions, allow people to have a com- fort thermal sensation as well as outdoor activities (agricultural activities, livestock, tourism etc).
Although efficiency of photovoltaic (PV) modules is usually specified under standard test conditions (STC), their operation under real field conditions is of great importance for obtaining accurate prediction of their efficiency and power output. The PV conversion process, on top of the instantaneous solar radiation, depends also on the modules’ temperature. Module temperature is in turn influenced by climate conditions as well as by the technical characteristics of the PV panels. Taking into consideration the extended theoretical background in the field so far, the current study is focused on the investigation of the temperature variation effect on the operation of commercial PV applications based on in-situ measurements at varying weather conditions. Particularly, one year outdoor data for two existing commercial (m-Si) PV systems operated in South Greece, i.e. an unventilated building-integrated (81 kWp) one and an open rack mounted (150 kWp) one, were collected and evaluated. The examined PV systems were equipped with back surface temperature sensors in order to determine module and ambient temperatures, while real wind speed measurements were also obtained for assessing the dominant effect of local wind speed on the PVs’ thermal loss mechanisms. According to the results obtained, the efficiency (or power) temperature coefficient has been found negative, taking absolute values between 0.30%/ oC and 0.45%/ oC, with the lower values corresponding to the ventilated free- standing frames.
Increased interest is recently demonstrated in the promotion of distributed generation based on renewable energy sources (RES). Contrariwise, owed to RES intermittency, most remote areas rely on oil-fired power generation. To facilitate further penetration of RES, the concept of demand side management (DSM) has lately emerged. To this end, a new DSM algorithm is currently developed. Peak shaving and load shifting are applied, considering implementation levels that the residential sector may comply with. Finally, a small-medium scale island grid is used as case study, with our results indicating that the appropriate level of DSM application may yield considerable benefits.
To confront problems concerning large-scale integration of renewable energy sources, introduction of energy storage constantly gains ground. Benefits stemming from the adoption of energy storage include exploitation of otherwise rejected energy, increased reliability of energy supply and improved operation of a given power system overall. In this regard, contribution of such systems in achieving large-scale integration of wind energy into island grids is currently considered. More precisely, fuel cells and hydrogen storage (FC–HS) are investigated, in comparison with conventional batteries. For this purpose, a simulation algorithm is developed to study the energy performance of different FC–HS configurations used to recover wind energy curtailments. The developed algorithm is then applied to a representative Aegean island of medium–high quality wind potential. Results obtained indicate that FC–HS may become attractive in comparison with conventional batteries, only in the case that the use of hydrogen surplus to cover other energy flows is also put forward.
Across the entire Greek territory one may encounter several remote consumers that could cover their needs on the basis of PV-based stand-alone applications exploiting the high quality local solar potential. In this context, optimum sizing of such installations also involves investigation of the optimum panels’ tilt angle, which opposite to grid-connected applications is required to provide year-round energy autonomy rather than maximization of the annual energy yield. Considering the above, investigation of the optimum panels’ tilt angle for stand-alone applications is the aim of the specific study, in both theoretical and experimental terms. Theoretical investigation is based on the validation of the assumption that the optimum angle for such applications coincides with the angle that provides maximum exploitation of solar potential during winter months, while following, the optimum angle determined in the area of 60o is also experimentally validated with the conduction of long-term winter measurements for the area of Athens.
On the numerous small and medium-sized Greek islands one may encounter several thousands of remote consumers unable to appreciate a direct electricity utility supply. For this purpose, remote consumers usually cover their electricity needs based on the operation of small diesel-generator sets. On the other hand, most of these areas appreciate high quality solar potential that comprises a stimulus for the use of stand-alone photovoltaic (PV)-based configurations. In this context, the primary objective of the present study is to determine the optimum dimensions of a stand-alone PV-diesel system, under the restriction of minimum long-term electricity generation cost, and accordingly obtain a comparison with diesel-only systems. For this purpose, the developed methodology is applied to a representative Greek island, with results obtained being rather encouraging for the implementation of the proposed solution.
Renewable energy sources (RES) based stand-alone systems employing either wind or solar power and energy storage comprise a reliable energy alternative, on top of conventional diesel-electric generator sets, commonly used by remote consumers. However, such systems usually imply the need for oversizing and considerable energy storage requirements leading to relatively high costs. On the other hand, hybrid configurations that may exploit both wind and solar potential of a given area may considerably reduce energy storage capacity and improve the economic performance of the system. In this context, an integrated techno-economic methodology for the evaluation of hybrid wind– photovoltaic stand-alone power systems is currently developed, aiming at the designation of optimum configurations for a typical remote consumer, using economic performance criteria. For the problem investigation, the developed evaluation model is applied to four representative areas of the Greek territory with different wind potential characteristics in order to obtain optimum configurations on the basis of minimum initial investment, 10-year and 20-year total cost. According to the results obtained, the proposed solution is favorably compared with all other stand-alone energy alternatives, reflecting the ability of hybrid systems to adjust even in areas where the local RES potential is not necessarily of high quality.
Renewable energy sources (RES) based stand-alone systems employing either wind or solar power and energy storage comprise a reliable energy alternative, on top of conventional diesel-electric generator sets, commonly used by remote consumers. However, such systems usually imply the need for oversizing and considerable energy storage requirements leading to relatively high costs. On the other hand, hybrid configurations that may exploit both wind and solar potential of a given area may considerably reduce energy storage capacity and improve the economic performance of the system. In this context, an integrated techno-economic methodology for the evaluation of hybrid wind– photovoltaic stand-alone power systems is currently developed, aiming at the designation of optimum configurations for a typical remote consumer, using economic performance criteria. For the problem investigation, the developed evaluation model is applied to four representative areas of the Greek territory with different wind potential characteristics in order to obtain optimum configurations on the basis of minimum initial investment, 10-year and 20-year total cost. According to the results obtained, the proposed solution is favorably compared with all other stand-alone energy alternatives, reflecting the ability of hybrid systems to adjust even in areas where the local RES potential is not necessarily of high quality.