Hydropower development priority using MCDM method

Hydropower is recognized as a renewable and clean energy sources and its potential should be realized in an environmentally sustainable and socially equitable manner. Traditionally, the decision criteria when analyzing hydropower projects, have been mostly a technical and economical analysis which focused on the production of electricity. However, environmental awareness and sensitivity to locally affected people should also be considered. Multi-criteria decision analysis has been applied to study the potential to develop hydropower projects with electric power greater than 100 kW in the Ping River Basin, Thailand, and to determine the advantages and disadvantages of the projects in five main criteria: electricity generation, engineering and economics, socio-economics, environment, and stakeholder involvement. There are 64 potential sites in the study area. Criteria weights have been discussed and assigned by expert groups for each main criteria and subcriteria. As a consequence of weight assignment, the environmental aspect is the most important aspect in the view of the experts. Two scenarios using expert weight and fair weight have been studied to determine the priority for development of each project. This study has been done to assist policy making for hydropower development in the Ping River Basin.     

Short-term predictability of photovoltaic production over Italy

Photovoltaic (PV) power production increased drastically in Europe throughout the last years. Since about the 6% of electricity in Italy comes from PV, an accurate and reliable forecasting of production would be needed for an efficient management of the power grid. We investigate the possibility to forecast daily PV electricity production up to ten days without using on-site measurements of meteorological variables. Our study uses a PV production dataset of 65 Italian sites and it is divided in two parts: first, an assessment of the predictability of meteorological variables using weather forecasts; second, an analysis of predicting solar power production through data-driven modelling. We calibrate Support Vector Machine (SVM) models using available observations and then we apply the same models on the weather forecasts variables to predict daily PV power production. As expected, cloud cover variability strongly affects solar power production, we observe that while during summer the forecast error is under the 10% (slightly lower in south Italy), during winter it is abundantly above the 20%.     

Desalination of underground brackish waters using an electrodialysis system powered directly by photovoltaic energy

The aims of this paper are: to demonstrate the feasibility of the desalination of brackish water from aquifers (total dissolved solids=2300-5100 g m⁻³) by means of an electrodialysis system powered directly by photovoltaic solar panels, and improve the mathematical model developed in a previous work in order to apply it to real brackish waters. The application of this model allows to predict the behaviour of the electrodialysis-photovoltaic system under different operational and meteorological conditions, and the time required to reach a given final concentration. Finally, the cost of electrodialysis-photovoltaic systems for small applications in isolated locations with lack of electric grid has been estimated.     

A novel optimization method for designing stand alone photovoltaic system

This paper presents a novel optimization method for sizing and design of stand alone photovoltaic systems. Loss of power supply probability analysis is set as a benchmark to determine all possible PV array and battery capacity. Then, the optimum design is proposed based on the lowest levelized cost of energy. The case study, with reference to Malaysia's meteorological data and typical load profile of rural area, has been simulated and compared to selected three past researches.     

Searching for public benefits in solar subsidies: A case study on the Australian government’s residential photovoltaic rebate program

The Australian Government ran a renewable energy program in the 2000s that provided rebates to householders who acquired solar Photovoltaic (PV) energy systems. Originally called the Photovoltaic Rebate Program (PVRP), it was rebranded the Solar Homes and Communities Plan (SHCP) in November 2007. This paper evaluates both the PVRP and SHCP using measures of cost-effectiveness and fairness. It finds that the program was a major driver of a more than six-fold increase in PV generation capacity in the 2000s, albeit off a low base. In 2010, solar PV’s share of the Australian electricity market was still only 0.1%. The program was also environmentally ineffective and costly, reducing emissions by 0.09 MtCO₂-e/yr over the life of the rebated PV systems at an average cost of between AU$238 and AU$282/tCO₂-e. In addition, the data suggest there were equity issues associated with the program, with 66% of all successful applicants residing in postal areas that were rated as medium–high or high on a Socio-economic Status (SES) scale.     

Scalable methodology for the photovoltaic solar energy potential assessment based on available roof surface area: Application to Piedmont Region (Italy)

During the last few years the photovoltaic energy market has seen an outstanding growth. According to the new directive on renewable energies of the European Commission (2009/28/EC), the European Union should reach a 20% share of the total energy consumption from renewable sources by 2020. The national overall targets impose for Italy a 17% renewable share: in case of failure the gap would be filled by importation of renewable energy from non-UE countries. The ambitious national targets and thus the continuously increasing interest on renewable fuels, require simple but reliable methods for the energy potential assessment over large-scale territories. Considering roof-top integrated PV systems, the assessment of the PV energy potential passes through the evaluation of the roof surface area available for installations. In the present paper a methodology for estimating the PV solar energy potential is presented, together with its application to Piedmont Region (North-Western Italy). The roof area suitable for solar applications, is calculated through the analysis of available GIS data. The solar radiation maps are taken from the database of the Joint Research Centre of the European Commission. Different solar energy exploitation scenarios are proposed with the relative perspective results and confidence interval. Further developments and applications of the presented methodology are finally discussed.     

Ex-post economic analysis of photovoltaic power in the Spanish grid: Alternative scenarios

Nowadays, photovoltaic technology as a whole is considered to cause deficit to the Spanish power system, because the bonuses that it receives are higher than the savings generated over the electricity prices thanks to the merit-order-effect. However, the bonuses to generation for new facilities have undergone significant declines over the past five years, along with the drop in the prices of modules. That means that the economic influence of photovoltaic power is highly penalized by the existing feed-in-tariff scheme presented in the years 2007 and 2008, which gave way to the Spanish photovoltaic boom. Based on these facts, the economic profitability to the system of the latest installed photovoltaic plants is analyzed; reaching the conclusion that the facilities registered in and after the second quarter of 2011 have been profitable to the system in the fourth quarter of 2012, and are very close to being profitable for the whole year. Finally, based on the aforementioned conclusions, alternative scenarios for the deployment of photovoltaic power in the Spanish grid are presented, based on a temporary redistribution of the facilities that fostered the boom, to provide a better understanding of the situation. This knowledge may be a valuable tool for less developed countries in terms of photovoltaic energy.     

Electrocoagulation of a synthetic textile effluent powered by photovoltaic energy without batteries: Direct connection behaviour

The feasibility of the use of an electrocoagulation system (EC) directly powered by a photovoltaic (PV) array has been demonstrated. The model pollutant used was a reactive textile dye Remazol Red RB 133. It has been proved that PV array configuration is a factor of great influence on the use of the generated power. The optimum PV array configuration must be reshaped depending on the instantaneous solar irradiation. A useful and effective methodology to adjust the EC–PV system operation conditions depending on solar irradiation has been proposed. The current flow ratio, J_v, is established as the control parameter.     

Numerical method for the extraction of photovoltaic module double-diode model parameters through cluster analysis

A numerical procedure for the extraction of the double-diode model parameters of photovoltaic (PV) modules is described. A particle swarm optimization algorithm is used to fit the calculated current–voltage characteristic of a PV module to the experimental one. As no recurrent solution was found in the large number of simulations carried out, mainly because of the stochastic nature of the optimization algorithm, statistics in combination with cluster analysis was employed to give an insight into the PV module parameters. This approach allows one to obtain a set of parameters which is reasonable and representative of the physical system.     

Procedure for optimal design of hydrogen production plants with reserve storage and a stand-alone photovoltaic power system

A procedure for sizing an electrolytic hydrogen production plant powered by a stand-alone photovoltaic system is described in this study. Our fundamental proposal is to compensate the loss of load probability of the photovoltaic system, by means of a hydrogen complementary storage. We compute the necessary hydrogen volume of that reserve storage. Using the isoreliability map of curves that characterizes a given location, we determine the size of the photovoltaic system that would be needed to generate a predetermined flow of hydrogen. Finally, we share information on our own experience relating to the design of the experimental installation at Villafría, located in the city of Burgos, Spain.     

Estimating photovoltaic energy potential from a minimal set of randomly sampled data

The remarkable rise of photovoltaics in the world over the past years testifies of the great improvement in the use of solar energy. Opportunities for further new PV installations are being sought, especially power plants in areas with as yet little exploited solar energy potential. In this paper, we describe a methodology for generating estimation models of PV electricity for installations in large regions where only a few scattered data or measurement stations are available. For validation only, application of this methodology was performed considering Italy, where estimations can be benchmarked using the Photovoltaic Geographical Information System (PVGIS) by the Joint Research Centre of the European Commission. The results show that the mean absolute errors were usually lower than 4%, compared to the PVGIS data, for about 90% of the estimates of PV electricity, and about 6% for the greatest mean error.     

Scalable methodology for the photovoltaic solar energy potential assessment based on available roof surface area: Further improvements by ortho-image analysis and application to Turin (Italy)

The ongoing rush of the UE member states to the 2020 overall targets on the national renewable energy share (see Directive 2009/28/EC), is propelling the large exploitation of the solar resource for the electricity production. However, the incentives to the large employment of PV solar modules and the relative perspective profits, are often cause of massive ground-mounted installations. These kind of installations are obviously the preferred solution by the investors for their high economic yields, but their social impact should be also considered. Over the Piedmont Region for instance, the large proliferation of PV farms is jeopardising wide agricultural terrains and turistic areas, therefore the policy of the actual administration is to encourage the use of integrated systems in place of massive installations. For these reasons, an effort to demonstrate that the distributed residential generation can play a primary role in the market is mandatory. In our previous work “Scalable methodology for the photovoltaic solar energy potential assessment based on available roof surface area: application to Piedmont Region (Italy)”, we already proposed a basic methodology for the evaluation of the roof-top PV system potential. However, despite the total roof surface has been computed on a given cartographical dataset, the real roof surface available for PV installations has been evaluated through the assumption of representative roofing typologies and empirical coefficients found via visual inspection of satellite images. In order to overcome this arbitrariness and refine our methodology, in the present paper we present a brand new algorithm to compute the available roof surface, based on the systematical analysis and processing of aerial georeferenced images (ortho-images). The algorithm, fully developed in MATLAB®, accounts for shadow, roof surface available (bright and not), roof features (i.e. chimneys or walls) and azimuthal angle of the eventual installation. Here we apply the algorithm to the whole city of Turin, and process more than 60,000 buildings. The results achieved are finally compared with our previous work and the updated PV potential assessment is consequently discussed.     

A comparative investigation of various greenhouse heating options using exergy analysis method

This study deals with modeling and analyzing the performance of greenhouses from the power plant through the heating system to the greenhouse envelope using exergy analysis method, the so-called low exergy or LowEx approach, which has been and still being successfully used in sustainable buildings design, for the first time to the best of the author’s knowledge. For the heating applications, three options are studied with (i) a solar assisted vertical ground-source heat pump greenhouse heating system, (ii) a wood biomass boiler, and (iii) a natural gas boiler, which are driven by renewable and non-renewable energy sources. In this regard, two various greenhouses, the so-called small greenhouse and large greenhouse, considered have heat load rates of 4.15 kW and 7.5 MW with net floor areas of 11.5 m² and 7.5 ha, respectively. The overall exergy efficiency values for Cases 1–3 (solar assisted vertical ground-source heat pump, natural gas boiler and wood biomass boiler) of the small greenhouse system decrease from 3.33% to 0.83%, 11.5% to 2.90% and 3.15% to 0.79% at varying reference state temperatures of 0 to 15 °C while those for Cases 1 and 2 (wood biomass and natural gas boilers) of the large greenhouse system decrease from 2.74% to 0.11% and 4.75% to 0.18% at varying reference state temperatures of −10% to 15 °C. The energetic renewability ratio values for Cases 1 and 3 of the small greenhouse as well as Case 1 of the large greenhouse are obtained to be 0.28, 0.69 and 0.39, while the corresponding exergetic renewability ratio values are found to be 0.02, 0.64 and 0.29, respectively.     

A comparative study of the thermal and radiative impacts of photovoltaic canopies on pavement surface temperatures

Rapid urbanization of the planet is occurring at an unprecedented pace, primarily in arid and semi-arid hot climates [Golden, J.S., 2004. The built environment induced urban heat island effect in rapidly urbanizing arid regions – a sustainable urban engineering complexity. Environ. Sci. J. Integr. Environ. Res. 1 (4), 321–349]. This growth has manifested itself as a cause of various impacts including elevated urban temperatures in comparison to rural sites known as the Urban Heat Island (UHI) effect [Oke, T.R., 1982. The energetic basis of the urban heat island. Q. J. R. Meteor. Soc. 108, 1–24]. Related are the increased demands for electric power as a result of population growth and increased need for mechanical cooling due to the UHI. In the United States, the Environmental Protection Agency has developed a three-prong approach of (1) cool pavements, (2) urban forestry and (3) cool roofs to mitigate the UHI. Researchers undertook an examination of micro scale benefits of the utilization of photovoltaic panels to reduce the thermal impacts to surface temperatures of pavements in comparison to urban forestry. The results of the research indicate that photovoltaic panels provide a greater thermal reduction benefit during the diurnal cycle in comparison to urban forestry while also providing the additional benefits of supporting peak energy demand, conserving water resources and utilizing a renewable energy source.     

Increasing the solar photovoltaic energy capture on sunny and cloudy days

This report analyzes an extensive set of measurements of the solar irradiance made using four identical solar arrays and associated solar sensors (collectively referred to as solar collectors) with different tilt angles relative to the earth’s surface, and thus the position of the sun, in order to determine an optimal tracking algorithm for capturing solar radiation. The study included a variety of ambient conditions including different seasons and both cloudy and cloud-free conditions. One set of solar collectors was always approximately pointed directly toward the sun (DTS) for a period around solar noon. These solar collectors thus captured the direct beam component of the solar radiation that predominates on sunny days. We found that on sunny days, solar collectors with a DTS configuration captured more solar energy in accordance with the well-known cosine dependence for the response of a flat-surfaced solar collector to the angle of incidence with direct beam radiation. In particular, a DTS orientation was found to capture up to twice as much solar energy as a horizontal (H) orientation in which the array is tilted toward the zenith. Another set of solar collectors always had an H orientation, and this best captured the diffuse component of the solar radiation that predominates on cloudy days. The dependence of the H/DTS ratio on the solar-collector tilt angle was in approximate agreement with the Isotropic Diffuse Model derived for heavily overcast conditions. During cloudy periods, we found that an H configuration increased the solar energy capture by nearly 40% compared to a DTS configuration during the same period, and we estimate the solar energy increase of an H configuration over a system that tracks the obscured solar disk could reach 50% over a whole heavily-overcast day. On an annual basis the increase is predicted to be much less, typically only about 1%, because the contribution of cloudy days to the total annual solar energy captured by a photovoltaic system is small. These results are consistent with the solar tracking algorithm optimized for cloudy conditions that we proposed in an earlier report and that was based on a much smaller data set. Improving the harvesting of solar energy on cloudy days deserves wider attention due to increasing efforts to utilize renewable solar energy. In particular, increasing the output of distributed solar power systems on cloudy days is important to developing solar-powered home fueling and charging systems for hydrogen-powered fuel-cell electric and battery-powered vehicles, respectively, because it reduces the system size and cost for solar power systems that are designed to have sufficient energy output on the worst (cloudy) days.     

Estimating potential photovoltaic yield with r.sun and the open source Geographical Resources Analysis Support System

The package r.sun within the open source Geographical Resources Analysis Support System (GRASS) can be used to compute insolation including temporal and spatial variation of albedo and solar photovoltaic yield. A complete algorithm is presented covering the steps of data acquisition and preprocessing to post-simulation whereby candidate lands for incoming solar farms projects are identified. The optimal resolution to acquire reliable solar energy outputs to be integrated into PV system design software was determined to be 1 square km. A case study using the algorithm developed here was performed on a North American region encompassing fourteen counties in South-eastern Ontario. It was confirmed for the case study that Ontario has a large potential for solar electricity. This region is found to possess over 935,000 acres appropriate for solar farm development, which could provide 90 GW of PV. This is nearly 60% of Ontario’s projected peak electricity demand in 2025. The algorithm developed and tested in this paper can be generalized to any region in the world in order to foster the most environmentally-responsible development of large-scale solar farms.     

Stand-alone operation of an alkaline water electrolyser fed by wind and photovoltaic systems

Over the last few years, hydrogen technologies have established themselves as key enablers in the medium and long-term development of a new energy model that offers greater sustainability and independence than the present-day one. In this respect, the integration of water electrolysis with renewable energy-based systems can play an important part in the large-scale production of sustainable hydrogen. This paper reports on the complete experimental characterisation of a 1 Nm³ h⁻¹ alkaline water electrolyser located in the Public University of Navarre (UPNa). Specifically, a study was made of the electrical performance, hydrogen production rate, purity of the gases generated and energy efficiency, for a range of operating currents (40–120 A), temperatures (35–65 °C) and pressures (5–25 bar). Additionally, an experimental study was conducted on the electrolyser operation under conditions that are characteristic of a stand-alone wind power and PV-based renewable energy system, installed at the UPNa. The results obtained for the wind power and PV emulations showed that the electrolyser performed correctly, with regard to balance of plant and its principal electrochemical characteristics. Furthermore, the mean energy efficiency of the electrolyser was 77.7% for the wind power emulation, and 78.6% for the PV emulation on a day with stable irradiance, and 78.1% on a day with highly variable irradiance (day with scattered clouds).     

Effects of nanofluids on the photovoltaic thermal system for hydrogen production via electrolysis process

In this study the photovoltaic hybrid thermal system has been fabricated for an effective increase in production of electric output. Further the PV/T system also designed to produce the hydrogen from the water through electrolysis process. Several studies reported drastic reduction in the electric output due to high cell temperatures. Nevertheless, these effects are reduced by introduction of the nanoparticles. This study also examines the nanofluids MWCNT and Fe₂O₃ as the passive cooling agent for higher electric output production without any major energy loss. The nanoparticles are dispersed in the water at the optimum fashions to increase the thermal and electrical efficiency of the system. Both MWCNT and Fe₂O₃ nanofluids were passed to the hybrid system at the flow rate of 0.0075 kg/s and 0.01 kg/s. The highest electrical output and thermal efficiency has been obtained at 12.30 P.M. With regard to the production of hydrogen, the maximum productions were observed from 12.15 P.M. to 13.00 P.M.. Implementation of this method compensates the energy loss with superior electrical output compared to previous conventional method. By compelling the results, 0.01 kg/s subjected to be efficient on the electricity production and the hydrogen generation. Further, employing the electrolyzer as the attached to the hybrid system produces the hydrogen, which can be stored for future use as the promising source of energy.     

Hydrogen production by methanol aqueous electrolysis using photovoltaic energy: Algerian potential

Hydrogen is considered as the most promising energy carrier for providing a clean, reliable and sustainable energy system. It can be produced from a diverse array of potential feed stocks including water, fossil fuels and organic matter. Electrolysis is the best option for producing hydrogen very quickly and conveniently. Water electrolysis as a source of hydrogen production has recently gained much attention since it can produce high purity hydrogen and can be compatible with renewable energies. Besides the water electrolysis, aqueous methanol electrolysis has been reported in several studies. The aqueous methanol electrolysis proceeds at much lower voltage than that with the water electrolysis. As a result of the substantially lower operating voltage, the energy efficiency for methanol electrolysis can be higher than that for water electrolysis. In this paper, we are interesting to methanol electrolysis in order to produce hydrogen. The relation linking hydrogen production rate to the power needed to electrolyse a unit volume of aqueous methanol solution has been determined. Using this relation, the potential of hydrogen from aqueous methanol solution using a PV solar as the energy system has been evaluated for different locations in Algeria.