A current and future state of art development of hybrid energy system using wind and PV-solar: A review

The wind and solar energy are omnipresent, freely available, and environmental friendly. The wind energy systems may not be technically viable at all sites because of low wind speeds and being more unpredictable than solar energy. The combined utilization of these renewable energy sources are therefore becoming increasingly attractive and are being widely used as alternative of oil-produced energy. Economic aspects of these renewable energy technologies are sufficiently promising to include them for rising power generation capability in developing countries. A renewable hybrid energy system consists of two or more energy sources, a power conditioning equipment, a controller and an optional energy storage system. These hybrid energy systems are becoming popular in remote area power generation applications due to advancements in renewable energy technologies and substantial rise in prices of petroleum products. Research and development efforts in solar, wind, and other renewable energy technologies are required to continue for, improving their performance, establishing techniques for accurately predicting their output and reliably integrating them with other conventional generating sources. The aim of this paper is to review the current state of the design, operation and control requirement of the stand-alone PV solar–wind hybrid energy systems with conventional backup source i.e. diesel or grid. This Paper also highlights the future developments, which have the potential to increase the economic attractiveness of such systems and their acceptance by the user.     

Interfacing wind energy conversion equipment with utility systems

Technical interface issues between utility systems and solar technology devices are receiving increasing attention from government and industry. These issues arise from the intermittent power generation characteristics of solar systems, in contrast to most utility generation equipment. This paper explores the interface issues for wind energy systems, a solar technology likely to achieve early commercialization. Described are government- and industry-sponsored assessments of the impact of wind energy devices on industry operations, controls, and protective subsystems. The conclusions drawn indicate that: there does not appear to be any major technical interface problem in applying wind energy devices to utility power systems; current utility control and protection design methods are adequate for interfacing wind energy units with a utility system; and, the cost of control and protection for large (over 1 Mw) wind machines appears acceptable but may prove prohibitive for small machines. Several advanced technology options with the potential for reducing the costs for protection and control are also described, for both the wind machines and the utility system.     

Optimal design and techno-economic analysis of a hybrid solar–wind power generation system

Solar energy and wind energy are the two most viable renewable energy resources in the world. Good compensation characters are usually found between solar energy and wind energy. This paper recommend an optimal design model for designing hybrid solar–wind systems employing battery banks for calculating the system optimum configurations and ensuring that the annualized cost of the systems is minimized while satisfying the custom required loss of power supply probability (LPSP). The five decision variables included in the optimization process are the PV module number, PV module slope angle, wind turbine number, wind turbine installation height and battery capacity. The proposed method has been applied to design a hybrid system to supply power for a telecommunication relay station along south-east coast of China. The research and project monitoring results of the hybrid project were reported, good complementary characteristics between the solar and wind energy were found, and the hybrid system turned out to be able to perform very well as expected throughout the year with the battery over-discharge situations seldom occurred.     

Monitoring and control of a hydrogen production and storage system consisting of water electrolysis and metal hydrides

Renewable energy sources such as wind turbines and solar photovoltaic are energy sources that cannot generate continuous electric power. The seasonal storage of solar or wind energy in the form of hydrogen can provide the basis for a completely renewable energy system. In this way, water electrolysis is a convenient method for converting electrical energy into a chemical form. The power required for hydrogen generation can be supplied through a photovoltaic array. Hydrogen can be stored as metal hydrides and can be converted back into electricity using a fuel cell. The elements of these systems, i.e. the photovoltaic array, electrolyzer, fuel cell and hydrogen storage system in the form of metal hydrides, need a control and monitoring system for optimal operation. This work has been performed within a Research and Development contract on Hydrogen Production granted by Solar Iniciativas Tecnológicas, S.L. (SITEC), to the Politechnic University of Valencia and to the AIJU, and deals with the development of a system to control and monitor the operation parameters of an electrolyzer and a metal hydride storage system that allow to get a continuous production of hydrogen.     

Renewable energy resources as an alternative to modify the load curve in Northern Cyprus

The average annual increase in electricity consumption and peak demand in Northern Cyprus (N. Cyprus) during the past 20 years have been 7.1 and 5.5%, respectively. In recent years, the demand for electricity has been stretched to its limits in winter. This raised the question of whether renewable energy resources could be utilized to reduce the level of peak demand. Indeed, Cyprus being a Mediterranean island, enjoys an abundance of solar energy, and preliminary studies showed that a considerable potential of wind energy is also available. Utilization of renewable energy for space heating, water heating, pumping and power generation would increase electrical reserve margins, raise system load factor, improve load following capabilities, and reduce the need for capacity expansion. Currently, solar water heating which leads to a saving of at least 72 GWh energy per annum and a significant reduction in CO₂ emission has been extensively used in N. Cyprus. In N. Cyprus, despite the availability of renewable energy resources constructing renewable base-load, electrical power stations has not been found feasible. However, constructing such systems is recommended for two reasons: firstly, as a supplement to saving fuel and secondly, expanding capacity. In this context, the economic analysis for both solar and wind energy systems, has shown a reasonable internal rate of return (IRR). Although, the IRR is higher for wind energy systems, the availability of wind is limited to a few locations and therefore energy distribution is required.     

Strategic trends for future energy policy: Evidence from China

In addition to taking advantage of clean technologies for energy from fossil fuels, China’s current policy is to focus on renewable energy especially hydropower and wind. However, this policy is not practical due to climatic problems for installing wind turbines and solar collectors in some Chinese provinces. In this study, China’s regional policy is examined in terms of renewable energy sources and solutions are provided. Based on the data available in the literature, it was found that the hydropower systems account for a significant share of energy required in China, except for Henan. Inner Mongolia was also introduced as the most important Chinese province for developing wind energy systems because over 30% of wind power capacity of China belongs to this province.     

Impact of hydrogen energy storage on California electric power system: Towards 100% renewable electricity

Decarbonization of the power sector is a key step towards greenhouse gas emissions reduction. Due to the intermittent nature of major renewable sources like wind and solar, storage technologies will be critical in the future power grid to accommodate fluctuating generation. The storage systems will need to decouple supply and demand by shifting electrical energy on many different time scales (hourly, daily, and seasonally). Power-to-Gas can contribute on all of these time scales by producing hydrogen via electrolysis during times of excess electrical generation, and generating power with high-efficiency systems like fuel cells when wind and solar are not sufficiently available. Despite lower immediate round-trip efficiency compared to most battery storage systems, the combination of devices used in Power-to-Gas allows independent scaling of power and energy capacities to enable massive and long duration storage. This study develops and applies a model to simulate the power system balance at very high penetration of renewables. Novelty of the study is the assessment of hydrogen as the primary storage means for balancing energy supply and demand on a large scale: the California power system is analyzed to estimate the needs for electrolyzer and fuel cell systems in 100% renewable scenarios driven by large additions of wind and solar capacities. Results show that the transition requires a massive increase in both generation and storage installations, e.g., a combination of 94 GW of solar PV, 40 GW of wind, and 77 GW of electrolysis systems. A mix of generation technologies appears to reduce the total required capacities with respect to wind-dominated or solar-dominated cases. Hydrogen storage capacity needs are also evaluated and possible alternatives are discussed, including a comparison with battery storage systems.     

Transient simulation and comparative assessment of a hydrogen production and storage system with solar and wind energy using TRNSYS

This paper uses the TRNSYS software to investigate the hourly energy generation potential, storage, and consumption via an electrolyzer and a fuel cell in the Canadian city of Saskatoon, which is a region with high solar and wind energy potential. For this purpose, a location with an area of 10,000 m² was considered, in which the use of solar panels and vertical-axis wind turbines (VAWTs) were simulated. In the simulation, the solar panels were placed at specific distances, and the energy generation capacity, amount of produced hydrogen, and the energy available from the fuel cell were examined hourly and compared to the case with wind turbines placed at standard distances. The results indicated energy generation capacities of 1,966,084 kWh and 75,900 kWh for the solar panels and the wind turbines, respectively, showing the high potential of solar panels compared to wind turbines. Moreover, the fuel cells in the solar and wind systems can produce 733,077 kWh and 22,629 kWh of energy per year, respectively, if they store all of the received energy in the form of hydrogen. Finally, the hourly rates of hydrogen production by the solar and wind systems were reported.     

Numerical estimation model of energy conversion for small hybrid solar–wind system

This article presents a numerical model which can estimate the energy conversions of separate and hybrid solar–wind systems under variable weather. The model integrates the equations associated with the characteristics of photovoltaic generation, wind energy conversion, energy balance, and battery bank, and uses the local database for radiation, wind speed, and ambient temperature. Once the equation associated with the characteristics of load is given, the numerical model can estimate the monthly and yearly powers output of the separate and hybrid solar–wind systems provided with different configurations. As a fundamental research, the presentations of daily profiles of solar radiation, wind energy, and ambient temperature are explained in detail, and the combination of the characteristics of wind energy conversion and battery bank is determined. The condition of hybrid action is shown, and the solutions are certain to be found. The operation strategies of separate and hybrid systems are also presented.     

Test Procedures for Heat Storages for Solar Heating Systems

The Danish Government supports producers of systems for renewable energy sources (solar, wind, biomass). At present the consumer will receive 30% of the investments in the installed solar heating system. In order to participate in this arrangement it is required of the producers that the components of their solar heating systems are tested. The heat storages are tested at the Thermal Insulation Laboratory at the Technical University of Denmark. Tests of marketed heat storages for solar heating systems for domestic hot water supply started in 1979, and since then the test procedures have been changed continuously according to the experience gained. The test procedure in use now and some of the experiences gained will be described in the following.     

System-level power-to-gas energy storage for high penetrations of variable renewables

According to outlooks by the IEA and the U.S. EIA, renewables will become the largest source of electricity by 2050 if global temperature rise is to be limited to 2 °C. However, at penetrations greater than 30%, curtailment of wind and solar can be significant in even the most flexible systems. Energy storage can reduce curtailment and increase utilisation of variable renewables. Power-to-gas is a form of long-term storage based on electrolytic production of hydrogen. This research models the co-sizing of wind and solar PV capacity and electrolyser capacity in a jurisdiction targeting 80% penetration of variable renewable electricity. Results indicate that power-to-gas can reduce required wind and solar capacity by as much as 23% and curtailment by as much as 87%. While the majority of charging events last less than 12 h, the majority of the total annual stored energy comes from longer-term events. Additional scenarios reveal that geographic diversity of wind farms reduces capacity requirements, but the same benefit is not found for distributing solar PV.     

Solar forecasting methods for renewable energy integration

The higher penetration of renewable resources in the energy portfolios of several communities accentuates the need for accurate forecasting of variable resources (solar, wind, tidal) at several different temporal scales in order to achieve power grid balance. Solar generation technologies have experienced strong energy market growth in the past few years, with corresponding increase in local grid penetration rates. As is the case with wind, the solar resource at the ground level is highly variable mostly due to cloud cover variability, atmospheric aerosol levels, and indirectly and to a lesser extent, participating gases in the atmosphere. The inherent variability of solar generation at higher grid penetration levels poses problems associated with the cost of reserves, dispatchable and ancillary generation, and grid reliability in general. As a result, high accuracy forecast systems are required for multiple time horizons that are associated with regulation, dispatching, scheduling and unit commitment. Here we review the theory behind these forecasting methodologies, and a number of successful applications of solar forecasting methods for both the solar resource and the power output of solar plants at the utility scale level.     

Alternatives to grid extension for rural electrification: Decentralized renewable energy technologies in Vietnam

This paper examines the economic viability of stand-alone, household-sized renewable energy technologies, namely wind generator and solar PV for application in remote and rural areas of Vietnam. Three reference technologies are chosen. These are two solar PV systems of 130 and 100 Wp for solar conditions in the North and the South, respectively, and one 150 W wind turbine. It is found for all regions that levelized costs of PV energy are lower than the cost of energy from gasoline gen-set, and are cost-competitive with grid extension, especially for areas with low load density and low number of households to be electrified. Regarding wind energy, the viability is dependent on the location due to the wide variation of wind resource to topography. However, in locations with proper resources, wind energy is even more cost-competitive than solar PV. Thus, the use of either wind generator or solar PV is economically feasible in rural villages and remote areas of Vietnam. Policy recommendations for promoting the market development of renewable energy technologies are discussed in the final section of the paper.     

Prospects of renewable energy - a feasibility study in the Australian context

Given the recent increasing public focus on climate change issues, there is a need for robust, sustainable and climate friendly power transmission and distribution systems that are intelligent, reliable, and green. Current power systems create environmental impacts as well as contributing to global warming due to their utilization of fossil fuels, especially coal, as carbon dioxide is emitted into the atmosphere. In contrast to fossil fuels, renewable energy is starting to be used as the panacea for solving climate change or global warming problems. This paper describes a feasibility study undertaken to investigate the potentialities of renewable energy including the prospective locations in Australia for renewable energy generation, in particular solar and wind energy. Initially, a hybrid model has been developed to investigate the prospects of wind energy for typical Australian region considering production cost, cost of energy, emission production and contribution from renewable energy using the Hybrid Optimization Model for Electric Renewable (HOMER), a computer model developed by the USA’s National Renewable Energy Laboratory (NREL). This model also explores suitable places around Australia for wind energy generation using statistical analysis. Subsequently, the usefulness of solar energy in the Australian context and suitable locations for solar energy generation are also investigated using a similar hybrid model. Finally, the model has been developed to investigate the prospects of renewable energy in particular wind and solar energy including specific locations in Australia that would be suitable for both wind and solar energy generation. From simulation analysis it is clearly observed that Australia has enormous potentialities for substantially increased use of renewable energy; a large penetration of renewable energy sources into the national power system would reduce CO₂ emissions significantly, contributing to the reduction of global warming.     

太阳能烟囱与垂直轴风机耦合发电可行性分析

通过分析太阳能烟囱热气流发电和垂直轴风力机发电的技术及特点,提出了太阳能热气流烟囱与垂直轴风力机耦合发电的方法。对风力机—太阳能热气流烟囱互补发电系统的可行性进行了分析。互补发电的功率输出持续、稳定,具有大规模并网的良好条件,是实现太阳能与风能综合利用的有效途径。     

Methodology to estimate the output of a dual solar–wind renewable energy system in Japan

The potentially damaging effects of climate change make it imperative to develop zero-carbon energy systems and societies based on renewable energy sources that do not negatively affect the environment. However, these systems are often criticized for their intermittency, and the present paper proposes a method to analyze the true minimum capacity factor that can be expected from such a system based on a historical hourly estimation of the electricity produced by a given solar–wind generating mix. A simulation was carried out to show how much energy could be produced for a sample future group of scenarios encompassing a variety of solar and wind mixes, and the results show that, with a 1:2 mix of solar to wind energy, the system will always operate at least at 10% capacity from 10:00 to 16:00, as calculated using the meteorological conditions of the year 2001. This study also analyzes the land requirements necessary to implement such a solar–wind energy system, highlighting the vast areas that would be necessary to be covered with wind turbines and solar panels if such a system were to supply the majority of the electricity demand in Japan.     

Integration of wind turbine with heliostat based CSP/CPVT system for hydrogen production and polygeneration: A thermodynamic comparison

In this study, two wind-solar-based polygeneration systems namely CES-1 and CES-2 are developed, modeled, and analyzed thermodynamically. CES-1 hybridizes a heliostat based CSP system with wind turbines while CES-2 integrates heliostat-based CPVT with wind turbines. This study aims to compare the production and thermodynamics performance of two heliostat based concentrated solar power technologies when hybridized with wind turbines. The systems have been modeled to produce, freshwater, hot water, electricity, hydrogen, and cooling with different cycles/subsystems. While the overall objective of the study is to model two polygeneration systems with improved energy and exergy performances, the performances of two solar technologies are compared. The wind turbine system integrated with the comprehensive energy systems will produce 1.14 MW of electricity and it has 72.2% energy and exergy efficiency. Also, based on the same solar energy input, the performance of the heliostat integrated CPVT system (CES-2) is found to be better than that of the CSP based system (CES-1). The polygeneration thermal and exergy efficiencies for the two systems respectively are 48.08% and 31.67% for CES-1; 59.7% and 43.91% for CES-2. Also, the electric power produced by CES-2 is 280 kW higher in comparison to CES-1.     

The development of urban renewable energy at the existential technology research center (ETRC) in Toronto, Canada

This paper presents new forms of urban renewable energy, in particular, the integration of solar and wind power into the industrial and commercial buildings with flat roofs which populate a city's downtown core. This combination of renewable energy passively adapts to pre-existing structures and exploits them to their full advantage. The working prototypes presented aim to introduce an element of multi-functionality to building-integrated photovoltaics (BIPV), creating systems which produce energy while meeting required needs and desirable features of urban buildings. We also explore the combination of wind energy and various energy efficiency initiatives with BIPV designs. Our energy efficiency initiatives include a new method of generating the perception of natural sunlight from artificial light and brainwave controlled lighting that dims automatically when occupants’ concentration is lowered. These efforts result in an environment that celebrates the existential notion of self-empowerment through reducing energy consumption and having control over one's own energy production. Our discussion follows into market considerations of our BIPV designs and how project costs are lowered and space is conserved, assets when designing for urban locations. The test site for the development of urban renewable energy is the Existential Technology Research Center (ETRC), located in downtown Toronto, Canada.     

Wind power systems for zero net energy housing in the United States

This work investigates the feasibility of renewable energy housing development in the U.S. using wind power and solar thermal systems to attain zero net energy consumption. The over all objective was to determine how the wind power and solar thermal system designs and economics differ with various climates, wind and solar resources, energy prices, and state incentives, such as net-metering. Five U.S. cities, one in each of the five climate zones, were selected for this study based on their potential for wind power. A zero net energy housing design tool was developed in order to analyze and compare various system designs. The energy performance and economics of the designs were compared for various sizes of housing development, for seven turbine models, and selected heating systems. The results suggest that while there are some economical options for wind powered zero net energy housing developments, they are generally more expensive (except in the warmest climate zone) than housing with natural gas heating. In all of the cases, the economies of scale for large-scale wind turbines gave more of an economic advantage than net-metering programs gave small- and medium-scale wind turbines.     

Domestic integration of micro-renewable electricity generation in Ireland – The current status and economic reality

The utilisation of renewable energy resources for power generation is extremely important for Ireland due to the lack of indigenous fossil fuel resources. A micro-wind turbine is by far the most commonly used grid-connected micro-renewable electricity generation system for domestic applications in Ireland, followed by solar PV. Unfortunately, neither a single micro-wind turbine nor a single solar PV system can provide a continuous power supply due to variations in weather and climate conditions. The coupling of these two systems however can improve the power supply reliability by using the complementary characteristics of wind and solar energy. In this paper, a micro-renewable electricity-generation-system integration technique, tailored for applications in Ireland but generally applicable, is presented. Net present value is the parameter used to identify the optimal system. The optimal system can be a mono system, formed from a single micro-wind turbine or a single solar PV system, or a hybrid system formed from a combination of both. A renewable energy requirement is a constraint used in the integration to eliminate systems that cannot provide sufficient energy from renewable energy resources. The integration technique is applied to find the optimal system, under current Irish conditions, that can be formed from six sample micro-wind turbines and/or solar PV systems assembled from three sample solar PV modules. The analyses show that, with a 50% renewable energy requirement, the optimal system is a mono system containing a 2.4 kW micro-wind turbine; however, critically, the system is not economically viable. Four parameter studies assessing the effect of household electrical load, imported electricity price, exported electricity tariff and wind speed have also been conducted. From these studies it is seen that the most effective way to improve the financial performance of all systems is to offer a higher exported electricity tariff; installing a mono/hybrid system containing a micro-wind turbine in a location with a good wind resource can also have a significant effect.