GRID-CONNECTED PV SYSTEMS -THE ROLE OF THE UTILITY SECTOR

The development of photovoltaic solar energy (PV) has accelerated in the past decade. On the one hand, the improvements in solar cell types are very promising, while, on the other hand, the market for autonomous (off-grid) applications has grown substantially.

The development of grid-connected PV systems especially in the built-up environment is just starting up, both worldwide and in Europe. The energy losses currently present at system level will be reduced in the following years by implementing and assimilating practical experiments and demonstration projects.

Developments in Europe and some other countries will be described briefly. The interest in PV system developments is increasing and focussing more and more on the electricity utility sector.

It is clear that the utility sector will play an important role in the upscaling of the market for PV in energy supply. It is necessary, therefore, that the utility sector develops a long-term view, with a horizon of at least 25 years, on the role of PV in the energy supply.     

Advancement in solar photovoltaic/thermal (PV/T) hybrid collector technology

This article presents an overview on the research and development and application aspects for the hybrid photovoltaic/thermal (PV/T) collector systems. A major research and development work on the photovoltaic/thermal (PVT) hybrid technology has been done since last 30 years. Different types of solar thermal collector and new materials for PV cells have been developed for efficient solar energy utilization. The solar energy conversion into electricity and heat with a single device (called hybrid photovoltaic thermal (PV/T) collector) is a good advancement for future energy demand. This review presents the trend of research and development of technological advancement in photovoltaic thermal (PV/T) solar collectors and its useful applications like as solar heating, water desalination, solar greenhouse, solar still, photovoltaic-thermal solar heat pump/air-conditioning system, building integrated photovoltaic/thermal (BIPVT) and solar power co-generation.     

On the value of decentralised PV systems for the GCC residential sector

Based on the rich natural potential of the Gulf region, solar energy is expected to play a greater role in the future of the Gulf Corporation Council (GCC) countries. This study examines whether the integration of the photovoltaic (PV) into individual residential buildings in the GCC countries is worth the investment. A prototype residential building is developed and a building integrated photovoltaic (BiPV) system is then designed. The system performance is simulated, and through economic analysis, it is shown that the current BiPV technology is not a cost-effective option for the GCC countries based on the present electricity tariff, PV system cost and system efficiency. The only way such a system would be viable with current technology is if the electricity tariff were to increase substantially. However, if the tariff remains constant for the foreseeable future, BiPV solar energy technology will only be feasible if the total system cost drops drastically. This study shows that BiPV systems offer cost reductions in both energy and economic terms over centralised PV plants, especially if the costs of avoided building construction materials are taken into account. To bring about the benefits of BiPV technology for the GCC residential sector, therefore, the first logical and most practical step is the implementation of a continuous promotion strategy that consists of both subsidies for investments and reasonable tariffs.     

Industrial application of PV/T solar energy systems

Hybrid photovoltaic/thermal (PV/T) systems consist of PV modules and heat extraction units mounted together. These systems can simultaneously provide electrical and thermal energy, thus achieving a higher energy conversion rate of the absorbed solar radiation than plain photovoltaics. Industries show high demand of energy for both heat and electricity and the hybrid PV/T systems could be used in order to meet this requirement. In this paper the application aspects in the industry of PV/T systems with water heat extraction is presented. The systems are analyzed with TRNSYS program for three locations Nicosia, Athens and Madison that are located at different latitudes. The system comprises 300 m² of hybrid PV/T collectors producing both electricity and thermal energy and a 10 m³ water storage tank. The work includes the study of an industrial process heat system operated at two load supply temperatures of 60 °C and 80 °C. The results show that the electrical production of the system, employing polycrystalline solar cells, is more than the amorphous ones but the solar thermal contribution is slightly lower. A non-hybrid PV system produces about 25% more electrical energy but the present system covers also, depending on the location, a large percentage of the thermal energy requirement of the industry considered. The economic viability of the systems is proven, as positive life cycle savings are obtained in the case of hybrid systems and the savings are increased for higher load temperature applications. Additionally, although amorphous silicon panels are much less efficient than the polycrystalline ones, better economic figures are obtained due to their lower initial cost, i.e., they have better cost/benefit ratio.     

Solar Technological Progress and Use of Solar Energy in the World

Solar energy can potentially play a very important role in providing most of the heating, cooling and electricity needs of the world The sun has produced energy for billions of years. Solar energy is the solar radiation that reaches the earth. There are a variety of different technologies used in order to take advantage of solar energy. The primary solar energy technologies include photovoltaics, concentrating solar power, and solar heating and cooling systems. Today solar sources provide around 10% of the energy used worldwide, but in the developing countries their share is still of the order of 40%. In 1999, installed photovoltaic (PV) capacity was 594 MWp in the world. Japan has the highest PV capacity as a result of an important program to support the development of PV markets. Japan had a PV capacity of 205 MWp in 1999.     

Development of an economical model to determine an appropriate feed-in tariff for grid-connected solar PV electricity in all states of Australia

Australia is a country with a vast amount of natural resources including sun and wind. Australia lies between latitude of 10–45°S and longitude of 112–152°E, with a daily solar exposure of between less than 3 MJ/(m² day) in winter and more than 30 MJ/(m² day) in summer.Global solar radiation in Australia varies between minimum of 3285 MJ/(m² year) in Hobart to 8760 MJ/(m² year) in Northern Territory. As a result of this wide range of radiation level there will be a big difference between costs of solar PV electricity in different locations.A study we have recently conducted on the solar PV electricity price in all states of Australia. For this purpose we have developed an economical model and a computer simulation to determine the accurate unit price of grid-connected roof-top solar photovoltaic (PV) electricity in A$/kWh for all state of Australia. The benefit of this computer simulation is that we can accurately determine the most appropriate feed-in tariff of grid-connected solar PV energy system. The main objective of this paper is to present the results of this study.A further objective of this paper is to present the details of the unit price of solar PV electricity in the state of Victoria in each month and then to compare with electricity price from conventional power systems, which is currently applied to this state. The state Victoria is located south of Australia and in terms of sun radiation is second lowest compared with the other Australian states.The computer simulation developed for this study makes it possible to determine the cost of grid-connected solar PV electricity at any location in any country based on availability of average daily solar exposure of each month as well as economical factors of the country.     

基于层次分析法的太阳能利用技术综合评价

本文首先利用一个非稳态传热模型对同一环境条件下光伏光热一体化（PV/T）系统、光伏系统（PV）和太阳能热水器的能效进行分析,然后采用层次分析法（AHP）对不同品质终端能源输出的太阳能利用系统的能效统一表征,并以北京、广州和银川为代表的不同城市自然环境及用电价格为条件的三种情景,对三种太阳能利用系统的综合能源利用效率、累计净收益和投资回收期进行分析。结果表明,太阳能利用系统的经济性不仅受到系统能源利用效率和成本的影响,系统所在地的自然环境和电价水平也会引起系统经济性发生变化,因此考虑多种因素的综合评价可以为太阳能技术推广提供更客观和准确的参考。     

Potential of photovoltaic systems in countries with high solar irradiation

Renewable energy sources derived principally from solar energy have been gaining ground over the last few years and are now beginning to contribute to the global energy mix. Solar energy in the form of direct electricity conversion (photovoltaics) is already very popular in countries such as the United States, Germany and Japan. The enormous potential of photovoltaic (PV) technology is also obvious and favourable in countries with high irradiation such as the Mediterranean region. The objective of this paper is to review the different up and coming PV technologies, to explore the potential of different PV systems in countries with high solar irradiation and to compare their performance through the assessment of thirteen different types of PV systems that have been installed side by side in Nicosia, Cyprus and Stuttgart, Germany. Finally useful insight into the performance of the PV systems as a function of the meteorological conditions and location will be highlighted.     

Performance comparison of a double-axis sun tracking versus fixed PV system

In the present study, performance results of two double axis sun tracking photovoltaic (PV) systems are analyzed after one year of operation. Two identical 7.9 kWp PV systems with the same modules and inverters were installed at Mugla University campus in October 2009. Measured data of the PV systems are compared with the simulated data. The performance measurements of the PV systems were carried out first when the PV systems were in a fixed position and then the PV systems were controlled while tracking the sun in two axis (on azimuth and solar altitude angles) and the necessary measurements were performed. Annual PV electricity yield is calculated as 11.53 MW h with 1459 kW h/kWp energy rating for 28 fixed tilt angle for each system. It is calculated that 30.79% more PV electricity is obtained in the double axis sun-tracking system when compared to the latitude tilt fixed system. The annual PV electricity fed to grid is 15.07 MW h with 1908 kW h/kWp for the double axis sun-tracking PV system between April-2010 and March-2011. The difference between the simulated and measured energy values are less than 5%. The results also allow the comparison of different solutions and the calculation of the electricity output.     

Energy return on investment (EROI) of mini-hydro and solar PV systems designed for a mini-grid

With dramatic cost declines and performance improvements, both mini-hydropower and solar photovoltaics (PV) now serve as core options to meet the growing demand for electricity in underserved regions worldwide. We compare the net energy return on energy invested (EROI) of mini-hydropower and solar electricity using five existing mini-hydropower installations in northern Thailand with grid-connected solar PV simulations. Both assessments use a life cycle perspective to estimate the EROI. We find that distributed mini-grids with penetrations of solar PV up to 50% of annual generation can exceed the EROI of some fossil-based traditional centralized grid systems. The analysis will help planners and engineers optimize mini-grids for energy payback and utilize local resources in their design. The results suggest higher EROI ratios for mini-hydropower plants than solar PV, though mini-hydropower plants typically yield lower EROI ratios than their large-scale hydropower counterparts.     

深圳首个户用太阳能示范系统分析

户用太阳能系统是非常有发展前景的可再生洁净能源利用方式之一。本文对深圳首个户用太阳能应用系统从结构原理、设备性能、建设成本、工作方式、经济效益和社会效益等方面进行了全面系统的分析。指出了在我国发达城市地区推广使用户用太阳能系统所产生的经济效益和社会效益，并由此阐明了该户用太阳能系统对我国户用太阳能并网发电与光伏产业发展的示范意义。     

Photovoltaic grid stabilization system using second life lithium battery

The operation of residential solar photovoltaic arrays are typically dependent on net energy metering (NEM) tariffs or feed in tariffs that allow the array owner to treat the electricity grid as an energy storage device. This study presents a model and simulation results of a photovoltaic array paired with a second life battery pack, a partially degraded lithium battery pack from an automotive application, for stabilizing the electricity grid interactions of residential photovoltaic systems and reducing the overall residential demand placed on the electricity grid. Two numerical simulations are performed on the operation of a second life battery pack. The first used an equivalent system model for the battery pack and measured solar production and residential loads to evaluate the system performance using one second time steps. The second model used hourly time steps and round trip efficiency for the battery, coupled with weather data and residential demand, to determine the system performance over the course of a year. The numerical investigation shows that the PV and battery system can substantially reduce the quantity of solar electricity that is exported to the distribution grid and decrease the impacts of sudden fluctuations in photovoltaic output due to cloud cover while providing significant reductions in the electricity demand placed on the grid. Copyright © 2015 John Wiley & Sons, Ltd.     

Solar energy scenarios in Brazil. Part two: Photovoltaics applications

This paper discusses some energy scenarios for photovoltaic applications in Brazil engendered by using SWERA database in order to demonstrate its potential for feasibility analysis and application in the energy planning for electricity generation. It discusses two major different markets: hybrid PV–Diesel installations in mini-grids of the off-grid Brazilian electricity system in the Amazon region, and grid-connected PV in urban areas of the interconnected Brazilian electricity system. The potential for using PV is huge, and can be estimated in tens to hundreds of MWp in the Amazon region alone, even if only a fraction of the existing Diesel-fired plants with a total installed capacity of over 620 MVA would fit to run in an optimum Diesel/PV mix. Most of the major cities in Brazil present greater electricity demand in summertime with the demand peak happening in the daytime period. This energy profile match the actual solar resource assessment provided by SWERA Data Archive, enabling grid-connected PV systems to provide an important contribution to the utility's capacity.     

太阳能光伏发电技术及其应用

随着现代工业的发展,全球能源危机和大气污染问题日益突出,太阳能作为理想的可再生能源受到了许多国家的重视。目前太阳能光伏发电技术正在迅速发展,应用的规模和范围也在不断地扩大,已成为当今世界新能源发电领域的一个研究热点。本文在介绍太阳能光伏发电基本原理的基础上,详细阐述了太阳能光伏发电的相关重要技术,论述了太阳能光伏发电技术的主要应用方式和应用领域,并分析了太阳能光伏发电技术的应用前景。     

Technico-economic analysis of off grid solar PV/Fuel cell energy system for residential community in desert region

A technico-economic analysis based on integrated modeling, simulation, and optimization approach is used in this study to design an off grid hybrid solar PV/Fuel Cell power system. The main objective is to optimize the design and develop dispatch control strategies of the standalone hybrid renewable power system to meet the desired electric load of a residential community located in a desert region. The effects of temperature and dust accumulation on the solar PV panels on the design and performance of the hybrid power system in a desert region is investigated. The goal of the proposed off-grid hybrid renewable energy system is to increase the penetration of renewable energy in the energy mix, reduce the greenhouse gas emissions from fossil fuel combustion, and lower the cost of energy from the power systems. Simulation, modeling, optimization and dispatch control strategies were used in this study to determine the performance and the cost of the proposed hybrid renewable power system. The simulation results show that the distributed power generation using solar PV and Fuel Cell energy systems integrated with an electrolyzer for hydrogen production and using cycle charging dispatch control strategy (the fuel cell will operate to meet the AC primary load and the surplus of electrical power is used to run the electrolyzer) offers the best performance. The hybrid power system was designed to meet the energy demand of 4500 kWh/day of the residential community (150 houses). The total power production from the distributed hybrid energy system was 52% from the solar PV, and 48% from the fuel cell. From the total electricity generated from the photovoltaic hydrogen fuel cell hybrid system, 80.70% is used to meet all the AC load of the residential community with negligible unmet AC primary load (0.08%), 14.08% is the input DC power for the electrolyzer for hydrogen production, 3.30% are the losses in the DC/AC inverter, and 1.84% is the excess power (dumped energy). The proposed off-grid hybrid renewable power system has 40.2% renewable fraction, is economically viable with a levelized cost of energy of 145 $/MWh and is environmentally friendly (zero carbon dioxide emissions during the electricity generation from the solar PV and Fuel Cell hybrid power system).     

Optimization of operational cost for a grid-supporting PV system with battery storage

Coupling an energy storage to a photovoltaic (PV) system not only increases the self-consumption but also solves the over-voltage issues if the cycling of the storage is properly controlled. Whatever the application the storage is used for, the primary concern of the system owner is to maximize the profits. Therefore, this paper addresses an energy management system for a PV system coupled with battery energy storage, which maximizes the daily economic benefits while curtailing the power injection to the grid in such a way that helps to mitigate over-voltage problems caused by reverse power flow. A time dependent grid feed-in limit is proposed achieve this objective. The daily operational cost that includes the energy cost and the battery degradation cost is considered as the objective function. The non-linear constrained optimization problem is solved using dynamic programming. The analyses are made to investigate the economic benefits of charging the battery from the grid. It is found that there is a possibility for these systems for participating in load-levelling if batteries are charged from the PV system. In order for that to be feasible, the peak-hour sell-back price for the energy from storage should be higher than the off-peak utility electricity price.     

Installation and operation of the first city centre PV monitoring station in the United Kingdom

Recent interest in the application of PV in buildings throughout northern Europe has developed a need for long-term records of the solar resource in urban situations. Previous records have usually been collected from locations quite remote from city centre sites and, furthermore, at hourly sampling frequencies which are not rapid enough for photovoltaic applications. The installation of a photovoltaic monitoring station in a city centre in the north-east of England is described. Weather monitoring instruments were installed to measure ambient temperature, wind speed and direction, relative humidity and solar irradiance. Four types of photovoltaic modules are mounted on the rig in typical buiding orientations in order to assess their performance with respect to PV cladding applications. Preliminary investigations have shown that the electricity generated by PV cladding on vertical surfaces experiences much less seasonal variation than that on a horizontal surface. The performance of north and south facing modules has also been compared and this has shown that the north facing modules generate reasonably large amounts of electricity, particularly during the summer months. The proportion of diffuse irradiance on a north facing surface has been studied and quantified for various amounts of global horizontal irradiance. Analysis of the cadmium telluride modules has confirmed a better response to diffuse irradiance than the silicon modules and records of the amorphous silicon module show no evidence of cell degradation.     

Modeling and simulation of grid-connected photovoltaic energy conversion systems

Solar power generation using PV (photovoltaic) technology is a key but still evolving technology with the fastest growing renewable-based market worldwide in the last decade. In this sector with tremendous potential for energy security and economic development, grid-connected PV systems are becoming today the most important application of solar PV generation. Based on this trend, PV system designers require an accurate and reliable tool in order to predict the dynamic performance of grid-tied PV systems at any operating conditions. This will allow evaluating the impact of PV generation on the electricity grids. This paper presents a detailed characterization of the performance and dynamic behavior of a grid-connected PV energy conversion system. To this aim, a flexible and accurate PV simulation and evaluation tool (called PVSET 1.0) is developed. The PV system is modeled, simulated and validated under the MATLAB/Simulink environment. The accuracy of simulation results has been verified using a 250 Wp PV experimental set-up.     

Domestic application of solar PV systems in Ireland: The reality of their economic viability

Renewable sources of energy are anticipated to play a major role in electricity generation in Ireland in the future. Currently, electricity is mainly generated from imported gas and coal due to a lack of indigenous fossil fuel resources in Ireland. Solar energy is omnipresent, freely available and environmental friendly. The utilisation of solar energy to produce electricity has become increasingly attractive worldwide. However, solar electricity generation has not been very popular in Ireland to-date either on a large scale or on a domestic scale. The unclear economics of domestic solar PV systems, under Irish conditions, is considered the biggest obstacle for expanding domestic solar PV system installation in Ireland. This paper presents a methodology to accurately evaluate the economic viability of a domestic solar PV system on a case-by-case basis. The methodology utilises the software programmes HOMER and Microsoft Excel 2007 for the energy and economic analyses. Utilising this methodology, a realistic economic analysis of eight sample domestic solar PV systems available in Ireland is presented. Based on the predictions, the domestic solar PV system is not economically viable under current conditions in Ireland. Domestic solar PV systems still do not look promising even if better financial support is given.     

PV hybrid systems for rural electrification in Thailand

Photovoltaic (PV) hybrid systems can make a positive contribution to the sustainability of rural communities in developing countries that do not have access to electricity grid. Integration of solar photovoltaic system with diesel generator for remote and rural areas would assist in expanding the electricity access in the tropical region. A survey of PV hybrid system in Thailand during the last decade regarding to status of technology, performance in terms of technical and economic aspects, and their prospects has been presented in this paper.