Solar Grid Research Articles

Direct Current and Alternative Current Based Solar Micro-Grid in Rural Energy Infrastructure

In India kerosene uses as primary source of lighting- 43% of rural and 7.1% of urban households, even most populated African countries (Uganda, Ethiopia, and Kenya) more than 60% of the population relies on kerosene as the primary lighting fuel. Though they have access to grid electrification the unreliable supply leaves them in complete darkness and hence compelling them to think of alternatives. Poor electrification and unreliable supply lead to usage of kerosene based lighting devices such as kerosene lamps, which not only provides lowly quality illumination but also results in hazardous smoke. Off-grid electrification can provide an alternative solution for many low demand users at lower cost than grid extension and market growth of rural energy service. Costs of off-grid technologies have decreased significantly over the last few years hence making it affordable. Morden micro grid has come up with a way to make lighting system accessible to most of the rural households. Solar based renewable energy technologies extensively development in the last decade, the Solar photo voltaic cell converts light energy into direct current using the photovoltaic effect. Battery devices storing the extra power generated at day time and used during nights. Inverters and power Store Electronic Systems are used to convert direct current power generated by solar photo voltaic systems to alternative current, and utilization of direct current /alternative current in renewable energy power system at higher capital cost. But the internal rate of interest makes it superior to other system. This paper a latest researcher’s review of assessment of Direct current (DC) and Alternative current (AC) based Solar Micro-grid in rural community. The paper is therefore structured as follows: overview of micro-grid AC and DC system with case studies. Sensibility analysis in Compression with decentralized Diesel Genset (DG) based on Net present value (NPV) Internal rate of interest (IRR) for DG set 92% (not included as environmental economics), the IRR for solar micro-grids 50% and solar micro-grids with Government subsidy 80%. Opportunities and challenges involved in the implementation of solar mini grid in rural energy infrastructure.

Power quality assessment of a solar photovoltaic two-stage grid connected system: Using fuzzy and proportional integral controlled dynamic voltage restorer approach

Dynamic voltage restorer (DVR) is used to protect sensitive loads in voltage disturbances of distribution generation (DG) system. In this paper, a variable step size incremental resistance based incremental conductance maximum power point tracking (MPPT) technique is implemented for solar photovoltaic (PV) grid connected system. A power quality study which includes perturb & observe (P&O) MPPT comparison is carried out during fault on grid side. At the same time, proportional integral and artificial intelligence-based fuzzy-logic controlled DVR is operated which injects voltage during the faulted grid side. Simulation results during fault show fuzzy logic based DVR scheme demonstrates simultaneous exchange of active reactive power, less total harmonic distortion in voltage source converter (VSC) current and grid current, less fluctuation of DC bus voltage to VSC, less DC current injection, and fast tracking of optimum operating point at unity power factor. This paper aims at simulating and validations of MPPT technique and VSC control approach using manufacturer's solar PV data sheet; fuzzy logic controlled DVR demonstrates effectiveness of proposed control schemes. The whole framework results in a simulation PV-DG model which constitutes a computer-aided design tool that is helpful for PV professionals who require simple, fast, and accurate PV simulator to design their systems precisely.

Solar Grid Parity dynamics in Italy: A real option approach

Over the past three years Italy has seen a rapid growth in the PV (photovoltaic) energy market, followed by an equally sudden decline when the government decided to reduce the incentives. This sharp change in the trend of the market calls into question the achievement of the so called Grid Parity and the possibility that the market is able to develop independently. The motivation of this paper is to evaluate the effects that uncertainties surrounding both the energy prices and PV module costs have on forecasting the dynamics of the Italian PV market. Using the Real Option approach we calculate “the best time to invest” in a PV system by a maximizing investor. We show that these sources of uncertainty can delay the optimal investment decision of several years compared to current Grid Parity forecasts, well describing the current market situation in Italy.

Solar Grid Parity Dynamics in Italy: A Real Option Approach

Over the past three years Italy has witnessed a rapid growth in the photovoltaic energy market, followed by an equally sudden decline when the government decided to reduce the incentives. This sharp change in the trend of the market calls into question the achievement of Grid Parity and the possibility that the market is able to develop independently. Starting from the standard Grid Parity Model, widely used for the photovoltaic (PV) market, we internalize the uncertainty surrounding both the energy price and PV module costs, to forecast the dynamics of the Italian PV market. We show that these sources of uncertainty can delay the Grid Parity timing of several years compared to current forecasts, well describing the current market situation.

Smart water grid: desalination water management platform

This paper presents a desalination process powered by a microgrid. Desalination is critically important for many countries demanding potable water beyond that available in nature. The desalination process requires a stable power supply system. As the stable power supply system, microgrid, which is a distributed small capacity power system integrating renewable energy with energy storage, has become important. In this paper, small capacity desalination plant powered by a microgrid is implemented and its features are described. The desalination plant is operated by electricity provided from either renewable energy resource such as solar cell or power grid. Overall control of the desalination plant is carried out by a programmable logic controller and status of water production is monitored by energy management system. The implemented desalination plant consumes 5 kW and produces 1 m3/h of fresh water.

Research on Application of Solar Photovoltaic Grid Power System Research

Research on the conditions of solar photovoltaic grid connected power generation, research the form of converting solar energy into electrical energy generating.This paper introduces the solar photovoltaic system components, advantages and disadvantages as well as the current domestic solar photovoltaic power generation application status, prospect the development of the trend in the future, according to the analysis of the present problems. And relying on Tianjin CNOOC oil development group of Yingkou natural gas terminal 330KW solar photovoltaic power generation demonstration projects are introduced. For the photovoltaic CNOOC Yingkou terminal-station problems presents the feasibility scheme and suggestion.

Short-term irradiance forecasting using skycams: Motivation and development

This paper examines the motivation, applications and development of short-term solar forecasting using ground-based sky imagery for controlling equipment on electrical grids.Historically, there has not been a great deal of interaction between the fields of solar forecasting and electrical grid research. This situation is changing rapidly as solar forecasting is becoming increasingly important for dealing with the mass uptake of photovoltaics (PV) and solar-thermal generation on electrical grids around the world. The interactions in these two fields is examined, along with the opportunities for applying solar forecasting for on-grid and mini-grid applications.We review solar forecasting techniques, summarise their applications and evaluate the links to suitable techniques with applications. A review of current solar forecasting techniques, including Numerical Weather Prediction (NWP), statistical/data-driven approaches, and satellite techniques is presented. We also compare the characteristics of each technique to illustrate the requirements, status and suitability of each for use in short-term solar forecasting applications. The application of sky-camera (‘skycam’) forecasting in electrical grids is discussed in addition to the presentation of a detailed case study demonstrating the use of these techniques to enhance grid operation. The control strategy developed demonstrates an increase the real-time penetration of renewable power by dynamically adapting solar inverter setpoints according to cloud forecast data.A novel short-term solar forecasting system is presented which makes use of inexpensive ground-based sky imaging cameras (or ‘skycams’). This system is able to predict changes in irradiance by forecasting cloud movement up to 20min ahead, with a 10s update frequency.Several novel techniques for skycam setup and forecasting are presented. These include:(a)A new, high-performance approach to cloud classification using a novel set of neural network input features.(b)A new method for calibrating a lens distortion model.(c)A novel technique using per-pixel cloud movement vectors to predict the timing and extent of sun shading events.This latter technique is capable of correctly classifying 97% of cloud pixels from a validation database of over 500,000 examples.Finally, we present a new technique for taking features extracted from sky-camera pixel data and building a model for predicting large shading events. We show an example of how this model can be easily adapted for either conservative or aggressive operation of a solar power system with a backup generator. In conservative operation, this model is shown to supply adequate or excess energy up to 99.96% of the time using 4min-ahead forecasts when used for scheduling a backup electrical generator; meaning the system would require only minimal battery storage, while producing a large reduction in fossil-fuel consumption.

Can solar panels leapfrog power grids? The World Bank experience 1992–2009

Abstract Solar photovoltaic systems promise both rural access to electricity and reduction in greenhouse gas emissions. During 1992–2009, the World Bank contributed US$790 million to promote the uptake of off-grid solar home systems in 34 developing countries. This paper reviews the experience of the World Bank involvement in the rural solar photovoltaic market and draws lessons learned. The review finds that World Bank efforts, using quality-contingent producer subsidies and relying on microfinance for consumers, have been effective in stimulating the diffusion of the solar technology although the impact on greenhouse gas reductions is rather limited because of limited energy consumption of off-grid households.

Reducing shadowing losses with femtosecond‐laser‐written deflective optical elements in the bulk of EVA encapsulation

AbstractA new approach on decreasing the optical shadowing of the solar cell grid fingers is presented. The approach relies on a local change of the optical properties in the bulk of the photovoltaic module encapsulation material ethylene vinyl acetate (EVA). In particular, scattering and diffractive optical elements are locally generated within the volume of cross‐linked EVA encapsulation material by applying a femtosecond‐laser‐writing process. When these optical elements are located above the metal grid fingers, the optical shadowing of these grid fingers can be decreased. In an experimental proof of concept, the optical performance of this approach is demonstrated. The best results obtained so far indicate a decrease in optical shadowing by 17%. The material characteristics of the volume optics were investigated by applying confocal Raman microscopic characterisation, which indicates that the EVA material partially degraded upon the impact of the laser beam and is partly carbonised. Supplementary optical simulations show that the light deflection is caused by diffraction. However, parasitic absorption substantially deteriorates the optical performance of the deflective volume optics. Copyright © 2014 John Wiley & Sons, Ltd.

THD reduction with reactive power compensation for fuzzy logic DVR based solar PV grid connected system

Dynamic voltage restorer (DVR) is used to protect sensitive loads from voltage disturbances of the distribution generation (DG) system. In this paper, a new control approach for the 200 kW solar photovoltaic grid connected system with perturb and observe maximum power point tracking (MPPT) technique is implemented. Power quality improvement with comparison is conducted during fault with proportional integral (PI) and artificial intelligence-based fuzzy logic controlled DVR. MPPT tracks the actual variable DC link voltage while deriving the maximum power from a photovoltaic array and maintains DC link voltage constant by changing modulation index of the converter. Simulation results during fault show that the fuzzy logic based DVR scheme demonstrates simultaneous exchange of active and reactive power with less total harmonic distortion (THD) present in voltage source converter (VSC) current and grid current with fast tracking of optimum operating point at unity power factor. Standards (IEEE-519/1547), stipulates that the current with THD greater than 5% cannot be injected into the grid by any distributed generation source. Simulation results and validations of MPPT technique and operation of fuzzy logic controlled DVR demonstrate the effectiveness of the proposed control schemes.

Study on Effects of Solar Generation on Power Grid

The climate change and the shortage of energy have made the solar energy as the priority renewable energy in many countries, and solar energy is under the fast development. Since the solar energy has the intrinsic intermittence and fluctuation, its integration into the power grid will lead to the power fluctuations. The paper proposes a method of deploying the photovoltaic generation which is the main solar generation technology in China to meet the load demand in order to reduce the storage investment. The analysis shows that there is a strong correlation between daytime solar generation fluctuations and grid load fluctuations, and it is able to use solar plant instead of some peek-load regulating generator units. Therefore, solar generation technology also has great potential of integration ability even without the use of energy storage, and the purpose of solar generation is to increase the share of solar electriciy at the lowest unit cost rather than to guarantee 100% utilization factor.

The Constant Voltage Composite Control Method of the SVC with Unbalanced Load Compensation

in practical application of SVC, unbalanced load system exists on many sites, and the voltage at system access point is required to meet the demand of power grid operation. This paper describes a SVC constant voltage control method for an unbalanced load system. the control algorithm controls the voltage at evaluation point to reach the preset range while compensating reactive power of unbalanced load system. the control method could compensate an unbalanced load system into a balanced system, at the same time, the voltage at access point could meet the demand of power grid operation. This control method is particularly applicable to reactive control requirements of steel mills, wind power, solar power grid systems. This algorithm has been applied in Lishizhai 66kV SVC Project in Fushun, inhibits three-phase unbalance of the grid, has achieved good compensation effect.

Features of a fully renewable US electricity system: Optimized mixes of wind and solar PV and transmission grid extensions

A future energy system is likely to rely heavily on wind and solar PV. To quantify general features of such a weather dependent electricity supply in the contiguous US, wind and solar PV generation data are calculated, based on 32 years of weather data with temporal resolution of 1h and spatial resolution of 40×40km2, assuming site-suitability-based and stochastic wind and solar capacity distributions. The regional wind-and-solar mixes matching load and generation closest on seasonal timescales cluster around 80% solar share, owing to the US summer load peak. This mix more than halves long-term storage requirements, compared to wind only. The mixes matching generation and load best on daily timescales lie at about 80% wind share, due to the nightly gap in solar production. Going from solar only to this mix reduces backup energy needs by about 50%. Furthermore, we calculate shifts in FERC (Federal Energy Regulatory Commission)-level LCOE (Levelized Costs Of Electricity) for wind and solar PV due to differing weather conditions. Regional LCOE vary by up to 29%, and LCOE-optimal mixes largely follow resource quality. A transmission network enhancement among FERC regions is constructed to transfer high penetrations of solar and wind across FERC boundaries, employing a novel least-cost optimization.

Solar PV and Battery Storage Integration using a New Configuration of a Three-Level NPC Inverter With Advanced Control Strategy

In this paper, a novel configuration of a three-level neutral-point-clamped (NPC) inverter that can integrate solar photovoltaic (PV) with battery storage in a grid-connected system is proposed. The strength of the proposed topology lies in a novel, extended unbalance three-level vector modulation technique that can generate the correct ac voltage under unbalanced dc voltage conditions. This paper presents the design philosophy of the proposed configuration and the theoretical framework of the proposed modulation technique. A new control algorithm for the proposed system is also presented in order to control the power delivery between the solar PV, battery, and grid, which simultaneously provides maximum power point tracking (MPPT) operation for the solar PV. The effectiveness of the proposed methodology is investigated by the simulation of several scenarios, including battery charging and discharging with different levels of solar irradiation. The proposed methodology and topology is further validated using an experimental setup in the laboratory.

Modeling and Lifetime Assessment of Lithium-Ion Batteries Used for Solar Firming Applications and Grid Storage

The intermittent nature of many renewable power sources inhibits their implementation in the electric grid (1). Consumers demand an uninterrupted power supply and the unpredictable nature of renewables means that only a portion of the electric grid’s energy portfolio can come from these sources. However adding an energy storage device to renewable power sources can stabilize the source’s intermittency.A coupled system can supply a constant level of power to the grid (below the system’s peak generation rating) by storing part of the energy created during peak generation hours and releasing that energy during periods of low or no power generation (see figure 1).Our study utilizes a model of a photovoltaic solar cell coupled with a Lithium-ion battery. The system charges the battery anytime power generation exceeds the goal constant output and discharges the battery when the solar power output falls below the goal output. This protocol will control the system with the goal of generating the highest constant power output while still protecting the battery from degradation. Stabilizing the power source inevitably leads to sub-optimal charging and discharging patterns for the Li-ion battery and additionally can lead to intermittent cycling (small depth of discharge or small charging percentages). Our control strategy will seek to optimize both systems for single cycle and lifetime results.The hybrid system will involve an electrochemical and transport based Li-ion battery model (2-5). Intermittent charging patterns obtained from solar insolation variations will be studied and their effects on capacity fade will be analyzed. The study will focus on the lifetime benefit that can be obtained from a battery during implementation into a solar firming application and seeks to understand the dynamics associated with coupled solar-battery system. Acknowledgements The authors acknowledge financial support from the U.S. Department of Energy’s Advanced Research Projects Agency- Energy (ARPA-E), and the Solar Energy Research Institute in India and the United States (SERIIUS), as well as, Washington University in St. Louis’ McDonnell Academy Global Energy and Environmental Partnership (MAGEEP)

A dynamic assessment based feasibility study of concentrating solar power in China

The technology of concentrating solar power (CSP) is a potential way to meet the increasing demand of electricity consumption and environmental sustainability. However, it is still difficult to determine the installed locations of CSP systems, electricity generation by the systems, and the cost of CSP electricity in China. After a comprehensive geographic assessment, this study analyzes the technical and economic feasibility of 100 MW CSP systems to investigate the development potential of three types of CSP systems (i.e. parabolic trough system, tower system and dish Stirling system) under Chinese conditions in the period of 2010–2050. Based on the geographic assessment in terms of solar resource, land resource, water resource and power grid analysis, six locations are selected as the representative sites of each potential region for installing CSP systems. The performance analysis is further carried out, and the results show that the six representative locations are suitable for installing CSP systems because the higher solar-to-electricity efficiency can be generated compared to the average one of CSP systems. Due to the high time dependency of the cost of CSP electricity, a dynamic assessment based on feasibility analysis method is applied to study the economic performances of CSP systems based on the predictions of CSP cumulative installed capacity in four scenarios proposed by International Energy Agency (IEA). It is found that the grid parities of parabolic trough system and tower system will be achieved as early as the next 10–20 years for the selected locations. The integration analysis of geographic assessment, technical and economic feasibility demonstrates that China has sufficient potential for the utilization of parabolic trough system and tower system.

Energy policy and financing options to achieve solar energy grid penetration targets: Accounting for external costs

Abstract This paper presents a review and assessment of public-policy options for supporting large-scale penetration of photovoltaics (PV) in the United States. The goal therein is to reduce the costs both of solar technology and of grid integration, so enabling solar deployment nationwide. In this context, we analyze the solar PV markets and the solar industry globally, and discuss the external benefits of PV that must be advertised, and perhaps marketed, to assure an increase in social support for PV. We discuss existing energy-policy mixes in those countries leading to the development of solar power, highlighting the lessons learnt, and outlining areas of improvement of the existing policy mix in the United States. We highlight that there is a need for a holistic approach including social in addition to economic considerations, and we discuss policy options for supporting the continuation of PV market growth when the current investment tax credits expire.

Comparative Analysis of Solar Photovoltaic Lighting Systems in India

This study is based on extensive survey of selected photovoltaic (PV) programs in India and presents a comparative analysis of four prevalent solar lighting technologies, namely Solar Home System, Solar Charging Station, Solar AC Mini Grid and Solar DC Micro Grid employed for rural electrification in India. The study is focused on technical, financial, and institutional aspects of these programs along with the social impact assessment of PV based electrification in rural households. The findings of this study revealed that private entrepreneurship based delivery model have shown better performance as compared to the subsidy based delivery model. It is also found that beneficiary ownership play a vital role in the performance and sustainability of PV programs. We suggest that financial support, local need based technical innovations, developing local technical expertise and sensitization and training of all stakeholders are key parameters to enhance the operational sustainability of the PV programs.

Preparation of micro-sized and monodisperse crystalline silver particles used for silicon solar cell electronic paste

In this paper, monodisperse crystalline silver particles in microscale were prepared via chemical reduction method and the reaction conditions were systematically investigated. Gelatin was used as surfactant to prevent the agglomeration of silver particles. The crystallized and mono-disperse silver particles were obtained at the optimal synthesis condition (1.2 mol/L silver nitrate, 0.8 mol/L ascorbic acid, gelatin/silver = 0.025 wt% and pH = 1.5). The average particle size of the silver particles is 1–2 μm and the tap density of silver particles is over 5.0 g/cm3. The pH value is a key factor for preparation of crystallized silver particles. When the pH value increases from 1.0 to 4.0, the morphology of silver particles changes from polyhedron crystalline to spherical particles. The silver particles were used for preparation of the lead-free silver paste for monocrystalline silicon solar cell and the solar cell grid electrode has low resistivity and high adhesion strength.

Commentary: Fostering innovation in materials sciences and engineering

[http://dx.doi.org/10.1063/1.4811499]For many years, industry progressed with the idea that suitable materials were always available,but now this is not the case for a number of challenges: sustainable energy production and storage,future ICT (Information and Communication Technology), green transport, and health applications.We have passed from the perception “materials are in the drawer” to the perception “materials arethe bottleneck.” Research on better performing and sustainable materials will be a pre-condition tomeeting such challenges. Progress will come through the development of intelligent materials thatembed and transfer knowledge into products and processes or perform certain tasks, when in use orduring manufacturing. Already, some 70% of all technical innovations hinge directly or indirectlyon the properties of the materials employed.Materials research has an essential role to play in meeting the increasingly complex needs ofindustry and society, for example, greener, smaller, lighter, and cheaper products. But while it isessential to examine all aspects of a product’s life cycle to make substantial reductions in the useof resources, we also need to address any environmental and health concerns. Failure to do so mayslow the take up of innovations. Any “dark side” or drawbacks to new materials must be dulyascertained. The possible toxicological or eco-toxicological effects must be studied according to aprecautionary approach. Since the first emergence of nanotechnology in materials engineering, theEuropean Commission has elaborated and promoted a model of integrated, safe, and responsibledevelopment. There has been a double ethical concern: to prevent risks that may derive from a too-rapid deployment of novel technologies that are not yet known well enough and, at the same time,a desire to allow citizens to benefit from technological advances, as in the case of new treatment ofdiseases via targeted delivery of nanoparticles.TheEuropeanCommissionhasrecognisedtherelevanceofadvancedmaterialsandsingledthemoutforsupportinitsKeyEnablingTechnologies(KETs)initiative,launchedin2009.TheseKETsarenanotechnology, micro-nanoelectronics, advanced materials, photonics, industrial biotechnology,and advanced manufacturing systems. Mastering and deploying KETs in the European Union iscentral to strengthening industrial innovation and the development of new products and servicesneeded to deliver smart, sustainable, and inclusive European growth. Significant economic benefitscan be expected offering a widening variety of uses in an increasing number of application areas andindustries, as well as contributing to energy and resource efficiency through innovative materials,processes, technologies, and applications. In a resource-scarce Europe, new products must have lowmaterial/energy resource needs and high knowledge content.The Commission published in the end of 2011 “Materials Roadmap Enabling Low CarbonEnergy Technologies.” The document, based on contributions from nearly one hundred leadingscientists and industrial researchers, shows that materials are at the core of developments in the11 technologies covered: wind energy, photovoltaic energy, concentrating solar power, geothermalenergy, electricity grids, electricity storage, bioenergy, carbon capture and storage, nuclear fission,