IMPROVEMENT OF SOLAR PHOTOVOLTAIC MODULE EFFICIENCIES THROUGH WATER COOLING AND DEBRIS REMOVAL

Low energy conversion efficiency is one of the major problems that take place in the method of photovoltaic power generation. The factors that cause this problem to occur are mainly due to the extremely high operating surface temperatures of the photovoltaic module and the dust accumulation on the solar module surface. Therefore, the objectives set in this project are to highlight how these factors do affect the module performance and how can they be solved. The first objective of the case study is to study the effects of surface temperature cooling on the photovoltaic modules while the second objective emphasizes on the performance of PV modules with respect to debris accumulation on the module surface. In order to carry out the project, a prototype was first built to implement the method of water cooling on the photovoltaic module. The performance of the module with water cooling is then compared to the conventional module (no modifications). As for the debris accumulation study, the conventional module is covered with opaque sheets of different sizes resembling the dust coverage area on module surfaces and the output power is compared with the module with water cooling (zero dust coverage). Based on the results obtained, it can be analysed that when the water cooling technique is applied on the PV module, the average highest performance improvement comparing to the conventional module, reaches up to a maximum value of 43.24% (5th July 2013). This proves that the addition of water layer helps in improving the amount of power generated for a specific solar irradiation, thus efficiencies increase as well from 11.01% to 17.45%. As for the dust accumulation experiment, the highest average performance improvement achieved is 89.94%; when comparing the module with water cooling to the conventional module set up with 50% dust area coverage. The module with water cooling also has an improved efficiency of 23.92% compared to the efficiency of the conventional module with dust coverage which is only 10.61%, at peak hours. Hence, the project study carried out proves that improvement of the photovoltaic module efficiencies is highly possible with application of the water cooling method. This method does not only reduce the surface temperatures of the module, but also prevent dust settlement on the module surface as well

Grid-tie inverter topology with maximum power extraction from two photovoltaic arrays

This study presents a transformerless topology for a grid-tied single-phase inverter capable of performing the simultaneous maximum power point tracking of two independent and series connected photovoltaic sources. This topology is derived from the neutral point clamped multilevel inverter in half-bridge configuration. The use of a half-bridge topology reduces the leakage current to very low values, whereas the multilevel topology presents an output voltage quality similar to that of a full-bridge inverter. To simultaneously track the maximum power of both photovoltaic sources, a generation control circuit is used. With this topology, it is possible to improve the performance of the converter under partial shadowing conditions, very common in photovoltaic facilities operating in residential areas. A 5 kW prototype of this topology has been implemented and tested in the laboratory.This work is supported by the Spanish Ministry of Science and Innovation under grants ENE2009-13998-C02-02 and ENE2012-37667-C02-01.Patrao Herrero, I.; Gabriel Garcerá; Figueres Amorós, E.; González Medina, R. (2014). Grid-tie inverter topology with maximum power extraction from two photovoltaic arrays. Renewable Power Generation, IET. 8(6):638-648. doi:10.1049/iet-rpg.2013.0143S63864886Bevrani, H., Ghosh, A., & Ledwich, G. (2010). Renewable energy sources and frequency regulation: survey and new perspectives. IET Renewable Power Generation, 4(5), 438. doi:10.1049/iet-rpg.2009.0049Zhu, J., Bründlinger, R., Mühlberger, T., Betts, T. R., & Gottschalg, R. (2011). Optimised inverter sizing for photovoltaic systems in high-latitude maritime climates. IET Renewable Power Generation, 5(1), 58. doi:10.1049/iet-rpg.2009.0162Amoiralis, E. I., Tsili, M. A., & Kladas, A. G. (2012). Power Transformer Economic Evaluation in Decentralized Electricity Markets. IEEE Transactions on Industrial Electronics, 59(5), 2329-2341. doi:10.1109/tie.2011.2157291Bowtell, L., & Ahfock, A. (2010). Direct current offset controller for transformerless single-phase photovoltaic grid-connected inverters. IET Renewable Power Generation, 4(5), 428. doi:10.1049/iet-rpg.2009.0043Patrao, I., Figueres, E., González-Espín, F., & Garcerá, G. (2011). Transformerless topologies for grid-connected single-phase photovoltaic inverters. Renewable and Sustainable Energy Reviews, 15(7), 3423-3431. doi:10.1016/j.rser.2011.03.034Kjaer, S. B., Pedersen, J. K., & Blaabjerg, F. (2005). A Review of Single-Phase Grid-Connected Inverters for Photovoltaic Modules. IEEE Transactions on Industry Applications, 41(5), 1292-1306. doi:10.1109/tia.2005.853371Puttgen, H. B., MacGregor, P. R., & Lambert, F. C. (2003). Distributed generation: Semantic hype or the dawn of a new era? IEEE Power and Energy Magazine, 1(1), 22-29. doi:10.1109/mpae.2003.1180357Nian, H., & Zeng, R. (2011). Improved control strategy for stand-alone distributed generation system under unbalanced and non-linear loads. IET Renewable Power Generation, 5(5), 323. doi:10.1049/iet-rpg.2010.0216Thomson, M., & Infield, D. G. (2007). Impact of widespread photovoltaics generation on distribution systems. IET Renewable Power Generation, 1(1), 33. doi:10.1049/iet-rpg:20060009Karatepe, E., Syafaruddin, & Hiyama, T. (2010). Simple and high-efficiency photovoltaic system under non-uniform operating conditions. IET Renewable Power Generation, 4(4), 354. doi:10.1049/iet-rpg.2009.0150Wang, Y.-J., & Hsu, P.-C. (2010). Analytical modelling of partial shading and different orientation of photovoltaic modules. IET Renewable Power Generation, 4(3), 272. doi:10.1049/iet-rpg.2009.0157López, Ó., Freijedo, F. D., Yepes, A. G., Fernández-Comesaña, P., Malvar, J., Teodorescu, R., & Doval-Gandoy, J. (2010). Eliminating Ground Current in a Transformerless Photovoltaic Application. IEEE Transactions on Energy Conversion, 25(1), 140-147. doi:10.1109/tec.2009.2037810Cavalcanti, M. C., Farias, A. M., Oliveira, K. C., Neves, F. A. S., & Afonso, J. L. (2012). Eliminating Leakage Currents in Neutral Point Clamped Inverters for Photovoltaic Systems. IEEE Transactions on Industrial Electronics, 59(1), 435-443. doi:10.1109/tie.2011.2138671Wu, T.-F., Chang, C.-H., Lin, L.-C., & Kuo, C.-L. (2011). Power Loss Comparison of Single- and Two-Stage Grid-Connected Photovoltaic Systems. IEEE Transactions on Energy Conversion, 26(2), 707-715. doi:10.1109/tec.2011.2123897Shimizu, T., Hirakata, M., Kamezawa, T., & Watanabe, H. (2001). Generation control circuit for photovoltaic modules. IEEE Transactions on Power Electronics, 16(3), 293-300. doi:10.1109/63.923760Gonzalez-Espin, F., Figueres, E., & Garcera, G. (2012). An Adaptive Synchronous-Reference-Frame Phase-Locked Loop for Power Quality Improvement in a Polluted Utility Grid. IEEE Transactions on Industrial Electronics, 59(6), 2718-2731. doi:10.1109/tie.2011.2166236Mastromauro, R. A., Liserre, M., & Dell’Aquila, A. (2012). Control Issues in Single-Stage Photovoltaic Systems: MPPT, Current and Voltage Control. IEEE Transactions on Industrial Informatics, 8(2), 241-254. doi:10.1109/tii.2012.2186973Delfino, F., Denegri, G. B., Procopio, R., & Invernizzi, M. (2012). Feedback linearisation oriented approach to Q–V control of grid connected photovoltaic units. IET Renewable Power Generation, 6(5), 324-339. doi:10.1049/iet-rpg.2011.0075Ishaque, K., & Salam, Z. (2013). A review of maximum power point tracking techniques of PV system for uniform insolation and partial shading condition. Renewable and Sustainable Energy Reviews, 19, 475-488. doi:10.1016/j.rser.2012.11.03

Potential for Solar Energy in Food Manufacturing, Distribution and Retail

The overall aim of the study was to assess the potential for increasing the use of solar energy in the food sector. For comparative purposes the study also included an assessment of the benefits that could arise from the use of other renewable energy sources, and the potential for more effective use of energy in food retail and distribution. Specific objectives were to: i) establish the current state of the art in relevant available solar technology; ii) identify the barriers for the adoption of solar technology; iii) assess the potential for solar energy capture; iv) appraise the potential of alternative relevant technologies for providing renewable energy; v) assess the benefits from energy saving technologies; vi) compare the alternative strategies for the next 5-10 years and vii) Consider the merits of specific research programmes on solar energy and energy conservation in the food sector. To obtain the views of the main stakeholders in the relevant food and energy sectors on the opportunities and barriers to the adoption of solar energy and other renewable energy technologies by the food industry, personal interviews and structured questionnaires tailored to the main stakeholders (supermarkets, consultants for supermarket design; energy and equipment suppliers) were used. The main findings from the questionnaires and interviews are: - Key personnel in supermarkets and engineers involved in the design of supermarkets are aware of the potential contribution of renewable energy technologies and other energy conservation measures to energy conservation and environmental impact reduction in the food industry. A number of supermarket chains have implemented such technologies at pilot scale to gain operating experience, and more importantly, for marketing reasons, to gain competitive advantage through a green image. - From installations to date in the UK the most notable are a 600 kW wind turbine at a Sainsbury's distribution centre in East Kilbride and a 60 kWp photovoltaic array at a Tesco store in Swansea. - The main barrier to the application of renewable energy technologies in the food sector is the capital cost. Even though significant progress has been made towards the improvement of the energy conversion efficiencies of photovoltaic technologies (PVs) and reduction in their cost, payback periods are still far too long, for them to become attractive to the food industry. - Wind energy can be more attractive than PVs in areas of high wind speed. Apart from relatively high cost, the main barrier to the wide application of wind turbines for local power generation is planning restrictions. This technology is more attractive for application in food distribution centres that are normally located outside build-up areas where planning restrictions can be less severe than in urban areas. In these applications it is likely that preference will be for large wind turbines of more than 1.0 MW power generation capacity as the cost of generation per unit power reduces with the size of the turbine

Power Quality Improvement and Low Voltage Ride through Capability in Hybrid Wind-PV Farms Grid-Connected Using Dynamic Voltage Restorer

© 2018 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission.This paper proposes the application of a dynamic voltage restorer (DVR) to enhance the power quality and improve the low voltage ride through (LVRT) capability of a three-phase medium-voltage network connected to a hybrid distribution generation system. In this system, the photovoltaic (PV) plant and the wind turbine generator (WTG) are connected to the same point of common coupling (PCC) with a sensitive load. The WTG consists of a DFIG generator connected to the network via a step-up transformer. The PV system is connected to the PCC via a two-stage energy conversion (dc-dc converter and dc-ac inverter). This topology allows, first, the extraction of maximum power based on the incremental inductance technique. Second, it allows the connection of the PV system to the public grid through a step-up transformer. In addition, the DVR based on fuzzy logic controller is connected to the same PCC. Different fault condition scenarios are tested for improving the efficiency and the quality of the power supply and compliance with the requirements of the LVRT grid code. The results of the LVRT capability, voltage stability, active power, reactive power, injected current, and dc link voltage, speed of turbine, and power factor at the PCC are presented with and without the contribution of the DVR system.Peer reviewe

量子ドット太陽電池とペロブスカイト太陽電池における界面エンジニアリングと界面電荷移動ダイナミクス

電気通信大学201

A hierarchical architecture for increasing efficiency of large photovoltaic plants under non-homogeneous solar irradiation

Under non-homogeneous solar irradiation, photovoltaic (PV) panels receive different solar irradiance, resulting in a decrease in efficiency of the PV generation system. There are a few technical options to fix this issue that goes under the name of mismatch. One of these is the reconfiguration of the PV generation system, namely changing the connections of the PV panels from the initial configuration to the optimal one. Such technique has been widely considered for small systems, due to the excessive number of required switches. In this paper, the authors propose a new method for increasing the efficiency of large PV systems under non-homogeneous solar irradiation using Series-Parallel (SP) topology. In the first part of the paper, the authors propose a method containing two key points: a switching matrix to change the connection of PV panels based on SP topology and the proof that the SP-based reconfiguration method can increase the efficiency of the photovoltaic system up to 50%. In the second part, the authors propose the extension of the method proposed in the first part to improve the efficiency of large solar generation systems by means of a two-levels architecture to minimize the cost of fabrication of the switching matrix

Assessment of the photovoltaic potential at urban level based on 3D city models: A case study and new methodological approach

The use of 3D city models combined with simulation functionalities allows to quantify energy demand and renewable generation for a very large set of buildings. The scope of this paper is to determine the solar photovoltaic potential at an urban and regional scale using CityGML geometry descriptions of every building. An innovative urban simulation platform is used to calculate the PV potential of the Ludwigsburg County in south-west Germany, in which every building was simulated by using 3D city models. Both technical and economic potential (considering roof area and insolation thresholds) are investigated, as well as two different PV efficiency scenarios. In this way, it was possible to determine the fraction of the electricity demand that can be covered in each municipality and the whole region, deciding the best strategy, the profitability of the investments and determining optimal locations. Additionally, another important contribution is a literature review regarding the different methods of PV potential estimation and the available roof area reduction coefficients. An economic analysis and emission assessment has also been developed. The results of the study show that it is possible to achieve high annual rates of covered electricity demand in several municipalities for some of the considered scenarios, reaching even more than 100% in some cases. The use of all available roof space (technical potential) could cover 77% of the region’s electricity consumption and 56% as an economic potential with only high irradiance roofs considered. The proposed methodological approach should contribute valuably in helping policy-making processes and communicating the advantages of distributed generation and PV systems in buildings to regulators, researchers and the general public

Investigation of the energy performance of a novel modular solar building envelope

The major challenges for the integration of solar collecting devices into a building envelope are related to the poor aesthetic view of the appearance of buildings in addition to the low efficiency in collection, transportation, and utilization of the solar thermal and electrical energy. To tackle these challenges, a novel design for the integration of solar collecting elements into the building envelope was proposed and discussed. This involves the dedicated modular and multiple-layer combination of the building shielding, insulation, and solar collecting elements. On the basis of the proposed modular structure, the energy performance of the solar envelope was investigated by using the Energy-Plus software. It was found that the solar thermal efficiency of the modular envelope is in the range of 41.78–59.47%, while its electrical efficiency is around 3.51% higher than the envelopes having photovoltaic (PV) alone. The modular solar envelope can increase thermal efficiency by around 8.49% and the electrical efficiency by around 0.31%, compared to the traditional solar photovoltaic/thermal (PV/T) envelopes. Thus, we have created a new envelope solution with enhanced solar efficiency and an improved aesthetic view of the entire building