1 Supervisory Data Acquisition and Performance Analysis of a PV Array Installation with Data Logger S.Chowdhury, Member, IEEE, P.Day, Non-member, IEEE, G.A.Taylor, Member, IEEE S.P.Chowdhury, Member, IEEE, T.Markvart, Member, IEEE and Y.H.Song, Senior Member, IEEE organizations as a technology with the potential to supply a Abstract--Different photovoltaic (PV) technologies are being significant part of the worlds energy needs in a sustainable developed, tested and employed as small-scale on-site distributed and renewable manner. Moreover, due to the extensive generators for directly catering to the customer loads at the improvement in inverter technologies, PV generation is now distribution voltage level. In this connection, extensive off-line being preferred and deployed worldwide as distributed energy and laboratory based research is also being performed for resources (DER) for augmentation of local generation at studying and comparing the PV technologies as well as for assessing their effectiveness for on-site power generation. This distribution voltage level. The UK government has recently paper describes the performance evaluation and capacity committed £10 million towards encouraging the installation of augmentation of a laboratory-scale PV Array installation at photovoltaic systems on buildings in the UK as energy use in Brunel University, West London, UK, comprising a buildings accounts for over 30% of the UK's energy usage. In monocrystalline and a HIT PV array. The paper reports on the the UK, PV systems are also being used for a long time to collection of on-line electrical and weather data through an IP- provide high-reliability power for remote industrial use enabled data and utilisation of the data to evaluate the inaccessible locations, or where the small amount of power performance of the PV arrays under different solar irradiance required is more economically met from a stand-alone PV conditions. It also describes the capacity augmentation process and testing and validating the improvement in array system than from mains electricity. Some of such applications performance by comparing the power and energy outputs of the include: (i) to power navigation buoys, lighthouses and arrays before and after augmentation. offshore warning light vessels around the English and Welsh coastline, (ii) to trickle charge batteries for agricultural Index Terms--Monocrystalline, HIT Technology, Installation, applications, (iii) to provide power for lighting systems and Commissioning, Distributed, Sustainable, Renewable Energy, telephone boxes in premises like railway platforms, (iv) to Performance Evaluation and Capacity Augmentation, Weather power summer cottages and farm buildings. Major industrial Station. companies like Transco are using PV-powered control systems, data loggers and automatic reading equipment. I. INTRODUCTION Currently, water supply companies are using PV systems to P HOTOVOLTAIC (PV) generation involves the generation of electricity from free and inexhaustible solar energy. The major advantages of a PV system are (i) sustainable trickle charge their batteries in remote monitoring equipment, while the Meteorological Office has installed PV-powered remote sensing equipment in the north of the country. nature of solar energy as fuel (i) minimum environmental In the UK, the British Photovoltaic Association which was impact, (ii) drastic reduction in customers’ electric bills due to formed in 1991 with the aim to advance the development and free availability sunlight, (iv) long functional lifetime of over use of solar photovoltaic, to promote the use of PV within the 30 years with minimum maintenance and (v) silent operation. UK as well as other regions such as Africa, Asia and Latin Owing to these benefits Today PV systems are recognized by America decided to merge its membership with the governments, environmental organizations and commercial Renewable Energy Association in 2006 to provide added strength in the effort to develop and apply PV plants in the This work was funded by Royal Society, UK (Incoming India Fellowship UK. British Photovoltaic Association records 138 PV system Scheme) for 2006-2007. clusters installed around the UK, with a total (peak) S.Chowdhury is with Women’s Polytechnic, Kolkata, India (e-mail: firstname.lastname@example.org) generating capacity of approximately 2.28 MWp. It also P.Day is with Brunel University, West London, UK (e-mail: provides a comprehensive list of PV Building installations in email@example.com) different places in UK. PV systems of more than 25kWp G.A.Taylor is with Brunel University, West London, UK (e-mail: ratings have been installed in areas like Llanelli (Wales), firstname.lastname@example.org) Perthshire, Berwickshire, Nottingham, Milton Keynes, S.P.Chowdhury is with Jadavpur University, Kolkata, India (e-mail: email@example.com) Steelstown (N. Ireland), Sutton (South London), Sunderland T.Markvart is with University of Southampton, UK (email: and Bridgend. firstname.lastname@example.org). Y.H.Song is with XJTLU University, China (email: email@example.com, firstname.lastname@example.org). 2 Different crystalline silicon based and amorphous silicon installation set-up at Brunel University, UK comprising based technologies are being developed and tested for monocrystalline and HIT PV arrays feeding into the university improvement of performance of PV systems. Made using cells distribution network through dedicated inverters and a saw-cut from a single cylindrical silicon crystal, the weather station for monitoring the local weather parameters monocrystalline silicon cells have the advantage of high like solar irradiance, ambient temperature, % relative efficiencies, but are costlier than other types. On the other humidity, wind speed and wind direction. The relevant data hand, the multicrystalline cells made from ingots of melted for daily power and energy outputs of the arrays, operating and recrystallised silicon are cheaper but slightly less voltage and current, AC voltage at inverter terminals and efficient. Amorphous silicon or thin film cells are a little less system frequency and the weather parameters are collected efficient than crystalline based cells but are definitely and logged in through a data logger. The data can be accessed cheaper. A number of other materials like cadmium telluride from any terminal through the Brunel University Local Area (CdTe) and copper indium diselenide (CIS) are also being Network (LAN). The paper reports on the utilisation of this used in PV cells, owing to simpler manufacturing processes on-line collected data to evaluate the performance of the total and better efficiencies. Upcoming hybrid solutions like the amorphous silicon/crystalline silicon (s-Si:H/c-Si) PV Installation under different solar irradiance conditions and heterojunction (HJ) solar cells with features are now then performance optimisation through capacity augmentation becoming popular basically due to their excellent performance of the installation. The power and energy output of the and simple low-temperature production process. These Hybrid installation have been monitored daily since October 2006 and PV cells combines both monocrystalline and thin-film silicon the dependence of the same on solar irradiance have been to produce cells with the best features of both technologies. studied daily from December 2006 after the installation and The key feature of the HIT technology, as conceptualised by interfacing of the weather station to the analog and digital the Sanyo group is that a thin intrinsic layer of amorphous channels of the data logger. Collected data has been used to silicon is inserted between the amorphous emitter and the detect the level of underperformance of the Sharp array. Then crystalline base forming a HJ solar cell with heterogeneous the possible causes behind the underperformance have been intrinsic thin layer (HIT). The buffer layer, owing to its investigated and the most economic solution of capacity excellent passivating properties, gives very high open circuit augmentation arrived at. After capacity augmentation, the voltages and module efficiencies as high as 17%. . improvement in performance level have been again tested and A comparison of different PV technologies is given in Table-1 validated from collected data by comparing the increase in including their energy conversion efficiencies at Standard power and energy outputs of the arrays before and after Test Conditions (STC) of 25 °C, light intensity of 1000W/m² augmentation. and air mass = 1.5.  and annual energy generation per kWp (kilowatt peak power rating of PV modules at STC). II. BASIC SCHEME FOR PV ARRAY INSTALLATION TABLE 1 COMPARISON OF PV TECHNOLOGIES  The original Laboratory scale Grid-Connected Types of PV Mono- Multi- Thin Film Hybrid Photovoltaic (PV) Generation System in Brunel University Cells crystalline crystalline which was first installed in September 2006 consisted of three Cell 16-17% 14-15% 8-12% 18-19% series-connected 185Wp Sharp NUS5E3E monocrystalline Efficiency at STC PV modules with a total nominal power of 555Wp and three Module 13-15% 12-14% 5-7% 16-17% series-connected 210Wp Sanyo HIP-210NHE1 HIT PV Efficiency modules with a total nominal power of 630Wp resulting in a Area needed 7 m2 (Sharp) 8 m2 15.5m2 6-6.5m2 PV plant of nominal power rating of 1.185 kWp. Each Sharp per kWp (for (Sharp) (Kaneka) (Sanyo) modules) 16m2 NUS5E3E module uses 125mm square single crystal silicon (Unisolar) solar cells with 14.1% module conversion efficiency each Annual Energy 830 kWh/kWp 810 800 865 Sanyo HIP-210NHE1 module has 16.8% module conversion generated per kWh/kWp kWh/kWp kWh/kWp efficiency. Each array feeds power to the University utility kWp in UK distribution grid through a SMA make Sunny Boy SWR700 (South facing, 30° tilt) Multi-String Inverter specifically designed to be used with grid connected PV-plants. These inverters conform to the regulation G83/1 relevant to small scale generation plants. Annual Energy 107 kWh/m2 100 50-52 139-150 The installation also includes a weather station for monitoring generated per kWh/m2 kWh/m2 kWh/m2 m2 (south local weather parameters such as solar irradiance, ambient facing, 30° tilt) temperature, relative humidity, and wind speed and wind direction. Annual CO2 471 kg/kWp 460 kg/kWp 454 kg/kWp 491 Both the weather station and the inverters are monitored savings per kg/kWp and controlled through a specialised supervisory controller kWp Annual CO2 61 kg/m2 57 kg/m2 28 kg/m2 79-85 cum data logger connected to a computer terminal, linked to savings per m2 kg/m2 the internet through the Brunel University Local Area This paper describes a laboratory scale PV Array Network (LAN). The monitoring and data collection has 3 mainly been done through the IP enabled Sunny Boy Control Plus controller, which can also be used to configure and/or The weather station comprises the following components: control the operating status (e.g., ON, OFF, waiting, grid i) CM3 Pyranometer (Kipp & Zonen) for measuring solar monitoring, MPP search and MPP) for inverters both on-site irradiance (W/m2) and connected to ANALOG IN-1 Channel as well as remotely. This means, in essence this controller can of data logger. be used as a basic Supervisory Control and Data Acquisition ii) W200P Potentiometer Wind vane (Vector Inst.) for (SCADA) system. measuring wind direction in degrees (with reference to geographic North as 0 degree) and connected to ANALOG-IN 2 Channel of data logger. iii) MP100A Hygromer (Rotronic) for measuring ambient temperature (°C) and RH (%) and connected to ANALOG-IN 3 and 4 Channels of data logger. iv) A100R Switching Anemometer (Vector Instrument) for measuring wind speed (m/s) and connected to DIGITAL-IN Channel of data logger. IV. SUNNY BOY INVERTER SET-UP The Sunny Boy (SWR700) Multi-String Inverter manufactured by SMA, Germany is specifically designed to be used with grid connected PV-plants. The main benefits to Fig. 1. 1.765 kWp PV Array Installation using this inverter include: (i) It conforms to the G83/1 regulations concerning small After capacity augmentation, the current Sharp array consists scale generation plants of five series-connected 185Wp Sharp NUS5E3E modules (ii) It has an inbuilt anti-islanding unit; if the grid power fails with a nominal power rating 925Wp and the Sanyo array the SWR700 automatically goes into waiting mode and stop consists of four series-connected 210Wp Sanyo HIP- supplying power to the grid until the grid power is restored. 210NHE1 with a nominal power rating of 840Wp. The total (iii) Diagnosis and communication via Powerline installation currently has a nominal rating of 1.765 kWp. The Communication, radio transmission or via data cable like basic scheme of the current PV installation is shown in Fig. 1. RS232 or RS485 is possible. (iv) Surge voltage protection with integrated thermally III. PV ARRAY AND WEATHER STATION SET-UP monitored varistors. (v) Enclosure type IP65, suitable for outside installation. The PV installation comprises Sharp make monocrystalline (vi) Connection of DC input with waterproof snap cable and Sanyo make HIT arrays. Both the technologies use light connectors. trapping techniques with uneven surface layer composition (vii) Connection to AC utility with waterproof plug. ensuring the maximum amount of incoming light enters the Although the manufactured power rating of the SWR700 is solar cell with negligible loss through reflection. The technical 700W, the inverter can also be configured to work with arrays specifications for the two types of modules are listed in Table of smaller power ratings or voltage ranges as listed in Table 3. 2. TABLE 2 TABLE 3 TECHNICAL SPECIFICATION OF PV ARRAYS VOLTAGE AND POWER SETTING RANGES OF SWR700 Specification Sharp Array Sanyo Array Setting Input Voltage Range Nominal Output Power Technology Monocrystalline HIT 1 119…250 VDC 700 W Model NUS5E3E HIP-210NHE1 2 96…200 VDC 600 W No. of modules in Series 5 (previously 3) 4 (previously 3) 3 72…150 VDC 460 W Maximum Power (W) – Pmax 185 210 Maximum power voltage (V) – Vpm 24.0 41.3 Fig. 2 shows the internal arrangement and connections of Maximum power current (A) – Ipm 7.71 5.09 Open circuit voltage (V) – Voc 30.2 50.9 SWR700. Manual configuration of the SWR700 is a fairly Short Circuit Current (A) – Isc 8.54 5.57 simple exercise but it is hazardous and even lethal voltages Warranted minimum power (W) – 175.8 199.5 can be encountered within the enclosure. Besides, the Pmin SWR700 is a complex electronic device being quite Maximum system voltage (V) 1000 760 vulnerable to electrostatic discharges. Temperature coefficient of Pmax -0.485 -0.3 (%/°C) Temperature coefficient Voc (V/°C) -0.104 -0.127 Temperature coefficient of Isc 0.053 %/°C 1.67 mA/°C 4 to North as 0°) and wind speed (m/s) as data files stored in a dedicated folder in the master computer. For fast failure identification the Sunny Boy Control can send daily/hourly plant and failure reports via an external modem. Any alteration in the operating parameters of the SWR700 inverters, such as the start-up voltage for the inverter (Upv), starting or stopping operation, changing the mode of operation (waiting, grid monitoring or MPP) can be done in two ways i) locally through the Sunny Data Control Plus data logger/controller ii) remotely through the software Sunny Data Control provided with the data logger/controller Thus, in essence this data logger can be used as a basic Supervisory Control and Data Acquisition (SCADA) system Fig. 2. Internal Arrangement and Connections of SWR700 thorough which an operator is not only able to log data but can also use the same to make any decision making regarding Input voltage range VDC implies the total DC voltage alteration of operating parameters locally as well as from a generated by the array and the Nominal Power Output is the remote location. For both these methods, the essential nominal power rating of the modules. They can be calculated functions that affect the operation of the Sunny Boy Control as: are protected with a dynamic user password. Through the software, the security level can be changed to have Installer VDC = Vpm for each module x no. of modules per array Privileges by changing the Security level with password access leading to the privileges of setting the system Nominal Output Power = kWp for each module x no. of parameters for each device connected to the controller. This is modules per array the outcome of the Royal Society funded projects undertaken in School of Engineering and Design of Brunel University, Before augmentation, the setting for the arrays are chosen UK dealing with an approach based on grid computing from Table 3 as per the nominal kWp output and VDC technology with the following aims: generated per array as shown in Table 4 below: • To provide economic and adoptable approach for monitoring and control. TABLE 4 • To enable any number of generating unit to be INVERTER SETTING FOR THE PV ARRAYS BEFORE AUGMENTATION plugged-in in the proposed grid through LAN (without any restriction in plugging-in the number of Setting Sharp Array Sanyo Array Vpm 24.0 41.3 units). No. of modules in series 3 3 • Monitoring and controlling the unit from more than VDC 3 x 24 = 72 3 x 41.3 = 123.9 one location at the grid. kWp 185 x 3 = 555 210 x 3 = 630 Inverter Setting chosen 3 2 VI. PERFORMANCE ANALYSIS V. DATA MONITORING AND CONTROL When the instantaneous output of the array, recorded every 15sec by the Sunny Boy controller, from the 5th June, 2007 The Sunny Boy Controller Plus data logger is specifically were graphically plotted in Fig. 3, it can be clearly seen that designed to work with the SWR700 inverters and is being there was a significant underperformance problem with the used as the principal tool in Monitoring and Control of the Sharp Array. At the point where the Sanyo array was giving system. In the current installation, the controller is connected its highest output the Sharp array was continually dropping to the inverter using RS 485 transmission protocols. However out, leading to substantial effect on the power output and this equipment is particularly versatile and can be configured difficulty in system modelling. to use the onboard powerline communications whilst also having provisions for additional “NET Piggy-Backs” which are available in the following versions: Analogue Modem, ISDN, Ethernet and GSM (mobile). This data logger is set up, monitored and controlled through the software programming. This software is used to record the logged data for instant-to-instant power (Watt), energy output (kWh) of each array, daily energy yield, total energy yield from the time of installation and weather parameters like solar irradiance (W/m2), ambient temperature (°C), relative humidity, wind direction (degrees with respect 5 VII. PROPOSED SOLUTION After determining the cause of the problem the German manufactures of the Sunny Boy inverters, SMA6, were contacted to decide the best course of action. SMA responded by confirming that unfortunately the Sunny Boy inverters were not designed to work within the voltage to power ratio that the Sharp NU-SE3E5E module produced and provided a design tool GenAu_733.xls that could be used to determine the best configuration and modules to be used with the Sunny Boy inverters. Figure-5 shows the GenAu_733.xls design tool provided by SMA6. (a) Sanyo Array Two viable options towards rectifying the problem are as below:- 1. Sharp produces a similar module, the NT-S5E2E, also of 185WP but with a higher maximum working voltage (41.3 Vpm) which was identical to the Sanyo array. However this meant scraping the existing panels and spending the entire amount on procuring and installing new panels. 2. By buying two additional current modules and adjusting the configuration of the inverter, the existing installation could be modified to provide the correct voltage levels to work with the inverter, whilst also increasing the nominal power of the array. However, the downside to this was that a peak (b) Sharp Array output the current levels were above the recommended levels for the inverter. Fig. 3. Daily Trend of Power Output of the Arrays Before Augmentation An informed choice was made to go for option 2 as this left Table 5 also clearly indicates that despite there being only a enough budget to procure an additional Sanyo module to bring 12% difference in the nominal rating of the arrays there was the arrays into comparable nominal power and it was noted significant difference in the average daily yield, with the that the array would rarely be operating at peak output. This Sharp array at less than half of the output power of the Sanyo significantly increased the nominal power rating of the array. To determine the reasons behind the poor performance installation as a whole whilst making best use of the budget of the array, rigorous analysis was undertaken to judge partial available. shading of array, dirt sediments on array surface, damage or malfunction of any module as well as inverter, impedance of VIII. INVERTER SETTING AFTER AUGMENTATION connecting cables and incorrect configuration of the inverters. It was determined by closely studying the data that although Table 6 shows the changes made in the inverter settings after the modules were of similar power ratings, the Sharp array augmentation. Fig. 4 shows the changes in the trend of power had fewer cells in series and hence a lower output Voltage of output of the Sharp Array over a day before and after 24Vpm compared to the 41.3 Vpm of the Sanyo modules. Three augmentation done in July 16, 2007. The power output graph of the NU-S5E3E Sharp modules in series could not produce a clearly shows that the inverter is not going off line and is kept voltage high enough to trigger the inverter from grid- switch on steadily throughout the operating period. monitoring mode into operational mode. This then required suitable configuration of the inverter to get any performance. TABLE 6 However this was not the optimal settings for the inverter and INVERTER SETTING FOR THE PV ARRAYS AFTER AUGMENTATION Setting Sharp Array Sanyo Array hence resulted in poor performance of the Sharp array. Vpm 24.0 41.3 No. of modules in series 5 4 TABLE 5 VDC 5 x 24 = 120 4 x 41.3 = 165.2 COMPARISON OF ARRAY PERFORMANCES kWp 185 x 5 = 925 210 x 4 = 840 Inverter Setting chosen 2 1 Maximum power output 650 W 650W limited to (in order to compare the maximum power outputs of the arrays and to avoid overloading of the inverters) 6 IX. RESULTS Monthly Average Power and Energy Output of PV Installation vs Irradiance Condition (After installation of weather station in Dec 06) 350 Power (W), Energy (kWh), 300 Power Energy Irradiance (W/m2) 250 Irradiance 200 150 100 50 0 70 -p eS 70 -guA 70- lu J 7 0-nu J 7 0-y aM 7 0-rpA 70- raM 70-beF 7 0-na J 6 0-ceD 60- voN 60 -tcO 6 0-peS Months Fig. 5 Fig. 4. Daily Trend of Power output of Sharp Array Before and After Daily Average Power Output Before Augmentation (June 07) Augmentation 600 Sanyo Array Power (W), Irradiance (W/m2) Sharp Array 500 Daily Average Irradiance Fig. 4 compares the instantaneous power outputs of the Sharp array on June 05 2007 before augmentation with that on July 400 18, 2007 which was a very sunny day shortly after the 300 modification. 200 It can be seen from Fig. 4 that: 1. At no point during the day does the output fall low 100 enough for the inverter to click into waiting mode, 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 which it did regularly before the modifications. Days of Month 2. During a number of points during the day the output Fig. 6 leveled off at around 650W. This is the maximum voltage that the inverter would allow; obviously this has a negative effect on the net performance of the Daily Average Power Output After Augmentation (Aug 07) array. 500 Although the data used to compile these results only 450 Sanyo Array Power (W), Irradiance (W/m2) Sharp Array encompass a small period of time, the initial conclusions are 400 Irradiance that the modifications were a success. Table 7 shows the 350 300 increase in electrical power and energy outputs of the 250 installation after augmentation. 200 150 TABLE 7 100 POWER AND ENERGY OUTPUTS BEFORE AND AFTER AUGMENTATION 50 0 Power and Energy Values of PV Installation Jun-07 Aug-07 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 (Before) (After) Days of Month 2 Average Irradiance over a month (W/m ) 296.00 243.00 Fig. 7 Monthly Average Output - PV Installation (W) 190.00 331.00 Daily Maximum Power Output Before Augmentation (June 07) Monthly Energy Output - PV Installation (kWh) 81.74 172.94 1600 Monthly Average Output of Sanyo Array (W) 146.00 165.00 Sanyo Array Sharp Array Power (W), Irradiance (W/m2) 1400 Irradiance Monthly Average Output of Sharp Array (W) 45.00 167.00 1200 1000 The following graphs in Fig. 5 to Fig. 9 clearly indicate an 800 increase in average monthly and daily power and energy 600 outputs from the month of July after augmentation. 400 200 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Days of Month Fig. 8 7 Daily Maximum Power Output After Augmentation (Aug 07) 1400 Sanyo Array X. CONCLUSION Sharp Array Power (W), Irradiance (W/m2) 1200 Irradiance 1000 This project has been particularly successful, especially when looking into context of the original aims of the research: 800 • In improving the efficiency of the installation as a 600 whole. The initial figures show that there is 400 approximately a 100% increase in the power 200 generated by the installation. This was done by 0 making an informed choice to buy additional PV modules, that coupled with minor configuration 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Days of Month changes has shown a net power output of far greater Fig. 9 than the increase in generation capacity. • By using the communication capabilities of the Table 8 gives the estimated monthly average energy output up Sunny Boy Controller Plus a simple SCADA system to August 2007 without considering augmentation. was realised. This allowed detailed data acquisition TABLE 8 and simple control of the system, including remote ESTIMATED MONTHLY ENERGY OUTPUT IN KWH UP TO AUGUST 2007 access over TCP/IP on the Brunel University LAN. WITHOUT AUGMENTATION • The students of the new MSc course in Sustainable Power Generation of School of Engineering and Sept Oct Nov Dec Jan Feb Design, Brunel University have been extensively 2006 2006 2006 2006 2007 2007 51.08 40.55 31.11 16.18 22.31 31.71 using the aforesaid facility to collect on-line data from the PV Array installation in addition with the Mar Apr May June July* Aug* Weather Station data through Brunel Internet. These 2007 2007 2007 2007 2007 2007 on-line data are utilised for different performance 69.59 62.20 82.71 81.74 83.06 83.0 analyses of the PV Array. Further, from these data different co-relation studies are undertaken by MSc [* Estimated values for July 07 and August 07 assuming that students various intelligent algorithms. Average weather conditions to be same as July] The augmentation of the PV Array with the installation of new units in addition with the Weather Station provides an Total estimated kWh that would be obtained without excellent State-of-the-Art Laboratory facility in Brunel augmentation = 655.23 kWh University to update the knowledge of MSc students on renewable power generation and its Supervisory Data This figure of 655.23 kWh is somewhat lower than the Acquisition and Control facility. It is definitely timely and accredited installer’s predicted annual generation of the relevant particularly in the era of green power generation system of 850 kWh; however this can be contributed to the exploiting all the facilities of renewable generations. Sharp array’s underperformance. After augmentation in mid July 2007, the actual monthly energy output of the installation XI. ACKNOWLEDGMENT is given in Table 9 The authors would like to thank Royal Society, UK (Incoming India Fellowship Scheme) and Nuffield Science Bursaries for TABLE 9 ESTIMATED MONTHLY ENERGY OUTPUT IN KWH UP TO SEPTEMBER 2007 Undergraduate Research, UK for providing funds and Brunel AFTER AUGMENTATION Institute of Power Systems, School of Engineering and Design, Brunel University, UK for providing necessary Sept Oct Nov Dec Jan Feb infrastructure and facilities for undertaking this research 2006 2006 2006 2006 2007 2007 work. 51.08 40.55 31.11 16.18 22.31 31.71 Mar Apr May June July Aug Sept XII. REFERENCES 2007 2007 2007 2007 2007 2007 2007  http://www.greenenergy.org.uk/pvuk2/uk/pvapps.html 69.59 62.20 82.71 81.74 134.88 172.93 141.41  http://www.greenenergy.org.uk/pvuk2/technology/types.html  M. Tanaka, M. Taguchi, T. Matsuyama, T. Sawada, S. Tsuda, S.Nakano, H. Hanafusa, and Y. Kuwano, “Development of new a-Si/c-Si After augmentation, heterojunction solar cells: ACJ-HIT (artificially constructed junction Total kWh actually obtained up to August 2007 after heterojunction with intrinsic thin layer),” Jpn. J. Appl. Phys., vol. 31,pp. augmentation = 796.99 kWh 3518–3522, 1992. and that up to September 2007 = 938.4 kWh  M. Tanaka, S. Okamoto, S. Tsuge, and S. Kiyama, “Development of HIT solar cells with more than 21% conversion efficiency and commercialization of highest performance HIT modules,” Proc. Conf. Thus after augmentation, the energy output is well above the Photovoltaic Energy Conversion, pp. 955–958, 2003. accredited installer’s predicted annual generation of the  C. Emanuele, I. Daniele, Rizzoli Rita and Zignani Flavio, “Silicon system. Heterojunction Solar Cell: A New Buffer Layer Concept With Low- 8 Temperature Epitaxial Silicon”, IEEE Transactions On Electron Devices, Vol. 51, No. 11, Pages 1818 – 1824, November 2004. Dr.T.Markvart obtained his BSc (1st Class Hons) and PhD in Mathematical  T.Markvart, L.Castaner, Practical Handbook Of Photovoltaics, ISBN: Physics from the University of Birmingham. He came to Southampton in 1977 to 1857173909, 1015P, 2003 work as a Research Fellow in the Department of Mathematics and later  http://www.solarcentury.co.uk/content/pdf/2727 Department of Engineering Materials. In 1987 on award of 'Allocation de Sejour  Technical Data sheet for Sharp Arrays available at Scientifique de Haut Niveau' by the French Government he spent four months at http://www.solarcentury.co.uk/products/solar_photovoltaics/ sharp_185w ONERA/CERT in Toulouse. He was appointed Associate Professor at Instituto  Technical Data sheet for Sanyo Arrays available at de Energia Solar at Universidad Politecnica de Madrid in 1991 before returning http://www.sanyo.co.jp/clean/solar/hit_e/download_pdf/jet/HIP- to Southampton as Head of Solar Energy Centre. He was awarded the 205_210NH1-BO-1.pdf prestigious Royal Academy of Engineering/EPSRC Clean Technology  Data sheet for SWR700, SMA, String Inverter Sunny Boy 700, Fellowship in 1994, and became Reader in Electronic Materials in 2002. Installation Guide, Version 1.0, SB700-11:SW3205, IME-SB700.  Data sheet for SMA Sunny Boy Control Plus Data Logger available at Prof.Y.H.Song received his BEng, MSc and PhD in 1984, 1987 and 1989 www.SMA.de respectively. In 1991, he joined Bristol University, and then held various positions at Liverpool John Moores University and Bath University before he joined Brunel University in 1997 as Professor of Network Systems at the XIII. BIOGRAPHIES Department of Electronic and Computer Engineering. He was Director of Brunel Dr.S.Chowdhury received her BEE and PhD in 1991 and 1998 respectively. Advanced Institute of Network Systems and Pro-Vice-Chancellor of the She joined M/S M.N.Dastur & Co. Ltd as Electrical Engineer and Women’s University till 2006. He is currently Pro-Vice Chancellor of Liverpool Polytechnic, Kolkata, India as Lecturer in 1991 and 1998 respectively. She was University, UK and Executive Vice-President of Xi’an Jiaotong-Liverpool promoted to Senior Lecturer in 2006. She visited Brunel University, UK several University He has published four books and over 300 papers mainly in power times on collaborative research programmes. She has published two books and systems. He was awarded the Higher Doctorate of Science (DSc) in 2002 by over 50 papers mainly in power systems. She is a Member of the IET (UK) and Brunel University for his significant research contributions. He is a fellow of the IE(I) and Member of IEEE(USA). She is acting as YM Coordinator in Indian IET (UK) and the Royal Academy of Engineering and Senior Member of Network of the IET(UK). IEEE(USA). P.Day is a student of Electronic & Electrical Engineering Undergraduate Course at Brunel University, West London; Currently on an Industrial Placement. Dr.G.A.Taylor is currently based at the Brunel Institute of Power Systems as a lecturer and course director. He received his BSc degree in Applied Physics from Royal Holloway College, London University, in 1987, and his MSc and PhD degrees in numerical analysis and modelling from the University of Greenwich in 1992 and 1997 respectively. He has contributed to over 50 publications concerning applications of computational modelling and numerical analysis in both power and general engineering problems. His current research interests include micro-generation and micro-grids, reactive power and voltage control, power system and network communications, power system and network operation, power system economics and electricity markets. He is a member of the IET (UK). Dr.S.P.Chowdhury received his BEE, MEE and PhD in 1987, 1989 and 1992 respectively. In 1993, he joined E.E.Dept. of Jadavpur University, Kolkata, India as Lecturer. He was promoted to Senior Lecturer and then to Reader grades in 1998. He visited Brunel University, UK several times on collaborative research programme. He has published two books and over 100 papers mainly in power systems. He is a fellow of the IET (UK) with C.Eng., IE(I) and the IETE(I) and Member of IEEE(USA). He is a member of Membership and Regions Board (MRB), MRB Finance Committee, Council and the Regional Representative Committee of the IET(UK).
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