Supervisory Data Acquisition and Performance Analysis of a PV by xvi11400



        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.[1]
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:
                                                                            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                                                          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),
                                                                            Perthshire, Berwickshire, Nottingham, Milton Keynes,
    S.P.Chowdhury is with Jadavpur University, Kolkata, India (e-mail:                                                    Steelstown (N. Ireland), Sutton (South London), Sunderland
    T.Markvart is with University of Southampton, UK (email:                and Bridgend.[1]
    Y.H.Song     is     with    XJTLU      University,     China  (email:,

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.[2] 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.[6]       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%. [3][4][5][6].         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. [6][7] 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 [2][6]                  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
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
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
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

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.
                              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
Temperature coefficient Voc (V/°C)   -0.104             -0.127
Temperature coefficient of Isc       0.053 %/°C         1.67 mA/°C

                                                                        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
                                                                             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
  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

                                                                                              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
                                                                                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)

                               IX. RESULTS                                                                        Monthly Average Power and Energy Output of PV Installation vs Irradiance
                                                                                                                          Condition (After installation of weather station in Dec 06)

                                                                                   Power (W), Energy (kWh),
                                                                                                                  300                                Power

                                                                                      Irradiance (W/m2)
                                                                                                                  250                                Irradiance





                                                                                                                               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

                                                                         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
                                                                                                                                                                                               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

increase in electrical power and energy outputs of the                                                     250

installation after augmentation.                                                                           200


                              TABLE 7                                                                      100

      POWER AND ENERGY OUTPUTS BEFORE AND AFTER AUGMENTATION                                                50

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

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

Monthly Average Output of Sanyo Array (W)        146.00    165.00                                                                                                 Sanyo Array
                                                                                                                                                                  Sharp Array
                                                                            Power (W), Irradiance (W/m2)

Monthly Average Output of Sharp Array (W)          45.00   167.00                                          1200


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


                                                                                                                   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

                                                  Daily Maximum Power Output After Augmentation (Aug 07)
                                                                                                                Sanyo Array
                                                                                                                                                                                 X. CONCLUSION
                                                                                                                Sharp Array
        Power (W), Irradiance (W/m2)

                                       1200                                                                     Irradiance

                                                                                                                                                    This project has been particularly successful, especially when
                                                                                                                                                    looking into context of the original aims of the research:
                                                                                                                                                         • In improving the efficiency of the installation as a
                                                                                                                                                             whole. The initial figures show that there is
                                                                                                                                                             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      [1]
69.59                                    62.20                82.71                81.74            134.88             172.93             141.41    [2]
                                                                                                                                                    [3]   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                                                                                                           [4]   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                                                                                           [5]   C. Emanuele, I. Daniele, Rizzoli Rita and Zignani Flavio, “Silicon
system.                                                                                                                                                   Heterojunction Solar Cell: A New Buffer Layer Concept With Low-

     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
[6] 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
[7]                                  Department of Engineering Materials. In 1987 on award of 'Allocation de Sejour
[8] Technical Data sheet for Sharp Arrays available at                              Scientifique de Haut Niveau' by the French Government he spent four months at sharp_185w         ONERA/CERT in Toulouse. He was appointed Associate Professor at Instituto
[9] Technical Data sheet for Sanyo Arrays available at                              de Energia Solar at Universidad Politecnica de Madrid in 1991 before returning                 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
[10] 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.
[11] 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                                                                     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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