Monitoring and Controlling Energy Efficiency of Photovoltaic Installations

Transcription

1 Monitoring and Controlling Energy Efficiency of Photovoltaic Installations Features System Current and voltage supervision of solar panels Control of switching states Sources Shunt and inductive sensors in string arrays Standard signals from temperature, wind speed, and irradiation sensors Door switches Digital outputs of power inverters Applications Solar Power Plants Off-Grid Systems Roof Systems pi-ipv_system_e V

2 Functions and Benefits Installations generating green energy have to be operated economically and efficiently to feed in a maximum of energy. For that consistent information about their efficiency is absolutely mandatory. Permanent control also provides early detection of defects and malfunction of a PV system or its solar panels. Further on additional access control and equipment condition monitoring should be set up. Data and state acquisition of the PV system is designed with modular components. There are modules measuring DC current and voltage of the individual strings, modules for panel temperature, and signals of wind speed and irradiation sensors. Digital-In modules monitor e.g. switching states of door switches and inverters. The individual DIN-rail modules are mounted in openfield array boxes or in a local indoor control cabinet as needed by application and quantity. There they are linked each time via an internal bus with an intelligent communication unit transmitting the collected data over a field bus (Modbus RS485 or CAN) to the next higher control level. The modular design allows manifold combinations and upgradings. So the modules are not just suited for large power plants, but also for monitoring of medium and small power installations. 2 pi-ipv_system_e V

3 The current-to-voltage characteristic of a solar panel built of several solar cells connected in series, reflects the specific properties of this power generator. The curve of a solar panel is very similar to a single cell, despite the different scale factor. Solar panels are again connected in series or in parallel to generate more current or voltage as appropriate. The energy efficiency of the strings is also remarkably dependent on a mismatch caused by e.g. shadowing of cells or different input resistances. Under normal conditions the characteristic curve is like: Fig.3 Schematic view of shadowing impact within a % range (solid line ideal characteristic) The output current of a solar panel is proportional to incident solar radiation. Maximum radiated power on earth is in the range of 800 to 1200 W/m². Fig.1 Schematic view of IV characteristic Voltage value at MPP is approximately 80% open circuit voltage of a solar panel. MPP (Maximum Power Point) is the operating point with maximum power as product of cell current and voltage: Fig. 2 Schematic view of maximum power characteristic From the characteristics it can be learned how important it is, that the operating voltage of the panels is not suppressed too much below the MPP, avoiding potential energy losses. Degradation of cells by internal or external influences over time can be seen instantly from the measured curves. Depending on how many panels are combined to a string, occurring malfunctions can also be localized physically precise. Fig. 4 Schematic view of irradiation impact within 100 to 1000 W/m² (solid line The energy yield of a panel is determined by its cell with the lowest yield. Degradation of cells by internal or external influences over time, can be seen instantly from the measured curves. Depending on how many panels are combined to a string, yield losses can also be localized physically precise. pi-ipv_system_e V

4 GHM GROUP - Standort Martens GHM Messtechnik GmbH Kiebitzhörn Barsbüttel GERMANY Phone Fax The energy yield of solar panels is also affected by cell temperature, as cell voltage is decreasing with increasing temperature. For reference, temperature in an array is measured exemplarily at a characteristic spot. Data from wind speed and irradiation sensors via signal current or voltage transmitters can also be acquired and incorporated in the monitoring of the installation. Switching states of e.g. doors can be supervised with the digital input module. This accommodates safety aspects (security control) or shutdown of inverters. Fig. 5 Schematic view of temperature impact within (from left) C (solid line) Temperature measurement can be done with a temperature transmitter with signal current or voltage output. Pt100 sensors can be used directly with optional adaptation of the AD module. The following listed measurement devices guarantee efficient monitoring of PV systems' energy yield. Further on malfunction of or in strings depending on the layout of the monitoring system can be recognized quickly, avoiding potential energy and financial losses with it. Device Overview Module Input Output Sensor Voltage Current Signal Voltage Signal Current Pt100 Digital-Out Internal (SPI) Modbus RS 485 CAN Page Voltage 5 Current 5 Signals AD 6 Signals D 6 Communication 7 Standard, Optional, per type of sensor Mistakes reserved, technical specifications subject to change without notice 4 pi-ipv_system_e V

5 GHM GROUP - Standort Martens GHM Messtechnik GmbH Kiebitzhörn Barsbüttel GERMANY Phone Fax Voltage Characteristics Current Characteristics This module serves to acquire DC voltage values in solar systems for string efficiency monitoring in medium sized or large facilities. Technical Data Supply voltage 24 V DC ± 10 % This module serves to acquire DC current values in solar systems for string efficiency monitoring in medium sized or large facilities. Technical Data Supply voltage 24 V DC ± 10 % Power consumption at nominal voltage appr W Power consumption at nominal voltage appr. 1.0 W (full load) Electrical isolation 1000 V DC Electrical isolation 1000 V DC Environmental temperature C Environmental temperature C Module Voltage 1 channel per module Accuracy Installation Power supply and internal bus with T-Bus connection of housing max V DC ± 2 % Module Current (2 channels) with power connector Accuracy Module Current (2 channels) contactless Accuracy Installation ± 25 max V DC < 1.5 % ± 50 max V DC < 1.5 % Voltage Power screw terminal 10 mm² Power supply and internal bus with T-Bus connection of housing Dimensions Current Power screw terminals 10 mm², contactless via feed through Dimensions Ordering Code Input 1 1 channel 2. Measuring quantity 1 Voltage 3. Output 5 Bus (internal) Ordering Code Input 2 2 channels (with power connector) 3 2 channels (contactless) 2. Measuring quantity 2 Current 3. Output 5 Bus (internal) pi-ipv_system_e V

6 GHM GROUP - Standort Martens GHM Messtechnik GmbH Kiebitzhörn Barsbüttel GERMANY Phone Fax Signals AD Characteristics Signals D Characteristics This module serves to acquire analog and digital signals in solar systems. Technical Data Supply voltage 24 V DC ± 10 % This module serves to acquire digital signals in solar systems. Technical Data Supply voltage 24 V DC ± 10 % Power consumption at nominal voltage 0.5 W) Power consumption at nominal voltage 0.25 W Electrical isolation 1000 V DC Electrical isolation 1000 V DC Environmental temperature C Environmental temperature C Module AD Signals Input Analog (2 channels) signal current or -voltage alternatively temperature Input Digital (2 channels) switch contacts Installation ma or V Pt100 open >16 kω Module D Signals Input Digital (8 channels) switch contacts Installation Power supply and internal bus with T-Bus connection of housing up to 24 V open >16 kω Power supply and internal bus with T-Bus connection of housing Signals via screw terminal 2.5 mm² Signals via screw terminal 2.5 mm² Dimensions Dimensions Ordering Code Input 2 2 channels analog and digital 2. Measuring quantity 3 Analog-I and Digital 4 Analog-Pt100 and Digital 5 Analog-U and Digital 3. Output 5 Bus (internal) Ordering Code Input 8 8 channels digital 2. Measuring quantity 6 Digital 3. Output 5 Bus (internal) 6 pi-ipv_system_e V

7 GHM GROUP - Standort Martens GHM Messtechnik GmbH Kiebitzhörn Barsbüttel GERMANY Phone Fax Communication Characteristics This module serves to transmit data acquired by the current, voltage, and signal modules of solar systems for string efficiency monitoring in medium sized or large facilities. Data of the individual measurement modules are picked up over the internal serial bus and processed. Up to 18 subscribers can be operated via the internal bus, and configured for ID and measurement ranges accordingly. The digitized measurement data are then transmitted via a field bus (Modbus RS485 or CAN) to the next superordinate level (like a local control unit or to a data logger for smaller facilities). Installation Power supply and external bus via screw terminal 2,5 mm² Measuring quantities and supply of the modules via internal bus with T-Bus connection of housing Dimensions Ordering Code Technical Data Supply voltage 24 V DC ± 10 % Power consumption at nominal voltage 10 W for 8 subscribers 1. Input 5 Bus (internal) 2. Measuring quantities 9 all 3. Output 7 CAN bus 8 Modbus RS485 Electrical isolation 1000 V DC Environmental temperature C Module Communication internal external serial Field bus (Modbus RS485, CAN bus) pi-ipv_system_e V

8 GHM GROUP - Standort Greisinger GHM Messtechnik GmbH Hans-Sachs-Straße Regenstauf GERMANY Phone Fax info@greisinger.de Accessories Various temperature sensors and transmitters (details see main catalog) Cable Sensor GTF 101 P Measurement Kit Temperature SL-Pt eco Set Pt100, Pt1000 Complete with cable sleeve and (open end) cable Extremely rugged Temperature Sensor with Transmitter GTMU Watertight and shockproof hand-held device (with Silicone protective cover) Waterproof temperature sensor Top quality carry case Manufacturer's calibration certificate Free factory calibration after 1 st year with automatic reminder by calibration lab Optimum adaptation with 4 different designs PT100 or Ni Cr-Ni sensor incl. transmitter Ready for mount and operation 8 pi-ipv_system_e V

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12 Product Overview Laboratory Instrumentation Industrial Sensors and Instrumentation Industrial Electronics Displays / Controller Transmitter / Signal conditioning Isolating converters Safety and Monitoring Devices Power Electronics Calibration and Testing Process Instrumentation Hygienic Design GHMadapt Temperature Flow Level / Filling Height Analysis Measuring Data Acquisition Data Logging and Monitoring Test Bench Measurement Technology Renewable Energies 12 pi-ipv_system_e V