and monitoring in pv power plant performance

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The importance of Solar Resource Assessment and Monitoring in PV Power Plant Performance

Ajith GopiAgency for New and Renewable Energy Research & Technology

(ANERT)

Department of Power, Govt. of Kerala

Thiruvananthapuram

Solar PV – Business Models

Solar Roof-top PV Plants

Ground Mounted PV Floating Solar

Floating Solar with Hydro

Microgrids Agri Photovoltaics

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Data Collection through integrated SCADA system

Eg: 100kWp Grid connected PV Power Plant at Kerala University

• 400 PV Modules of 250Wp

• 5 nos. of String Inverters

• Web monitoring

• Generation: more than1,50,000 units per year

Eg: 100kWp PV Plant at Kerala University – Typical Generation log from SCADA

Data Monitoring System (Conventional)

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Usually a dedicated data logging system (Hardware and software) for monitoring the plant shall be provided even if the inverter has embedded data logging system.

The following important weather parameters are to be measured as part of the datalogging system:

(a) Solar IrradianceGlobal Tilted Irradiation/ Global Horizontal Irradiation

(a) TemperatureModule Surface Temperature, Inverter inside temperature etc.

Data Monitoring System

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Solar Irradiance:

• A Pyranometer/ Solar cell based irradiation sensor (along with calibration certificate) shall be provided, with the sensor mounted in the plane of the array. Readout shall be integrated with data logging system : Advisable for lower kWp rooftop systems

• Pyranometer (Class II or better) shall be provided with the sensor mounted in the place of the array. Readout shall be integrated with data logging system : Advisable for higher kWp rooftop systems and utility scale plants.

Temperature:

Integrated temp, sensors for measuring the module surface temp., inverter inside enclosure temp, and ambient temp to be provided complete with readouts integrated with the data logging system.

Data Monitoring System - Parameters

a) AC Voltage

b) AC Output current

c) Output Power

d) Energy in kWh

e) DC Input Voltage

f) DC Input Current

g) Temperatures (C)

h) Invertor Status

i) Irradiation

j) Module temperature

k) String Voltage & Current (For

PV Plants from 100kWp onwards)

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IOT based Solar PV Monitoring System – Block Diagram

The Three Layer IOT

Architecture

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Performance ratio – Important metric (IEC 61724)

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Parameter Equation Unit

PERFORMANCE RATIO (PR)

Performance Ratio

The plant acceptance test period is five days long with the following minimum irradiance criteria for PR measurement.

At least three days must have irradiance measured in the plane of the array that is greater than 600 W/sq.m for three continuous hours, and the daily total irradiance must exceed 3,000 Wh/sq.m/day.

• Clouds• Aerosols• Water Vapor• Terrain

Major factors influencing Solar Radiations

PV Power plant - Why we collect Solar Data?• Technology selection

• Siting

• System design

• Performance monitoring

• Research

• The Direct irradiation is the solar radiation traveling on a straight line from the sun down to the surface of the earth

• The Diffused irradiation is scattered by molecules and particles in the atmosphere but that has still made it down to the surface of the earth.

There are various components of Solar Irradiance.

Direct Normal Irradiance(DNI)

Pyrheliometer

• Sunlight enters the instrument through a window and is directed onto a thermocouple which converts heat to an electrical signal that can be recorded.

• The amount of light that is coming perpendicular or (normal) to surface to the rays that come in a straight line from the direction of the sun at its current position in the sky.

• DNI is measured by Pyrheliometer

• The term, beam solar irradiance is used to denote the direct solar beam, incident on a horizontal surface.

• The solar radiation is incident perpendicularly on the receiving surface.

Diffused Horizontal Irradiation (DHI)

• Represents solar radiation that does not arrive on a direct path from the sun, but has been scattered by clouds and particles in the atmosphere and comes equally from all directions.

• It is the downward irradiance scattered by the atmospheric constituents and reflected and transmitted by the cloud and incident on a unit horizontal surface

• DHI measured by Shaded Pyranometer

• The precision spectral pyranometer being used has a black thermopile sensor protected by two concentric hemispherical optically ground covers.

• The detector is independent of wavelength of radiation over the solar energy spectrum.

• In this the shading disk are mounted on an automated solar tracker to ensure that the pyranometer is continuously shaded during the measurement.

Global Horizontal Irradiance(GHI)• This is the irradiance that reaches a horizontal unit surface.

• It is made up of the direct normal solar irradiance and the scattered diffuse solar irradiance.

• The total amount of radiation received from above by a surface which is horizontal (parallel) to the ground

• Measured by Pyranometer.

• Measures solar irradiation received from a solid angle of 2π radians on a horizontal surface.

• GHI= DNI* cos(Ѳz) + DHI

where Ѳz = solar zenith angle , which is the angle between the local zenith and the line of sight to the sun.

Type of data Advantage Disadvantage

Ground based measurements

accurate, site-specific

high temporal resolution

costly equipment, difficult to maintainlimited availability of long-term data

Satellite derived data

good availability of long- term datamost of the regions of the world

less accuratelow time resolution & missing ground-truth

Ground based v/s Satellite based Data collection

Ground Based Data CollectionSolar Radiation Resource Assessment (SRRA) stations• A SCADA system is able to monitor the real-time efficiency of the PV

system and continuously compare it with the theoretical efficiency to assess if the system is operating optimally

• Data from the weather station, inverters, combiner boxes, meters and transformers will be collected in data loggers and passed to a monitoring station, typically via Ethernet, RS485 or RS232 cables.

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Resource Maps - DHI, DNI, GHI prepared utilising SRRA station data by NIWE

Lightening arrestortower

6 m wind mast

PV panel

Rain gauge

Solar tracker at 1.5 m

Typical SRRA Station

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Ultrasonic Wind Sensor GPRS Antenna

GPS

Rain Gauge

Temperature/RH Sensor

Data Logger & Modem

Battery & Barometer

Meteorological Tower

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1.5 m Solar Tower

Solar Tracker

Shading Disc Assembly

Shaded Pyranometerfor Diffuse Horizontal Irradiance (DHI)

PyranometerGlobal Hor. Irr. (GHI)

Solar Tower

Pyrheliometer (DNI)

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2MW Solar PV Project at Kuzhalmannam ANERT’s Utility scale Solar Project

at Kuzhalmannam, Palakkad (Highlights)

• ANERT’s own land at Kuzhalmannam, Palakkad

• ANERT as the IPP with PPA with KSEB at the rate fixed by KSERC

• Solar PV Modules with Crystalline Silicon (C-Si) Technology

• The power plant has already evacuated more than 12 million units of Power to KSEB Grid

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2MW Kuzhalmannam PV Power Plant – SCADA Page_ 04-12-2017

Solar Radiation Resource Assessment (SRRA) station with quality and internationally calibrated measuring instruments

Solar panel for powering the system Rain Gauge Sensor Pyranometers and Pyrheliometer

Data Logger Wind Speed / Direction Sensor Rain Gauge Sensor

Quality Big Data being collected through SRRA remote server from the Utility Power Plant

Solar meteo data available from various resources

• NASA Surface meteorology and Solar Energy (NASA – SSE Wordwide)

• National Renewable Energy Laboratory (NREL)

• Meteonorm

• PV GIS ( Europe + Africa)

• Solar GIS Worldwide

National Renewable Energy Laboratory (NREL)

• Developing, updating, and disseminating the modeled National Solar Radiation Database (NSRDB)

• Offers a serially complete collection of meteorological and solar irradiance data sets for the United States and a growing list of international locations.

• The data set is publicly available

• Provides data of more than 8,055 weather stations

• The measured parameters are monthly means of global radiation, temperature, humidity, precipitation, days with precipitation, wind speed and direction, sunshine duration

• This data is not freely available

Meteonorm

• To optimise system performance, there is a need to ensure that the plant components function efficiently throughout the lifetime of the plant.

• Continuous monitoring of PV systems is essential to maximise the availability and yield of the system

• In large-scale solar PV power plants, voltage and current will typically be monitored at the inverter, combiner box or string level, each offering more granularity than the previous.

Need for Software tools

Solar Resource Assessment (SRA) and Energy Yield Analysis (EYA) – Software tools

• PV syst

• PV*Sol

• System Advisor Model(SAM)

• RETscreen

• Helioscope

PV syst• Used globally for the study, sizing, simulation and data analysis of

complete solar PV System.

• It deals with grid-connected, stand-alone, pumping and DC-grid (public transportation) PV systems

• In addition to the Meteo Database that is included in the software, PVsyst gives access to many meteorological data sources available on the web

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SolarGIS: Specific PV power output and Global Tilted irradiance

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Solar GIS: Global Horizontal Irradiation and Direct Normal Irradiation

PV*Sol• 3D solar software with the most detailed configuration and shade analysis

for PV systems.

• Climate locations with street-level resolution

• Includes the Photo Plan option

• Time of day tariffs can be defined

• Output of yield probabilities

• Definition of outputs, costs, performance indicators and CO2 fuel savings for a wide range of variables and optimise solar PV performance.

System Advisor Model(SAM)

• SAM is a techno-economic computer model for solar PV plants• Financial model• Performance Model

• Open source software not only for PV but also for other renewable sources modeling

• Performance models make calculations of a power system's electric output, generating a set of timeseries data that represents the system's electricity production over a single year.

• Financial models calculate financial metrics for various kinds of power projects based on a project's cash flows over an analysis period that you specify.

RETscreen• RETscreen Expert models a full range of clean energy sources

and technologies

• It is capable of performing energy analysis, financial modeling, GHG analysis and risk analysis.

• Both free and licensed versions available

• RETscreen Expert has analysis capabilities covering an entire project life cycle

Eg: 200kWp PV Power Plant- Retscreen simulation for environmental Benefits

• 772 PV Modules of 260Wp

• 8 nos. of String Inverters

• Feeding Power to a Utility

• Generation: 3,00,000 units per year

• Avoiding the release of abt. 340 tonnes of CO2 to the atmosphere per year

Eg: 200kWp PV Power Plant- Retscreen simulation for environmental parameters

• GHG Reduction: 340t CO2

• 62 Cars/Trucks not used for an year

• 788 Barrels of Crude Oil not consumed

• 77 Acres of Forest absorbing Carbon

Helioscope• Its robust 3D design and energy yield simulator

• Easy layout tools

• Bankable performance modeling

• Financial analysis

• Shading analysis

• Single line diagram

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Helioscope – Loss diagram

RESULTS AND OBSERVATIONS:

THE POWER GENERATION

TREND

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SITE DETAILS

Results of the Trends in Generation of a 25MWp PV plant

The Trend of solar

generation against the predicted

generation

CONCLUSIONS & THOUGHTS

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► With Mega solar farms becoming more popular worldwide, the effective measures for performance monitoring can be only initiated with the state-of-the-art SCADA / data monitoring system.

► Forecasting techniques for solar generation is becoming more accurate. This is being achieved by the accurate data collection utilizing precision measuring instruments and intelligent data collection systems.

► Distributed Energy Resources(DER) utilizing renewable energy are becoming more popular and need proper control and forecasting for this de-centralized systems. Hence, SRA becomes an inevitable part with DER.

► SRA helps in remote monitoring and brings analytics capabilities to support remote electrification which in turn ensures the functionality of RE microgrids.

CONCLUSIONS & THOUGHTS

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► Since solar resource is linked with the generation and the revenue earned / sold, SRA is the basic requirement for any solar/RE based Blockchain implementation.

► IoT is now being used for advanced SRA since it helps to avoid wired network in strings for huge solar power plants.

Thank you!

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ajithgopi@ieee.org