Basic maintenance of the Solar PV system

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Introduction

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Performance of solar rooftop PV system with regular & basic maintenance improves. For best system performance, regular maintenance is necessary. This leads to increased system life and decrease in disruptions due to component failures. 

Also a data log for fault diagnosis during system maintenance should be maintained. 

[mk_blockquote font_family=”none”]“Solar power systems operate safely with regular maintenance”[/mk_blockquote]

Basic maintenance in a solar system that an owner has to care for :

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Solar Panels:

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One of the most important job is to clean the solar panels regularly. During the cleaning, panels need to be washed with the help of a hose pipe to remove the dust and dirt on the surface of the panel. This enhances power generation. 

Incase of dense or stubborn layers of dirt, modules need cleaning with a sponge or soft cloth or glass wiper after spraying some water. Glass layer needs to be wiped gently to avoid cracks due to small stone particles in the dust.  Even the bird droppings need a similar treatment. It helps decrease the effort to clean and at the same time removes the bird droppings completely. 

More importantly, the ideal time to clean panels is before 8 AM or after 5 PM. It avoids the microcracks on the module glass surface.

It is also suggested to remove the dry leaves if any to avoid long term problems like water clogging, short circuit due to moisture and fungus etc.PS: Since, modules are placed on the rooftop, it is very important to have safe walkways for the cleaning of the modules. Incase of a complicated rooftop, it is highly recommended to use a safety harness before considering cleaning the modules.

Modules with and without dust
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Inverter:

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Inverters convert DC into AC power. They generally require very little maintenance. 

  • Keep the inverter clean by wiping it with a dry cloth to avoid dust blowing inside. Necessary care needs to be taken while cleaning. 
  • Check the inverter LED color for the status of the system. If it displays GREEN, the system is working fine, if it displays BLUE, then there is a  problem with INTERNET connection which needs to sorted with help of internet provider, if it displays RED, there’s an ERROR in the system – do contact installer/customer care immediately. 
Inverter
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Balance of the system:

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Balance of the system includes the protection devices like Fuses, Surge Protection Devices (SPD), Circuit breakers, Monitoring interface and miscellaneous items.

All these needs to be checked once a while as they are first ones that are prone to failure due to grid instability, lightning etc. 

 

  • Check all the circuit breakers and switches if they are in working condition
  • Find if the Surge Protection Device (SPD) is working fine. If the SPD display color is dark, then it needs to be addressed immediately. Contact the installer immediately.
  • Check the earthing (grounding) cable to see if there are any disconnections in between. 
  • Lightning arrester connections and clamps should be checked if they in place without any disruptions
  • Monitoring. SolarEdge power optimizer systems come with module level monitoring. It helps in monitoring the system remotely. Regular look at it will help understanding drop in generation giving an alarm that modules need cleaning. In case of any other issues like failure of optimizer or panel will be known immediately decreasing the maintenance time and money and increasing productivity of system. Following image is the screen shot of one of the sites where there is shadow on two panels. This shows how shadow can effect the generation of each panel.
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Selection of SolarEdge power optimizer and inverter

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Introduction

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SolarEdge offers its latest cuttingedge technology to wide variety of customers from residential to commercial building owners. Offering ranges from 1kW till the maximum required or possible to install.

With wide range of selection, it’s very essential to choose the right power optimizer and inverter combination. It is decided based on the building requirement and size of the system needed.

There are typically two types of inverters we look at in rooftop segment. Single phase inverter and Three phase inverter. In single phase, we have Compact technology and HD Wave technology. Whereas, in three phase we have normal three phase inverters and Synergy technology. Single phase inverters range between 1-5kW where as three phase inverters are greater than or equal to 5kW.

Below chart gives overview details about the selection of optimizers possible for respective inverters.

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Selection of Power Optimizer based on Inverter size

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Inverter and Optimizer combination

Each of the inverter and the optimizers listed above have certain limitations in terms of string length. These factors are important to be considered as cables are designed for certain wattages based on the system size.

Following chart explains the minimum number of optimizers needed and maximum wattage each string is capable of.

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Selection of Power Optimizer for Inverter

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String length

**With P730 – For SE27.6k, SE55k, SE82.8k: It is allowed to install upto 13,500W per string when there are 3 strings connected to the inverter. The maximum power difference between the strings is upto 2000W

**For SE27.6k the maximum inverter DC power is 37,250W

**No optimizer listed in the above table can be mixed in same string.

For data sheets of the inverter and optimizer

With the help of SolarEdge designer tool, it is possible to do optimal design and create a generation report for the sytem to be proposed. Use of this tool helps in reducing the installation cost, time and at the same time increases the reliability.

[mk_title_box font_family=”none”]About Sunlit Future[/mk_title_box]

Sunlit Future with an experience of more than two decades also are distributors of SolarEdge power optimizer technology products. We offer technical support in terms of design, installation and commission of the system for the partners. Our aim is to provide quality installation to gain optimal generation of the system.

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Safe DC option with SolarEdge power optimizers

Safe DC option is an integrated feature in SolarEdge power optimizers and inverters. Safety of installers, maintenance personnel and firefighters is ensured with this option. This option shuts down DC current and voltage in strings when inverter is off or disconnected or in safety mode.

High string voltages are de-energized automatically to 1 Vdc per Power Optimizer and max. 50 Vdc per string in any of the above cases. Electrocution and unsafe high voltage risks are eliminated with this Trade Mark option.

Safe DC option can be triggered from SolarEdge fire fighter gateway aswell, providing centralised safety management.

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Working of Safe DC

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The SolarEdge Solution consists of a Inverter which communicates to Power Optimizers over Power line communication (PLC).
Safe DC is a mechanism which is build into the software of the Inverter and the Power Optimizer.

The Power Optimizers only harvest full power from the panels if the PLC signal is constantly renewed. If it fails the Power Optimizers initiates the Safe DC mechanism, which lowers the DC voltage to 1 Vdc per Optimizer. This feature works even when more than one panel is connected to it.

The 1 Vdc is necessary during installation and maintenance stage to check the proper working of the Power Optimizers.

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Advantages of SolarEdge Safe DC mechanism

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Installation

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During installation, panels are connected with Power Optimizers in strings. Safe DC is activated by default, lowering the operational voltage of the Power Optimizer to safe 1 Vdc, if the sun shines.

The maximum number of Power Optimizers in one String of panels is 50, therefore max. string voltage is 50 Vdc if all Power Optimizers are working properly.

Full power harvest can be safely activated when the Power Optimizers are connected and communicate with an SolarEdge inverter.

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[mk_button url=”https://www.solaredge.com/sites/default/files/solaredge_case_study_fire_safety_tasmasia_australia.pdf”]Case study on Safe DC[/mk_button]
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Emergency

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In case of a fire firefighters, mostly the AC wires of the house were cut to terminate the grid connection. Safe DC is automatically activated by the inverter if the grid connection is lost. This reduces the per power optimizers voltage to 1 Vdc. Eventually, max. 50 Vdc per String, lowering the risk for firefighters tremendously.

If properly educated, firefighters can also manually activate Safe DC by switching off the Inverter, the AC breaker or the AC/DC safety switch.

The Power Optimizers will also activate Safe DC by themselves if their thermal sensor senses a temperature above 85 °C, because such high temperatures typically indicate a fire near the PV System.

To activate Safe DC manually, inverter should be turned off so that it stops sending PLC signals to the Power Optimizers. Safe DC can also be activated if the connection to the AC side is interrupted by switching off the main AC breaker or AC/DC safety switch.

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Maintenance

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Maintaining PV system should be done regularly. Safe DC should be activated in order to reduce the high DC string voltages to a safe level. Maintenance like cleaning the panels, checking for defects, replacing panels or power optimizers should be considered only after activating the Safe DC mechanism.

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Sri Sarada Ashram, Ulundurpet

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Sri Sarada Ashram, Ulundurpet

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[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About Kalasalingam University[/mk_fancy_title]

Sri Sarada Ashram was established with the core objectives of promoting and developing the poor and the backward villages by means of quality education, affordable healthcare, cultural and socio-economic development activities, agricultural development and providing much needy and timely relief during natural disasters.

Located at Uludurpet, on the Chennai Trichy Highway in Tamilnadu, the Ashram houses 45 Sanyasin Sisters and services the remotest villages in and around the place. Over 1000 students and 500 women are given schooling, vocational training and job-oriented career coaching annually.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Why Solar[/mk_fancy_title]

Contributing towards the sustainable future with various initiatives in ashram, they had decided to add more to it. With regular training to the women in ashram, kids in the school there is a need of energy demand. Inorder to reduce the electricity bills and promote renewable energy, ashram decided to go ahead and install solar on its rooftops.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About the project[/mk_fancy_title]

A total of 63.28kWp of Solar rooftop system was installed on five different buildings using SolarEdge power optimizer technology. These buildings include main ashram building, boys hostel, pump house.

A 10kW solar rooftop system was installed earlier on one of the buildings by another vendor. Due to performance issues, revamp of the system was needed. Sunlit future had revamped the system and extended the system to 17kW with SolarEdge power optimizers technology. Existing 240Watt panels for 10kW and 7kW of 360Watt panels under one inverter were connected. This gives an affirmation that the system could be extended in future with no extra investment on inverter.

Satisfied with the performance of the revamped system, ashram authorities had reached us for solar on other buildings as well, extending it to 63.2kW

SolarEdge Power optimizer technology enhances the generation of each of these systems. They have module level MPPT which enhances the generation. Overall performance of the system is not compromised with shade on one module due to the trees or dust or bird droppings.

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Project Details

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Location Ulundurpet, Tamil Nadu
Owner Sri Sarada Ashram
Capacity 63.28kW
Number of panels (240 Watts) 42
Number of panels (310 Watts) 32
Number of panels (330 Watts) 50
Number of panels (340 Watts) 25
Number of panels (360 Watts) 51
Type of panels Mono-crystalline
Orientation ~South at angle 10°
Structure Pre fabricated
Inverter 17kVA SolarEdge (3 units)

10kVA SolarEdge (2 units)

Average units per day 265 kWh
Average units per year 97,008 kWh
Date of commissioning (Building-1) 24th March, 2018
Date of commissioning (Building-2) 19th July, 2018
Date of commissioning (Building-3) 20th July, 2018
Date of commissioning (Building-4) 25th July, 2018
Date of commissioning (Building-5) 24th April, 2019
[/mk_table][mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Generation & Savings[/mk_fancy_title]

This system was installed with Modbus meter enabling Net Zero option. All the generation of each of the systems is being utilized in the building and there is no excess generation that gets exported to the grid.

It saves about Rupees 52,000/month at an average with the generation. All the systems together takes about 5 years for the return of the investment.

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Installation specifications

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Solar on all the five buildings was installed on the flat roof with the help of pre fabricated cement ballast structure made of Aluminium. This structure helps in corrossion free and long durability of the system.

Safe walkways were provided ensuring seamless maintenance of the system. Cables were routed through UPVC pipes providing safety from external factors like weather, insects etc.

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Church of South India Synod, Chennai

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Church of South India Synod, Chennai

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[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About Church of South India[/mk_fancy_title]

The Church of South India (CSI) is the second largest Christian church in India based on the number of members and is result of union of Anglican and number of Protestant churches in South India.

The Church of South India is the successor of a number of Anglican and Protestant denominations in India, including the Church of England, the British Methodist Church and the Church of Scotland after Indian Independence.

The CSI synod consists of bishops of 24 dioceses, presbyters and layman (both men and women) who are elected from the respective diocesan councils to the synod. The synod members will elect the apex body consisting of a Moderator, Deputy Moderator, general secretary and Treasurer. The Moderator is the spiritual and administrative head of the Church.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Why Solar[/mk_fancy_title]

With a lot of visitors coming to be part of the church proceedings the guest house in CSI Synod is mostly full. With increasing visitors, building consumption is constantly increasing resulting in high electricity bills.

CSI Synod had decided on solar rooftop system while wondering about solving the high electricity bills.  They had approached Sunlit Future to install rooftop solar grid-tied systems on the guest house. It also inspires the visitors to consider sustainable solutions.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About the project[/mk_fancy_title]

A total of 100.56kW solar rooftop system was installed on the rooftop of the CSI-Synod.

CSI Synod had decided to go for the SolarEdge power optimizers and inverters rather than traditional string inverters to have a higher solar yield and greater savings.

These products aim to increase energy output through module-level Maximum Power Point Tracking (MPPT) and also provide module-level remote monitoring via the SolarEdge monitoring web portal and mobile app.

Complete system was connected with help of a Modbus meter which enables zero export option. As the building have equally high day time loads, they have considered to use Modbus meter till they get a bidirectional meter from the utility grid company.

It also captures the load of the complete building which helps in finding out the consumption patterns of the building.

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Project Details

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Location Whites Road, Chennai
Owner Church of South India, Synod
Capacity 100.64kW
Number of panels (370 Watts) 272
Type of panels Mono-crystalline
Orientation ~South at angle 10°
Structure Ganges
Inverter 27.6kVA SolarEdge (3 units)
Average units per day 422.7 kWh
Average units per year 1,54,281 kWh
Date of commissioning 24th May, 2019
[/mk_table][mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Generation & Savings[/mk_fancy_title]

100kWp of Solar rooftop system on CSI Synod building is saving them about Rs.90,500/month by generating about 12,000 kWh/month on an average.

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Installation specifications

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370Watt Mono crystalline modules were used on this system manufactured by Waaree Energies.

Complete project was installed on the flat roof with the help of Ganges structure at an angle of 10 degrees facing towards the south direction. Considering the height of the building, inorder to avoid high winds, structure was designed to be close to the floor.

Safe walkways were provided ensuring seamless maintenance of the system. Cables were routed through UPVC pipes providing safety from external factors like weather, insects etc.

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Kalasalingam Academy of Research and Education

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Kalasalingam Academy of Research and Education

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[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About Kalasalingam University[/mk_fancy_title]

Located at the pristine foothills of the scenic Western Ghats, Kalasalingam Academy of Research and Education (KARE) was established in 1984. The University caters to students from all walks of life through its undergraduate, postgraduate and doctoral programmes.

They have elaborate infrastructure spread over 320 acres. It is the first university in India to introduce a special B. Tech programme in engineering for the differently-abled (speech and hearing impaired) students.

Kalasalingam Academy achieved 4th rank in Green Metric Rankings in 2018 with their various green initiatives.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Why Solar[/mk_fancy_title]

The University Board of this progressive and conscientious university had been troubled by their high electricity bills . Thus, it unanimously decided to opt for solar energy to power their campus.

It also helps them in promoting green initiatives across the campus in various departments and inspire future generations graduating from the campus. They had approached Sunlit Future to install rooftop solar grid-tied systems on the campus in phases.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About the project[/mk_fancy_title]

So far there was 503kW solar was installed on the various buildings of the institute in three phases.

In the 1st phase of going solar, a 96.48kW rooftop solar grid-tied system was commissioned on 18 May 2017. The University decided to go for the SolarEdge power optimizers and inverters rather than traditional string inverters to have a higher solar yield and greater savings.

These products aim to increase energy output through module-level Maximum Power Point Tracking (MPPT) and also provide module-level remote monitoring via the SolarEdge monitoring web portal and mobile app as shown in the gallery below.

Highly satisfied with the quality of the installation, the solar generation and the service, Kalasalingam University approached Sunlit Future for the II nd phase of its drive for rooftop solar and commissioned another 144kW in IInd phase.

Catering to the needs of their energy and reducing the electricity bills, another 263.2 kW solar PV system was installed and commissioned later in October, 2018.

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Project Details

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Location Krishnankoil, Tamil Nadu
Owner Kalasalingam University
Capacity 503.68kW
Number of panels (330 Watts) 360
Number of panels (335 Watts) 288
Number of panels (350 Watts) 824
Type of panels Mono-crystalline
Orientation ~South at angle 10°
Structure Pre fabricated
Inverter 27.6kVA SolarEdge (7 units)

55.4kVA SolarEdge (4 units)

Average units per day 2,065 kWh
Average units per year 7,53,757 kWh
Date of commissioning (Phase I – 96.48kW) 18th May, 2017
Date of commissioning (Phase II – 144kW) 28th May, 2017
Date of commissioning (Phase III – 263.2kW) 04th October, 2018
[/mk_table][mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Generation & Savings[/mk_fancy_title]

With 503.68 kWp solar rooftop system on various buildings in Kalasalaingam university, it contributes to savings of about Rs.4,10,000/month. This system generated about 63,162 kWh/month on an average every month.

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Installation specifications

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All the three phases of the project were installed on the flat roof with the help of pre fabricated cement ballast structure made of Aluminium. This structure helps in corrossion free and long durability of the system.

Safe walkways were provided ensuring seamless maintenance of the system. Cables were routed through UPVC pipes providing safety from external factors like weather, insects etc.

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Aravind Eye Care Hospital, Puducherry

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[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About Aravind Eye Care[/mk_fancy_title]

Aravind Eye Care Hospitals chain emerged from Dr Govindappa Venkataswamy’s mission to eliminate the needless blindness of the people. Founded in Madurai, Tamil Nadu with 11 bed hospital, Aravind eye care emerged with more than 4000 beds. Aravind Eye Care treated more than 56 million people from its inception.

From Madurai, Aravind eye hospital expanded to TirupurSalemDindigulThoothukudiUdumalaipettai , Tirupati and neighboring Pondicherry.

Adding to the mission, Aravind Eye Care hospital in Puducherry had gone for a 201 kWp solar PV system on its rooftop to cater to the continuous energy consumption of the hospital in a sustainable way.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Why Solar[/mk_fancy_title]

With continuous inpatients and huge number of surgeries taking place round the clock, the hospital is contributing to huge electricity consumption. Due to which, they are incurring huge electricity bills and dependent on fossil fuels for that.

Inorder to decrease the electricity bills and contribute towards sustainable way of power generation, Aravind Eye Care hospital in Puducherry had gone for a 201 kWp solar PV system on its rooftop. 

The project was carried out in two phases with 136 kWp in Phase I and 64.6 kWp in Phase II, making it a 201.28 kWp capacity in total.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About the project[/mk_fancy_title]
System Specifications

201.28kWp solar was installed on the roof of the Aravind Eye Hospital in Puducherry in two phases.

In the 1st phase of going solar, 136kW rooftop solar grid-tied system was commissioned on 24th January 2018. The University decided to go for the SolarEdge power optimizers and inverters rather than traditional string inverters to have a higher solar yield and greater savings.

About Technology

SolarEdge products aim to increase energy output through module-level Maximum Power Point Tracking (MPPT) and also provide module-level remote monitoring via the SolarEdge monitoring web portal and mobile app as shown in the gallery below.

Highly satisfied with the quality of the installation, the solar generation and the service, Aravind Eye Care had further considered II nd phase of its drive for rooftop solar and commissioned another 64.6kW in IInd phase.

Catering to the needs of their energy and reducing the electricity bills, another 263.2 kW solar PV system was installed and commissioned later in October, 2018.

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Project Details

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Location Puducherry
Owner Aravind Eye Care
Capacity 201.28kW
Number of panels (335 Watts) 408
Number of panels (340 Watts) 190
Type of panels Mono-crystalline
Orientation ~South at angle 10°
Structure Ganges
Inverter 27.6kVA SolarEdge (6units)
Average units per day 845.4 kWh
Average units per year 3,08,562.24 kWh
Date of commissioning (Phase I – 136kW) 24th January, 2018
Date of commissioning (Phase II – 64.6kW) 26th March, 2018
[/mk_table][mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Generation & Savings[/mk_fancy_title]

With 201.28 kWp solar rooftop system on various buildings in Kalasalaingam university, it contributes to savings of about Rs.1,64,650/month on an annual average. This system generated about 25,363 kWh/month on an average every month.

 

 

Generation of Phase I & II in kWh


Savings in INR/month

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Installation specifications

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Both the phases of the project were installed on the flat roof with the help of Ganges structure. It is long lasting and durable enough to hold the modules for more than 25 years.

Safe walkways were provided ensuring seamless maintenance of the system. Cables were routed through UPVC pipes providing safety from external factors like weather, insects etc.

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Silicon Hetrojunction (HJT) Modules from Waaree

Bifacial modules are gaining the traction due to its ability to generate more kWh in limited conditions, Waaree group had come up with their new Super Silicon HJT modules. These HJT modules generate higher kWh and long-lasting.

PV module market around the world has been cost-driven. It is no wonder that the crystalline technology has been the chalk horse of the industry. Further, with the Levelized cost of electricity (LCOE) from solar plants have started breaching grid parity. The focus now is to extract maximum kWh from the plant in order to ensure the investors have maximized returns. The technology up-gradation in conjunction with module design up-gradation has played a significant role in such a shift.

Utilization of bifacial module which is capable of generating power from both sides has been gaining traction. Given the fact that enhanced energy output could be expected under the right designing considerations. However, the currently available bifacial module utilizes PERC/PERT crystalline solar cells have limited bifaciality. They are coupled with other inherent issues like LID, PID, LeTID, etc. It was hence necessary to bank upon a pragmatic solution.

Silicon Hetrojunction (HJT)

Silicon heterojunction (HJT) solar cell which has been introduced in the mid-19th century, utilizes both crystalline and thin-film technology. The cell has crystalline silicon (n-type) sandwiched between amorphous (thin film) layers of silicon on both sides. It gives the cell its bifacial nature. The monocrystalline technology in the cell has better absorption of light. Whereas, the amorphous has superior passivation (which enables high electron collection) characteristics.

The cells are thinner (~120 μm) compared to crystalline silicon cell making it slightly flexible and further also making them highly resistant to micro-cracks. The n-type silicon present in HJT does not have Boron, which makes these cells LID free. Further, the mitigation of electron from the cell which is responsible for PID is reduced to zero in HJT cells. Thanks to the presence of highly conductive oxide layer (ITO) which protects the cell electrically.

Additionally, the cell has a lower temperature coefficient (almost half of the crystalline technology-based cells). All the above factors when coupled together enables HJT based module to have lower degradation rates throughout its lifetime.

Since these cells have high bifaciality, micro-crack resistance, no LID, PID & LeTID and lower temperature coefficient it is a perfect technology for Indian conditions. Waaree Energies recently in REI-2019 launched their SUPER HJT module which utilizes HJT solar cells. Available next year, this module has already started gaining popularity among the local and international markets.

Further, with the detailed scrutiny happening for each and every module we manufacture, the end customer can rest assured that their plant would be up and running for 25+ years. It ensures more than the desired return.

India has set an ambitious target of meeting 175GW of its power demand by renewable energy in 2022. While there has been a lot of improvement from its state of cumulative capacity in the early 21st century. From that state, the sector has seen a lot of government intervention and private partnerships in order to establish and develop a solar power plant in the country.

A new plan by the government (yet in draft version) enables Public Sector Undertaking (PSU) companies to utilize and/or source green energy. The plant shall likely be 1.8 GW of capacity (similar to coal-based ultra-mega power projects (UMPPs)) and may be divided into 3 parts. The country already has a plan to develop 12GW of the power plant through the PSU route. While there have been cases of tender cancellation in various states citing various reasons, we believe that the role of government in fuelling the solar PV market growth is crucial.

The role of PSU's in enabling India to meet its renewable energy targets

Cumulative & Expected capacity addition of solar energy in India by 2022

Health benefits from Renewable Energy sources implementation estimated

Implementing renewable energy sources for meeting the enhancement in demand of the world is a no brainer now. However, it is also a well-known fact that renewable energy comes with environmental advantages too! A recent study titled “Health co-benefits of sub-national renewable energy policy in the US” reviews the health benefits of implementing renewable source in Rust Belt, US.

The study compares the impacts of Renewable Portfolio Standards (RPS) on air quality and human health. The study compares Business As Usual (BAU) RPS case along with enhanced RPS cases of +50% & +100% and finally the case of pricing CO2 emissions to no renewable energy implementation by 2030.

The study finds that the co-benefits of the BAU, RPS + 50%, and RPS + 100% scenarios correspond to co-benefits of 8¢, 12¢, and 13¢ per kWh of new renewable generation (or $94, $120, $119 per ton of CO2 reduced respectively). It further suggests that CO2 emission pricing shall further have a positive impact with a health benefit realized up to $211 per ton of CO2 reduced. The study concludes by finding that health co-benefits in the region were 35%–79% higher depending on the RPS scenario. We believe that for a country like India which has ambitious missions like 24×7 Power for all and Health for all, studies like such should be taken into consideration by the policymakers to enable implementation of right sources.

Cost benefits from implementing renewable energy sources under different scenarios in 2030 comparing to no renewables implementation (Source: Emil G Dimanchev et al 2019 Environ. Res. Lett. 14 085012)

The state of solar grid parity in China and takeaways for India

Solar PV has gained tremendous popularity around the world and China is amongst the top leader in the market. Even though the country had both supporting government policies and attractive upfront subsidies for PV which is making it a competent source of electricity in the past few years. The country (and many countries around the world) breaching the grid parity, the dynamics are poised to be changed.

A new study titled “City-level analysis of subsidy-free solar photovoltaic electricity price, profits and grid parity in China” and published in “Nature Energy” reviews the situation of China. The study analysed more than 344 prefecture-level Chinese cities and finds that all these cities without any subsidy in solar PV, can meet grid parity.

Further with the country also being a coal-powered giant and utilizing desulfurized coal (which emits lower emission) for power production; the study finds that around 22% of the cities can produce electricity which can match prices of such sources.

The subsidy cuts in recent years was a clear note that the PV industry now needs to be focused on quality products rather than on the scale. But, economies of scale has been instrumental in the case of India. Very often it is forgotten that the solar PV plant is to last for 25 years which makes quality a crucial factor of review. We believe that the utility/customers which are only utilizing quality products would be able to reap the long term benefits of solar PV.

(From left) Historical LCOE of solar PV generation in China and (right) LCOE of various generating sources (Source: Yan J., et al. City-level analysis of subsidy-free solar photovoltaic electricity price, profits and grid parity in China. https://doi.org/10.1038/s41560-019-0441-z)

Source: Waaree Group

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Maximum Power Point Tracking – MPPT

What is MPPT

Maximum Power Point Tracking (MPPT), a simple digital electronic DC to DC converter. It optimizes to match between the Photovoltaic (PV) panels and utility grid (ESCOM) or battery. Converts higher DC output of modules according to the need of the grid or the battery. 

MPPT block diagram

Block Diagram of MPPT Photo Voltaic system

Image Source 

Why is it needed

Solar modules are cool devices, harnesses photons and converts into usable DC supply. Assuming we don’t have MPPT.

Let’s consider a 300 Watt solar module and 24-volt battery with a charge of 10 amps. It equals to 240 Watts. A loss of 60 Watts has occurred when compared with modules generation of 300 Watt. 60 Watt will be a loss with no generation due to mismatch with the battery. 

MPPT technique is used to avoid such losses and generate the maximum possible at any given time, in the optimizers and inverters.

Working of MPPT

This MPPT compares the output of the module and the voltage of the utility grid or the battery. MPPT looks for the best voltage for the utility grid or battery and brings out the maximum current from the power. Power (W) = Voltage (V) X Current (I). There are various MPPT techniques. Most of these techniques are 95-97% efficient.

Some of the MPPT techniques used are:

  1. Perturbation and observation (P&O) technique 
  2. The incremental conductance (Inc Cond) technique 
  3. Ripple correlation technique 
  4. Short circuit current (SCC) technique 
  5. Open circuit voltage (OCV) technique

In a case, the solar panel is producing 300 Watts and connected to 24 Volt battery, MPPT takes in the voltage and Current panel is producing say 40 Volt, 9.5 Amps and converts it into 24 volts, 15.83 Amps not letting incur any loss. Happy all.

With respect to the usage of MPPT in DC optimizer technology and string inverter technology, even though the technology remains the same the way it is used varies. 

MPPT in String inverters

Based on the inverter capacity solar modules are connected in series. Each string is connected to the inverter. Here series of modules are connected to the inverter with inbuilt MPPT component in it. Each series is called a String. Here MPPT optimizes at the string level. In a panel of 72 cells, all the cells are connected in series. 

Series means connecting positive of the first cell to the negative of the second cell and so on. Negative terminal from the first cell and positive terminal of the last cell in the panel are pulled from the panel allowing to connect to another module. When the positive output of the first panel is connected to the negative of the second panel and so on it connects all the modules in series forming a string. 

Once the output is passed through the MPPT it is inverted into the AC output. Usable power in the building.

With all the modules in series, if there is an issue in a generation it affects the generation of complete string. Possible generation issue could be a bird dropping or shadow on the panel. Generation of all the modules will be completely dependent on least generating panel, compromising on the generation of the system.

MPPT in Power optimizers

In the case of power optimizers technology, each module is connected with a DC power optimizer. Here MPPT technique is provided at module level not letting the generation of the system go in vain. Possibility of external factors like bird dropping and shadow on one single panel are few of them. Each panel will be having independent MPPT technique generating power irrespective of the adjacent module. 

All the power optimizers after optimising the power from each module are connected in series and connected to inverter through a junction box. Each module is independent of each other.

This kind of technology helps better in roofs in various directions, shadows etc. One optimizer can be connected to two modules reducing the need to a number of optimizers but having the benefit of maximum generation. 

String Vs Power Optimizers (MPPT)

Technology remains the same in both cases. In string inverters, it is at a string level whereas in case of optimizers it is at the panel level. In optimizer technology, it is also possible to monitor the generation at the panel level. This helps in the reduction of the maintenance work saving time, money and enhancing the generation bringing down the diagnosis of the system to the module level. With module-level MPPT it prevents loss due to module mismatch.

Conclusion

Maximum Power Point Technique (MPPT) as the name says, helps in generating optimal power within the constraints of a string level of module level. This technique is used not just in photovoltaics but also in Wind power in harnessing maximum possible power at that instance.

References:

Waaree   Wikipedia  SolarEdge Wiki  Solar Electric  SolarEdge

 

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