Solar Chanakya

24th August 2018

Factories should go for the Solar Net Metering but there are pitfalls

Discoms in almost all the states provide the Net Metering facility by which the consumers can store the excess energy generated from the roof top solar plant with the Discom Grid and can use it in later hours.

During the Sun hours, when the load (in KW) of the factory or the commercial building is less than the roof top solar generation for any 15-minute block interval, the excess solar energy goes back to the Grid. During evening hours when the load is more and there is hardly any solar generation, then the stored solar energy is used back by the consumer from the Grid.

The accounting of the roof top solar energy is done on a monthly basis.

  • At the end of each month, the solar energy is set off against the energy consumed by the factory or the Plant through a bi-directional meter installed by the Discom at the Consumer premises.
  • If there is any excess solar energy which is not used during the month, it is taken forward to the next month in which the consumer can use the same.
  • However, if there is unused solar energy left in March (end of Financial Year), then it will lapse as per the policy in Haryana while it will be paid at Rs 2.0 /kWh in Uttar Pradesh. Similar policies exist in other states also including Delhi, Rajasthan and Punjab.

  • The table below shows the energy accounting and settlement for 1 month (April) under Net Metering for a 100 KW solar system in a typical factory set up with a contract demand of 100 KW.

    Day Energy Consumed (kWh) Solar Generation) (kWh) Banked Energy
    1 614 479 -
    2 15 478 463
    3 478 491 13
    4 645 444 -
    5 633 450 -
    6 701 441 -
    7 612 520 -
    8 426 523 97
    9 12 541 529
    10 459 497 38
    11 723 478 -
    12 578 483 -
    13 623 429 -
    14 701 501 -
    15 641 504 -
    16 12 502 490
    17 423 476 53
    18 530 472 -
    19 481 451 -
    20 392 439 47
    21 543 472 -
    22 605 462 -
    23 12 495 483
    24 452 523 71
    25 545 547 2
    26 393 482 89
    27 479 477 -
    28 625 461 -
    29 521 441 -
    30 12 478 466
    April 13,886 14,437 551

    For certain days in April month, the energy is getting banked or stored with the Discom. At the end of month, solar has generated excess of 551 kWh or units which will be taken forward to the month of May.

    Table below shows monthly settlements for the full year of solar energy.

    Month Energy Consumed(kWh) - (1) Solar Generation(kWh) - (2) (2)-(1) (kWh) Cumulative Energy banked (kWh)
    Apr 13,886 14,437 551551
    May 15,672 15,432 (240) 311
    Jun 14,521 13,441 (1,080) -
    July 12,673 11,699 (974) -
    Aug 11,128 10,952 (176) -
    Sep 11,893 11,699 (194) -
    Oct 12,321 11,450 (871) -
    Nov 11,009 9,210 (1,799) -
    Dec 10,121 8,463 (1,658) -
    Jan 10,344 8,712 (1,632) -
    Feb 11,236 11,201 (35) -
    Mar 11,037 13,690 2,653 2,653

    So, there is excess solar generation in the months of April and March. However, the excess generation of April month is utilized in future months during the settlement year. But the excess solar generation in month of March will lapse in spite of Net Metering facility.

    Especially for seasonal industries that has lean period during winter months, the coincidence of the settlement year with the financial year is a problem. For example, the potato cold storages (aloo godowns) has this typical problem as they hit a off season from October to February when their load dips significantly.


    23rdAugust 2018

    Factories/Industries ‒ How much solar (in KW) can be installed at the roof?

    Solar installmodular in nature and the factories, cold storages, warehouses, commercial buildings, Malls etc can plan to install solar panels (KW) as per their requirements.


    To understand the solar plant sizing, let us assume a hypothetical case where in an industry located in Kundali, Sonipat (Haryana), and
    • has a roof made of metal shed and has an area of 3000sqmeters,
    • has a contract load of 1,500 KW,
    • has an average monthly electricity consumption of 70,000 units or kWh
    • is connected to a distribution transformer of 2,000KVA.

    Following factors should be taken into consideration while designing the solar system for your roof -
    1. Roof Size determines the maximum capacity of the solar plant that can be installed:
      1. Each panel has an area size of roughly 2 sq meter (1 meter X 2 meter) with a capacity of around 325 watts. So broadly, 3 panels can make 1 KW of solar installation which implies 1 KW can be installed in 6 sq meter of roof areain ideal conditions.
      2. However, space is required to be left between the panel rows to avoid shadow on the panels. As the panel structures are raised to provide inclination and thus the better exposure to sunlight, the shadow free area further decreases.
      3. Typically, on concrete roofs, 10 sq meter would be a good estimate for 1 KW of solar panels. For inclined metal sheds and asbestos roofs, the area required to install 1 KW of solar panels would decrease based on the direction of the shed. A South facing shed can accommodate more solar panels than the one facing north.
      4. For the roof in the above example, a solar plant of 300-350 KW (=3000 /10) can be installed based on the size and inclination of roof.

    2. Solar Plant size in KWs cannot be more than the Contract Load. In Haryana, Delhi, Uttar Pradesh, Rajasthan and other states, the size of solar plant is constraint by the Contract Load of the Building as per the Discom’s regulations. So, in this case, the maximum size of the solar plant that can be installed on the roof is 1500 KW.

    3. Electricity bill is an important factor to determine the size of the plant. As the Net Metering facility is available in all the states in India, the annual electricity consumption of the industrial unit, factory, warehouse or the building should be considered while sizing the solar plant.
      1. In Haryana, UP and Delhi, consumers should consider a solar generation of 1400 kWh per KW of solar panels with 5 percent variation in the first year of the plant’s installation.
      2. In the above example, the factory has average monthly consumption of 70,000 units or annual consumption of 8,40,000 units (=70,000 X 12).
      3. To reduce the variable part of the electricity bill to zero, the industrial unit should install 600 KW (=8,40,000 / 1,400) of solar panels on the roof or within the campus.

    4. Availability of Distribution Transformer capacity is important for the solar plant.

    All the state regulators and Discoms have specified the maximum capacity of solar plants that can be connected to a Distribution transformer. For example, Haryana allows only 15% of the distribution transformer capacity that can be used by the solar plant while Delhi allows 20% of the transformer capacity and Uttar Pradesh allows 25% of transformer capacity.

    In the example above, the transformer has a capacity of 2000 KVA.So, a maximum of 300 KW (=15% of 2000) of solar panels can be connected to this transformer.

    Discoms may consider the distribution transformer located in the premises of the industry also as the distribution transformer in spite of the transformer being owned by the consumer. Therefore, it is important to check with the Discom for the maximum solar capacity that can be installed and Net Metered with the Distribution Transformer.

    So, going by the above 4 factors, namely (1) Roof Size (2) Contract Load (3) Electricity Bill (4) Distribution Transformer capacity, the Kundali consumer in this example can plan for a solar plant of only 300 KW. In this case, the size of distribution transformer and the roof size are constraining factors.


    20th August 2018

    What should be installed as part of Rooftop Solar System at Factories?

    Apart from the solar panels, there are a number of components that make the solar system to be installed at factories and industries.

    Solar Inverters are the most important component after the solar panels which need to be properly selected and installed for rooftop solar systems. Most industries in Delhi and NCR (Faridabad, Kundali, Panipat, Sonipat, Ghaziabad, Manesar, Noida, Neemrana etc) have opted for strong brand names for the inverters that would include ABB, Huawei, SMA, Delta, Waaree etc. The Inverters are available with a warranty of 5 years though the extended warranty of another 5 years can be available by paying a bit extra. Quality of Inverters matter significantly in generating higher power from the same level of solar generation provided by the Solar panels. More number of MPPTs (Maximum Power Point Tracker) generally help to increase the reliability of the solar system and provide better generation.

    The structure for mounting the Solar Panels is an important part of the system. The strength of the structure should be such that they can bear a wind speed of 180 kms per hour. Typically, the structure should be designed and tested on the design software like STAAD.PRO to check their suitability for the given height and weight. As the height of structure increases, the wind pressure increases. Recently in places like Alwar, many solar panels flew away due to poor quality of structure. Consumers should be careful in selecting the structure as the flying panels can not only damage the system but also can cause serious accidents.

    DC cables should be used for interconnecting the solar panels. Practices have been noticed where in the vendors tend to connect the panels by the AC cables which increases the generation losses. AC cables are cheaper and can help to reduce the capital cost in short term but will be expensive due to mounting losses. Ideally the DC cables should only be utilized to connect the solar panels to the Inverters.

    AC cables of right size should be used to connect the Inverters to the AC junction boxes or the LT Panel of Discom. Sizing of the cable is important to reduce the losses.

    Earthing of the system is important for the safe operations. Earthing strip and wires need to be connected to all the key electrical components.

    Lightening Arrestors (LA) are required to safeguard the system against any weather lightening and should be installed based on the system size.

    Remote monitoring of the generation should be provided to continuously check the health of system.

    Water piping system should ideally be designed to provide the water supply for periodic cleaning of the panels which will help to increase the generation.


    19th August 2018

    Can metal sheds and Asbestos roofs accommodate Solar System?

    Factories in Delhi and NCR regions have a variety of roofs ranging from flat concrete roofs, metal sheds which are mostly inclined and even the asbestos sheets laid over the top.

    The Solar Plant can be installed on any roof that has sufficient strength.

    On flat concrete roofs, it is quite easy to lay the solar panels. The civil foundations need to be laid in a way that the water should not seep into the roof. Over the foundations, the structure made up of hot dipped galvanized steel needs to be built of sufficient strength. The structure should preferably give a tilt of 20 degree around in Delhi and NCR to get the best solar irradiation. The panels should face to the South side to the extent possible.

    The Metal sheds can be facing east-west or north-south. If the metal structure has sufficient strength, the solar panels can be easily laid. The solar panel structure should be such that it is light and strong enough to hold panels. In typical sheds, the purlins and associated structures are designed to take weights of more than 100 kg per square meter. Solar plant will weight around 20-25 kgs per square meter, hence the weight of plant is never a problem unless the purlins are not strong enough.



    However, the factory owners should be careful while allowing the puncture in the roof. Water leakages would tend to happen from the punctured holes in the roof. Over time, the screws put on these punctured roofs will have movement due to the pressure from strong winds and the puncture size will increase. So, while installing panels or building pathways or side rails, these punctures need to be reduced to the maximum.

    Similarly, panels can be installed on asbestos sheets. The old sheets need to be replaced in such installations. Typical asbestos sheet has a life of 10 years. Again, it is not the sheet but the purlin structure that has to take the weight of the solar panels and structures. Asbestos sheets should have enough strength that the man power for plant installation can freely walk and do their work.


    18th August 2018

    Industries/Factories can run all Heavy Machines and Motors on Solar System

    In past, the solar systems used to be connected with the batteries that used to store the power before it was supplied to the machines and. Appliances. These solar systems were called as the off grid solar systems and were typically used as the backup for limited purposes.

    However, with the technology break through and manifold increase in the reliability of electricity supply from the Discoms, the new age solar systems directly connect to the Discoms panel and Energy Meters via certain protections and relays. No batteries are required for these On Grid Solar systems as the much-required stability to match up the intermittent nature of solar power, is provided by the Discom power. Hence, the Discom acts as the large size battery for the On Grid Solar plants.

    So, the solar works only when the power is available from Discom or from the DG sets.

    These On-Grid systems generate power during sunny hours which are on average 1400 hours in an year in Delhi and NCR (Gurgaon, Faridabad, Ghaziabad, Noida etc) with few hours plus or minus. So out of 8760 hours in a year, the solar is available for around 16% of time assuming the full capacity of the solar plant. The electricity units generated during the solar hours help to reduce the electricity bill of the factory while also helping the Discom to reduce the peak loads in its network. Hence, the Discoms also support the setting up of rooftop solar systems in its area through Net Metering and Banking facility.

    As the solar system runs in conjunction with the Discom power or Grid, the solar power can run virtually all the machines and motors in the factory. Hence, the solar systems have been adopted by heavy load industries including steel, automobiles, textile, pharma, chemicals, furniture, cold storages etc. Think of solar supply as a small pipe connected to a many times large pipe (Discoms’ supply) while feeding the electricity demand of the machines.

    As Solar System is never supplying power directly to heavy machine and equipment, there is absolutely no risk to them. Such solar systems are cost effective also as they do not have expensive storage and battery systems.


    17th August 2018

    Industries can run Rooftop Solar Plant with Diesel Generators (DG) also

    Many industries in Delhi/NCR (Kundali, Sonipat, Faridabad, Bahudargarh, Manesar, Bawal, Ghaziabad, Greater Noida etc) have to still depend on the Diesel Generator sets for running factories for few hours daily. What happens if the discom supply is disrupted during the sunny hours when the sun is still out generating the power?

    Grid tied solar plants or On-grid solar systems will run when the Discom power is available as the solar inverters have in built feature which commands the solar system to generate power when it can sense that the supply is available from other sources. Such a feature is built in solar inverters as the solar power is an intermittent source of electricity supply which provides variable output depending on the solar intensity at that moment. Hence if suddenly the clouds cover the sun, the solar generation will dip making the system unstable.

    Therefore, solar has to always run in conjunction with any other dependable and stable source of supply like Discom power, DG power or the batteries.

    As the batteries are quite expensive and need to be replaced periodically, most factories depend on the DGs for the back up power. Solar can be connected to the DG panel directly as it is connected to the LT panel of the Discom supply in the factories. Certain protections require to be built in based on the DG sizing however. Also, the factory load that can be served by solar should never be more than the DG supply which means that the primary supply source will always remain the DG.

    So, the size of solar plant cannot be more than that of the DG size as the solar alone cannot take the factory or plant’s load.

    Solar will help to reduce the diesel consumption during the DG hours as the DG will run at lower loads and even idle loads depending on the system design. For the system to work smoothly, if there are multiple DGs, they should be synchronized (manually or automatically) before they are put in sync with the rooftop solar system.


    16th August 2018

    Solar Systems and Plants for Small and Medium Enterprises

    The industries should opt for rooftop solar today as there are a number of commercial advantages apart from environmental benefits. Industries can opt for solar system size ranging from few KWs to few MWs.

    Typically, an on grid solar system is preferable which directly connects to the LT panel of the Discom Meter.

    • Power generated from solar will directly reduce the electricity bill.
    • Any surplus power generated at any time will be fed back to the Grid and stored with the Discom.
    • These solar plants run through Net Metering facility provided by the Discom in which the billing and settlement happens at the end of each month. Any surplus power generated from solar plant will be carried forward to the next month. However, if there is any solar plant left unused at the end of the financial year, it will typically lapse.
    • Having said that there are very slim chances that the solar power will lapse as the power generated from solar plant will not be more than 30% of the electricity bill for any industry.

    As the solar system directly connects to the LT panel, the solar power gets used to run all the heavy machineries, air conditioners, motor loads etc. No batteries are used in such On-Grid systems which means that the solar system will only run when the Discom power is available.

    There are no subsides available for setting up solar system in industries now which were there till 2016 as the cost of solar was high during that time. However, now the solar prices have become very affordable. For example, for the industries located in and nearby Delhi/National Capital Region (NCR) where the solar radiation levels are good, the pay backs of solar will be typically in 3-4 years.

    Hence, many industries located in Okhla, Noida, Gurgaon, Faridbad, Ghaziabad, Kundali, Manesar, Neemrana, Palwal, Bawal, Bahadurgarh etc have opted for the rooftop solar plants.

    Also, the Accelerated Depreciation (AD) benefit is available for installing solar plants. Factories can depreciate 40% of the solar plant capital cost in the 1st year itself. So, for a company paying 34% income tax, the cost of solar plant reduces by 13.6% in the very first year itself. 40% AD is available on the reducing balance in the next subsequent years.


    15th August 2018

    Solar Chankaya

    Like Pandit Chanakya, who showed us the path to live a happy, virtuous and content life, the Solar Chanakya is aimed at showing the path to help build solar societies around us which will be independent for their energy needs and will be based on sustainable and green development.

    Finally, the solar has arrived due to technology break through and setting up of large production capacities across the World led by China and Europe. The crashing prices of solar cells have also led to the innovation in balance parts of the systems including the inverters which have further helped to increase the affordability of solar systems everywhere.

    Governments and Regulators also joined hands to provide a conducive framework to support installations of solar systems across industries, institutions, commercial buildings and houses. Facilities like Net metering, banking, solar credits and timely subsidies were announced by them to make the solar attractive for everyone.

    Now the onus is on us ‒ the Consumer to make the transition to Solar Energy. Many have already taken this step in the right direction to contribute through solar energy and many more are joining the movement to create a solar world. Yes, no revolution comes cheap and without price. Extra efforts and contributions are to be made to create sustainable solar societies.

    Solar Chanakya aims to help everyone who wishes to join the solar world and will like to install solar system. .

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