Captive Solar PV Systems – L&T’s Experience

(This interview with L&T was done by Madhavan Nampoothiri, Founder & Director of RESolve Energy Consultants on 19 March2011 when he was working for Energy Alternatives India(EAI). The original post can be found here.)
It is a well known fact that India’s electricity generation is insufficient relative to the demand the country has. In 2009-10, India’s electricity deficit was approximately 10% (84 TWh) and the corresponding peak load deficit is 12.7% (over 15 GW). India’s frequent electricity shortages are estimated to have cost the Indian economy 6% of gross domestic product (GDP) in financial year 2007–2008.
One report states that there is an approximately 7% decrease in the turnovers of Indian companies due to power cuts. As a consequence, most factories, businesses, and private customers have set up their own power generation capacities in the form of captive power plants or diesel generators in order to ensure their power supply. This provides an attractive opportunity for renewable energy solutions; they compete not with power produced relatively cheaply by large coal plants but with much more expensive diesel back-up generators.
With the constant increase in the crude oil prices and the gradual reduction in the prices of Solar PV systems, replacement of Diesel Generators with Solar PV systems is increasingly becoming an attractive option.
Larsen and Toubro (L&T) was one of the first Indian companies to understand this. The company commissioned a 406.8 kW grid connected PV system for its captive usage in its Manapakkam, Chennai campus in December 2009. L&T provided Energy Alternatives India (EAI) an opportunity to visit the campus and to learn more about the PV system. In this discussion with EAI, Mr. Shaji John, Chief – Solar Initiatives, L&T, explains the system in detail and highlights some of L&T’s experiences in constructing and managing the Rooftop Solar PV system.
EAI : Could you please share with us the reasons for setting up this captive solar PV plant?
Shaji John: L&T’s objectives of commissioning the plant are
a. Take positive steps to create “Green Power” as a CSR activity and contribute towards the preservation of Mother Earth’s Resources.
b. Need for a reliable back-up power for meeting emergency needs
c. To reduce dependency on DG set and diesel oil
d. For moving towards a smart micro grid (for reliable power and energy saving)
EAI: What are the key features of the solar PV system at your campus?
Shaji John: The current installed capacity (Phase 1) of the system is 406.8 KW. Work is underway to increase it to 1 MW in another 3-4 months. The first part of Phase 1 was completed in December 2009. The 406.8 kW is distributed among 4 buildings within the campus. All buildings except one have an East-West facing unique wave mounting structure for arrays. One building has a South facing mounting structure. The campus load is currently 7 MW and is expected to increase to 13 MW soon. In addition to this, we are also building a 100 kW standalone PV system in Delhi with battery storage of 2 days.
EAI : What was the financing model? What were the government subsidies you availed from the government?
Shaji John :The cost of the Phase 1 was Rs. 10 Crore which was fully financed by L&T internal funds. The project got the 80% Accelerated depreciation benefit as per the guidelines of the Government of India(GoI).
EAI : You mentioned earlier that the project helps you reduce the diesel consumption and reduced Carbon dioxide(Co2) emissions. Could you elaborate more on that?
Shaji John :Both L&T and the environment are benefiting from this project. The benefits to the company are

  • The system will produce approximately 556,000 units of electricity per annum.
  • This will result in annual saving of Rs. 75 to 100 L in the initial years, though savings from costly diesel power.
  • It is expected that the payback will be within 7 years.

The benefits to the environment are as follows.

  • Carbon dioxide cut effect – 370000 kg-c/ year
  • Diesel savings – 136000 litres/year
  • Co2 absorption effect on forest – 1113000 square metres

EAI: We understand that Japan’s SHARP played a key role in the project. What was their contribution to the project?
Shaji John: SHARP played a crucial role in the project. For instance, SHARP designed the Solar PV Power Generating System for L&T including,

  • Solar irradiation study
  • Shading analysis of roof-tops
  • Solar PV array design
  • Array layout detailing
  • Mounting structure design
  • Design of module, inverter and monitoring system

SHARP also supplied to L&T the Solar PV Power Generating System including,

  • Solar Modules(mono-crystalline PV cells of 15.7% efficiency)
  • Inverters (Grid connected with an efficiency of more than 96%)
  • Monitoring System
  • Mounting Structures

L&T has carried out the following:

  • Finalizing the scheme to integrate the solar power system to existing distribution system
  • Structural analysis of roofs
  • Design & detailing of foundation/footings for the solar arrays
  • Preparation of protection scheme for the total system
  • Preparation of synchronization scheme (involving solar system, grid & DG sets)
  • Design of earthing & lightning protection system
  • Design of cabling system including cable routing, cable schedule, cable identification system etc.

L&T carried out the sourcing of Balance of System, Civil Works and Installation of the entire system. Testing & Commissioning was carried out under specialist supervision of SHARP.
EAI: How would you rate the system performance?
Shaji John : We are happy to observe that the actual system performance is matching the design expectations. The energy output was 4% lower than forecast. One of the reasons for this could be the above-average rains in Chennai in 2010 which resulted in lesser number of sunny days in the year and reduced solar insolation.
EAI : You mentioned earlier that you went for both the traditional south facing panel mounting and the East-West wave mounting for panels. Based on their performances, which one do you rate better?

East-West facing Wave Mounting Structure
Shaji John: The East- West facing structure is advantageous because
a.       more panels can be installed in the same area(more MW/acre) and
b.      more energy is generated per MW installation
We have observed that the E-W facing modules’ output is upto 9% higher (in peak summer) than the South facing installations, and on an average, the output is 5% more.
EAI:  One of the most attractive features of Solar PV systems is their low operations and maintenance (O&M) costs. What is your opinion on that?
Shaji John: The O&M cost is negligible for the plant. The panels are cleaned every week, but we have found that cleaning every 15 days is economically optimal for this location. We use plain water and there is no need for special chemicals for panel cleaning. We are planning to use a sprinkler system to ensure uniform and regular cleaning and also for cooling the panels(on an average, there is a drop of 0.4% module efficiency for every 1 Deg C increase in module temperature. The modules are rated at Standard Test Condition(STC) which is at 25 Deg C)
EAI: What are L&T’s R&D initiatives and future expansion plans?
Shaji John: L&T is sponsoring the Build India Scholarships for IIT Madras and Delhi for M.Tech study. Some of these students are studying the performance of the rooftop and will help us improve the design.
In the 600 kW addition being carried out at the Manapakkam campus, L&T  is trying different technologies like
o   CdTE Thin film
o   CIGS Thin film
o   Concentrating PV
o   Hybrid PV
o   Trackers
o   BIPV
o   Unique system configuration
L&T is executing 25 MW projects in Gujarat and is also in the final stages of closing deals for EPC of Solar PV projects(several MWs) all over India.
EAI : Thank you very much for your time and for the opportunity to visit the campus.

Shaji John:My pleasure.

EAI thanks Mr. V S Ramana, General Manager & Head – Corporate Communications – L&T – ECC, for facilitating the visit to the L&T campus. EAI also thanks Mr. Sankaranarayanan M, Senior Engineer-Electrical, Solar Initiatives at L&T for showing us around the captive solar PV plant and also patiently answering our questions.
For more details and enquiries related to the solar PV plant, please contact Mr. V. S. Ramana

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