2 MV Pictures

INDIA'S FIRST MW LEVEL SOLAR PV POWER PLANT –

MY DREAM PROJECT

                                                                                    S.P.Gon Chaudhuri

Managing Director, WBGEDCL

Energy is a key input to economic growth and for improved quality of life.  Continued access to unrestricted supplies of energy is of major importance to all economics India's Energy Policy till the end of the 1980s was mainly based on availability of indigenous resources.  Coal was by far the largest source of energy.  Things have changed since then Coal and lignites share in the commercial energy has come down further.  The reason being non-availability of good quality coal and also environmental issues.   In order to fill up the gap between demand and supply Renewable Energy has to play a major role in India.  Out of many forms of Renewable Energy Sources Solar Energy appears to be most attractive.  The world over installation of PV cells and modules has been growing at an average rate of 35 percent since 1998. 

There are two routes for converting Solar Energy into electricity.  One route is by collecting Solar Energy as heat through concentrating Solar Collectors and converting this heat into electricity using a typical thermal power generating unit.  This is known as solar thermal power generation.  The other route is by using Solar cells to convert the radiation from the Sun directly to electricity.  This is called Solar Photovoltaic power generation. Sunlight can be converted to electricity due to the photovoltaic effect discovered in 1839 by Edmund Becquerel a French scientist.  Sunlight is composed of photons or packets of energy.  This photon contains various amount of energy corresponding to the different wave lengths of light. When photos strike solar cell electricity is generated in the external circuit. Historically, it has been about 50 years since the first operational silicon solar cell was demonstrated.  However, the last 20 years have seen large improvements in the technology, with the best confirmed cell efficiency being over 24.7%( laboratory level). The commercial crystalline cells having efficiency around 20% is now available in the market.  Manufacturers claim that thin film module can be produced as low as 1 US$/Wp by the year 2011. However, wafer based crystalline silicon solar cells have dominated the solar PV industry since the advent of the Solar era.  Crystalline Silicon is widely available, reliable and well understood.  In the previous decades the Solar Industry grew by almost 50% annually.  Crystalline Silicon has had about 90% of the total volume in the market.

 Photovoltaic Power System Types.

Terrestrial photovoltaic systems can be categorized into three application types: Stand alone, hybrid and grid connected.

The stand alone system generally involves batteries and is used in remote areas which have no access to a public utility grid.  A hybrid system includes a PV array one or more auxiliary power sources ---- wind or diesel generator and one or more batteries.  Although it requires a more complex controller than the stand alone or the grid connected systems, its overall reliability is superior to the other two systems.

In grid connected system, the utility network acts as an infinite energy sink and accepts all available power from the PV system. The simplest grid connected system has a PV array and an inverter.  For high voltage grid connected system (greater than 230 or 415 volts), transformers and appropriate power switching and protection devices are essential.   However, the grid interface criteria vary with the utility companies and not yet been standardized nationally.  Most of the inverters now being seen for grid connected applications incorporate peak power tracking capability.  That is the inverter controls the PV array out put to maintain operation at its maximum power point which changes rapidly with variation in Solar intensity and module temperature.

Solar PV in India.

The demand for power in India and consequently, the demand supply gap, is growing over the years. Solar PV has the potential to be deployed in some key segments like grid connected power generation, decentralized distributed generation, roof based solar PV.  The total Solar energy potential in India is huge and this may contribute significantly in bridging the gap between supply and demand  Today, India experiences an average energy (electricity) shortage of 9.6% and a peak shortage of about 14%.  Peak shortage is highest in the western and northern region of India where the availability of Solar radiation is also comparatively high.  To meet the growing demand and shortage of energy, the generation capacity needs to be doubled in 10 years from the current level of 1,45,000 MW (approximately).  The country needs to deliver a sustained growth of 8-9% through 2031-32 and meet the energy needs of its citizens.  India will need about 800 GW of power by the year 2031-32 according to the planning Commission.  The country at best can generate 500,000 MW of Power from coal and 100,000 MW of power from Hydro.  The quality of Indian coal is not good. Large hydro power stations are seriously threatened by climate related issues. The contribution of nuclear power in the energy basket of the country may not be more than 50,000 MW by the year 2031 due to various techno-political issues.  There will be a net shortfall of power to the extent of 1,50,000 MW even after considering other sources like natural gas etc.  This gap may be filled up by various forms of Renewable Energy Sources amongst which Solar energy appears to be most prospective.  World wide Solar installation has crossed 16 GW.  Unfortunately due to absence of lucrative policies Indian contribution in this major event is insignificant.

India has done impressive work in the area of stand alone type Solar photovoltaic.  The Ministry of New and Renewable Energy launched a country wide Solar photovoltaic programme almost two decades ago.  Under this programme, almost one million Solar PV based systems have been installed including 5.85 lakhs of solar Lanterns, 3.64 lakhs Solar Home Lighting Systems, 69,500 street lighting system, 7,068 Solar water pumps and few small Solar PV Power Plants. Though number wise installed Solar PV system in India is impressive however, MW wise the installed capacity of Solar PV is very low in India.  The installed capacity of Solar PV can only be increased significantly through installation of MW level grid connected Solar projects. 

The initiative towards setting up of MW level grid connected Solar project was first officially discussed in the country in a workshop held at Kolkata in  the year 2006 where some state Electricity regulators were requested to declare feed in tariff for grid connected Solar PV power plant. Secretary MNRE, Government of India also argued in favour of the idea.  The high cost of Solar PV equipment results in a higher cost of generation, which restricted the growth of power generation through Solar PV. However, finally MNRE, Government of India decided to support large sized grid interactive Solar Power generation projects. The ministry announced a generation Based Incentive (GBI).

Scheme to support a total capacity of 50 MWp from 2007 to 2012.  The state of Punjab and the state of West Bengal first declared the feed in tariff in the country.  The State of West Bengal went one step ahead by declaring feed in tariff for Roof Top Solar PV system also.

The salient features of GBI schemes are:

a)                  Solar PV Power generation plants of a minimum installed capacity of 1 MWp per plant; either a single unit or modular units at a single location will be eligible for generation based incentive

b)                  GBI is available only for a maximum cumulative capacity of 10MWp of grid interactive Solar PV Power generation projects in a state.

c)                  The incentive scheme is applicable only to those projects that are connected to the grid.

d)                  The GBI scheme guarantees an overall tariff of Rs.15 per KWh which is the sum of GBI plus the preferential tariff offered by the state utility.

e)                  Any project that is commissioned after 31^st December, 2009 would be eligible for a maximum incentive with a 5% reduction and ceiling of Rs.11-40 per KWh.

2 MW Asansol Solar PV grid connected Power Plant.

The power plant was conceived under the above mentioned scheme in February, 2008 in a meeting where Secretary, MNRE, Managing Director of DPSC Ltd. and the author of this article was present.  Interestingly DPSC offered the land free of cost in an old coal based Power Plant site.  The 6 MW old power plant was declared as abundant in the year 1997.

It was difficult for an Indian to make the Project Report since there was no past experience.  However, with great difficulties that project proposal was prepared and financial closure was done with the Power Finance Corporation.  It was really a bold step for PFC to come forward to provide fund for the project at an interest rate of 9%. 

A number of clearances were obtained thereafter and finally the contract was awarded to a Hyderabad based Company who started executing the Project in collaboration with a German Company and under the overall supervision of West Bengal Green Energy Development Corporation.   The Plant is now ready for export of power to the grid.

The Asansol Project is unique in many ways.

• This is the first grid tied MW level Solar PV Project in the country.
• The Project for the first time used indigenous 250 KW level Power conditioning units in the country.
• Multifunctional MMS (Module Mounting structure) fixing machine was used for the first time in the country.
• This is first Solar Mega Project in the world which replaced a small coal based thermal power plant.

Salient Features of the Power Plant

Site Information:

The Plant is installed at Jamuria (Sheebpur thermal power plant site) Asansol, West Bengal, India. Its co-ordinates are:

Latitude                                    : 23.7^o N

Longitude                                 : 87.1^o E

Altitude                                    : 364 m above MSL

The site is about 210 Km from Kolkata, the major metro city in the Eastern India.  The site is approachable by road and rail.

Site Constraints:

There are some coal mines in the nearby area which may cause deposition of dust on the modules. In such case the modules will require frequent cleaning.

Plant Architecture and Layout:

                                     Rail Line

Solar Radiation and Climatic Conditions:

Insolation, global horizontal:

• Annual                                      :           1900 kWh/m²
• Daily average                         :            5.4 kWh/m²
• Best performance month        : October/November and February/March
• Ambient Temperature               :           44^o C maximum

                                                      :           8^oC minimum

• Wind speed                              :           120 kmph (maximum)

System Description:

The PV arrays have been installed in the ash pond area of an old thermal power plant named as Sheebpur Thermal Power Plant. The arrays have been installed in a plot of land measuring 5 acres.  There are 14 rows of PV panels.  The panels face truly south. In the lay out and design of the module mounting structure adequate care has been taken in regard to wind speed and soil condition. The MMS are made of I-channel and wooden beam.

All the sides of the PV array are free from any structure and there is hardly any chance for construction activities in future. So there is no threat of shadow on the module yard in future.  33 kV grid substation is only 200m away from the SPV power plant.

Major components and their Features:

Solar Array

Rated Peak Power                   : 1250 kW (1^st Phase)

Array Tilt Angle                                                :  20^o

Bus voltage                                                       : 670 -750 V

Number of strings                                             : 191

Total Number of Modules                                 : 4600

Number of Modules per string              : 24

Module  Manufacturer                          : Titan Energy Systems Limited, Hyderabad                    

Module Rating                                      : 240/225 W

Number of Cells per Module                            : 60

Module weight (Av)                                          : 18.5 kg

Module dimension                                            : 1667mm x 994mm

Module area                                                     : 1656998mm²

Solar cell Type                                     : Crystalline

Cables                                                              : All DC cables are copper cable with XLPE Insulation and cables are directly laid into the ground. AC cables are Aluminium/copper conductor XLPE.  HV cables are XLPE type

Inverter (PCU):

Rated Power                                                    : 250 kW each

Number of Inverters                                         : 5

Manufacturer                                                    : Optimal Power Synergy Systems Ltd., Salt Lake, Kolkata

Input Voltage Range                                         : 450 – 800 VDC

Output Voltage Range                                      : 400 VAC (compatible with grid voltage)

Frequency                                                        : 50 Hz ± 2.5%

Efficiency at Full load                                        :  93%

Data acquisition system                         : SCADA in built in Inverter (PCU)

LT panel                                                         : 2000 Amp with 5 incoming and 1 out going with ACB  on the outgoing feeder.

11 kV Circuit Breaker                                      :  Indoor type

Transformer                                                   : 0.4/11 kV, 1.5 MVA, outdoor type oil cooled

Component Description:

Modules - The modules are of 240W/225W size manufactured by Titan Energy Systems Ltd. The cell assembly is laminated between glass/PVB and tedlar/aluminium/tedlar.  Electrical connections are made with quick connect plug.  By pass diodes are mounted in the termination box. Each module has 60 crystalline silicon cells of size 156 mm x 156 mm.  

MMS (Module Mounting structure) - The module mounting structures are designed to allow a simple assembly and installation of module and cabling.  The Module Mounting Structures comprising of galvanized M.S. I - beam sections properly embedded and grouted in the ground along with treated wooden beam properly fitted so as to withstand wind speed of 200 kmph.

Solar Array

The array comprises of 191 strings in total. Each string has 24 PV modules in series.  All the cables are underground type.

Array Cablings

All array cables are made of copper and XLPE cables of 1000VDC grade.

Data collection - The data acquisition system scans the solar, meteorological and PV system data every minute and records the average values of these date once in every hour.  The system has been designed for autonomous operation. 

                                    Array field                                    Control Room                                  

Power Evacuation -  The Solar Power Plant is connected through a short 11 KV line ( 200 mtrs) up to the 33 KV grid substation of the utility.  The LT Power from the Solar Power Plant is stepped up to 11 KV by a 0.4/11 KV, 1500 KVA transformer.  The HT line and the transformer is protected through a suitable circuit breaker. 11kv XLPE type cables have been used to connect the circuit Breaker and the transformer

Lightning Protection - Lightning protection consist of proper earth grounding of all array structures and other electrical equipments. L.A s have been provided in the substation.

Earth mat has been provided. Special earthing has been arranged for inverter and transformer.

Instrumentation – All electrical equipments including Inverters, LT panel, Transformer and HT gear have been provided with ammeters, voltmeters, power-factor meters, kWh meter and meter as and where required. Calibrated Energy meters have been installed to measure the quantum of export of energy.

Conclusion – Solar PV is a technology that offers a solution for a number of problems associated with fossil fuels.  It is clean decentralized, indigenous and does not need continuous import of a resource.  On top of that, India has among the highest Solar irradiance in the world which makes Solar PV all the more attractive for India.  The state of Orissa and Andhra Pradesh also houses some of the best quality reserves of silica.  India has a large number of cells and modules manufacturers.  In spite of all above advantages Indian Photo Voltaic programme is still in the infancy stage.  One of the reasons could be absence of simple, action oriented and aggressive PV policy of the country both in the state and central level.  More quickly we do it with the professionals more we protect our future energy security.