The Basics of Solar Power Plant Installation
Parag Nanavaty explains the understanding required while installing roof top or ground type grid connected solar power plant.
understanding required while installing roof top or ground type grid connected solar power plant
Green House effect is natural since the sun generates heat. Green house gases are Water Vapour, Carbon Dioxide, Methane, Nitrous Oxide, Ozone and some synthetic chemicals. As long as the blanket of green house gases is within limits, the earth’s average temperature remains lower. However human activities like burning of fossil fuels (coal, oil, natural gas and nuclear plants) and global warming emissions, lead to concentration of green house gases, resulting in increasing average temperature on earth.
The importance of renewable energy has increased since this generates very low green house gases, helps in reducing concentration of green house gases in atmosphere, and reduces significantly the green house effect – Global Warming.
Renewable energy mainly generated from wind and sun, is abundant and not going to deplete anytime. On the other hand, fossil fuels are depleting and are major cause for global warming. Like the sun and wind, biofuel is one of the good alternatives of renewable energy. Instead of burning stubble on field and generating carbon dioxide if it is converted into bio gas then good alternative shall be available easily in India.
Reducing global warming means better atmosphere and human life. It reduces air and water pollution, human breathing and neurological issues and many other ill effects.
Before the start of the renewable energy movement, India had deficit of power generation capacity. More power and planning is needed to install more fossil fuel plants. However due to various commitments by the Government of India to reduce green house effect at various international conferences, the focus has turned on increasing renewable resources. Today India is the fifth largest country in the world in renewable energy generation map. The increased use of renewable resources is also expected to reduce India’s dependence on expensive imported fossil fuels, and great saving in forex. It helps in generating more and more employment. It ensures power reaches to remotest part of India where today people do not even have power connections.
India is the first country in the world coming up with separate ministry for renewable energy with the aim to increase focus on it and to show the world our commitment and responsibility to reduce the effects of global warming. Since then, the government is working very hard to increase the installation of renewable energy plants. They are targeting substantial share of renewable energy in total power generated and make the country energy surplus.
India Target for Renewable Energy by 2022
The target for renewable power by 2022 is 175 GW, which includes 100 GW of Solar power, 60 GW from wind power, 10 GW from biomass power and 5 GW from small hydro power.
There are different types of renewable energy resources, like:
Grid connected power generating plants like: a) Wind, b) Solar Plant – Ground Mounted and Roof Top, c) Small hydro plants, d) Biomass power, etc
Off grid Power Plants like: a) Waste to Energy, b) Biomass, c) Solar Pimps, and
Other Resources: Family biogas plants and water mills/micro Hydro, Tidal and water wave power.
Irradiance is an instantaneous measurement of solar power over some area. The unit of irradiance is Watts per square metre (w/m2). Maximum irradiance on a sunny day on earth is 1000 w/m2.
Irradiation or Insolation is a measurement of the cumulative energy measured over some area for a defined period of time (e.g., annual, monthly, daily, etc). The common unit of insolation is kilowatt hours per square metre (kWh/m2).
While transmitting energy from sun to earth due to various reasons huge amount loss takes place. In spite of all these losses on an average, the sun energy on earth per 1 m3 is equivalent to one barrel of oil, 200 kg of coal and 140 m3 of natural gas. Major influencing factors for solar energy are location of place, its latitude, clouds covers, aerosols, elevation and shading.
Maximum solar energy concentration is near the Tropic of Capricorn and Tropic of Cancer. The 121 countries that form the International Solar Alliance (ISA) are mostly or partly located in this sunshine area.
Solar projects are mostly viable in India since high level of solar irradiation is received in Rajasthan, northern Gujarat, Tamilnadu, parts of Ladakh region, parts of Andhra Pradesh, Maharashtra and Madhya Pradesh. Karnataka is also receiving fairly large amount of radiation as compared to many other parts of the world.
Configuration of Solar System
The main components required to configure complete Off Grid or Grid Connected system:
Solar PV panels and related mounting structures
Inverter in case of Grid connected system and Battery in case of off grid system, and
Other accessories like environment friendly Cable, Combiner box, DC disconnects, AC disconnects, Charge controller and transformer in case of Grid Connected system.
Photo Voltaic Cell
A number of silicon cells connected together makes a Photo Voltaic panel. Generally panel voltage will be in range of 12, 24 or 36 V. However it changes from manufacturer to manufacturer depending how many cells are connected in series. Current delivery of each panel depends on its internal construction how many cells are connected in parallel. Its power delivery depends on intensity of light falling on the whole panel. Power delivery changes with change in sun position during day, cast shadow – uneven or even, or total blackout due to clouds. Practically on sunny day peak generation is possible during 4-6 hours depending on season and location of site.
Two different types of panels are available: Crystalline Silicon Cell and Thin Film Cell. There are two sub categories in crystalline panel – Poly Crystalline and Mono Crystalline. Mono Crystalline panel is more efficient (max up to 20%) but Poly Crystalline (efficiency 16%) is generally more in use due to its lower cost and rectangular shape that captures most incident light.
Generally crystalline type panel is preferable for any solar system. However when different shape like curvature or any other type panels are required thin file type is the choice.
Normally solar panels are designed for 40oC. However they are exposed to operate at high temperatures but then its power delivery capacity reduces. While designing a system study the de-rating factor and consider reduced power delivery capacity.
Mounting of panel is equally important to get the desired power from solar system throughout the day. Site location will give its latitude and which hemisphere on earth. The angle and mounting direction shall be decided based on these two parameters.
Panel output will be connected to the inverter.
PV panel and inverter are required to work as a pair. Size of PV panel shall be in coordination with inverter such that:
Number of modules in string x Voc< Inverter Vmax (Voc – Open voltage of Panel and Vmax – Maximum permissible DC voltage of Inverter)
Number of modules in string x Vmpp < inverter’s MPPT voltage range
Iscstrings < Inverter Iscmax (Iscstrings – short circuit current of PV string, Iscmax – short circuit current of inverter)
Inverter shall be mounted nearer to PV panel. It reduces voltage drop in system. It will also reduce the chance of fatal accident since DC voltage between panel and inverter will be very high.
Note: Do not combine different rating panels in one string. Panel which are likely to get exposed to shadow shall be connected together and if possible to separate inverter.
Voltage generated by solar panel is DC voltage. In grid or for any direct usage we need inverter which converts DC voltage into AC voltage.
Power generated by PV panel is non linear due to dependency on solar irradiance and operating temperature. The inverter should be capable of generating maximum possible power from the system. It should be most reliable in performance, higher efficiency even at part load with lightening and surge protection.
During full sun PV panels operate efficiently. Generated voltage, current and frequency through inverter matches with grid and synchronises with it. Generated active power will flow from solar system to grid. Inverter with its in-built MPPT controller tries to maintain maximum power generation from panels.
However during clouds or at night the PV panel does not give desired voltage and power. When it does not match with the grid, power flow stops from PV system to grid. During the time it is likely that grid loses its stability due to sudden drop of large amount of grid power. To maintain the grid stability and constant voltage of grid, the inverter shall have facility to feed in reactive power even though there is no DC voltage available from PV panels.
In grid connected system a transformer is required to boost voltage to make it suitable for gird connection. Please procure the transformer under the guidance of the inverter supplier. Inverter output shall be fed to the transformer primary and secondary will be connected to the grid. Hence proper matching is equally important for feeding power to grid to get desired benefits.
In off grid system battery shall be charged during sun light. To charge battery, charger is required. Battery Ah capacity depends on total ampere of load to be connected and time duration for which power is required.
Special cable with 30 years life shall be used due to stringent operating condition. Cables are exposed to all sorts of environment hazards. Selection of cable is important to reduce voltage drop in system and to achieve desired performance of system. It is flexible tinned copper cable with polyolefin insulation compound covered by halogen polyolefin to make it suitable for outdoor installation, having low smoke emission, low toxicity during fire and UV resistance. Other main features of cables are – resistance to mineral oils, acids and alkaline, maximum conductor operation 120oC during 20000 hours of operation, minimum operating temperature – 40°C, suitable for 1.5 kV DC and tested at 6.5 kV DC for 5 minutes. Its mechanical features are strong enough with impact, tear and abrasion resistance, minimum bending radius 4 times of overall diameter and safe pulling force 50 N/sq mm.
It is recommended to adapt reliable and strong connection method. It ensures proper connection at all junctions and avoids voltage drop or wire breakage.
SCADA is another important part of system for monitoring data of the generated power over a period of time. It is more important to have SCADA in case of grid connected system.
India reaches 20 GW in Cumulative Installed Solar Capacity
India has achieved a milestone 20 GW in cumulative solar installations to date, according to a report by Mercom India Research based on recent figures. 20 GW was the initial goal set up for 2022 by the National Solar Mission, which has been reached four years ahead of time. This demonstrates the commitment by the new government, which is working hard to achieve the revised target of 100 GW solar by the year 2022.
According to Mercom’s India Solar Project Tracker, the utility-scale cumulative installations total for India now stand at ~18.4 GW, with rooftop solar accounting for another ~1.6 GW.
For the first time, solar was the top source of new power capacity additions in India during calendar year 2017, with preliminary figures gathered by Mercom showing that solar installations reached ~9.6 GW and accounted for 45 percent of total capacity additions.
The top State for solar installations was Telangana, followed by Karnataka, Andhra Pradesh, and Rajasthan.
India’s rooftop solar sector also witnessed steady growth last year alongside the rise in grid-connected utility-scale solar. Rooftop solar accounts for ~1.6 GW of the 20 GW of capacity installed so far, and could be bolstered by a new Ministry of New and Renewable Energy (MNRE) policy designed to further its growth.
MNRE recently announced a new program that would provide distribution companies (DISCOMs) incentives for commissioning rooftop solar projects. The effectiveness of the program remains to be seen.
Even with the new MNRE initiative, the pace of overall solar installations is likely to be less impressive in 2018 as several protectionist government policies appear poised to increase costs and uncertainty.
“The government’s revised solar installation target of 100 GW by 2022 has recently been clashing with Prime Minister Modi’s “Make in India” Initiative to promote domestic manufacturing. The recently announced 70 percent preliminary safeguard duty recommendation, the ongoing anti-dumping case, and a 7.85 percent port duty on imported modules are together creating an atmosphere of regulatory uncertainty that is taking a toll on the industry and slowing down installation activity,” said Raj Prabhu, CEO of Mercom Capital Group.
“20 GW of solar installations is a laudable achievement for India considering the initial goal. However, it took eight long years to reach 20 GWs and hopefully the pace will pick up going forward. Private solar companies in India have gained vital experience over the years and are looking for the government to create an environment conducive for growth and remove the policy uncertainties that are currently plaguing the industry,” added Prabhu.
Parag Nanavaty, CEO, ForeKen Technology, is always looking for new business design challenges and helps medium scale companies to bring them on the top notch in their area of operation.