3 Photovoltaic Installation Terms To Be Familiar With

Pro to voltaic (PV) installation

In order to understand a photovoltaic (PV) installation and its components we must be familiar with the following terms:

1. Standard Test Conditions (STC)
2. PV modules
3. PV string and Array

1. Standard Test Conditions (STC)

The output of a PV module is not stable it depends on irradiation, temperature etc., thus, we need fixed conditions in order to compare them, size and design our installation. These conditions are called as standard test conditions (STC):

a) Incident irradiance on the PV module surface: 1000W/m²

output power of the module is the point of the IV curve which shapes the greatest area. The irradiance influences mostly the current.

b) Cell temperature: 25°C

output power of the modules is the point of the IV curve which shapes the greatest area. As we notice the output voltage of a PV module depends mostly on its temperature.

c) Air Mass: 1.5

The Air Mass is the path length which light takes through the atmosphere normalized to the shortest possible path length (that is, when the sun is directly overhead AM=1).

2. PV Modules

All the datasheets include their electrical characteristics data in STC. For instance:

El. characteristics        Unit           Value
Nominal output          (Pmpp)W    280
Voltage at Pmax         (Vmpp)V    36.5
Current at Pmax         (Impp)A       7.7
Open circuit voltage   (Voc)V       44.5

3. String and Array PV Modules...............

Read full article

India’s Solar Power Targets Too High For Domestic Module Manufacturers, Claims Report

The Indian government is set to transform the solar power sector as it plans to substantially increase the capacity addition targets. Under the National Solar Mission, India had initially planned to achieve an installed solar power capacity of 22 GW by 2022. The new government, however, has given strong indications to increase this target.

The government has announced plans for several ultra mega solar power projects with capacity of up to 4,000 MW. Work on some of these projects has already started. Additionally, the government will allocate several projects through competitive auctions which could be worth tens of gigawatts over the next few years.

According to data released by the Ministry of New and Renewable Energy earlier this year, only 660 MW of the installed 2.3 GW module production capacity is operational in India. Just about half of the companies with manufacturing facilities are actually producing modules.

When the National Solar Mission was launched, prospective project developers were required to procure crystalline modules from domestic manufacturers and had the option to buy thin-film modules from other countries. A majority of the solar PV project developers opted for imported modules which came bundled with very cheap debt financing from development banks like the US Ex-Im Bank. US-based First Solar was actually one of the leading suppliers of modules during the first phase of the solar mission and the projects commissioned under the Gujarat solar power policy.

The government tried to correct this bias by introducing an obligation for prospective project developers to use domestically manufactured equipment. Of the 750 MW capacity auctioned during the first tranche of the second phase of the solar mission, 50% capacity was reserved to be commissioned using domestic content. Developers complied and have started placing orders with Indian module makers.

Future auctions may not include an obligation for prospective developers to use domestic content, as India looking to avoid international trade confrontation especially after the United States dragged the Indian government to the WTO over what the former calls discriminatory practices.

Indian solar module manufacturers have been waiting for years for any kind of boom in sales from the Indian project developers. Several manufacturers are under significant financial strain and have either reduced production facilities or have shifted focus to international markets.

Domestic manufacturers hope to cash in on the possible spike in demand from government-controlled companies. The Indian government has asked public sector companies and the Indian Army to set up large-scale power projects. As per government sources, these entities can give preference to and use domestic content and they would still be in compliance with the WTO regulations.

Read Source

Banks Push For Fixed Feed-in Tariffs For Indian Solar Power Projects

Lenders are calling for regulatory reforms in the Indian solar power sector, hoping that financial sense may soon prevail among the project developers who have been pushing tariffs to unsustainable levels in the competitive auctions.

The Indian government must consider switching to a fixed feed-in tariff regime for the solar power sector as is in practice for all other renewable energy sectors, officials of India’s Yes Bank have told Bloomberg. Current tariffs derived through reverse auctions have been pushed to levels where projects would lose viability, the officials added.

The fears about excessive competition in the solar power sector have been voiced ever since the landmark national solar mission was launched through competitive bidding. Since then, the fears have only grown as several states have implemented similar reverse auctions.

While the Central Electricity Regulatory Commission (CERC) issues tariff regulations for all renewable energy technologies including solar photovoltaic and solar thermal power every year, these regulations are not binding upon the state governments, which can choose their own method of project allocations.

Such has been the competition in the solar power auctions that project developers have offered discounts of more than 50% over the base tariff on offer. The recent auctions have seen developers offering to sell solar power at prices similar to the price of coal-based power.

Such cut-throat competition has forced some developers to even forfeit the projects they had secured in auctions as it made no financial sense to pursue them further. Lenders, especially Indian financial institutions, thus see such projects as investment risks.

The CERC has reduced solar PV tariffs by about 15-20% every year over the last five years. There are indications that this reduction would not be as steep over the next few years. In fact, tariffs of solar thermal power projects have actually started to increase marginally over the last couple of years.

Interestingly, Gujarat, the state with the largest installed capacity in the country, has never conducted an auction to allocate solar power projects. Every single large-scale solar power project operational in Gujarat today was allocated to companies with a feed-in tariff for 25 years.

A new solar PV report from the IEA finds that 70% of solar PV power installed around the world in 2013 benefited from a feed-in tariff (+ 4% from a feed-in tariff plus tender), and 66% of all solar PV power capacity installed in the world at the end of 2013 benefited from a feed-in tariff (+ 2% from a feed-in tariff plus tender).

Action in India: Government Announces 15-GW Solar Power Purchase Program

Solar energy action in India just got more exciting. The federal government of India announced the largest of its National Solar Mission (NSM) programmes to date — 15,000 MW over the next five years.

In this phase of the NSM, part 1 of tranche 1 will consist of 1,000 MW. The government will buy power from a maximum of 20 developers, and each project size is limited to 50 MW. Each developer can bid for up to five projects with a total of 250 MW.

The latest initiative has the following key takeaways:

1. Economies of scale will bring down the cost of solar power in India
2. Smaller players faced with financial challenges will be phased out
3. Large international developers and investors will enter India’s solar power sector

The first tranche will consist of projects available at a single solar power park. They will be developed by a joint venture of different federal and state governments in the Kurnool district of Andhra Pradesh state. However, the draft guidelines issued by the Ministry of New And Renewable Energy (MNRE) are a little confusing.........

Click to read full original Article

India drafts auction rules for 1,000MW solar capacity

India making headway with Prime Minister Narendra Modi's clean-energy push, announcing draft rules to auction 1,000MW of solar capacity in Andhra Pradesh, reports Bloomberg.

Released by the Ministry of New and Renewable Energy, the rules outline by-invitation bidding for contracts to construct plants at a solar park in the southern state, mandating the use of locally-made panels and cells to a quarter of the capacity.

The mandate is a boon to home-grown manufacturers, considering that India dropped a plan to impose antidumping tariffs on solar panels imported from U.S., China, Taiwan and Malaysia, which is expected to boost the flow of investments into the power sector.

According the auction rules mentioned in theBloomberg report, the responsibility for implementing capacity will be transferred to the central government, away from the states. The central government has raised its capacity installation target to 15,000MW by 2019, five times the current national capacity and approximately triple what it co plan to boost India's clean-energy targets and shift responsibility for implementing capacity away from states to the central government. By 2019, the central government expects to install 15,000 megawatts, more the five times the current national capacity and about triple what it promised in 2012.

Each company can bid for up to 250MW of capacity, with each project capped at 50MW. Winners will sign 25-year power purchase agreements with state-run power trader NTPC Vidyut Vyapar Nigam Ltd. (NVVN).

A venture between the Solar Energy Corp. of India, New & Renewable Energy Development Corp. of Andhra Pradesh and Andhra Pradesh Power Generation Corp. will run the solar park. It will see to the provision of roads, water and power substations in support of the projects.

A schedule included in the draft sets building of 3,000MW by 2017, 5,000MW by 2018 and 7,000MW by 2019.

Read Source

India’s Largest Power Producer To Invest $810 Million In 750 MW Solar PV Project

Public sector companies are heeding to the Indian government’s direction to set up large-scale renewable energy projects, especially solar power projects. The latest to join the long list of government-owned companies to announce a major investment in the solar power sector is NTPC Limited, India’s largest power generator.

NTPC Limited (formerly National Thermal Power Corporation) has announced plans to set up a 750 MW ultra mega solar photovoltaic power project in the state of Madhya Pradesh. The company plans to invest ₹5,000 crore ($811 million) into the project. The project would be a major milestone in the company’s near-term target to install 3,500 MW solar power capacity over the next five years.

A large portion of the 3.5 GW capacity would come up in the southern states of Andhra Pradesh and Telangana. NTPC plans to install similar ultra-mega solar power projects in the two states.

The Indian government has directed state-owned companies to invest heavily in solar power projects. This strategy has been adopted in lieu of the decision not to impose anti-dumping duties on imported solar power modules. According to government sources, government-owned companies can give preference to domestic solar power equipment under WTO regulations.

NTPC Chairman stated that the company will invite bids for solar PV modules from domestic as well as foreign companies but will request foreign companies to manufacture the equipment in India.

Read full original article here

Types of Solar Panel and Which one is the best PV Panel

Crystalline Silicon (c-Si) for PV Technology

Crystalline Silicon (c-Si) is a crystalline form of Silicon (Si) which is widely used in the manufacturing process of the crystalline solar panels (Poly and mono-crystalline PV) in the photovoltaic technology. Almost 90% of PV technology is based on Silicon which is mostly used in crystalline silicon solar panels.

There are many factors to use the silicon in photovoltaic technology but the important one is purity of silicon, which means the more purification in silicon, the more ability of the solar panel to convert sunlight into electricity as output power.

Crystalline Silicon (c-Si) forms the basis of poly or multi and monocrystalline Silicon PV cells, which we will discuss in detail as follow.

Monocrystalline Solar Panels

“Mono” means “single”, as the name indicates, The Monocrystalline solar panel cells are made of single pure silicon crystal. It is also called single crystalline silicon because once single crystal used to make the array which provides Solar Panel (PV) purity and uniform appearance across the PV Module.

Monocrystalline Solar panels (PV cells) are in rounded shape and the Silicon crystal bars look like cylindrical in the entire PV module.

Good to Know:

To differentiate between Polycrystalline and Monocrystalline PV (Photovoltaic or Solar panel) is that monocrystalline solar cells look cylindrical with rounded edges.

Advantages

• The efficiency of Monocrystalline Solar panels are 15-20%, while the latest monocrystalline solar panels achieves 25% efficiency in the labs and 21% is the verified efficiency. In the US, the efficiency of the E20 Series is approximate up to 20% and the X-Series of SunPower PV (Photovoltaic panels) provides 21.5% efficiency.
• Monocrystalline PV (Photovoltaic or Solar panels) requires the least amount of space and takes up a small area on the roof.
• The average life of Monocrystalline solar panels are about 25 years while other PV panels manufacturers claims 25 to 30 year life expectancy.
• Its performance is better than polycrystalline at same rating light conditions. In addition, monocrystalline solar panels produce up to four times the amount of Electrical energy as compared to thin film solar panels.
• In short, Monocrystalline Solar panels are the most efficient available PV module, most popular technology in the market, commonly available, takes up the least amount of area on the roof and easy to use and replace.

Disadvantages

• Monocrystalline solar panels are costly. The initial cost of monocrystalline PV panels is too high and expensive as compared to thin film solar PV modules or Polycrystalline Solar panels.
• As it is made of single silicon crystal, hence the partially covered area of solar panel with snow, dirt or shade may break the entire circuit of PV.
• A large amount of pure silicon ends up as waste. To make silicon wafers and arrays in large cylindrical shape (a process, which used to make monocrystalline Silicon in called Czochralski process), the four ends of the PV cells are cut out of the ingots, which result in large amount of pure Silicon waste.
• It tends to be more efficient when the temperature goes up i.e., it works better in warm weather and full sunshine, but it is not a considerable fact for most homeowners.

Polycrystalline solar panels

“Poly” means “many or multi”. As the name tells the story, it is made of a number of different pure silicon crystals, combined together to make a solar or PV cell. The shapes of these cells are rectangular and need less silicon as compared to monocrystalline solar panels which makes them less expensive, but their efficiency is also lower than the monocrystalline PV cells (approximately 13.5-17%. It is also called polysilicon or multi-crystalline silicon and first introduces in 1981 in the market.

To make Polycrystalline PV (photovoltaic) cells, pure raw silicon is melted and poured into a square mold which is cooled and cut into perfectly squared wafers and arrays. There is a random crystal arrangement Polycrystalline solar panel and reflect some light back, so it looks a little bluer. Nowadays, the prices of Polycrystalline solar panels come down and get popularity again in the US, UK, Australia and other local markets.

Advantages

• Polycrystalline solar panels have lower heat tolerance (which means their performance is lower in high temperature as compared to monocrystalline solar PV modules. As heat may disturb the solar panels and reduce their life). However, it is not considerable fact to most homeowners and Solar panel buyers and they don’t take into account while design the solar panel installation layout.
• The process to produce the polycrystalline silicon is cost less and less complicated.
• In short, it is cost effective to manufacture, good efficiency, takes up a small area on the roof, commonly available and easy to replace and use.

Disadvantages

• The efficiency of polycrystalline solar panels is approximately 13.5-17%. This technically means that if 100W of solar potential energy strikes the solar panel, then its output would be about 13.5W to 17Watts solar produced electrical energy. Hence, it is slightly less efficient than monocrystalline solar panel.
• The same surface of polycrystalline PV modules (in size) would produce less power as compare to monocrystalline solar panel (but this is not always the case).
• It is not suitable to use as compared to thin film and monocrystalline solar panel in terms of elegance (when needed) because it hasn’t a uniform appearance, but only random and odd blue color.

String Ribbon Solar Cells

A process in which multi crystalline silicon strips and foils are manufactured for Photovoltaic (PV) Technology. In this process, high temperature resistance wires are pulled through the molten silicon to form multi –crystalline thin ribbon of silicon crystals. These very thin ribbons then cut into different lengths to form PV and Solar cells. Solar panels made with String Ribbon technology looks the same to traditional polycrystalline PV panels. The process was first developed in the 1970s by Mobil-Tyco, Solar Energy Corp and The Evergreen Solar were the major manufacturer of using String ribbon Technology to make the solar cells. Note that Note that String Ribbon PV panels are also made out of polycrystalline silicon.

Advantages:

• Lower cost production, simple and easy to use.
• String Ribbon Solar panels efficiency is about 13-14% (while in laboratories, researchers achieved 18-19% Efficiency)

Disadvantages:

• Manufacturing is more energy extensive
• Lowest space-efficiency

Thin Film Solar Cells (TFSC) or (TFPV)

Thin Film Solar Cells (TFSC) are also known as Thin Film Photovoltaic Cells (TFPV) or Amorphous PV Modules.

Integrating one or more thin layers of PV materials or thin film (TF) on a substrate, e.g. metal, glass, plastic etc. is the basic process to make thin film solar panels and it is a second generation solar cell. The thickness of film varies from a few nanometers (nm) to tend of micrometers (µm) while the much thinner of thin film has been developed. The first generation Crystalline Silicon solar cell (c-SI) uses up to 200 µm silicon wafers.

Following are the subcategories (Types of Thin Film Solar panels) by which PV materials are integrated on a substrate.

• Amorphous Silicon (a-Si/TF-Si)
• Copper Indium Gallium Selenide (CIGS/ CIS)
• Cadmium Telluride (CdTe)

Below are the third generation thin film solar cells, which are not available commercially at all and researcher are hopeful to make the dream come true (very soon).

• Organic Photovoltaic Cells (OPC/OPC) … (It is available now)
• Dye-sensitized
• Polymer solar cells
• Quantum dot
• Copper Zinc Tin Sulfide,
• Nanocrystal
• Perovskite Solar Cells

Thin film solar panels are cheaper but less efficient than conventional Crystalline Silicon solar cell (c-SI) technology. However, recent technology development verifies the lab cell efficiency of Cadmium Telluride (CdTe) and Copper Indium Gallium Selenide (CIGS/ CIS) reached up to 20%.

Advantages

• The Large scale production of thin film solar panels are less complicated than crystalline based PV cells.
• They are cheap as compared to other monocrystalline PV / Solar panels.
• The uniform appearance of thin film solar panels are more attractive and can be used for beautification purpose as well.
• It comes also in flexible form which may be used for many purposes and applications and make sense when used where space is not an issue.
• It has high temperature tolerance, i.e. high temperature and shading have less impact on thin film solar panels.

Disadvantages

• It requires a lot of space. Typically, they are not useful for residential and homeowners.
• The additional support structure, cables, maintenance, etc. for thin film solar panel installation makes the system costly.
• The overall life expectancy of thin solar panels is lower than that of poly- and monocrystalline solar panels.

Amorphous silicon (a-Si or a-Si:H) Solar Cells and PV Modules

An amorphous silicon solar cell which is a subcategory of Silicon thin film solar panels has recently become popular in the market. As they need less than (say 1%) of Silicon used in the crystalline solar cells and very less efficient than poly or monocrystalline solar panels (approx 5-6%).

To manufacture an amorphous silicon solar cell one or more layers of photovoltaic materials are sandwiched onto a substrate as a gas spray which is called “vapour deposition”.

Cadmium Telluride (CdTe) Solar Cells

Cadmium Telluride thin film solar panels are based on Cadmium telluride and the only PV (Photovoltaic) technology, which is cost effective as compared to Silicon crystalline solar panels in a significant part of the market especially in the multi kilowatt system.

The efficiency of these solar panels tends to be in range between 9-11%.

First Solar has installed over 5 gigawatts (5GW) of cadmium telluride thin-film solar panels worldwide. The same company holds the world record for CdTe PV module efficiency of 14.4%.

Update: in August 2014, First Solar announced a device with 21.0% conversion efficiency. In 2014, the record module efficiency was also raised by First Solar from 16.1% up to 17.0%

The first solar powered 40-MW (CdTe) PV (Photovoltaic) Array installed by JUWI Group in Brandis, Germany.

Copper Indium Gallium Selenide (CIGS/ CIS) Solar Cells

The commercial production of flexible Copper Indium Gallium Selenide PV cells started in Germany in 2011. They are made of Copper, Indium, Gallium and Selenide by integrating on a substrate like plastic or glass, along with anode and cathode (electrodes) on the back and front side to collect electrical output power. CIGS or CIS solar panel cells have high temperature tolerance and work better in a warm climate, so they work even better when cells deposited on glass.

The efficiency rates for CIGS solar panels typically operate in the range 11-14 %. However, the highest value achieved by National Renewable Energy Laboratory researcher team is 19.9% and again the best efficiency achieved as of October 2013 was 20.8%. In addition, scientists at EMPA, (Swiss Federal Laboratories for Materials Science and Technology) developed CIGS cells on flexible polymer foils with a new record efficiency of 20.4%.

Expect this, many other thin film solar panels are still in the research and gradually growing the development. You may hear more unexpected and interesting news about these developments soon in coming daysJ.

BIPV: Building Integrated Photovoltaic Panels

This is not something new, but the same as they may be thin film or Silicon crystalline solar panels or both, in the shape of roof tiles or what the design needs to be. BIPV (Building Integrated Photovoltaic) is designed to be a part of a building like walls, roofs, facades, windows and other things which may fit with photovoltaic materials (Solar Shingles are the best example Building Integrated Photovoltaic [BIPV]). It looks very nice and beautiful, but beautiful things are expensive too

Unfortunately, Building Integrated Photovoltaic BIPV is too much expensive system and less efficient as well as compared to other PV (photovoltaic) cells and Panels. So it is not recommended to homeowners or small scale users to integrate BIPV systems as they are used in huge projects like a 10MW plant in the desert near Las Vegas.

Solar Thermal Panels

It is a different PV or Solar power system rather than the explanation above. They do not produce the electricity, but convert the solar power into required heat to heat up the water for swimming pool or general purpose usage at home. It is also good to know that some solar thermal or PV panels can even be used for heat and air-conditioning too.

Hybrid Solar Cells and PV Panels

An Organic material (a Semiconductor material which properties lay between in insulator and conductors and used for electrical conductivity) is sandwiched with an inorganic high electron conduction material to form the photovoltaic (PV) layers. Which efficiency is greater than the single material layer and has both the advantages of organic and inorganic semiconductor masteries.

The hybrid PV cells are low cost by R2R process (roll-to-roll or Real-to-Real process: creating electronic components and devices on a flexible plastic roll or metallic sheet and foils) and developing solar power conversion as well.

The most efficient hybrid solar panels available are Panasonic (formally Sanyo) HIT PV module with Incredible 18.6% efficiency, which takes less space on the roof as well.

Hybrid solar panels are very expensive then poly or monocrystalline PV panels. If you have a lot of space on your roofs, then it is not recommended to use the hybrid solar panel system otherwise you are wasting your money to generate the same electrical power as you generate with crystalline solar panels.

Which is the best type of Solar Panel for Home Use?

This would be a little bit difficult to decide which one is the best solar panel for you and if you don’t know even the basic about PV then it is recommended to contact an expert to select the best one solar panel for your particular situation, but will discuss the typical matter and you will be able to get a little bit idea which may help you to select the best one solar panel for your home use.

As we know that “Cost and space” is the main factors for proper PV panel selection, so we will briefly discuss the topic.

Space:

As the majority of us haven’t large space on their roof, windows etc, than thin film solar panel are not for you. Obliviously, but crystalline base solar panels in the best choice then, and if size really matter, then go for the highest rated out power solar panels because the same sizes PV panels have the different rating such as 60W, 150W, 200W etc.

If size matter, Then which one is best? Mono or Poly crystalline Solar panel

Both are good for you with the same advantages except that monocrystalline solar panels are more space efficient and produce little more electrical power than polycrystalline but this is not always the case.

One thing more that polycrystalline solar panels are slightly less expensive, but also less space efficient as well.

In addition, for the same rating (say 150W) of mono and polycrystalline solar panels would generate approximately the same electrical output power (with a few negligible difference) but polycrystalline would take up little more space as compared to mono-crystalline solar panel.

Read Source

First floating solar farm powers up in the UK

800 solar panels, mounted atop plastic floats have been installed on a reservoir at the Sheeplands Farm in Berkshire. The $400,000+ project is the first of its kind in the UK, and is expected to provide the property with a new means of green energy.

800 solar panels, mounted atop plastic floats have been installed on a reservoir at the Sheeplands Farm in Berkshire. The $400,000+ project is the first of its kind in the United Kingdom, and is expected to provide the property with a new means of green energy production.

The floating solar panel farm comes from French company Ciel et Terre who has also set the technology up on quarry lakes, irrigation canals, tailing ponds, and more. Altogether, the company operates and maintains 55 solar power plants and are actively expanding worldwide.

Once the build was complete, the owner of Sheeplands Farm set up a company called Floating Solar UK, to distribute the technology to the rest of the UK.

Farm owner Mark Bennett said to the BBC, "We are a fourth-generation farm so we have had to diversify, because it's hard...This green energy [provides] another revenue stream."

For those curious, Bennett is using Ciel et Terre's modular Hydrelio system which, according to the company’s site, has a 30-year lifetime. Ciel et Terre manages all aspects of the development process for these types of projects, including the design, engineering, financing, legal, construction, operation, and maintenance services. This ensures that the technology they provide their customers with operates at peak efficiency.

"Thanks to the cooling effect of water on PV panels, our systems produce more energy than land-based systems of a similar size," said the company.

Bennett hopes his story sparks an interest in the benefits of the technology throughout the rest of the UK. "We are speaking to big utility companies, to agricultural companies — anyone with an unused body of water,” he said in a quote from the Telegraph. “The potential is remarkable."

Floating solar panels are considered a viable source of renewable energy for reasons beyond the technology’s ability to occupy previously unused property (speaking about the surface of the body of the water here). You see, when the solar panels cover part of the water, the body as a whole has its temperature reduced. This, coupled with the fact that some of the water is not exposed to the open air, reduces water evaporation by 33% on natural lakes and ponds, and up to 50% on man-made facilities (numbers as per Ciel et Terre).

The Hydrelio system that Bennett purchased is also a particularly durable floating solar farm, as it can withstand winds of up to 118 mph, and changes in water levels of up to 20 feet.

Read source

Rooftop solar plants to create 3.25 lakh jobs in 10 years.

Small rooftop solar power plants alone are likely to create 3.25 lakh jobs cumulatively in the next ten years in the country, says a report by Bridge to India, a company engaged in businesses like Strategic Consulting, Market Intelligence and Project Development.

"The small rooftop scenario (sector) would contribute the most to job creation, with around 3,25,000 cumulative new jobs in next ten years," said the report.

"The supply chain for small rooftop systems would include many intermediaries, spreading margins across more layers", it said.

The report divided the solar power sector into four segments - small rooftops, large rooftops, utility scale projects and ultra mega projects.

The average size of a small rooftop solar is 3 KWp (kilowatt peak), the power achieved by a solar module under full solar radiation. The average size of a large scale rooftop is 250 KWp, utility scale project 20 MW and that of ultra mega solar scheme is 1,000 MWp or 1 GWp.

In large rooftop systems, around 2.20 lakh cumulative jobs and in the utility scale scenario around 71,000 cumulative jobs will be created in the next 10 years.

The report added that the least number of jobs will be created in the ultra mega scale category. The total number of jobs in this scenario comes to only around 63,000 in ten years.

The general policy recommendations to enable the sector to grow under any of the four scenarios is creating transparent and dependable solar policies to encourage Indian and international investment.......

Read more

How do solar PV Inverters work?

What is the basic scientific principle based on which solar PV inverters work?

What are the main components of the solar PV inverters and what are their main roles and the principles on which each of these components work?

Four major functions or features are common to all transformer-based, grid-tied

inverters:

• Inversion

• Maximum power point tracking

• Grid disconnection

• Integration and packaging

Inversion - The method by which dc power from the PV array is converted to ac power is known as inversion. Other than for use in small off-grid systems and small solar gadgets, using straight dc power from a PV array, module or cell is not very practical. Although many things in our homes and businesses use dc power, large loads and our electrical power infrastructure are based on ac power. This dates back to the early days of Edison versus Tesla when ac won out over dc as a means of electrical power distribution. An important reason that ac won out is because it can be stepped up and travel long distances with low losses and with minimal material. This could change inthe distant future if more of our energy is produced, stored and consumed by means of dc power.

Today, the technology exists to boost dc electricity to high voltages for long distance transfer, but it is very complex and costly. For the foreseeable future, ac will carry electricity between our power plants, cities, homes and businesses. In an inverter, dc power from the PV array is inverted to ac power via a set of solid state switches—MOSFETs or IGBTs—that essentially flip the dc power back and forth, creating ac power.

Maximum power point tracking - The method an inverter uses to remain on the ever-moving maximum power point (MPP) of a PV array is called maximum power point tracking (MPPT). PV modules have a characteristic I-V curve that includes a short-circuit current value (Isc) at 0 Vdc, an open-circuit voltage (Voc) value at 0 A and a “knee” at the point the MPP is found—the location on the I-V curve where the voltage multiplied by the current yields the highest value, the maximum power.

As cell temperature increases, voltage decreases. Module performance is also irradiance dependent. When the sun is brighter, module current is higher; and when there is less light, module current is lower. Since sunlight intensity and cell temperature vary substantially throughout the day and the year, array MPP current and voltage also move significantly, greatly affecting inverter and system design. The terms full sun or one sun are ways to describe the irradiance conditions at STC (1000 W/m2). Sunlight intensity varies from nothing to full sun or a little more than one sun in some locations and conditions. This means that PV output current can vary from zero to full array rating or more. Inverters need to work with arrays at their lowest voltages, which occur under load on the hottest days, as well as at their highest voltages, which occur at unloaded open circuit array conditions on the coldest days.

In some climates, temperatures can vary by 100°F or more, and PV cell temperatures can vary by 150°F. This means array voltage can vary by ratios of nearly 2:1. A string of 22 Evergreen ES-A-210 modules, for example, will reach a Voc of 597 Vdc with a cell temperature of -30°C (-22°F). The MPP voltage (Vmp) can get as low as 315 Vdc in an ambient temperature of 50°C (122°F). In most cases, the maximum power point voltage operates over a 25% variation. However, this number is lower in regions with more consistent year-round temperatures, such as San Diego, California, and is higher in regions where temperature varies more, such as the Midwest and Northeast. Finding the array’s MPP and remaining on it, even as it moves around, is one of the most important grid-direct solar inverter functions.

Grid disconnection - As required by UL 1741 and IEEE 1547, all grid-tied inverters must disconnect from the grid if the ac line voltage or frequency goes above or below limits prescribed in the standard. The inverter must also shut down if it detects an island, meaning that the grid is no longer present. In either case, the inverter may not interconnect and export power until the inverter records the proper utility voltage and frequency for a period of 5 minutes. These protections eliminate the chance that a PV system will inject voltage or current into disconnected utility wires or switchgear and cause a hazard to utility personnel. If an inverter remained on or came back on before the utility was reliably reconnected, the PV system could backfeed a utility transformer. This could create utility pole or medium voltage potentials, which could be many thousands of volts. A significant battery of tests is performed on every grid-tied inverter to make certain that this situation can never occur.

- See more at: http://www.eai.in/club/users/narsi/blogs/26758#sthash.5l1hOmXb.dpuf