Monthly Archives: September 2013

Advanced String Monitoring System of today

What happens when a module fails in a 1-megawatt photovoltaic system, bringing down a 3-kilowatt string?

If the monitoring system tracks production for each of the two 500-kilowatt inverters, the loss of output will only represent 0.6 percent of a 500-kilowatt array’s capacity — virtually impossible to detect, especially when pyranometers commonly used in utility-scale PV plants measure solar irradiance with a +/- 2 percent uncertainty (or more). Even comparing the output of both inverters would hardly allow detection of the fault: inverters measure power output with a relatively high uncertainty (typically +/- 1 percent to +/- 5 percent).

Arguably, even multiple string failures could go unnoticed until the next inspection when maintenance technicians perform systematic string testing.

In order to quickly detect such failures and minimize the associated energy losses, some PV plants are equipped with string monitoring equipment. This consists of “smart combiners” collecting current (and sometimes voltage) for a string or a small group of strings, and sending this data to the monitoring system where some software analyzes the information and identifies low production string conditions.

String monitoring is a common practice in most European markets, along with string inverter designs for PV systems, which intrinsically provide the ability to monitor at the string level, since each inverter is a string or a small group of strings. In a recently published report about global PV monitoring markets, GTM Research and SoliChamba Consulting estimated that 100 percent of new utility-scale PV plants in Germany in 2012 were string-monitored, along with 95 percent of large commercial systems and 85 percent of small commercial ones (including plants with string inverters).

In other parts of the world like the U.S. and Japan, however, very few PV plants are string-monitored, even in the utility-scale segment. In those markets, the dominant perception is that string monitoring significantly increases the initial cost of the PV system without providing enough yield increase to justify such investment. No independent study has either proved or disproved this theory, and opinions may vary between EPC firms and project developers.

In order to better understand the logic behind this different approach, let’s examine the economics of a broken “3-kilowatt string”. Assuming that the average annual yield is 1,500 kWh/ kWp and the faulty string goes undetected for six months (until the next inspection), the lost production would amount to 2,250 kilowatt-hours. For a 2006-built German plant benefiting from the 40 euro cents feed-in tariff, this would represent a $1,200 loss. For a 1-megawatt system, the additional cost of string monitoring equipment ranges from $10,000 to $15,000, which is the equivalent of $500 to $750 annually over a twenty-year time span (excluding financing costs and installation, which is usually part of overall EPC budget). In these conditions, an average of one string failure per year would justify the investment. For a U.S. plant with a PPA (Power Purchase Agreement) price of 10 cents, however, the same production loss would only be worth $225, so it would take two to four annual string failures on the same 1-megawatt array to justify the investment. This simple calculation goes a long way toward explaining the gap in string monitoring adoption rates between Germany and the U.S.

In the past few years, a new DC array monitoring practice emerged in America, referred to as “zone monitoring” or “sub-array monitoring.”

By collecting sub-array data from the master combiner, zone monitoring provides an intermediate level of granularity for issue detection and diagnostics, at a much lower upfront cost than string monitoring ($3,500 to $5,000 for a 1-megawatt plant). With this approach, the ability to detect subtle issues is more limited, and the guilty string cannot be specifically identified — it is only possible to single out the sub-array that is underperforming because of it. In the case of our previous example, if each 500-kilowatt master combiner includes 15 sub-arrays (for a 33-kilowatt individual capacity), the loss of a 3-kilowatt string represents a 10 percent reduction of the affected sub-array’s capacity — an easily detectable anomaly. GTM Research and SoliChamba Consulting estimate the adoption of DC monitoring in the U.S. in 2012 at 65% in the utility-scale segment, 25% in the large commercial segment, and 15% in small commercial. Most of it is believed to be zone monitoring.

As often in the solar world, the ultimate decision to adopt a technology lies in the hands of the investors and their technical advisors. In Europe, these firms often mandate string monitoring for large-scale plants, and will consider a PV system less valuable if it does not include such monitoring capability. In the U.S., few solar investors have a strong opinion on this topic, and independent engineering firms that validate the production estimates used in financial calculations do not consider any difference in output whether a plant is a monitored at the inverter, sub-array or string level. In such circumstances, project developers and EPC firms are unlikely to invest in string monitoring technology.

Over time, as more data becomes available about module and string failure rates, we can expect the choice of monitoring approach to become less cultural and more financial.



Unleashing Delhi Solar Potential

Unleashing Delhi solar potential is an in-depth analysis of the potential for Roof Top in Delhi. Since Delhi is facing a potential electricity crisis. Demand of the Electricity is expected to reach an all-time high of 6000MW this summer. With the crippling power supply situation there is an urgent need to rethink electricity and supply in the city.


Within the last decade Delhi electricity demand rose by an average of 6% every year. From 20 BU in 2002 the demand will reach over 33BU by 2017 a 65% growth. As a capital and second richest state in the country Delhi is in a very good position to take the lead in transitioning to a decentralised,sustainable energy paradigm. For this capital has started a campaign “switch on the sun” campaign. In the coming days the campaign seeks to bring distribution companies, government decision makers, regulatory bodies & electricity consumers all together.

In coordination with RWA’s we have  individual colonies like sukdev vihar , Delhi Pledge their commitment for Roof Top solar.Delhi  can be 2GW solar city by 2020,the total land are on which Delhi is built could support 123GW therefor 2GW will require only 6% of the city land. The First Step toward positioning solar Roof top solar energy as a solution is to understand its potential in the city.

India preparing first floating solar power station

KOLKATA, India, Aug. 22 — The U.S. Energy Information Administration lists India as the world’s fourth-largest energy consumer. The Indo-Asian News Service reported on Wednesday that the country’s shortage of domestic energy supplies has heightened its interest in renewable energy.

India currently has 211 Giga-Watts of installed electricity capacity; most is generated by coal-powered plants. Coal remains India’s primary source of energy and the country has the world’s fifth-largest coal reserves. Because of insufficient fuel supply, India suffers from a severe shortage of electricity generation, leading to rolling blackouts, which is having a negative impact on the country’s exports. In 2011, India was the 10th-largest economy in the world, as measured by nominal gross domestic product. The U.S. Government’s Energy Information Administration projects India and China to account for the biggest share of Asian energy demand growth through 2035. While India’s primary energy consumption more than doubled between 1990 and 2011, according to the International Energy Agency, India’s per-capita energy consumption remains lower than that of developed countries.

Searching for energy alternatives, West Bengali capital Kolkata may soon get India’s first floating solar power station by the end of next year. The facility has been proposed by Indian solar expert S.P. Gon Chaudhuri.

“Each station would require around 3,000 square feet of space to generate 20 kilowatts of power,” Gon Chaudhuri said. “There are many water bodies that could be used for this. Such floating solar stations would generate more energy as research has shown that if the panels stay cooler, they generate more energy, up by 16 percent.” The project is scheduled to be installed in a pond in Victoria Memorial in the city of Kolkata in India. The floating solar platform is being funded by the Ministry of New and Renewable Energy, and is said to be the first of its kind in India.  Reservoirs and dams of hydroelectric power stations are also attractive spots for the floating solar power generator. “This would not only help conserve water for the dry seasons when power generation goes down because of lack of water but would also help us generate extra power – solar and hydro from a single station,”

India’s Ministry of New and Renewable Energy, which has underwritten the research, expects the project to be implemented by 2014. Current cumulative solar installations in India stand at 1,761 megawatts. In 2012 India installed 980 megawatts of solar power installations, with about 557 megawatts installed thus far in 2013.

Many Indian analysts subsequently commented that, as India’s solar market is still in its infancy, starting a trade war could become costly when New Delhi’s prime concern should be to encourage new technologies, competition and free markets. Solar power has the immense capacity to bring in stability to the fluctuating electricity tariffs in India, as it is cheaper than thermal and domestic coal. States have realized that solar sector is positive as most solar radiation in the worst parts of India is better than in the best parts of Europe. Solar is a serious area to work for large scale projects in India.

Solar Creates Jobs Along With Clean Energy

Solar Energy has a great potential to end the power sufferings, it provides clean energy, removes all the disadvantages provided by the fossil fuels and the added advantage is it creates well paying jobs.

Many studies have proved that solar and renewable energy creates 10 times more jobs than provided by fossil fuel industry.

University of California (UC) report concludes we can expect 86,370 new energy jobs in the U.S. by 2020 if we continue with our current energy mix. But if 20 percent of our energy were to come from renewable sources, then 188,000 to 240,850 jobs could be created, depending on the proportion of wind, solar and biomass energy. The American Council for an Energy-Efficient Economy estimates that 1.1 million jobs could be created in the next 10 years through investments in energy efficiency technology.

Solar offers high paying manufacturing and installation jobs as well as jobs for highly skilled people such as engineers and managers, often in areas of the country struggling with higher unemployment.

Author of the UC report Daniel Kammen, head of UC Berkeley’s Renewable and Appropriate Energy Laboratory says, “Investing in clean energy technologies would both reduce our trade deficit and reestablish the U.S. as a leader in energy technology, the largest global industry today.”

Scope for a ‘green’ career in India
One of the major developments in the Indian solar sector is the JNNSM initiative, which basically aims at generating 20 GW of solar power by year 2020.

In a growing industry like solar power generation, opportunities will also naturally be on the rise.

“As per official statistics, in order to fulfil the 20,000MW installed capacity targets under the Jawaharlal Nehru National Solar Mission, the Indian solar energy industry will need an estimated 300,000 people by 2022 across all domains, profiles and levels,” says Singh. Commenting on the scope for a career in this field, Nayak shares, “The scope is unlimited since PV offers a unique opportunity to solve the 21st century’s energy and environment related problems simultaneously.” He adds, “There are enough opportunities in production and project execution of solar projects as massive plans are being laid by every state.”

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