With consumers looking for greener and safer technology, manufacturers are introducing an array of solar inverters
By Richa Chakravarty
Tuesday, July 10, 2012: With rising electricity bills, power crunch and the ‘go green’ trend, the solar inverter market is hotting up. To cash in on this in a big way, almost all major inverter players now offer solar inverters, for both domestic and commercial purposes. On the utility front, these inverters are now being used in massive, multi-megawatt projects, and hence, are getting bigger in size. While for the home market, they are becoming more compact and adaptable.
What’s the latest in the market
According to the requirements and usage patterns of the consumer, Indian manufacturers offer a wide range of solutions including standalone or off grid solar inverters, grid tied solar inverters, string inverters for grid tied solar systems, central inverters, and battery backup inverters.
A conventional inverter and a solar inverter do not differ much, except for the energy supply. A conventional inverter converts DC from a battery into AC. On the other hand, a solar inverter uses a string of PV panels as the DC source. Power inverters use the AC mains to charge batteries, whereas solar inverters use solar energy.
Su-Kam Power Systems Ltd offers hybrid solutions rather than just solar or grid based solutions. The company claims that its latest product, Brainy, is based on the new age solar hybrid technology which is meant for domestic use. “Hybrid systems utilise grid, solar or stored power to run any load, while the dominant source of power is solar energy. This inverter can address the challenges of the existing on-grid and off-grid systems, making it cost effective and durable,” says Kunwer Sachdev, managing director, Su-Kam Power Systems Ltd.
Uniline Energy Systems Pvt Ltd offers a cost effective inverter solution based on advances in digital signal processors (DSP). Sophisticated functions such as maximum power point tracking (MPPT) help to get the most energy out of the PV modules. “DSP is one of the advanced technologies (meant for high speed data processing), which when used in conjunction with sine wave technology delivers output that is completely stable and distortion free. This power is actually purer than what is supplied from the
grid. This makes it absolutely safe to run even the most sensitive equipment,” informs RK Bansal, managing director, Uniline Energy Systems Pvt Ltd
Indo Powersys Pvt Ltd offers standalone inverters with inbuilt solar charge controllers. These solar inverters provide both AC and DC output, making it an ideal choice for small solar home power generators, in which AC and DC appliances can be connected. “These solar inverters are used as a standard building block in solar power systems. Our solar inverters are specially designed to meet low or idle current consumption patterns and for high reliability,” says Anoop Agarwal, partner, Indo Powersys.
Convergence Power Systems Pvt Ltd offers three variants—solar inverters, solar hybrid inverters and solar hybrid intelligent inverters. According to Sreekumar, director, Convergence Power Systems Pvt Ltd, “Convergence intelligent solar inverters utilises maximum solar power and enhances battery life as well.”
upsINVERTER.com offers its ‘UTL Hoodi Backup’ which is a combination of a UPS system, an inverter and a voltage stabiliser as it provides pure sine wave output. It is powered by microcontroller digital technology, and works in both UPS and inverter mode. This means that no additional stabiliser is needed for input AC regulation. Says Yogesh Dua, director, upsInverter.com, “Its
features are user configurable—one can enable or disable them to suit individual needs. Also, if exposed to excessive loads it shuts down automatically and beeps. It then gauges the load, before switching itself to operating within the specified limits, eliminating the need to manually reset the system.”
Hita Technology Pvt Ltd offers both grid and off-grid solar inverters. Its domestic type of inverter ranges from 600 VA to 10 kVA. “Usually, solar inverters, by default, get charged by solar energy, and will switch to the main line only when there is no sun. But our products have an inbuilt solar charger, which charges the batteries using solar energy at the same time as it uses power from the main line to recharging,” explains Arun Ghosh, managing director, Hita Technology Pvt Ltd.
Advancements in technology
In order to provide a high performance, reliable and cost effective solution, the power industry is currently focusing on microinverters, hybrid systems, solar power conditioning units (PCU) and maximum power point tracking (MPPT) solar charge controllers. An MPPT device is an electronic DC to DC converter that converts a higher voltage DC output from solar panels down to the lower voltage needed to charge batteries.
Solar hybrid inverters use a new technology, which changes the DC from the PV array and battery into AC. If the mains and solar power are both available, the charging current is taken from both the sources, with priority given to solar power.
Microinverters, the latest entry in the Indian power industry, convert DC from a single solar module or pair of modules into AC, unlike central inverters that convert power generated by the entire array of solar modules. The difference between a solar microinverter and a solar inverter is that the former works with a single solar panel, while the latter works with 10 to 50,000 solar panels.
Microinverters are more reliable as the failure of a single piece affects only one solar panel. In the case of normal solar inverters, such a failure affects the whole array of solar panels. Also, the life of solar inverters is much higher than the life of the solar panels compared to the 5-10 year life of string inverters which have to be replaced. Microinverters claim to have a 5-25 per cent higher power production capability as they manage to maximise the power production from each solar panel (MPTT), as compared to string inverters which do so from the whole solar array. Easy installation and flexibility in configuration are added benefits. Having proved its mettle in the international arena, this innovative product is yet to create waves in the Indian market.
Inverters are now programmed according to the user’s preference. The latest software introduced by manufacturers enables users
to programme the system according to their specific needs. Such a software is also imperative while harnessing solar energy, as the solar panels are usually mounted far away from the systems. Su-Kam has programmed its software in such a way that the batteries remain fully charged during the day and will only be used as backup when set to night mode. During the day, one can limit the use of the inverter through permanent or ad hoc programming of inverters. The inverter can also be programmed remotely by connecting it through the computer. “The software developed by Su-Kam enables users to decide when they want to use power from the battery bank and when they want to use solar power, directly. Thus, the user can also decide the source of energy for peak and off-peak hours,” informs Kunwer Sachdev.
The industry is moving to higher efficiencies and minimal system losses by offering 99 per cent efficient power conditioning units
(PCU). A PCU is an integrated system consisting of a solar charge controller, inverter and a grid charger. It has the facility to charge the battery bank either through solar power, grid power or a DG set. “Earlier, these inverters used to be of low efficiency. But the efficiency of solar inverters has increased in the recent past. To attain greater efficiency and keep a track of distortion,
manufacturers are adopting innovative methods like sun-tracking systems for rooftop standalone installations to get 20-30 per cent extra power from the system,” shares RK Bansal.
Customisation: The need of the hour
Customisation is the key factor propelling the inverter market in India. The products currently available in the market are all amenable to being further customised. Hence, prior to designing any solar solution, manufacturers have to consider factors like the input power requirement, load, use per day, grid power supply, backup time required, changes related to design such as the DC
bus, battery voltage settings, charging current requirements, communication and remote monitoring requirements, changes in the mechanical design to conform to various IP standards, etc. Having concluded a 100 VA
HF inverter project for The Energy and Resources Institute (TERI), Yogesh Dua opines, “Customisation is essential as individual consumers have different requirements. According to the preference of the consumer, manufacturers offer only inverters or inverters with AC chargers along with the solar charge controller.”
Even the software in the case of the PCU is tailor made to meet the customers’ requirements. Such software integrated into the solar power system enables users to remotely monitor, configure and control their power systems at any time and whenever required. This is especially helpful in the case of high end applications with zero tolerance on power outages. And, if the software facilitates common modes of communication via the Ethernet, GSM, GPRS, etc, then such systems are very easy to use even when mobile.
Tips for buyers
Sreekumar opines that what consumers need to keep in mind are their own requirements. “Since the industry offers customised
designs keeping consumer preferences in mind, buyers need to evaluate their requirements and the way they want to utilise it. Efficiency is one basic and core element that should be given first priority. The efficiency of solar modules, batteries and inverters should be kept in mind while opting for a solar inverter,” he says.
Kunwer Sachdev shares his opinion: “While opting for a solar inverter, installation plays a vital role—check whether the mounting structure for the module is galvanised or powder coated. Galvanised mounting structures will last long and remain protected from rust. Also, one should keep in mind the wind speed it can withstand, its tilting angle, etc.”
One of the basic concerns of the buyer is reliability. While making a purchase decision, consumers worry about the credibility and experience (related to the technology) of the manufacturer. “The product should be procured from a credible and reliable source that offers after sales support. Also, the buyer should keep in mind the size of the company, the technology on offer, the efficiency of the inverter and past performance,” says RK Bansal.
While opting for a solar inverter, technicalities should be given first priority. Thus, the type of waveform must be considered. It is recommended that buyers opt for sine wave high frequency inverters due to their higher efficiency, which results in lower power losses. Charge controllers must be based on pulse width modulation (PWM) for the longer life of the battery. MPPT charge controllers are good but cost a lot.
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