1. Regional cafe: Harnessing the rays of the sun

Regional cafe: Harnessing the rays of the sun

IIT Madras professors are working on the concept of decentralised solar-based DC power, which is an unconventional solution that has the potential to provide electricity 24x7

By: | Published: July 14, 2015 12:32 AM

When one walks into Prof Ashok Jhunjhunwala’s room in the electrical engineering department in IIT Madras, it does not look any different from the other spartan rooms of professors. Jhunjhunwala uses a remote control to switch on his fan, light and the TV in his room. Nothing particularly remarkable, except that all the electrical appliances in the room operate on direct current (DC) and not alternating current (AC), which is the standard the world over for power transmission and usage, both industrial and domestic. Power comes from a solar panel. It is an innovation which has been conceptualised and executed by Jhunjhunwala and Bhaskar Ramamurthi, the director of IIT Madras. This has been done in a few other departments and in some of the hostels of the institute as well.

What they are working on is the concept of decentralised solar-based DC power to the grid-based AC power, which is an unconventional solution that has the potential to provide 24×7 electricity access to all homes. They call this a disruptive innovation towards overcoming India’s power problem and making India one of the most ‘green’ countries. Of the 80 million homes in the country, 32.8% households are off-grid. Another 30-40 million homes are near off-grid. It is common for black-outs to last for 10-12 hours a day. Then there are the eternal power cuts. The solution they are offering could be a game-changer.

The professor and his team worked on how much power connected homes consume? Total domestic consumption is 200 TWh (terra-watt hours) per year for 1.25 billion people. This works out to an average of about 500 Wh/day per person or 2.5 kW per home per day. Average power consumption for grid connected homes is only 4 kWh per day as 33% homes do not have power. Most lower-income homes will consume no more than 1,000 Wh a day. “A 250 W solar panel will generate this,” says Jhunjhunwala.

The first step was to figure out how to provide decentralised solar power at home. All the electronics devices people use are DC while the power distribution comes from AC lines. At every point, AC power is converted to DC. In LED tubes, in cell-phones and laptop chargers, TVs, we are converting AC to DC power. Solar PV (photovoltaic) provides DC power. But the load is AC. What is needed is a DC-AC converter. “That was when I thought, why not have DC power at least in homes and in offices?” From substations, power is transmitted as AC. It can be converted to DC in homes and offices. The idea was to develop micro grids.

To cut down on conversion and battery costs, Jhunjhunwala and his team have come up with the idea of the discoms providing a 48-V DC line as an additional power line at home. “This will lead to a highly efficient usage of solar power. Battery can be added with higher efficiency, without having to resort to convertors, if required.”

Jhunjhunwala says he had to sell this dream to the industry as they had to manufacture DC appliances. Industry seems to have risen to the occasion. Crompton Greaves and Lucas TVS are making BLDC (brushless DC) fans. LED tube-lights and LED bulbs are coming from Inteligion. Another company, Cygni, is providing cell-phone and laptop chargers and also solar panels at a maximum power point tracking of 48-V. Amara Raja is taking care of batteries.

The pilot projects for the deployment of DC micro grid for off-grid and near off-grid homes have started. The two places this experiment has been successfully completed are the Irukkam Island in Andhra Pradesh and Kundithal in Tamil Nadu. Irukkam Island is in close proximity to Sriharikota Range, ISRO’s rocket launch centre. In spite of being located in a high-tech neighbourhood, only some households get electricity sporadically and others are off-grid in the Irukkam Island. Kundithal is a tribal village in a downhill forest area. Movement is restricted here after 5 PM because of erratic power supply. There have been visible improvements in the lives of these small, below poverty line communities. Women are able to cook in the evenings, children are able to study and men do not die of snake bites. There are trials going on in Tamil Nadu, Telangana, Odisha and Kerala.

Can solar DC solve the country’s power problems? Says Jhunjhunwala, “Solar DC will reduce the demand-supply gap and will make life better for off-grid and near off-gird homes. Distribution at 48-V helps in reducing losses.” He adds that instead of pushing this idea, a market-pull has to be created. The brown-outs can create this pull by introducing DC power lines at homes in addition to the existing AC lines. If there is 90% load-shedding, the DC line can take over and continue to power the basic needs of lights and fans. Uninterrupted DC Power Module (UDPM) is an equipment which is an uninterrupted DC power module or meter. It detects voltage drop to 90-V, cuts of AC line, but continues feeding 48-V DC. Even during some of the worst power shortages, 10% power can be made available.

The professor further explains: “If it is in DC form, 10% power is useful. There will be uninterrupted but limited power. 100 watts of DC will allow three lights, one fan and cell-phone charging, or one fan, three lights, 24-inch LCD/LCV and a cell-phone. If one wants more, one can add solar PV and, if needed, a battery to have solar DC.

IIT Madras team is convinced decentralised solar can make a huge difference. It would require minimal government investment. To install a UDPM, the cost is about R1,200. It would cost an additional R500 per home to add this to the existing power distribution infrastructure. With increasing scale, costs will come down. “India should take the leadership in decentralised DC power. This can complement conventional power generation from coal and nuclear as well,” says Jhunjhunwala.

There are issues which would have to be addressed such as finding acceptance from people for technology and DC. Then there is lack of standardisation and availability of DC home appliances. It would do well to remember that these are the people who, in the 1990s, developed Wireless in Local Loop technology for wider telecom access in developing countries through their corDECT solution, which is now widely deployed in India and 15 other countries.


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      Jul 14, 2015 at 1:20 pm
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