If everything falls into place, Technopolis - the 6.75 lakh sq ft IT park also in Sector V - will be the first real estate project anywhere in the world to be registered under the United Nations Framework Convention on Climate Change as a clean development mechanism project.

If it happens, Technopolis will be eligible to trade in certified emission reductions, a potential source of revenue of around Rs 75 lakh.

There's a good chance that Technopolis will get the UNFCC registration since it is already a LEEDS-certified "green building".

"Any energy-efficient green building can apply to become a CDM project," says Sudipto Das, partner, Ernst &Young. Technopolis, claims Saraf, will save as much as 35.57 per cent on its energy bills - 2 MW in installed load and 87.5 lakh units/annum in usage - by using energy-efficient equipment - insulated walls, double-glazed glass with low U factor and solar heat gain coefficient, chillers with coefficient of performance (CoP) of more than 5, treated fresh air units along with heat recovery wheels, intelligent humidification controls, online carbon dioxide monitoring and control, and state of the art Integrated Building Management Systems (IBMS).

In theory, the calculation is simple. Technopolis will draw less power from the grid, leading to less emissions from power plants. The reduced emissions can then be quantified in terms of CERs and put up for sale to an agency in developed countries. For example, Saraf calculates he can earn CERs for 7,500 tonnes of carbon-dioxide per year, which at Euro 18 a tonne, brings him Rs 75 lakh a year.

Plus there are the savings on energy bills of Rs 435 lakh a year, and he quotes a figure of Rs 50 crore (Rs 500 million) saved in 10 years. And all this for an added investment of Rs 8.7 crore (Rs 87 million). Thus there is a lot to Saraf's claim that "Technopolis has opened a new source of revenue for the real estate industry".

But first, Saraf will need to get the documentation - the project concept note and design document - in place and E&Y has been asked to work on these. Then there'll be approvals from the designated national authority, the union ministry of environment in this case, highlighting the additionality criteria, and so on. Saraf expects the whole process to take about 4-5 months.

Saraf, of course, is not the only developer in Kolkata who is looking at new avenues of energy conservation. Albeit on a more modest scale, South City, a 1,600 apartment project coming up on Prince Anwar Shah Road, is exploring the possibility of using solar energy for its street lights, signages, pavement and garden lights, and hot water for the three swimming pools, club kitchens and the 20 rooms of the clubhouse.

Says D J Chakraborty, business development manager, South City Projects, "We are still working out the cost of going green to see how long the payback period will be."

And the economics is quite daunting. Each solar-powered street light post will cost Rs 30,000-35,000 (the battery, which costs Rs 4,000-5,000, has a 20-year life), far more expensive than the Rs 3,000 for a conventional one. This means the per unit cost of solar-powered electricity will be Rs 12, against the Rs 5 it costs for power from the grid.

The other consideration will be luminosity -  "Solar lighting is good for low-wattage applications only. For the kind of bright lighting the mall and facade will require, only a 250 W sodium lamp will do. At best, a solar-powered CFL lamp can give 9-14 W, good only for rural roads," says Anjan Mukherjee, electrical consultant for the project.

If solar-powered lighting doesn't quite meet the cost-benefit analysis, water heating definitely does, especially since the West Bengal government gives a 40 paise/unit rebate to users of solar-powered geysers.

S P Gon Choudhuri, director, West Bengal Renewable Energy Development Authority, sees other exciting possibilities in this area. "Domestic water heaters powered by alternative energies also have a potential to earn CDM credits. A domestic 5 litre water-heater needs about 2 KW. If 2,000 households switch over to solar energy, we'll save 4 MW. If all this power is bundled, it'll mean CDM credits worth Rs 50 lakh a year for 10 years. There's also a business opportunity here for private players who can do the bundling."

But Gon Choudhuri's pet project is Ravikiran, a set of 25 houses fitted with BIPV (building-integrated photo voltaic) tiles, that WBREDA is coming up with in Rajarhat. Each house will not only manufacture its own power, thus saving 2.1 KW of power from the grid, but each house will also feed 2,500 KW/hr annually into the grid. At Rs 4 per unit, it'll mean yearly earnings of Rs 10,000. The houses, priced at around Rs 40 lakh each, will be ready by February 2007.

Does that sound too futuristic? But then, with the earth's fossil fuels getting depleted fast, who knows what shape the future will take.