Solar, Utility Integration

India Builds Solar: A BIPV First

Issue 4 and Volume 11.

India’s first green housing project facilitated with building-integrated solar power has been developed in a new district of Kolkata. Both environmentally and economically attractive, this project acts as a trailblazer for the rapidly developing country. Jaideep Malaviya reports.

The burden of combating global warming is not restricted to developed countries and many developing countries have shown their commitment to moving towards a more sustainable, low-carbon economy.

A good example of this type of commitment comes from India’s West Bengal region, where the country’s first housing complex using roof-integrated photovoltaics has recently been completed.

The policy behind the Rabi Rashmi Abasan project, which in the local Bengali language means ‘solar ray-based dwelling’, was the brainchild of S. P. Gon Choudhary, managing director of the West Bengal Green Energy Development Corporation Limited (WBGEDCL), a state government-backed renewable energy undertaking.

During his tenure as director of West Bengal Renewable Energy Development Agency (WBREDA) Gon Choudhary was inspired while watching a television documentary on eco-housing projects under way in developed countries in early 2001.

He subsequently approached the Ministry of Housing of the government of West Bengal and made a representation to them, outlining a new concept known as ‘New Century’s Housing’ based on energy efficiency using state-of-the-art technologies. The first fruits of this concept have appeared with the Rabi Rashmi Abasan housing development, a name which was proposed by the chief minister of West Bengal, Shri Buddhadeb Bhattacharya.

This 58 kW eco-housing project was developed by Germany’s Conergy in partnership with the WBREDA as an initiative in solar architecture and is a flagship project in India.

Selling solar

As with other developed and developing nations, India’s buildings are one of its more energy intensive sectors and are thus responsible for more than 30% of the total energy consumption of the country. The focus on implementing energy efficient technologies in buildings in order to move towards long-term sustainability is therefore obvious. And, as India is a tropical country blessed with consistent, almost year-round sunlight, Building Integrated Photovoltaics (BIPV) is a logical choice, showing clear promise.

The authorities at the Ministry of Housing agreed to provide 1.76 acres (nearly three quarters of a hectare) of land in a district of Kolkata city, the capital of West Bengal state in eastern India.

With plans to become a major hub for business, trade, industries, IT, institutions and culture, the New Town area for the development’s location is 10 km from Kolkata’s Central Business District and about a kilometre from the International Airport.

The land was obtained from West Bengal Housing Infrastructure Development Corporation Limited (WBHIDCO).

After obtaining land, environment and power evacuation clearances from concerned authorities, work on building Rabi Rashmi Abasan took shape by 2006, based on a solar passive architecture design. In the meantime, West Bengal State Electricity Distribution Company Limited (WBSEDCL) had passed an order allowing the development of captive power generating systems up to 250 kW by individual entities using net-metering. ‘This order was crucial to make Rabi Rashmi Abasan project a reality and contributes to the success of the project’, explains Gon Choudhary. West Bengal is still one of the few states in India to allow captive generation by private entities.

Development in the detail

The Rabi Rashmi Abasan residential housing complex has 25 private houses and a community centre with a net connected load of 380 kW, of which 58 kW is supplied using roof-integrated solar PV.

The built area of each house is 155 m2 and, in addition, there are 14 m2 of terrace. Each cottage has 2 kW of roof-integrated solar PV tiles that use crystalline technology from SunTechnics India, a subsidiary of the Conergy Group, which developed the project in partnership with WBREDA.

The installation, valued at approximately €600,000 overall, consists of 26 photovoltaic systems comprising 464 units of Conergy’s C125W solar modules, which were individually customized in various geometric shapes to fit the roof profiles of each building.

The installations are each expected to generate 2.4 MWh of power annually. The energy will be fed to the grid using net metering and will be purchased by WBSEDCL. Consumers will pay the cost of any net energy consumed through the local distribution grid. In the event of a grid failure, in addition to the system inverter, a backup battery of 160 Ah is provided.

Like many countries, India has a multi-stage tariff for residential electricity consumption. However, up to 100 kWh consumers are subsidized to varying degrees depending on the state utility. As consumption increases so does the tariff. A key advantage of the solar PV system is that it allows electricity usage in the cottages to stay within the subsidized tariff band, despite additional consumption.

Energy efficient technologies and design principles have also been incorporated into the design of the housing project. A small water pond surrounding each cottage aids with passive cooling. The south-facing solar passive architecture is designed such that during the summer months, hot air within the building rises due to convection and is expelled through ducts in a ‘turret’ at the top of the building. The pond surrounding the dwelling allows a cool breeze to circulate and a simple fan is sufficient to keep the room comfortable to live in. Temperatures in Kolkata (Calcutta) city reach a summer maximum of up to 42°C. The temperature varies between 12°C and 14°C in winters and does not go below 10°C, while humidity in summers is usually around 85%.

In addition, each cottage also has a 100 litre per day solar thermal water heater and cavity wall insulation has also been installed in strategic locations to improve thermal efficiency.

As part of the housing complex the hydro-pneumatic water pump, responsible for supplying water in the houses, is of a variable frequency type. The pump only begins to operate when there is a reduction in pressure in the system, caused by demand from the houses, and then only up to the speed required to maintain full pressure, thus saving energy during operation.

Within the housing complex there is a community centre for recreational activities and public functions. It has an 8 kWp solar PV system including 2 kWp of BIPV on the windows.

Each of the eight windows incorporates 125 Wp transparent PV and there are 17 standalone street lights also operating on solar PV and obtained under a government subsidy programme.

There is also a 6 kWp grid-connected roof-top system which is again operated on a net metering basis. The electricity generated by this installation offsets the power drawn from the grid for applications such as pumping, garden lights and the internal lighting, fans and other night-time power demands.

Green housing, good economics

The cost of each roof-top PV system was about Rs0.7 million (US$16,000) and the solar systems are not subsidized, nor is there any premium feed-in tariff — although in the case of excess production the power utility offers a rebate of Rs 0.40/kWh up to a maximum limit of 200 units per month ($1.87). However, the approximate cost of each dwelling is Rs 4.8 million ($112,000) and since the solar component was a relatively small fraction of the total housing cost, incentives for its installation were not necessitated by investors. Indeed, purchasers willingly came forward to buy into the project and all the houses have been sold — a direct measure of the success of the initiative.

A joint venture enterprise between DC Properties Ltd, part of the Development Consultants Group, and West Bengal Housing Board, the development is currently managed by the Bengal DCL Housing Development Company Ltd.

The Kolkata New Town development of Rabi Rashmi Abasan is a landmark project in Indian infrastructure. Using solar passive architecture as part of a new housing concept, such projects are particularly conducive to the region’s prevailing climatic conditions.

It has showcased the benefits of solar PV that will inspire other builders and those corporate players that have a commitment to using renewable energy technology and energy efficiency measures. Indeed, some of the country’s leading building companies, such as DLF Builders, Siddha group and MRMGF, have shown considerable interest in setting up mega-scale projects using roof-integrated solar PV as an integral component. Rajesh Bhat, chief executive of SunTechnics India explains: ‘Using building-integrated photovoltaic (BIPV) elements, buildings can maximize their energy efficiency by saving 0.5 kg of carbon emissions for every kilowatt hour of solar power produced. Green buildings are thus highly advantageous for consumers and real estate developers in large capital cities. In addition to reaping the benefits of energy cost reductions, green buildings are also interesting architectural applications as they are highly distinctive and innovative.’

Jaideep Malaviya is a consultant and freelance journalist based in India.
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