The Centre for Energy Studies at the Indian Institute of Technology (IIT), Delhi, is all set to change this thinking with its ambitious Rs 1 crore project of turning the IIT Delhi cafeteria into a self-generating green space, deriving energy for lighting, ventilation, electrical fittings and lifts from an innovative solar roof, comprising an array of photo-voltaic cells.

The project, if successful, will be a boon to farmhouses and corporate buildings, which use huge generators to meet power requirements at times of load-shedding. For instance, farmhouses in and around Delhi depend heavily on noisy and polluting generators as the Delhi Vidyut Board is unable tomeet all the demand. If they have a stand alone system as envisaged in the solar roof project, it will not only be eco-friendly, but also save on recurring fuel costs.

Says Dr N K Bansal, professor and head, Centre for Energy Studies, IIT Delhi, ``The objective of the IIT Delhi canteen project is to create an independent and stand-alone 20 kw electric system powered by solar energy. Such an experiment is the only one of its kind in the world. The concept has been there for a long time, but no one has tried to integrate it the way we are doing.''

The idea for the project was first mooted in October 1997 by the Centre for Energy Studies and the approvals came in April 1998. The project will be completed in March 1999. In all, 80 per cent of the project cost of Rs 1 crore is being borne by the Department of Non-Conventional Energy, government of India; the balance will be met by IIT Delhi. The Centre for Energy Studies is looking for corporate sponsorship for the seminal project.

Explaining the experiment,Bansal says, ``A solar roof basically incorporates photo-voltaic (PV) tiles that serve both as a roof and a solar electric power plant. The PV tiles trap the energy, which can be effectively and efficiently used to meet the power requirements within a given building. The project has four components--architectural, internal environment, solar and electrical. With a harmonious blend of these, a self-generating unit can function efficiently and meet its entire energy requirements without any outside help.''

In order to achieve techno-economic viability and integrate solar PVs into the proposed structure, the project team has undertaken a set of activities. These include assessment of peak load and load patterns; evaluation of climatic data, building geometry and shadow patterns; sizing of PV systems for DC voltage, AC voltage, transformer, controls for grid coupling, etc, and measuring instruments and data processing. Bansal talks of the advantages of such a system: ``It is noiseless, there are no black-outsand it saves conventional electricity, which can be diverted to industrial use. Though the per kw price works out to three times than that of diesel, the functioning is eco-friendly and the long-term benefits are immense. The maintenance cost is also minimal.'' Solar roofs will be particularly useful in far-flung areas, where it is difficult to install and maintain power lines and people wish to save money on huge transformers. In such a system, there is no question of transmission and distribution losses as it is a self-generating, independent unit.

Pointing out the cost benefits and ease of use of a solar roof, Bansal says, ``Farmhouses in and around Delhi invest huge amounts of money in noisy and polluting gensets. Added to that is the recurring fuel expense for running the generators. For an average farmhouse, the cost of a solar roof will work out to one-twentieth to that of maintaining, installing and running a generator. In a solar roof environment, there is no maintenance cost, except the cost ofreplacing the battery once in five years. This will be one-tenth of the total cost of the installation of a solar roof.'' The pay-back period of a solar powered environment will depend on the applications. However, rough estimates made by the Centre for Energy Studies reveal that the entire cost of installing a solar roof can be recovered in 4-5 years.

With the kind of climatic conditions that prevail in India, solar roofs will be functional throughout the year, but there might be some problems during the rainy season. To tide over these problems, Bansal says that the efficiency of the roof can be improved to store energy, which can then be utilised on rainy days.

Bansal also stresses that solar PV roofs will be able to emulate the characteristics of the building material they replace and be strong enough to absorb environmental impact, thermal shocks and seismic changes.

The replacement of conventional fuels with renewable sources of energy is essential if we have to achieve sustainability in ourenergy supply. As a non-polluting, safe and indigenous energy source, solar energy is a critical component of a renewable energy mix. Solar farms in blazing deserts are a common sight in scientific journals. The practical application of that at the IIT Delhi cafeteria is set to be a unique model of its kind in the country. Will the present project remain an exhibition case, totally insulated from real world applications? It remains to be seen how commercially viable and productive are the solar roofs.