Keeping warm naturally

THE hexagonal shape of the bee honeycomb is often cited by engineers as the most economical use of 2-dimensional space. But now it appears the honeycomb design is ideal for saving energy, too.

Scientists at the Indian Institute of Technology (IIT) in Delhi have designed a honeycomb-type of insulation material that can reduce heat loss in many industries. The transparent honeycomb insulation system, as it is called, will also increase the efficiency of solar thermal energy applications by about 30-50 per cent.

Industries use thermal insulation to maintain the temperatures of fluids such as furnace oils, water and steam in the pipes transporting them. Conventional insulators are opaque and porous, besides containing several air gaps, all of which lead to heat loss.

N D Kaushika and his colleagues at the Centre for Energy Studies at IIT explored methods to minimise this energy loss and came up with the honeycomb insulator, which they say will diminish the convectional air currents inside the tiny cells. Made of a non-conducting polymer, such as perspex or Teflon, the material is light, transparent and weather-resistant. Not only does it save energy, it also spurs the production of solar energy for outdoor applications. The transparency of these materials may even enable sunlight to warm the pipelines carrying hot fluids and steam.

Researchers investigating honeycombs of various cell-shapes have found the thick, square-cell array to be simple. They can also be easily mounted on solar ponds and hot-water tanks to trap solar thermal energy efficiently. Kaushika and colleagues have proposed that a significant thermal energy gain in the tank could be achieved by keeping these materials on the top and side walls.

The scientists demonstrated the effectiveness of this method in a prototype field experiment, in which a storage water cube was insulated with 10-cm thick conventional insulation materials like glass wool at its bottom and 2 sides. The remaining 2 sides and the top were insulated with the transparent honeycomb material and the cube was then placed in the sun. The scientists claim a 40 per cent solar energy thermal conversion efficiency in their experiments.

Although USA, Canada and Australia are also researching this area, Kaushika claims theirs "is the first indigenously developed honeycomb material and it costs less than one-third of what is available abroad. Two-thirds of the fuel oil consumed in industries in India is used to heat or raise steam in boilers. The new insulation material would economise these processes, provided some initial investment is made."