I pulled out the latest issue of Green Futures for a bit of light relief. It instantly lifted my mood as it reminded me just… how exciting sustainability issues can be.
India burns a lot of energy to stay cool. It needn't, says Martin Wright, with innovative alternatives to air conditioning.
Anyone familiar with stepping from the street into an Indian office block on a hot day will know that it’s like walking from a furnace into a fridge. Air conditioning is also one of the country’s more voracious consumers of energy – accounting for 30-40% of domestic consumption.
Keeping buildings cool enough for comfort is uncontroversial. But the quest for ever chillier indoor climes, achieved by turning hot air cold at eye-watering expense, is increasingly coming under critical scrutiny. Unsurprising, given the rapid rise in electricity prices…
The good news is that there are a number of innovations under way which enable people to stay cool in less costly ways, and some of these look as much to the past as the future.
Infosys, which has achieved more than most in terms of cutting energy devoted to air conditioning, learned a lot from past masters, says its Head of Green Innovation Rohan Parikh. “Nearly half our energy was being consumed in cooling or aircon, so it was an obvious priority. We started off by saying to ourselves: ‘Air conditioning was only invented 100 years or so ago, so how did people manage to keep cool in the past?’ That led us to look at ancient monuments, old buildings, caves, even. And so we hit on the principle of ‘radiant cooling’”, which draws heat from the room to walls cooled by water circulating through embedded pipes.
“The principles of physics were very compelling”, explains Parikh, “so we were keen to try them out on our new Hyderabad campus. Now we knew that even if we proved them in practice, people would be sceptical: they’d say, ‘ah well, it worked for Infosys because it was a particular sort of building in a particular place, it probably wouldn’t work for us…’”
But in the Hyderabad campus, Infosys had the perfect testing ground: a building divided into two huge wings, identical in every respect. One was fitted with conventional air conditioning, the other with radiant cooling. “They were ideal experimental conditions”, says Parikh: “real buildings occupied by real live people.” The difference was dramatic: the wing with radiant cooling consumed 38% less energy – and detailed ‘comfort surveys’ showed staff much preferred it, too. The capital spend required was actually 1% less than the building’s conventional twin. “Financially”, concludes Parikh, “it’s just amazing.”
Harvesting the cooling effect of the earth can be a productive way of keeping comfortable, too. At TERI University’s elegant new campus on the southern fringes of Delhi, so-called ‘earth air tunnels’ make use of the fact that the temperature 4m below the surface is equal to the annual average above ground. So there it’s 25.6°C at all times, even though the temperature outdoors might be a burning 45°C in summer and a chilly 4°C in winter. Drawing air up from the tunnels helps keep buildings cool in summer and warm in winter. Together with a north-facing façade, thick walls packed with insulation and ‘evaporative cooling’ produced by the effect of water trickling down specially designed towers, this all helps to reduce the need for artificial aircon.
Indeed, the design is so effective that the student hostels do without it altogether – a rarity in modern accommodation – with the temperature never rising above the 20s even in the hottest of summers. Combined with a design which makes maximum use of natural light, it means the campus’s energy bills are 40% below average.
The Torrent Research Centre in Gandhinagar, Gujarat’s new political capital, is an energy miser. It consumes around 54kWh per square metre, compared to an Indian average for new buildings of 280-500kWh. It’s similarly miserly when it comes to carbon emissions, accounting for just 72kg per square metre (compared to an average 380-670kg per square metre).
The key is passive solar design, which drastically reduces the need for both conventional air conditioning and artificial light. By using passive downdraught evaporative cooling, it brings indoor temperatures close to bearable even on the hottest summer days.
Costs were 13% higher than the conventional equivalent – but such were the savings on energy bills that this was recovered within a year. Indeed, they were so dramatic that the entire capital will be repaid within 13 years, from the energy savings alone.
Photo: Mahindra World City Developers Ltd