“WATER, water everywhere, nor any drop to drink,” lamented the becalmed Ancient Mariner. Oddly, the same is true of energy. As with the water that surrounds a desert island, there is abundant energy right under people’s noses, in the form of wind, sun, tides and heat. The trouble is that, like saltwater, none of these sources is easily tapped. Wind turbines, solar panels and devices that extract energy from wave and tide have become more common in recent years. But technologists have been slower to exploit the vast amounts of ambient heat available in the atmosphere, or produced by machinery.

True, some simple forms of heat recycling have been around for a while: using heated waste water to warm flooring and melt ice on driveways, for example. Such systems can also reduce the need to heat water in a home. By running pipes that carry outgoing waste hot water alongside those carrying incoming fresh cold water, it is possible to warm the inlet stream and thus reduce the amount of energy needed to heat it up. “Combined heat and power” stations produce electricity while also warming nearby homes using their waste heat. In industrial settings, waste heat from boilers and large refrigeration units is sometimes recycled to reduce heating costs elsewhere. And some green-minded householders are fitting “air-source heat pumps” to keep their homes cosy using heat extracted from outdoor air.

Yet, with the spread of computers, which generate vast amounts of heat and need to be kept cool, tactics for recycling are getting ever more creative. Power and cooling demands grow in tandem and, as machines get more powerful, the world is paying dearly to keep them cool enough to run properly. From 2006 to 2011 the cost of powering and cooling servers in America alone is expected to grow from $4.5 billion to $7.4 billion, according to the country’s Environmental Protection Agency.

Frustrated by seeing ice on his roof at the same time as being told that his computer simulations could not run faster because cooling costs were too high, Paul Brenner, a computer scientist at the University of Notre Dame, in South Bend, Indiana, decided to take action. Dr Brenner and his colleagues explored the idea of using waste heat from computers as part of a thermostat-controlled indoor heating system. In theory, such a system would save on heating and cooling bills by exposing computers to low-temperature offices while exposing office workers to the warmth of the computers.

To try the idea out, the team secured an office and plonked some servers in it, linked to the Notre Dame campus computer pool used for big calculations. A thermometer in the office detected when it was getting too cold and sent a signal to the network requesting that calculations be diverted to the servers in the office. Once the temperature had risen, a second signal suspended work on the servers.

Having proved that their idea worked on campus, Dr Brenner and his team tried it out in the wider world—specifically, at the South Bend Botanical Conservatories and Greenhouse, a botanical garden that was spending $115,000 a year running boilers and propane heaters to keep temperatures high enough for its plants to survive.

By constructing a computer rack similar to that used in the office test, the researchers were able to provide the greenhouse with badly needed heat. A short while later, the rack was joined by three more racks that today provide the greenhouse with enough heat to cut its gas bills by $15,600 a year—while simultaneously saving Notre Dame $38,000 in cooling costs.

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Source: The Economist

Tags: Economic opportunity | climate change | energy conservation | global warming | heat | reuse