Warming with Ice

Cooling with ice is one thing, but what about heating with ice? One company has developed a system that uses the latent energy contained within ice to heat a home efficiently and without releasing greenhouse gases into the atmosphere. Here’s how.

A large buffer is constructed next to a building in a moderate climate. By burying the buffer underground, its ambient temperature is kept nearly constant. During the summer, the cool water is used to reduce the heat in the building, for instance by water-cooling floors or by passive air-conditioning.

Now comes the innovation. As the months grow colder, the water in the buffer is also cooled in a gradual, measured process. This crystallization releases some energy in the form of heat. However, as the ice is being cooled, the heat is contained within the ice itself.

This phase transition heat is retained as potential energy in the ice. The trick lies in the fact that much more energy is needed to change a material’s phase (in this case from solid to liquid, or the other way around) than in heating or cooling a material within the boundaries of one phase.

An example makes this principle clear. It takes as much energy to melt one liter of ice (at a temperature of just below freezing) into water (at a temperature of just above freezing) as it does to heat a liter of water from just above freezing to 80°C.

It is this latent heat that is then used to warm the building very gradually during the colder season. In this manner, one m3 of ice stores about as much potential heating energy as 10 m3 of natural gas.

The system uses solar power during the autumn to add energy to the system. This means that greenhouse gases are reduced to an absolute minimum. The first large-scale system is being installed in a Dutch municipality building this summer.

Info and images via the developer’s site.