Several years ago, IBM pioneered a hot-water cooling system for use in supercomputing. Dubbed Aquasar, the system relied on hot water rather than refrigerant or huge banks of air conditioners, and it managed to significantly cut power consumption in server rooms. IBM is now working on a more advanced type of cooling solution, dubbed Thrive, which could dramatically slash power consumption.

Most estimates put data center cooling costs between 30-50% of the total depending how many machines are deployed and the type of cooling required for the building. IBM thinks it could cut cooling-related power consumption by up to 65%. That’s 65% of ~35%, but it could still reduce the total cost of data center operation by as much as 23%. Those are the sorts of figures that get companies interested.

Here’s how the system works: Like any common air conditioner, the Thrive system relies on a heat pump. As the name implies, a heat pump is used to transfer heat from one area to another, taking advantage of the fact that heat energy tends to move from areas of high temperature to areas with lower temperature. A typical heat pump system can either pull cold air from the outside and use it to heat a home, or pull hot air from the outside and exploit the energy gradient to cool the home. Typically, these devices run on electricity, though that power can be sourced in a number of ways.

This video explains both the Thrive project and how the cooler works in more detail. Interestingly, it relies on silicon desiccants — the same material you find in vitamin bottles or inside packages — to provide the adsorption function that the entire system relies on.

What IBM has built is a heat pump that can run largely on its own waste heat. That’s not something data centers are short on, since even the most efficient cooling solutions on low-power servers still produces a great deal of heat energy. Instead of a compressor, the IBM design has an adsorption heat exchanger. Adsorption (not absorption) is the adhesion of atoms, ions, or molecules on to a surface. Absorption, in contrast, refers to the act of containing a fluid within an entire volume of a material, not simply its surface. If water clung only to the outside of a sponge, we’d say that the sponge adsorbed the water. Since water permeates the entire sponge, we refer to it as absorption.

According to IBM, a thermally powered adsorbing heat pump works by using residual heat at a temperature of 60C. Vapor is adsorbed from the radiator and compressed inside the heat exchanger, releasing the stored heat energy. The refrigerant material is forced out by an external supply of heat (possibly the waste heat collected from the systems themselves). Advantages of this system include the fact that it can use water rather than requiring expensive refrigerants. Two heat exchangers working in parallel are required to handle the task, and the system does apparently use some electricity — just not very much.

IBM has already demonstrated that its hot-water cooling system can function in an enterprise environment, and the company points out that the possibilities for this kind of heat pump are enormous in certain markets. Solar power plants, for example, produce huge amounts of waste heat — and Thrive could theoretically tap that energy to provide on-site cooling for attached buildings or offices.