Cutting Japanese carbon dioxide emissions

From gas burners to heat pumps

In Japan, most people use gas burners to heat the water in immersion heaters. In the shadow of our domestic climate debate, however, some two million Japanese households and companies, with a little help from Norway, have started to heat their water in a greener way.

The key to the change is heat pumps based on technology that originated in pioneering work done at SINTEF and NTNU.

Back to nature

Heat pumps are well-known as a way of saving electricity for heating buildings. In most heat pumps, the heat is transported around the system by chemicals. However, when they are specially designed to do so, they can instead use CO₂, one of nature's own substances, saving power even while they generate steaming hot water.

Green paradox

Many people find it paradoxical that the notorious greenhouse gas CO₂ can be used in heat pumps to reduce emissions of the same gas from gas burners. Used in a heat pump, however, CO₂ does not contribute to the greenhouse effect, even if it should leak out into the atmosphere, since the gas that circulates in the heat pump is "borrowed" from industrial flue gases that would otherwise have been directly released in any case.

Climate benefits in Japan

"Without the CO₂ heat pumps, these two million Japanese users would have had to heat their water by burning gas. Now they use some electricity instead to drive their heat pumps; true enough, this is generated by fossil-fuel power plants, but because heat pumps are so energy-efficient, the environmental accounts end up in the black. Our calculations show that heat pumps cut Japanese CO₂ emissions by 1.1 million tonnes in 2009," says senior scientist Petter Nekså of SINTEF Energy Research.

In that same year, Norwegian emissions amounted to 42.4 million tonnes of CO₂. The reduction of 1.1 million tonnes in Japan is thus equivalent to 2.6 percent of these emissions, and to 2.5 percent of the somewhat higher figure for 2008 (44.2 million tonnes).

Problematical chemicals

The story of the Norwegian CO₂ heat pump started one day in the late 80's, when ozone-destructive chemicals were still circulating in heat pumps and refrigeration units. By the 1997 Kyoto Treaty, the international community had agreed to eliminate these substances, and the chemical industry was quick to launch a new chemical to replace them. Unfortunately, the new compound turned out to have a powerful greenhouse effect. In fact, leakages from refrigeration units and heat pumps are currently equivalent to ten percent of the global CO₂ emissions from fossil-fuelled power stations.

Drinks chilling cabinets and freezing compartments

The CO₂-based technology has also been advancing into the refrigeration field, primarily in the retail area, where once again the point is to avoid using current chemical-based systems so that any leakages will not add to the greenhouse effect. A few years ago, Coca Cola announced that it intends to adopt CO₂ in its in-store soft-drinks chilling cabinets all over the world.

The CO₂ technology is also being introduced into chillers and freezer units in food stores. One of the first chilling units to be entirely based on CO₂ was installed by the ICA chain in its Tempe store in Trondheim five years ago.