As many of us who have spent our lives sitting inside offices know, “air conditioners powered by coal, oil or gas energy simultaneously increase emissions of greenhouse gases that heat the planet. Often installed on building facades, air-conditioning units also contribute to warming cities through the release of waste heat.”
Gero Rueter, the author of this piece, says that there is an alternative to air conditioning: “To address these problems, numerous major cities such as Paris, Munich, Hong Kong, Singapore, Dubai and Toronto are building large, efficient central cooling systems that consume less electricity.
There, they are used by hospitals, hotels, data centers and large buildings, and operate by pumping cold water through a network of pipes.”
Why is this type of system (of pumping cold water through a network of pipes) better than the conventional AC? Mr Rueter says that there are two different forces at play. Firstly, it is more energy efficient to cool water in one place rather than air in many different places: “In modern cooling technology as used in refrigerators, air conditioners and heat pumps, a gas is compressed in a closed system where it becomes a vapour. The process releases heat. The pressure is then reduced, causing the vapor to warm again and become gaseous. In the process, heat energy is extracted, creating a cooling effect.
Using various measures, large refrigeration plants can produce cold in a more environmentally friendly way than small plants.”
Secondly, municipalities can source cold water from a natural source thus eliminating the need to cool the water using energy: “Many municipal utilities, for example, use natural cold from rivers, groundwater, lakes or the sea. This also means such plants need far less energy.
“We try to use as much groundwater or city streams as possible as the main cooling supplier,” said Stefan Dworschak of Stadtwerke München, a city-owned communal company that supplies electricity to more than 95% of Munich’s households.
Like other district cooling networks, the one in the southern German city of Munich has ice storage facilities. Ice is produced there using large chillers, particularly at night, “when electricity consumption in the city is low, creating less pressure on the power grid,” Dworschak told DW.
The cold created at night is then released during the day to meet the needs for cooling in the buildings.”
However, it is not all sweetness & sunshine with this new cooling system. There are downsides to consider: “Like district heating networks, district cooling networks also have disadvantages. Investment costs are high, and pipes have to be laid underground in the city and connected to buildings. Both cooling and heating energy gets lost as it passes through long pipes in the ground.
These losses are particularly high if the water is either very hot or very cold when in transit.”
For very hot or very cold countries, one way to deal with the need to expend high amounts of energy on heating or cooling water is by using more insulation in buildings. So, for example, in Marcellus’ glass walled offices, if the insulation was better, less of the cooling would escape through the walls (and the outside heat would have a reduced impact the ambient temperature inside out office): “The most important factor for efficient cooling, however, is building insulation, says Wolfgang Hasper of the Passive House Institute in Darmstadt. The independent research institute calculates the energy consumption of buildings, organizes conferences and trains architects worldwide in energy-efficient design.
If buildings have good facade and roof insulation, windows with double or triple glazing, good shading and intelligent ventilation, “then the heat from outside doesn’t get in,” Hasper said.
Well-insulated buildings need up to ten times less cooling energy than a building with a lot of glass, no shading and no insulation. Hasper says that if insulated apartments in warmer regions were efficiently equipped with decentralised air-conditioning systems, it would lead to significant electricity savings.” [Underlining is ours]
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