For around 15 years, we are using the ground under building to save energy. We heat or cool the ground, we store energy along the seasons, we shift heat or cooling production along nighttime for cheaper electricity, etc. This is done, for large projects, using water circulating in plastic tubes inserted in the ground, generally in poles drilled up to 100 meters in depth.
My Belgian colleagues were pretty excited about exploring geothermal usage for building in Vietnam and for tropical climate in general . After several weeks, their enthusiasm cooled down when we collected the first data from ground temperature: a constant 26 to 29 C, which is pretty high for supporting a proper building cooling system. In addition, there are no season, a constant cooling demand, high outdoor temperature and humidity levels. We quickly went from the uninformed optimists to the informed pessimists on the motivation curve!
Thinking about it again, it should have been the same when, back 15 years ago, we were challenged by heating building in Northern Europe, with -15 C in the winter, while ground temperature is around 16 C... Wasn't it the same doubt and skepticism ? Today, geothermal usage for building is getting popular in Europe and China. The question in those markets is not anymore about feasibility.
Let's keep faith. Shallow geothermal ( up to -100m) is new in S-E Asia. Very little has been done in tropical climate and data is scarce (especially water and ground temperatures at these depths). Also, demand for high cooling temperature remains insignificant as full convective (air) cooling is still the norm. Building air tightness is still little considered, even in advanced markets such as in Singapore.
For sure the way we may use the ground will be different compared to Northern climates. What are the opportunities under the tropics? Instead of storing heat load in the ground, we can imagine (pre)cooling the ground along nighttime, when electricity is significantly cheaper. We may also use vertical and horizontal transient water flows to regenerate the ground, or base our calculations considering the ground as an infinite heat dissipation medium instead of a energy storage tank.
And yes, there is one big change compared to 15 years ago: we have simulation tools, so it may go much quicker !
XP, Dec 2013
Further readings:
- A concept note we wrote about geothermal in Vietnam ( in English, in Vietnamese)
- One of our major project with massive geothermal usage
- Seasonal Energy Storage
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