Korean Professor Seung Rae Lee has high hopes for geo-thermal energy storage.
Visit by a Geo-Thermal Energy Pioneer
Korean Professor Seung Rae Lee has high hopes for geo-thermal energy storage.
Imagine that we could store the excess heat from summertime and use it to warm up buildings during winter. According to trials and simulations conducted by CERE PhD student Lisa Pasquinelli in cooperation with Visiting Professor Seung Rae Lee this is not unrealistic.
After obtaining both his Masters and Ph. D. degrees at Stanford University, USA, Seung Rae Lee returned to a position at the Korean Advanced Institute of Science and Technology (KAIST) in 1989, soon to become head of the institute’s group on geotechnical-engineering.
“I guess you can say that I have become a pioneer in geo-thermal energy.”
By March 1st 2014 Professor Lee came to DTU as part of a one-year sabbatical, which will also include a stay at the Technical University of Munich (TUM).
The stay at DTU has allowed him to join the geothermal energy storage activities at CERE led by Professor Ida L. Fabricius.
“Being a geologist, Ida focusses at rock structures at large depth, while I, as a geotechnical-engineer, usually study clay and other types of soft soil near the surface. In geo-thermal energy storage we have found a field in which our competencies can be joined optimally,” says Professor Lee.
Geology is being overlooked
Professor Lee adds that both geology and geotechnical-engineering should influence the field more strongly than today:
“The typical geo-thermal practitioner would be either a mechanical engineer or a civil engineer specializing in buildings. Both groups tend to overlook the importance of the local geology when designing a geo-thermal system.”
The key factor in this context is the thermal conductivity of the ground, which may vary a great deal compared with an average type of ground. This obviously needs to be taken into consideration:
“If you have conditions with a lot of heat being lost to the surroundings, it would be a waste of money to design a thermal system that could work under much better conditions. And vice versa: if you plan for good conditions but in fact face poor conditions your system will not be adequate.”
Using a combination of commercially available software and original software developed in his group at KAIST, Professor Lee hopes to be able to simulate easily and accurately what would be the required geo-thermal design for a given location.
“We need a big mouth”
The simulations based on Danish trial results have been encouraging. However, good results require optimal administration of the site, he stresses.
“The natural temperature in the aquifer we looked at is 50-60 degrees C. We obtained the results by injecting water at a temperature of 70 degrees C. If you try to inject water at a higher temperature, your relative loss will increase. Further, you need to inject the water not all at once but with some intervals.”
A further encouragement was the fact that it was possible to scale up volume with just a slight decrease in efficiency.
Further, the technology offers a very cheap and almost CO2-free energy source, since it is often possible to utilize warmth generated by the sun during summertime, or excess heat from other activities, or geothermal energy. Why then, do we not see a booming interest in the technology?
“The Korean government, for instance, is highly committed to green energy, but wind energy and solar energy take almost all focus. The situation in Denmark seems to be quite similar. In my opinion the potential in geothermal energy is actually larger than several other clean energy technologies, but maybe we need a “big mouth”, so everybody gets the message,” Professor Lee remarks smilingly.
Korean prestige project
While the efforts at CERE led by Ida L. Fabricius are focused on heat storage in deep aquifers, Professor Lee also takes an interest in near-surface systems.
Just as in Denmark, underground storage of warm water is being used in some new Korean buildings. By the way some of these systems work both ways – also supplying cooling when needed.
“One great advantage is that installation costs are very low as one may build in the storage units in the piles which are needed anyway for the foundations of new buildings.”
In this respect Professor Lee has high hopes for a current prestige project in South Korea. The “Lotte World II” in capital Seoul will become the tallest building on the Korean peninsula once completed.
7.7 per cent of the energy consumption of the 123-floor building is to be met by clean energy sources. This may not sound too impressive in itself, but Professor Lee notes that the majority of this clean energy is geothermal, outweighing the joint contribution from wind and solar energy.
“The project could have a large impact when it comes to creating attention around the potential in geo-thermal energy storage.”