Investigations for geothermal systems

[Okiryu]

Hi, does anybody have experience doing subsurface investigations for geothermal systems? For example, I am looking for a way to provide recommendations for soil thermal conductivity or other ground parameters that may be required to design this system. Any feedback will be appreciated.

 

[epoxybot]

Here is a link that might be of interest: Advanced Testing Method for Ground Thermal Conductivity Link

 

[fattdad]

you may find information by looking at the design methods for, "Energy Piles." Folks have come up with circulating fluid piles in driven piles that engage the latent heat in the soil. Designing these necessitates information on the thermal properties of various soils. I think there are installations in Florida - perhaps elsewhere?

We (Virginia Department of Transportation) did one energy pile installation to evaluate geothermal deicing on a bridge deck. Can't recall the data sources, etc. It's just something that's being done/studied in commercial practices.

Also, there is current research on what happens to the soil. I mean if we rely on some soil strength via standard geotechnical practices, will the changing temperature, etc. affect any of these properties? Consolidation? Strength? Etc.

I think some of this was occurring at Virginia Tech over the last few years? Can't recall.

I would google energy piles though.

f-d

ípapß gordo ainÆt no madre flaca!

 

[racookpe1978]

Whatever source you get - and I have to stress I'm not familiar with the references likely available - you must be able to get the baseline water table height (max, min, average, and yearly change) and water table drought/flood conditions.

Heat transfer below ground for the basic rock/dirt won't change much with time. But will change a great deal week-to-week with how much water is "flowing" around the underground pipes.

 

[fattdad]

I don't want to comment about the water table and its affect on thermal properties. I just want to further comment on the nature of mechanical engineering. And, I'm not a mechanical engineer.

In typical HVAC design, the heat transfer occurs with air, which is considered an infinite, "Sink." The heat transfer does not affect the overall air temperature.

Below the ground it's different. The heat transfer makes a heated bulb, which is determined by various thermal properties. These thermal properties are influenced by all of the typical geo-variables, like soil type, soil density (void ratio), moisture content and expectations of temporal changes during the year.

I'm not a source for quantifying these variables. I just wanted to echo the thoughts about water AND all the other stuff.

I know it's frustrating that the geotechnical engineers have not really developed some generally accepted practice for geothermal studies.

f-d

ípapß gordo ainÆt no madre flaca!

 

[epoxybot]

You have probably already been to this site but here is a link to the "International Ground Source Heat Pump Association" Link

 

[Okiryu]

Thanks for your responses. The project is on hold now but it may come again later. That’s good since it gives time for some research. Will post again if I get any news. Thanks again!

 

[Okiryu]

Found an article from the Geostrata magazine (March/April 2012). f-d, also appears that Virginia Tech did some research on this (the authors are from there).

 

[fattdad]

yes, Tech has looked into several different aspects of energy piles, geothermal, etc. It's all very interesting!

f-d

ípapß gordo ainÆt no madre flaca!