Tapping geothermal: A molecular representation of a nanomaterial developed at Pacific Northwest National Laboratory that can improve the efficiency of geothermal power plants.
PNNL
Fluid extracts more heat out of low-temperature wells.
Researchers at Pacific Northwest National Laboratory in Richland, WA, say they've developed a superior type of heat-extracting fluid that could dramatically improve the economics of producing renewable power from low-temperature geothermal resources.
Lab fellow Pete McGrail says the liquid is used to absorb the heat from hot water that's been pumped from underground into a geothermal plant's heat exchanger. The liquid can potentially boost the rate of heat capture by 20 to 30 percent. Researchers engineered proprietary nanomaterials made up of metals linked by organic molecules. They found that adding the nanomaterials to a fluid such as hexane or pentane significantly enhanced the heat-trapping properties of the liquid.
"The hope here is that by improving the efficiency as much as we think we can, a project can become economic at much shallower depths," says McGrail. "You'd be able to deploy in what would now be considered marginal or uneconomic areas."
There's no shortage of geothermal energy under our feet. Drill deep enough and the heat is there. An MIT-led study from 2006 concluded that geothermal power systems have the potential to supply 100 gigawatts of power to the United States by 2050, but only if new drilling and rock-fracturing technologies and advanced plant designs emerge that could lower development costs.
Improved technologies are required because most economical geothermal plants today generate electricity by using steam or hot water directly from naturally formed high-temperature reservoirs, such as the Geysers field in California. The wells are relatively shallow, the water is 360 degrees Fahrenheit or hotter, and the rock is porous enough to sufficiently circulate water. Tapping geothermal resources in less-ideal locations requires drilling deeper and forcing fractures in rock, both of which add immense cost. It also means making the most of lower-temperature heat resources, which is accomplished using binary-cycle plants that extract and repurpose the heat from underground hot water rather than using the hot water directly to spin a turbine.
In these plants, water pumped into an injection well absorbs heat from hot rock and is pumped back up through a separate extraction well at temperatures ranging from 150 degrees Fahrenheit to 300 degrees Fahrenheit. The hot water is then passed through a heat exchanger, along with a fluid with a low boiling point. This fluid, which flows in its own closed loop within the plant, absorbs the heat from the water and flashes into vapor under high pressure. The vapor passes through a turbine, generating power, and is then condensed and recycled back through the loop.
An underground "heat nest" design avoids the need to fracture the rock.
DOE funds will help finance construction of a geothermal facility using advanced technology.
Carbon dioxide captured from power plants could make geothermal energy more practical.
If this improves efficiency for low temp geothermal, what is the possibility of adding this technology to the cooling outflow from nuclear...also make coal a little cleaner from a cumulative standpoint in that waste heat could effectively be used an alternative method of power generation from a plant that already has the electrical infrastructure in place. Also, what is the possibility of this technology being used in a ground loop system for a homeowner? I love reading this MIT site...What wonderful innovations are coming out for effective energy production and conservation...
Guest (vbstens)
There are several companies that have developed waste heat generated electricity. It certainly would be a step forward if their equipment became 20%-30% more efficient.
Wait a second!
There are hundreds of other applications for such a promising material like this which are much more realistic. Consider heat exchangers, "would this nano-material help reduce the size of heat exchangers by increase the thermal absorption rate?" I think so, but what do I know I only have a master in Thermodynamics.
I really think they should patent this molecule and license it to anyone at all. Moving everything towards the "Green Movement" is a way to get quick funding as a professor, but it is shorting the market potential of this new technology.
P.S. This is truly an exciting discovery.
Dr. Brian Glassman
Ph.D in Innovation Management from Purdue University
Graduate of Duke's Masters of Engineering Management Program
Graduate of UCF’s Master of Mechanical Engineering Program
by a very wide margin, most geothermal applications in the US are residential/commercial ground-source heat pumps. Would this potentially increase their efficiency (reducing cost)? Seems like it.
But before we go there, I think we must better understand the potential fate and transport of these materials in the subsurface. Massachusetts is already observing unforeseen water quality problems with conventional GSHP systems. And that is with materials we have a pretty good understanding of. Let's not march headlong into another mess like we did with PCB's in the 50's and 60's...
Very good point (I would spell your screen name but it is a bit long). Freon and Chlorofluorocarbon were great but very bad at the same time for the environment.
Again sell the stuff to labs for testing!
I know my Thermo lab at University of Central Florida would die to buy this stuff!
The more the merrier,
How about a simple Solar Rooftop system that can be used to collect heat and then pipe it into your home to lower utility bills?
In reply to the above comment about releasing these materials underground, the article clearly states that the advanced heat exchange material is in a closed loop, only water circulates below ground.
Study of the improvement of refrigerants is nobel. However there are already many very good materials available. Low temerature geothermal is being done already. Check out Chena Hot springs, in Alaska. They are on the cutting edge of 30 year old technology and it works. More development needs to be done. The heat source is a shallow thermal well, of 165deg. F.. This is producing power at less than one tenth the cost for a rural location in Alaska.
Sadly the greatest barier is monitary and political, not technology. Green can work, it is not going to make the rich richer. The technolgy is here, room for improvement, yes. We just need to get off our collective fat As*** and get it done. Bill
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50 Comments
Fracking
With all the issues with fracturing rock that are coming to light-- the poisons used, the compromising of our water resources, the problems of tectonic stability, sinkholes and other issues, that's not something we should be doing more of, it's something we should consider not doing at all.
Having said that, I'm glad someone's working on improving heat exchange technologies. Geothermal is a very promising area.
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