Tuesday, February 15, 2011


Hawai`i geothermal critic embraces small geothermal

By Henry Curtis

Kristine Kubat and Shawn James-Leavey are meeting with Legislators at the State Capitol to discuss small geothermal and its application to Hawai`i Islands.

Kristine Kuba, the former editor of Big Island Weekly, was an outspoken critic of geothermal. Shawn James-Leavey was a writer with the Big Island Weekly and an activist with Big Island Voter Owned Elections advocates. Together they have formed a company which has the rights to the Power Tube [geothermal] Technology in Hawai`i.

Kristine Kubat fought against geothermal during the heyday of the anti-geothermal protests on the Big Island.

Home Power (1991): “The Big Island Rainforest Action Group, as part of its campaign to stop geothermal development in Hawaii, is sponsoring an alternative energy fair and concert to be held on the Big Island of Hawaii on June 28 & 29 1991. "Our group has taken an unconditional stand against geothermal here in the islands", says Kristine Kubat, spokesperson for the group. "That puts us in a difficult position because the State is promoting the use of geothermal as a means for achieving energy self-sufficiency. We're in favor of self-sufficiency in the broader sense, the extent to which we as individuals can reach out there and grab our own power. Geothermal development not only endangers our forests and jeopardizes the health of those living near proposed developments, it undermines the efforts of those working towards true energy independence. I guess it's up to us to validate the options.’”

Hawaii Business (1990): “Puna resident Kristine Kubat, an artist who is a member of the Big Island Rainforest Action Group, ‘Is geothermal good business? I think not. It's risky, it's unreliable, and there are no guarantees. When you look at alternatives which are good business, like developing energy-efficiency programs, you can't imagine why the state is having anything to do with it.’”

A good introduction to small geothermal would be really small (micro) geothermal.

Residential Heat Pumps (Micro-Geothermal)

A heat pump is a device which moves heat from one place to another usually using air as the medium.

“Geothermal heat pumps are similar to ordinary heat pumps, but use the ground instead of outside air to provide heating, air conditioning and, in most cases, hot water. Because they use the earth's natural heat, they are among the most efficient and comfortable heating and cooling technologies currently available.” Geothermal heat pumps qualify as EnergyStar devices and qualify for federal tax credits.

Residential Geothermal Heat Pump

While parts of the U.S. have ranged from 134 degrees (Death Valley) to negative 70 degrees (Montana), the temperature 6 feet below the ground varies from 45-75 degrees. In the winter, caves and igloos are warmer than the land around them, while in summer they are cooler.

A working fluid ("refrigerant") transfers the heat from one area to another. The working fluid is a substance which is a high temperature liquid when compressed, and a low temperature gas when it expands. Without external forces, hot substances give off heat to cool substances. If the ground is warmer than the house, then ground heat goes into the house. If the house is warmer than the ground, then heat goes from the house to the ground.

Small Geothermal

Doyle Brewington has spent the past 18 years developing and patenting a small geothermal power plant. Ten years ago Power Tube Inc. became one of the first to join the Clean Energy Incubator (CEI) which was launched by the Austin Technology Incubator.

The Power Tube is “a double-walled tube consists of four modules stacked sequentially. Geothermal rock heats the lowest module, essentially the boiler module containing a fluid. The second-lowest module is a turbine that turns the generator at the top of the Power Tube. Between turbine and generator is a condenser that cools the fluid. The cooled fluid then flows down the outside layer to begin the cycle again. The 25-meter-long prototype is being designed to generate 1 MW of electricity.”

EV World: "Much of the technology Brewington integrated into the Power Tube is new to the industry. ..."It took quite a while because Power Tube itself has four new technologies and ten different disciplines. Because of that, it took us pretty close to six years to get the patent. ...We don't need to estimate steam or pressure or anything like that. All we need to know is where the heat is. The other difference is the only thing you see on the surface at one of our installations is a ten meter by ten meter building with about a 3 meter roof. "

The first prototype Power Tube measures 85 feet in length and is 29 inches in diameter. The working fluid is a mixture of iso-pentane and iso-butane. The unique super-cooling condenser is powered by sound. The input heat must be at least 220 degrees Fahrenheit (104 C). It uses low to medium temperature heat, 110-200 C.

In a traditional geothermal power plant water plays the vital role of a heat conductor. The Power Tube “Argus” is a geomagnetic device that does not need water, steam or steam pressure to operate. The Argus units are designed for the 1, 5 and 10 Megawatt market.

The Power Tube uses a monocoque turbo-generator device. Monocoque is a construction technique that supports structural load by using an object's exterior, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork. The word monocoque comes from the Greek for single (mono) and French for shell (coque).

The Power Tube has 76 sensors that monitor temperature, speed, pressure, flow and seismic activity and then send the data to a satellite so it can be tracked anywhere in the world.


Sounds this could be another piece of the energy puzzle, and then again it could be a bust. The point is the alternative energy solution will not come from a single technology but a mix of technologies. Their will always be the next great invention that will provide more and cleaner energy for the state. At some point we are going to have to jump in the water. We are currently spending hundreds of billions of dollars invading countries for oil and paying too high a price in human lives. Geothermal on the big island seems like it could be one of a number of bridges until the next wave of technologies arrive. Are we going to do something to solve the energy crisis or are going to sit around spewing hot air.

Still, an 85 foot rigid PowerTube sunk into the ground in Hawaii may be very vulnerable to seismic forces with very high shear capability. One earthquake could potentially destroy all the value in the equipment because if it is bent or twisted inside its hole it may become impossible to extract or repair. In addition the working fluid could escape into the ground or atmosphere. Solar is better equipped to withstand these kinds of events, especially photovoltaic and solar hot water devices because the installations can be made to float on the movement of the earth's surface. You can't just look at these technologies as a theory. You have to look at how they are likely to perform over time.Because investments in these systems are for 25 years or more, that's a lot of time for things to go wrong. However the micro geothermal which is essentially a heat pump could be good for Hawaii because it can collect the heat in flexible underground tubes.

wind and geo-thermal. kinda funny that in fact one of the alternatives is ocean generating power. kinda funny as we are surrounded by ocean! and I hear nothing of development. mind you, all alternatives are expensive, and unpredictable. need people who are not prone to $$$$ as the primary objective. control of water, control of energy, control of farming, control of the "land"....a grand scheme, eh?

The blog is really nice one and full of information we appreciate the kind of information you have provided in this post.

Dear Jonathan,

THanks for raising these points.

Kristine here to answer the point raised about vulnerability to earthquakes. Actually the tubes are much longer, with between 140-180 ft in the ground. However, the well is engineered so that the device is not rigid within it but can move with the seismic activity. They are also fully equipped with sensors that monitor these occurrences down to .5 on the Richter Scale. At 6.5 the device shuts down while a back-up system continues to monitor the situation for 72 hours.

As for the fluids, a 10MW unit uses only 50 gallons of working fluid (isopentane, isobutane mix), circulating through 1" channels in numerous ropes of stainless steel tubing. Even if the doubled-hulled casing of the heat exchanger breaks open, the fluid is not lost to the environment but remains in the thick-walled tubing. But even if both walls of the exchanger are damaged and somehow each and every tube in the the device cracks open and the fluid leaks out, being highly volatile, it will evaporate as soon as it contacts the hot rock surrounding it. The only other fluid is a biodegradable thermal transfer oil (approved by EPA-approved for use in kitchens) that runs through the thermal riser.

Feel free to call me to talk more. Any more questions, keep them coming. My contact is on www.mokupower.com. a
aloha, kb

How close together can the wells be before one well starts cannibalizing the heat of the other? As in when a community needs more than 10 Mwatts of power.

Post a Comment

Requiring those Captcha codes at least temporarily, in the hopes that it quells the flood of comment spam I've been receiving.

Links to this post:

Create a Link

<< Home


page is powered by Blogger. Isn't yours?

Newer›  ‹Older