Sunday, July 26, 2009

How does the earth’s heat produce geothermal energy?

Geothermal energy is a renewable energy source. Essentially the source of geothermal energy is the radioactive decay of elements deep within the earth. If aquifers are coincidental with geothermal, hot geysers will form that spout steam into the air. If no aquifers are present the hot spot is called dry geothermal. Iceland leads the world in the capturing of geothermal energy to heat homes, offices and factories as well as generating electricity from this renewable energy source. Chevron the San Francisco based oil company claims to be the world’s largest geothermal electricity company. Chevron has large projects in Indonesia and the Philippines which are two countries with significant geothermal potential.

California leads the US in the production of geothermal electricity but there is tons of interest in geothermal in Utah, Nevada, and other states in the intermountain area. The method to extract work from the geothermal source is pretty simple. If an aquifer is present and the geothermal source is hot enough to produce steam the steam is simply run through a turbine and the turbine is connected to a generator that produces electricity. If the temperature of the geothermal sourceis not sufficient to produce pressurized steam then an alternate working fluid is used to power the turbine. The alternate fluids have boiling points lower than water (steam) and will also be routed through a turbine in their vapor state. Much research is being undertaken to invent the optimum working fluid with thermodynamic properties to optimize the amount of electricity that can be generated. Often the process of these alternate working fluids is referred to as an Organic Rankine Cycle. Organic means the working fluid is carbon based and Rankine was a thermodynamicist who has a temperature scale named after him. This link explains the Organic Rankine Cycle further

Ormat technologies traded on the NYSE as ORA is a leading developer of the Organic Rankine Cycle technology. United Technologies is another and this makes sense since UTX also produces Pratt and Whitney turbines. Just a few weeks ago a group working at the Pacific Northwest National Energy Lab discovered a method to use nano particles to agglomerate organic Rankine fluids such as hexane or pentane to improve the performance of geothermally derived heat for electric power generation. This link provides further details I have no doubt that geothermal energy will play an increasing role in power generation in the USA, and elsewhere. Geothermal is a source of renewable energy that can operate on a 24 by 7 basis. Wind and solar are very intermittent and only provide power for some 25% of the hours in a year. Some recent research out of NYU Stern Business School by Mellissa Schilling ranks geothermal as well as wind as the technologies that should attract research money as they are likely to deliver the best improvement in cost of power generation. Solar PV and Solar Thermal according to these researchers will not deliver the cost improvement and research dollars spent on these technologies will likely prove futile.

I like geothermal simply because the word rings nicely in my head. Chevrolet used to market a mini car named a Geo Prizm which was actually a Toyota Corolla manufactured in the factory GM and Toyota shared (NUMI) in Fremont California. GM in bankruptcy has pulled out of the joint venture and just this week it is pretty much assured that Toyota will close the NUMI plant. Numi is the only auto assembly plant on the US West Coast. The left coast will be left out of the auto race, except perhaps Tesla who will get almost half a billion of government money to build their plug in sedan. Here is an idea. Toyota should buy Tesla and use NUMI for the plug in and the feds should keep our tax dollars for fixing potholes that otherwise will destroy vehicles.


  1. Ja, Mr. Co-developer of the Altamont Pass wind farm, Randy Tinkerman also thinks we should be doing more to exploit geothermal.

    But you didn't mention anything about geothermal being used in ground source heat pumps or direct source of heat applications in this blog blat, Lindsay. How come?

  2. I limit the blog to about 500 words as that is what the local newspaper want. How about I do a second episode on heat pumps and direct heating by geothermal next week? Thanks Kimgerly Lindsay

  3. GeoThermal Power has a significant share of the current Philippines'Energy Mix. Its share could increase as new investments develop even smaller GeoThermal Sites. Surprisingly though, my Filipino GeoThermal-Specialist declares, that knowing much of the "unpredictables" relative to the GeoThermal Industry, he would prefer investing in Hydro Power.