Low Enthalpy Geothermal Resources

A leading renewable energy site recently posted a news item  “Low-Temperature Geothermal: Digging for Its Vast Opportunity”

A few of the geothermal experts commented thus:

“We need to have better exploration and drilling technologies because that’s one of the biggest hurdles to geothermal prospects.”

“We must look at new technologies on all fronts – both exploring for new resources and for developing and operating those new resources — so we would like to see additional funding from the DOE [U.S. Department of Energy] in the geothermal technologies program.”

“a continued focus and expansion of trying to utilize lower-temperature resources  so that we can continue to bring what was once thought uneconomical and unattractive for geothermal, but often more abundant. These low-temperature resources actually can produce utility-scale power production.”

The need and the available low enthalpy geothermal resources, especially in the non OECD  countries  has already been brought to focus in a book way a back in 2008 in a book entitled ‘Low Enthalpy Geothermal Resources for Power Generation” ( by D Chandrasekharam and J Bundschuh, CRC Press, 149 pages).

The main aim of this book is to bring to the geothermal community, the huge quantity of available low enthalpy geothermal energy resources lying untapped in all the developing countries, the method to tap this energy sources and the advantages it will have in mitigating global climate change, reduction in carbon dioxide emissions and uplifting the socio-economic status of the rural population.

The greatest development is expected in the  non-OECD Asia where the electricity generation is expected to be of the order of 10,186 TWh in 2030 from the current 3518 TWh. This correspond to an annual average increase of 4.2 %. In non OECD Asia India and China have the highest absolute national electricity generation growths.

Low enthalpy geothermal resources occur in a wide range of geological and tectonic regime. Some time they are close to a high enthalpy domain or occur as large exploitable  independent resource. They also occur as geopressured systems within large sedimentary basins and or petroleferous formations. With the developments taking place in drilling technology and heat exchanger technology, EGS may also be able to provide low enthalpy fluids that can be utilized for power generation using carbon dioxide as working fluid. Such low enthalpy EGS resources occur in large areas in developing countries.

Although they were considered economically not viable in the past, considering the constant build-up of CO2 in the atmosphere, CO2 reduction strategies countries have to adopt and compelling situation for a constant industrial growth by developing countries, policy makers are and planners are encouraging development of low enthalpy geothermal resources. Now it is possible to generate power from geothermal fluids with temperatures as low as 82 °C.  According to estimates  use of geothermal fluids with temperature of about 100 C will increase the energy available for electricity generation from 11200 TWh per year to 22400 TWH per year with the advancement taking place in binary power generation technology.  Thus the potential of low enthalpy geothermal resources has been underestimated worldwide. Compared to other low CO2 emission sources like wind and solar, geothermal supplies base load power, does not require storage systems and back-up power facility. Once commissioned, the system runs for several years with proper maintenance. In fact for many countries are using low enthalpy geothermal resources for recreation, balneology, space heating, dehydration etc (direct applications). Now these countries can evaluate their low enthalpy resources for power generation. 400 000 TJ/y of geothermal energy is in use for direct application world over according to a recent publication by the World Geothermal Congress, 2010 held at Bali in April 2010. Countries such as those like the Caribbean islands ( Nevis, st.Kitts,Montserrat, St. Lucia etc) according the book mentioned above import oil and gas for electrification even though these countries have large low enthalpy geothermal resources.  This is true even with countries inEastern Africa. Those located within the rift environment with plenty of geothermal energy sources, depend on imported oil  to support their electricity demand and increase the GDP of the country as well as that of rural regions.

As published earlier, there are two energy sources, one the Sun and the Earth. We need a media to convert Sun’s energy to electric power. In the case of Earth’s we need small generators. Media to convert Sun’s energy is expensive while small generators can be bought off the shelf at a competitive cost. Perhaps when oil wells dry up mankind will certainly have to depend on this source, for certain!!