[Whitecrab]

Oh, I forgot to mention: I'm not sure geothermal can be used everywhere. I remember hearing in my geology class there are concerns about using it in fault zones: water can enter fault cracks in the earth and it's feared this may provide fault lubrication and increase the number of earthquakes.

[Yamaha_R6]

Water working as a lubricant???? I don't think so. Ever tried doing it in a hot tub? Water does anything but lube. Or so I have heard...........

[Dvanharn]

link"The Geysers," north of Santa Rosa, California is the largest developed geothermal generation facility in the world. The powerplants there have produced up to 5% of California's electricity in a single year (1999). Santa Rosa just finished up a very expensive ($187 million) project to transport treated water from the sewer plant to recharge the steam wells at the Geysers. The first link below describes that project.
link

This link is an absolutely excellent VERY short introductionto the potential and limitations of geothermal power. link
This last link is a review of California's current geothermal development and it's potential. link

Yamaha, there may be a lot of heat down there, but how do you exploit it? The thermal conductivity of rock is very low, and the best geothermal fields are natural highly fractured deep regions with high heat. But even then, recharging of water for steam is necessary, and you are cooling the rock in the region, so it still is not absolutely renewable, and many geothermal fields taper off over time, just like oil fields.

Yes, there is potential for a lot more geothermal power generation, but it has it's limits too, both financially and technically.
Unless you are a lot smarter than the scientists and engineers dedicated to developing and exploiting geothermal energy, and know somethng they do not, your grandiose plan may be a bit exaggerated. (Wishing I had a small geothermal steam source on my property)[/url]

[Leanan]

The Big Island does have a geothermal plant. It also has an ocean thermal plant. However, they still get most of their electricity from oil. The geothermal plant was so expensive to build that there are no plans to build any more. It's also proved noisy and polluting.

Geothermal is not practical elsewhere in Hawaii. Well, maybe Maui. But most of Hawaii's population lives on Oahu, which doesn't have geothermal resources. At one point, they were considering running an undersea cable from the Big Island to other islands, but it proved too expensive to be practical.

Leanan <-- raised on the Big Island

[Graeme]

I copied this from the IGA newsletter June 2003:
Status of Geothermal Energy Amongst the World´s Energy Sources (Part I)Ingvar B. Fridleifsson, United Nations University
- Geothermal Training Programme, Orkustofnun, National Energy Authority, Iceland
Abstract: The world primary energy consumption is about 400 EJ/year, mostly provided by fossil fuels (80%). The renewables collectively provide 14% of the primary energy, in the form of traditional biomass (10%), large (>10MW) hydropower stations (2%), and the new renewables (2%). Nuclear energy provides 6%. The World Energy Council expects the world primary energy consumption to have grown by 50-275% in 2050 depending on different scenarios. The renewable energy sources are expected to provide 20-40% of the primary energy in 2050 and 30-80% in 2100. The technical potential of the renewables is estimated 7600 EJ/year, and thus certainly sufficiently large to meet future world energy requirements.
Of the total electricity production from renewables of 2826 TWh in 1998, 92% came from hydropower, 5.5% from biomass, 1.6% from geothermal and 0.6% from wind. Solar electricity contributed 0.05% and tidal 0.02%. The electricity cost is 2-10 US/kWh for geothermal and hydro, 5-13 US/kWh for wind, 5-15 US/kWh for biomass, 25-125 US/kWh for solar photovoltaic and 12-18 US/kWh for solar thermal electricity. Biomass constitutes 93% of the total direct heat production from renewables, geothermal 5%, and solar heating 2%. Heat production from renewables is commercially competitive with conventional energy sources. Direct heat from biomass costs 1-5 US/kWh, geothermal 0.5-5 US/kWh, and solar heating 3-20 US/kWh.
Keywords: geothermal, electricity, direct use, comparison of renewables, energy prices.
1. Introduction: With increasing awareness of the detrimental effects of the burning of fossil fuels on the environment, there has been an increasing interest world wide in the use of clean and renewable energy sources. It is important for the proponents of renewable energy sources to be aware of the outlines of the world energy use. The present paper starts with a description of recent energy forecasts for the world in the new century and the increasing role that renewable energy sources are expected to play in the world energy mix. The forecasts referred to here have been initiated by the World Energy Council. The present use of energy sources is summarised. A comparison is made of geothermal
energy with other renewable energy sources based on data presented in the World Energy Assessment report [1] prepared by the United Nations Development Programme, the United Nations Department of Economic and Social Affairs, and the World Energy Council. The present paper is largely based on two review papers recently published by the author [2], [3].
2. World energy forecasts: Amongst the top priorities for the majority of the world´s population is access to sufficient affordable energy. There is a very limited equity in the energy use in the different parts of the world. Some 70% of the world´s population lives at per capita energy consumption level onequarter of that of W-Europe, and one-sixth of that of the USA [4]. Two billion people, a third of the world´s population, have no access to modern energy services. A key issue to improve the standard of living of the poor is to make clean energy available to them at prices they can cope with. World population is expected to double by the end of the 21st century. To provide sufficient commercial energy (not to mention clean energy) to the people of all continents is an enormous task.
The World Energy Council (WEC) has presented several scenarios for meeting the future energy requirements with varying emphasis on economic growth rates, technological progress, environmnetal protection and international equity. All the scenarios provide for substantial social and economic development, particularly in the developing countries. They provide for improved energy efficiencies and environmental compatibility. During 1990-2050, the primary energy consumption is expected to increase by some 50% according to the most environmentally conscious scenario and by some 275% according to the highest growth rate scenario. In the enviornmental scenario, the carbon emissions are expected to decrease slightly from 1990 levels. The high growth rate scenario is expected to lead to a doubling of the carbon emissions [5].
The scarcity of energy resources forecasted in the 1970s did not occur. With technological and economic development, estimates of the ultimately available energy resource base continue to increase. Economic development over the next century will apparently not be constrained by geological resources. Environmental concerns, financing, and technological constrains appear more likely to limit future development.
In all WEC´s scenarios, the peak of the fossil fuel era has already passed. Oil and gas are expected to continue to be important sources of energy in all cases, but the role of renewable energy sources and nuclear energy vary highly in the scenarios and the level to which these energy sources replace coal. In all the scenarios, the renewables are expected to become very significant contributors to the world primary energy consumption, providing 20-40% of the primary energy in 2050 and 30-80% in 2100. They are expected to cover a large part of the increase in the energy consumption and to replace coal.
It is a very legitimate question to ask whether these scenarios are realistic. Table IV shows the technical potential of renewable energy resources. The technical potential is the yearly availability of the renewable resources.
There is no question that the technical potential of the renewables is sufficiently large to meet future world energy requirements. The question is, however, how large a part of the technical potential can be harnessed in an economical, environmentally and socially acceptable way. This will probably vary between the energy sources. It is worth noting, however, that the present annual consumption of primary energy in the world is about 400 EJ (Table IV).
References
1. WEA(2000). World Energy Assessment: energy and the challenge of sustainability. Prepared by UNDP, UNDESA and the World Energy Council. United Nations Development Programme, New York, 508 pp.
2. Fridleifsson, I.B. (2001). Geothermal energy for the benefit of the people. Renewable and Sustainable Energy Reviews, 5, p. 299-312.
3. Fridleifsson, I.B. (2002). Energy requirements for the new millennium. In: Human development and the environment: Challenges for the United Nations in the new millennium, p 220- 233. United Nations University Press, Tokyo.
4. WEC (1993). Energy for Tomorrow's World, St. Martin's Press, USA, 320 pp.
5. Nakicenovic, N., A. Grabler, and A. McDonald, (editors) 1998. Global Energy Perspectives, Cambridge Univ. Press, 299 pp.
Hydropower 50
Biomass 276
Solar energy 1575
Wind energy 640
Geothermal energy 5000
TOTAL 7600
Table IV. Technical potential of renewable energy sources
Source: World Energy Assessment [1].
My question is: Why doesn't ASPO consider geothermal as a renewable energy source?

[Devil]

I can't answer for ASPO, but geothermal power, in industrial quantities, requires geological conditions that are present in only a few places in the world. It certainly cannot be considered as a general panacea for energy shortage.
However, where the right conditions exist, Iceland being the example par excellence, then yes, let's exploit it to a maximum.

[0mar]

Geothermal can't be controlled and modeled for any place on earth. Rather, we have find places on earth and then build around it. It all depends on geology as Devil said. We do not have the drilling technology to create geothermal vents.

[Graeme]

Here I beg to differ with the replies given because I have some expertise in this area. In addition, if you read the newsletter, the author says near the bottom of the article and in Table IV that there is considerable potential for geothermal to supply our energy needs later this century. Many countries are already exploiting their geothermal resources for electricity generation. These include nearly all countries in the Pacific Rim but also in central and eastern Europe and East Africa. This development is only going to accelerate as oil becomes more expensive. Also there is some potential in other countries to extract hot water at shallow depth for domestic heating. I am surprised that ASPO does not even consider geothermal as a renewable resource.

Graeme Scott

[Devil]

OK, put your brain where your mouth is and show us your expertise. Please provide a table of every country generating geothermal electricity, the power capacity thereof and the fraction this represents of the electricity consumption within the country, with references.

[Graeme]

OK This is not an exhaustive survey but try the World Energy Council: link
Scroll down to view by fuel and select Geothermal and click GO
Scroll down and look for Table 12.1 Hope this helps

[Frank]

I believe that there are "challenges" to using geothermal directly unless you happen to live in one of those special places, but that indirect use (ex. extraction via heat pumps) could play a more significant role in the future.

For example, it's not uncommon to see electric heat in some places in Canada (I'm thinking Quebec and New Brunswick specifically) - one reason is their proximity to cheap hydro power. Electricity is cheap and abundant in these areas. If heat pumps were to be used instead, electricity usage would be reduced by a factor of (?) 3 or 4 and this would then be available to (a) offset generation elsewhere by coal or NG or (b) recharge electric vehicles (battery or Vd-redox cells). Either use would help offset fossil fuels.

Maybe my terminology isn't correct and I certainly don't have a good idea of how much potential there would be, but I've lived in Quebec and have been looking at houses in NB and 100% electric heat is quite common. I like the idea of using electricity to leverage what mother earth is already making available to us. After all the earth is the largest solar collector around.

[Mercani]

Somewhere I read that Russians were attempting to drill 6 kilometers into the Earth for research.
Go down a few more km's and you would hit magma. Is it called Earth's mantle? Basically very hot stuff that's coming out of vlocanoes.

If we can develop drilling technology, geothermal could be useful all around the world.
Basic idea: Drill 2 very deep wells side by side. Somehow connect them at the bottom. Pour cold water into one of the wells and get hot water from the other one. Use the energy to produce electricity, or heat your home, etc. This system is already being used for heating and cooling, but it's expensive investment. To heat your home you don't need to drill very deep indeed.
I think geothermal will be a big energy source in the future, once we advance drilling technology. Maybe we can use that bunker-buster bombs for drilling purposes.

[Antimatter]

Hot dry rock geothermal. http://hotrock.anu.edu.au/]link
Same deal, only useful in areas with the right geological conditions, though it may be more widely applicable than conventional geothermal.

Based on temperature data from more than 3,500 boreholes, mostly oil and gas exploration wells, the Australian resource of hot dry rock has been quantified to the five kilometre level. The resulting image map of temperature at a depth of five kilometres is shown above.
Conservative assumptions were also made in calculating the size of the resource, in the following terms:
* the resource was defined by a minimum temperature of 225ºC at a depth of 5km
* the resource was assumed to be only 1.5 km thick with temperature ranging from 225ºC at the bottom to 165ºC at the top (ie average temperature 195ºC)
* higher temperatures, known to exist at some locations, were ignored in the calculation
* 165ºC was the assumed average temperature when the resource would be exhausted

The resulting estimate of energy available for electricity generation was 23 million petajoules (1 petajoule =1015 joules) or 7,500 years of Australian energy consumption at the current level. Over 80% of this resource is located in the Eromanga Basin, an area covering the NE corner of South Australia and the SW corner of Queensland. The distribution of the resource is given in Somerville et al (1994) [ERDC Report 243]: Figure 6 and Table 1.
About 11% of these energy resources (2.5 million petajoules), or more than 800 times the current annual demand for electricity in Australia, are thought to be in granite rock which is the most favoured host rock for heat extraction. Granite bodies are typically large in size, uniform in properties, and suitably cracked or jointed for the formation of heat mining reservoirs. As granite has a relatively low density, the presence of subterranean granite bodies can be inferred from geophysical surveys using microgravity measurements. This applies particularly to high heat producing granites, so in Australia, the occurrence of a gravity low together with high temperature in the Earth’s upper crust is generally indicative of a buroed granite hot-rock resource.

Wells are being drilled for a pilot plant at the moment. Should be cost competitive with fossil fuels, I'll beleive it when I see it though.

[Devil]

I have heard, but cannot substantiate it, that there is a problem with cracked impermeable rocks, as opposed to permeable sedimentary rocks. The closed circuit causes inceasing amounts of silicates to dissolve. The solubility at 200°C is much higher than at 100°C or whatever temperatures and can achieve greater than saturation in the downpipe, causing precipitation. This can bung up the cracks around where the downpipe enters the stratum, over time. With multiple cracks typically less than 5 mm wide, the pressure/flow characteristics change in a timescale of a few years and new downpipe boreholes become necessary a few tens of metres away.

I can easily visualise the problem. Where we live, we are on metamorphised pillow lava, with a similar crack structure. Our next-door neighbour bored a 180 m well in 1999 for irrigation, well below the water table level. When it was first bored, the infiltration was at 4 m3/day. Today, he barely gets 3 m3/day, despite a succession of heavy wet seasons over the last three years causing the water table to rise slightly. The well expert has ascribed this to the opposite effect: as the water infiltrates through the cracks, it reaches the air in the well and there is some evaporation, causing dissolved minerals to bung up the "outlets". Normally, the air is saturated, but, as he pumps the water out, twice a day, there is quite a down-draught of dry air from the surface (the borehole diameter is about 20 cm). Apparently, so I am told, those who live in a sandstone area, about 20 km from here, don't have the same problem because, as one pore bungs up, there are hundreds more to replace it.

[Antimatter]

I have heard of that issue too, not sure what they plan to do about it. If it takes a number of cycles for the concentration to build up to high levels the water could be boiled off and recondensed every so often. Perhaps a small amount diverted and distilled constantly so as not to interupt the turbines, say 95% to the heat exchanger and 5% allowed to boil and recondense. I have no idea if this would keep the mineral concentration low enough, just guessing. Alternatively a hydrocarbon (or veggie oil ) could maybe be used but too much would probably be lost into the ground.

[JBinKC]

I think it will be a key future energy resource for heating needs because it conserves space. For power needs it will be a regional power source where the mantle is near the surface.

[Triffin]

I like this concept too ..

http://www.ees4.lanl.gov/hdr/

Triff ..

[nero]

The real question I have about alternatives is in what order are they likely to be used. Is HDR likely to be cheaper than shale oil? If not then it is pretty irrelevant since we will exploit the shale oil before we exploit the HDR. This all assumes that there is no "hard landing" and we still have a society in the future able to exploit these difficult resources.

[formandfile]

Slap me if OT or if covered elsewhere, but were the efforts to 'recharge' The Geysers Hydrothermal plant over in California via pumping them with treated wastewater successful? Or has that not be attempted as of yet?

[BastardSquad]

OK,so this is probably going to sound reallllyyy stupid.
One of the largest (if not the largest) volcanic caulderas in the world is here in the States---Yellowstone National Park!!!
How much energy do ya figure we could siphon off that baby if we could safely tap into it???