Kyoto – A Perspective (Part 22)

Posted on Wed 05/07/2008 by



These two processes here actually might have some merit, so rather than include them with the processes in the previous article, I’ve included them separately here.

There are two actual methods of operation in this Geothermal process.
The first is the extraction of hot water and steam from the vicinity of volcanic sites, and you would be aware of hot springs where the steam bubbles to the surface through hot mud. These sites are closest to the surface, and the steam from them is currently being used to generate electricity effectively in Iceland, New Zealand, and in the US as well, albeit on a small basis for all these plants.

The second process is quite an interesting one, and even though it sounds like Science Fiction, it is actually being made to work by a company in Australia.
The Company is GEODYNAMICS. The two graphics and the text are from their website. It’s a large website, but navigating across all the tabs shows some very interesting information, further highlighting that it’s not the green crackpots who produce viable alternatives, but real, working engineers. The acronym HFR stands for Hot Fractured Rock.

The HFR geothermal process is a closed system, with two loops. The first loop uses water to extract heat from the buried hot rocks. The simplest hot dry rock power plant comprises one injection well and two production wells. Cold water is pumped under pressure down an injection well where it flows through an underground heat exchanger in the hot granite. It is then returned to the surface through production wells. Because this loop operates under pressure, the super heated water remains a liquid, with no steam generated. This water heated to greater than 200 degrees C then returns to the surface under pressure. The high temperatures of the hot water are transferred to the geothermal power station loop via a heat exchanger. This second closed loop uses liquids with a low boiling point (similar to those used in fridges and air conditioners) and this drives a turbine system. The cooled geothermal water returns to the underground heat exchanger where it is reheated. The twin loop system is known as a binary geothermal power plant.

This has real prospects of actually being able to provide good baseload power. Deep in the Earth are layers of solid rock heated by the Mantle, that large layer between the Earth’s Crust and the Earth’s Core. This is not similar to the geothermal activity around the volcanic areas and hot springs of the other process because this HFR area is stable and not close to the surface where it can result in eruptions of any sort. There is a need for a three kilometre layer of sedimentary rock above the heated Granite. Old and expired gas wells provide perfect places for this process, because the vacant space (where the gas was) already exists, and this is the space the pressurised water is pumped into. There may be some conjecture that over time, the rock may cool, but consider this. So far exploration has found suitable areas where this process can be used, here on the Australian Continent. Those areas currently stand at around the same area as the whole State of California, and some areas are quite vast, so the inherent heat would be difficult to dissipate, if at all. The inherent problem is evaporation to a degree of the water so some might need to be brought in, but the only part above the surface is in the pipes leading to the heat exchanger, so evaporation is not the problem you might perceive when viewing cooling towers at other plants. The infrastructure would also need to be built, but the process is a lot cheaper than nearly every other alternative.

This actually is a viable alternative, and it’s already producing electricity.

For so long this gas was just an added problem in the coal mining process itself. Now, engineers have found a way that it can be used. Coal seam gas (CSG) is associated with every coal mine in existence. Remember back to stories from long ago how underground coal miners used to take birds in cages down the mines as an early warning of the presence of the volatile and highly explosive gas. That gas is coal seam gas, and surprisingly, it actually has some good prospects. An earlier process I mentioned was the use of LNG to fuel combined cycle turbines. CSG can be used in the same manner, and naturally enough, is as readily available as coal itself, because wherever there is a coal mine there will be CSG. It has an advantage over LNG in that it produces less carbon dioxide at the well head because the carbon is sequestered in the coal itself, and this is released during the burning phase, so using CSG produces less carbon dioxide at the plant than even the LNG does, and only 5% of the CO2 produced by coal fired power plants themselves. It is however still a fossil fuel. It has been suggested that this could prove to be a reliable interim replacement for coal fired plants while a reliable renewable alternative is found. Currently in Australia, CSG is being used to fuel a combined cycle power plant that produces a rated maximum of 635 MW of power, supplying power to an estimated 400,000 homes. It is in the range of intermediate baseload power and is still best used in the same manner as the other combined cycle turbine, that of peak power requirements. The CSG will also be piped to the mineral exporting large port of Gladstone where another plant will be constructed and run from this gas

However, why I wanted to leave this process to a separate article is that it has thrown up an interesting development. One of the major power companies here in Queensland Australia is the developer of this process of using CSG for the purpose of running a power plant. Because of the drastically reduced greenhouse gas emissions, there is the perception of being ‘green’ by its very nature.
Since news of this plant using the CSG process broke, a huge power company from the UK has launched a multi billion dollar takeover bid for the company.
As much as you think of this as understandable, consider something you may not have thought of.
Remember Kyoto. I have to occasionally refer back to it so we don’t think we’re being sidetracked.
What arose from this was that companies will have to start paying carbon tax or offsetting their carbon footprint. One way to achieve this is for the company to show it has interests in environmentally conscious things. Because this use of CSG is a lot ‘greener’ than most other power plants currently in use, then the big UK power conglomerate, if it succeeds in the takeover, can then say that it has actually invested billions in environmentally conscious power production, thus offsetting their large greenhouse gas belching plants they operate in Europe. It has nothing to do with magnanimously investing in green power for the benefit of the environment. It’s doing this to protect the shareholders returns from the huge impost of the new carbon taxes.

In the next article, I’m going to bite the bullet and venture into Solar Power, for so long the mantra of the green lobby, who perceive this as being the answer to all our trouble with respect to Electrical power.