Get It Where You Can
Geothermal power in Alaska, hmmm. Seems counter-intuituive to me. Turns out there are hot springs in Alaska - they’re just not very hot (comparatively). Traditional geothermal generators require steam. That means the water has to be hot (not just the 212 F temperature you are thinking)! From Wikipedia
The most common process is the steam flash process, which incorporates steam separators to take the steam from a flashing geothermal well and passes the steam through a turbine that drives an electric generator.
Commercial exploration and development of geothermal energy to date have focused on natural geothermal reservoirs—volumes of rock at high temperatures (up to 662°F or 350°C)
This process requires sources of heat close to the surface.
Although geothermal energy is present everywhere beneath the Earth’s surface, its use is possible only when certain conditions are met: (1) The energy must be accessible to drilling, usually at depths of less than 2 mi (3 km) but possibly at depths of 4mi (6–7km) in particularly favorable environments…
Do I have to have steam? Not necessarily.
A more efficient utilization of the resource can be obtained by using the binary process on resources with a temperature less than 360°F (180°C).
So what is this “binary process”? The Wiki gets a bit too technical so I’ll take over.
Simply put, utilizing heat without using steam is like a heat pump for your house. You take a second system (hence, binary) to utilize the temperature differential - you are moving heat. When substances heat they want to expand. When gasses heat they REALLY want to expand. You keep them under pressure until you are ready to use this energy. In the case of the home heat pump you typically let the gas expand in some coils, that makes the coils cold, then you blow air across the coils to cool your home. With power generation it’s a bit more intense. You let this hot gas out of a nozzle and spin a turbine to produce electricity.
Converting your home heat pump to an electrical generator is not a job for a home hobbyist. Enter the Chena Geothermal Power Plant
The Chena geothermal power plant came online in late July 2006, putting Alaska squarely on the map for new geothermal technologies.
The cost of power production, even in semi-remote locations such as Chena, will be reduced from 30¢ to less than 7¢ per kWh once the UTC plant is installed and operational.
The site has excellent explanations and references so I won’t go into great detail here. United Technologies Corporation (UTC) is the engineering firm involved with the project..
The challenge for moderate temperature small scale geothermal development has been to bring the cost down to a level where it is economical to develop small geothermal fields.
So far this hasn’t been bad - new technology, nice success story. This is where it gets good.
The technology developed by UTC can operate off any heat source, with a minimum of 100°F temperature differential between the heat source and sink.
Ok, I’m thinking waste heat from ALL KINDS of applications. I’m especially thinking about fuel cells that run hot as the dickens. One definition of efficiency is how may times you can use the fuel (it’s really more simple than that, energy out divided by energy times 100 (to get percent) in but an equation seems to throw some people). Oil wells sound like a perfectly reasonable choice as well.
The oil and gas also provides another possible application for UTC’s power plant. Because most oil and gas wells are quite deep, they are warmed by the natural thermal gradient of the earth.
Some estimates suggest up to 5000MW of additional power could be generated in Texas alone…
I’m certain there are a few other states that have oil wells - Oklahoma comes to mind. There is effort under way to explore the available geothermal resources but new geothermal requires digging, drilling, and (usually) transmission lines. Where can we get the heat above ground where there are already people? There have to be lots of examples.
- Posted in : Environment, In the News, Pictures, Positive Change, Renewable Energy
- Author :Rt
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[...] I heard about geothermal in Alaska I learned a lot. I even made an attempt to explain the binary heat capture process (this graphic [...]