Expensive oil and gas?

I like it! (For lots of reasons)

[Cynic mode]
Mind you, that's an awful lot of bottled heat to be letting out into the atmosphere (assuming 50% conversion to electricity). Might it contribute to global warming!?

The atmosphere weighs 5 x 10^18 kg, and the specific heat capacity of air is 1 kJ per kg per degree C.

If they are talking about producing 400 exojoules electricity so releasing also, say, 400 exojoules of waste heat as a byproduct per year (400 x 10^15 kJ) that would increase the atmosphere temperature by about 0.1oC per year. Not much, but ten years or 50 years of continual release adds up!

[/Cynic mode]

 

<div class='quotetop'>QUOTE(clett @ Aug 3 2006, 08:05 AM) [snapback]296891[/snapback]</div>

Does cynic mode include irony? :_> The additional heat won't build up endlessly because the atmosphere is not a perfect insulator; the heat will merely radiate away at a new slightly higher equilibrium temperature. Raising the Earth's temp by 0.1'C would be far better than the 2'C rise we face due to the release of greenhouse gasses such as carbon dioxide, which are a problem because they *do* make the atmosphere a better insulator.

 

Sounds like a closed system: steam out, steam and hot water back in. Heat escape would exist, but could me minimized. Any electro-geothermal experts out there?

 

<div class='quotetop'>QUOTE(etyler88 @ Aug 3 2006, 08:31 AM) [snapback]296878[/snapback]</div>

This is exactly what was said about atomic (fission) energy when we were kids. Some experts made claims that electricity would be so cheap that we wouldn't bother to meter it; just pay a monthly fee to be hooked up. That, of course, doesn't mean it won't happen with geothermal. I suspect the intrinsic need for energy and the cost of distribution will keep the costs near current levels, which is really pretty cheap when you consider what you are getting.

As for releasing additional heat into the environment, remember that geothermal heat is ultimately released into the environment, regardless of whether man helps or not. Drilling holes will increase the heat in a specific area, but not the overall amount of heat. To some extent it may speed the release of heat by breaching the insulation of the earth's crust, but I suspect the net effect is much better than having additional greenhouse gases.

This is exactly the sort of project we need to fund at the federal level. The chances of a big payoff are too great to ignore.

Tom

<div class='quotetop'>QUOTE(M. Oiseau @ Aug 3 2006, 11:33 AM) [snapback]296972[/snapback]</div>

To generate power, you must have a heat differential. In other words, to do work, you have to move heat from something hot to something cooler. In this case the cooler part is the surface of the earth, whether it is the air or water cooling. Some of the heat energy is converted into useful power, such as electricity, but the rest is dumped as low grade heat energy. Ideally you use this low grade heat for heating buildings or other useful processes, but it ultimately gets dumped into the air.

Tom

 

<div class='quotetop'>QUOTE(qbee42 @ Aug 3 2006, 11:00 AM) [snapback]296981[/snapback]</div>

Why is the heat dumped? If we're driving a turbine with superheated steam, the "exhaust" is low-temp steam and water which is pumped back into the deep well reservoir inlet.

 

<div class='quotetop'>QUOTE(M. Oiseau @ Aug 3 2006, 05:23 PM) [snapback]297327[/snapback]</div>

It's thermodynamic law - you must have a heat sink to get the work. A second 'cold' well could work, but is probably uneconomical. Been a while since thermo, but someone will correct me if I'm too far off. Basically, the turbine only spins because the hot steam is rejecting heat at the outlet, shrinking by cooling and condensation, and therefore creating a pressure differential. If it does not reject heat, there is no pressure differential created to spin the turbine. Where does the heat go? A cold well could work, but a nearby river or natural draft cooling tower to evap it to atomosphere is probably cheaper and more effective (ever wonder why all those nuke plants are next to a river or ocean? Cold is as important for power generation as hot). A standard car works on the same principle, with combustion creating a hot gas that happens to push a piston on its way to getting to a cooler area (out the tailpipe). Using cold local homes or a nearby industry that needs heat (mmmm, brewery) is better - at least you get a little more use of it!

 

Too bad space can't be used as a cold well. We could "vent" global warming to space while generating power. BLEH.

 

<div class='quotetop'>QUOTE(clett @ Aug 3 2006, 03:05 PM) [snapback]296891[/snapback]</div>

Where do you think the majority of the energy produced by a conventional power plant is going to?


<div class='quotetop'>QUOTE(M. Oiseau @ Aug 4 2006, 12:23 AM) [snapback]297327[/snapback]</div>

There are hard limits on what efficiency you can achieve given a certain temperature difference.
In a nutshell: heat is the lowest grade of energy. If you want to convert it into a higher grade of energy (such as electricity or motion) you need first of all a cold and hot reservoir, and you use the energy flow between both to drive a machine that produces other energy. You can do this only up to a certain efficiency. In other words, you have to give up some of the heat flow. The efficiency increases with the temperature difference between the cold and hot reservoir:

efficiency = 100% x (TH-TC) / TH

with TH= hot temperature, TC= cold temperature, and both should be in Kelvin. Do a search on "carnot cycle" if you want to learn more about it. Of course, you can still use the energy waiste to e.g. warm houses in the winter.

 

True, but it's the timescales that are different. The earth is cooling on its own, but if you start moving heat from the insulated core into the atmosphere, then you'll accelerate the process and heat the atmosphere. Of course, we're doing that anyway.

How many people think that global warming might be due to all the energy we're generating from fossil fuels ending up as heat in the atmosphere? It might be responsible for the accelerating rate of warming...

 

<div class='quotetop'>QUOTE(molgrips @ Aug 4 2006, 07:51 AM) [snapback]297590[/snapback]</div>

Few or none, I hope, because that isn't the cause. The amount of energy used by people (and thus released as heat) is still miniscule compared to the heating of the earth by the Sun and the flow of heat from inside the Earth. The problem is release of greenhouse gasses, which make the atmosphere a noticeably better insulator. Better insulation means that a given (unchanged) heat flow raises the temperature significantly.

 

<div class='quotetop'>QUOTE(jweale @ Aug 3 2006, 10:33 PM) [snapback]297482[/snapback]</div>

I haven't been clear enough. Look at a Rankine Cycle instead of Carnot because it's easier to conceptualize. Why can't the rejected heat (condenser) be directed back into the source well inlet (your "cold" well), thereby minimizing the rate of heat lost directly to the surface environment?

 

<div class='quotetop'>QUOTE(M. Oiseau @ Aug 4 2006, 10:18 AM) [snapback]297670[/snapback]</div>

How can the source well be both hot and cold simultaneously? The cold well would have to be a different well than the hot well (and a hole that soaks up heat is tough to find - heat has to go somewhere, and the only way out is up!).

Its an issue of driving heat flow. Heat is not a bucket of water, it requires a temperature differential to 'flow.' The rejected heat is at a lower temperature than the source well - it has to be or the turbine will not operate. You can not reject the outlet waste heat from the turbine back into the heat stream feeding the turbine - the waste heat will be either too cold or too low a pressure. The only way you could 'reject' it to the hotter source is by applying more pumping work than you earned from the cycle, kinda defeating the purpose.

The work is being done by heat moving from a high energy state (high temperature) to a low energy state (low temperature). Heat does not move and therefore does not do work if there is no energy state difference . And running a geothermal plant is not a batch process. Unlike oil, you can't empty the well out, then extract the energy, and then put the waste products back into the empty hole.

You're the first person I've ever heard say the Rankine Cycle is easier to conceptualize than the Carnot

 

<div class='quotetop'>QUOTE(vtie @ Aug 4 2006, 05:48 AM) [snapback]297563[/snapback]</div>

I'm going to pull out my atkinson cycle ICE and replace it with a new carnot cycle model. Then we'll see some real MPGs!

All of these posts have done such a good job explaining thermodynamics, I don't have anything else to explain.

Tom

 

<div class='quotetop'>QUOTE(jweale @ Aug 4 2006, 02:15 PM) [snapback]297816[/snapback]</div>

I concede. I'm wrong.

Because it was stated that the reservoir would be "very large" and "VERY deep," I was visualizing heat transfer down the hole and the inlet end being rather cooler than the exit end, each end being miles apart. I was hoping that someone who knows something about these deep injection reservoir systems could give us some details about how they might work.

<div class='quotetop'>QUOTE(qbee42 @ Aug 4 2006, 02:37 PM) [snapback]297836[/snapback]</div>

You could take a shot at explaining enthalpy in layman's terms. That would be fun. :huh:

 

<div class='quotetop'>QUOTE(etyler88 @ Aug 3 2006, 05:31 AM) [snapback]296878[/snapback]</div>

Well, I spent well over 30k on a vehicle without a hybrid drivetrain... that has NO internal combustion engine. How crazy am I? We really don't need to be burning gasoline in (most of) our cars at all. Hybrid is a cute little step, but we might as well get back to where we were ten years ago with EVs.

 

While we're on the subject of powerplant thermal efficiency and waste heat, check this out:

http://www.wowenergies.com/pages/1/index.htm

I think this is probably one of the BIGGEST ADVANCES in technologies for cutting CO2 emissions yet, but I can't understand why it's not being reported more widely? Double the electricity from the same amount of coal is surely a good thing. Wow have been touting their system for ages now too. Perhaps funding/money are the problem areas?

(BTW, my first post was a little tongue in cheek ).

 

With a nuclear power plant, the worst case scenario is a meltdown and release of radiation.

With a universal geothermal energy plant, a worst case scenario - alluded to in the article with, “. . . you need to think about are you disturbing the natural conditions in the earth that might cause bad things to happen†- could be the triggering of a massive earthquake, or volcano.

[your choice of what you believe would constitute a worst case of “bad things to happen.†]