Old quarry near runway now saves airport $430,000 a year

An abandoned rock quarry near a runway at Nashville International Airport was thought of as a liability, so risky that authorities considered filling it in a decade ago. Now, the water-filled pit is enabling the airport to save $430,000 a year.

By taking advantage of the quarry reservoir's year-round 50-degree temperature, the will be able to halve its cooling costs, said Christine Vitt, the airport authority's vice president of strategic planning and sustainability.

The geothermal system—the largest of its kind in North America—has been fine-tuned since it began operating in February, with results far beyond expectations, Vitt said at a dedication ceremony on Tuesday.

The system pumps hot from the terminal's cooling plant to stainless steel heat exchangers submerged about 50 feet under the reservoir's surface. The are about the size of an SUV and work similarly to a car radiator. Water enters at about 79 degrees, is cooled by the surrounding reservoir water, and returns to the plant at about 63 degrees.

It's a closed-loop system, so the water never leaves the pipes, and the components should last a century or more, said environmental consultant David Rehse of Energy Systems Group, who worked on the system. And unlike solar panels, which are a visible sign that a building uses renewable energy, this geothermal system operates continuously underground, rain or shine.

It's "the greatest project in Nashville you can't see," Rehse said.

The $10.4 million project is financed through grants and a loan that is being repaid with money that would otherwise have gone to cooling costs, as part of a sustainability plan created with help from the Federal Aviation Administration.

"Our operating budget doesn't increase," Vitt said in an interview. "What was maybe a liability has become a wonderful asset for us."


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May 18, 2016
So the money outweighed the risk?


If the quarry is abandoned and the city does not fill it in and some college kids have a party and one drowns, the city could arguably be held liable for negligence (although it should be the quarry's previous owner), even if the kids had to jump a fence.

However if it is an active facility that can't be filled in, then not filling it in is not negligence and the city becomes less liable. And since it is active, it becomes easier to justify a better fence or a security guard or other measures that reduce liability further as well as actually reducing the risk.

So the net result is lower cost (assuming that the saving really do pay for the costs) AND lower risk (both actual and liability), plus good publicity for saving energy.

May 18, 2016
Risk of what ?? This doesn't involve hot-rocks, fracking or what-have-you. It is a neat variation on the 'lawn-buried' heat-pump coil systems that have been around for several decades.

May 18, 2016
Risk of what ?? This doesn't involve hot-rocks, fracking or what-have-you. It is a neat variation on the 'lawn-buried' heat-pump coil systems that have been around for several decades.


Mainly liability:
Kids swim in or jump into abandoned quarries, and sometimes a kid drowns and the parents sue, and sometime that city (or other quarry custodian) is found negligent (unguarded attractive nuisance) and gets hit for millions.

(As teenagers we used to jump from the rocks into an old abandoned copper-mine pit that had filled with water, for example, and the town periodically sent the police up to try to stop it.)

The risk / liability is reduced once the pit it in use for something again.

May 19, 2016
How long until cities decide that geothermal energy should be available to homeowners like other utilities?

I want a set of pipes to my place for heating in the winter and cooling in the summer. The city could bury the pipes 6 ft down and run them like water pipes. Each person can pump their own from the loop and return it to the return loop.

We deliver Water, Gas, electricity and telecom, why not geothermal?

May 19, 2016
jag, we already do it, and have for decades, as Nik said. It is done by the individual homeowners.

May 19, 2016
How long until cities decide that geothermal energy should be available to homeowners like other utilities?

I want a set of pipes to my place for heating in the winter and cooling in the summer. The city could bury the pipes 6 ft down and run them like water pipes. Each person can pump their own from the loop and return it to the return loop.

We deliver Water, Gas, electricity and telecom, why not geothermal?


@Lord_jag: You can have it today if you move to Iceland! Geothermal heat is used to generate electricity, and the left-over warm water is piped to Reykjavik and around to buildings.

Combined-heat-and-power is also used in quite a few European cities ('waste' heat from power plant cooling water is piped to customers around a city). It isn't geothermal, but since the heat was going to be wasted it is still a good step.

May 19, 2016
...why not geothermal?
@Lord_jag
as noted by RS above you can move to Iceland... or there are US areas too, if you care to go to the west, like Klamath Falls, Oregon, Alaska, Wyoming, Cali and some other places (some listed here: https://en.wikipe...d_States )

i am sure you can also consider investing in companies like this: http://www.usgeot...dex.aspx

check this out too
http://geo-energy...inal.pdf

May 19, 2016
A great thing about Iceland is that the capital, which has ~2/3 of the whole country's population, is close enough to one of the main geothermal stations that they pump enough hot water over to heat much of the whole city.

Plus people kept sneaking into the low-temperature 'waste' water lagoons from the electricity production, and when fences didn't keep people out the power company got smart and opened it up as a spa and made a huge profit (it is now considered one of the world's top spas).

May 19, 2016
Isn't Eikka going to tell us it really will not work, like the swimming pool heat sink?

May 21, 2016
We deliver Water, Gas, electricity and telecom, why not geothermal?


Because it doesn't need to be delivered. You drill a hole onto your property and draw it out from there.

Isn't Eikka going to tell us it really will not work, like the swimming pool heat sink?


You were not talking about using swimming pools as heat sinks.

You said that you had proposed the use of swimming pools as seasonal thermal storage when you were working with HVAC systems - your proposition involved pumping heat into swimming pools and then drawing the heat out in the winter by reversing the air conditioner. I pointed out that the heat escapes the swimming pool in a matter of days because the pool is not well insulated and there is significant evaporation, and a pool is too close to the ground surface for a geothermal system anyhow - it follows the ambient temperature.

A large body of water, such as a quarry lake, will have significant thermal inertia and will work.

May 21, 2016
I just reported what had already been done, Eikka. You can find ways they could not do it all you want.

And perhaps you would fire up the pool heater?

May 21, 2016
I just reported what had already been done, Eikka. You can find ways they could not do it all you want.


No you didn't. You were tooting your own horn about how smart you were for suggesting the thermal storage scheme all the way back when and calling other people stupid because they didn't buy into the idea then or now. The whole debate wasn't about using pools as heat sinks, but as thermal storage.

Don't try to retcon yourself - everyone can google your old comments.

And perhaps you would fire up the pool heater?


And what would be the point of heating your pool in the winter so you could then draw heat from it through the HVAC? Instead of just... you know, heating the house directly?

May 21, 2016
Let me quote you directly, gkam

While at PG&E, I tried to get homeowners and those putting in pools to consider using them as heat sinks. In the Summer, the heat from the house gets dumped into it to heat the pool and cool the house, and in the Winter it is covered and that heat is pumped back into the house.

That was in the late '80's, and we had little compatible equipment, and even less compatible consciousness.

http://phys.org/n...html#jCp

May 21, 2016
Quote away. That does not refute my statement that I got it from an actual installation.

May 22, 2016
Quote away. That does not refute my statement that I got it from an actual installation.


A statement like that doesn't need to be refuted because you haven't given any evidence for it. You simply changed your statement and blamed others for not proving your assertions for you:

It is an old concept, and the pool idea was not mine, but one already used and perfected. You should have looked closer.


That's just backpedaling because you got caught up with a lie again.

Where has anyone ever used a small private swimming pool for seasonal heat storage?

Nobody with a clear conscience would try to sell people a thing like what you proposed, because it simply does not work and even some cursory engineering calculations woud show that it doesn't. You're plain and simply making it up.

May 22, 2016
For example:

http://wcec.ucdav...ment.pdf

Figure 10. Page 8

The rate of energy loss from the example pool being heated by an AC system in the study is on the order of 250 kWh a day as judged from the figure from the slope of the energy accumulation curve. There's just no net accumulation of energy that you could retrieve later on, and this is why nobody with any sense in them would try to use a swimming pool for thermal storage.

So if you claim that such systems exist, please do tell us where so we can tell the owners they can sue the company that sold it to them.

May 22, 2016
"That's just backpedaling because you got caught up with a lie again. "
-------------------------------

STOP IT!

The kids you play with may be liars but I am not. If you cannot debate an issue without resorting to name-calling and silly assertions, you have lost the debate!

And you have lost the debate.


May 22, 2016
Eikka, the use of pools and ground temp for cooling and heating has been known for centuries, below a certain depth in the ground (6-10 ft) it maintains an even temperature year round of around 50 to 55 degrees F. This has been used for root cellars in summer, and the below ground temp of 50 is MUCH warmer than the above ground freezing in winter which is why a lot of the plains folks dug their houses at least partway in to that same ground.

Modern heat pumps work on the same principle for cooling and heating houses today. The use of pools for thermal storage has been around for a long time, especially when folks realized that the pools they heated during summer did not freeze like other natural ponds did due to the heat that seeped into the tile, concrete and soil around said pool and thus kept it warmer over the Winter.

Folks have built houses with walls made of water containers to keep cool during the day and warmer at night. Do some STUDY Eikka, leave the ego at home.

May 22, 2016
@SteelWolf - Please read Eikka's first post in this thread.

Eikka was clear that he was not arguing using a swimming pool as a heat sink, but with using a household swimming pool as SEASONAL heat storage.

I must have missed the earlier conversations that Eikka was referring to - normally bringing up the past to attack a current commenter in a thread is poor form, but in this case gkam invited Eikka's comment (see gkam's comment before Eikka's).

May 22, 2016
As I did point out in my post that there is a lot of heat lost to the soil surrounding the pool, as the contact loss is much greater (by an order of a couple magnitude) by conduction and is actually thus stored in the ground around the pool, it is going to stay warmer throughout the year and, yes, to a degree may be used as a heat sink on a seasonal level, in fact, people setting up the central air heating systems that use differences in air and ground temp actually delight to have a heated pool to be able to tap that heat as a source. It is something they look for and is why those heaters are generally located near a pool if there is one. People who live in their books and on the computer screens in closed rooms all day do not always understand the significance and amount of science even the basic lay person deals with on a daily, hands on basis.

Economical; unlikely, but Possible; unequivocally Yes, doable because the ground itself is the heatsink, not the water.

May 22, 2016
Personal reactions to my posts are one reason for the confusion. Some here are intent on challenging everything I post, and look for excuses to poke holes in them.

The use of the swimming pool is not only good, but in use today. Fiddle with your numbers all you want, the thermal storage available in that pool is very large, and can be used in the winter, even if not hot. Ground-coupled heap pumps use base temperatures in the 50sF.

If you want to do it, you can get the specially-made heat exchangers here:

http://www.hotspo...hangers/

May 22, 2016
People who live in their books and on the computer screens in closed rooms all day do not always understand the significance and amount of science even the basic lay person deals with on a daily, hands on basis.


I agree with you on that! (I've learned more about practical engineering from being a do-it-yourselfer than I ever did in university (although I find that the two types of knowledge are complimentary).

For example, putting a 'proper' engineering analysis together for how much heat is in the ground versus the pool water would be a long process, but and a quick non-engineering estimate is fairly simple and almost as accurate.

- continued -

The ground around a backyard pool holds roughly as much heat as the pool itself - the the heat gets conducted very roughly this can be seen by you comment on the l.pool holdI am curious as to why you think that the ground around a pool a pool would


May 22, 2016
- continued -
Below about 2 meters the ground is fairly constant in temperature, so heat from the pool will be conducted very roughly 'up to 2 meters' into the ground around the pool.
If the pool is about 2 meters deep then the volume of ground heated below the pool is the same as the volume of the pool, and if the pool is about 5 meters by 10 meters then the wall area is just a bit bigger than the floor area, to the volume of ground heated iis twice the volume of the pool.

The heat drops off rapidly, starting at the temperature of the pool and dropping to the ground temperature, so the average ground temperature is raised a bit less than half the pool temperature, so the 'half' and the 'twice' cancel. Wet dirt is roughly 2.5 times as dense as water and has roughly 40% of the specific heat, and these again cancel.

So to a first approximation, the extra heat in the ground is about the same as the extra heat in the water (for a 5m x 10 m x 2 m pool).

-continued-

May 22, 2016
A 5 x 10 x 2 pool is 100 m3 or 100,000 kg of water so that's ~420 MJ per degree C, or ~120 kWh per degree, doubling that for the ground is 240 kWh/C so if the pool is 10C warmer, then that's 2400 kWh of heat. For a reasonable coefficient of performance of 3 for a heat pump, that saves ~~ 800 kWh of electricity through better heat pump performance. Since heat is needed at night, that's probably ~~$100 of electricity.

But could the pool be kept ~10 degrees warmer than normal?
Looking at the paper Eikka linked to, figure 9 says that the heat loss from radiation and evaporation were together almost 50 times greater than the heat lost through conduction into the ground!

So yes, if you have a respectable sized pool and you keep an insulated cover over it, you can store somewhere around $100 of heat if you are willing to keep a cover on the pool.
Probably not worth the cost of setting up the plumbing, unless you LIKE tinkering.

May 23, 2016
People who live in their books and on the computer screens in closed rooms all day do not always understand the significance and amount of science even the basic lay person deals with on a daily, hands on basis.
I agree with you on that!
@RScience
i've learned from "laymen" as well
but!!!
... that doesn't mean that making a claim and then arguing that it must be correct because personal anecdote means it must be true (this is argument from authority - not evidence)

when the argument falls back on "because i have a degree" rather than "here is the evidence" (or here are links/references) then it is a bad argument *and* wrong, especially when it is proven to be such by evidence, links and references

argument from authority isn't valid unless there is evidence with it - period

May 23, 2016
It does not mean what you look up is what you understand.

And when evidence is provided for personal achievement in the areas and with the issues discussed, what do you do? Personal attacks. Do not try to gussy it up with excuses, you are just an attacker like otto, with hurt feelings and a need to get even.

May 23, 2016
when the argument falls back on "because i have a degree" rather than "here is the evidence" (or here are links/references)

Which is why I avoid mentioning my background or personal achievements except in a direct response to a question or a challenge ... it simply shouldn't matter, because each of my comments should stand or fall on its own merits.

Because I think that each comment should be rated on its own merits, I also never down-rate a post simply because of who posted it. I might skip over posts from a habitual abuser, but if I'm going to rate a post I read it carefully (and I only give it a 1 if it is really bad, while if someone who often makes pointless posts makes a surprise good post, I give them a 5* to try to encourage them).

I also avoid personal attacks, except in the case of a bully who tries to use personal attacks on others (I did enjoy showing that JVK's bullying insults that actually applied to himself).

May 24, 2016
it simply shouldn't matter, because each of my comments should stand or fall on its own merits
@Real
yep... I was not referring to you at all, BTW - just for the record

there are some who truly believe that because they paid for a degree it means they're the expert with experience in everything, despite their fallacious claims, comments or statements (not going to name names)
... the case of a bully ...
but what about the idiot bully who can't substantiate a claim but continually falls back on "but i have a degree"?
... worse still, they use said argument when they've been proven false with actual evidence, links, etc?

argument from authority is a personal attack, especially when proven wrong with facts

if you have youth or inexperienced reading, will they take the time to check facts before making a decision about the content?

or will they ASSume the degree holder is more important than the content?

they should be challenged when wrong (like jvk)

May 24, 2016
Many folk do not have sufficient experience to speak from it, so they get their "information" from the writings of others, who also may not have said experience. But it makes them feel "smart".

http://www.thegua...n-google

May 24, 2016
Many folk do not have sufficient experience to speak from it, so they get their "information" from the writings of others, who also may not have said experience. But it makes them feel "smart".


So true, but they are no worse than folk who overvalue their experience and spam a comment board. You have some good comments, but you comment so often with such repetitive comments that I find myself starting to skip over yet-another-gkam-comment (along with the yet-another-attack-on-gkam comments that typically follow).

I offered you friendly advice before - and I will offer it again: you will have much more positive impact if you post 1/10 as often (as long as you make the best 10% of your posts).

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