Using an Abundance of Wasted Energy

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Using an Abundance of Wasted Energy

Postby AUGUGA » Wed Jan 05, 2011 6:13 pm UTC

So a few weeks ago, I was taking my winter break vacation, and my family and I had booked a hotel room for the night. While taking a shower and watching the water go down the drain, I came to the realization that, being on the third or fourth floor, the water had lots of potential energy that was being wasted as it simply flowed to the bottom of the hotel and into the sewer system where it would flow slowly to a water treatment plant to be treated or whatever it is they do at water treatment plants. What a waste of perfectly good energy! We could use it to power turbines, or something, right? I'm not an engineer, and I don't plan on becoming one, so maybe somebody else can use this idea to do good work.

Is there a way to cost efficiently tap that energy formed by the downhill flow of our excrement? Is it already being done? If there is, and it isn't, we should do that. 8)
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Re: Using an Abundance of Wasted Energy

Postby Aelfyre » Wed Jan 05, 2011 7:06 pm UTC

It's not a bad idea in circumstance such as that when you are high up and the fluid has to be channeled down to the recovery system.. I mean techincally all you are doing is recovering some of the energy it took to pump it up to that height in the first place. Not sure what kind of net yield you could expect but I imagine it would be most cost effective in large multi-story buildings like condos and hotels and what have you..

that being said I guess concievably you could put systems such as this in storm water runoff drains in areas that are quite hilly and recover a decent amount of energy from rain water.
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Re: Using an Abundance of Wasted Energy

Postby jmorgan3 » Wed Jan 05, 2011 7:44 pm UTC

A turbine would slow down the water as it goes down the drain. This would cause a vastly increased chance of clogs and of water backing up into your tub. That's not worth the headache. The storm water turbine might work until a tree tries to go through it.
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Re: Using an Abundance of Wasted Energy

Postby firechicago » Wed Jan 05, 2011 8:04 pm UTC

A back of the envelope calculation suggests that the amounts of energy available are just too small to matter.

Assuming you use 100L of water in your shower, and the water drops 30m from your fourth floor room to ground level, you've got about 30,000J of kinetic energy available there (KE=PE=mhg, 100L = 100kg, 100kg*30m*10m/s2=30,000J).

That sounds like a lot until you realize that electrical energy for general use is measured in kilowatt-hours, with 1kwh = 3,600,000J. A quick google suggests that electric power in the U.S. costs about 10-20 cents per kwh. So in a best case scenario (capturing all of that energy with a magically efficient generator) you've saved yourself a sixth of a cent per shower. Assuming you use 2 showers worth of water per day, the entire system (with installation, and assuming no maintenance costs) would have to cost less than $1,400 per unit to pay you back at even a 5% rate of return.

And remember, that's with a whole bunch of ludicrously favorable assumptions built it. It might work in some very tall buildings (over 100m) but it just doesn't make any sense for buildings that aren't skyscrapers.

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Re: Using an Abundance of Wasted Energy

Postby gmalivuk » Wed Jan 05, 2011 8:55 pm UTC

From an environmental standpoint, a much better thing to do with your shower water is greywater recycling. In other words, flush your toilet with old shower water, instead of peeing into a bowl of stuff that's cleaner than what several billion people have access to for drinking. (Granted, even after the shower *and* the pee, it's still cleaner than what a whole lot of folks have to contend with.)

Furthermore, if you can efficiently channel water from the shower drain to the toilet tank, you'll still save most of the energy that would otherwise have been used to pump water up into said toilet tank, without all the complications of trying to maintain a turbine being run on raw sewage.
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Re: Using an Abundance of Wasted Energy

Postby AUGUGA » Wed Jan 05, 2011 11:10 pm UTC

I'm not talking about putting turbines in the shower drain, I'm talking about putting turbines in the giant sewer pipes in the ground. The shower in the hotel was just what sparked the thought.
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Re: Using an Abundance of Wasted Energy

Postby Technical Ben » Wed Jan 05, 2011 11:46 pm UTC

Which is hydro electric power. Do you want to see the lake made by all your waste water?
I would guess you could do a water wheel. But that would take a lot of water, flowing quickly As it's from drains and not a river, I don't think it flows too well. Unless your town/city is high in the mountains.
You also have to clean your generator a lot if it's dirty water.
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Re: Using an Abundance of Wasted Energy

Postby gmalivuk » Thu Jan 06, 2011 12:26 am UTC

AUGUGA wrote:I'm not talking about putting turbines in the shower drain, I'm talking about putting turbines in the giant sewer pipes in the ground. The shower in the hotel was just what sparked the thought.
What difference does that make? It's still "a turbine being run on raw sewage", so it still has all the same problems.

Also, various sites I've looked at say 250L/day of total indoor water use is the American per-capita average. Suppose a 4-person apartment to get 1000kg/day of water, and a magical 100% efficient turbine 30m below the apartment, and you'll be able to generate an average of 3.4 Watts per household! Which doesn't really seem worth it, being as it's only 0.053% of the average total power used by those same 4 people.
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Re: Using an Abundance of Wasted Energy

Postby Zamfir » Thu Jan 06, 2011 8:38 am UTC

Potential energy isn't worth the effort, but heat is another story. A shower consumes a few MJ to heat (say 1 kWh on average, not necessarily electric of course), and there are some potential ways to recoup part of that.

The most direct is a heat exchanger between the water going in and out of your shower, but heat exchangers aren't free and do have clogging risks. There's also the complication that the heat exchanger has to be placed before the incoming water gets heated. This requires lots of plumbing unless it is taken into account in the first design of the building, it's not something you can just add to an existing shower.

Another option, useful in winter, is to redirect the water from the shower to a floor heating system for example.

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Re: Using an Abundance of Wasted Energy

Postby Magnanimous » Thu Jan 06, 2011 8:47 am UTC

From what I've read, setting up new sources of energy is a much better idea than trying to recycle what you already have. Lifehacker had a page about building solar heaters a few months ago, for instance.

Somewhat related: I've always wondered how hot street lights get. If the bulbs aren't very efficient, it could be worth it in the right circumstances to harness that heat... (This is all void with LED bulbs, though, so eh.)

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Re: Using an Abundance of Wasted Energy

Postby Thesh » Thu Jan 06, 2011 9:00 am UTC

Magnanimous wrote:Somewhat related: I've always wondered how hot street lights get. If the bulbs aren't very efficient, it could be worth it in the right circumstances to harness that heat... (This is all void with LED bulbs, though, so eh.)


You would be better off with LEDs. The problem is that the smaller the power source, the less efficient it is.

As for sewage and storm drains, they would easily clog up unless you could efficiently separate solid and liquid matter. For the future, I believe we are best building whatever solar and geothermal plants we can, while using nuclear power to fill the gaps (we should actually have enough nuclear power to run everything in the world, as we can control that better than we can control the weather).
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Re: Using an Abundance of Wasted Energy

Postby Zamfir » Thu Jan 06, 2011 9:01 am UTC

Magnanimous wrote:From what I've read, setting up new sources of energy is a much better idea than trying to recycle what you already have. Lifehacker had a page about building solar heaters a few months ago, for instance.

Nah, industrial plants are cramped with systems to recoup energy and heat, even with additional systems to recoup the losses from those systems. The problem is that such systems cost money and maintenance, with high efficiencies of scale. So single households tend to have a lot less of such systems, because the energy waste flows are smaller and the scale effects don't make it worthwhile.

But household boilers for example are nowadays a lot more advanced than a few decades ago, and other systems are getting cheaper and more robust too, making it more likely that they can be used in houses. I wouldn't be surprised if small cogeneration units start to enter households in the coming decades
Somewhat related: I've always wondered how hot street lights get. If the bulbs aren't very efficient, it could be worth it in the right circumstances to harness that heat...

That's basically the household scale problem squared: you could theoretically collect the heat in every light. But you need a larger scale to make it pay.

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Re: Using an Abundance of Wasted Energy

Postby Tass » Thu Jan 06, 2011 11:34 am UTC

Magnanimous wrote:Somewhat related: I've always wondered how hot street lights get. If the bulbs aren't very efficient, it could be worth it in the right circumstances to harness that heat... (This is all void with LED bulbs, though, so eh.)


Street lightning often uses sodium vapour lamps which are even more efficient than fluorescent and most LEDs (although with terrible colour reproduction)

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Re: Using an Abundance of Wasted Energy

Postby idobox » Fri Jan 07, 2011 2:24 pm UTC

There is another problem with the turbine idea. The turbine will slow down the water, and will generate pressure. If you don't take care of that with one-way valves and such, flushing your toilet on the 4th floor would create geysers in lower grounds.
And even if you can avoid the sewer geysers, the first floor toilet might take ages to flush, because the pressure blocks the one-way valve.
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Re: Using an Abundance of Wasted Energy

Postby nitePhyyre » Mon Jan 10, 2011 6:05 pm UTC

I've always wondered this with revolving doors. They are human powered turbines that are never hooked up to a generator. In big malls, some of these never stop spinning.
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Re: Using an Abundance of Wasted Energy

Postby letterX » Mon Jan 10, 2011 7:01 pm UTC

nitePhyyre wrote:I've always wondered this with revolving doors. They are human powered turbines that are never hooked up to a generator. In big malls, some of these never stop spinning.

Because we want to encourage use of the revolving doors instead of the handicap-accessible regular door that is always right next to them. Using only revolving doors in a building can significantly cut heating/cooling expenditures, depending on use-patterns (and myriad other factors about the building), but the point is, you're more likely to save a lot more energy by getting people to not use the regular doors than you will generate by turning people into microgenerators.

And when people start asking why the door is unusually difficult to push, and you tell them it's because they're being used to generate power, they will probably use the regular door instead.

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Re: Using an Abundance of Wasted Energy

Postby Technical Ben » Mon Jan 10, 2011 7:47 pm UTC

nitePhyyre wrote:I've always wondered this with revolving doors. They are human powered turbines that are never hooked up to a generator. In big malls, some of these never stop spinning.

Perhaps because they are motorised. :lol:
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Re: Using an Abundance of Wasted Energy

Postby Izawwlgood » Mon Jan 10, 2011 8:00 pm UTC

I too think about this a lot; I was appalled to discover that most car breaks don't include a generator to recover lost energy, for example. Or didn't until recently.

I don't know a lot about the technology, but don't piezoelectrics convert electricity to movement (in the material) and vice versa? Can't they be used to generate current? Why not just install strips on doors and the like, and in peoples shoes, sleeves, pants, etc?

Name of the game isn't to extract ALL the energy spent, just a steady trickle. With better energy storage devices, I can see this being a pretty cool thing.
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Re: Using an Abundance of Wasted Energy

Postby Antimony-120 » Mon Jan 10, 2011 9:40 pm UTC

Because it's really expensive to do that, and it doesn't make much energy.

The issue is that we use a lot of power, and the standard ways of producing power are REALLY REALLY good at what they do. Think about this, imagine a bucket chain. Now lets make it, say a kilometer long. At 2 people per m the bucket chain has ~2000 people in it. Now this bucket chain is capable of delivering roughly a 1 gallon bucket every second of every minute of the day (so far I've been very generous). So, how many people does it take to create the hoover dam? (at over 100m height difference, this is a 1/10 slope)

Well, flow is roughly 650m^3/s, or 650 000L/s, or approximatly 150 000gal./s (for a 4L gallon). So we need 150 000 bucket chains, of 2000 people each. The Hoover damn creates a muscle power equal to roughly 300 000 000 people. In short, if you got every single man, woman and child in the U.S. working day and night working on a bucket chain, you would have 1 Hoover dam.

Of course that's not necessarily the most efficient way to create power from muscle, but it exists merely to give a concept of scale. Electricity generation is non-trivial, and muscle power is not sufficient to match even a small percentage of out energy needs.

...

Luckily, I'm from Canada, where Hydro and nuclear power abound, so I'm not exceptionally worried about my electrical generation (at least, not unless I'm in Alberta, which is all coal).
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Re: Using an Abundance of Wasted Energy

Postby Technical Ben » Mon Jan 10, 2011 11:14 pm UTC

Izawwlgood wrote:I too think about this a lot; I was appalled to discover that most car breaks don't include a generator to recover lost energy, for example. Or didn't until recently.

I don't know a lot about the technology, but don't piezoelectrics convert electricity to movement (in the material) and vice versa? Can't they be used to generate current? Why not just install strips on doors and the like, and in peoples shoes, sleeves, pants, etc?

Name of the game isn't to extract ALL the energy spent, just a steady trickle. With better energy storage devices, I can see this being a pretty cool thing.


But isn't burning the corn in a furnace more power efficient?*
Your making all those things harder for those people. We need to find wasted energy first. Not steal it off the masses while they are not looking. ;)

*Than eating it, then pushing the door open, to get electricity out of it.
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Re: Using an Abundance of Wasted Energy

Postby Izawwlgood » Tue Jan 11, 2011 1:22 am UTC

You don't think accelerating an automobile, and then converting that momentum into heat friction is a waste?
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Re: Using an Abundance of Wasted Energy

Postby letterX » Tue Jan 11, 2011 1:32 am UTC

It is, but until you started having (partially) electrically powered cars, there wasn't a good mechanism for storing the reclaimed energy. Also, you need regenerative brakes to be both reasonably efficient, and still good at actually stopping the car.

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Re: Using an Abundance of Wasted Energy

Postby Technical Ben » Tue Jan 11, 2011 8:36 am UTC

Izawwlgood wrote:You don't think accelerating an automobile, and then converting that momentum into heat friction is a waste?

Yep. But was talking about doors and manually moved objects. Counter productive to put too many electrical generators being powered by your body. You are exerting more energy to do the extra work, not create it from "spare" or "free" or "wasted" energy.

Cars though, can benefit from all of these kind of devices. We do hit a problem with weight though. So we need to find lightweight solutions. That is usually why you do not find a sterling heat engine on your bonnet.
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Re: Using an Abundance of Wasted Energy

Postby Izawwlgood » Tue Jan 11, 2011 12:43 pm UTC

Technical Ben wrote:That is usually why you do not find a sterling heat engine on your bonnet.

Well there's your first problem.

The suggestion wasn't to make doors out of these materials, but to allow doors to generate a small amount of current. The point again with revolving doors, in say, train stations, is that if you have thousands of people walking through them daily, you don't need to recapture ALL the energy, or even most of it, just some.
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Re: Using an Abundance of Wasted Energy

Postby HungryHobo » Tue Jan 11, 2011 3:30 pm UTC

Izawwlgood wrote:The suggestion wasn't to make doors out of these materials, but to allow doors to generate a small amount of current. The point again with revolving doors, in say, train stations, is that if you have thousands of people walking through them daily, you don't need to recapture ALL the energy, or even most of it, just some.


I once heard that people just throw their toenail clippings away.
If we employed teams of people to collect the toenail clippings from every house in the country then brought all those clippings to a central location and burned them to power a generator sure we wouldn't make much power and we wouldn't capture ALL the energy or even most of it, just some. but <tripe>every little helps</tripe>

your problem is that you're ignoring the stunning cost of such ideas.
And "cost" isn't some abstract thing invented by some greedy buisnessman.
It's a real expression of the resources, energy and work it would take.

It's entirely possible that the energy it would take to stick generators to every revolving door and piece of clothing would be more than you would ever recover through such a system and as such would make the problem worse.

it's the same way of thinking that drives people to do crazy things like sticking tiny little inefficient, expensive ,status symbol solar panels on their roofs in canada instead of investing in nuclear or a nice big serious solar installation in the middle of a desert on the equator.
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Re: Using an Abundance of Wasted Energy

Postby gmalivuk » Tue Jan 11, 2011 4:01 pm UTC

"Every little bit helps" is a perfectly fine sentiment, as long as you're talking about net benefit and keeping in mind the associated costs.
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Re: Using an Abundance of Wasted Energy

Postby Technical Ben » Tue Jan 11, 2011 4:05 pm UTC

Izawwlgood wrote:
Technical Ben wrote:That is usually why you do not find a sterling heat engine on your bonnet.

Well there's your first problem.

The suggestion wasn't to make doors out of these materials, but to allow doors to generate a small amount of current. The point again with revolving doors, in say, train stations, is that if you have thousands of people walking through them daily, you don't need to recapture ALL the energy, or even most of it, just some.


I did not say to make the door out of the materials. I was commenting on adding a generator of any type to the door. This will add to the energy needed to push it open. This will add to the calories needed to feed your population (train commuters or hotel users). This will add to the food you need to grow. So unless it is only used on the airport foreign arrivals terminal, it is costing you more than it needs to in generating power.
So to avoid all the unnecessary, and wasteful, steps in between we can just burn food. Or, to be more precise use bio-fuel in power generation. Which is being done already.

Now for devices that do not have access to mains power, these little power generators are great. Such as a kinetic powered watch or phone. I'd love a bluetooth keyboard powered by button presses. Or a mouse by acceleration. But not a house light powered by the light switch (it would need to be larger than the house!).

[edit] Oh, and what is wrong with me pointing out a sterling heat engine is too heavy to be used to recapture wasted heat energy on a car? This is a fundamental thing you need to consider when ever looking at generating energy. What is the cost in energy to run it and what is the profit in energy made. That is even before we talk about manufacturing costs.
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Re: Using an Abundance of Wasted Energy

Postby gmalivuk » Tue Jan 11, 2011 4:09 pm UTC

Technical Ben wrote:This will add to the food you need to grow.
This is only true if your country has a food shortage (or is just on the edge of that). In a country where most of the population eats too much already, giving folks a bit of extra exercise when they go through doors is probably a good thing.
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Re: Using an Abundance of Wasted Energy

Postby Technical Ben » Tue Jan 11, 2011 4:15 pm UTC

gmalivuk, I agree with you there. But that is not the question, or discussion being made. As would it not be better to just get everyone to go to the gym, and use dynamo connected gym equipment?
Or as said, just burn the food. Now you have no excess and no one eats too much. You loose a lot less due to waste (as far as I can tell, less steps = less waste). We already see waste material being put into power generation.

How about a TV remote wired up to the grid? If it works in giving, or receiving electricity it will lower the number of couch potatoes. :)

[edit] The entire comment could be rephrased "energy requirement is increased" by adding a generator. We are talking about reclaiming energy, not how much, or little, is produced in the first place. I was trying to point out, that you do not reclaim any energy, but increase the amount needed in the first place. A bit like putting an alternator on your electric motor to reclaim some of the energy...
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Re: Using an Abundance of Wasted Energy

Postby HungryHobo » Tue Jan 11, 2011 4:22 pm UTC

gmalivuk wrote:"Every little bit helps" is a perfectly fine sentiment, as long as you're talking about net benefit and keeping in mind the associated costs.


If everyone does a little... very little gets done unless you're talking about everyone doing a little to the benefit of a few.
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It's a fine sentiment when you include all costs but people tend to exclude lots of costs and make silly assumptions like assuming that the time and effort people have to put into doing XYZ has zero value.

See also changing the scales like : "every everyone in the world [insert something that sounds small but in aggregate takes a vast amount of human time an effort ] then you'd save enough energy to [ insert something which sounds BIG but in real terms is an almost infinitesimal gain]"

If everyone in the world [put a generator in their drain/spent an hour on an exercise bike generating power] then we'd have enough energy to [run all the street lights in some town for a month or anything else which sounds big but in real terms means something like 0.00001% of the energy the world uses]
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Re: Using an Abundance of Wasted Energy

Postby gmalivuk » Tue Jan 11, 2011 5:25 pm UTC

Technical Ben wrote:As would it not be better to just get everyone to go to the gym, and use dynamo connected gym equipment?
You could *also* put generators on gym equipment, sure. But it's not very likely you'll be able to get lots of additional people to go to the gym regularly, whereas it's pretty certain people will continue to go through doors.
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Re: Using an Abundance of Wasted Energy

Postby jmorgan3 » Tue Jan 11, 2011 6:12 pm UTC

gmalivuk wrote:"Every little bit helps" is a perfectly fine sentiment, as long as you're talking about net benefit and keeping in mind the associated costs.

If "net" means taking opportunity costs and the discount rate into consideration as well as other costs, then yes.
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Re: Using an Abundance of Wasted Energy

Postby Moose Hole » Tue Jan 11, 2011 6:17 pm UTC

I was at a home show one time and someone was selling wind turbines. My house was in a pretty windy area, so I asked about them. He said they did surveys in my area and it's not windy enough to give me any net benefit. This was a very good and honest thing for him to say, but I think their company went bankrupt about a year after that.

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Re: Using an Abundance of Wasted Energy

Postby nitePhyyre » Wed Jan 12, 2011 2:36 am UTC

Technical Ben wrote:I did not say to make the door out of the materials. I was commenting on adding a generator of any type to the door. This will add to the energy needed to push it open. This will add to the calories needed to feed your population (train commuters or hotel users). This will add to the food you need to grow. So unless it is only used on the airport foreign arrivals terminal, it is costing you more than it needs to in generating power.
So to avoid all the unnecessary, and wasteful, steps in between we can just burn food. Or, to be more precise use bio-fuel in power generation. Which is being done already.

Have you ever actually walked through a revolving door? I don't know about the ones where you live, but the ones where I live are very hard to turn as it is. They already have added resistance. Just replace the systems already in place to slow it down with a generator. I don't see how that TCO could be higher.
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Re: Using an Abundance of Wasted Energy

Postby Carnildo » Wed Jan 12, 2011 8:36 am UTC

nitePhyyre wrote:
Technical Ben wrote:I did not say to make the door out of the materials. I was commenting on adding a generator of any type to the door. This will add to the energy needed to push it open. This will add to the calories needed to feed your population (train commuters or hotel users). This will add to the food you need to grow. So unless it is only used on the airport foreign arrivals terminal, it is costing you more than it needs to in generating power.
So to avoid all the unnecessary, and wasteful, steps in between we can just burn food. Or, to be more precise use bio-fuel in power generation. Which is being done already.

Have you ever actually walked through a revolving door? I don't know about the ones where you live, but the ones where I live are very hard to turn as it is. They already have added resistance. Just replace the systems already in place to slow it down with a generator. I don't see how that TCO could be higher.

With the revolving doors I'm familiar with, the "systems in place" are the rubber seals between the door and the frame -- the ones that keep the drafts out. You can replace the seals with a generator, sure, but I bet the heat lost through leakage is far more than the energy you'll recover from people spinning the door.

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Re: Using an Abundance of Wasted Energy

Postby Meteorswarm » Wed Jan 12, 2011 9:26 am UTC

Carnildo wrote:With the revolving doors I'm familiar with, the "systems in place" are the rubber seals between the door and the frame -- the ones that keep the drafts out. You can replace the seals with a generator, sure, but I bet the heat lost through leakage is far more than the energy you'll recover from people spinning the door.


Presumably a sensible implementation would use the axis in the middle for power transfer, not the edges or bottom of the door.

Still doesn't make a lot of sense.

Also, the side doors aren't just for the handicapped. Ever notice how (at least in the US, but this is probably global) they always open outwards? There were some really nasty fires where a lot of people died because panicked people pushing on a revolving door won't let anybody through. Normal doors that open outwards solve this.
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Re: Using an Abundance of Wasted Energy

Postby Zamfir » Wed Jan 12, 2011 9:40 am UTC

Meteorswarm wrote:
Carnildo wrote:With the revolving doors I'm familiar with, the "systems in place" are the rubber seals between the door and the frame -- the ones that keep the drafts out. You can replace the seals with a generator, sure, but I bet the heat lost through leakage is far more than the energy you'll recover from people spinning the door.


Presumably a sensible implementation would use the axis in the middle for power transfer, not the edges or bottom of the door.

No, the point is that the friction of the doors is caused by seals that are needed anyway. You can;t take away the seals and then add a generator. You can only add a generator on top of the seals.

The main point of revolving doors is that they are good at keeping heat inside even when many people enter and leave the building. If you compromise that function by removing seals, you do far more damage then you gain by the generator.

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Re: Using an Abundance of Wasted Energy

Postby Technical Ben » Wed Jan 12, 2011 10:19 am UTC

gmalivuk wrote:
Technical Ben wrote:As would it not be better to just get everyone to go to the gym, and use dynamo connected gym equipment?
You could *also* put generators on gym equipment, sure. But it's not very likely you'll be able to get lots of additional people to go to the gym regularly, whereas it's pretty certain people will continue to go through doors.

I see picket lines outside of politicians and economical offices. "We want our doors OPEN!"
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Re: Using an Abundance of Wasted Energy

Postby Meteorswarm » Wed Jan 12, 2011 8:06 pm UTC

Zamfir wrote:No, the point is that the friction of the doors is caused by seals that are needed anyway. You can;t take away the seals and then add a generator. You can only add a generator on top of the seals.

The main point of revolving doors is that they are good at keeping heat inside even when many people enter and leave the building. If you compromise that function by removing seals, you do far more damage then you gain by the generator.


I thought the discussion was about adding a generator on top of the existing doors as-is and then whether the accompanying added resistance was worth it. The existing seals probably are doing double duty now to slow the door down, and might be able to be re-engineered to have lower friction, but I was thinking about this as adding resistance on top of whatever the current state was.
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Re: Using an Abundance of Wasted Energy

Postby gmalivuk » Wed Jan 12, 2011 8:13 pm UTC

The point is, slowing the doors down is most likely an unavoidable byproduct of the seals, though admittedly you also wouldn't want the door to keep spinning too readily so I suppose they *might* be designed to provide more resistance than they really have to.
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