Alternative Power, but with existing tech

Great Debates
1

So, I just had an idea. I think about ways to reclaim power from things we would be doing anyway. So I wanted to know what people thought of this one.

What about lining interstates with small wind turbines? Every time a 90 mph gust goes by, we get a couple of watts. We’re doing the driving anyway, and we probably have mountains of data that tell us where people are most likely to be flying by. Imagine how much could come from semi traffic alone. This could be done with small little turbines that could be mass produced very cheaply.

Thoughts?

2

My initial thought is it would cost more in energy spent than we’d ever get back out of it. I’d say tidal energy is a better place to put our money into if we are going for this kind of thing.

Better yet, build nuclear power plants…

:wink:

-XT

3

Aside from the not-inconsiderable initial investment in time, money, and yes, energy, you’re talking about lining the interstates with windmills to catch a tiny, tiny amount of juice. Frankly, you’re going to lose more from transmission losses than you’d ever get back.

TANSTAAFL: There ain’t no such thing as a free lunch.

4

I’m not talking about big massive windmills but small ones.

5

I thought that windmills needed some sort of sustained wind to operate. More interesting would be if we could make tractor tailers go electric and put solar panels on the roof of the cargo trailer.

6

I heard a similar scheme regarding some sort of piezoelectric matting that could be installed in busy traffic areas - thing is, that energy has to come from somewhere - and it comes from the fuel you’re burning to move the vehicle - so in the case of the matting, it would generate power by braking the vehicle.

Less so with your turbine idea - but if you extract energy from the moving air, you slow it down, making it harder for other cars to push through - less of an effect there though - as you could place the turbines where they’re only affected by air currents that would have dissipated anyway, but I’m not sure they’d ever generate useful amounts of power.

7

The energy expended in just manufacturing and installing a gazillion mini-windmills would be greater than what they could capture before they all started falling apart from exposure to rain and/or snow.

Personally, I’m looking forward to a superconducting power grid that can transmit without loss, so if somebody wants to build a reactor way the heck out in the middle of nowhere, they can still get the juice to the cities. Similarly, we can have mid-sized (but not uselessly small) windmill and hydroelectric generators in areas where the power potential is the most concentrated. Individual landowners can be encouraged to slap up solar panels and inject the surplus into the grid.

We don’t need a whacky scheme - we just need to improve what we already have.

8

If we REALLY want a wacky scheme we could power the world off of Natural Gas for a couple million years…there are literally lakes of the stuff on Saturn’s moon Titan (as well as on a couple of other moons)…

Now THAT is a wacky scheme if ever I heard one! :slight_smile:

-XT

9

And we can get free thermometers on Mercury!

You raise a point that’s always bugged me in sci-fi stories like V and Independence Day in which aliens come to raid Earth’s resources. With their tech, they could far more easily harvest asteroids or comets and not have to deal with trying to lift their plunder out of Earth’s gravity well.

10

:stuck_out_tongue:

Yeah, the sum total of all the resources on the Earth pale in comparison to what is in the solar system. Supposedly on Titan alone there are several orders of magnitude more hydrocarbons than there ever were on the Earth…and that is just one moon. That’s why I never get TOO riled up when various Chicken Little types start hand wringing that we are running out of this or that resource (and it will be TEOTWAWKI! I really feel fine…). Oh, to be sure we can’t go get that stuff now (well, we COULD, but it wouldn’t be a picnic), but we probably will have the capability before civilization comes crashing down.

And it makes more sense than mini-wind generators sucking the breeze off of our cars and such…

-XT

11

Somebody was describing to me an idea for powering the lights in the subway from piezoelectric pressure matting under the walkways. I was trying to tell them that that energy would just come out of the food the pedestrians eat, so the people would be paying for it through higher grocery bills. Kinda works out to the same thing…

12

The latest studies in the Golden Gate straits of San Francisco showed no way to break even. (The mayor didn’t like the study, though and fired people in charge)
Basically, tides are slow. Putting a generator there is close to building a dam in the middle of a lake, there’s some flow but nothing steady like a river.

13

What about the gulf stream? That’s pretty constant and it’s pretty heavy to. Do you have a cite that none of these efforts are break even? Because I was under the impression that this was viable.

-XT

14

The power industry is exploring some new ways to try to improve efficiency on existing plants, especially fossil steam plants (coal versions of which make up 50-55% of our electrical generation in the US). If every coal plant could on average be improved 1% in efficiency, that could result in a savings of about roughly 20 million tons of CO2 per year (assuming roughly 1,950 million tons of CO2 produced for all US coal plants per year). Think about the entire coal plant cycle:

  • Fuel is turned into steam at about 83-90% efficiency.
  • Steam is turned into electricity at about 35-47% efficiency.
  • Electricity is sent to your house at about 90% efficiency. (see T&D losses realtive to Net generation on here: http://www.eia.doe.gov/emeu/aer/pdf/pages/sec8_3.pdf)

Air heater improvements at power plants could result in a 1% improvement in efficiency, yet it’s like pulling teeth to get anyone to do them because coal is so cheap, it’s hard to justify the payback period. In other words, it makes economic sense to waste that 1%. Advanced plant controls including neural networks are a bit oversold, but from the ones I’ve actually tested and worked on, you could get another 0.5 to 1% efficiency increase, depending on the situation. Improvements in coal storage and drying could result in up to 1% improvement in efficiency. Switching to variable-speed fan motors could result in a few tenths of a percent efficiency for the plant overall.

Solar feedwater heating is something that has been seriously looked at for the steam side. We’re getting lots of requests for studies, but very, very few serious applications. Active monitoring of condenser cleanliness, improved feedwater heater leak monitoring, advanced turbine blade systems - these can add a few more percent here and there. But again - coal is just so damn cheap that there are few projects where there is an actual economic payback. A carbon tax would of course change that, and could very well drive a sudden 1-5% improvement in efficiency across the board within a year for coal plants - saving maybe as much as 20-100 million tons of CO2 per year.

15

Heck, how about subsidizing those little tire valve caps that change colour if your tire pressure is too low? I was thinking about buying a set and I admit the one-time price would likely pay for itself over a year or so, but I haven’t gotten around to it and I’m a bit concerned about somebody swiping them.

16

Umm, no, that argument doesn’t follow. People will eat and walk anyway, so the cost to the individual providing the power is not increased.

17

The problem with this scheme is that if you look at things a different way, we don’t really burn hydrocarbons for energy. Instead, we react free oxygen in the atmosphere with various things for energy. The energy is generated because there is all this oxygen in chemical disequilibrium in our atmosphere, and of course, the oxygen is produced as a byproduct of photosynthesis. You can drop a lighted match into a lake of gasoline on Titan, and nothing would happen, assuming you could light a match in the first place.

The limiting factor therefore isn’t the amount of stuff we can find to burn, the limiting factor is the amount of oxidizer we have, and the sustainable amount of oxidizer is limited by the annual photosynthesis output.

This ignores the effect of dumping all that CO2 into the atmosphere of course, we’d probably see negative effects from high CO2 long before we saw negative effects from low O2.

18

Or maybe they’d eat the same amount and lose weight. Hell, we ought to just stick mini-stationary bikes under the desks of every office worker, connect the bikes to electric generators, and then make them pedal all day. Clean energy and a cure for the national obesity epidemic! :wink:

That said, I’m not sure I really understand why piezoelectric pressure matting would cause people to burn more calories. You expend energy lifting your foot up off the ground, with the amount of energy determined by how far you lift your foot and how much your foot/leg weighs. As you let your foot fall, gravity is doing the work of converting the potential energy you produced by lifting your leg into kinetic energy. When your foot hits the floor, the kinetic energy your foot has is transfered to some sort of microscopic stretching of the intermolecular bonds of the floor and then dissipated as heat. If the floor is made of a piezoelectric material, some of that energy becomes electricity instead of heat. But unless the piezoelectric matting requires you to lift your leg higher or stomp down extra hard, I don’t really see why you’d be expending more energy.

That said, I expect it would take a long time for the amount of energy produced to make up for the energy cost of manufacturing and installing the piezoelectric mats, to say nothing of the financial cost.

19

I’m not sure I’m following you there Lemur866. Are you saying that if we brought back tanker loads of natural gas from Titan (let’s leave aside HOW we’d do that), that we’d be limited in our use of this resource due to…oxygen? That if we switched our entire infrastructure to natural gas we couldn’t use it because of a lack of oxygen?? Or am I mis-underhearing you there?

As to more CO2 in the atmosphere, maybe I’m wrong, but my understanding was that some of the new technologies using natural gas are MUCH cleaner than our current technologies…all that is lacking is a means of getting huge quantities of natural gas cheaply. To which, there are oceans of the stuff (well, big lakes anyway) on several moons in the solar system.

Granted, it’s not cost effective (or even possible) to get to those resources today…but I don’t see any show stoppers for us to be able to get to them one day if we need them badly enough.

-XT

20

I think folks sometimes lose sight of the fact that there are cheaper ways to improve efficiency using existing technology right off-the-shelf, and reduce GHG emissions.

So I’m going to give you a real-world example, with real numbers, but for an unnamed power plant. All I’ll say is it’s a US coal plant, East of the Mississippi, that serves about a quarter million homes.

Currently this plant emits about 1,185,000 tons of CO2 per year, and doesn’t produce power as efficiently as it might. The reasons for this are varied, as I will demonstrate. I looked at things on a 10-year basis.

I recommended a lot of possible upgrades for them to improve the efficiency of their power plant. The first thing is a simply having boiler tuning experts come out and improve their plant efficiency by running tests on damper positions, fixing some leaks, and improving combustion tuning. The cost for this is roughly $50,000 per year, and there is the potential to save about 9,000 tons of CO2 emitted. So over 10 years (using simple math, not taking into account escalation, NPV…this is just an SDMB post, after all) we get.

Boiler tuning: Spend $500,000, save 90,000 tons of CO2 ($5.55 per ton)

The next thing up is looking at repairing an abominable air heater, which is a huge energy waster. Fixing this critter will save about 29,710 tons of CO2 per year, and cost $1,200,000 the first year, with other costs of $100,000 every 2 years, with CO2 savings decreasing slightly in-between the “touch-up” costs. So:

Air heater repair: Spend $1,600,000, save about 267,390 tons of CO2 ($5.98 per ton)

Next we have installing a new control system with closed-loop neural models, which will allow much finer boiler operation. This system costs $1,300,000 initially, with $150,000 per year added on. It can save about 18,000 tons of CO2 per year. So:

Advanced boiler controls: Spend $2,650,000, save 180,000 tons of CO2 ($14.72 per ton)

Finally, we have a turbine upgrade, which would improve their LP efficiency by quite a bit, and fix some HP blade problems as well. This sucker costs about $4,500,000 and will save about 30,000 tons of CO2 per year, with the savings declining over time due to gradual loss of improvement. So:

Turbine upgrade: spend $4,500,000, save about 255,000 tons of CO2 ($17.65 per ton)

So the short of it? A carbon tax of about $5 a ton would drive this plant to make probably two immediate upgrades, and could influence them for a 3rd. The net savings would be more than a third of a million tons of CO2 emitted at their current generation rate. These solutions are standard solutions, using standard off-the-shelf tech, and there are numerous vendors available to help them. Total downtime for the first two items would be about 4-6 weeks for the air heater, and a couple of days each year for the boiler tuning.

Now…I probably know about a hundred coal units that are the same size or larger as this one which could benefit to the same level as this hypothetical case. In reality, there could be 300-400 or so that could be in this same situation. Let’s just take 100 – we would be looking at saving millions of tons of CO2 using standard off-the-shelf tech and processes, with minimal downtime.

Oh, you might be wondering what the net cost is, right? Well – this plant generates about 1,100 GWh of electricity each year. That’s 1,100,000,000 kWh. Spending a total of $2.1 million over 10 years, with 11,000,000,000 kWh generated over that 10-year period, results in an increase in cost to you, the consumer, of 0.19 cents per kWh, or 0.019 cents per kWh per year. For an average electric bill in that area, that might increase your annual electric bill by 0.16%. If your total annual electric bill is about, oh, $1500 a year, then you pay $2.39 per year as your part to save a third of a million tons of CO2 from being emitted. You are not going to get that ROI too many other places.