I live in an area not too far from some chemical refineries and a couple nuclear power plants (we put the FUN in superfund!). Occasionally we’ll see a steam plume from the power plant cooling towers and we frequently see smoke and/or flames from the smokestacks and towers at the refineries. It seems to me that there should be some way to generate energy from this vented gas.
Could wind turbines be placed in the towers and smokestacks that would be able to turn with the rising gas thus generating power? Could the flames coming from the refineries be used to heat water to turn steam turbines? Are there any logistical reasons why this couldn’t be done to convert some of this lost energy and put it into the grid?
Many times the exhaust gases are being run through a heat exchanger to use the waste heat. The gas from the stacks you see may not be all that hot (relatively speaking).
Using waste heat is one of the first things to look at when trying to improve the efficiency of a plant.
No cite, but the local DJ who does the morning show on my Air America affiliate was ridiculing some pol (McCain? Giuliani? Bloomburg?) the other day for suggesting mounting wind turbines on existing urban structures (The Brooklyn Bridge, I think). He mentioned among other problems that the weight and vibration of the turbines would wreak havoc on the structural integrity of the mounted structure, and did the pol really think it was a good idea to mount enormous machines in the middle of urban areas and guarantee casualties if/when one collapsed. He also said that a standard turbine requires an acre footprint but I have no idea if that’s correct. He was repeating stuff he’d heard at some alternative energy seminar he’d attended a while ago.
That was Bloomberg proposing a Manhattan wind farm. I was thinking more along the line of ducted fans in a chimney, not putting a pinwheel over the exhaust (although that could look pretty cool).
If it’s a fairly new plant, you can pretty safely bet that they’ve already wrung out as much energy from that “waste” as is feasible and cost-effective.
There does come to be a point of diminishing returns - how much can you spend to extract that last percent and not lose money? In theory, you could build a refinery whose waste output is nothing more than cool water, but you’d have to spend a frightening amount of money to wrangle all of that heat and leftover hydrocarbons that your stockholders would dunk you head-first into the first vat of tar they find.
Similarly, the flares that you’re seeing at the refinery are just burning off crummy junk with not much energy in it - most of the flares I’ve seen are a lazy, bloopy flame that looks like it needs encouragement to burn. Burning it is simply the most cost-effective way to get rid of it, as opposed to gathering it in tanks and then trying to figure a use for it. It’s not like they’re burning 93-octane gasoline here.
Hell, you should see the flares around here! We call it our nightlight because, although it’s about 4 miles away, it still lights up the night sky to an infernal orange glow.
You may be underestimating the actual power available from a power plant chimney. First off, the differential pressure between the chimney exhaust and the atmosphere is only a few inches of water. Second, any sort of turbine used to try to extract energy from the chimney will slow the gas down, and remove the chimney effect. Power plants have very large, very power-hungry fans in use just to get the gas to the chimney and able to flow up it in the first place. Sure the chimney draft helps out, but what I’m saying is if you remove that draft by putting restriction in it, you’ll have to increase the power (or the size) of the induced draft (and possibly forced draft) fans at the power plant - thus taking power away from the power plant.
And the vapors from a cooling tower have much, much less energy in terms of differential pressure and volumetric flow. If you put restriction on the air flow from the cooling tower, then you take away from the cooling effect and thus the turbine can’t condense steam as efficiently, and then you end up losing power.
Really, either way you look at it, you’re likely to not only lose energy but you could interfere with the plant systems enough that no one would even think of trying it.
ETA: I’m not even addressing the potential negative impacts to emissions controls systems on the plant, which could easily make it not only a losing proposition, but an illegal one as well.
Exactly! In general, it’s a bad idea from an energy perspective.
Besides a highly corrosive environment that would greatly increase the expense of any sort of turbine installed in the stack, most plants are designed to give the plume adequate velocity out of the stack so that the plume heads up into the atmosphere, not down toward the ground. If the plume heads down, then the plant personnel, local citizenry, and nearby flora and fauna usually do rather poorly in the very low oxygen gas stream. Bad all the way around, unless you’re a liability lawyer.