Comment by rfrey | Hacker News Reader

Comment by rfrey | Hacker News Reader

Hi Rob. I'm CTO of a company that generates electricity from waste heat at industrial facilities. Pipeline compressor stations often generate 35MWth+ in waste heat, which we can use at about 20% efficiency to generate electricity.

Many pipeline compressor stations are not anywhere close to distribution lines so just merrily pump this heat up their stack. Especially with new pipelines where companies are battling (legitimate) environmental concerns, there is no reason they would not install your tech, powered by a heat recovery system, on every single proposed compressor station on the line.

We have actually modeled it with negative operating costs (using technology from one of your competitors) and think we could get the pipeline companies or the government (we're in Canada) to pay for it even in the face of bad economics. If your system is a step change in effectiveness from those systems, it could be a game-changer in this market.

Let me know if you'd like to explore this a bit. My email is in my profile.

> Pipeline compressor stations often generate 35MWth+ in waste heat, which we can use at about 20% efficiency to generate electricity.

Can the waste heat be used for distillation instead? To heat up the fuel/water mix to separate the two cleanly?

It would seem to me that the future of "waste heat" is to actually utilize the heat, instead of powering a relatively inefficient heat-engine. Perhaps instead of 20% efficiency, you get closer to 100% efficiency since all you'd be doing is running the fuel-water mix to the heat-source to evaporate the fuel out (I presume anyway, I'm no chemist)

re: waste heat, I've been thinking forever that someone must capture this. I've generally assumed the economics don't work out or no one has cracked it outside of scenarios like regenerative braking. We waste so much energy that we could capture and put back to use.

Something like 55-60% of the thermal energy created by burning fossil fuels is currently wasted.

It’s kind of ironic that cars and power plants work hard on getting rid of that energy.

Modern power plants work hard at getting every last bit of that energy before it escapes. Current Combined Cycle plants, that generate steam from the exhaust of a gas turbine, are currently getting over 60% efficiency.

One must be a bit careful there. 60% efficiency based on the LOWER heating value of natural gas. That ignores the heat available from condensing the water of combustion. Coal plants typically use the higher heating value when computing efficiency, which does reflect the latent heat of vaporization of that water.

I know ICE engines use turbochargers to "recapture" the energy. Exhaust can be used to power the intake fan, which can increase air-pressure available to the engine's intake.

Turbocharged engined still need a ton of cooling but yes I think they are more efficient overall .

Regen braking doesn’t use waste heat. It converts mechanical energy back to electrical.

And in so doing, reduces waste heat due to friction, which is likely what the parent commenter meant.

Some say it doubles the lifespan of brake pads.

> We waste so much energy that we could capture and put back to use.

The biggest current waste of energy is residential heating. We take high quality energy in the form of natural gas and fuel oil and use it to produce low quality heat.

Co-gen systems burn fuel to generate electricity and use the waste heat for heating buildings.

Your instincts are excellent: using heat directly is always and everywhere better than turning it into a fungible commodity like electricity, only to convert that electrical energy to some other form later. (Creating liquid fuel is no different in this regard.)

The reality is that there's almost never a practical direct use of the heat at the facility where it is created. It is too low quality for the onsite processes. Economizers and Regenerators are two common pieces of equipment that suck out what heat can be used - what's left is too low temperature for whatever they're making onsite.

Sometimes there's an opportunity to broker a deal between two adjacent facilities, where one can use the heat that the other considers waste. But those are rare.

Happy to talk about this until you wished you'd never asked. Feel free to email.

You could certainly do this, using distillation or the thermal processes Carbon Engineering is doing, and it could be worth pursuing, from a business opportunity perspective. We're focused on an implementation that can scale to >300 B gallons per year, so are pursuing an electricity only path.

Thanks. If the scale is lacking, I get it. But to be clear, I’m talking about a series of 10MW electrical power plants each with 95% capacity factor.

Using your number downthread of 60kW/gallon, that translates to about 1.4 million gallons per station per annum - even with dozens of stations per line, a couple of orders of magnitude less than your target opportunity of 300B gallons+.

Would you be willing to expand a bit on your opportunity target of 300B+ gallons/year? My understanding is that the US production of gasoline in 2018 was about 142 billion gallons, so I certainly misunderstand something.

To put this number in perspective: 300B gallons of gasoline is an amount of carbon equivalent to all of the CO2 in the air above all of the earth's land area, up to an altitude of about 80 feet.

If you can pull that off, I'll be impressed; but it seems like a very aggressive target.

It's about half of global annual gasoline consumption. It's going to be hard, but worth it to try.

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