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June 12, 2007

Comments

Tim

What's the difference between this technology and a Sterling engine?

Vit

Sounds like Stirling where working fluid is actually a fluid. Apparently the design is different from Stirling.

Volker

From what I read that is not a Stirling system. In a Stirling motor you have two pistons and move the internal gas from cold to warm cylinder (and vice versa).

From the descriptions here you only have a single, sealed cylinder. Instead of moving the internal gas around (as in a Sirling) they switch between heating/cooling water. As this means re-cooling/heating the cylinder I guess the efficiency is worse than that of a Stirling, plus there is more stress to the material (due to the heating/cooling cycles) leading to earlier fatigue in the cylinder material.

Peter Hunt

I sure would like to see the details in terms of output efficiency., start up cycles, the elements that determine it's effectiveness such as working fluid. Is there any phase change? How many lbs per HP?

Don't get me wrong, I like bottoming cycles but this seems to massive to be pratical for any thing but a low HP steady state installation.


Can you explain the Erricson cycle?

Peter Hunt

I sure would like to see the details in terms of output efficiency., start up cycles, the elements that determine it's effectiveness such as working fluid. Is there any phase change? How many lbs per HP?

Don't get me wrong, I like bottoming cycles but this seems to massive to be pratical for any thing but a low HP steady state installation.


Can you explain the Erricson cycle?

Reality Czech

Efficiency and power will both be poor.  This is essentially a Newcomen engine with the cylinder and boiler combined.  The cylinder will have to be heated for each power stroke and cooled for each condensing stroke, making the operation very slow and losing efficiency due to the extra heat transferred without doing useful work.

Stephen Boulet

What if the piston/cylinder were made out of some material with a low thermal mass, like ceramic? It seems like the pressure would need to be high to have CO2 liquid at these temps.

Stephen

Stephen Boulet

What if the piston/cylinder were made out of some material with a low thermal mass, like ceramic? It seems like the pressure would need to be high to have CO2 liquid at these temps.

Stephen

Reality Czech

Reducing the losses due to the bad design does not eliminate them.

The inefficiencies of engine designs like this have been known for centuries (literally).  The only way someone can claim this as an improvement, and get people to believe it, is a pervasive ignorance of basic thermodynamics.

RML

I'll bet they are using a Malone cycle. The expansion ratio of a liquid is fairly good near the critical point so you can get a good density change with relatively low dT.

Efficiency of the Malone can be very good as well (reported similar to Stirling in Malones' original work) but much depends on the regenerator and overall engine design.

Also, as a guy that worked on many Stirling engines, I can tell you that the cyclic stress from pressure is much easier to deal with than the low cycle fatigue of heating up a Stirling engine (800 C) for each start.
High pressure sealing of a piston for the Malone is the big challange though...

donb

There must be hundreds of ways to make inefficient engines. This looks like yet another.

RML mentions cyclic stress from pressure (which all reciprocating engines have). But to make this one work, there is cyclic thermal stress as well.

The design relies on a single heat exchanger. This means it will see cyclic thermal stress. Also, if there is only one heat exchanger, either it must be thoroughly drained each half-cycle, or the hot and cold fluids will mix. Any mixing will cause further loss of efficiency, and may be undesirable for other reasons (e.g., hot brine contaminating and cold fresh water).

Good observation by RML about using fluids around their critical point - for CO2 it is 88°F.

The original posting links to a web site with further information. Some extravagant claims are made, such as no valves for the engine (thus simple and less friction). While there may not be valves for the working fluid, there certainly are valves for the hot and cold fluids running through the heat exchanger. So complexity and friction are back in.

Perhaps a better engine would have two cylinders - a small one pumping CO2 liquid and a large one pumping CO2 gas, with a hot heat exchanger in the CO2 flow from the small to large cylinder, and a cold heat exchanger in the flow back (plus appropriate valves for the working fluid). No excess thermal cycling, no mixing of hot and cold fluids.

There is nothing wrong with low efficiency designs that tap into waste energy if they can be done cheaply. But it looks to me that a better design could extract more shaft power from less waste heat using less material.

Engineering is the art and science of doing for $1 what any damn fool can do for $3.

Stephen Heyer

I think all the discussion about efficiency is pointless. From what I read, I gather the whole point of this engine is that it works off low grade waste heat, essentially free energy (you don't have to pay for it).

All that matters is that it do whatever it is supposed to - say pump oil, with, in effect, free energy.

donb

Stephen - read my last two paragraphs.

casey

Why is DOE sinking money in this if it is nothing new?

casey

I am familiar with a facility that produces 75,000 ACFM of flue gas at 430 deg F. What is the best way to convert it to electricity with the greatest efficiency without spending > $1 million? What efficiency should we be shooting for? Lets make money!!

RML

Hey Casey,
A lot depends on your ability to reject heat and the flue gas composition but a few things to consider:
If you want really cheap, you could use a steam engine- compound expansion if you want to get fancy.
A better system may be an organic rankin. You won't want to loose the working fluid with this so probably best to use a motor technology that's easy to seal with a rotary shaft seal. It's probably cheapest and easiest to use a vane motor but you could also use a screw expander or if you really want to get tricky, use a turbine.

Reality Czech

Casey, what temperature do you need to get proper draft in your stack and avoid condensation of corrosive liquids?  Lofting of the plume to keep the neighbors happy?

Casey C

The temperature of the steam coming out of the wet scrubber is 120 deg F. The plant manger says we can't cool the flue gas below the dew point or we will get sulfuric acid. I don't know what the dew point is.

Manu Sharma

The engine developed by Deluge appears to be a Minto wheel which too produces mechanical energy through heat transfer.

Manu Sharma

Correction:
Just read the original article... looks like there's no wheel in this case, though the conversion is the same as in a Minto wheel.

davea0511

This is very different than anything done before. Fluid expansion only - no phase change. Very interesting. If there are inefficiencies they are related to the design, not the technology. We should look at this the same way we look at the first internal combustion engine - the first of it's kind. Whatever deficiencies exist I'm sure will be engineered away with time, and given it's uniqueness it's sure to find a niche that Stirling and other thermal engines do work as well in (otherwise why not just use a stirling)?

Ice Czar

Patent Number 5899067
and a pimp for https://www.pat2pdf.org/ which I just adore ;)

sreenivasan

can you please explain what is erricso cycle with T-S diagram

Matt

I bet any $$$ that this engine is vaporware or ahem. liquid ware.

I bet it will never see the light of day.

Al

Then check them out in the "light of day" in Hawaii...2 of them

Cyril R.

Organic Rankine is not economical for such low delta Ts. It is a huge challenge to make any system economical for such small temperature difference. Do these guys have it?

Carnot is not the way to go for low temperature heat. If infrared nano antenna's pan out, a plate heat exchanger style generator might be devised with reasonable efficiency. Since emissivity rises to the fourth power of the absolute temperature difference, high grade heat is still desireable even then.

energychina

if the engine is the same as you said, it's great!

Arfima

What is more efficient for high thermal gradient dT=400F: a heat engine with electrical generator OR a thermal electric device (generator)?

Does anyone know of a good source on the web for information on commercial thermal electric?

Engine Additive

Nice post, great detail. I would have liked to see the costs that are associated to it so I could add to my business case justifications to use the technology. Keep up the good work!

Rozer

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CGS intake

It is efficient, reliable and low cost. this should be innovated by now but I can't seem to find it anywhere being used.

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