Dick’s Recent Comments

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  Waste heat to power

  Paintbrush, your analysis is correct as far as it goes.  However, consider that power produced at an industrial site using its waste heat is power that will NOT be produced by the utility supplying power to the industrial site.  The waste heat power is emission-free, while the utility power is full of polution.  This is a huge net environmental benefit.

  AP, you are a skeptic in the true sense of the word.  I have consistently faced your cousins over the last eight years trying to raise money to prototype a newly invented engine that will convert waste heat to power more economically than any current technology.  Sean has done a great job responding to your questions, but let me add a little more information to the pot.

  First, some comments on the scope of the opportunity.  Glass ovens generally operate at around 2500F.  Because they are fuel-fired, they must have an exhaust - you can't just keep the heat inside forever.  The exhaust temperature in the flue is between 1500-2000F.  You won't believe (I didn't until I saw it) that glass manufacturers generally let this exhaust go up the stack.  Why?  Two reasons: one, management of low margin businesses rarely allocate scarce capital to energy efficiency projects - they need the capital to keep their technologies current; two, the economics of collecting the heat and re-routing it back to the incoming gas burner air just aren't good enough to warrant the cost - simple economics.

  Another point to make is that glass ovens are NEVER shut off - it costs too much to heat them back up again.  OK, every few years they will shut down for maintenance.  Most capital- intensive commodity-type industries - glass, metals, cement, ceramics - are pretty much the same.  This is where most of the waste heat is, so the capacity factor of waste heat power plants can be very high.

  My company, ReGen Power Systems, has designed a modified Stirling-cycle engine to convert industrial waste heat to power.  The group may be interested to know that Robert Stirling, the inventor of the Stirling engine, actually patented an economizer as part of his engine.  The real invention behind his engine was the re-use of lower temperature heat rather than exhausting it as steam engines did.  Today's Stirling engine incorporates what is called a regenerator, but it is really just an economizer.  The reason that Stirling engines are often considered attractive is because they retain this heat and, therefore, have a higher Carnot efficieny than other engines.

  We will have engines that operate at two temperatures - 250C (490F) for exhaust heat as in the glass case, and 100C to condense low pressure steam.  In the latter engine, the latent heat of condensation is the energy used by the engine, rather than any significant temperature differential.  We see very large opportunities for it in the other commodity businesses that produce so much of the waste heat Sean refers to -paper, oil refining and petrochemicals.

  This all sounds so easy, you're thinking, why didn't we already do this?  In our case, our inventor figured out how to operate the engine at these lower temperatures.  No one else has, and until oil gets to 100 bucks, who cares?

  Sean, great job in your analysis of the nation's smoke stacks and in promoting waste heat to power.

  Dick

  On A very promising climate change solution with an image problem posted 1 year, 4 months ago 15 Responses

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  Waste heat to power

  Good summary of Stirling Energy Systems; however, all Stirling engines are not alike.  SES uses a very high temperature engine (800+C), resulting in higher cost materials and damage from creep stress.  Ultimately, the engine will fail at a lifetime well below where most industrial buyers would invest (40,000 hours?).  Also, at these pressures, temperatures and engine speeds (3000psi, 800C and 50hz), it is impossible to keep the hydrogen locked in very long, requiring regular rechargings to maintain rated power.

  ReGen Power Systems has designed a Stirling-type engine to operate at 250C, a temperature at which creep stress is not an issue and high cost materials unnecessary.  At 1000psi, 250C and 5hz, the difficulty of retaining the hydrogen is diminished.  We have also designed to recharge the engine automatically.  We will make a 500kW prototype and sell to the industrial waste heat market.

  Dick

  On Development in waste-heat-to-electricity technology posted 1 year, 5 months ago 11 Responses