An efficient heat engine for ocean thermal energy conversion

Carbon-dioxide-absorptive ocean thermal energy conversion (OTEC) holds the promise to provide 2-3 orders of magnitude more energy than current world consumption from fossil fuels, nuclear, hydroelectric, and all other alternative energy sources combined. However, the ten-fold capital costs of ocean thermal energy over ubiquitous coal-fired power plants discourages OTEC’s popular use, and this proposed cycle is estimated to be one-fourth the cost of coal. This will make OTEC more profitable than coal-fired electricity. Current OTEC technology uses a phase-change Rankine cycle, boiling either pressurized ammonia-working-fluid in a closed cycle or vacuum flash boiling warm seawater in an open cycle, and then passing through a spinning turbine. Their efficiencies hover around 1% versus the possible 7% Carnot efficiency. This new thermal cycle has some similarity to an Inverted Brayton cycle’s (IBC) colder core than intake or exhaust; it has similarity to the Brayton cycle’s ramjet momentum-driven no-moving-parts compression. This thermal cycle is more efficient than the IBC or Rankine. It has a theoretical thermal-to-mechanical efficiency of more than twice the current OTEC systems. OTEC is available in oceans which cover 70% of Earth, a decentralized resource, and therefore will hopefully mitigate centralized fossil energy resource conflicts. Thermal physics led to this improvement over the open Inverted Brayton cycle used as a bottoming cycle. The preliminary experimental results were far less than theory and were later attributed to air viscosity and turbulence ignored by my theoretical thermal Physics. The solution required engineering knowledge in the realm of Reynolds numbers, friction factors, and Navier-Stokes computational fluid dynamics solutions to optimize the venturi so that it would approach its theoretical efficiency. I therefore chose my co-discipline in Mechanical Engineering. Computational fluid dynamic simulations were then compared to Physics equations of state. When the size of this new thermal cycle is scaled-up large enough then the viscosity becomes insignificant and the thermodynamics shine within the simulation. This Dissertation research is only the first of two needed parts. This open cycle converts heat into kinetic air flow. The second part left unfinished by this Dissertation is the conversion of the kinetic air flow into electrical generation via coronal electrohydrodynamics, already designed but will be modeled at a future date beyond school upon advice to limit Dissertation scope. Wind blades could be used within the sustained airflow from this thermal cycle to create rotational mechanical energy and then drive a normal rotational electrical generator, but that would bring us back to the inefficiencies associated with rotating airfoil turbulence losses. Towards the end of the Dissertation will be the CFD results and discussion. After the CFD results will be a copy of the last submitted but not accepted peer-reviewed journal manuscript.

Name thesis:degree_name

Ph.D. (Doctor of Philosophy)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Physics (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2022

Author dc:creator

• Pederson, Mark A.

Advisor dc:contributor.advisor

• Zhu, Da-Ming, 1957-

Handle dc:identifier.uri

https://hdl.handle.net/10355/90321

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/90321