Session: 06-03: Concentrated Solar Power II -- Power Block and Components

Paper Number: 131321

131321 - Assessment of Fluidized Bed Heat Exchanger Techno Economics Considering Parasitic Pumping Power 

Abstract: 

The Department of Energy's Solar Energy Technologies Office downselected particle-based concentrating solar power as the technology most likely to decrease the levelized cost of energy to below their 0.05 $/kWh target in 2020. A particularly challenging component within a particle-based system is the particle to supercritical CO2 heat exchanger due to the relatively low thermal conductivity and poor heat transfer characteristics of the particle media. The current state of the art particle to sCO2 heat exchanger is a parallel plate design in which particle flow between an array of sCO2 containing plates. This design suffers from low particle side heat transfer coefficients, but is passive, allowing particle to move downward via gravity. Fluidized bed heat exchangers have widely been used in industry for alternative applications and feature high particle side heat transfer coefficients that can help reduce the cost of the heat exchanger. This increase in heat transfer coefficient is acheived by bubbling air through the particles which increases their movement relative to the tube bundle heat transfer surface. The parasitic power associated with the delivery of air into the heat exchanger introduces a concern about particle-system levelized cost of electricity as more power is required to extract the same amount of heat. A confounding factor is the ability to increase the particle side heat transfer coefficient with increased air delivery. As air flow is increased less heat exchanger area is needed and vice versa. This is a particularly cost sensitive system as sCO2 containing material must operate at temperatures up to 800 C and pressures of 25 MPa, and are therefore composed of expensive high nickle alloys such as Inconnel or Haynes. A study was conducted to assess the opimal parasitic power consumption of the fluidized bed heat exchanger given the cost of material used to construct it. Additional considereations include 1) the ability of the heat exchanger to temporarily increase the heat transfer coefficient to better allow the power block to respond to transients, 2) the trade off between increased pressure drop and heat transfer coefficient on the sCO2 side, and 3) decreased tower height due to the more compact nature of the fluidized bed design compared to the parallel plate system. The results of this study will not only inform the optimal blower power consumption for the currently presented design, but also provide alternative fluidized bed heat exchanger designs a basis for selecting the optimal blower power consumption. 

Presenting Author: Nathan Schroeder Sandia National Laboratories

Presenting Author Biography: Nathan Schroeder is a Senior member of the technical staff at the National Solar Thermal Test Facility within Sandia National Labs. Nathan's research primarily focuses on Generation 3 concentrating solar power technologies and their use in electricity production and industrial process heat applications. Nathan leads projects investigating falling particle receivers, particle to sCO2 heat exchangers, packed bed thermal energy storage, and cement decarbonization.

Authors:

Dylan Lerch Sandia National Labs
Nathan Schroeder Sandia National Laboratories