Session: 18-05 HelioCon Modeling & Training

Paper Number: 142409

142409 - Impact of Process Temperature on the Cost of Concentrating Solar Thermal Industrial Process Heat 

Abstract: 

Concentrating solar thermal (CST) power towers can provide high flux concentrations at commercial scale. As a result, CST towers exhibit potential for high-temperature solar industrial process heat (SIPH) applications. However, at higher operating temperatures, thermal radiation losses can be significant. This study explores the trade-off between thermal radiation and optical losses for SIPH applications using a collection of three case studies at operating temperatures that range from 900-1,550 ^oC, and compares the relative levelized costs estimates for a CST tower system to the receiver target temperature assuming cost assumptions for current commercial CST technologies. We assumed a cavity receiver and polar heliostat field for our analysis. We restrict the analysis to the costs and performance of the tower, cavity receiver, and a polar solar field so that the analysis is agnostic to the end use. We assume blackbody radiation to represent the thermal losses at the cavity receiver and we use ray tracing to estimate the optical losses. We then optimized the tower height, receiver acceptance angle, and field layout to first maximize system efficiency and then to minimize the levelized cost of thermal energy generation. The results show higher flux concentration requirements as the temperature increases and a decrease in the maximum attainable system efficiency as process temperature increases due to radiative heat losses. We find that using current cost assumptions for CST technologies, the levelized cost of producing SIPH increases significantly as the process temperature increases. The optimal solar field size and concentration ratio are both larger when optimizing the system design to minimize LCOH instead of maximizing efficiency. However, whether optimizing for system efficiency or levelized cost, we found that the optimum field size decreases as the process temperature increases and is considerably smaller than the size of solar fields used by solar power tower for commercial electricity generation. The results of our study illustrate the importance of considering the temperature of an industrial process when determining system design and levelized cost goals when using CST technologies to produce process heat at high temperatures. We note that we use cost assumptions for current power tower technology that operates at a target temperature of about 565 ^oC, and that these cost assumptions are likely not valid at the process temperatures studied. Commercial scale designs for the cavity receiver and tower do not exist, making cost estimates of high temperature SIPH systems difficult. For this reason, we do not include absolute values of our levelized cost estimates. Costs are likely to increase with process temperature so our estimates are likely on the low end. Still, the cost trends, especially for a given process temperature, are still valid and informative.

Presenting Author: Alexander Zolan National Renewable Energy Laboratory

Presenting Author Biography: Alex Zolan is a researcher in the Thermal Sciences Group at NREL. His recent work involves the development of models that seek optimal design, dispatch, and operations of concentrating solar power and hybrid energy systems. He currently co-leads the Field Deployment task of the NREL-led Heliostat Consortium.

Authors:

Evan Westphal National Renewable Energy Laboratory
Kenneth Armijo Sandia National Laboratories
Chad Augustine National Renewable Energy Laboratory
Alexander Zolan National Renewable Energy Laboratory