Capabilities

Capabilities

Engineering of Balance of Plant (BOP) for High-Temperature Systems

Laboratory

National Renewable Energy Laboratory (NREL)

Capability Expert

Zhiwen Ma, Janna Martinek

Class

System Integration

Node Readiness Category

2: High-Temperature Electrolysis (HTE)
2: Solar Thermochemical (STCH)
1: Hybrid Thermochemical (HT)

Description

This capability serves as interface engineering for integration of the balance of plant (e.g. solar field, receiver, operations) into high-temperature solar fuel systems. Thermal energy in the temperature range of 600°–800°C is necessary for high-temperature electrolysis process using solid oxide electrolytic cell (SOEC) and hybrid solar thermochemical hydrogen (STCH) production. The low end of this temperature range can be supported by existing molten nitrate salt power tower systems while the high end temperatures will require advanced molten-salt or particle-based concentrating solar thermal (CST) systems currently under development. When integrated with the appropriate storage technology, CST systems can provide non-intermittent hydrogen production at high capacity factors, reducing the levelized cost of hydrogen production.

Capability Bounds‎

NREL uses an integrated suite of solar field, receiver, and thermal storage design tools (e.g. SolarPILOT, SolTrace, Aspen, ANSYS Fluent, COMSOL, etc.) to maximize the performance of integrated H2 component and systems. NREL’s high-temperature optical and heat transfer materials laboratories can be used to develop and characterize advanced materials (high temperature salts, particles, absorber materials) envisioned for high-temperature BOP components and systems.

Unique Aspects‎

Under direction and funding through DOE SETO’s CSP program office, NREL has developed a unique portfolio of integrated capabilities dedicated to supporting the design of CST BOP components and systems. NREL has developed relationships with public and private entities engaged in R&D focused on delivering concentrated solar flux to a centralized receiver and transporting this energy through high-temperature materials. Current and past research partners include SolarReserve and BrightSource (solar field design and integration), Babcock & Wilcox (particle-based thermal system), and Savanah River National Laboratory and University of Wisconsin.

Availability‎

NREL's CST BOP design capability can integrate the hydrogen production with the solar thermal collection and storage for plant overall heat and mass balance. The modeling tools include SolTrace, SolarPILOT (both are freely downloadable), energy balance and component design analysis, and need support to maintain the capability. The Thermal Energy Storage laboratory in NREL ESIF is user facility for characterizing the CST heat transfer media for high-temperature application.

Benefit‎

Proper design and configuration of the solar field and other BOP design is often ignored, yet is a critical element for delivering high-temperature thermal energy in the range of 600°–800°C required for SOEC or hybrid STCH, and for delivering solar energy to two-step STCH processes for temperatures above 1,000°C.

Images

Figure 1. chemical-looping CSP system integrated including BOP Rendering (top), SolarPILOT solar field optimization tool (middle left) and SolTrace solar field and receiver ray trace software (middle right), and chemical looping for STCH processes (bottom).

Figure 1. chemical-looping CSP system integrated including BOP Rendering (top), SolarPILOT solar field optimization tool (middle left) and SolTrace solar field and receiver ray trace software (middle right), and chemical looping for STCH processes1,2 (bottom).

Raytracing of five tube reactors inside a solar cavity receiver

Figure 2. Previous raytracing with all 5 tube reactors inside a solar cavity receiver.

Planar cavity receiver concept for solar reactor receiver

Figure 3. Planar cavity receiver concept for solar reactor receiver3

References‎

  1. Ma, Z., Davenport, P. & Saur, G. System and technoeconomic analysis of solar thermochemical hydrogen production. Renew. Energy 190, 294–308 (2022).
  2. Ma, Z. Chemical Looping Fluidized-Bed Concentrating Solar Power System and Method, USPTO Patent Number 9,702,348 B (2017).
  3. Ma, Z. and Martinek, J. Analysis of Solar Receiver Performance for Chemical-Looping Integration with a Concentrating Solar Thermal System. J. Sol. Energy Eng. 141, 021003 (2019).