Compact Heat Exchangers for the Stringent Operating Requirements of CSP Systems
- Makai Ocean Engineering
Concentrating Solar Power (CSP) systems offer promising solutions for grid scale renewable energy; however, wider adoption remains limited by system inefficiencies leading to higher levelized cost of electricity (LCOE) compared to alternative energy sources. Gen3 CSP systems utilize high temperature, high pressure (HTHP, 700°C, 20.8MPa) supercritical-CO2 (sCO2) Brayton cycles to improve system efficicencies but a cost-effective HTHP primary heat exchanger remains a critical technology gap. Specific challenges include: identification of robust materials for HTHP operating conditions; scalable cost of materials and fabrication methods; and understanding the design tradeoffs and challenges of using sCO2 as a working fluid. A cost-effective and reliable sCO2 primary heat exchanger capable of operating in the Gen3 CSP environment does not currently exist. In this work, Makai Ocean Engineering, Inc. has developed a fundamentally new heat exchanger that directly addresses the need for reliable, efficient, and cost-effective HTHP sCO2 heat exchangers and revolutionizes the economic viability of Gen3 CSP systems. Makai’s Thin Foil Heat Exchanger (TFHXTM) technology relies on novel designs and fabrication methods to use 5X thinner raw material than comparable brazed or diffusion-bonded etched-plate heat exchangers while delivering the same pressure capacity (> 20.8 MPa, 3,000 psig). The TFHX consists of individual plates that are stacked together to form a heat exchanger. Individual TFHX plates consist of two pieces of foil welded together in application-specific patterns customized to obtain the optimal internal channel size. The external channel size and flow path length are also customizable to match the required flow rate with the available pressure drop. The internal channel size can be changed independently of the external channel size and vice versa with little impact to pressure rating or cost. This degree of customizability provides a significant benefit for optimization of heat exchanger performance and cost-effectiveness. In this Phase 1 work, Makai demonstrated TFHX pressure capacities from 20.8-34.5 MPa (3,000-5,000 psig) and sCO2 channel sizes from 0.25-0.40 mm using proof-of-concept plates fabricated using Haynes 230, a Gen3 CSP HTHP compatible material. A thermo-hydraulic finite element model was used to determine the size of a 100-MWe particle-sCO2 heat exchanger under varying channel size and flow path length combinations and an economic model was used to determine the most cost-effective particle-sCO2 TFHX design. The result is a projected cost of $50/kWth for a 100-MWe particle-sCO2 TFHX, a 3X cost reduction compared to the 2030 SunShot target of $150/kWth for a primary heat exchanger.
- Research Organization:
- Makai Ocean Engineering
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- DOE Contract Number:
- SC0021797
- OSTI ID:
- 1862036
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-MAKAI-21797
- Country of Publication:
- United States
- Language:
- English
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