Decarbonisation Technology August 2022 issue

Feature

Solid Particle Technology

Molten Nitrate Salt Technology

Molten Chloride Salt Technology

Gas Receiver Technology

Operating

Ambient to >1000°C

~300-600°C

~400-800°C

Ambient to >1000°C

temperatures Solar flux

No flux limitations

Limited to tube- wall fluxes of

Limited to tube-wall Limited to tube-wall fluxes

on particles

fluxes of 800- 1200 kW/m 2

of 800-1200 kW/m 2 or

800 kW/m 2

less depending on gas- side heat-transfer coefficient

Freezing

No freezing

Freezing below

No freezing

200-300°C; requires

trace heating

Corrosion

Inert materials, non-

Corrosive to

Extremely corrosive to containment materials in presence of air or water

Potentially corrosive depending on gas

corrosive

containment materials

Storage

Direct thermal

No direct thermal storage; requires intermediate heat exchanger

storage

Ducting and containment

No hermetic seals

Hermetic seals

required

Conveyance

Particle lift (bucket elevator or skip hoist)

Long-shafted pumps

High-temperature

blowers; lifts for particles if used as storage media Table 1 Comparison of CSP technologies using different heat transfer and storage media Credit: Sandia National Laboratories

Solex is collaborating on Sandia’s $25 million US award to build a 1 MW demonstration plant for CSP technology. The CSP configuration utilises a heliostat field to directly heat solid particles that would then go into a hot storage silo (see Figure 4 ). For this project, MBHE technology based on the VPE’s diffusion bonded know-how and expertise is being used to transfer stored thermal energy at temperatures greater than 700°C to a sCO₂ power generation flow loop. Solex is also working with Sandia to supply a 2.5 MW thermal heat exchanger using vertical tube MBHE (VT-MBHE) technology. This is part of a test programme to evaluate the performance of an upstream solar receiver. In this project, the VT-MBHE is being used in the solid media cooling loop using ambient air. This project is anticipated to be installed and commissioned in Q4 2022. In another CSP LD-TES development, Solex

and VPE are working with Heliogen Inc. on an advanced particle-to-sCO₂ MBHE for a 5 MWe power block. This is anticipated to be the first and largest commercially integrated recompressed Brayton cycle power block coupled with thermal storage from a CSP field. This project includes a test loop that is being developed to evaluate and optimise the performance of the MBHE – first at the 1 MW scale prior to the implementation of the 5 MW commercial installation. Solex and VPE are providing both a diffusion bonded particle-sCO₂ test exchanger and a hot air-to-particle heater (to simulate a CSP field in the test loop) for the test loop. Meanwhile, King Saud University in Saudi Arabia is pursuing CSP to generate hot compressed air that would then drive a power generation turbine. The hot air comes from thermal energy stored in sand or other particle media, with the thermal energy provided by a CSP plant.