US Energy Dept. Still Holds Torch For Concentrating Solar Power

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Concentrating solar power has had a hard time getting off the ground in the US, but that is not stopping the Department of Energy. The agency is in the middle of a $100 million program aimed at pushing the technology into the mainstream of the renewable energy revolution, and they are not stopping at power generation. Industrial decarbonization is also on the menu. That means more green hydrogen is in play, despite what the skeptics say.

Concentrating Solar Power To Decarbonize The Hard-To-Decarbonize

Concentrating solar power plants are complex systems. Instead of using specialized materials to draw electricity from a solar panel, they deploy specialized mirrors to bounce solar energy from a wide field of points onto a much narrower field, where it heats a store of molten salt or a specialized oil.

The heated liquid can be piped to a generating station, where it boils water to produce steam to run a turbine and generate electricity, as in a conventional power plant. Or, the liquid can be used simply as heat to run industrial processes.

If that sounds expensive and laborious, it is. However, the payoff in terms of carbon-free power can be huge, partly due to the built-in energy storage angle. The Obama administration promoted concentrating solar power as the wave of the renewable energy future, citing its ability to deliver zero emission electricity on a 24/7 basis.

In terms of commercial development, not much came of it after former President Trump took office with a mission to promote fossil energy. The Solar Energy Industries Association currently lists just 11 CSP plants in the US, including several that went online during the Obama administration.

Nevertheless, the Energy Department continued to promote R&D on solar power and next-generation CSP technology all throughout Trump’s term in office.

Additional signs of a CSP revival have been popping up during the Biden administration. One encouraging development consists of a modular approach that skips over some of the site selection issues that have held back the concentrating solar power industry.

Another pathway is the deployment of high heat from CSP plants to run industrial processes, and that brings us to the latest round of CSP funding.

$24 Million To Kick Concentrating Solar Power Into High Gear

The new round of funding will split $24 million among 10 projects in two categories.

One category deals with solid particle technology, which is a relatively new development on the CSP scene. Instead of molten salt, this technology deploys solid particles to transfer solar energy. One key application is to generate high heat for supercritical carbon dioxide systems.

Supercritical CO2 is a liquid, not a gas. One of the advantages of supercritical CO2 systems is their small footprint, which could translate into savings on overall system costs and allow for a greater range of application.

High heat creates new  materials and engineering challenges to solve, and apparently the five projects in this category are well on their way to solving them:

GE Research (Niskayuna, NY): This project will aim to deliver a preliminary design of a supercritical carbon-dioxide (sCO2) power block that is optimized for Gen3 CSP that uses solid particles.

Mississippi State University (Starkville, MS): The project team will develop a novel particle-based thermochemical energy storage system for CSP.

Sandia National Laboratories (Albuquerque, NM): This project will design high-temperature mass flow sensors that use solid particles to move and store thermal energy for the reliable operation of Gen3 CSP systems.

Sandia National Laboratories (Albuquerque, NM): This project will design a modular slide gate system for control of particle flows in CSP receivers, in collaboration with an industrial valve manufacturer.

University of Wisconsin-Madison (Madison, WI): This project aims to develop a prototype particle-to-sCO2 heat exchanger using advanced design and manufacturing techniques.

Next-Generation CSP For Green Hydrogen

The other five projects in the funding pot have to do with industrial processes, and one of those is hydrogen. For those of you new to the hydrogen topic, three things:

1. Hydrogen has been a fixture in modern industrial and agricultural systems for generations

2. The global hydrogen market is also expanding into transportation and power generation

3. Almost all of the global hydrogen supply comes from natural gas, and to a lesser extent coal and other fossil sources

Decarbonizing item #1 is essential, regardless of what the skeptics think about item #2. Reworking whole systems to eliminate human-produced hydrogen is one pathway. Another is to develop alternative sources for hydrogen, and that’s where solar power comes in.

Renewable hydrogen can be produced from biogas and other organic wastes. Hydrogen can also be recycled from industrial waste, but for now much of the activity is centered on electrolysis, which deploys renewable energy to push hydrogen gas from water.

On the solar power side, that means producing electricity from solar panels and applying it to water. Another approach is to provoke a photoelectrochemical reaction by suspending a specialized PV cell in water.

The Energy Department is interested in a third pathway, which involves the kind of high heat that concentrating solar power plants can produce. The $24 million funding pot includes $2.2 million for the University of Florida to “design and validate a highly efficient and scalable solar thermochemical reactor to produce hydrogen from water and sunlight.”

If you’re wondering why not use fossil energy to do the same thing, the urgency of decarbonization is only part of the answer.

Last spring, CleanTechnica caught up with John Shingledecker of the Electric Power Research Institute, who explained that a high-heat CSP system can generate much higher temperatures than fossil power plants can produce.

“A lot of the developments are being taken from fossil power plant steam cycles or coal boilers, but they only go up to 620 degrees C,” he said. “Seven hundred degrees and beyond has been the subject of much study — for example advanced supercritical technology, involving supercritical CO2 power cycles based on CO2 as a working fluid,” he said.

The University of Florida has been researching solar powered thermochemical hydrogen production since 2001.

“Solar-driven thermochemical water splitting cycles (TCWSCs) provide an energy-efficient and environmentally attractive method for generating hydrogen. Solar-powered TCWSCs utilize both thermal (i.e. high temperature heat) and light (i.e. quantum energy) components of the solar resource, thereby boosting the overall solar-to-hydrogen energy conversion efficiency compared to those with heat-only input,” they explain.

More Solar Power — & More Savings — For Heavy Industry

The other four projects in the industrial CSP category are aimed at decarbonizing the cement industry (Heliogen and Sandia National Laboratory), improving molten salt storage tanks (Solar Dynamics), and developing a new chemical reactor to decarbonize the production of propylene (University of Maryland).

As for who’s going to use these CSP systems, that’s a good question. Until costs come down, industrial deployment will have to depend on grants and subsidies.

The Energy Department has a plan for that, too. The agency’s National Renewable Energy Laboratory has just released a roadmap for reducing the cost of heliostats, the specialized mirrors that collect solar energy in a CSP plant.

“These components represent 30-40% of the cost of a CSP system, so reducing the cost of heliostats can make a significant impact on DOE’s goal of $0.05/kwh for CSP plants by 2030,” NREL explains.

In support of that effort, NREL is collaborating with Sandia National Laboratories and the Australian Solar Thermal Research Institute on something called HelioCon, so stay tuned for more on that.

Follow me on Twitter @TinaMCasey.

Photo courtesy of NREL.