A few days ago, we reported on a new plan by researchers at MIT that would create clean hydrogen from water using only sunlight. Not just ordinary sunlight, but the power of the sun focused on a single point by an array of mirrors, a technology known as concentrated solar power, or CSP.
It really is just a scaled-up version on that experiment you learned at summer camp where you used a magnifying glass to focus sunlight until it was hot enough to burn your initials onto a piece of wood. The difference between a CSP facility and a conventional solar farm is the captured heat can power conventional supercritical steam turbines for up to 15 hours, whereas the solar farm only produces electricity while the sun is shining. ceramic-sand
Now Australia’s Commonwealth Scientific and Industrial Research Organization — popularly known as CSIRO — says its CSP research facility in Newcastle north of Sydney has announced a breakthrough in its investigation of “falling ceramic particles” technology that captures and stores solar energy as heat.
Dr. Jin-Soo Kim, who leads the solar technologies team, said this week the group has reached a critical milestone temperature of 803 °C (1477º F) for the first time at the falling particle receiver by using a new and novel concept. “This is significant because it creates the opportunity for greater renewable energy storage when combined with our patented heat exchanger,” Jin-Soo said. “This technology is key to delivering low cost renewable energy at scale for the decarbonization of Australia’s heavy industries. Over eight years of development and thousands of hours were invested to reach this outcome.”
The basic idea behind CSP dates back to the 1800s when European inventors tinkered with sunlight concentration. In recent decades, several different concentrated solar thermal power technologies have evolved, ranging from a parabolic dish circled by mirrors to tower systems filled with molten salt. The problem with molten salt is that it cannot get hot enough to take full advantage of the power of concentrated sunlight.
The research team in Newcastle is using ceramic particles as fine as grains of sand that are able to reach ultra high temperatures that are ideal for storing significant amounts of heat. Those heated particles act like a battery, storing energy as heat for up to 15 hours.
“The technology is a smart, cost effective way to store a large amount of high temperature heat for 10 to 15 hours,” said Dominic Zaal, the director of the Australian Solar Thermal Research Institute. He added that traditional CSP facilities are limited by the fluids they use. Molten salt can only handle temperatures of up to 600º C while high temperature oil can only manage 400° C.
However, the ceramic particles the team is working with can endure temperatures of 1000° C. They not only absorb the sun’s heat but also store it, which simplifies the system and reduces costs.
The “falling” part of this method uses gravity to heat these tiny, dark colored ceramic particles less than half a millimeter in size. When dropped from a hopper at the top of the tower, they are heated as they pass through a beam of focused solar energy. As they fall, their temperature can increase quickly from 500° C to 800° C. With more advanced setups, temperatures of more than 1000° C. are possible. Once heated, they are stored in a silo, then used to produce steam for power generation or other industrial tasks.
At first, the particles fell too fast, which allowed them to spread out. That let the sunlight through and reduced efficiency. The answer was a “catch and release” method system that captures them in a trough, slowing them before they are released to fall into the next trough.
“CST doesn’t compete with PV solar energy,” Dominic Zall said. “PV gives you power when the sun is shining, whereas CST takes energy from the sun, stores it and then allows the user to use that energy when the sun isn’t shining, such as overnight or on cloudy days.”
CSIRO says CSP with ceramic particles can offer a dependable and green power source that will make it possible for Australia to meet its goal of closing all of its coal-fired generating stations by 2033. At present, those thermal facilities provide 62% of Australia’s electricity.
CSIRO’s pilot system in Newcastle has 400 mirrors. However, a full-scale installation might use over 10,000 larger mirrors and generate power similar to a 100 MW coal plant. Wes Stein, the chief scientist for solar technologies at ASTRI, said, “The challenge isn’t so much collecting energy from the sun; it’s how to safely and efficiently convert that energy into heat and store it for later use.”
“The power generation from CSP technology resembles a coal fired power plant without the coal. It uses the same turbine. Typical coal fired power plants use a steam turbine that operates at 540 degrees. Instead of using coal to create the heat to superheat the steam, we capture energy from the sun and store it for 10 to 15 hours,” Stein said.
There are currently CSP facilities in 18 counties producing a total of 6460 megawatts of electricity, with another 3859 MW of projects under construction.
In addition to generating electricity, Zaal said CSP could also help decarbonize Australia’s heavy industries. “Process heat is the thermal energy used in industrial processes. It accounts for over 20 per cent of Australia’s total energy use and emissions. There is now strong industry interest in how to abate thermal emissions.”
Some of the potential uses are quite prosaic. Mars Petcare is evaluating the potential installation of a CST system to provide renewable steam for its pet food factory. It has the potential to displace up to 50% of their methane gas usage. That factory already uses solar panels during the day to generate and store renewable heat. Combining the solar panel system with the proposed CST system, Mars Petcare is targeting net zero operation by the end of 2025.
“Within five years, the return on investment for this kind of renewable heat solution will be under 10 years. By 2035, the payback will be less than four to five years,” Zaal said. “We need policies to encourage industry first movers to establish local supply chains and expertise, thereby accelerating the energy transition. We want Australian industry to optimize their access to our abundant, low cost solar resources. It will drive productivity and improve their competitive standing in global and domestic markets.”
“The CSIRO falling particle technology can provide renewable heat at the same high temperature that coal and gas deliver, and over multiple hours. In addition to being an ideal technology to replace current fossil fuel based power generation assets, it is also an excellent technology to meet higher temperature requirements for mineral processing.”
With significant infrastructure support, falling particle CSP could potentially account for up to 40% of Australia’s electricity generation and process heat requirements in remote areas by 2050. “This would make a significant contribution to Australia’s emissions reduction targets and help us to achieve a more sustainable energy future,” Dominic added.
As Bill McKibben said recently, the sun can provide all the energy humans will ever need for free. All we have to do is figure out how to harness that energy and put it to use. It will take all the cleverness and inventiveness humans are capable of to make the transition away from fossil fuels. CSP will almost certainly be part of the energy mix of the future.
Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new."
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