by Tina Casey
If you thought concentrating solar power was dead, guess again. A new round of $11 million in Energy Department funding for cutting edge solar R&D includes six CSP projects, and one of them in particular stands out as a game-changer. It deploys the “whispering gallery” effect and 3-D printing to miniaturize CSP plants — those gigantic, lumbering installations that typically occupy hundreds of acres in remote deserts — into a comparatively compact, lightweight configuration suitable for urban and suburban site rooftops.
Concentrating Solar Power, With Trackers
For those of you new to the topic, utility scale CSP plants consist of thousands of heliostats (that’s fancyspeak for special mirrors) or other large solar energy collecting modules. Each module is mounted on a tracking device that rotates throughout the day, keeping its payload in an optimal position to collect solar energy as the sun moves across the sky. All that energy is then transported to a central location.
The US Energy Department has already established a showcase collection of five large scale CSP plants based on conventional trackers, including the Ivanpah plant in California:
Trackers enable the plant to operate more efficiently, but they are heavy, expensive mechanical devices, typically made of concrete and steel. They seem more at home in a steampunk landscape than in the 21st century world of advanced electronics.
If you look closely at that photo above you can see that part of the problem is space. Each silver dot is a heliostat mounted on a tracker. Each of those modules requires a relatively large amount of space between itself and the next one, partly to enable optimal rotation and partly to allow access for repair and maintenance.
So, where to find space for behemoth plants like Ivanpah? In developed countries like the US, finding sites without running afoul of local opposition or environmental concerns (exaggerated or not) is already a struggle. New transmission lines for renewable energy have also become bones of contention (here’s an example relating to wind farms).
Check out the latest interactive solar projects map from SEIA and you can see that very few conventional CSP projects are in the US pipeline:
Conventional CSP is far from dead, though. It still has plenty of room for growth, at least globally. One impressive example is Masdar’s Shams 1, which CleanTechnica got a chance to see first-hand during Sustainability Week in Abu Dhabi earlier this year.
Shams 1 was developed as a showcase for the capability of complex solar technology to operate in the harsh desert environments of the Middle East, and so far it has exceeded expectations.
In addition, the potential for integrating CSP principles into stationary solar modules is already emerging. That’s where the new round of Energy Department funding comes in.
Concentrating Solar Power, Without Trackers
The “whispering gallery” project is a $2.2 million award to Giant Leap Technologies, with additional support from the Lawrence Livermore National Laboratory’s Center for Engineered Materials.
The idea is to deploy the relatively new field of microfluidics, in which fluids are manipulated through tiny channels that are measured in double digits of micrometers.
If you’re familiar with the whispering gallery effect, you can see where this is going. A whispering gallery is an oddity of architecture in which a whisper can be transmitted from one side of a chamber to another, without being audible to anyone in the middle.
A curved ceiling or roof is a key feature of a whispering gallery. Similarly, the Giant Leap/Livermore CSP concept “steers” light along a curved path by deploying internalized, non-mechanical “mirrors:“
The capability is ultimately based on micron-scale capillaries containing a refractive Index Matching Fluid (IMF) distributed within a transparent solid. The physical distribution of the fluid within the capillaries allows light to be steered to a solar receiver, where it can be captured and turned into energy.
The underlying science is electronic beam steering, which harnesses light-matter interaction in order to change the direction of light. CSP is just one of many potential applications for this emerging cross-disciplinary line of research, so stay tuned for more on that topic.
Here’s a sequence from Livermore showing how the internal mirrors form:
The work is still in the prototype phase. In its final iteration, each “Digital Glass™” CSP module would resemble a transparent sheet of glass no thicker than the windshield of a car.
CSP + 3D Printing
Since the whole thing is based on microscale structures, you can also see where the 3D printing comes in. Giant Leap enthuses over the possibilities:
The team will advance new techniques in 3D-printing of opto-microfluidic structures having micron feature sizes with a manufacturing technique that can eventually scale to square meter areas.
This is an increase in fabrication volume of nearly one billion times what was typical a few years ago.
Yep, they said an improvement of nearly one billion times (if you’re taking that with a grain of salt, take it up with Great Leap).
To ice the cake, the folks at Livermore foresee that the new modules could be used in combination with thermal energy storage for baseload renewable energy supply, and in straight-up photovoltaic applications for peak load needs. The peak load angle chips away at the need for natural gas peaker plants, but that’s a whole ‘nother can of worms.
You can get all the details on from Giant Leap’s article from the Optical Society of America journal Optic Express under the heading, “Towards doubling solar harvests using wide-angle, broad-band microfluidic beam steering arrays.” For those of you on the go, here’s the money quote:
The demonstrations clearly showed that a completely transparent medium can dynamically change its internal structure to provide non-mechanical and reconfigurable mirrors that can support broad-band quasi whispering gallery waves and that these waves may be steered to any desired direction by simply changing the distribution of fluids within the device.
Not for nothing, but this kind of inventiveness presents a stark contrast to the lamentations of Silicon Valley A-lister and Facebook board member Peter Thiel, who has been making the rounds in support of the Donald Trump campaign, and painting the same bleak picture of national malaise favored by the candidate himself.
It sure looks like the entire clean tech sector has been flying under Thiel’s radar. If you can think of anything else he’s been missing, drop us a note in the comment thread.