Sunday, November 20, 2016

Waste from Solar Panels:

End-of-Life Challenges

I have commented a number of times on the fact that every source of electricity has pros and cons.  For example, both fossil fuels and nuclear power provide reliable baseload electricity, but fossil fuels create air pollution and emit greenhouse gases, and nuclear power generates long-lived radioactive waste; the "fuel" for solar and wind power is free, but solar and wind power have intermittent availability and require vast quantities of materials. 

Recently, I've become aware of a new issue related to solar panels.  At least, it's new to me.  Solar panels create large volumes of waste when they reach the end of their working lives.  Since solar panels have no moving parts, I had never thought of them as having a limited life span. 

It turns out that, unlike many other electricity-producing technologies, which can operate for decades, solar cells slowly lose efficiency, and therefore, are expected to need to be replaced after only 20 or 30 years of operation.  This is much less than the lifespan of fossil plants or nuclear reactors.  And because solar energy is diffuse and large numbers of solar cells are needed, the increasing use of solar energy will result in huge volumes of waste in the coming decades.

The cited study comes from Japan, where they are trying to increase the use of renewable energy dramatically following the closure of a large fraction of their electricity supply after the Fukushima accident.  Their estimate is that, a couple of decades from now, solar energy will result in around 700,000 to 800,000 tons of waste annually.  Dealing with that would require getting rid of 110,000 panels per day.

Efforts are being made to figure out how to handle this waste, but all options have complications.  Panels may be recycled for less intensive uses, but panels degrade at different rates and would need to be tested before determining if they have enough remaining capacity to justify transporting them for reuse, perhaps to other countries.  And ultimately, of course, they would decay further and still need to be recycled or disposed of.   Recycling the materials from the panels is also complicated.  Panels are composed of several layers which would need to be separated, and existing processes for doing so are fairly costly. 

Work is underway to improve all these processes, and no doubt the coming years will see improvements in the technology for handling "spent solar panels."  But even with improvements, it is clear that the issue of dealing with old solar panels will be a significant part of the life cycle for solar panels, and the cost, energy use, and necessary infrastructure to move and process hundreds of thousands of solar panels will need to be considered. 



Innovative Nuclear Energy Systems:

A Fascinating Symposium

I recently had the pleasure of participating in INES-5 in Tokyo, Japan--the fifth Innovative Nuclear Energy Systems symposium held since 2004--and wanted to share my observations from that meeting. 

I participated as an invited speaker in a special memorial session in honor of MIT Professor Mujid Kazimi, who died last year.  Although that session started the meeting on a somber note, the rest of the meeting was more upbeat, as it highlighted innovative developments and initiatives in all areas of nuclear technology.  I'm sure Mujid would have been pleased to hear of some of this work.

The meeting was a special delight for me, as it was held on the campus of Tokyo Institute of Technology, where I had previously spent a year as a visiting professor in the Research Laboratory for Nuclear Reactors (now the Laboratory for Advanced Nuclear Energy).  It was fun to return to the campus, to pass some familiar spots and reminisce, and to see all the new buildings and other changes.  And to reconnect with several of the professors I had worked with while I was there.

The meeting was a trip down memory lane in another respect as well.  I was a participant (along with Prof. Kazimi) in the first INES conference in 2004.  I participated again in the second INES conference in 2006.  

The meeting had speakers and participants from around the world.  The vast majority were from Asia, particularly Japan, of course, but some were also from at least a half dozen other countries in Asia. Other countries represented ranged from countries with operating nuclear power plants, like China, Korea, and India, to countries like Vietnam, Indonesia and Mongolia, that currently have nuclear research programs, and may have possible future ambitions for nuclear power plants.  In addition, there were also participants from the U.S. and from several European countries.  What was particularly impressive was that the symposium included a lot of students and highlighted some of the interesting work they are doing. 

The special session on Prof. Kazimi covered some of his work, and also highlighted his character.  The session was introduced by Prof. Yukitaka Kato, one of the chairs of the symposium, and the speakers included Prof. Emeritus Hiroshi Sekimoto, a former professor from TITech, Professor Ron Ballinger from MIT, and myself.  Sekimoto, who had worked with Kazimi, recognized the long-standing ties Kazimi had with TITech, and recounted some of his personal memories of Kazimi.  Ballinger described Kazimi's research activities, and also commented on his outstanding relationships with students and MIT faculty.  I tried to put some of his work in the context of what is happening today in the U.S. in the advanced reactor area.  I had known Mujid for many years (the photo below shows us both participating in a summer course at MIT in 2000), but had not worked with him as much as the other speakers, so felt particularly honored to be included in the session.

The technical program featured several sessions on innovative nuclear reactor technologies, and also sessions on related technical areas, including advanced nuclear materials, measurement and detection, radioactive waste treatment technology, innovative separation technology, heat transfer and hydraulics in innovative nuclear systems, innovative energy utilization, safety and security in nuclear systems, nuclear fundamentals (cross section measurements, spallation reactions, etc.), and accelerators and plasmas.  There was also a large poster session featuring a lot of the students' work.

 As noted, this event was the 5th in a series of symposia that have been put on over a period of about a dozen years, starting in 2004.  I look forward to the 6th INES symposium, which is now being planned for 2019, and will no doubt continue the tradition of highlighting innovative work in a broad spectrum of nuclear areas.