Hey Little Girl, Cathodic Protection
Those who grew up with the rock/pop of the 1960s will recognize that the title here is a take-off on the song: “(Hey Little Girl) Psychotic Reaction.”
Now that we have that bad pun out of the way, let me explain that protecting the metal poles that are driven into the earth to support ground-mounted PV systems is not a joke at all; in the wrong soil conditions, they can corrode to the point of complete destruction in as few as five years. That’s where the people from Corrpro come in. Imagine that you have a utility-scale PV array that costs $100 million to install; now imagine that you can extend its life another 15 years with an investment of under $2 million.
How? Use a tiny fraction of the electrical power generated by the system, and cause it to flow though a circuit created by installing a set of custom-made anodes (can be magnesium, zinc, aluminum, etc. depending on the make-up of the soil) a few feet away from each of your poles, which now act as so many cathodes. The net effect: all the corrosion occurs at the anode, rather than at your precious cathodes.
As 2GreenEnergy intern Fabio Porcu and I learned as we walked the halls of the Solar Power International show yesterday, there are hundreds of novel approaches to solving the many problems associated with harvesting the sun’s energy, 365 days a year for decades on end. However, many of them are unexciting, and some downright silly. Corrpro, by contrast, is brilliant, and their customers’ ROI stats speak for themselves.
Same effect as in boats and water heaters.
Actually corrosion is a huge issue, and a massive cost, throughout the entire energy industry. For example, the oil company that is responsible for the Alaska Oil Pipeline from Prudhoe Bay to the Port of Valdez, several years ago turned off the corrosion protection system (and apparently didn’t bother to tell the Department of Transportation), and now that pipeline has corroded in some areas to the point of potential leaking which could create a massive pollution nightmare. Wind towers must be constantly monitored for corrosion as well.
Corrosion is not the only maintenance cost for renewable energy systems. The biggest problem with the massive installation of “end-user” PV systems is that the owners generally are not educated, nor prepared, to properly maintain these systems. This is creating a massive “ticking time bomb” as our energy delivery grid becomes more and more dependent on distributed energy. This is no different than the individual wind turbines — which also require an on-going maintenance program. PV is only economically viable, when installed at the end-user location to offset the cost of energy, which includes all of the generation, as well as transmission and distribution costs of energy. It is not, in most cases economically viable for large utility scale installations, where the competing coal or natural gas generation cost is near 4 cents/kW-hr.
Until large utility scale solar is low enough cost to be economically viable, so large organizations with the financial capability and technical expertise to do the proper maintenance, utility scale wind energy is the only truly viable renewable energy source for us to be installing in the U.S.
Distributed energy is great, but individual owners are just not going to make the necessary investment to properly maintain them. The organizations advertising and selling them, are doing the energy industry a great disservice by not telling the potential buyers that there is an inherent maintenance cost that must be factored into any energy generating installation. Banks and other lending institutions, and investors, always make large utility scale wind energy systems include an escrow account to pay the cost of maintenance, in the economic Cost of Energy (COE) analysis BEFORE the wind farm is built. Individual PV installation owners should be assisted to do the same thing.
Thanks, Jerry. Please see: http://2greenenergy.com/2015/09/20/solar-pv-infrastructure-corrosion/.
Cathodic protection has been around for many decades; it is not new.
In earlier times, defective telephone systems, which of course use DC, resulted in cathodic unprotection and serious problems with corrosion. If the polarity is not right, what is supposed to be cathodic protection is cathodic unprotection and accelerates corrosion.
Regarding home PV systems, except in very remote areas, I am not aware that they have made severing the connection with the grid possible. Merely getting a modest amount of our power from renewable sources in insufficient. As global demand for power increases, it will be necessary to get about 90% of our power from non-CO2 emitting sources, including power for heating, cooling, lighting, cooking, sea water desalination, transportation, manufacturing, etc.
Yes, in some places, wind power dovetails nicely with solar, but wind power can be almost nonexistent for weeks at a time.
Craig – when I saw your link, I was hoping it lead to a detailed “how to” article. I appreciate the heads up about the issue (although, since my panels are on my roof, this is not a problem for me… I think) but this has started me wondering what other issues there are.
It seems to me that your site is the perfect spot to hold descriptions and possible solutions for problems most of us don’t know about until we’re hit with it!
“Cathodic protection” (the name amuses me, for some reason…) never occurred to me – I’m still not sure I understand it – what about “grounding” and cathodic protection – is there an interaction? Can the same metal poles do both? Do I solve the issue by having my grounding rod made from the right metal?
I realize I sound like a complete novice – but my training is in music! Not electrician-ism. If I’m trying to get something done, part of it is knowing the right questions to ask.
And this is one place your site can be really helpful.
Thanks.
Thanks. As far as I understand the subject, the issue is that a piece of metal stuck in the ground is going to undergo a chemical reaction (depending on the type of metal and soil) in which it corrodes. The solution described above, i.e., forming a circuit in which a small amount of current flows between the metal PV structure (now a cathode) and a new piece of metal (an anode), moves the degradation to the anode, thus protecting the cathode.
Yes, this website could act as a repository for ideas like these; let me think about that.
This excels.
Ha! Thanks.
In the case of guard posts around ground mounted PV’s , they could be recycled plastic posts and thereby avoid the problem.