Corrosion is a Challenge for Renewable Energy Systems, But Solutions Exist
February 28, 2013
The firms that are designing the solar panels are saying the product has a life of 20 to 30 years. But it’s a new industry, so the power companies that are buying these are asking how the manufacturer can guarantee the equipment will last 20 to 30 years in these harsh environments? We don’t have a proven 30-year history of installing these in the desert or on the coast.
So our company goes out and does a physical environmental study, including the soil that the posts are going into. That’s what they are concerned about – not the thin film, but the supporting structures that are going into the ground and holding the panels up. They are worried these posts will degrade and fall over. We look at what kind of steel are they using, how thick it is, what kind of coatings are already going on it, and look into corrosion control measures that will ensure the product has the lifespan promised.
With wind, you have onshore and offshore. Onshore, you are putting them in the windiest places you can find: tops of mountain ranges, the plains, etc. We are assessing these big steel structures, and looking at the metal, the coatings, etc. Offshore wind farms are in an even more corrosive environment because of the salt water. Here, we are looking into more heavy-duty designs.
The other thing we look at is if there are dissimilar metals. So if you have steel in contact with bronze or copper couplings, this will cause a corrosion cell. We will need to design insulators so that the metals will not be touching.
Then there is a larger corrosion control method called cathodic protection. That is a design where we purposely put in a material that will corrode instead of the asset. So we will put in a less noble metal, typically magnesium or zinc, and that will corrode instead of the asset. You can’t always stop corrosion, it’s a natural process. But you can let something else corrode first. It can be designed for most applications, but what comes into play is cost and design life. We can design it to last as long as the client wants, it all depends on how much magnesium or zinc they want to use.Q. Give me an example of the kind of coating you would put in an offshore wind farm versus an Arizona solar farm. NIKOLOKAKOS: In a desert environment the hot-dip galvanizing (zinc coating) has been used for almost all the installations we have been involved in. In a marine environment, it will depend on the installation details and how far they will be from the sea water. Near the water, the zinc coatings will not be as good. An evaluation must be made based on the installation details and materials to determine what would be the best coating for the solar support structures.
For the underground portion of the structures a cathodic protection system may also be required if the soil is very corrosive (ground water may be brackish/sea water). This also applies for the wind structures; I am not sure what they are normally using for the wind structures in a desert or in a non-marine atmosphere. In a marine atmosphere, however, an epoxy or other similar type of coating may be used. Depending on the type of foundation, cathodic protection may also be required for the below-grade portion.
Bottom line: If recommendations are to be provided, we need to evaluate the corrosiveness of the environment, materials of construction, installation details and also consider the design life of the structure as well as the cost of maintenance.Q. Are these pre- or post-installation solutions? GRANT: We have both. But it comes down to whether the post is already corroded. We can’t put metal back on the pipe. However much it is corroded it will stay that way. As long as it’s structurally sound, we can retrofit cathodic protection on it so no more metal corrodes. We prefer to do it pre-installation. Q. What kind of damage and challenges does corrosion cause for energy generation systems themselves? GRANT: There have been some companies that have asked us to do some research, but we have not really engaged too much in this. Companies like First Solar and some of the Chinese manufacturers are already looking into it. But we are more focused on the ferrous metals that are supporting these structures. Q. Solar and wind power have been around a long time. Why hasn't anyone thought of this before? GRANT: That’s a good question that I’ve thought about a lot. It’s not like we started marketing into the renewable energy market. We started getting proactive calls from companies saying that they are installing something in the California desert or along the coast of Italy and that they are worried about this and that, and asked us to provide guidance on how their design life can be achieved. Q. How do these solutions affect the overall carbon footprint and environmental impact of renewable energy equipment? GRANT: Our solutions are not going to be impactful to that footprint in any way that I can think of. Our whole mission is to keep those assets that are producing renewable energies from falling over.