Monday, January 10, 2011

Grid Stability:

First Evidence of Effects of Solar Arrays

This is another post in my occasional digressions into non-nuclear turf, done in the interest of trying to provide a full picture of the potential pluses and minuses of all energy supply technologies.

In this case, I am reporting on solar arrays and the issue of grid stability. Nuclear power proponents have long pointed out that our grids depend on a reliable source of baseload power, and that the irregularity and instability of wind and solar energy could result in serious problems. I have believed that, but to date had not seen reports of specific problems.

In the US, perhaps, we haven't reached that point. However, Germany apparently has reached that point. A report from Germany in recent weeks cites Stephan Kohler, an energy advisor to the German government, as saying that the generous feed-in tariffs have resulted in an "explosion" of new rooftop solar panels and large-scale photovoltaic plants, and that this is seriously stressing Germany's aging power grid. He is actually quoted as saying that "expansion of solar power has to be cut back quickly and drastically."

Now, like most stories, this one may not be quite so simple. Upgrading the grid may help solve the problem. This is not an inexpensive proposition in itself. Further, I have my own concerns that so-called "smart grids" may have their own vulnerabilities, but I don't want to end this post by crossing my arms and saying "told you so." The truth is never as simple as that.

Germany has apparently made the classic mistake of rushing full-tilt into a policy position on solar installations without considering what would happen if it was wildly successful. Of course, Germany isn't unique in its short-sightedness. So far, in my observation, every country keeps making the same mistake again and again. Just think about the effects of increasing ethanol on food crops and food prices.

My message is simply that the German experience is just the latest cautionary tale that we really need to learn to do a better job of anticipating the potential impacts of all technologies.



  1. After reading both your post and the referenced article, the same question--which neither document addresses--keeps coming to mind: in just what way can too much solar power production affect the stability of the electrical grid?

    Are we talking here about too much dependence on potentially unreliable power sources? (A situation such as widespread heavy overcast affecting power production by the solar panels, or widespread "calm" affecting wind production.)

    Are we talking about something else? Like, grid component aging or too high a source to load ratio?

    Some further explanation would be helpful.

  2. Randy's point is well taken that neither the article nor my summary were specific about what the problem was. Perhaps a better reference would have been the New Scientist article below:

    (Looks like this will have to be copied and pasted.)

    The New Scientist article describes the problem in a little more detail--specifically, that the solar input can exceed demand even with all the generators turned off and can trigger blackouts). It also makes clear that this contention is disputed by others. (However, the specific argument, that the solar electricity tends to be generated close to where it is used, may not be the case everywhere.)

    Perhaps most important, the New Scientist article makes it clear, as I said in my posting, that this problem is not an insoluble problem, but that the "fix" requires changes and upgrades to the grid, which comes at a cost.


  3. Thank you, Gail, for taking the time to look into and reply to my questions. Unfortunately, I am no farther along in terms of an adequate explanation of the "problems" and consequences than when we started.

    Here is what I am thinking (nad, mind, I am no professional grid analyst or designer): Grids are designed for transmission of power at high voltages. Variations in that voltage in relation to the actual load on the grid results in current variations (these are controlled in some instances with capacitive load banks), some of which can be quite large (these are the VARs which do no real work but are a consequence of using AC power). These VAR swings can adversely affect the performance of any generators (traditional rotating machinery with windings and interacting fields), in some cases tripping them as a consequence of a sensed potential for overheating or damage to the machinery. In that way, having too much capacity for the demand can affect the stability of the grid.

    But that is a problem we face today were we to put all of the generating capacity we have on the grid at once.

    The trick, as I see it, is coordination and judicious use of automatic capacitive load switching.

    It strikes me that--as is generally the case--there are two sides to this story and we are not getting both of them. Right now we are hearing from those who want to upgrade the grid, who have a vested interest in doing so. They are raising the red flag without telling the other half of the story, the half hinted at but not fully elaborated upon in the New Scientist 'article.'

    I would be interested in any other thoughts on this subject, in part because I want to convert my own home to solar electric and heating (we can do that where I live). But I am also interested because I want to know how stuff works.


    1. to whomever is reading this the problem with the stability issue is that if there are to many solar or wind generators nomatter how small, the grid still needs spinning reserve, which means that if there is 300MWe generated by wind or solar there has to be 300MWe in reserve to take up the slack if one or all of the ways of generating goes down and when they go down then the grid (substation monitoring equipment as well as plants)tries to make the dropped power up and sometimes it cant. then the next plant sees the ripple and it cant make it up the next thing that happens is the main disconnects trip to save the plant from overloading itself to make up the dropped power. that is why there is rolling blackouts or major blackouts if the monitoring equipment cant isolate sections of the grid.

  4. Randy,

    Thanks for your further explanation of your concern. Based on your questions, I realize that we are quickly getting out of my comfort zone here.

    Regarding your specific comments, I would have thought that the head of Germany's energy agency who made these comments was a reasonably balanced source, particularly since Germany is a strong proponent of more solar energy. I would have had more reason to question the solar industry spokesman who discounts the concern about the grid. And my understanding is that managing the output of a few large generators is a much different, and easier, task than managing many small inputs to the grid.

    But there are all impressions I have from general reading. I'm not an expert on the German system, and I'm not an expert on grid management, so I think I've taken this discussion as far as I can. The discussion also taking me farther from the central theme of this blog, which does address non-nuclear issues, but mainly to help broaden the picture--for example, to show that there are no simple solutions. I don't really want this blog to drift too far into other issues.

    Therefore, I suggest the following--I'd like to bring the blog back to the more central and major themes, but I'd like to try to make sure you do get the answers you deserve to your questions. Therefore, Randy, if you are willing to send me your e-mail address, I will post it and ask that anyone who can further answer your questions to respond directly to you.

    I hope this is helpful.