A reader who has a fair amount of experience with wind energy writes in to tell us he's concerned about the City of Portland's pipe dream of building and operating a wind farm:
It's pretty obvious that wind power has become the darling of the political establishment, which seems to view it as the answer to all, or most, of our energy and climate change challenges. It's hardly that, in my opinion, and the following are a few of the principal reasons why I think that is so, and why the idea of the city of Portland actually financing the construction of a wind resource is so scary.My, my. How un-"progressive" of this reader.
1) For example, a 50 megawatt (MW) wind resource is not really a 50 MW wind resource. In fact, in the Pacific Northwest, its a 15 average megawatt (aMW) resource. 50 MW is the capacity of the resource, i.e., the maximum amount of energy the individual turbines making up the project, in aggregate, could generate at their combined maximum output during any given instant. 15 aMW is an expression of how much actual energy is generated on an annual basis. Of course, the wind is not always blowing. In the Pacific Northwest, experience with wind turbines, beginning in about the late 1980s, shows that over the course of a year a wind power resource will produce an amount of actual energy that is equal to between 28 and 32 percent of it total rated capacity: so 50MW x 30% = 15 aMW. So when you read that Portland is going to build and use the output a 50 MW wind power resource to serve its electricity load, you need to understand its only 15 aMW -- a lot less than advertised. Do you think Sam Adams knows that?
2) Idle wind turbines can be a big problem. An intermittent resource such as wind needs to be "firmed up" to be useful. In other words, it needs to be backed up by additional energy resources that can be turned on and off (more or less instantaneously) to fill in the gaps when the wind turbines are not producing energy. This gets complicated, and has to do with the way electric energy is "scheduled" into the wholesale bulk transmission system, but long story short, in order to balance electric power loads with electric power resources, every energy resource is scheduled ahead of time (usually an hour ahead of actual delivery onto the transmission system). Obviously, that is much easier to do if you are running a coal resource than if you are running a wind power resource. So, if a wind resource schedules 25 MW onto the transmission grid next hour, but only generates 15 MW because the wind speed slowed, the other 10 MW has to come from somewhere else. The system must be kept in balance, every second of every day, both to make sure loads are served, and to keep the transmission system itself in balance. The PNW is blessed with a large hydroelectric system that, in general (depending on the time of year) can be ramped up and down quickly. This abundance of instantaneous generating capacity is useful to integrating intermittent energy resources such as wind. The problem is the hydro system, over the last 20 years or so, has lost much of its operating flexibility due to the competing demands for fish mitigation, leaving less operating flexibility left over to integrate or "firm up" wind resources. As more wind resources are built, while the hydro systems flexibility continues to wane, this creates a big problem. So what happens? Other resources, principally gas turbines, must be built to firm up wind. The Germans, who I believe have more wind generating capacity than just about any country in the word, have had to install massive amounts of natural gas fired generation to firm up their wind. So wind looks a bit less clean all of a sudden. I doubt Sam Adams has an inkling of this.
3) A strong case can be made that, in some circumstances, wind is dirtier than natural gas. This relates to point #2. Basically there are two kinds of natural gas fired energy resources: combined cycle and simple cycle. The latter is the type usually built as a firming resource to back up wind resources. Simple cycle is dirtier than a combined cycle resource. An argument can be made that a wind resource combined with a simple cycle gas turbine, designed, for example, to produce 100 aMW, will under some scenarios produce more greenhouse gas over the course of a year than producing the same 100 aMW with a combined cycle gas turbine. This an irony I doubt many politicians know about, including Sam Adams.
4) The wholesale power business in impossibly complex and highly risky. So this point is not so much about wind power as it is about whether it's such a good idea for the city to get into this game. Its not clear to me what the proposal is exactly, but it's apparently much more than simply signing a contract to buy output. I should wait to see what they actually propose to do, and assuming its covered in your blog, I can chime in with my two cents worth then. Suffice it to say for now that even in the best of circumstances, building a large resource is fraught with operating and market price risks. Based on what I have seen, I doubt the current members of the Portland City Council are equipped to readily grasp, let alone evaluate or understand how to mitigate, those risks.