5 ms·

Those two coal plants are only being run sporadically now, which probably means that they're being run as "peaking" plants, which is a very expensive mode of op

Those two coal plants are only being run sporadically now, which probably means that they're being run as "peaking" plants, which is a very expensive mode of operation. A year or so ago TVA closed our local coal plant after replacing it with a natural gas one, and while they were at it they also built a one megawatt solar plant nearby. Which is all well and good, but that solar plant, even under ideal conditions, can only produce 1/1000th of the power that the natural gas plant can! And just a couple of months ago TVA opened a 53-megawatt solar plant in my area, and they are promising that it will produce enough power to run thousands of homes plus some industrial-scale stuff. I haven't yet been able to find output stats for the two newest installations which I've already mentioned, but I have been monitoring a third local solar installation of basically identical design. And even under "ideal" conditions it's only producing 60% of its promised one megawatt output, and on average only a small fraction of it. (I don't know if it's always been that way or if the situation has deteriorated in the five years it's been in operation.) If TVA keeps building out solar plants which on average only produce a small fraction of their promised output, then before long they're going to be in trouble. This is a general problem with wind and solar; they only produce a fraction (on average) of their "nameplate" (full capacity under ideal conditions) output, yet "nameplate" is what gets quoted in press releases and such. But actual average capacity may be only 25% of that (to use a ballpark number), meaning that you have to divide the quoted capacity by four to get a far more realistic capacity. Meaning that the 1/1000th number that I quoted above is probably actually more like 1/4000th!

SEJeff 7y ago
Thanks for the comment, I think it massively depends on the specific panels and their makeup. You also add a lot of excellent context to the stories I found. There is a ton of cutting edge research going into solar panels and there are many different ways to achieve higher efficiency and/or longer lifespans. My comment wasn't intended to say solar/wind is killing Coal because it isn't. Natural Gas is what is killing coal. I'm from Kentucky originally and the economy is feeling the squeeze from coal just not being really economically viable for some use cases compared to natgas. As the tech improves and mass production makes it cheaper, solar / wind will continue to make more economic sense. The currently "top of the line" most efficient solar panels as of 2019 come from SunPower and only are a paltry 22.2% efficient so there is a lot of room for improvement. Regarding renewables being a fraction of their "nameplate" capacity it really just depends on too many factors to generalize.
- southern_cross 7y ago
  Well, "nameplate" capacity is always the maximum theoretical output under ideal conditions, and how often does that happen? And with solar you have to deal with nighttime, so there goes fully half of it right off the bat! As to that local installation, I drove by it the other day and saw no obvious tracking issues or anything like that. When I took a tour of it about a year after it opened, they said that it had already become obvious that the inverter system was going to be finicky and that it was going to an ongoing challenge to keep that in tip-top shape, given the expense involved. So after five years I could easily envision a situation where the panels and tracking system are still going strong, but the inverter system has degraded to the point where it can only spit out 60% max.

SEJeff 7y ago

Thanks for the comment, I think it massively depends on the specific panels and their makeup. You also add a lot of excellent context to the stories I found. There is a ton of cutting edge research going into solar panels and there are many different ways to achieve higher efficiency and/or longer lifespans. My comment wasn't intended to say solar/wind is killing Coal because it isn't. Natural Gas is what is killing coal. I'm from Kentucky originally and the economy is feeling the squeeze from coal just not being really economically viable for some use cases compared to natgas. As the tech improves and mass production makes it cheaper, solar / wind will continue to make more economic sense. The currently "top of the line" most efficient solar panels as of 2019 come from SunPower and only are a paltry 22.2% efficient so there is a lot of room for improvement. Regarding renewables being a fraction of their "nameplate" capacity it really just depends on too many factors to generalize.

southern_cross 7y ago
Well, "nameplate" capacity is always the maximum theoretical output under ideal conditions, and how often does that happen? And with solar you have to deal with nighttime, so there goes fully half of it right off the bat! As to that local installation, I drove by it the other day and saw no obvious tracking issues or anything like that. When I took a tour of it about a year after it opened, they said that it had already become obvious that the inverter system was going to be finicky and that it was going to an ongoing challenge to keep that in tip-top shape, given the expense involved. So after five years I could easily envision a situation where the panels and tracking system are still going strong, but the inverter system has degraded to the point where it can only spit out 60% max.