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I don't think so. TWh (Terawatt-hours) are not units of power, but a convenient conversion from Joules (J), which measure work, aka energy. When you say "steel
by cormacrelf 5y ago
I don't think so. TWh (Terawatt-hours) are not units of power, but a convenient conversion from Joules (J), which measure work, aka energy. When you say "steel uses so-and-so TWH" you are omitting over how long a period it does that; if it's an annual figure or something, then that makes sense, but you can't omit that. If my house consumes 1MWh (Megawatt-hour) of energy in one year, then it's a normal house. If it draws the same amount in an hour, then my house is not a house but a mid-sized city. You shouldn't expect people to guess what time period you are talking about. You should see the error in describing "all the hydro power" in TWh, because it simply is not a measurement of power.
Usually when you're talking about electricity generation, you are trying to weigh up demand and supply. These quantities are each most naturally represented as rates of energy use, because those rates fluctuate intra-day. We mostly care about the highest point of the graph of demand in a region over a 24-hour period, because you can't build a wind farm in an hour to meet extra demand. Using Watts avoids ever having to talk about the period in question. One Watt is one Joule of energy per second. The OP clarified in an edit that they mean Watts.
When you're talking about batteries, yes, you do need absolute quantities. Currently they're only good for smoothing out small peaks and troughs in supply, so the absolute amount of energy is proportional to how long it can cover for a wind farm when the wind farm slows down. Note that when the article talks about production capacity being "60GWh per year", they don't mean watts; the batteries are presumably shipped without much energy in them. They mean "produce enough batteries that the amount of capacity in total is 60GWh". It says nothing about the energy it will take to build them, which you would measure in Watts so that you can plug it into the instantaneous supply-demand calculation. 60GWh only tells you how much total supply smoothing capacity it will be able to provide to customers.
When you are talking about carbon emissions, you aren't as interested in peak demand, and you might instead think about absolute quantities in a year, and proportions of that that have been generated by renewable sources.
- bjoli 5y agoI omitted "per year". In the energy debate i sweden, the "per year" art has often been sloppily implicit. I will make sure to keep it in. The numbers given by the parent are consistent with the twh/yr number seen in swedish media
- cormacrelf 5y agoTWh/year is definitely convenient if the central purpose of the discussion is to figure out the CO2e that will be emitted to produce it, or how to reduce the total energy use. This is good, in contrast to the coal/oil lobby's laser-like focus on peak demand, because their argument has long centered on the unpredictability of renewables. If you can do what the "smart grid" folks are trying to do, and spread out energy demand over the day, then the peak is not as big of a problem. Maybe Sweden's peaks are just naturally not so dramatic. In Australia everyone worries about peak demand because the central interaction most people have with the grid (aside from their electricity bill) is a blackout during a heatwave due to heavy air conditioner use. This is incredibly dumb, because the argument completely fails to hold up against solar, for which a heatwave is a blessing.
- tmikaeld 5y agoIt's blackouts that Sweden is dangerously close to, because the majority of power is consumed in the south but it's produced in the north. There's not only a production issue, but also a transport issue.
- cormacrelf 5y agoYeah. Everyone's got the same problems; practically nobody has invested enough in transmission. (I'm hoping someone sees this and corrects me, I'd love to see a good example.) Good luck up there.
- magicalhippo 5y agoWe have a similar issue in Norway. There's currently a huge difference in prices between north and south of Norway due to limited transport capability. It's been over 10x at times this winter[1], though on average "just" 3-4x. In addition the water reserves for our hydro, which is like over 90% of our power generation, is quite low... [1]: https://www.nordpoolgroup.com/Market-data1/Dayahead/Area-Prices/NO/Hourly/?view=table https://www.nordpoolgroup.com/Market-data1/Dayahead/Area-Pri... (December 21, Oslo vs Tromsø)
- 5y ago
- kragen 5y agoThis is all correct, and I really appreciate you taking the time to say it. Except that a megawatt is more like a small town than a mid-sized city. A mid-sized city is closer to a gigawatt.
- cormacrelf 5y agoThanks. And you’re right, I think I was spitballing for one minute.