Environment & Energy

frequency increases or slows down. If the problem is generation < load, the system frequency slows down, and the governors on the online generators automatically raise generation, which pushes the frequency back up.

(And the opposite in the case of generation > load -- system frequency speeds up and the governors back down the generators.)

Back to the first case of generation < load -- If these actions are insufficient, i.e. all generators on the system have had their generation raised to maximum, and yet the frequency continues to drop and dips below a certain point, than automatic load-shedding occurs. If that still doesn't do the job and the frequency dips below a certain level, the generators trip to protect themselves from damage and a big chunk of the regional power system probably goes down.

The opposite -- generation in excess of the load -- works the same way except everything in the opposite direction.

As for all the talk of storing energy and using it at a better time -- yup, but still, the total generation (including storage device outputs) must still meet the total system load (including storage device usage for recharging).

The huge energy losses in the energy flow diagrams are what caraher said.

Thermal power plants (nuclear and fossil fuel) are only about 30 to 60% efficient (the 60% figure is about the maximum obtained by combined cycle). Other than combined cycle, the range is more like 30 to 40% efficient. That's because converting heat to mechanical motion (to turn the turbine which is attached to the generator), as all thermal power plants do, is an inherently inefficient process that is limited by the temperature difference between hottest and coldest temperatures available to it.

https://en.wikipedia.org/wiki/Heat_engine

I worked as an electrical engineer in the planning and system operations departments of an electrical utility (Northern States Power Co, now part of Xcel) for about 15 years, in the late 1970s - 1992. This was before wind and solar were a factor.

As for excess wind generation -- when all of the power system's online generators are backed down to their minimum operating points and still the total system generation is on course to exceed the load -- the wind turbines can be and are shut down if the economics are favorable to that (shutting down and restarting a thermal power plant incurs energy and additional maintenance costs, so it will often be cheaper to shut down the wind turbines than to shut down a thermal power plant that has to be brought back on line in a few or several hours, or in some cases an entire weekend).

I presume the wind turbines also shut down automatically in case of excessive system frequency. I know they do if the wind speed is too great.

I don't think that shutting down wind or solar is represented as a loss in the energy flow diagram. It's just electricity that could be generated but wasn't.

The other losses are at the customer end (the right side of the diagram), e.g. a typical home furnace efficiency is 75%. The other 25% goes up the chimney. (New furnaces must by law be at least 78% efficient, Google sez).

Well, as the fine print wording below the diagram says: