Power Plants

I think folks are reading too much into the hullabaloo about the cold outbreak down south

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I think folks are reading too much into the hullabaloo about the cold outbreak down south.

  • Sometimes it gets very cold in the winter, even in places where you might not think it would get get very cold.
  • Engineered systems, such as power plants and the electric grid work under certain parameters, and when you exceed them, they fail.
  • The extreme electricity demands of resistance heating and air-source heat pumps pre-heaters, overloaded the grid to the point it couldn’t keep up.
  • It doesn’t mean the grid is defective or bad, it’s just that it’s a rare, outlaying case, when parameters were exceeded and an engineered design failed
  • While maybe the it wouldn’t have been an issue in cold weather areas, where the temperature regularly gets that cold, they don’t have the natural gas and fuel oil burners down south to take energy demand off the grid.
  • I think it’s foolish to blame politicians, power plant operators or electric companies for a once in a lifetime disaster that is exceedingly rare, and overwhelmed their infrastructure.

I wonder how much of the spike in demand and electricity shortage down south is due the common air-source heat pumps having to kick on their electric pre-heaters due to extreme cold conditions (at least for the south)

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I wonder how much of the spike in demand and electricity shortage down south is due the common air-source heat pumps having to kick on their electric pre-heaters due to extreme cold conditions (at least for the south). In the south with warmer temperatures being the norm, they rely on heat pumps to pump heat out of buildings in the winter (air conditioning), and pump heat into buildings during the winter. Many large buildings, especially down south, use air conditioners with reversing valves, that allows them to pump heat into buildings, by compressing the heat in outdoors air.

Such systems work well, and are very energy efficient in moderate temperatures. You can typically compress enough heat out of 35 or 40 degree air to keep a building a comfortable 70 or 75 degrees. But the problem is when the air temperature drops below 35 degrees — there is simply not enough heat in air for compressor to work. Such air-source heat pumps then contain electrical resistance pre-heaters, similar to electric space heaters that a lot of people have. The pre-heaters are activated to heat the air when it’s cold to compress it out of outdoors air. While resistance heaters release all of the heat in electricity, power plants are lossy and 55-70% of all heat in fuel is discarded and not turned into energy. So when they fire up the electric heat, it’s quite lossy.

Why is electric heat so expensive?

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Why is electric heat so expensive?

On average in 2019, it took an average of …
10,551 BTU or 3.1 kW of coal or 7,732 BTU or 2.3 kW of natural gas
To produce 1 kilowatt of electricity, which is equal to 3,412 BTU.
 
How much does your 120 volt plug-in electric heater in your house use when it’s on? It doesn’t really matter whether it’s a $12 Walmart heater fan, or a $300 radiant heater in a fancy wood cabinet. All are same energy efficiency – when you apply resistance to electricity, 100% becomes heat, including the heat produced by the fan coils or indicator lights.
 
All 120-volt heaters are 1.5 kW or 5,118 BTU, because 120-volt wall outlets can only supply 12.5 amp constantly. In theory, you could make a space heater smaller then 1,500 watts but nobody does because electric coils are cheap to manufacture, and when you are warm, the thermostat just shuts off.
 
So every hour a heater heater is operating, it’s 1.5 kWh.

Oddly Fascinating

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I find it oddly fascinating that in the split phase electricity system used in the United States, the only power that flows on the neutral wire back to the center tap of the pole transformer is the difference in amperage between the phases.
So if you have …
20 amp draw on the Phase A
30 amp draw on Phase B
You’ll have 10 amp flowing on the neutral, which is also referenced to the ground
If you disconnect the neutral from the center tap of the transformer, the 20 amp load will work okay but the 30 amp circuit will see its voltage cut by 1/3rd.

Learn Why Ohm’s Law Is Not a Law

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Learn Why Ohm’s Law Is Not a Law

All diodes violate ohms law as they are inherently non linear loads - which is why you can't use ohm's law to understand solar power or LEDs as they are diodes which conduct electricity in a non linear fashion.

If solar panels were linear their output would would be the same regardless of load but the silicon junctions are more efficient at certain current levels. That's why people use buck and boost converters to maximize their efficiency - and why most larger solar systems use MPPT controllers. 

Likewise, if you limit the current and under drive LEDs they can be much more energy efficient and last longer. For example, two LEDs each driven at 10 mA will produce much more light than one LED driven at 20 mA, even though ohms law says that's impossible. This important - if you pack more LEDs in a light bulb and run them at lower current you can boost efficiency and lifespan at a greater cost of building the bulb.