Author Topic: Episode #701  (Read 1399 times)

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Offline PatrickG

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Episode #701
« Reply #15 on: December 18, 2018, 11:06:12 AM »
There is one respect in which higher voltage is better: lower voltage requires heavier wiring for the same amount of wattage because it necessitates higher current. But this is irrelevant to the discussion at hand where we’re talking about powering lights.

True. Picking the right voltage is a complex trade-off, and highly dependent on the situation. And sometimes a bad choice sticks: here in the USA we use 120V AC power, while most of the rest of the world uses 240V. Sticking to 120V costs a lot of extra copper, breakers, house fires and losses, while saving only a few electrocution casualties.

Conversely, in electronic chip design we want an as low as possible supply voltage. That is because switching power goes up with the square of the voltage. Most processor chips use less than 1 Volt, which causes huge currents and many design challenges related to that.

Electric Vehicles batteries are typically at 400V. Higher voltages have diminishing return because it would require more expensive isolation and much different power electronics. On the other hand, ultra fast charging (459kW) needs a higher voltage to avoid hot charging cables. So it is all a trade-off.
« Last Edit: December 18, 2018, 11:08:20 AM by PatrickG »

Offline CarbShark

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Re: Episode #701
« Reply #16 on: December 18, 2018, 01:55:05 PM »
I call bogus on that SoF item.
I’ll have to Listen again but I believe the point was that it would produce enough wattage (voltage and current) for only a brief flash.

Steve is great in producing Science-or-Fiction items. This item, however, was a skeptical fail, both in the way it was formulated as well as the quality of the underlying work. This is verbatim how it was formulated:

Researchers have found a way to harvest electricity directly from plants, so that a single leaf can generate enough voltage to power 100 LED lights.

To any casual reader this suggests that a potential solution to our energy problem lies in harvesting electricity from plant leaves. After all, it “powers 100 LEDs” from a single leaf. 100 LEDs is more convincing than 1 LED, right?

Yes, and I also understand that was a Science or Fiction question where the intent is to trip up any of the rogues who only listen casually.

If his language was technically correct, but possibly misleading, that's how the game is played.

Blame the game not the player


There is a widespread public misperception that a higher voltage is somehow more powerful. Try shopping for a cordless drill at Home Depot. All ads prominently show volts, but never power or durability. You are made to believe that 18 Volts is better than 12V.

18 volts is better than 12volts for cordless tools.

It would be truly relevant to know whether the energy harvested from leaves is enough for a tiny internet-of-things device. It would be interesting to know whether this connection is reliable. And it would be interesting how this compares to other means of harvesting energy from wind.  None of those questions are answered by this work.

The Science or Fiction game is not designed to answer those questions, but it is designed, in part, to encourage the listener to ask those kinds of questions.

It's not work, it's play
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