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Comment by capty99 | Hacker News Reader

could someone explain to me how that $5 spend is lying to me. i know elec is cheap, but that cheap?

They’re using wholesale prices. The entire flight was 27 minutes, peaked at a megawatt of power, and a wholesale megawatt-hour is $40-50 these days.

$5 does not make sense, and there must be some qualifer on that we're missing.

Napkin math:

(27 minute flight) * (25000 lbm TOGW) * (Earth gravity) / (~10 average L/D) * (160 KTAS average) / (70% propulsive efficiency) / (97% coulombic efficiency) * ($50/MWh) = $30

(Add residual kinetic energy upon landing too)

Side note: Heart also has a weight issue here they'll need to overcome if they want to certify under FAR Part 23 (as their 19-pax spec implies); TOGW limit for that is 19,000 lbm.

It's a 30-pax (32-seat), Part 25.

I tried to run a napkin calculation, and that 5$ figure must be quoted per seat (30 seats). And a 'first flight' might be very very short, like 15 minutes of flying or less.

During certain hours of the day in California, electricity is essentially free due to solar overproduction, which sometimes causes negative wholesale prices.

I've never quite understood negative electric/gas/oil prices.

Are you literally paid for agreeing to receive the energy?

Yes. Counterintuitive, but it make sense when you take all the factors into account (such that completely shutting down and then later restarting turbines may cost a generator more than paying someone to take power off their hands).

Yup. What people have to realize is that power generation has inertia and can be painful to start/stop. But also, the power output always has to match the power demand. If you don't, you get either brown outs or over voltages.

When you add sources like solar onto the grid, you end up with times of the day where high solar production pushes base load power generators to need to slow down or shutdown.

Easiest to understand with oil. During Covid the price of oil went negative. So you’d be paid if you bought that oil.

Sounds like a great deal right? But now you’re on the hook for receiving and storing that oil. That costs money, it’s not free. That’s why the price went negative - the seller was trying to offload and there were no takers at $0.

Yep. Last August the total cost to charge my car for the month was -10SEK of about -$1.05 US, as my energy company was trying to put load into its batteries at the times when the grid most needed it.

>my energy company was trying to put load into its batteries at the times when the grid most needed it.

I'm not sure I understood this sentence?

Grid had too much production and needed somewhere to put it, so they paid the GP to put the energy into GP's car.

On an electric grid, Supply and Demand must meet. When demand is low, you either reduce supply or increase demand and sometimes it's easier to increase demand.

Also, if you're supplying electricity, you may have reason to supply it even when the wholesale cost is negative. If you have production incentives not included in the wholesale price, you can be profitable at negative wholesale prices. (Things like green incentives, or base load incentives, or long term supply price guarantees)

If significantly reducing your output takes time or causes operational difficulties, it may be sensible to deliver at negative prices as you taper off. If you have a fuel shipment inbound and nowhere to store it, the negative wholesale price may be less expensive than cost to deal with the storage logistics.

Yes, if you’re a battery in the system. Basically discourages generation because there’s too much supply. But this generally doesn’t trickle to consumers afaik.

Gas and oil need storage, if there’s too much supply and no storage, the price goes negative. This happened during COVID.

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