4 ms·
Agreed, stunning it is that so common and reasonably safe a thing as a self-serve gas pump is a 22 MW chemical energy delivery system! Some reflections: * Per
by EEGuy 13y ago
Agreed, stunning it is that so common and reasonably safe a thing as a self-serve gas pump is a 22 MW chemical energy delivery system!
Some reflections:
* Perhaps an EV might be 10x as efficient with its input energy as a gasoline powered car. Perhaps 220 KW would do.
* Perhaps a robotically mobile, rather than a counterweighted, manually lifted and connected cable is in order. The present day robotic car wash design where the car stays still while the motile, rotating washing machinery moves around it comes to mind.
* Electrical connectors give me more trouble than wires and cables. A replaceable, quick-disconnect connector capable of 20KA seems more of a design challenge than the cables that would go with it.
* High voltage insulation and wiring is "easier" than high current conductance (low resistance) wiring, for example: Common engineering practice with 30-volt solar panels is to wire them in series so that the total string voltage is 300 to 600 VDC at 8 Amps, rather than in parallel so that the current would be 80 to 160 Amps at 30 Volts. Air is a lousy and unsafe insulator, but there are good liquid insulators which could easily, temporarily fill a two-pole, ground-surround high-voltage connector (displacing the air) before it's allowed to be electrically energized and ramped up to a high voltage. Precise ground fault current detection could make it safe from fault currents (i.e. shocks & shorts) in the milliamp range even as the cable carries hundreds or thousands of Amps. But any HV supply requires up-conversion at the station and down-conversion in the EV; whilst these can be 95% efficient, the effect of each conversion inefficiency is multiplicative, and they add weight.
* Then there's the charging station itself. If it has eight charging stations at, say 250 KW each, that's 2 MW draw from the utility (or an underground group of batteries recharged at a lower rate from utility power?) when all stations are charging cars. Not trivial; just the 500 KVA (call it 500 KW for discussion purposes) utility distribution transformer outside building where I work is the size of four refrigerators, not including its switchgear, all of which is enclosed by a 20 foot tall fence surrounding about 200 sq feet. Multiply that by four in volume to get 2 MW supply required from the utility.