For starters, code could say at least 30% of the roof surface has to be South-facing. Then indeed, they could require that South facing part of the roof doesn't have any of these features :

For starters, code could say at least 30% of the roof surface has to be South-facing. Then indeed, they could require that South facing part of the roof doesn't have any of these features :
40% Round trip efficiency on a li-ion battery seems high?
That ~7% is friction losses in the transmission. There are multiple gears that the engine power must go through before it hits the wheels. This is the same reason that mid drive efficiency is significantly lower than what we see in hub motors ( until you go and climb a 15% grade and your hub motor falls out of it's efficiency curve in a dramatic way - in that case, the mid drive obviously wins the efficiency challenge ).cricketo wrote: ↑Feb 05 2019 10:14pmWhat does this 7% represent ? Increased friction due to gear box ? Oil pumps ? Sub-optimal engine performance due to variance in RPM ? Friction losses in the transmission ? Any difference between 2wd, 4wd, FWD, RWD ?
Also don't tell these guys
https://en.wikipedia.org/wiki/Workhorse_SureFly
Understood. So for comparing against an ICE vehicle we still need to account for drop in engine efficiency due to variance in RPMs. That may be lower for a hybrid like you're describing, but even there engine won't run at steady RPMs at its peak performance.
That's not just lithium ion charge/discharge efficiency. It's also generator efficiency, power conversion efficiency, controller efficiency and motor efficiency. Let's ballpark those numbers:
I would note that since most hybrids don't use standard transmissions, the engine RPM is largely uncoupled from the wheel RPM. So you can run at a more efficient speed, rather than a ratio to vehicle speed.
It depends what you are quoting and how. For example, a lithium ion battery might well have a 99% coulombic efficiency (amp-hours in to amp-hours out) but a 90% power efficiency (watts in to watts out) since you have to charge at a higher voltage than you discharge. If you are charging at 4 volts and discharging at 3.6 volts, that's 90% right there. (Lower charge rates result in greater efficiencies.)
Mostly agreed. But the primary efficiency loss isn't due to "thermal loss" - it's due to pumping losses. When it's cold out, air is denser, so the throttle plate has to remain more closed for the same mixture - and it is harder to pump air past the narrower opening.Ianhill wrote: ↑Feb 08 2019 4:47amTemperature makes a big difference with ice engines too, Cold air is more dense and needs more fuel to reach it's stochmetric value of 15-1 so the Injectors have to work harder and throw more fuel in. This then means you get more power per stroke but your efficiency drops with worse thermal loss in the block.
If you dont mind me asking bill how you learnt all this random information ?billvon wrote: ↑Feb 08 2019 12:08pmMostly agreed. But the primary efficiency loss isn't due to "thermal loss" - it's due to pumping losses. When it's cold out, air is denser, so the throttle plate has to remain more closed for the same mixture - and it is harder to pump air past the narrower opening.Ianhill wrote: ↑Feb 08 2019 4:47amTemperature makes a big difference with ice engines too, Cold air is more dense and needs more fuel to reach it's stochmetric value of 15-1 so the Injectors have to work harder and throw more fuel in. This then means you get more power per stroke but your efficiency drops with worse thermal loss in the block.
That particular tidbit came from working with Ford on their VCC110 program. I was working for a subcontractor but worked with their engineers quite a bit - and they were looking at both EV's and hybrids, and looking at ways to optimize both. Understanding where ICE engines were most efficient was critical for optimizing hybrids.
That gives good reasoning to all this juicy info I read of yours then, all my ev knowledge comes from potching about with stand on scooters or the ice side ive only learnt from reading and building a basic turbo track car, my main college was for electrical installation so I knew a bit of the language and a bit about older type motors, I've learnt more outside of college than in and I'm only 33. It's costs to much for me to further my education.billvon wrote: ↑Feb 08 2019 2:06pmThat particular tidbit came from working with Ford on their VCC110 program. I was working for a subcontractor but worked with their engineers quite a bit - and they were looking at both EV's and hybrids, and looking at ways to optimize both. Understanding where ICE engines were most efficient was critical for optimizing hybrids.
Like the freevalve system used in the agera, I looked into the past of rover uk and they had a patent for a electrically controlled hydraulic actuated valvetrain back in the 90's and developed it over a few years then flopped.Punx0r wrote: ↑Feb 09 2019 5:35amThe avoidance of pumping losses is one of the reasons diesel engines are generally more efficient than spark-ignition ones like petrol/gasoline. Although a solution to this is valve-throttled engines that use variable valve lift instead of a throttle plate are supposed to give up to a 10% efficiency gain. The Fiat 500 multi-air is probably the most common car with this system.
I would add that the Prius uses an Atkinson cycle engine. It is not a "true" Atkinson in that the piston always moves the same distance regardless of position in the four-stroke cycle. Instead, Atkinson operation is obtained by leaving the intake valve open for too long; some of the charge is ejected before the intake valve closes, resulting in a small volume of mixture compressed followed by a large expansion during the power phase. Variable valve timing allows operation in both Atkinson mode (most of the time) and conventional 4-stroke operation during wide open throttle operation (for maximum power.)