Live Tesla Shareholder meeting

[WildhavenMI]

Funny how people say California's F'd up. There's always many ways to look at any situation.

This looks like Michigan as looking at this situation, NOT from the consumer/public perspective. They are taking away any incentive to help the grid by adding solar.

Michigan utilities are governed by something called the Michigan Public Service Commission. In theory it is a regulatory agency, but in practice the appointed commissioners are empty suits that sign on to whatever the two big utilities put in front of them.

Sponsored

 

[Crissa]

So if I want to charge off solar, I don't just need a huge array (which I'm fine with) but I need 70kWh of backup battery to draw from just for vehicles. And if they charge most every day (lets say 300/year), that 1,500 charge cycle life expectancy on a Powerwall is only 5 years long.

You need solar panels or sharing agreement where the cars sit all day ^-^

-Crissa

 

[WildhavenMI]

You need solar panels or sharing agreement where the cars sit all day ^-^

-Crissa

Well, the one sits in a hospital parking lot for 13 hour stretches (my wife's Bolt), and you'd think they'd have EV spots but they don't.

My PacHy and future-CT sit...wherever the job is, which is usually in the bush somewhere. I could carry a pop-up array with me but that might be a big pain in the ass.

 

[ajdelange]

I'm going through this modeling right now. ... Well insulated, ductless minisplits air-source heat pump, hybrid water heater, etc. R-32 walls, R-50 ceiling, in Michigan. And it doesn't matter what more I put in the house - the ~70kWh/day my 2 EVs will pull down dwarfs the household consumption by a LOT.

Let's take 2 CT requiring 410 Wh/mi. At the wall that's about 410/0.9 = 467 Wh/mi. The average American drives 13,500/yr (approximately) so if each is driven that much you will need 17000*.467 = 12.6 MWh/yr which is 34.5 kWh/da. So you are planning for 2 large BEV each of which you plan to drive twice the average (or one of which you plan to drive the average and the other 3 times that). If that's the case well then that's the case but it did catch my notice.

Now having expressed my surprise that you will use 70 kWh/da for charging BEV l will also express my surprise that this dwarfs the household consumption by a lot (in caps). The average US consumption is 30 kWh but I don't think the "average" US residence has two big BEV either. FWIW my average consumption last year was 98 kWh/da for a house that is not particularly big and is heated and cooled mostly by a geo thermal system which is, of course, the big load. You live in Zone 4 or maybe 5 and are, thus, going to need something like 50,000 BTU per thousand square feet. Assuming 50% duty cycle (or the equivalent thereof for an inverter system) and a COP of 4 you'll need something like 50000/3412*0.50/4.00*24 = 44 kWh per day thousand square feet. Keep in mind that this will go up when the weather gets colder as COP drops with outside temperature (one of the advantages of geo but the A/A units these days are amazing).

And the most challenging part is modeling for charging. These are vehicles that leave the house at 7am (which is dark a big chunk of the year) and don't return home until 6p-7p or later most days, when it is either late hours or dark.

It certainly is best to make hay when the sun shines if you can. If you must charge at night you will have to pay the additional 10% round trip efficiency tax for the Powerwalls bringing the amount of energy that must be collected and stored for the vehicles to 70/.9 = 77.8 kWh.

So if I want to charge off solar, I don't just need a huge array (which I'm fine with) but I need 70kWh of backup battery to draw from just for vehicles. And if they charge most every day (lets say 300/year), that 1,500 charge cycle life expectancy on a Powerwall is only 5 years long.

The Powerwalls are now warranted for 8 years.

You will have the 77.8 plus buffer zone requirement for the Powerwalls as a minimum but if you are planning on using split packs you will need more for them. The main heating load in winter does not come when the sun is shining. That's when it is the least. Plus in that seasons the sun is like the locals - it heads south and nasty weather rolls in. Just looked at the year's history. In the week around the summer solstice I saw 5.23 hrs/da FSE (full sun equivalant) but this week only 1.73. It's only October and thus the reduction was more from cloud than ephermeris but in any case there will be days, in fact runs of days, when you will see at most an hour FSE. How will you cover those? And even on days where the production is in the 3 or 4 hour region you still must power HVAC, well, refrigerators etc for the periods when clods obscure the sun from a few minutes to an hour or 2. My average load (year round) runs about 98 kWh/da - about what it appears your's will - and I find that even on the sunniest days 25 - 30 kWh day comes from the battery (at night) and in the winter it can be over 100 kWh (note - my battery is infinite: Dominion Energy).

It's a challenging equation, for sure - and something I'm only able to even slightly afford because I've been incredibly lucky in life and have a well paying job.

Yes, extremely challenging. If there isn't a bit of Henry David Thoreau in you (and apparently he turned out to be a big phony) off grid isn't really feasible. Looks as if you'd need the maximum 10 Powerwall configuration (135 kWh - this represents 2.5 months allocation for the largest installer in the Washinton Metropolitan area) at $80 k or so and an array which could fully charge them on 2 hr FSE/day (67.5 kWh ~ 230 panels). Even then you'd need to have means of backup for the days when you don't even get the 2 hrs.

As a reference: I've built a 3 car garage for my BEV. It's design is based on being able to aim 45 panels due south at the optimum elevation angle. It's conditioned with split packs and I figure the 45 panels and 5 Powerwalls will let me charge the cars, run lights and even condition it in the summer but in the winter I don't think there will be enough collection so it has gas heaters as backup. Love to share some data with you but as is everyone else here, I'm waiting for Elon to deliver the Powerwalls. Do note that he said they use the same batteries as the cars and have, thus, been pushed to the back burner.


Any way, it seems a challenging and fun project you are undertaking. Good luck with it! I'd suggest shooting for some other means of heating that doesn't require electricity for more than fans. Many people here in Quebec use nothing but fire wood. Others have pellet stoves which are a bir more automated. As long as the trees you burn are allowed to regrow it's carbon neutral. Another approach is to heat water directly with sunlight and store the hot water in huge subterranean tanks. My sister lives in a house (California) that sits on a huge pile of rocks through which they circulate hot air (from the sun) during the day. Etc.

 

[Ogre]

My PacHy and future-CT sit...wherever the job is, which is usually in the bush somewhere.

Rivian’s are ideal for working in the bush.

(Sorry not sorry)

 

[Crissa]

Well, the one sits in a hospital parking lot for 13 hour stretches (my wife's Bolt), and you'd think they'd have EV spots but they don't.

My PacHy and future-CT sit...wherever the job is, which is usually in the bush somewhere. I could carry a pop-up array with me but that might be a big pain in the ass.

Well, they don't install it if you don't rattle a few bushes ^-^

-Crissa

Sponsored