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Powerwall 2 and Integrated Solar

powerwall.tesla.com

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Re: Powerwall 2 and Integrated Solar

#201

Post by chmike »

jacquesm wrote: post #172
j1vms wrote: post #165

Earlier quoted context omitted.

> The big difference is because of air conditioning and baseboard heating (...) Which makes you wonder why there is not as much high-profile attention on A/C (and to a lesser extent electrical heating) as being a problem worthy of rethinking by Silicon Valley (perhaps even ahead of solar, in North America).

There is quite a bit of work being done on solar powered airconditioning. I experimented myself with this about 10 years ago using two back-to-back Stirling engines with the first powered by the sun and the second being run in reverse to cool a working fluid. It's an interesting field, you'll learn more about Carnot cycles and thermodynamics than you ever wanted to :)

A climatization using DC current from capacitors charged with solar panels might be more interesting in mild hot regions.

If I understood well AC is optimized for carrying current on long distance with minimal loss. But most electric devices use DC. They need an AC to DC convertor with some energy loss.

Solar panels produce DC and is usualy converted to AC with some loss. Then, in most electronic devices, this AC is converted back into DC in the device power transformator.

What waste of energy. Shouldn't we do something about this ?

Re: Powerwall 2 and Integrated Solar

#202

Post by [deleted] »

jacquesm wrote: post #172
j1vms wrote: post #165

Earlier quoted context omitted.

> The big difference is because of air conditioning and baseboard heating (...) Which makes you wonder why there is not as much high-profile attention on A/C (and to a lesser extent electrical heating) as being a problem worthy of rethinking by Silicon Valley (perhaps even ahead of solar, in North America).

There is quite a bit of work being done on solar powered airconditioning. I experimented myself with this about 10 years ago using two back-to-back Stirling engines with the first powered by the sun and the second being run in reverse to cool a working fluid. It's an interesting field, you'll learn more about Carnot cycles and thermodynamics than you ever wanted to :)

[deleted]

Re: Powerwall 2 and Integrated Solar

#203

Post by [deleted] »

Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

[deleted]

Re: Powerwall 2 and Integrated Solar

#204

Post by crb »

superfx wrote: post #196

Does anyone know where the video was filmed? It looks like it might be a neighborhood in the Bay Area.

The "Colonial Street" set at Universal Studios in Burbank, California. Most famous as the set of Desperate Housewives.

https://en.wikipedia.org/wiki/Colonial_Street

Re: Powerwall 2 and Integrated Solar

#205

Post by maxerickson »

Annatar wrote: post #149

So I used the calculator on Tesla's web site, in my case, I'd want 3 powerwalls and I'd want a solar installation to complement it: $18,000 USD. That's still way too high: $1,800 - $2,500 would have been acceptable. That is how much I'm willing to pay for some solar panels, three batteries, and a little bit of electronics (processed sand) to control the lot. As far as I'm concerned, this is all still hype. Prices nee…

A more interesting metric might be months of pay back time. $1,800-$2,500 seems like an arbitrary number you made up.

Like if your power bill averages $150 (I realize it probably doesn't) and you plan to stay in place for a few years, then something like 50*$150=$7500 is easy to consider and is much higher than the numbers you tossed out (that's just over 4 years to pay you back).

I mean, I agree with the point you are implying, that people won't be overwhelmingly excited with solar until the payback goes below 2 or 3 years, but I think it also makes sense for longer payback times.

Re: Powerwall 2 and Integrated Solar

#206

Post by Brakenshire »

anthay wrote: post #168

I was pleasantly surprised to see prices quoted in £GBP - the Powerwall is available in the UK! But, we don't have enough sunlight here to run a typical house off-grid year-round, do we?

In the UK we get about a quarter of the incident energy from sunlight in Winter than we do in Summer. You could do it by overbuilding your solar array by 4 times over what's required in Summer. That might actually be reasonable if solar prices carry on going down. Or you could do it by having some sort of micro-CHP system which produced electricity and then uses the waste heat to heat the house.

But, yeah, I think this is the major outstanding issue with renewables at the moment. Solar with battery storage looks like it will get parity with the grid anywhere near the equator, where you don't need seasonal storage. The UK needs additional solutions. I think we should be putting more money into developing micro-CHP personally. British Gas were trying out a Sterling engine system a few years back, there are also some in development using Fuel Cells.

Re: Powerwall 2 and Integrated Solar

#207

Post by novaleaf »

antisthenes wrote: post #184
Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

The reason their calculations are so high is because in the US, typical houses are made as cheaply as possible, pretty much with paper, plastic and vastly insufficient insulation. That may have changed in the recent years, but holds true for most residential properties built before 1980.

If you think the USA had bad standards, In Thailand it's common (even today!) to build skyscrapers out of cement and single-pane glass.

To bangkok office workers, it's pretty natural to blast the AC all day and have the office still be above 28'C

Re: Powerwall 2 and Integrated Solar

#208

Post by metric10 »

Loic wrote: post #118

Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage? On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. Thi…

They're probably factoring in a charging Tesla in the garage.

Re: Powerwall 2 and Integrated Solar

#209

Post by sfblah »

manav wrote: post #75

I haven't looked into it yet, but I'm curious about using utilizing my Teslas in case of emergency for power. With 75kwh+ each (leased so no concern about cycles) I don't think I'd need a powerwall at home.

Can you explain to me your economic thinking behind leasing two Teslas? Are you super rich or do you have some other thinking that went into that decision?

Re: Powerwall 2 and Integrated Solar

#210

Post by will_hughes »

usrusr wrote: post #169
will_hughes wrote: post #117

Earlier quoted context omitted.

The problem with phones is that they don't have good management - the battery doesn't have active cooling, or heating when needed. They're also charged to full capacity or depleted to empty a lot of the time. These things are what kills battery life.

Phone batteries get hot, but they have plenty of thermal connection with the environment. This is nowhere close to the magnitude of a heat problem you would have within a massive multicell pack, where the direct environment of one hot cell would be a few other hot cells. Active cooling is not something you add to a pack the size of a Tesla to make it survive a few more cycles, it needs it to survive the first cycle.…

> Does Tesla come with an UI where you can do something along the lines of

No, not like that.

The charge UI interface has a 'daily' indicated range that you can set, and the top ~10% is marked 'Trip'.

Example from a screenshot of the mobile app shows what i mean[1]

The advice given to owners is to normally set the charge limit to somewhere in the daily range depending on their expected driving needs the following day.

As stated by others, it's most damaging to cells to be kept at the extremes of their charges. Controlling temperature is another big factor in it too, that's why Tesla has active temperature management in the cars and stationary storage products.

Here's real-world numbers from owners[2] and shows that the degradation even after a lot of miles and with older packs isn't terribly much.

[1] http://imgur.com/a/Cr0Cq

[2] https://electrek.co/2016/06/06/tesla-model-s-battery-pack-da...

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