Tesla's Solar Roofs

[Irace86]

I am a Tesla fan. What can I say? So it is to say to no surprise that I find this awesome. Yet, I can always use a different perspective. Does anyone have anything to share on the subject that is ear bleeding to us fan boys?

[ame="https://www.youtube.com/watch?v=dRqSkR4ENAg"]https://www.youtube.com/watch?v=dRqSkR4ENAg[/ame]

I did notice that Musk failed to give a price for the rooftops--only the price on the new, more-powerful batteries was mentioned. He did say goal of Tesla was to make these rooftops cheaper than standard rooftops, but I am afraid Musk is likely referring to the overall savings. By having a roof that saves money on the electric bill, and by having a roof that lasts longer before needing to be replaced, he may be suggesting that there will one day be a savings, but I believe it is naive to think these will be cheaper to afford, unless installation is so simple, and such a time saver, that labor costs are cheaper. Considering the labor costs involved in the electrical aspects of this system, I don't see labor costs driving affordability.

Overall, this seems like the future, and a large step over boxy solar roof panels, or shinny solar shingles, or more vulnerable solar shingles.

[jvincent]

A quote from an article on the rool/powerwall.

Musk also unveiled Powerwall 2, a new version of the company's residential home battery. It's bigger and boxier than before, and more expensive too at $5,500, but it packs 14 kWh of capacity. Musk says that if you combine a Powerwall 2 with a Solar Roof, you could go "indefinitely" without pulling any power from the grid.

For my particular location, that claim is total horseshit.

I just took a look at my daily consumption for February and this past month and I am averaging about 25kWh of consumption per day. So even assuming I can run off the roof on sunny days and only use the battery on cloudy days it's pretty easy to see how the current battery technology still has a long way to go.

The roof is a good idea though.

[Irace86]

Originally Posted by jvincent

A quote from an article on the rool/powerwall.



For my particular location, that claim is total horseshit.

I just took a look at my daily consumption for February and this past month and I am averaging about 25kWh of consumption per day. So even assuming I can run off the roof on sunny days and only use the battery on cloudy days it's pretty easy to see how the current battery technology still has a long way to go.

The roof is a good idea though.

Good point. I guess it depends on how fast the battery charges, how much light the roof gets and usage. For instance, my iPhone 6 can get to 80-90% charge in like 30 minutes, so I can use a "day's worth of battery" then recharge it fast and have more time with the phone. Some days I can go the whole day without charging it and never get below 30%. Then there are times I am charging it while using it like a person would do if use was higher than what the solar panels could provide, so they needed to use some battery power too.

It will be interesting to see what real would scenarios can come of such a system.

[radroach]

Those solar tiles sure look nice. No mention about how they're wiring up a thousand of these on a roof though. Your average roofing contractor won't be certified for the job installing your electricals, and your average electrical / solar installer isn't equipped as a build contractor. So I suppose there's going to be a bit of specialization in the field, and I bet it will pay well.

[bcj]

edit: WARNING: Moose!

[ame="https://www.youtube.com/watch?v=qlTA3rnpgzU"]Solar FREAKIN' Roadways! - YouTube[/ame]

[Irace86]

Originally Posted by jvincent

A quote from an article on the rool/powerwall.



For my particular location, that claim is total horseshit.

I just took a look at my daily consumption for February and this past month and I am averaging about 25kWh of consumption per day. So even assuming I can run off the roof on sunny days and only use the battery on cloudy days it's pretty easy to see how the current battery technology still has a long way to go.

The roof is a good idea though.

I took a look, and we average 250-275kwh per month. That is less than 10kwh per day. So assuming the battery pack takes a day to charge, we would be ok.

[radroach]

@jvincent I don't think anybody is going to argue that solar anything would be efficient in canada, especially during February. Do you run an electric heater there? I would have figured gas would be popular up there?




I don't think it's that hard to get your consumption down. Easiest household items are clothes drying, lighting, and air conditioning. For example, using a hand crank washing machine and a soft-spin dryer and hanging on a clothes line I save about 2kW per laundry load. That's maybe $.25 of electricity I'm saving, but that would be a significant way to conserve electricity if you were hypothetically living off-grid on a solar / battery setup.

[jvincent]

Originally Posted by radroach

@jvincent I don't think anybody is going to argue that solar anything would be efficient in canada, especially during February. Do you run an electric heater there? I would have figured gas would be popular up there?

We run natural gas for heat and our stove is gas as well. There are some parts of the country, most notably Quebec, where they are almost completely electric power because it is so cheap there because of the hydro-electric dams.

In our particular case we don't run the A/C nearly as much as others do up here because quite honestly most of the time it's not hot enough. In the winter months most of the electrical consumption is lighting because it dark for a lot longer.

I actually credit Tesla for pushing the envelope on this kind of thing but Musk does a disservice when he makes claims that don't stand up to simple inspection.

Even in a sunny area a 10kWH battery won't be nearly enough to guarantee you won't need power from the grid. All you need is 3 or 4 rainy days in a row and your battery is probably dead unless you are running just the bare minimum (fridge, lights at night).

I'm an EE by degree and while power isn't my field directly battery life is important to what I do work on. The reality of the situation is that while it is getting incrementally better battery technology simply doesn't have the energy density of good old oil or gas.

Whoever comes up with a practical way of storing solar power in LARGE quantities is going to be a zillionaire.

[Dadhawk]

Here's an additional article on it at MSN Money (assuming that isn't what you are pointing to, it's getting blocked at work)

Primarily it looks like they are purchasing much of this, since it depends on approval of a $2.2B purchase of SolarCity.

I think this make a lot of sense and, assuming its not stupid expensive, I would build it into a new house.

I could run off the grid with this right now. I would have a backup natural gas whole house generator "just in case".

In the article I've attached they are dodging the cost question, which means it's expensive. The size of a roof has little impact on the unit cost. Roofing (at least residential) is typically priced in "Squares" (100sq ft) with adjustment for roof pitch and materials used. My guess is, like in the article, this is above the cost of slate, not exactly a typical residential roof covering.

[jvincent]

Originally Posted by Dadhawk

I think this make a lot of sense and, assuming its not stupid expensive, I would build it into a new house.

I could run off the grid with this right now. I would have a backup natural gas whole house generator "just in case".

Given the lack of pricing info, I would assume it's stupid expensive.

Your "just in case" scenario highlights the issue. For solar to really catch on, the just in case scenario needs to go away. It has to be reliable enough that the probability / frequency of outages is a non-issue.

As an example, very few people up here have backup generators. The electrical distribution grid is so reliable, and gets repaired so quickly in the case of storms, that nobody really considers one. Sure there's an uptick in emergency generator sales every 20 years or so when there's a huge ice-storm but that's about it.

My personal preference is for small scale nuclear, but too many people are afraid of it for it to ever catch on.

[Dadhawk]

Originally Posted by jvincent

Given the lack of pricing info, I would assume it's stupid expensive.

Yep, that's my assumption as well. Slate runs between $120 and $160 a square foot, so I figure it's north of there.

Originally Posted by jvincent

Your "just in case" scenario highlights the issue. For solar to really catch on, the just in case scenario needs to go away. It has to be reliable enough that the probability / frequency of outages is a non-issue.

Well, to be fair, I run data centers for a living so I'm always thinking redundant redundancy. Since I have natural gas at my house, a backup generator is relatively cheap insurance. But, like you, in the 20 years I've been in my house I've never had the power out for more than 2 hours so its hard to justify the cost.

Originally Posted by jvincent

My personal preference is for small scale nuclear, but too many people are afraid of it for it to ever catch on.

I'm all for a Mr. Fusion powered home! Sign me up!

[radroach]

@jvincent I don't think these systems were meant to be used in an off-grid setting. More likely, the home battery would take energy from the grid during off-peak hours for use during peak-use hours.

Originally Posted by jvincent

Whoever comes up with a practical way of storing solar power in LARGE quantities is going to be a zillionaire.

That's pretty much the whole point of what Elon / this battery system is doing. Put home batteries in thousands of homes that ties into the grid. Solar collections are either used in the home or sent to the grid and stored by other home batteries.

[jvincent]

@radroach, I hadn't read of the batteries being used in a distributed grid fashion, but that would be a good idea.

That said, I don't think the home units are big enough. If you had something like what Ambri (and others) are working on that could be shared in a neighborhood then I think it starts to become more viable.