Tesla Powerwall

[LTLFTcomposite]

So it would need to have a giant contactor/transfer switch, right? Like a standby generator, except it would only need to be "single throw", as the inverter/battery part would remain connected to the load panel. That opens up some possible simplifications since the inverter/battery units wouldn't need to be wired directly back to the transfer switch, but could instead connect directly to the load center. A typical panel has 200A main lugs but could be backfed with a 100A breaker.

 

[RegGuheert]

The PW would have to be a bit more sophisticated as it isn't just going to go off-line; it is going to create a power island. More like an automatic backup generator that has to do the same (cut link to grid and come online to power the 'island' then when grid is back for set time period transition back). The Grid Tied solar inverter simply has to shut down and wait to come back.

The Powerwall does not interact with the AC power grid. It is a DC battery. Only an inverter needs to interact with the grid and Tesla has not made any announcements about any inverter.

 

[Slow1]

The PW would have to be a bit more sophisticated as it isn't just going to go off-line; it is going to create a power island. More like an automatic backup generator that has to do the same (cut link to grid and come online to power the 'island' then when grid is back for set time period transition back). The Grid Tied solar inverter simply has to shut down and wait to come back.

The Powerwall does not interact with the AC power grid. It is a DC battery. Only an inverter needs to interact with the grid and Tesla has not made any announcements about any inverter.

That was rather my initial presumption too - but then I am very puzzled about why it is listed as being listed as "Compatibility: Single phase and three phase utility grid compatible." on their website? Seems that if it ONLY does DC, this is rather misleading isn't it? I mean, heck my AA rechargeable batteries can be hooked up to a charger as well - does that mean they are "single phase grid compatible" too? Something just isn't adding up here (typical of marketing material I know...)

 

[RegGuheert]

Seems that if it ONLY does DC, this is rather misleading isn't it?

Yep. And Elon Musk has everyone chomping at the bit to get one tomorrow!

I mean, heck my AA rechargeable batteries can be hooked up to a charger as well - does that mean they are "single phase grid compatible" too? Something just isn't adding up here (typical of marketing material I know...)

It was all pure marketing. There is no solution to anything today. Just a battery. But Elon Musk has a vision to build an energy business around his battery technology. That vision is what the presentation was all about.

Here is the list of all the things you can do with the Powerwall today (if you had one):

1) Charge it with a string of PV modules with an MPP voltage around 400V.

That's it unless someone can come up with some loads for 350 to 450VDC. If you know of any, please feel free to provide links to them here.

 

[AndyH]

It was all pure marketing. There is no solution to anything today.

Behold the mighty Google:

http://www.jpost.com/Business-and-I...Teslas-solar-powered-Powerwall-battery-402045

Herzliya-based SolarEdge Technologies Inc. will be teaming up with electric-vehicle industry leader Tesla Motors to provide an inverter solution for the Californian company’s new solar-powered Powerwall home battery system, the Israeli firm announced on Monday.

SolarEdge will be supplying an inverter system that will enable photovoltaic (PV) and grid integration with Tesla’s recently announced Powerwall home battery – a storage pack capable of supplying electricity for homes when the sun goes down. Combining their technologies, the partners said they are building upon SolarEdge’s DC-optimized inverter solution and Tesla’s automotive-grade energy-storage technology to provide a more economical solution for residential solar generation.

http://www.pv-magazine.com/news/det...sunrun-hop-aboard-tesla-juggernaut_100019309/

Two leading U.S. solar companies have announced early-adopter partnerships with Tesla’s new Powerwall home storage system, which was unveiled last week at the company’s California HQ by CEO and tech entrepreneur Elon Musk.

U.S. inverter specialist Fronius will collaborate with Tesla from the fourth quarter of the year, bundling its Symo Hybrid inverter with the Tesla Powerwall home battery to customers in Germany initially, before rolling out the package to the rest of Europe and Australia...

Sunrun offers welcome embrace
Tesla’s new home battery system will also be offered as part of AEE Solar’s home PV system. The U.S. distributor of residential solar is a subsidiary of Sunrun, which is one of the leading dedicated residential solar companies in the country, offering solar-as-a-service to American homeowners.

The good news is that there is no reason to have a solution today - as long as there's at least one solution when the batteries start to ship.

 

[RegGuheert]

Thanks, Andy! As I surmised, Tesla wants to redefine home-based energy systems around its uniquely-high battery voltage.

 

[AndyH]

Thanks, Andy! As I surmised, Tesla wants to redefine home-based energy systems around its uniquely-high battery voltage.

You're welcome.

Yes, it appears they do. I really wish they'd decided to provide lower-voltage solutions that fit the current 12, 24, and 48VDC equipment. It's a great business decision though as it limits customers (at least initially) to Tesla's supply chain. All I can surmise at this point is that they don't care about capturing any of the currently-installed systems and are looking outward towards new customers.

 

[evnow]

Powerwall is modular. You can connect up to 9 of them side by side if you have the wall space. So line up 3 or 4 of them if you need that much power.

Also it is 2 kW continuous / 3 kW peak. So you can burst up to 50% over the continuous.

9 of them side by side would be a lot of cash - just for the backup. I can get a NG 16kW backup generator installed for $10k.

All I'm saying is - as a backup I don't understand the use cases Tesla is aiming for.

I've personally not understood the lure of off-grid (not a survivalist) - so I won't go there.

 

[AndyH]

Powerwall is modular. You can connect up to 9 of them side by side if you have the wall space. So line up 3 or 4 of them if you need that much power.

Also it is 2 kW continuous / 3 kW peak. So you can burst up to 50% over the continuous.

9 of them side by side would be a lot of cash - just for the backup. I can get a NG 16kW backup generator installed for $10k.

You'd be using fossil fuel as long as the reason for the power outage didn't also kill the gas supply.

All I'm saying is - as a backup I don't understand the use cases Tesla is aiming for.

Temporal shifting of renewable generation. Charging with off-peak and using the energy during the day. Outages/back-up power. Their main customer isn't likely to be the home user but rather commercial and utility-scale projects - so toss in things like depreciation, tax credits, carbon trading and the like into the spreadsheet.

I've personally not understood the lure of off-grid (not a survivalist) - so I won't go there.

One doesn't have to be a survivalist to want to be off grid. Changing laws, constantly rising energy prices, the desire to not be morally or ethically bound to fossil fuel use...

- Environmental concerns—a desire to use less energy and make as much as possible from renewable sources;
- Independence from the electrical utility for philosophical reasons or to eliminate vulnerability from utility outages
- Political/social values, such as taking responsibility for your energy impacts;
- Cost—depending on how far you are from the grid, it may make economic sense to stay disconnected.

http://www.homepower.com/articles/solar-electricity/design-installation/so-you-want-go-grid

 

[evnow]

You'd be using fossil fuel as long as the reason for the power outage didn't also kill the gas supply.

I'd be fine with that for the couple of times a year we have power loss.

Besides when the power goes, even a big pack of battery doesn't last long - it is just a storage device. Not a energy supplier.

My best option, I think, is if Leaf to Home works well.

 

[Slow1]

My best option, I think, is if Leaf to Home works well.

Yes! I liked that solution, but too bad it hasn't come to US market in any way shape or form. I'm also a bit surprised that Tesla hasn't come out with a solution like that. With the right inverter a Tesla could be my backup battery to practically go off grid... well until I needed to drive it somewhere

 

[RegGuheert]

I'm also a bit surprised that Tesla hasn't come out with a solution like that.

How could they sell you a stack of colorful $3500 batteries to hang on your wall if they offered you that?

 

[Slow1]

I'm also a bit surprised that Tesla hasn't come out with a solution like that.

How could they sell you a stack of colorful $3500 batteries to hang on your wall if they offered you that?

Perhaps true - but consider that you have to have something when you are out taking your batteries for a drive. Maybe that is why the 10kWh is good enough - just long enough to go shopping or re-charge at your nearby supercharger and bring more power home to discharge to the network

Hmm... if one were to find a way to use a Tesla to shuttle power from (free) SuperCharger to home to sell at peak rates, I wonder how long it would take to recover cost of the Tesla... assume a yield of 60kWh (have to keep some reserve capacity to get to/from SC) * $.36/kWh (going with the peak rate someone mentioned here) = about $21 each trip... Do it daily (or about 360 days) somehow and that would add up to about $7500/year (more than I thought starting this foolish calc), so keep it up for 10 years (assuming the usage pattern doesn't raise alarm bells and get you cut off the SC station) and you are close to paying off the car

 

[edatoakrun]

...Hmm... if one were to find a way to use a Tesla to shuttle power from (free) SuperCharger to home to sell at peak rates, I wonder how long it would take to recover cost of the Tesla... assume a yield of 60kWh (have to keep some reserve capacity to get to/from SC) * $.36/kWh (going with the peak rate someone mentioned here) = about $21 each trip... Do it daily (or about 360 days) somehow and that would add up to about $7500/year (more than I thought starting this foolish calc), so keep it up for 10 years (assuming the usage pattern doesn't raise alarm bells and get you cut off the SC station) and you are close to paying off the car

As I mentioned a few days ago (p.7) the "free charging" policy is just one of the problems with Tesla batteries, which will probably prevent them from being used effectively in load balancing, both while in the vehicle, and after they are replaced.

...I do believe that Elon is on a mission here - not just to make money. ...

If so, a mission likely doomed to failure, IMO

="Slow1"...Load balancing for utilities is indeed an important part of a long term strategy...

Yes, BEV batteries have will be an important component of the future grid, but Tesla has pursued policies that will probably make it's products batteries useless for these goals.

There are two major future applications for BEV batteries in grid stabilization/load balancing.

The first is using the BEV batteries while they are in the vehicle.

This requires widespread installation of DC charger/Vehicle to grid devices at useful locations, mostly homes and workplaces.

Tesla instead "Free" supercharger policy, means VtoG is economically impossible.

Sad to say, that huge battery in every S will probably never be available to meet grid demand, not while parked at work, nor while parked in every S owners garage.

Which is part of why Tesla is now trying to sell S owners even more batteries for their garage.

The second application of BEV batteries is in repurposing them is stationary applications, after they lose enough of their initial capacity/energy density to make replacement desirable.

The complexity and cost of using Tesla batteries, which require thermal management for safety reasons, probably makes them a poor choice in most new installations.

IMO, trying to repurpose used S packs for this application involves so many additional challenges, it will probably never happen on any scale.

 

[RegGuheert]

Hmm... if one were to find a way to use a Tesla to shuttle power from (free) SuperCharger to home to sell at peak rates, I wonder how long it would take to recover cost of the Tesla... assume a yield of 60kWh (have to keep some reserve capacity to get to/from SC) * $.36/kWh (going with the peak rate someone mentioned here) = about $21 each trip... Do it daily (or about 360 days) somehow and that would add up to about $7500/year (more than I thought starting this foolish calc), so keep it up for 10 years (assuming the usage pattern doesn't raise alarm bells and get you cut off the SC station) and you are close to paying off the car

Doesn't it eat up the tires when you are carrying that much energy around?

 

[Slow1]

As I mentioned a few days ago (p.7) the "free charging" policy is just one of the problems with Tesla batteries, which will probably prevent them from being used effectively in load balancing, both while in the vehicle, and after they are replaced.

I don't see where I've suggested that batteries in EV's are a part of the load balancing solution. Frankly I have a hard time imagining VtoG being a significant part of load balancing if the EV's are actually being used as a vehicle...

I have read and re-read your statements but I still don't understand how you correlate the "free charging" policy with anything to do with load balancing. Certainly I don't see how this policy could be a a problem with the Tesla batteries.

My attempt to provide a silly example of abusing the free SC network was more one for amusement than anything. I am far from suggesting this is a good idea or even one that Tesla should allow to occur (and I do believe they could easily prevent through monitoring/access restrictions).

Batteries in an EV should be there with sufficient capacity to meet demands of the vehicle use. Balancing capacity (which equates to range) with available charging resources (time and locations) is likely to be a key to success. IMO using the batteries for home power is a nice idea for emergency use, but not something I'd be advocating for routine use - why mount batteries in a mobile platform if the main use is stationary?

 

[RegGuheert]

Batteries in an EV should be there with sufficient capacity to meet demands of the vehicle use. Balancing capacity (which equates to range) with available charging resources (time and locations) is likely to be a key to success. IMO using the batteries for home power is a nice idea for emergency use, but not something I'd be advocating for routine use - why mount batteries in a mobile platform if the main use is stationary?

The simple answer to that question is to provide more driving range. It is doubtful that Tesla Model S owners drive 250 miles each day, yet that energy is stored and could be available for use on the grid. The battery is experiencing calendar degradation every day, regardless of whether or not it is cycled. IMO, it makes more sense for a Model S owner to share their batteries to support the grid than to purchase ANOTHER set of virtually identical batteries to serve the same purpose. The battery and the inverters are already in place. Only a four-quadrant inverter capable of bidirection power flow will be necessary. Such a device is only marginally more expensive than the one already purchased for the car.

Some might say the fact that your car is not at home when you are driving it is an issue. I would counter that the load tends to follow YOU, so your car may be more valuable providing power where you are. If you work at a factory, it might come in handy to allow your car to help power the factory. If you are at Starbucks, that might be the best place to supply power. But this all requires a different kind of business relationship, infrastructure and real-time communications between the car and the power grid the to make it all work. Will it ever happen? Perhaps...

 

[Slow1]

Some might say the fact that your car is not at home when you are driving it is an issue. I would counter that the load tends to follow YOU, so your car may be more valuable providing power where you are. If you work at a factory, it might come in handy to allow your car to help power the factory. If you are at Starbucks, that might be the best place to supply power. But this all requires a different kind of business relationship, infrastructure and real-time communications between the car and the power grid the to make it all work. Will it ever happen? Perhaps...

I see your point - the basic reality is most vehicles spend far more time parked than actually on the road. However the complexity of coordinating such a solution (and the additional infrastructure required to support it) seems to be a significant barrier.

I wonder, however, if a far simpler solution would be to have the vehicle's battery be of a modular design such that you can 'park' your extra battery capacity at home, hooked to the grid, when it is not needed. So, if your daily commute requires 30kWh of power you leave 50kWh at home to play grid balancer, if you need 50Kwh one day (hey, it's Friday and you might get invited to hang with the gang), you leave the 30kWh part home, and if going on a long trip you take all 80kWh (fill in with your own favorite numbers for breakdown). While this may seem complex on the surface it at least has far less social complexity as the driver is the only one who needs to provide infrastructure and reaps the full benefit of whatever load balancing incentives exist.

With a proper design it could be as simple as backing into a dock (let the car self-dock, a roomba can do it and cars can drive themselves so why not), then selecting the battery capacity of the day from the car's touch screen, then driving off leaving whatever behind. Heck, you could even stop by to swap for a fully charged battery if you so desired (have the car 'talk' to the home battery system to notify of the planned swap and re-charge as needed)

I have no idea what the cost of such a design would be but I have no doubt it is technically possible.

 

[TimLee]

...
I have no idea what the cost of such a design would be but I have no doubt it is technically possible.

There are a huge # of concepts that are technically possible but completely impractical.
Did you miss that a single 10 kWh Power wall module weighs 200 pounds?
Automated robotic lifting devices in our garage that add or remove modules from our Tesla S :?: :lol:

 

[cwerdna]

I haven't been following this discussion closely as I'm the wrong target audience (don't own the home I live in, will be moving probably by end of year and I stay within tier 1 on PG&E anyway)...

http://westernsolarinc.com/washington-solar-and-the-tesla-powerwall/ was posted today on costs under "What additional equipment is required to make the Powerwall system work, and how much will it cost to add to my system?"