Musk's Powerwall

[Skipjack]

I might not have heard it right, but I thought Musk said during the presentation that the inverter is part of the system.

Per the Tesla website:

Installation
Requires installation by a trained electrician. DC-AC inverter not included.

Uhm, OK. That makes the thing a bit less attractive. Wonder why they did not include that in the package.

[Tom Ligon]

Uhm, OK. That makes the thing a bit less attractive. Wonder why they did not include that in the package.

I'd say a package deal built around the Tesla battery is likely, but the question is, how much would Tesla provide? The website suggests they expect outside installers to put these in.

The battery may contain a charge controller. The battery itself sits at 350-450 V, but modern charge controllers are typically switchers and can, in principle, work from any voltage. But it is likely they'll shoot for something in that voltage range, and PV arrays in the hundreds of volts are typical. This does require some special equipment, though.

The National Electric Code, last I checked, requires PV arrays to have a disconnect for both sides of the panel before entering the house. At hundreds of volts DC, that's a no-joke serious switch. My 21 V system can use Square D QO breakers, but above 48 V you're into specialized switchgear. Likely that's an outside supplier used to UL and NEMA standards.

The PV panels will almost certainly be Chinese. They've undercut the market and driven almost everyone else out of the business.

The panel wiring is high-temperature and outdoor stuff, and not standard household wire. Suppliers exist for it, so Tesla would not be the source.

Tesla might make the charge controller and DC-AC inverter ... they certainly use comparable gear in their cars. However, again, it must pass UL and NEMA standards for household PV installations, and there are some very good suppliers doing this already. Trace Labs I think is now part of Sorensen, and they would be a good candidate for these parts.

The big difference between what Tesla proposes and the cogeneration systems most people are designing today is that the cogeneration panels have inverters right on the panels, and they're not intended to use with battery storage. They are specifically designed to feed excess power back down the lines, something Musk quite reasonably is trying to get away from. Any really large scale distributed PV system needs storage, otherwise the grid system becomes nonsense, and Tesla is providing the missing piece. But it is a big break from the systems other outfits are pushing today.

The batteries are the messy part, and a Tesla specialty.

[Giorgio]

The system has two versions at the moment, one for $3k and the other for $3,500. http://www.teslamotors.com/powerwall

The cheaper one (7 kWh) is intended for load leveling during the day, and the other (10 kWh) is intended for backup.

This is what really catch my eyes.
A 3kWh difference for 500 Usd, makes it at around 150 Usd/kWh for the storage medium. That's quite an impressive number....
Seems like under 100 Usd/kWh could become a reality soon.

[pdxpyro]

Hmmmm. The 10kWh version is $3500. The 7kWh version is $3000. That still pencils out to $350 and $428 / kWh respectively, correct? True . . . the difference is only ~$167, but we're still a loooong way from $100 / kWh.

The system has two versions at the moment, one for $3k and the other for $3,500. http://www.teslamotors.com/powerwall

The cheaper one (7 kWh) is intended for load leveling during the day, and the other (10 kWh) is intended for backup.

This is what really catch my eyes.
A 3kWh difference for 500 Usd, makes it at around 150 Usd/kWh for the storage medium. That's quite an impressive number....
Seems like under 100 Usd/kWh could become a reality soon.

[Giorgio]

...makes it at around 150 Usd/kWh for the storage medium. That's quite an impressive number....

Hmmmm. The 10kWh version is $3500. The 7kWh version is $3000. That still pencils out to $350 and $428 / kWh respectively, correct? True . . . the difference is only ~$167, but we're still a loooong way from $100 / kWh.

I was referring to the price of the storage medium, not of the final battery.
From the ~167Usd/kWh you have to remove the extra labor, handling, testing, electronic cost to manufacture the bigger unit (factor them at around 10% from personal experience) and you get the 150 Usd/kWh I mentioned. Again, only for the storage medium, i.e. the battery itself.
Considering that here in Shenzhen a "good" Li-ion battery can't be sourced for less than 280-350 Usd/kWh, that's quite a bargain price.

Cheaper than that here you can only find from BYD factory with their "Lithium-Iron Phosphate" battery packs. What's also interesting is that they are expanding their battery factory to 10 GWh/year in 2015 with plans already laid out to reach 30 GWh/year within next 3 years to contrast Tesla Giga factory.

Interesting times ahead for the battery industry....

[paperburn1]

the 300 pound elephant in the room with regards to renewable energy has always been storage of excess energy for use when needed. As most systems are custom designed I can see where you at first would not want to provide a turn key solution as that would limit your market. Later on you might strive to that goal but right now it would not be in the best interest. I am sure that right now several manufacture of inverter chargers are looking forward to accommodate these new packs. after all this part is now a industry thing rather than a experimental thing as you can get several of these types of chargers already on the market.

[pdxpyro]

This is what I can't quite understand. (Really! I'm not trying to "troll" here.)

Do renewables really produce "excess" energy? I've been looking at PV systems for my home (in the Pacific NW of the USA). Even with the roof fully packed, it will only produce a fraction (20-25%-ish) of our total kWh usage. That's my micro view.

Expand the same notion to more of a macro view . . . We have wind turbine farms in the Columbia River Gorge. These, too, only produce a small fraction of the power usage in the region.

Why, then (back to what I don't understand), do we need storage? I suppose at some point (looks to be much to far in the future) if renewables (intermittent?) can generate more than we can consume at any point in time, I'd see the storage as an issue. But aren't we very far from that point?

the 300 pound elephant in the room with regards to renewable energy has always been storage of excess energy for use when needed. As most systems are custom designed I can see where you at first would not want to provide a turn key solution as that would limit your market. Later on you might strive to that goal but right now it would not be in the best interest. I am sure that right now several manufacture of inverter chargers are looking forward to accommodate these new packs. after all this part is now a industry thing rather than a experimental thing as you can get several of these types of chargers already on the market.

[Maui]

So I have absolutely no idea what the typical numbers are here (basically have no idea what I'm talking about)...

... still, from a micro perspective, if you are generating that 20-25% while you are at work and not using any power to speak of, it's just going down the drain right? So even if it is true that a typical home would be far from being able to be self-sufficient, in order to utilize the power you are generating, seems to me stone-cold common sense that you'd want to be storing the excess power generated during the day for use when you need it.

Similar situation from a macro perspective. Taking power plants on and offline as power demands and winds fluctuate takes time and I imagine at any given moment an electric utility needs to make sure they have a certain amount of excess power available. As greater percentages of power get generated via renewables, I imagine the power generation is only going to fluctuate more. Doesn't it make sense that excess power be stored and used when demand spikes or turbine output drops? Not only do you get better utilization of the generated power, but it may save having to temporarily bring another power plant online.

EDIT: Also, I think part of the idea is that as enough homes get their own batteries, "micro" solves the macro problem by having smart homes that draw power from the grid when demand and prices are low then use stored power instead of the grid when demand and prices are high. If enough homes are doing this, it should keep demand from a macro perspective essentially flat.

[JoeP]

The main problem, and it might have been mentioned somewhere in this thread or another, is that the grid must be a 100% capacity fall-through to any solar/wind generation infrastructure.

The micro example: if your personal solar array gives you %150 capacity averaged out for any day in the year, there may be days or even weeks where that percentage is pretty close to zero. Thus, you count on the grid for producing almost all your power needs in those intervals -- so solar/wind isn't even a good backup. I personally have a 5.5KW gasoline generator which works every time when I get the day (or three) without power and it doesn't degrade like batteries.

The capacity of the grid (fossil fuels, hydro, fission) cannot be reduced even with widespread PV panels and wind turbines all over the place.

No doubt solar & wind can/will reduce consumption, and it is the main thing greenies care about, but it is really a bad solution when compared to even fission.

[pdxpyro]

"down the drain" - Not quite. As I'm connected to the grid (I realize off-grid folks have completely different considerations), the power generated by PV while I'm at work will flow backward through my meter. Essentially, the grid (someone else using power while I'm at work) is my "storage".

I guess this might be more of a factor if my provider started some tricky peak-hour pricing regimes. Then, it might make more sense for me to store/use/release PV power when it made most economic sense.

So I have absolutely no idea what the typical numbers are here (basically have no idea what I'm talking about)...

... still, from a micro perspective, if you are generating that 20-25% while you are at work and not using any power to speak of, it's just going down the drain right? So even if it is true that a typical home would be far from being able to be self-sufficient, in order to utilize the power you are generating, seems to me stone-cold common sense that you'd want to be storing the excess power generated during the day for use when you need it.

Similar situation from a macro perspective. Taking power plants on and offline as power demands and winds fluctuate takes time and I imagine at any given moment an electric utility needs to make sure they have a certain amount of excess power available. As greater percentages of power get generated via renewables, I imagine the power generation is only going to fluctuate more. Doesn't it make sense that excess power be stored and used when demand spikes or turbine output drops? Not only do you get better utilization of the generated power, but it may save having to temporarily bring another power plant online.

EDIT: Also, I think part of the idea is that as enough homes get their own batteries, "micro" solves the macro problem by having smart homes that draw power from the grid when demand and prices are low then use stored power instead of the grid when demand and prices are high. If enough homes are doing this, it should keep demand from a macro perspective essentially flat.

[GIThruster]

This is what I can't quite understand. (Really! I'm not trying to "troll" here.)

Do renewables really produce "excess" energy? I've been looking at PV systems for my home (in the Pacific NW of the USA). Even with the roof fully packed, it will only produce a fraction (20-25%-ish) of our total kWh usage.

If you have room for the panels, you certainly want enough to produce more than you need when the sun is bright, knowing for instance you will have none after sunset, during storms, etc. It is often possible to do this, but not always. Depends upon location, what is between you and the sun at any given time, (such as the neighbor's tree), how much room you have for panels, etc. generally the more rural you are, the more southern and the drier you are, the more sunlight you can receive at that site, which is usually measure in "sunlight hours per year". If you have enough of these you can justify one sort of system, but with less you will need to be satisfied with another sort of system. In most of Alaska, there are generally no systems that work well, for lack of sunlight 6 months of the year, extreme cold, snow that would cover the panels, etc.

The beginning of the answer to this question is thus to take the sunlight hours/year and subtract from it those hours where obstacles would interfere with the sunlight, such as nearby trees, building, etc., then look at how much light you should reasonably have access to, including multiplying by the % difference between your panels and their percent collection at the various angels the sun will present itself. Most of the time the panels are not really collecting across their full area, but a much smaller area defined by the angle of incidence v normal. After that, divide out your conversion rate, and see what the cash value is of the energy you can produce. That is what is necessary to know whether to invest in solar. The only thing that has changed recently, are the costs since the feds are heavily subsidizing solar since OBama came it office.

[ltgbrown]

Pdxpyro's question, "Do renewables really produce "excess" energy?" could be looked at differently.

How about thinking how much energy did it take to make the panel versus how much it produces over its lifetime? Taking into account the energy to mine for the minerals, process them, transport them, manufacture the cells, assemble the panels, package the panels, transport the panels, and install the panels. Oh by the way, the same accounting for the equipment needed at every step (mining equipment, processing equipment, transport equipment, you get the point). And the additional equipment needed, like batteries (or some other energy storage mechanism), inverters, cabling, etc. If you add all that up, does it produce more than was needed to produce and install it?

My gut says it does, but by what factor?

[Skipjack]

Do renewables really produce "excess" energy? I've been looking at PV systems for my home (in the Pacific NW of the USA). Even with the roof fully packed, it will only produce a fraction (20-25%-ish) of our total kWh usage. That's my micro view.

How much power does your household need a day?!
Here is an example that I found for a solar panel that is actually pretty cheap. this one gives 1.2 kWh a day and costs only 1,140 USD.
It is only 2.5 by 1 meter, or 100 by 40 inches. An average home needs 5,000 kWh a year. Assuming that you need about that, you should be able to get away with an installation 150 by 400 inches in size. That does not sound all that big to me.
http://www.homedepot.com/p/Grape-Solar- ... /203505963

Edit and here is a solution that produces on average about 5,000 kWh a year and is almost exactly the size I calculated earlier.

[pdxpyro]

Hmmm . . . It could be looked at in this way, but it would be a fairly tortured view. IMHO.

Pdxpyro's question, "Do renewables really produce "excess" energy?" could be looked at differently.

[Skipjack]

Pdxpyro's question, "Do renewables really produce "excess" energy?" could be looked at differently.

How about thinking how much energy did it take to make the panel versus how much it produces over its lifetime? Taking into account the energy to mine for the minerals, process them, transport them, manufacture the cells, assemble the panels, package the panels, transport the panels, and install the panels. Oh by the way, the same accounting for the equipment needed at every step (mining equipment, processing equipment, transport equipment, you get the point). And the additional equipment needed, like batteries (or some other energy storage mechanism), inverters, cabling, etc. If you add all that up, does it produce more than was needed to produce and install it?

My gut says it does, but by what factor?

I think that some of that factor can be seen by how much cost went down since the first panels were introduced. All that energy has to be paid for by someone and that inevitably cuts into the profit margins for these panels. Certainly some of the energy needed to make them has become lower as well, but I think that most of the lower cost is due to improved manufacturing and economics of scale.