smkettner
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Re: Tesla Powerwall

Fri May 15, 2015 10:22 am

WetEV wrote:Grid load balancing by controlling charge rates might have enough value to be useful. The car owner gets a slightly lower rate for charging his car. The Utility gets the right to turn off charging for short time intervals as needed.
Yes we have had this for 20+ years to load shed the air conditioner.
Applying to an EV is just a new application of existing technology.

It would be interesting if used in conjunction with Powerwall what rate could be given to fully turn off your house main breaker when requested.
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smkettner
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Re: Tesla Powerwall

Fri May 15, 2015 10:26 am

Speaking of going off grid.... Does anyone see converting a home to DC power? As long as you are on solar and battery it might be time to do away with converting to 120/240v alternating current save for a few small appliances.
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RegGuheert
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Re: Tesla Powerwall

Fri May 15, 2015 10:43 am

smkettner wrote:Speaking of going off grid.... Does anyone see converting a home to DC power? As long as you are on solar and battery it might be time to do away with converting to 120/240v alternating current save for a few small appliances.
Some people move to 12V, but it is a bad idea. Both copper costs and copper losses are much higher at 12V than at 120V. (If you have the same load and the same wire, you have 100X the resistive losses at 12V than at 120V.) In addition, 12V appliances and lights cost significantly more than their 120V equivalents. Also, breaking a circuit is much more difficult (and expensive) with DC versus AC since the voltage waveform does not return to 0V 120 times each second. (OTOH, 12V fuses are cheap.)

It is much better to purchase a highly-efficient inverter and use safe, standard, inexpensive wiring for your home. You'll likely use less energy overall that way.

If you are thinking of a higher DC voltage, then I'm not sure where you would get your loads for it or how you would meet safety standards.
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2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
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edatoakrun
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Re: Tesla Powerwall

Fri May 15, 2015 11:01 am

Slow1 wrote:
edatoakrun wrote:IMO, high battery costs mean the economic use of batteries for the foreseeable future is in integrating BEV batteries with the grid, both while they are in the vehicle and afterward, as I posted previously:

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.


I disagree here - we do NOT need V2G devices in order to use BEV batteries while in the vehicle. To advocate for putting V2G everywhere is to add unnecessary complexity to the solution. Use batteries in the cars to propel the vehicle - if the battery pack is too large for this, buy a smaller battery pack...


Everyone wants a BEV with the single charge range to meet the majority of their regular needs, not just the daily average.

Which means, on most days, every BEV has a significant capacity surplus.

I rarely use more than ~10 kWh (less than 50% of my battery pack's present available capacity) in my usual daily driving of 50-55 miles, but I certainly wouldn't want to drive a BEV with only ~10 kWh total available capacity.

It will probably always be impractical to remove surplus batteries from your vehicle on those days you don't need all of them for a long trip.

It could be very practical to use a V-to-G/G-to-V site to discharge the surplus energy your BEV battery pack holds, especially when the discharge can be timed to meet peak demand, providing a significant financial incentive more than covering the cycling costs.

You don't want or need V-to-G "everywhere".

For example, I doubt anyone is going to regularly stop at a highway DC charge site just to make ~ a fast buck by selling a few kWh.

You want V-to-G wherever you will regularly have a significant energy surplus in your battery during periods of peak grid demand, producing the highest priced bid for your excess kWh, such as at those homes and at workplaces where regular parking patterns make the discharge/recharge cycle practical and profitable.
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AndyH
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Re: Tesla Powerwall

Fri May 15, 2015 2:34 pm

Slow1 wrote:
AndyH wrote:
edatoakrun wrote:Most consumers have no access to TOU rates, which allow them to reduce the cost and environmental impact of their kWh consumption, at all.

TOU rates don't 'allow' anyone to do anything. The only factor is the consumption and that is and always has been in the hands of ALL consumers.

TOU rates DO allow people to benefit from choosing when to consume the power which can have indirect environmental benefits. By time shifting loads more generation can be done at a steady state which benefits all the way around. Granted, one can time-shift even without TOU rate, but the access to TOU lets consumers see direct benefit and thus "allow' them to better manage their energy costs. Total consumption is not the only factor but certainly is a major one.

Sorry, can't agree with this. TOU rates are set by a for-profit business to change consumption patterns to better match their production - on a grid with little storage, where most generation assets can't be turned off for the night, and because THEY profit when peak demand is reduced (because any token 'losses' as a result of people choosing to charge their car at night are more than made up when they don't have to build a new power plant to cover the afternoon cooling surge). It's got zero to do with the consumer or the environment.

Most parts of the country don't have TOU rates. Many parts of the country have 'quantity' rates where kWhs are less expensive the more one uses.

Here's an example from a physicist at UCSD:
Treating energy as precious across the board, we can make gigantic changes to the amount we use without dropping out of society. Tracing my own path, we first look at pilot lights, and the dramatic impact this led to in home heating practices (now using a fifth of the gas I used to). Likewise, I have trimmed my utility electricity use by a factor of five—thanks in part to an off-grid solar installation (efficiency report here, also untimely death of battery), and due to almost no use of air conditioning. I have cut back on use of gasoline as well. Dietary choices can also have a big impact on personal energy: especially meat vs. veggie choices.

http://physics.ucsd.edu/do-the-math/post-index/


Slow1 wrote:
AndyH wrote:
edatoakrun wrote:And (back on-topic) the Powerwall will likely be just another wasted investment in the inefficient past, not the future of energy use.

I can't believe how backward this is! The condition of "no storage" is 19th century. Distributed renewable generation and storage on a smart grid is exactly the course we need.

While you may be correct about distributed generation with storage being desirable, I tend to agree with edatoakrun that the PowerWall isn't likely to be a part of that future. Too little, too expensive, and not offering economic value - more a symbolic gesture. My opinion is that the best thing about the Powerwall is it is getting folks thinking about the value storage can offer to the future and helping facilitate the conversation. I wonder how the economics of their commercial version of it work out - my guess is that it scales well there in volume and thus could well be a real practical solution.

It seems this thread has already gotten stuck on the home user. As has been commented on already, while there may be some limited ways for a home user to play the energy arbitrage game, most of their benefits will be non-financial (no outages, for example) until the bi-directional smart grid process gets rolling. Then homeowners can generate cash flow by contributing their battery for grid stabilization (this doesn't remove the back-up or home-scale load shifting capability). It appears that the Powerwall tech is a slam-dunk for business and utility scale, though. The tech isn't the battery, though - it's the comms and grid interactivity code.

Though I'm a fan of Musk for a number of reasons, Powerwall is not the first grid-interactive battery on the market - there are others inside and outside the US. Powerwall is actually a 'follower' here...
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Graffi
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Re: Tesla Powerwall

Wed Sep 16, 2015 2:35 pm

It has been 4 months since the last post on this thread. Any updates on the Powerwall? Only one more week of summer left for shipments to start. Have they started yet? I put in a reservation but have not heard anything.
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palmermd
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Re: Tesla Powerwall

Wed Sep 16, 2015 3:01 pm

Graffi wrote:It has been 4 months since the last post on this thread. Any updates on the Powerwall? Only one more week of summer left for shipments to start. Have they started yet? I put in a reservation but have not heard anything.



http://www.teslamotorsclub.com/showthre ... -homes-%21

http://teslaweekly.com/issues/53#start
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RegGuheert
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Re: Tesla Powerwall

Thu Feb 11, 2016 3:33 pm

RegGuheert wrote:
smkettner wrote:Does anyone know what inverter will be mated with the Powerwall?
I can't seem to find an off-grid backup inverter with 350-450 vdc input.
SolarEdge is developing an inverter for this application. Target release is the end of 2015.
Just to follow up on this post, SolarEdge has recently announced the availability of their new StorEdge product:
SolarEdge wrote:SolarEdge Technologies, Inc. (“SolarEdge”) (NASDAQ: SEDG), a global leader in PV inverters, power optimizers, and module-level monitoring services, announced today the immediate international availability of its StorEdge™ solution. At the end of 2015, the company already completed a number of StorEdge™ installations in select locations around the world.

Compatible with Tesla’s home battery, the Powerwall, StorEdge™ is a DC coupled storage solution that allows home owners to reduce electric bills and gain energy independence. With StorEdge™, unused solar energy is stored in a battery and used when needed to maximize self-consumption and for power backup. StorEdge™ also supports Time-of-Use management, which promotes energy consumption when electric demand from the grid is low (off-peak rates) and lower consumption when demand is high (peak rates). The backup function allows homeowners to store solar energy and use it during electric outages.
Their StorEdge webpage includes further information on the product including a link to the datasheet.

It is not clear to me whether this new inverter utilizes SolarEdge's new HD Wave Technology or not. CEC-weighted efficiency is listed as 97.5%. That should put round-trip storage efficiency at about 87% given Tesla's 92% efficiency number for the PowerWall. This is just a little lower than Enphase's 90% number for their AC battery, but is significantly higher than traditional battery-based PV solutions. The StorEdge/PowerWall solution also provides electricity when the grid is down, so Enphase' AC Battery does not solve exactly the same set of problems. The datasheet indicates that StorEdge has the same time-shifting capabilities as the AC Battery.

Once we have pricing information, we should be able to compare the per-kWh cost of this solution when compared with the $0.13/kWh we get for the Enphase AC Battery (assuming the application for both is time-shifting consumption). Tesla currently lists the PowerWall at $429/kWh, which is about half of Enphase' AC Battery, which comes in at $833/kWh, but PowerWall contains no inverter. The PowerWall solution might be cheaper if more than one PowerWall is attached to the StorEdge inverter.
Last edited by RegGuheert on Thu Feb 11, 2016 4:01 pm, edited 2 times in total.
RegGuheert
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Enphase Inverter Measured MTBF: M190, M215, M250, S280

Valdemar
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Re: Tesla Powerwall

Thu Feb 11, 2016 3:57 pm

Looks like the system is based on their existing inverter SE7600A-USS, which likely means those who already have it can just add missing components, mainly the battery, which doesn't necessarily mean there will be many takers.
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RegGuheert
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Re: Tesla Powerwall

Thu Feb 11, 2016 4:11 pm

Valdemar wrote:Looks like the system is based on their existing inverter SE7600A-USS, which likely means those who already have it can just add missing components, mainly the battery, which doesn't necessarily mean there will be many takers.
The existing inverter is SE7600A-US. The new inverter is SE7600A-USS.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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