Tesla Energy • Hacker News Board

Re: Tesla Energy

#391

Post by roel_v » Fri, May 01, 2015, 3:05 PM UTC

msandford wrote: post #287

roel_v wrote: post #200

Earlier quoted context omitted.

"and can only provide 2kW output." only 2kW? 2kW is enough to power any residential, single-family house for 95-98% of the time; you only need (a little bit) more than that at very short (few minutes) peak intervals - when heating up an oven, or some cycles of doing laundry. A second unit would provide that headroom, and otherwise (when the extra $5k for a second unit is prohibitive) you could still draw from the gri…

> only 2kW? 2kW is enough to power any residential, single-family house for 95-98% of the time You obviously don't live where it's hot. I live in Houston, TX and while I rarely run the A/C right now, in another month it's going to run on average 15 minutes per hour, every hour, for 3-4 months straight. Highs in the low 90s to high 100s and lows in the 80s (F). I have 2.5 tons of A/C which is pretty moderate. The cond…

I guess that my phrasing of "any residential house" is a bit unfortunate, and that 'the majority of all residential houses' would have been better, but that doesn't take away from the fact that with one extra of these units + 10k Wp of solar panels, you could power your AC's with power to spare to be stored in the battery pack, which you can then use to power the AC at night. Many people use AC's as a counterpoint to 2kW battery packs, whereas actually it's one of the more appropriate cases to use solar panels combined with (relatively) cheap local storage for nighttime consumption!

How much is your power bill in summer? Must be $300+, going on 500 during the hottest months? At that rate, you'll make back the $20k + $10k that 10k Wp + 2 of these batteries would cost you in what, 5 to 7 years? Add financing costs and you'll be at breakeven in 10 years, not counting possible government grants.

Re: Tesla Energy

#392

Post by ccalvert » Fri, May 01, 2015, 3:08 PM UTC

psychometry wrote: post #291

watty wrote: post #276

Earlier quoted context omitted.

I don't see how it's immediately beneficial for just about everyone. I currently have a flat rate for kWh and no solar panel... and moving soon. It's not worth the $. In 6 months I'll be renting for a year, still not beneficial. Perhaps in a couple years I can purchase solar, a battery, and an energy system that can automate some demand shedding but we're talking about 1%ers here. In fact, I'd say it's only immediate…

As someone who rents an apartment with no garage and has a traditional gas-powered car, I can echo your sentiment and claim that Tesla has had zero impact on my life and that this announcement doesn't change that. I sincerely hope that Tesla's many innovative business efforts improve society in some major way, but right now they're still just a high-end automative company that's exploring the renewable energy space.…

Renters may not have direct benefits, but if the product works, they could have indirect benefits. For instance:

Assuming someone rents, and has to pay the monthly energy bill, wouldn't they prefer living in an apartment that had tools like this that lowered the monthly energy bill?

Assuming you rented an apartment, and either paid for the monthly energy bill, or wanted to make your property more appealing, wouldn't you want to install a product that lowered your costs?

Re: Tesla Energy

#393

Post by joezydeco » Fri, May 01, 2015, 3:10 PM UTC

toomuchtodo wrote: post #373

joezydeco wrote: post #290

Earlier quoted context omitted.

I've been on ComEd RRTP for 6 years now and I've been wanting a nicer way to shift load or arbitrage price drops. The Telsa device, as others have mentioned, seems like a rebranded solar storage device. I suppose the intelligence would be in the inverter/grid cutout mechanism anyway. This system would run my home for about 8 hours in the winter and 4 in the summer before emptying, so I would need a lot more smarts in…

> This system would run my home for about 8 hours in the winter and 4 in the summer before emptying, so I would need a lot more smarts in the box to try and anticipate price spikes without running out. Most new grid-tie inverters can be controlled from a computer either over IP or a serial interface; you could fairly trivially control the flow of power by polling your electric provider's website (I scrape the RRTP AP…

I don't have a lot of experience with those inverters. How many cycles do you drop when switching over?

My first idea was to create a system that watched the immediate price as well as the day ahead AND the weather forecast to try and predict the best time to stay off the grid, but that's a little too ambitious.

My current idea is to grab my 5-minute history over the last year or two and model it against a simple buy-low-sell-high threshold. It should at least tell me how much the system would save each month.

(BTW about your earlier post, even if supply is 1c/kWh, there's still the delivery charge and taxes. I think supply needs to drop to something like -3.5c/kWh before the juice is "free". It's happened only once or twice in my history with the system.).

Re: Tesla Energy

#394

Post by kenrikm » Fri, May 01, 2015, 3:14 PM UTC

lsaferite wrote: post #313

kenrikm wrote: post #68

Earlier quoted context omitted.

To put it in perspective: in Florida, in the summer, using a 4ton very old/inefficient AC in a 2000sqft house in 100 degree summer weather, electric oven, refrigerator, washer/dryer and all other household stuff. I would burn about 3kw / hr in the middle of the day. So in theory the 10kwh would power a extreme case like this for ~3hours, and 9 of them could do it for ~27hrs. So yes you could do everything you would n…

Interesting numbers if you contrast them to another comment on this article saying his A/C was 12kWH.

I'm not aware of any consumer level ACs that draw that kind of juice. Given 10¢/kwhr (for easy math) that would still cost $1.20/hr or ~$8xx in electricity per month just for the AC.

Re: Tesla Energy

#395

Post by danielweber » Fri, May 01, 2015, 3:14 PM UTC

jws wrote: post #386

danielweber wrote: post #375

Earlier quoted context omitted.

What if it's in the garage and someone hits it with the car and pierces the cells? I didn't see "insurance" anywhere on that Tesla page. Ideally my insurance company won't pitch a fit about about me installing this in my house, but will Tesla guarantee that?

Does your insurance company allow you to keep one liter of gasoline in your garage? It has the same energy content as the Powerwall, is insanely flammable, is frequently implicated is home fires, and regularly causes human deaths. (Ok, a burning lithium battery will release more energy than its storage capacity, but I'm not finding a nice reference, Tesla knows all about containing cells to prevent chain reactions, a…

Gas fumes are very flammable, but the gasoline itself will flow down and out of my garage, and the fire would be very easy to contain with a simple garden hose.

A gas can also will not light on fire just because it gets hit with a car. It would take malicious use of a gas can -- splashing it on a wall and then lighting it on fire -- to match the default configuration of a Powerwall.

Re: Tesla Energy

#396

Post by dragonwriter » Fri, May 01, 2015, 3:16 PM UTC

criley2 wrote: post #335

psychometry wrote: post #291

Earlier quoted context omitted.

As someone who rents an apartment with no garage and has a traditional gas-powered car, I can echo your sentiment and claim that Tesla has had zero impact on my life and that this announcement doesn't change that. I sincerely hope that Tesla's many innovative business efforts improve society in some major way, but right now they're still just a high-end automative company that's exploring the renewable energy space.…

>" but it's not like Elon Musk has saved the world just yet." "I choose to rent, I choose to have no property rights over the building I live in, I choose to be legally incapable of installing solar panels and batteries on a structure I don't own: Elon Musk has failed me" Come on now. You made your choice to not be a part of the greater community and culture of property owners. These options, they're available to own…

> Elon can never overcome your landlords property rights. Not now, not in 100 years.

With sufficient lobbying juice he could. I mean, the government has intervened in property rights in favor of renters and against property owners when it comes to antennae for certain kinds of data, there's no fundamental reason they couldn't for residential backup power systems. [0]

[0] https://www.fcc.gov/guides/installing-consumer-owned-antenna...

Re: Tesla Energy

#397

Post by TillE » Fri, May 01, 2015, 3:17 PM UTC

tootie wrote: post #305

colinsidoti wrote: post #51

One thing that might go overlooked: Load shifting could, in theory, lower electric bills such that there's ROI without solar panels. --- Edit for why: On-demand power is expensive. "Spinning up" additional power during the day is more expensive than having certain types of power generation running all the time. In theory, pumping power into a battery at night during non-peak hours will cost less than consuming direct…

Big cities are prone to brown outs on hot days in the summer due to air conditioners. The 2003 European heat wave killed thousands1. I could imagine mayors mandating use of this kind of technology in apartment buildings. Let them charge overnight to offset peak usage. You'd cover 100 or more people at a time. [1] https://en.wikipedia.org/wiki/2003_European_heat_wave

Normal homes in Europe simply do not have air conditioners, not even in southern Europe. So the electricity is irrelevant.

Re: Tesla Energy

#398

Post by jws » Fri, May 01, 2015, 3:18 PM UTC

danielweber wrote: post #395

jws wrote: post #386

Earlier quoted context omitted.

Does your insurance company allow you to keep one liter of gasoline in your garage? It has the same energy content as the Powerwall, is insanely flammable, is frequently implicated is home fires, and regularly causes human deaths. (Ok, a burning lithium battery will release more energy than its storage capacity, but I'm not finding a nice reference, Tesla knows all about containing cells to prevent chain reactions, a…

Gas fumes are very flammable, but the gasoline itself will flow down and out of my garage, and the fire would be very easy to contain with a simple garden hose. A gas can also will not light on fire just because it gets hit with a car. It would take malicious use of a gas can -- splashing it on a wall and then lighting it on fire -- to match the default configuration of a Powerwall.

Or a vapor reaching an open flame. Common source of human immolation.

Re: Tesla Energy

#399

Post by balabaster » Fri, May 01, 2015, 3:21 PM UTC

wiremine wrote: post #310

What I'd love to see is a ROI calculator that: * uses my zip code to figure out what my non-peak costs might be. * allows me to optionally calculate solar energy capture (so I can see what impact having solar would be, given the average sunny days in my area) * takes into account the wear and tear average cold weather would have on the lifetime of the batter and the payback period. For example, I live in Michigan, an…

What I'd like to see is an ability for me to provide a list of appliances that I tend to use in my house (makes/models) along with a "typical" use pattern like "washer, dryer, dishwasher, fridge, freezer, stove, 50" TV, 200W sound system and blu-ray player or cable box frequently get used at the same time" With a usage pattern like that, which of the two batteries would be most useful? would I need multiples wired in series or parallel? is that possible? how long would it last under a load like that? My target is for off-grid use, so ROI isn't as big a concern to me as longevity of power and charging requirements from off-grid power generation.

Re: Tesla Energy

#400

Post by fancyketchup » Fri, May 01, 2015, 3:21 PM UTC

krschultz wrote: post #377

hyperpape wrote: post #332

Earlier quoted context omitted.

One point is that if batteries in houses (or electric cars) become more common, there's more incentive for a utility to offer variable pricing, because more people can actually make use of it, letting the utility company get by with less peak capacity.

I agree in the long term (50 years) that is true, but in the medium term (15 years) solar + storage might be moving faster than utility companies want. If you built a power plant with a 40 year lifespan in the year 2000, you would not be happy if peak demand is lower than expected in 2025. I would not expect the utility companies to be allies in this transition period to clean energy. It requires major capital outlay…

That doesn't really make sense.

Electric utilities require capital investment proportional to peak usage, but only earn returns on average usage. This will only increase the ROIC of an electric utility by reducing the peak:average ratio.

Additionally, electric utilities are in a constant cycle of capacity upgrades to keep up with increasing demand. Customers adding distributed storage allows utilities to delay capital investment (which makes the company look better in the near-term).