Over the years I’ve enjoyed experimenting with new technologies as they appear. Which is appropriate for a futurist. This week we started another such pilot, and I wanted to blog about it.
We now have a Tesla PowerWall installed in our house.
Main unit on center-left. Inverter, control panel, etc. to left. Hestia the dog snouting around on the bottom.
A little context: my family are homesteaders in Vermont, our house up on the Green Mountains about half off the grid. We get water solely from our well, heat the house exclusively with firewood, raise plants and animals for some of our food, and so on. (Here’s our hibernating blog) (photographic evidence) Electrical power, though, is a serious problem. We’re dependent on a fragile series of above-ground cables running along our mountain and through woods. Each basic storm has the chance of knocking us off-line for hours or days. We’ve been eying generators for a while, but haven’t yet made the considerable investment in money (plus gas dependency and emitting plenty of carbon fumes).
Enter Green Mountain Power, our state’s electricity utility. They have a lot of experience dealing with outages – remember that this is a very rural, underpopulated, and not wealthy state. They decided to pilot the PowerWall to help homeowners deal with such outages experimenting with these. GMP actually got ahead of the curve, since the devices aren’t commercially available until next year, according to Wikipedia.
So they called us, having selected our home at random, and asked us if they could trial one with us. Being the ideal candidates (homesteaders, me a futurist and social media hound) we jumped at the chance. GMP hired a squad to install it this past weekend, and did the job heroically, fending off our dog’s confused attentions.
The inverter and friends, freshly arrived, unattached. That’s one of our three in-house woodstacks off to the left.
I think we’re the 3rd installation in the state of Vermont.
So, how does it work?
Inventor and Robert Heinlein novel reenactor Elon Musk describes is as being like a backup generator. I think of it as a mega-UPS unit, or, basically, a giant, rechargeable battery.
These PowerWalls are designed for solar. I really want to feed solar power to ours, but we can’t. Our land is thickly forested, so we’d need to bring down a *lot* of trees. We’re also partly in the shadow of the mountaintop, so receive less sun than we should.
One solution involved sticking panels on top of an elevated structure, which is susceptible to being knocked over by wind. (We could also put one on top of the house, in which case a strong wind might peel off part of the roof along with the PVs.
) So for now we feed the Wall with grid juice.
We tested it by turning off power to the entire house. All the lights and appliances besides the fridge and water pump went off, but the fridge, pump, and digital machines smoothly kept on trucking.
So far so good.
Some stats: the manual claims the Wall will give 3.3kW of power each day. That’s enough to power our refrigerator, water pump (as long as we don’t overdo it), and a bunch of electronic devices (laptops, desktop, routers). Maximum DC current: 9.5 A. So far it recharges very fast, as in filling up under one hour.
I’ll keep you all posted as we test it out through May weather. In the meantime, what else would you like to know?
“Inventor and Robert Heinlein novel reenactor Elon Musk” – I laughed out loud at that one. (PS check your spelling.)
What was involved in planning for the installation? Figuring out which circuits get juice and which don’t, I suppose, but if you have any stories to tell about that process I’d be interested.
(Gambier’s power grid has gotten a lot more reliable, and AEP is doing better line maintenance, since we moved here – but as a fellow well user, I am curious how long I could run the well pump and the fridge.)
Good question.
We had to figure out what devices to connect, and which to leave off.
That involved balancing power draw and importance to us.
(Spelling corrected. Still trying to figure out Mac autocorrect)
Have you considered wind power? Small turbines are out there and are popular on farms. Although it is also possible a good winter storm would take that down as well.
Considered and rejected. The Green Mountains, upon which we live, break up the big Canadian winds that come down from the north. We’re also too far from the Atlantic to get those winds, usually.
3.3kW peak or continuous? And is it the 7kWh or 10kWh version?
And how long do you get that power? 3.3 kwh total (over any discharge time) or …?
Btw, my vision for this kind of thing is that eventually it could be like propane tanks – drop off your empty at the solar station and pick up a full one. 🙂
I think it’s 3.3 continuous, but will await practical testing.
Don’t know the duration yet, Emily.
Emily, that seems like a really neat idea for the developing world or new settlements. I’m not sure it makes a ton of sense for communities which already have electrical grids, since recharging can be accomplished over the grid. As an emergency service, though, it would be hugely helpful – if batteries were as easy to swap out as propane tanks, exchange locations could be set up as part of the response to a major storm or other grid-damaging event.
So the large box is the battery
Medium size is the inverter/rectifier
The one with the red triangle is the comnection box
What is the one below your breaker panel?
I think it’s a junction box, but am not sure.
That’s the autotransformer. The SolarEdge inverter normally interconnects to the grid and outputs at 240 Vac nominal. But your loads run on 120/240. The autotransformer is what makes it possible to supply 120 volts to backup loads.
Actually, I go that backwards. The box with the red triangle is the system energy meter. The all white box is the autotransformer.
Simplified system schematic is available here:
http://www.solaredge.us/files/pdfs/products/StorEdge/se_storedge_inverter_datasheet_na.pdf
The devices you have connected are those connected to the inverter I assume (a wiring disgram would be nice)? Hence are they connected to their normal AC outlet and this circuits rooted back to the the onverter which switches aotomaticalky when grid power is disrupted?
We are looking at putting two Powerwalks in our new house in Charlottesville that will be driven by solar roof panels.
The last question I have this what is the recommended discharge cycle to maintain maximum battery health and get as long a lifespan from it as possible?
We’re looking into the wiring diagram.
Yes, all connected to inverter.
Great question about discharge. Don’t know yet. Might be something we have to test in practice.
On the solar, is there not any place around that has sun? For example, could Green Mountain Power have consolidated solar locations that would directly recharge several Powerwalls?
Oh sure, especially down in the valley. Some folks in our town have solar, too.
We just lucked out.
That is super-cool. The Wall is calling to the battery fetish I’ve developed since Superstorm Sandy.
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This may be a useful resource because it shows a wiring diagram
http://www.jlconline.com/how-to/electrical/tesla-powerwall-not-just-for-solar_o