Took our first steps toward energy independence today with a Tesla Powerwall.
I'm observing Powerwalls too. waiting for solar but have already prepared most cabling. Natural gas to be replaced with heatpump too.
If a full Powerwall doesn't get you through the night you need to seriously look at your "base load".
I have seen radio's pulling 18W in standby (157 kWh/year) and microwaves using 8W to show the (wrong) time, Desktops using > 5W when off and floor heating pumps drawing 95W 24/7, even when not used in summer.
At night I have:
12W 12V outdoor LED lighting (9 x 1.2W running from a single high-efficiency adapter) [edit: corrected]
4W internet modem/wifi (with all status lights disabled)
18W freezer, 75W with about 25% cycle time.
10W fridge, 65W with about 15% cycle time.
8W standby central heater (I turn this off in the summer unless I need warm tap water)
5W phone charger (10W for half a night)
Total: 57W night-time usage.
a single 13.5 kWh Powerwall would last a me a
236 hour night.
Oh wow. We oscillate between 200 and 500W night time usage. Never go below 200W. Much of it is various security systems but I am curious as to what our fridges are consuming. The beer fridge is quite old and might be an energy hog. You have got me interested. I will run an audit on what everything is consuming.
So I wasn't sure if we would make it through the night but we did, including running a load of clothes through a washer and dryer. Now the solar is starting to kick in again and we are on 17% on the battery so we shouldn't need to draw from the grid at today. I'm guessing the battery would be over 40% if we hadn't done the clothes.
Warm climate here so heating isn't an issue. We run a heat pump maybe five days a year. AC is a challenge in summer but the solar panels are screaming through production in the full sun so we are heavily exporting even with the AC on full. AC at night time may require some balancing to avoid having to import.
It’s a good point. It’s currently attached to the outside of house and has cameras on it, not that that is likely to help.
Safety comes primary from a good battery monitoring system, and secondary from how the cells are packaged. A shorted cell should heat up but heat transfer to the next cell(s) should be slow enough so the whole pack can't do a cascading runaway. Powerwall should vent some hot gasses but nothing more. Mine will be indoor and I plan to not store very flammable things like cardboard/paper right next to it. It's
not a Chinese pouch cell, with just a thermal fuse, shrink-wrap "shielding", and very limited monitoring of charging and discharging conditions.
This safety talk is good. I decided to put a smoke detector from the hardware store above the Powerwall yesterday. Then my wife pointed out that the smoke detectors we have inside the house are all old and aren't compliant with current standards. They are also hardwired in. So we will get in an electrician to go through the house and update everything, including appropriate monitoring external to the battery pack.
Reserve power is a very nice thing for a house, not sure if you need a whole powerwall though. I've been running a power station in an outside shed on my property for about 20 years now, the core of it is 4 150ah VRLA (Valve regulated lead acid) batteries with a 1kw 24 volt inverter and 1kw of solar panels. About 5-6kw of power, 1kw peak draw, a 10 year life span on the batteries, and they will never catch fire..
In the event of a power failure I can switch to the shed manually for the fridge (300w, 25% duty cycle), a few lights, and most importantly cell phone and internet service (another 20-30 watts) and a coffee maker (70w for a few minutes). In a multi-day power outage the priority is keeping the fridge running and having fresh coffee. Can also run a smaller microwave oven if I need to warm some food up.
Solar panels can top off about 4kw of power a day, giving me around 9-10kw of power. With 2kw for the fridge this leaves me a fair bit of extra power for incidentals or a day or two of rain. Longest I have run it was 3 days when power really went out and it was a life saver.
Not too complex, worth it.
Neat. You are a solar battery pioneer !
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