Comment by roel_v | Hacker News Reader

Comment by roel_v | Hacker News Reader

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" 4kW seems to be the maximum potential drain from the battery. That wouldn't power an oven… let alone anything else at the same time."

4kW is enough to power an entire home continuously, without thinking about energy use, even a large one with a home office with several people working in it + washing machine + oven + electrical stove at the same time. I have the data to prove it, too - 10 second interval power consumption logs for the last 4 months for my house/office, and I never had a load of more than 3.5kW. To be fair, this is all with modern, top of the line appliances, so yes that 199$ no-brand Chinese oven will probably draw a lot more power, but still.

Worst case, you'd need a second 'peak power' supply, which could provide e.g. 6 or 8 kw for 10 mins max, maybe using some sort of XXL capacitor. I don't know about the EE side of this, or whether such a thing exists already, just saying - 4kW is perfectly feasible and even heavy users would maybe need just a little bit more.

(of course this also assumes you have a better quality house than the standard American cardboard 'house' in which you need A/C running 24/7 just to not die in summer).

> I never had a load of more than 3.5kW

Different issues over the pond, my kettle can draw 3kW :)

Since so many of my countryfolk have something similar, this actually causes our energy production quite severe issues when popular TV shows finish. Often a 200-400 MW spike but at the end of the 1990 world cup semi final penalty shootout against Germany, there was a spike of 2.8GW.

An interesting example of some of the problems that could be solved at least to a large degree by local batteries.

http://en.wikipedia.org/wiki/TV_pickup

I wonder if this will move more from ones in the home to ones placed by the national grid. While every house on my road might have one, and it's not enough to cover the load from a kettle, one for the whole street could cover it just fine as long as we don't boil them at an identical time (the worst case there is basically equivalent to the normal case for individual batteries).

"Different issues over the pond"

Well depending on which pond you're talking about, we're actually on the same side :)

" my kettle can draw 3kW :)"

True, you have some special circumstances in your country. You'd still be better off with a boiling water tap, the cost of which (even when amortized over only a few years) is the same as using a kettle (when accounting for all costs - lost energy, water, installation costs etc). So for somebody implementing this in the UK, they'd have to budget for an additional 1500 pound up front cost - which has the potential to turn into a cost saver after 5-10 years (probably closer to 5, depending on how fast energy costs will rise - which I think is fair to expect will be at a higher-than-linear rate).

> my kettle can draw 3kW

Pretty awesome for when you want that coffee ready in like 30 seconds flat, huh?

A 2 or 3 kW kettle is pretty common in the UK. We enjoy a good queue, but not to have to wait for a cuppa.

My air conditioner is 12 kW. No chance.

If your air conditioner actually draws 52 amps at 230 volts (or 110 @ 110 if you're in the US), you must be air conditioning a gym hall with a black, tin roof somewhere in a desert.

But you're probably not, and that was my whole point - my stove top is rated at 10kW, too, yet even when using alongside all other appliances in my house I have never gone above 4kW actual use. Actual need != summing all the nominal maximum rated loads of all appliances. In other words, it's not because your AC is rated 12kW, that you'd need 3 of these battery packs just for the AC. You might need 2, or maybe 3, I'm not saying that 2 (or 4) kW is enough always, everywhere for everybody - but there is no 'normal' (middle to upper middle class) home anywhere that would need 5 or 10 of these units, as is suggested at various places in this thread.

To be honest, I don't know. It has 12kw on the outside. It's a DC inverter ducted system. I had to get the wiring to the house upgraded with 3 phase when it was put in. It doesn't use 3 phase but one of the phases is dedicated to the aircon. My electricity bill in summer is 20% higher.

Is that the output or the input? If it's the output (i.e. the amount of heat coming out of the condenser outside your house), the input might be only 5kW or even less.

(Probably some jackass is going to downvote me because they think this violates conservation of energy, but no — those 12kW coming out of the heat exchanger include the 5kW of electrical energy that went in, plus another 7kW of heat that’s being extracted from the air being conditioned; and if you were to try to run a heat engine off that 7kW of heat difference, you wouldn't be able to recover the original 5kW. All perfectly thermodynamically copacetic.)

Not a chance without an investment in energy use optimisation and/or a change of habits. 12kW is a _lot_ of power.

Thank you for mentioning this. Too many people in this thread forget that not everyone lives in a temperate coastal area.

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