Redox flow batteries might be a cheaper alternative. It might be likely not all
available charging cycles are used for a long lasting battery. 20 cent per kWh
hour, price for electricity I found in USA is in the range 7 - 23 cents per
kWh, with an array on roof storage cost might be if you are unlucky storage
come cost close to bying electricity. I have done calculations there storage
cost for generated energy where higher than buying new electricity.
On Tue, 14 May 2019 10:36:42 -0700
Chris Albertson wrote:
> If you are building a battery-based power system and space and weight are
> not issues then what you should care about is the "total watt-hours per
> dollar".
>
> Here is an example,... You have a 100 amp-hour lead-acid battery at 12
> volts. If it is lead-acid then you can only discharge to 50% if you want a
> reasonable lifetime.If it is a cheap batery it might last only 100
> charge cycles. so 50% x 100 cycles x 100 amp-hours x 12 volts is 60 KWH.
>The cheap battery might cost $100 to you pay $1.60 per KHW for battery
> power based on the replacement cost of the battery. You can buy a higher
> quality battery for more money but your cost is going to be between $1 and
> $2. per KWH
>
> So the cost of the battery power is 4 to 8 times high than the cost of
> power from the utility company.
>
> But what if you buy higher quality batteries?
>
> A Tesla "Power Wall" cost $6,800 (They used to be $10K) it is a 13 KW
> capacity and is good for more than 3,000 charge cycles and is actually
> warrantied for 10 years. It is maintenance free for 10 years. Use with
> a waentry you have an incentive to use it for the full 3,650 cycles.
> Lets assume you only cycle it 3,000 times. That is under 20 cets per
> KHW for battery power. It is dramtically cheaper then lead acid.
>
> This is why Tesla is selling b'zillions fo power wall systems. If you do
> care about space, these Power Wall units cn be mounted to an exterior wall
> and actually look attractive.
>
>
>
>
>
>
> On Tue, May 14, 2019 at 9:32 AM Dave Cole wrote:
>
> > I've been planning to put up an array on my roof. But I have plenty of
> > space so I may do a ground level install.
> > It would be a lot easier to maintain.
> >
> > FLA batteries seem to be the general recommendation for a constant use
> > residential install.
> >
> > I've had chargers trash batteries when they failed. I sure wouldn't
> > want that to happen to $10K worth of Lithium batteries!
> >
> > Weight isn't an issue.
> >
> > Dave
> >
> >
> >
> > On 5/9/2019 10:37 PM, Erik Christiansen wrote:
> > > On 09.05.19 10:24, Dave Cole wrote:
> > >> Erik,
> > >>
> > >> Do you have a blog going on your build?
> > >
> > > Now that's an idea. All I've started is the seeds of an article for
> > > "Owner Builder" magazine - the editor was interested when we last spoke.
> > >
> > >> I'd be very interested in your solar and battery setup for your off-grid
> > >> home.
> > > The existing home, from the 1950's & extended, only has a little 2 kW
> > > petrol generator. The new roof which will carry the solar arrays goes up
> > > in June, if the framing carpenters turn up on time. (Just off the phone
> > > to 'em half an hour ago.) There's 6 or 7 kW of equator-facing panels,
> > > but the west-facing hipped roof can only take 9 panels, so only 2.5 kW
> > > or so - but still enough to keep pace with a modest aircon.
> > >
> > > The best trick for allowing high power consumption straight from the
> > > arrays, yet limiting battery charge rate to permissible maximum, is to
> > > use a hybrid inverter - they're beginning to become more available now.
> > > The Redflow ZnBr battery has a limited max charge rate (44A), and pretty
> > > much any other does too, e.g. 20A/100AH of capacity for LiFePO4. The
> > hybrid
> > > inverter looks after that while delivering to load first.
> > >
> > > I like the Redflow, as it's a long-life unit, unkillable by 100%
> > > discharge. It does though need that once a fortnight to regenerate, so
> > > it can be handy to have another battery. For off-grid, just one 10 kWh
> > > battery is maybe enough for one occupant, but a second is great for
> > > visitors from the city. But the reflow is about A$14k (US$10k), so I've
> > > even been looking at old technology like NiFe. They're also robust, but
> > > can drink a lot of distilled water, emit quite a bit of hydrogen, and
> > > put out a bit of mist. About 80% energy recovery is common for a lot of
> > > battery chemistries, these included. Li-Ion, or better LiFePO4, are
> > > better efficiency-wise, but cycle life on deep discharge is less. Do
> > > your machining in sunlight, and only run lights, computers, tv, and a
> > > microwaved egg sanger at night, then they'll do well enough, I reckon -
> > > certainly long enough for a better technology to reach a better price.
> > >
> > > We know from laptops that Li-Ion loses capacity with age. The ZnBr unit
> > > is claimed to retain
