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 <albertson.ch...@gmail.com> 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 <linuxcncro...@gmail.com> 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 capacity, just losing efficiency. If a few (cheap) > > > extra panels are put in the array(s), then that's pretty much covered. > > > > > > One thing - the hybrid inverter should have two MPPT string inputs - one > > > for each PV array, as their voltage at max power will never be equal, > > > given widely divergent orientation. > > > > > >> You must have a substantial setup to be able to run your AC off your > > battery > > >> bank. > > > I'm hoping to be able to get the roof up in time to qualify for a > > > current A$5k government rebate on batteries. Systems with only 6.3 kWh > > > battery capacity are selling well here for on-grid customers. I'd like > > > twice that, as without that, running the mill for hours after half a week > > > of overcast winter days could mean arcing the generator up for a charging > > > burst. But a litre of petrol now and then is a darn sight cheaper than a > > > big battery. > > > > > >> What do you do for domestic water? A deep well? > > > For 55 years it's just been rainwater tanks. I'll be putting in another > > > 90,000 litres of tanks, to catch it when it does come. There'll be > > > nearly 400 m² of roof all up. (But yes, years ago in a big drought it > > > really was bathe the baby in a bucket of water, use that to wash her > > > clothes, then wash the lino floor with it, then put it on the few garden > > > plants you could keep going.) The concern is that a tight rain deficit > > > might be shaping up to be the new norm for SE Australia, not improving > > > at all while we go from the current 1°C warming, through 1.5°C maybe as > > > early as 2030, to 2°C a bit later. (Accelerated warming at the poles > > > does not bear looking at, unless you've had a stiff drink first.) > > > > > > The neighbour had a drill rig in before easter, to drill for stock > > > water. It was expected around 70 feet down. I haven't heard the results. > > > That's a finite resource though, only buying limited time. Slabs of > > > India is hundreds of feet down now, and heading for a brick wall. More > > > roof, more tanks, and live on what precipitates is more viable for > > > longer. > > > > > > Erik > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
