On Monday 16 April 2018 06:29:12 Erik Christiansen wrote: > On 15.04.18 19:40, Gene Heskett wrote: > > Greetings all; > > > > I see Banggood has a 500 watt wind thingy for under $200 that net > > folks are calling professional grade stuff. I am looking to put up > > an anerometer to record the wind speeds, one of those 3 cups designs > > that isn't direction sensitive, and one of these card computers to > > log what it sees so as to get an idea who many of these 500 watt > > things I'd need to keep a bank of truck batteries topped up while > > running the house, including the AC. > > > > Has anyone else walked this trail, or do I have to start with a > > machete? > > Gene, my off-grid build has so far only passed planning approval, and > I've just embarked on building approval. It is based on wood-stove > heating plus 7¹ kW of PV panels on a 30° roof, not quite matching my > 38° south latitude. Battery requirements are reduced by trying to use > the aircon(s) only/mostly when it's hot & sunny, and using a heat pump > for non-winter water heating, as that uses only a quarter of the power > of direct water heating, taking the other 3/4 of the energy from the > air. The secret is to run dishwasher, washing machine, lathe, milling > machine, anything you can in the middle of the day, powered directly > from the PV array, not the battery.
> In winter, water heating is by an in-flue SS double-skinned tubular > unit. (Hot water system vented, so it's not a pressure vessel.) Fuel > supplied by 2 sq. km. of forest on the property. I think grandpa's hot water was pressurized, it was a copper coil in the firebox of grandma's wood fired Monarch cookstove. The water was pumped up to a water tanks of 5k gallons on a 25 foot tower so the gravity fed pressure wasn't very high. Fed by several hundred acres of riverbottom forest. Ice from the coon river was covered with sawdust from his sawmill that made all the building materials needed although the ice house itself was hollow tile. Several tons of river ice was cut and hauled up to the ice house in Jan/Feb, and he had ice for the icebox all summer and into a foot of snow on the ground in late fall. > Batteries: Even deep-cycle LA are not worth the biscuit. LiFePO4 are > better than plain Li-Ion for fixed installation, being _much_ less > flammable, and more robust. The zinc-bromide flow battery from Redflow > is more robust still. Not only can it be left for years on a shelf > either charged or 100% dead flat, but it needs to to be run dead flat > every few weeks to keep it young. It is a SS box on top of a 190 L > tank full of water & chemicals, so it'll tend to put a fire out if > that melts the tank. A vent tube to outdoors is advised, as in > extremis there could be a smell of bromine, possibly. > > It was originally sold as the ZBM2 for about $7k for a 10 kWh unit > with inbuilt long-life BLDC pumps and controller. Now it comes in a > consumer-friendly lockable outdoors enclosure and what-not for around > $12k installed. I've been umming and aahing about a second one for > long dark winter weeks, but I live alone, and it's cheaper by several > country miles to just arc up the petrol generator the year that > happens. Or fire up the 20kw nat gas fed standby out back of my garage/shop. > Its one weakness is that you can only charge it at 42A (~ 2.5 kW), > which isn't very compatible with a DC-couples system, i.e. > PV Array -> MPPT charger -> Battery -> Battery inverter -> 220v > To fully utilise the array output, we need to swallow up to 7 kW. The > Redflow is better suited to an AC-coupled system: > > PV Array -> Solar/Battery inverter -> 220v -> AC charger -> Battery > \_______________________________________/ > > Then you can use much of the 7 kW directly, storing only what's not > used. Which makes way more sense. > There are though two units (with small losses) between array and > battery. But most systems on the market are built this way. > > There are some saltwater batteries on the market, but they are > enormous, heavy, and have an even lower permissible charge rate, on my > reading of the datasheet. They could also be used as a heat sink, for night heating I'd assume. > OK, supercapacitors are coming, and they will annihilate the chemical > batteries, but the first ones are not as good as the ones still in the > labs, so I'll be reevaluating when I have a roof up, towards the end > of the year. > > Wind? The consumer generators provide piffling amounts of power, are > disproportionately expensive compared to solar, and die in the arse as > there isn't enough wind enough of the time. That fusion reactor in the > sky still delivers a useful bit even in light overcast, and who needs > to run the washing machine when the weather's no good for hanging the > washing out? > > In my new build, lighting will all be LED, run from DC. The inverter > won't need to be running for that. The plan is to make some of the > light fittings. I need something to build in the two workshops which > make up 1/3 of the build. (Also have to find time to finish the design > of a networkable LED dimmer (3 channel), and send off for some boards > to be made. The firmware needs a fair bit of work too. The light > switches are to be neat clicky pushbuttons. The last build, 30 years > ago, was as owner-builder. This time I'm paying a builder, so I _hope_ > to find time for the fiddly bits, despite having to prepare the old > build for sale.) > > I'm also looking at a camping fridge with phase-change material inside > the insulation. That only needs power for a couple of hours in the > morning, and again in the afternoon, so does not load the batteries if > there's sun. > > Cooking is microwave and induction hotplate - not a complete cooktop. > I get out of bed late enough so that will rarely draw on the > batteries. > > Double glazing reduces heat loss and gain, and might help if you have > to run the aircon after sunset. An MPPT charger or solar inverter > which takes two array strings allows you to put one of them on a > westerly roof, to catch more late afternoon power to help there. > > Hope there's something useful in these muddy footprints from where I'm > headed. There's doubtless stuff I've forgotten, but that's what's top > of mind ATM. > > ¹ Some reckon 12 kW is the go for off-grid, but they usually have a > wife and kids. I could go to 9 kW with 330 W panels instead of 250 W. > > Erik > (Headed out to the farm on Wednesday, to push this thing along a > little bit. Have to have a chat with the building surveyor.) > Thanks Erik. Some of the above I've not heard about till now, like the salt water battery. And its sounding like costs are coming down, just not fast enough to do me a lot of good. -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
