A lot of folk are putting in solar electricity with batteries, but the inverters shut down when there's no grid power, to avoid electrocuting a linesman. So you don't get a household UPS.
But why can't they just sense the mains power (perhaps during one skipped half-cycle per second, dithered) and just not send power out when the line is dead? It seems you should be able to get safety certification for such a system. Sure, if you have multiple such systems on the same segment, they'd see each other, but some signalling standard would take care of that.
It seems weird that folk invest in big batteries but can't use them without grid power.
That makes no sense at all. You ust be talking about a low cost option trying to save the expense of an automatic transfer switch. So selling price is cheap but the actual operation is disappointing. Auto transfer switches are not cheap.
I have a transfer switch consisting of a 50A breaker for the gennie, a
150A main breaker for the house, and a sliding aluminum panel with slots that prevent both being closed at once. 'Tain't rocket science.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
Your call. Our outages are very infrequent but occasionally last long enough to justify owning a gasoline generator. (We live in a very nice leafy suburb with overhead wires.)
Last winter we had one that was by far the longest yet--over a week. I got on the Con Edison webpage the first day--they were listing over 100k outages--and calculated how long it was going to be, based on d(outages)/dt. It was obviously going to be several days. There were no gennies to be had locally by then, so I ordered one online and lined up the electrician to put in the transfer switch and outside gennie attachment.
We had power 3-4 days sooner than our neighbours, and are prepared for next time.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
These sites don't distinguish between inverters that are for solar-panel stacks with from 300 to700 Vdc, and inverters that work from battery-backup systems, to provide AC line power, and let the standard PV install with its oen AC-line inverter, think it's driving the grid, whereas it's actually driving the house plus battery backup system. Automatic transfer.
"The grid" doesn't sell power to you or buy power from you. The local util ity sells and buys power to/from you. Here, as in many states, the utility must pay you the same rate you pay it. In fact, all they do it subtract t he power you provide to them from the power you take from them before addin g up the bill.
That is legislated for the purpose of promoting alternative energy producti on at home, so it may not last.
ates, the utility must pay you the same rate you pay it. In fact, all they do it subtract the power you provide to them from the power you take from them before adding up the bill.
tion at home, so it may not last.
International habits vary.
The retail price of electricity in NSW is $A0.33 per kWhr, and the feed-in tariff is now $A0.20 per kWhr.
It used to be higher, but rooftop solar is getting popular in Australia.
People in places where there's less sunshine and more cloud may still be be ing sucked in by unsustainable subsidies.
At least in Australia you get enough sunshine for it to be properly worthwhile. The UK has utterly weird rules for solar PV FIT where you are assumed to deliver half of whatever you generate with a domestic PV setup to the grid no matter what you actually do with it.
Most people have a diverter that dumps all of their daytime generated PV electricity into their hot water tank immersion heater if they are not at home to use it. It is a waste of high grade electrical power from PV turned immediately back into heat. A very few have battery storage to save some of it for night time (typically 4-12kWh capacity).
The whole thing is madness since solar hot water panels have no subsidy and would be intrinsically far better at the job of making hot water.
I have seen solar panels installed on "green" roofs shaded by trees in a woodland setting which stand no chance at all of working properly.
Presumably you could if you isolated the system from the grid and ran a local generator set to provide a seed supply for it to sync to. Although the poor variability of its frequency might be a problem.
Is that sort of mechanical interlock examined and approved by the power company to make sure that it is intrinsically safe?
I rely on running an extension cable from my rather basic generator set to the handful of appliances that need power in an extended power cut. Basically fridge, freezer and CH pump.
I was away for the last serious power cut in my village when the bulk milk tanker slipped on black ice and took out a power line pole. Usually powercuts are storm related and last a day or two here so being able to run heating and keep the freezer cold are the two main priorities.
It doesn't happen often enough to be worthwhile investing in a more complex solution. Such failures are once every three or four years. There is the odd summer shutdown when they prune the trees close to the mains distribution wires but they are daytime and scheduled in advance.
Especially after the first branch blows down onto them.
Cheers
Phil Hobbs
>
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
ility sells and buys power to/from you. Here, as in many states, the utili ty must pay you the same rate you pay it. In fact, all they do it subtract the power you provide to them from the power you take from them before add ing up the bill.
tion at home, so it may not last.
That may be in your state but not mine. First off, only 1% of the customer base is allowed to sell power to the grid, you need a license. Then the rei mbursement is what they call the "cost avoidance" rate, which runs slightly less than half of what the utility charges you. If the government wants to promote renewable energy, they need to force the big utilities to make the conversion. Their ratepayers foot the bill, so i t costs them nothing. And the rate increase is WAY WAY less than an install on their rooftop. Then a DOE survey from a few years back found that less than 10% of U.S. ho mes are even suitable for solar for one reason or another, things like roof too small, bad orientation, shading by trees or other structures, resident density, bad geography- not enough sun, a bunch of stuff.
The big problem in Sydney is hail damage. Not many solar panels withstand cricket-ball sized hailstones. You have to be unlucky to get those, but can still expect golf-ball sized hail with reasonably high probability in a ten-year period - and I'm simply unwilling to install solar with the expectation of less than ten year life.
When I last looked into there were two disparate species:
a) Grid-Tie units. These are designed to source power back into the grid, i.e. spin the meter backwards. I think of these as current sources; dependent on the near-zero impedance of the grid to sink its sync-ed output.
b) Battery backup units.
a) relies on the grid for 60 Hz to sync to; for safety reasons and that they shut down, period, when the grid fails.
A big difference is panel output voltage: a) tends to use series-connected panel arrays with the output in the 600VDC range while b) units tend to be just above battery bank voltage,
24/48V.
There were some outliers that did both; and Sunny Boy had some scheme that linked their separate grid tie & battery backup units.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
Similar experience here (UK suburban area with the typical underground feed from a local substation). This happened just a year or three after moving into this 6 bedroom semi-detached Victorian house some 35 years ago when water got into a joint, leaving us without power for about 4 hours.
As luck would have it, I'd acquired a 2nd hand 300W/450VA Emerson UPS less than a year before to protect against the almost improbable unplanned loss of power taking my computer down. A purchasing choice, it has to be admitted, made on the basis that I'd be the only one in the neighbourhood still able to carry on using my computer, with a smug smile on my face, whilst all around would be left in the dark staring at a blank screen with the prospect of having to run the CHKDSK routine when power was eventually restored (I must have been one of the few who were looking forward to a power cut!). :-)
As luck would have it, I got my wish soon enough. It happened on an evening when I was just about to head out to my local radio ham club meeting. After shutting the computer down, I moved the UPS to the half landing along with a floor standing lamp with a Philips SL13 so as to provide lighting for the hallway and stairs for some basic measure of safety. I couldn't shut the UPS off since it didn't have a "Black Start" option and this seemed the best use for it.
By the time I returned from my club meet about 4 hours later, power had only just been restored and the UPS had kept the light burning right through the whole outage which turned out to be handy since the children had completed their homework assignments via its light into the half landing toilet where they'd put the lavatory seat lid to good use as a 'chair' whilst writing up their homework assignments.
If it hadn't been for that rare demonstration of the benefit of UPSes, I probably wouldn't have built up such a large collection of UPSes over the following decades. At one point, I had as many as 4 UPSes in active use, protecting the server, my main desktop PC and PCs under repair on my workbench and the 'family use PC' in the front parlour.
After some three decades of reliable mains supply, marred only by the odd one or two second drop out event and a few weeks period in the run up to one Christmas when we started seeing shallow brown outs which suggested contactor issues with the voltage regulator gear in our local sub-station, I finally decided to retire the less vital UPSes as their batteries wore out.
Even the main 2KVA UPS I'd setup in the basement to power protected mains sockets landed up being decommissioned as I gave up trying to satisfy its seemingly voracious appetite for consuming 48 volt battery packs, leaving just the single BackUPS500 to protect the NAS box with its single 12v 7AH SLA battery pack to power its 'quasi sine wave inverter'.
This one did have the virtue of all such 'quasi sine wave inverter' types of high efficiency and low maintenance consumption and a decent battery service life so was easy enough to justify as a cost effective protective measure.
However, in view of the extremely tight margins during winter demands on the UK national grid that have arisen out of government mismanagement of the situation over the past two or three decades and the ever looming risk of rolling blackouts in the event of another severe winter, I've decided to recommission the basement SmartUPS2000 the cheapest way possible (using a set of 7AH SLAs where a set of 17 or 18 AH batteries are normally specified), supplemented with a 1KW (1.2KW 30 seconds surge rating) inverter genset to uprate to a backup supply that can be refuelled with 4 or 5 hour's worth of autonomy per tank refill.
Ideally, I'd have preferred a 2KW continuously rated inverter genset for
local Lidl store last year made its purchase irresistable, even if it was only to prove a point that the inverter type genset was the only type that could be trusted not to overvolt from the slightest sniff of capacitive loading as its 2.8KVA genset predecessor some 5 or 6 years earlier had done when I'd made my first doomed attempt to overcome the limitations of a battery only extended autonomy setup.
The overvolting effect, common to all such "direct from the automatic voltage regulated alternator" gensets in the 1 to 30 KVA and above range is what put paid to that scheme. It turns out that the 'claims' made by the UPS manufacturers in regard of "Dirty Power" from emergency gensets is a load of bullshit. Plus or minus 3Hz from the genset? The UPSes cope with this problem with the greatest of ease. Harmonic distortion? No problem! Under or overvolting? Yes, of course but if the voltage variations aren't too severe, a decent line interactive UPS can buck or boost the supply to save burning up the battery reserve.
However, when the 9.4 microFarad's worth of input loading from the SmartUPS2000 is presented to the output of a 2.8KVA genset that only needs to see a mere 4.7 microFarad to send its output north of the 275v mark on a 230v setting, the UPS has no choice but to disconnect the supply and run its sine wave inverter off the battery, at which point, the generator stops seeing the 9.4 microFarad load and stops overvolting, causing the UPS to switch back to the 'incoming mains voltage' provided by the genset which then kicks off the next overvolting cycle.
Unless you (can?) select a conventional generator designed to overcome this capacitively induced overvolting effect, the only other option is the inverter genset where a three phase multipole PMG powers an inverter/ engine management module to provide clean sine wave power at 50 or 60 Hz that's not only immune to this overvolting effect but is also a damn sight purer than the badly distorted 50 or 60 Hz 'sine wave' power provide by the Power Supply Utilities.
The power rating, as I said before, is a little on the marginal side but, since upgrading almost all of my lighting to LED since my previous failed attempt at upgrading my backup plan, it turns out to be just enough to keep all of the lights on as well as power the more critical IT kit, the CH pump and the main TV set.
I did try out Aldi's more powerful 1.8KW rated Workzone inverter genset offering that became available a few months after purchasing the Lidl Parkside PGi1200 B2 genset but, after trying out three examples (optimist that I was), I gave up on these festering piles of utter s**te.
I do wonder how many (if any) of Aldi's customers accepted the piss poor voltage regulation, exacerbated by the effect of any sudden loading causing the engine to almost stall, as being normal for this type of genset? Hopefully, none. By comparison, the Parkside unit is a shining example of inverter genset perfection. The contrast between the two could hardly be greater.
Added to that was the fact that the Workzone genset had a combined fuel and ignition cut off and lacked the normal/eco-throttle switch meaning you couldn't run the carb float bowl dry to facilitate longer term storage as you could with the Parkside unit and you were forced to allow several minutes of warm up time before connecting a load unlike the Parkside which could be connected to its load straight after startup and then switched to eco-throttle mode after a couple of minutes warm up time.
Indeed, provided you didn't have any high current startup loads, you could start the Parkside unit whilst still connected to a load since it would delay enabling the inverter output for a couple of seconds after the engine had gotten up to speed (with the eco-throttle option disabled of course, until it had warmed up a couple of minutes later).
The only serious omission in both cases being the lack of a priming bulb to operate the engine vacuum driven fuel lift pump to prime the carb float chamber to both ease recoil rope starting and reduce the wear on the recoil starter rope itself. To this end, I'm in the middle of a project to recruit the PMG as a directly coupled starter motor by the addition of a bunch of electronics.
Initially, I had hoped to be able to use sensorless commutation with an add on BLDC controller module but it turns out, like the needs of the BLDC electric drill and chainsaw, "sensorless" just can't cut the mustard and "locked to the rotor positional Hall Effect sensing" is mandatory for this type of mechanical loading. Sensorless operation might be fine for fans and quad-copter propeller BLDC motor drives but it's just not up to this job.
I got as far as proving the PMG would run as a motor using sensorless commutation but only when the spark plug was removed to lighten the load. as soon as I blocked the spark plug hole with my finger, the BLDC controller became confused and stalled. Clearly, my next step is to add a magnet to the end of the crankshaft and fit a pre-programmed Adapter Board for AS5047P module onto the crankcase mountings to sense the rotor position to an accuracy of a fraction of a degree by which to simulate the classic three hall sensor signals to drive the HE inputs on my BLDC controller.
Whilst such "Gross Mechanical Modification" goes against my original idea of an "electronic only modification", it's still a far cry from the rather quaint practice of fitting a starter ring gear and DC starter motor with bendix and starter solenoid option of old and still simpler than trying to modify the PMG itself by fitting and carefully aligning three separate Hall sensors.
At the moment, I've yet to determine how many pole pairs are used by this particular PMG. Typically, pole pair counts for these machines are either 6 or 7 (18 or 21 salient pole windings on the stator). As soon as I know this, I'll be able to specify the Hall Effect emulation option when I purchase the AS5047P module (I can always manually align the module to the engine post programming in this case).
Alternatively, if the programming software is provided free (I can no longer recall the details of this option), I could bolt it on and then program it afterwards. I vaguely recall that the control program can be held external to the device and fine tuned before committing it to the internal prom.
Whatever my options are, I should be able upgrade the PMG to a Hall Effect sensored brushless DC motor to endow the inverter genset with an electric starter option. I just need to take another look at the programming options for this rotary encoder module before making any further decisions on how to continue with my project.
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