Cutting your energy bill.??. Don't try this at home, kids.

The greenest watt is the one you don't have to create. Energy efficiency is the low hanging fruit of greening our homes. Ask your questions or post your energy efficiency tips in here!

Re: Cutting your energy bill.??. Don't try this at home, kids.

Postby gyro » Wed Apr 04, 2012 4:25 pm

ooosp my typo! "Card"
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Re: Cutting your energy bill.??. Don't try this at home, ki

Postby markhead » Sat Jan 18, 2014 9:25 am

---BEEN HAVING LOTS OF FUN LATELY---with my W7 TOMAHAWK 3000-9000 variant and after much testing have come to these conclusions. I only use it for 240 vac power-and have no need to bother with the charging side of it so my concerns are mainly with 240vac generation.
1. use of power saver system is a complete waste of time- system at idle uses 8 amps and hiccups if power saver is in use so better left off
2. DON'T ALLOW IT TO CONTROL ANY FUNCTION WHATEVER WITH REGARD TO BATTERIES- ITS JUST NOT GOOD ENOUGH TO DO THAT. And in any case, much better not to allow batteries to go below 12 volts for maximum battery life so a good controller to regulate power from solar/wind with adequate dumping capacity is essential. If going below 12 volts then increasing size of battery bank is essential until balance between use and charge is achieved. An excellent controller for this up to 60amp solar charging capacity is the Plasmatronics PL60 [UP TO APPROX 10 PANELS depending on size. I have been keeping my system to 12 volts and can cheerfully tell you that the PL60 cheerfully controls my smorgasbjord of different size/voltage panels very well and not only that will tell me exactly what charge is going in, what the load is and what level my soc is once the setup has been mastered and that weird menu is understood. An excellent design and made in Australia too and you can actually talk to the makers reps if you have a mind to. Manual is an easy download but not everything you need to know is in it I discovered.
3. To test whether W7 unit is capable of delivering stated output great way to do this is the electric kettle test- if you have one rated at 2200watts, that will be a reasonable heavy load and if W7 system is rated at 3000watts [such as mine] it should run that kettle with ease. Mine won't so is about to undergo a transformer replacement I suspect since current draw was extremely high during the test I made yesterday which ran for 30 secs until the unit shut itself down.Alarm glowed but everything on control board idiot lights showed everything ok. Positive battery feed became too hot to touch so current is going somewhere and not into 240vac. W7 ran hot when I got it so got in touch with seller at that time but cooled down after a week or so but fitted a thermocouple temp checker against the transformer itself and regularly checked. System runs 1000watt microwave fine and a couple of soft load fridges and a light or two but realised all not well a few weeks ago when washing machine failed to complete cycle for unknown reason. Purchase date of this unit September 2013 and it has been run continuously under varying test conditions since then- but it will not and never has actually delivered what it is supposed to. Seller has agreed to replace transformer and other defective components if necessary since I am quite certain transformer is misbehaving and stripdown is imminent to test its capacity. I can live with inefficient no load since I have 16 batteries in my system- but when I need full load it must deliver that, and for a system rated at 3000 - 9000peak it just simply isn't, and if I ever buy another one I will make this kettle test and repeat this for at least an hour in stages [boiling water does evaporate!] Here endeth my experience with the W7 and if anyone has a circuit diagram that would be nice since I suspect not even supplier has one for his techies for I have asked him/her for one so repair can be conducted efficiently and why a circuit diagram for a unit such as this is simply not available in the documentation at time of purchase is quite simply ridiculous. Time for manufacturers to change this arrogance I think. Cheers. Mark
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Re: Cutting your energy bill.??. Don't try this at home, ki

Postby Warpspeed » Sat Jan 18, 2014 11:04 am

Tracker wrote: I suspect that MANY have thought about how they can reduce their actual bills, and I have attempted to take a "Standard Approach" at shifting usage from Peak to Off-Peak.. Clearly, it only works when there is more than a 4:1 ratio of Peak to Off-Peak tariff costs, and even then the capital cost would likely NEVER be recouped. As already mention, a tangible benefit is that I do have a means of emergency fridge supply, should the grid go down..

Just discovered this thread, and Tracker, you must have been reading my mind.
There are a few observations that have already been made in this thread that I would like to expand upon.

First are the "nuisance" small constant loads that must be constantly powered with 240 volts, 24 hrs a day.
This includes the magnetising current of small transformers in many household appliances supplying electronic control systems, digital timers, and displays of all kinds, even when the appliance main switch is innocently in the off position in many cases.
Thirty milliamps here, sixty milliamps there, very quickly adds up (0.173Kwh and 0.346Kwh/day) a few of those around the home can add 1 to 2Kwh per day all too easily.
An energy audit around the home can be a truly eye widening experience.

The next hurdle is the inverter. It really needs to run continuously to supply the above nuisance loads.
Two main types of inverter, the transformer inverter which switches the low voltage dc into a step up transformer to generate 240 volts. This will be hopelessly inefficient at very light load because of the very high magnetising current consumed by the the huge volume of iron in the 50 Hz inverter transformer, even with zero output load.

Much better is converting a very high dc voltage, either 350 volts dc, or 700 volts dc direct to 240 volts ac with direct semiconductor switching, either a true PWM full sinewave, or a "modified" sine wave, (which is really a square wave).
This can work extremely efficiently at any load, but is especially an advantage with very light nuisance loads.
It can also supply very high peak transient starting currents from a high voltage electrolytic capacitor bank.
This can store an amazing amount of energy when charged to really high voltage (e=1/2CV^2)

There then remains the problem of raising nominal battery or solar panel voltage up to 350 or 700 volts.
This is dead easy, and can be done more efficiently at any power level because we are not limited to 50 Hz transformer operation.
By using higher switching frequencies, and by using multiple voltage converters run in parallel, the voltage conversion process can respond faster to load changes, and be made smaller and much more efficient.
If you only need fifty continuous watts to run the nuisance loads you don't need a single 10Kw voltage converter.
Maybe a 200 watt one, a 1.5 Kw one, and several kilowatt monster that switch in sequentially, depending on actual load.
Low load losses can be kept extremely low, the high voltage dc capacitor bank will easily handle very high current surges for a cycle or two without complaint.

The other aspect that is probably killing efficiency is prolonged battery float charging, and the battery charger.

Using a really big battery charger for bulk charge replacement at constant current is fine, right up to just below the gassing point, where you reach the max set charging voltage.
What you then need to do is switch the damned thing right off !

Use a second totally different charging technique with a much lower powered battery charger to put the final 10-15% back into the battery. Constant voltage with slowly tapering current over many many hours or days, is not the best and most energy efficient or fastest way to do that.

What you need is high current pulse charging, similar to many high power desulphator designs.
Very short, very high current inductive discharges, force current into an almost fully charged battery and can complete final charging in a much shorter time without gassing or battery overheating.
Its much more energy efficient than taper charging with dc over prolonged periods.
And it has the advantage of reducing and preventing sulphation.

I believe the idea of using off peak grid power + solar + battery in combination can be made to both work and be cost effective, but a great deal of thought and planning has to go into it.

My feelings are, that much common commercial off the shelf conventional equipment is just not up to it.
A fairly unique system needs to be engineered from scratch, to do everything really well, and meet some pretty exacting requirements.
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Re: Cutting your energy bill.??. Don't try this at home, ki

Postby Smurf1976 » Sat Jan 18, 2014 9:34 pm

Without wanting to diminish any of the technical stuff, reading this thread really highlights that energy efficiency at home certainly does follow the basic law of diminishing returns.

Easiest - Put the existing electric hot water on off-peak and replace blown light bulbs with CFL or LED etc.

Slightly difficult - Install insulation, get more efficient appliances when old ones break etc.

Bit more difficult - Get a more efficient heater and install solar hot water.

Getting a bit more complicated - Install grid-connect solar.

Getting really complicated - anything that involves off-grid solar, batteries etc.

I'm not against it, just pointing out that once you've picked the low hanging fruit with light bulbs, heating water overnight or from solar, ceiling insulation etc then it gets progressively more difficult (and expensive) to save each additional kWh of power from the grid. A point comes where, in most situations, a further reduction in power bills actually increases the overall cost and the idea of charging batteries overnight etc quite likely falls into that category I'd think. If not then it's certainly getting very close once you consider the cost of equipment, lifespan, efficiency and so on.
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Re: Cutting your energy bill.??. Don't try this at home, ki

Postby gyro » Sat Jan 18, 2014 10:48 pm

Hi Smurf
I agree it is a bit like the pyramid system those at the bottom pay for those on the top. However if you count your beans after government subsidies, the early bird got the worm but because of the worm it got to lay the golden egg.
Many of those that still get 60 cents rebate because they had the forethought to get in early are reaping the rewards. Now those people who took advantage of the cheaper panels, inverters and installation combined with the newer net in-feed system are the ones who in the long run reap the rewards.
I have 5 Kw of solar going into the grid gross and 1.7 Kw of solar, combined with 800 watts wind and 800 watts water power into 850 AMP Hour batteries at 48 volts DC running a 6000/12000 watt W7 inverter purchased while our dollar was very strong. I am currently running my whole house 6 to 12 hours a day using the inverter I don't get a power bill any more, instead they paid me $817.00 last quarter.
All my systems have in fact paid for themselves in the first 2.5 years.
For those that persevere we are :lol: laughing all the way to the bank, increasing the value of our property and some even have fun doing it.
Antonius
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Re: Cutting your energy bill.??. Don't try this at home, ki

Postby Warpspeed » Sat Jan 18, 2014 11:53 pm

Yes absolutely.
The first steps to take should be a complete electrical energy audit.
Measure the actual current draw of every single electrical contraption and gadget you own.
There will be MANY real shocks and surprises in store when you estmate total watt hours per day.
Things like 2.5Kw microwave ovens are nothing if only operated for less than a minute or two per day.
The consumption of a simple mains powered electric wall clock running 24/7 can be frightening.
Replacing truly ancient appliances with current models can be hugely beneficial to running costs, as well as usually doing a much better job.

But it is true, eventually you get down to real bleached bare bones, and rapidly diminishing returns.
In my own case I have almost halved my quarterly consumption for only a very few hundred dollars spent on "new goodies" which should all be recoverable in a year or two.
Although the recent four day heatwave in Melbourne has shot my electrical usage into orbit.
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