Thread: Off Peak electricity as an alternative to Solar

good plan....

the biggest problems your already in front of which are

the cost of the batteries (you had them)
the cost of the inverter (youve got it)

all you need is a charger and the authority to hook it up to off peak (which I think should just be a case of writing up and asking for it)

the possable non red tape killer is going to be the cost difference between off peak power and on peak power vs the loss in the system

if you loose 20% of the power going from mains to battery to inverter to lights but your off peak is only 10% cheaper you're loosing money.

Dave has covered most of it. There is of course the hassle of changing over if using it to save money. Of course for blackout readiness this is less of a problem - probably easier than starting a generator.

As far as saving money goes, as Dave says, the difference in cost of the power is the key. But bear in mind that the charge/discharge efficiency of lead/acid batteries, while better than any other battery type, is still only about 85% at best*; factor in the efficiencies of the charger (60-80%) and inverter (70-95%), and you will be lucky to get much better than 50% overall efficiency.

John

* The amount of charge put in is pretty close to the amount of charge you get back out, the difference being represented by the amount of gassing, pretty minimal on the type of battery you would be using. Where the loss of efficiency comes in, is the difference between the charging voltage and the discharge voltage. If your average charging voltage is, say 14.5v, and your average discharge voltage is 11.5v, that is an efficiency of 79% right there. Of course the actual charge and discharge voltages will largely depend on the currents involved relative to the battery capacity, so these are only sample numbers.

While cost is a consideration, trying to get a saving out of the set up is not.

I’ve been here about 10 years now and had at least 50 hours of blackouts during that time.

While this may not seem much, one was for 23 hours and even though we have not had one for some time, last week we were out for about 5 hours, all because a garage ( house type, not servo type ) caught fire, brought the power lines down and they couldn’t fix the power lines till the fire was extinguished.

And the real reason is that I just want something to play with, but don’t tell the wife.

go for it, it'll work and work well. I use a similar set up at home from my camping kit.

(its not permanantly hooked up tho)

battery charger charges the camping batteries after a trip, a small trickle solar cell keeps em floating and if the power goes out I just run a power cord to the inverter and run up a couple of neons and the fridge

I get about 20 hours worth out of a battery with the house fridge and 3 lights.

This is exactly what I have to do every time there’s a blackout, only thing is that everything is packed away and it takes me about 20 minutes to hook all the gear up and get going.

I was considering fitting solar panels and with all the weird weather we are having, more blackout are likely and this seems a quicker and initially, a cheaper way to get started.

What I need is some feedback on how large inverters work as far as powering them full time and having the output loads cycling from no load up to about 70% during peak usage times, every day?

Originally Posted by drivesafe

.....

What I need is some feedback on how large inverters work as far as powering them full time and having the output loads cycling from no load up to about 70% during peak usage times, every day?

This will depend on the inverter, but is basically the same as in a solar power setup like mine.

The inverters I have operate up to a 300% overload (for 2 minutes - provides motor starting etc) and will continue to operate down to an adjustable minimum power draw. If the current draw drops below this (usually set about 6w) the inverter shuts off and restarts when something is switched on - while switched off it pulses on for about 1/2 second every five seconds or so to see if there is a load. (this pulse will show as a faint flash in some CF lamps while switched off!)

One of the things to note is inverter efficiency. The quoted figure will be the maximum figure, typically at around 80% for a sine wave inverter, higher for modified sine wave, but at low current draw the efficiency may be well below 20% (makes sense as the inverter has the same overhead at all loads, but the smaller the load the larger proportion of the total power draw it represents). This effect is the main reason for eschewing an excessively large inverter.

Some inverters may also have problems with strange power factors that can result, for example, from running nothing except switchmode power supplies. Usually this only results in dropped efficiency, but some may switch off.

Hope this is the sort of information you are after.

John

What rebates are being offered by the govt. for solar install. A friend was thinking of installing one.

It appears you pump your power into the grid and get a further rebate from that (or it offsets your energy usage).

Ahh, here we are:

If you are eligible for the current $8,000 Australian Government Solar Homes and Communities Plan rebate, eco-Kinetics requires you to pay the additional $185 prior to the installation taking place. This $185 cost is refundable if for some reason the installation does not take place at your home.


If you are not eligible for the Solar Homes and Communities Plan rebate, eco-Kinetics will require you to pay $8,185, the full cost of the system and installation.

Solar Homes Program - EPA

Government rebate put solar power on roof for $185 | The Courier-Mail

http://www.environment.gov.au/settle...ml#eligibility

all of my stuff runs from 1 800w cheapy inverter I got from kmart...

the solar panels are only to keep the battery floated, it gets mainly charged from the vehicle or the charger unless I install it in the trailer which has a 70w panel for topping up...

pics to follow.