Off Peak electricity as an alternative to Solar

[drivesafe]

Hi folks and this is not my idea but was explained to me in some detail and sounds interesting.

The idea is to use the Off Peak power supply to charge a bank of batteries and these batteries are used to power an inverter that then powers all the lighting in a house and one fridge.

The purpose is to give a Blackout proof lighting set up.

I already have well in excess of 1,000 A/H of stored capacity in the way of a 12 volt Ag battery bank and only use it every blue moon when doing high current testing of new dual battery controllers, so they sit around for months at a time doing nothing.

I have a 1,500 watt inverter and as every light in the house are already low power “Greenie” globes, the inverter can easily handle having the lot on at once. Not that worried about powering a fridge.

The only device I need is a decent sized battery charger and I hope to have access to a new line of high current marine battery chargers very soon.

My question is, does anybody know of any regulations governing or stopping the use of this type of set and if anybody is already using such a similar set up, what are the pros and cons of it.

[Blknight.aus]

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.

[JDNSW]

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.

[drivesafe]

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.:confused:

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

[Blknight.aus]

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.

[drivesafe]

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.:mad:

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?

[JDNSW]

.....

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

[p38arover]

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 (http://www.epa.qld.gov.au/environmental_management/sustainability/energy/solar_homes_program/)

Government rebate put solar power on roof for $185 | The Courier-Mail (http://www.news.com.au/couriermail/story/0,,24066409-3102,00.html)

http://www.environment.gov.au/settlements/renewable/pv/index.html#eligibility

[Blknight.aus]

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.

[harlie]

Re original query to regulations. If you are to connect your charger to off-peak power tariff, it need to hard-wired (no plug)– you can connect anything to an off-peak circuit (AC, pool, freezer, dishwasher) as long as there is no plug enabling you to change the appliance over to the standard circuit. The idea is to offer the cheaper power but force it use to off-peak times.
For this idea it would be perfect - don't need a charger going full time, off-peak runs for 18hrs/day and it would kick a 3-stage charger into restarting its cycle...

[Tombie]

So in 87600 hours you have had 50 hours of no power :) seems quite respectable...

If doing it for fun... Go for it...

If doing it for 'serious' then I wouldnt bother...

Even a 24 hour blackout is just a day camping in the house :cool:

[harry]

tim, not sure you can use off peak here on the gold coast, someone will correct me i am sure,
the only off peak power we have is the hot water service, and that is powered by off peak, which is turned on and off by the electricity supplier, by some sort of magic pulse down the line or something, we cannot fire up the hot water service here, to boost water temp if we run out, until 10 pm each night, never been awake to find out when it turns off.
so i presume you would need a 'leccky' or talk to the power company 'origin' in my case.
it's not like we had in melbourne where we just wound the time clock around to switch the water heater on, when we needed extra.

[abaddonxi]

I had a plumber out the other day who said there are two types of off-peak. Type one, which is a fixed timer, turns on and off at the same time every night. Type two, responds to signal and turns on and off during the day and night when demand is low.

Simon

[BigTim]

I'm not familiar with the Queensland regulations but down here in NSW I strongly suspect our power companies would object to you essentially running your whole house on off-peak.....:)

I'd suggest speaking with a local sparky for the correct interpretation of the local connection rules.

If it winds up going ahead you'll probably need to construct a dedicated battery room with all the appropriate ventilation, acid spill and electrical fault protection measures. Australian Standard AS4086.2 - Secondary batteries for use in standalone power supplies will most likely be the applicable reference.

Best of luck - please let us know how it turns out.

[scanfor]

I run my pool pump from off-peak, and as mentioned earlier, the only restriction is that it must be hard-wired (i.e. no GPO on the circuit). I´m told that this is a requirement to prevent other appliances being plugged into the Off-peak circuit with the resulting possibility of them activating without notice or your intervention when the off-peak supply is re-energised.

[Blknight.aus]

more or less, any fixed appliance can be run on off peak.

I know of a few people who have garage heaters that only kick in on off peak.

I reckon it'd be ideal for big bank battery top ups...

[muddymech]

there is loads of links under battery bank on google.

Battery Back-up Power Emergency Backup Power (http://www.wholesalesolar.com/back-up-power.html)


i was trying toi find a system i had read about that was basically a battery unit the size of a cargo container which would use off peak power and supply several houses during the day, the idea being power staions can run at efficently as possible and avoiding the up and down of power demands.
of course i can nto find the info now.

[barney]

don't know about QLD rules, but i don't think you could get away with it in NSW. similar rules that require hard wiring of items on off peak, but i think the type of appliance is regulated.
i wonder if the money you would save by doing this would come anywhere equalling the set up of batteries and inverter, that is if you didn't already have it hanging around.

[JDNSW]

This discussion reminds me of a visit to Myanmar I made about 1980. When there I visited a data processing centre; they had the largest UPS I have ever seen - it included a battery room the size of a small house, filled with 1000AH lead/acid deep cycle cells. Perhaps a commentary on the reliability of the power in a city (Rangoon) where the top hotel thoughtfully supplied you with a bedside candle and matches.

John

[EchiDna]

JD has it - buy a junked server room UPS for your charger - all the transformers etc will be fine, the batteries you have already - as long as the voltages for the transformer's secondary fit to your battery backup system, you are home and hosed...

there is a great article on Dan's dataon a very similar topic: The DIY (or, if you must, "Ghetto") UPS (http://www.dansdata.com/diyups.htm)

[abaddonxi]

JD has it - buy a junked server room UPS for your charger - all the transformers etc will be fine, the batteries you have already - as long as the voltages for the transformer's secondary fit to your battery backup system, you are home and hosed...

there is a great article on Dan's dataon a very similar topic: The DIY (or, if you must, "Ghetto") UPS (http://www.dansdata.com/diyups.htm)

Was thinking of that page myself.

Simon

[drivesafe]

Thanks for all the great replies and keep them coming.

As to the regulations, there are no Fed or state regulations but the regulations are set by each power provider and each provider has there own rules so I will have to sort out what my provider will or won’t allow.

Long way off installing anything yet.

[rar110]

I have 2kw grid connected solar system. Solar powers the house + excess into the during the day as you probably know. So no blackouts during the daytime.

[miky]

In S.A. "off peak" is only allowed for hot water and heating.

Quote:
... permanently installed storage water heaters with a rated delivery of not less than 125 litres, storage space heaters and other approved thermal storage applications