JJ
Member
I thought I'd just post a link to an "Instructable" I have posted on this website.
http://www.instructables.com/id/Solar-Power-Station/
<image src="http://cdn.instructables.com/FA7/3E7P/HV2AFH6X/FA73E7PHV2AFH6X.MEDIUM.jpg">
It is my 2nd step towards moving off grid - (1st step was a solar grid tie system). This is said with a bit of "tongue in cheek" as I live in suburbia and really don't expect to be off grid any time soon. 
I hope you enjoy viewing it.
JJ
Member
JJ said:
I thought I'd just post a link to an "Instructable" I have posted on this website.http://www.instructables.com/id/Solar-Power-Station/
It is my 2nd step towards moving off grid - (1st step was a solar grid tie system). This is said with a bit of "tongue in cheek" as I live in suburbia and really don't expect to be off grid any time soon.
I hope you enjoy viewing it.
Bushwalker
Member
Nice work JJ 
BW
Greg C
Member
Great idea. A simple adaption of the idea if you have a grid tie inverter with the net feed in 6c tariff could be to arrange for a mains charger to charge the battery whenever the sun is shining. Just how you could tell the charger when the sun is shining I don't know but.... Then use the inverter to power the TV etc. Ours draws 100 watts and with the external STB and DVD player the whole kit is probably 150 watts. If used for 4.5 hours after dark the system could cope I think. You would get charging every day, as I know our 2.8kW system outputs a few hundred watts even in the worse weather. Wether it is cost effective needs a bit of calculation the only unknown is the life of the battery.
If it works out cost effective (although just running the TV off the sun would be good enough), what about the computer system with the constant load of wireless networking etc. Could also be a good candidate for its own battery solar charged system.
JJ
Member
Ok Greg I think I see what you mean, I had not thought of that as as an option. I'm currently on the NSW gross FIT 66c/KWH. However, when that scheme ends for me (in a couple of years) I will take that opportunity to reassess whats best to do. Clearly the energy retailers have little interest paying a fair price for the electricity generated, at the same time, the energy storage technology for householders is still restricted to batteries and for the moment they are too expensive/difficult for the average Joe/Joanne to maintain in a 'normal' domestic setting. However things are changing.
I heard a really interesting review of the Austrlaian electricity market on the radio at the weekend....just 5mins long and worth a listen.
http://www.abc.net.au/radionational/media/5443136.asx
...until then I'll keep tinkering!
I've been running all IT, including charging mobiles and laptops, off solar charged batteries for many years. Works well with independence from blackouts an added bonus.
Lately I've recommending standard UPS units for everyone (around $110) to keep modems, cordless phone bases and a single CFL lamp etc going during blackouts. These often have a small 12V SLA 7Ah (84Wh) battery which is enough for up to 2 hours backup. They also have some surge protection and usually 6 outlets so are much better value than 'surge protection' power boards.
JJ
Member
Hi Rockabye - Using a UPS is great idea for blackouts at the same time I would not want to have one constantly connected. The reason is that UPS's use electrical energy even when totally idle. Even if it is a small UPS I estimate it is somewhere between 10-30W and this is something I would not want running 24/7. I am on a TOU meter and as such pay ~30c/kWh during the daytime so am keen to remove all loads during the peak period which is 7am-8pm I think.
Your post however reminds me of a UPS project I may do in the future. In my home the last power hungry daytime energy user is my fridge. My plan is to connect the UPS to the fridge and then switch the UPS off (at the mains) at 7am and back on at 00.00am -midnight, ie the UPS will only be on at the mains during the night. The total energy used will be no different (actually higher for the efficiency issues I mention above) but the cost will be much lower as the fridge will now be using all "off peak" electricity.
I actually have an unused 3000VA UPS in the garage but I think my current fridge which is 14 years old may deplete the batteries too much during the 17 hrs it would be disconnected from the mains. At about $250 for a new set of batteries it would be counter productive if I kill the batteries in a year or 2. I might reconsider if I upgrade the fridge to a more up-to-date unit which are much more efficient (better insulated and running on isobutane (R600a) refrigerant).
Lance
Key Master
I have my main PC on a CyberPower BR850ELCD UPS, works very well, never a glitch when the power goes off, was $170 at the time but cheaper now, such as http://www.scorptec.com.au/product/UPS/UPS/40279-BR850ELCD
Benny
Member
Interesting concept.
The UPS Lance links is $135 and has capacity of about 100Wh = 0.1kWh.
My fridge uses 1kWh/day. Lets assume its a uniform energy use so about 40Wh/hr.
So it could run my fridge for say 2.5hrs/day.
I'm on TOU tariff at 15c off peak and 45c peak.
So if I used the UPS to timeshift 2.5hrs per day, I'd be shifting 0.1kWh and saving 30c/kWh so saving 3c/day.
So the payback time is $135/3c = 4500days = 12years.
And would a UPS be designed for daily full charge/discharge ? or just the occasional cycle?
I'm sure bigger UPS would be cheaper per kWH shifted but it doesn't look feasible to use several small ones per appliance. I'll wait for bigger off grid systems to come along.
In fact I'm planning that in 5years when my iMiev battery is out of warranty, but hopefully still giving at least 10kWh of capacity, that I'll get a new one and bring the old one in to the house.
JJ
Member
Thanks for your input Benny - I think it is an interesting topic that probably bears more scrutiny...however the small 'retail' UPS's sold for computer systems are just good enough for keeping things going for a short while so that you can shut down computers properly, (and possibly running a few other low wattage devices for an hour or 2 as Rockabye reports).
Just a bit more on fridge power usage......I did a bit of measurement of my fridge which as I said earlier is an old beast (Samsung). It has used 2.4kWh in the past 24 hours. This is a bit on the low side I think as:
1) I was away from the house for most of that 24Hrs
2) Its late autumn and so the ambient temps are lower.
I guess in summer with frequent door opening/closing you could probably double that usage.
Looking at the kWh usage though I don't think your calculation of an average per hour is reasonable because:
1) Daytime ambient temperatures are higher than night time temperatures
2) The fridge door remains shut at night (unless you are nocturnal 
)
Therefore, I think the KWh usage will be skewed towardsthe daytime hours. (I'll do some more readings and post in a week or 2).
Another idea, and this is not new, (but I've not seen it implemented on a domestic fridge yet), is to set the fridge thermostat to its lowest setting during the night and then back to 'normal' during the day. This will effectively super cool the fridge and its contents using off peak electricity. I might be able to do some rough experiments with this also as my fridge has push buttons on the front to alter the temperature. Unfortunately there is no temperature readout/indicator so, as yet I do not know what the available temperature range is (I suspect only a few degrees).
Benny
Member
Maybe you're best option is to buy a new, efficient fridge (-; 2.4kWh/day is quite a lot, thats 876kWh/year and $227 per year at 26c/kWh.
You're probably right about the values I used but just trying to get indicative calculations and opening/closing the fridge doesn't really use all that much extra.
When you put the meter on the fridge check out the power it uses while operating (not standby). If its say 130W then it can't use more than 0.13kWh/hr or 3.12kWh/day. (not allowing for possible defrosting heater).
JJ
Member
...a new fridge yes! ...but the old dilemma of capital cost Vs. additional cost to run...and if I do my discounted cash flow projection....blah blah blah. 
Anyway I'm sure you know what I mean - The existing fridge (and I should have more accurately said 640Litre fridge/freezer) is in great condition and to dispose of it may mean landfill or if I am lucky Ebay.
Not withstanding another 24hrs has passed and I now think it is probably running nearer to 2kWh. I say this as I noticed I'd turned the thermostat up to MAX (ie the lowest temperature setting) as a result it would have taken a while for it to super cool the fridge and its contents (I've always used the mid setting between Max and Min)
Another thing I must correct is the rates for the electricity I buy....I think I must have had my head in the clouds when I said ~30C. Its actually:
Peak 47.77c/kWh
Shoulder 19.86
Off Peak 11.97
...so for every kWh I can shed from Peak to Off Peak is worth 47.77-11.97 = 35.8c each.
A conservative scenario would be to transfer 50% of the daily 2kWh total to Off Peak = 2/2 x 365 x 35.8/2 = $130.76/annum Hmmmm Still interesting.
BTW the running wattage of the fridge is:
5w idle
18W air stirring
190W compressor on
Your point about opening doors and the attendant loss of coolth is accurate (as the cold air escaping embodies only a small amount of energy relatively speaking), at the same time I'd still like to know what the loss is in a real world situation (with a statistical sample of 1!) A more particular issue of energy loss would be leaving an item out of the fridge for some time then returning it, say 1/2Hr later when it had warmed up to the ambient.
Tony From West Oz
Member
It is possible to expand the battery capacity of many UPS by paralleling additional batteries with those installed in the UPS. This would allow you to use an UPS which has the inverter capacity to run your fridge but a small reserve capacity, for longer periods.
eg, if your inverter has an internal 24v battery, you could add another string of 2 * 12v batteries in parallel with the internal batteries to increase the reserve capacity of the UPS. These 12v batteries should be of the same capacity as each other, but can be much larger than the internal batteries.
CAUTION: Some inverters (most small ones?) do not isolate the battery from incoming mains voltages (due to charger design). In this case, it is not advisable to extend the internal battery connections outside of the UPS case as it introduces an electric shock hazard.
Some UPS (for computer server power backup) do have expandable batteries, usually separate battery cabinets and interconnecting cables. These are eminently suitable for your application.
Some UPS require that mains power be present before their inverter turns on. These are not well suited for off-grid operation.
A time clock could be used to switch on the UPS charger during 'off peak' times.
