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Forum Index : Solar : Ways to maximise used own solar power
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| Boppa Guru  Joined: 08/11/2016 Location: AustraliaPosts: 814 |
My ex at the time thought I was crazy, turning off powerpoints all the time etc I showed her the meter readings but she really had no idea what the numbers meant So I turned on the backyard portaflood and told her to not turn it off ever She was kinda `whaa you crazy' Told her that was how much power we were using day and night with all the plugspacks etc we had running That got the message through, and I had to laugh a few weeks later when she complained when I left the computer powerboard switched on overnight (I was downloading a movie), giving me a talking to for wasting power LOL I created a monster |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Interesting discussion. How did you check each appliance's power use? Andrew |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
(I bought a new washing machine and got a plugin `KW hr tester' for free while living there and went around checking everything in the house lol) bunning kwhr meter mines an older one with a box in the middle of an extension cord, but this one is the same basic idea very handy when checking parasitic loads |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Thanks Boppa. At $20odd it is money well spent. Cheers, Andrew |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Andrew, Those e-bay power meters are extremely good for this application. There are several different numbers you need to have for getting the full picture of what an appliance is actually doing. Many appliances draw standby power when switched off, and other appliances can draw a highly variable power. Its those that are more interesting. Absolute peak power draw is important for sizing the inverter, and it can easily be ten or more times the average normal running power. Things that cycle on and off by themselves may actually use very little power over a 24 hour period, or maybe a lot of power. No way to really know until you make the measurement. Something like the electric kettle in your kitchen may be in use a dozen times a day for very short periods. All useful information to have to get the overall picture. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Some devices can draw an amazing amount in standby, my sister has a fetchtv box and it draws almost as much turned `off' as it does when on It is about 42/47w when on and still up around 30 on standby- so it running 24/7 is a quite heavy consumption the only way to reduce this is turning off at the wall (currently awkward as its in a 45 deg `corner' unit that covers the gpo), I'm thinking of making up a extension cord with a normal `wall switch' and fitting it just inside the corner so its easily reached instead I don't know why they bothered with the `standby' mode on it at all, as it actually still runs even when in standby so it can still record etc- there is no `off' mode at all- all turning it to standby does is blanks the screen/video drivers and turns a blue led to red..... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes, its fascinating to do a fairly comprehensive energy audit, some real surprises are absolutely guaranteed. And once you know, some quite simple changes can make a big difference. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I found it best to run over a 24hr period (or longer) to get an idea of the cumulative energy consumption as a `quick' test may not show the full usage pattern, fridges and freezers in particular may show vastly different results in a longer period, and even more change from season to season My fridge barely ran at all in winter, and over tripled its winter usage in summer (40+ deg some days) |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Biggest killers seem to be the multiple smaller things that suck power 24 hours. That can make a very big difference at night when you need to run on battery power. Batteries will probably be your largest capital cost for off grid. If you can halve your night time consumption, that will result in getting twice the bang for your buck when buying a battery. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Things like we had 2 led alarm radios next to the bed- each consumed 12w continuously (and were that bright they lit up the room, I used to cover the clock with a book so it wasn't too bright)- had a vcr that we hadn't used in months was in standby using over 25w, computer was 80w 24/7 with everything on `standby' / off added up to a huge waste of power, and with prices the way they are, added many $ to the bill unnecessarily, when the new house is built, being offgrid, wastage is even more important Luckily its not the first offgrid house Ive lived in, so I know the score about what I am wanting to do, in fact living offgrid before (over 4 years) means I have a much better idea of what I want as a result in my new house, am designing it specifically to be off grid friendly from the ground up |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yup, You don't need to sacrifice anything in the way of lifestyle. But if you can locate the leak in your boat, and fix it. Life will be that much sweeter. Cheers, Tony. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Yep, and if you time shift night time consumption to when power is taken directly from the sun the payback is more like four to six times (minus the cost of the technology that we use to change the use timing). panels that are angled to catch morning and afternoon sun lengthen the generation period and that makes it easier for some people to budget power usage through the day. probably the best example of saving energy is the effect of a pressure accumulator on a water pump. if you know how much water is used from 4 pm till 8 am and trigger the pump to run at 3pm with a 350 litre accumulator then not only will the pump save energy from a lack of high load starts it may not run at night at all. it is quite common to drop energy use from 1-2kwh/day to 100wh/day with the pump rarely ever running at night. the problem is accumulators are not cheap. I am happy to join the discussion however I have a couple of thing on for the next few weeks that will chew most of my time. I'm confused, no wait... maybe I'm not... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I have (some) East/West mounted panels set looking 60 degrees above the horizon. These are fantastic at sunrise/sunset and really kick in at least an hour before and an hour after the main North facing array has completely died in the bum. Well worth the effort, especially if you have no battery, or are grid tie. You get two to three hours more solar per day. But charging an off grid battery is rather different. That depends more on TOTAL surplus power available for battery charging. In winter the sun is manly in the North. And you will get more total power by utilizing the massive mid day peak to charge your battery by facing all your panels due North. So you really need to decide what is best. Maximum possible hours of solar. Or maximum retrieved watts per day given a similar total exposed panel area. As panels are now so cheap, an East/West virtual tracker is pretty much a "must have" if you have the means to install it. Cheers, Tony. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
the problem with having only a peak at midday with batteries is that we exceed our bulk charge rate limits with a smaller battery bank, I budget 0.35C rate for lithium cells and 0.15C for wet lead acid cells. there is a sticky situation where the panels we need during the day will not meet the maximum power requirement but if everything is switched off it will charge too fast for the battery chemistry. Some battery banks will spike up in voltage early and go out of bulk charge and the controller will limit the current but the lower resistance banks will not. There are a couple of neat ways around this but it still adds more money and complication to the system. I have to say that NE facing panels are a big hit with all the people I have installed them for, we get a lot of clear winter mornings and to have a couple of kilowatts happening when the sun is still on the horizon is a good feeling. Household chores like the laundry get started earlier and out of the way freeing up the day for other stuff. The first set of panels I installed like that was accidental and I moaned for days about wasting money on framing and the untidy look because it was a challenge to get them right. It was only after we got them in and I heard myself say "Yeah it will probably be OK because it gets pretty cloudy at four in the afternoon most days in winter around here" that I realised I hadn't being designing for local conditions and the clients needs.      I'm confused, no wait... maybe I'm not... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes quite right. I have been wrestling with this battery charging conundrum myself. Still undecided what to do, but will probably start off with a current limited charger that should extend the charging time without excessively raising the battery voltage. Just charge until the highest voltage cell reaches some threshold, then switch off the charger for that day. If charging rate is kept reasonably low say 0.1C to 0.15C it should reach a reasonably high state of charge with just a simple on/off charger control. Have about 6.5Kw of panels and only a 6Kwh Lithium battery to recharge. Should be plenty of grunt for that even on cloudy days. If charge power is limited to below 1Kw under any conditions, that should be plenty. Only use about 1.2Kwh (summer) to 2.5 Kwh (winter) at night anyway. I have 4Kw facing north, and 1.2Kw east, 1.2Kw facing west. Cheers, Tony. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
from memory I set the upper limit on the controller to 3.4875 volts per cell and the panel banks on the contactors at 3.44- 3.48 volts per cell depending on the battery bank resistance. The controller will take batteries to beyond 99% at 0.2C on bulk charge, I set the contactors voltage based on gut feeling. Technically they can max out at 0.4C charge rate. The slightly larger north facing bank current limits on the controller based on a shunt that sees the total current into the battery. The current limit settings you are thinking about look pretty good to me. I tried to run a system without a controller and it took some tweaking. The relay driver I use as a voltage switch also has timer settings for maximum and minimum high and low voltage times and both high to low delay and low to high delay. Its handy to cycle the contactors in the afternoon to top the batteries up, that means I dont have to finesse the low voltage threshold quite as much to stop it cycling or staying off. cheers Yahoo I'm confused, no wait... maybe I'm not... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I am trying to do without a charge timer, but as its all software controlled anything is possible. I am still a novice learner driver here, and have yet to put any of this into actual practice. Still at the metalwork stage for my battery box and BMS housing. Slow progress, but very happy with how it is coming along. The first thing will be some pretty good cell logging, and monitoring, and a graphical display of max, min, and current individual cell voltages on a large LCD screen. And like yourself, I believe tweak and learn, and tweak some more. As they say "slowly, slowly, catchee monkey". Cheers, Tony. |
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