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Forum Index : Solar : Advice on Off Grid System Components
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| DaveC Newbie  Joined: 27/10/2014 Location: AustraliaPosts: 11 |
I am looking for some advice from the experienced Forum Members who have good knowledge of off grid solar installations. I currently have a grid connected solar system with 8 * 180 watt solar panels giving a total of 1440 watts output, and this is connected to a Latronics PVE 2500 inverter. I initially installed a larger inverter when the panels were installed knowing that at some stage I would expand the capacity of the installation. This system was installed in 2009 so I am currently on the 60c/KwH NSW Feed in Tariff which, in NSW, ends in December 2016. I cant expand the existing system until the current scheme ends as I will lose the current tariff unless I install a second inverter for the additional panels at the reduced tariff. I have obtained 12 * 2v 1000AH gel cells to give me 24V supply, so I was considering installing another 4 * 180-250 watt solar panels and a charger/inverter to be used until the current rebate ends and then possibly connecting the extra panels into the existing Latronics inverter. Most of the batteries are approximately 16 years old and have not yet reached their 80% capacity design life (18 years) although several of the batteries are newer (6 years old), so I will make the assumption that the batteries are now de-rated to say, 800AH. In the meantime (and possibly into the future) I am considering having a separate installation and powering parts of the house from the batteries and the separate inverter. I am looking for advice from the experienced Forum members on the best methods for the installation and hopefully the least expensive. (In regards to my own experience, I have a reasonable knowledge in electronics and telco power systems). Initially I would look at powering the garage, pool and laundry items and I can schedule the operation of various items (pool pump and say, clothes dryer) so that I dont have a large peak current load (max 8A AC). In summary I am looking for a reasonably priced solar charger (MPPT?) or advice relating to what should look for. I can build one if it is economical to do so if I have a (proven) design. What size is recommended? I am looking for a reasonably priced inverter (off grid) to run initially my garage containing pool equipment and a laundry. What size is recommended? Should I look at a combined charger/inverter instead of separate units? Any other advice or feedback that Forum Members are able to provide would be appreciated. I am located in Sydney. Dave |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Dave Going off grid is a smart option these days, and I hope to see more people do it. I've been off grid for over 3 years now and wont look back, though I do miss grid power from time to time. The advantages of off grid are cheaper and more reliable power, but the initial investment puts a lot of people off. Sounds like you're well on your way though. First up, your solar panels, are they 72 cell panels? The 72 cell panels ( I think the other type are 64 cell ) have a higher output voltage, so work better in low light. If not, its no big deal, but 72 cell is the way to go for future purchases. If you want a reliable inverter, I recommend Latronics. Expensive, but sturdy and made here in Australia. Or you could buy a cheaper chinese inverter to get your started, and accept they may be less reliable and less efficient. Ideally you should go for a 48v system instead of 24v. The cabling is easier and you end up with a more efficient system. But as you have the batteries, stick with 24v for now and consider upgrading later. I built my own charge controller, its working well, but I dont have a circuit that I can share, it was sort of built on the fly, and uses a Maximite clone as the central processing unit. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| DaveC Newbie Joined: 27/10/2014 Location: AustraliaPosts: 11 |
Hi Glenn, Thanks for your comments and input, and BTW, I have enjoyed reading your various experiences with your off grid farm. In regards to solar panels, I am not sure whether my existing panels are 64 or 72 cell, but I will take your advice when I get around to buying the additional panels and look for 72 cell. In addition to the batteries I obtained to give me 24 V, I acquired a Thytec inverter but it requires 48V DC input, so it looks like I will need to expand my battery bank to 48V, but I won't be able to do it with a string of 2V cells, so will have to look at what my options are there. I realise that may cause charging issues with batteries of different type or chemistry, so I will have to solve that also. Regards, Dave |
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Hi Dave, I think it would be worthwhile doing some research on your grid connect latronics inverter. I have seen a couple of them with 16 x 185w solar panels wired to them But I noticed they had also made some effort to keep the inverter cool. A quick look at a recent spec sheet says input 3100w max, output reduced to 2100w @ 50 deg C. I dont know how much this would shorten the life of the inverter or even if yours is built to this spec but it would be worth finding the build date and serial number and asking the question. the fact that it will be seven+ years old by Dec16 probably means it wont owe you much by then anyway. You will also benefit by changing from gross metering to net metering if your system was originally installed as a gross metering system. adding panels can be tricky, chances are you wont get 180w mono's or poly's now, there are still some 190's around but they may be a different thickness. Sometimes the existing panels need to be repositioned to get the new ones in and the old rack wont match the new stuff. it can be cheaper to replace the old panels with a complete new set and sell the oldies as pre-loved! I know it is not as sexy as off grid but you will save some serious cash if you can net meter and use power while the sun is shining (pool pumps and aircon in particular). You might also consider what inverter will replace the pve2500 in the future, there are a new generation of inverters that can be overpaneled and set up as zero export or even switch on loads when the capacity is there. The fronius brand is an example of where things are headed. there is a couple of things to ponder on cheer Yahoo I'm confused, no wait... maybe I'm not... |
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| DaveC Newbie Joined: 27/10/2014 Location: AustraliaPosts: 11 |
Hi Yahoo, I took your advice and spoke to Latronics regarding my inverter and it is an early model and cannot be taken above 2800 watts, and I don't believe that temperature will be an issue as its mounted in my garage which is well insulated (Hebel block) and with the current 50% load it runs quite cool. Latronics were able to give me some advice on panels and there is a panel currently sold by Bluesun which is 60volts o/c and 250 watts and by stringing 3 of them together will give me the 180v my inverter requires, and will give me just over 2 kw total, well below my inverters maximum rating. The real issue I am looking for are answers for what can I do economically to utilise the 24v battery string I have between now and Dec 2016, as I can't increase my grid output as I will lose my 60c Feed in Tariff (in addition to a hefty fine). Any advice from Forum members on my off grid supply questions would be appreciated. Dave |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Maybe a 2nd system. Use you batteries as the start of a off grid system to work with the grid connect system. Basically, two separate circuits. Add solar panels, a charge controller and a small inverter to power your houses light circuit? You would need to talk to your sparky to see how easy it would be to separate the light circuit. If the house is wired correctly, should be straight forward enough. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| upwind Newbie Joined: 13/06/2015 Location: AustraliaPosts: 6 |
can anyone give me an bit of advice about my Plasmatronics (PL60) controller. The max charge rate has been around the 38 amp value but usualy around the 23 to 28 amp's on most days. What I need to know is ,1, can I just keep adding panels to my system,2, will I cause damage if there is more than the PL60 is rated at (60 amp), and can I mix different panels, there is different panels on the roof now, Visualy that is but I am not sure if they are of the same specs ! I have booked a sparky to come next week as my inverter is outputting 290 volts ! I need to up the input as it's 10.30 am before sunlight hits the panels and it's gone by 4.30 pm, even shorter exposure during winter months and running the generator is contrary to the sustainable idiom of off grid living !! any advice will be greatly appreciated, thanks. If it can't be fixed with a hammer and chisel it's probably electrical !! |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Until someone comes up with some real-world experience with the PL60 I would hope that you could add a few more panels. IE max 38Amps up to 50Amps or so. Are you paralleling all the panels? You need to provide more information, each panel's Vmp and even what your system voltage is. I would think that mixing panels with much different Vmp is not desirable. 290Volts! So, you are blowing up some of your appliances? |
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| flc1 Senior Member  Joined: 20/11/2011 Location: New ZealandPosts: 242 |
If you join panels in parallel they need to have same voltage, if you join in series they need to be same amps; or current, panels can be diffent watt output aslong as you have the volts or current the same ;depending on how you connect them |
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| Oldtimer47 Newbie Joined: 30/10/2015 Location: AustraliaPosts: 3 |
hi, I have just found this site, I am on the Darling Downs, I have 3kw of solar panels on the roof, very annoyed about the fact that I get 6 cents per Kw from Ergon, when they are charging me 26. not a bad free profit. I am thinking of putting a small, part off grid system in, just to start off, that will be running my Fridge, (new Samsung 4 1/2 star) fair sized LED TV, plus laptops and a few lights, Compact fluro, then, see how it goes and work up from there, those items will all be hooked up 24 / 7, I have been thinking about this for a while, my Plan ??? is a 1000w inverter, 24v, a couple of 12v deep cycle batteries, in series, to give 24v, at this time I plan to charge the batteries using a 24v battery charger hooked up to a timer of a day time when my panels are giving out free excess power, I have one of the meter thingo's the Gov put out a while back, I have been watching it for a while of a night time, seem to be using up to 700w this is all stuff I can do, extension leads, power boards and so on. I will still be using mains power for hot water, washing machine and some other items, any comments appreciated, Oldtimer. |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Oldtimer47, While you are mains connected you will never get pay-back on the batteries you buy. It could make a good standby system if you have a lot of blackouts, though. I suggest you have a look at this site openenergymonitor. Maybe, using the excess power straight into your hot water tank would be a better option. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
A complete Solar system incorporating a Tesla Power Wall for storage is supposed pay for itself in 6 years. This is based on Australian figures, not sure how much sun you get in NZ. Tesla 6 Year Payback There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
I only pay $0.25, so now my payback has doubled to 12 years. 12 years of connection charges are $40 * 12 * 12 = $5800, didn't see that in a quick read. Also, what if line charges and the rate increase because most of your customer-base are not using your grid power? Sunlight hours, Christchurch 2050 and at a rough guess 1700-1800 where I live. Should work for some people. |
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| Oldtimer47 Newbie Joined: 30/10/2015 Location: AustraliaPosts: 3 |
hi, thanks for the info, the Hot Water is probably the best idea, it is only a small unit, if I was to install a much larger unit and set it to heat when the sun is full, or even go to a solar hot water unit. thanks, Oldtimer47, While you are mains connected you will never get pay-back on the batteries you buy. It could make a good standby system if you have a lot of blackouts, though. I suggest you have a look at this site openenergymonitor. Maybe, using the excess power straight into your hot water tank would be a better option. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
If you keep an eye out on gumtree you can pickup second hand solar hot water systems for under $500. The one I have holds 320 litres and I only need to turn on the element if we have 3 days of very cloudy weather. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
After my experience with a professionally installed solar hot water system and the way the price of PV panels has dropped I would now put up some extra PV panels and dump the power straight into the HWT. Maybe you need twice or more area in PV compared with solar hot water, but no pump, no thermal relief valves (on the collector), no frost protection, etc. There are many microinverters available now that convert the PV voltage to 230VAC, search <ebay, aliexpress, etc> |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Out of a choice of valves and a pump or a microinverter from aliexpress I know which one I would put my money on to last longer. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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