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Forum Index : Windmills : Mixing Solar and WInd - how?
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| JPrel Newbie  Joined: 18/02/2007 Location: AustraliaPosts: 6 |
Has anyone mixed solar and wind - love to get your experience on this..... I have an 80w solar panel (12v) on a farm that is not supplying enough power as I have alot of trees that cut down on my sun heaps. I have just put in a small 12/24v fridge and need to supplement the panel as it does not generate enough power to run the fridge for 2-3 days. I currently have 3 x 75ahr deep cycle batteries in parallel hanging off my PL20 solar regulator (see http://www.plasmatronics.com.au/). What I want to do is convert my system to 24v to reduce the voltage drop that my 12v system suffers. I can get around it with big cables but gee votlage drop in a 12v system is a real pain. I also want to buy a 24v generator (just a cheap AUS$400) . The wind generator has no regulator built in, so I would like to know from someone exactly how to convert my existing system to a full 24v system. I assume I would need to firstly put a DC convertor on the putput of the solar panel to convert the 12v output up to 24v. I can then feed that into the PL20 because it can handle 12, 24 or 48v input. I then need some sort of regulator on the wind generator - don't know what I need here, can someone give me a pointer. Could I simply put the solar panel and the wind generator in parallel or is this too simplistic of an approach? Do I need to convert the solar panel to 24v (as this incurs loss) or is there a better way to incorporate a 12v panel and a 24v wind generator. I can buy a 12v generator, but I think going 24v is a better long term option for the whole system. I would really appreciate any real world expereince that people can give me about solar and wind systems, how to most effectively integrate them, is 24v's the way to go and why, and what's the best wind regulator to buy. I don't have alot of money so I am looking for a modest solution ($100's not $1000's) if possible. Thanks so much for your feedback. Regards John |
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| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Converting the 12 Volt panel to 24 Volts is going to be about 85-90% efficient. Will you gain in the long-run, with lower cable loss in a 24 Volt system? What efficiency is your 12 Volt feed line to the fridge? There is a Australian article on a 100Watt/day fridge made out of a freezer (230Volts) in one of your magazines. Have you looked at gas fridges? Keeping things cool is a BIG problem. I have made a top-loading insulated box with 2 * Peltier devices running at about 9 Volts (3 Volt drop in the feed line!) and 2 amps. I estimate it will draw power about 50% of the time at 5-6 degrees internal and 15 degrees external temperature. I run the heatsink in a small stream as keeping the heatsink cool is where you really gain performance. Now to work out how to freeze things! Have you got enough battery capacity? Sounds like you can't afford another solar panel. I have only one 80 Watt panel as well. Plan to buy another one and make a dual-axis solar tracker. You get a lot more power tracking the sun. Just have to keep the cost of the tracker down to about $400 to make it worth while. Good luck |
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| windman Newbie Joined: 02/12/2006 Location: Posts: 19 |
Hi john. The combination of wind and solar is good way of energy collection. In your case I would invest in another solar panel of the same type that you already have,connect it in series with the other and regulate it with the plasmatronic pl20.The solar is now at 24V.The 24V wind generator can also be regulated thru the pl20 using the load connection terminal , the plasmatronic web site details this connection, from memory I think its proram 4 L- set 10. You will need the external shunt kit and some kind of resistive load that can handle the max current of the wind gen and a relay that the pl20 turns on for current diversion, some use car horn type I prefer starter motor soleniods. I have used this method , it works well,its robust and only requires a modest outlay. Do not series connect wind and solar!! |
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Prof Newbie Joined: 01/12/2005 Location: AustraliaPosts: 33 |
Hi John, "windman" is on the right track with his advice, however I would be concerned that if the trees are affecting your solar panel then a wind generator may not perform either because of the trees.?? If you do as "windman" says and get another panel, the use of an MPPT regulator such as a Sunovation Solnexus 200 will accept the series input of two solar panels and get the very best out of them given your tree problem, and would keep you with a 12 volt system. You would be looking at spending around $1000 for another panel and the MPPT however. Prof I know boats!! |
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brett Newbie Joined: 08/02/2006 Location: AustraliaPosts: 39 |
Hi John I have the exact set up you are describing. We have 4 60w solar panels wired in series / parrel to get 24v. Run to the PL20. Also I have a F&P windmill as per Gizmo's instructions from this site, wired 7p3p. This is also wired directly into the pl20 positive terminal. The programming on the PL20 needs to be changed as per the website mentioned above. On the load terminal we have decided not to run a relay as our mill is unlikely to produce more than 20amps. So the load terminal goes direct to 2 x 24v 100w spotlights as the dump load. Works very nicely, you loose some of the functions of the PL20 but as a system it works very well. If you have any details you need let me know. Brett |
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Trev Guru Joined: 15/07/2006 Location: AustraliaPosts: 676 |
A lot of good advice. The PL regulator are a good choice. You can connect solar and wind with your PL20. My suggestion is to get another solar panel, and connect it in series with the other one, making 24v. Check outTrev's Diary Then connect the wind generator using the wiring diagram from Plasmatronic If you have trouble accessing, I can send you a copy. What wind generator were you looking at buying??? Trev @ drivebynature.com |
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| petanque don Senior Member  Joined: 02/08/2006 Location: AustraliaPosts: 212 |
Am I being simplistic but trimming some trees or moving the solar panel may be a cheap & easy way of improving the performance. Won’t the trees interfere with the wind as well? |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1448 |
Hiya Guy's, There's been lots of good adivce given above but no-one has mentioned that asumming those 75ah batteries are 12 volts 3 batteries wont hookup to make 24 volts!. Also I would recommend getting a few more batteries as it wouldn't take long to discharge those 3 batteries. Now personally I would mount the PV panel where the sun can have an un-interupted view of the panel. I have an 80 watt pv panel charging my nife batteries via oatleys old shunt controller modiefied for 16 volts and by the end of the day the dumpload (heating wire) is very warm. Now it's fair enought to have plenty of sun/wind charging a battery bank but with only a small capacity it wont take long to discharge them. Cheers Bryan  |
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| JPrel Newbie Joined: 18/02/2007 Location: AustraliaPosts: 6 |
Thanks so much everyone. Sorry for the delay in replying as I have been flatout at work. Some general feedback from all your input. The trees that surround my farm house as massive - 100 foot or so making it impossible to trim, and there are hundreds all circling 3/4 of the house which means that the current 12v panel doesn't get sun until about 10am, then loses the sun about 3pm. I could move the solar panel to get full sun, but that would be about 100m from the house and that I imagine would be disastrous for voltage drop. Funny enough I still get a fairly constant wind that howls through the trees, particularly at night as I am only 40k inland from the coast. So wind is pretty good. This is why I was thinking of the wind as another source of generation. Normally they mutually exclusive, so this should be a good co-sourcing arrangement I would have thought. The wind generator I am thinking of buying is a 24v one from Jaycar (http://www.jaycar.com.au/productView.asp?ID=MG4510&CATID=50 &keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword 2=&pageNumber=&priceMin=&priceMax=&SUBCATID=855). It doesn't have any regulator in it so I will look at the one suggested by Prof. I also take the point re the three batteries, I would need to buiy one more to make a series/parallel combination of 24volts. What is the general consensus re 12v V's 24v? My experiments last weekend certainly have shown me that voltage drop is a right pain in a 12v system. In the end I ended up moving the PL20 right next to the batteries and that fixed all the problems I was having. It took me hours to work out why my fridge kept cutting out. I worked out that I had about 0.3v drop across multiple cables and the end result was the fridge under voltage cutout was cutting in. Anyway I learnt alot last weekend in my trials and tribulations of wiring up the 12 volt system. On the other front of the DC convertor, yes I realise it would be a loss, but if I can't afford a 2nd panel and a the Jaycar generator, what would be best - a second panel (then no need for the DC-DC convertor) or the wind generator? I would have thought that the wind generator would give me more power than the panel, given the fact I get more wind than sun. Batteries, I have 3 x 75ahr batteries in parallel. From everything I have learnt, batteries in series are better than batteries in parallel as you ensure charge/discharge is even. I would be interested to hear that I am right on this - this I believe further supports my 24v aim (although I believe I would still have a series/parallel combination (2 x 12v in series with the same in parallel) unless the PL20 can charge to banks of 2x12v batts in series. Does anyone know? I measured the fridge and it pulls approx 10 amps on startup, then drops back to about 6 amps after 5 mins. Duty cycle seems to be about 30% on, 70% off. My simple maths tells me that it will draw 43.2ahrs/day (6amps x 24hrs x 30%). I have measured the current solar panel and under full sun it delivers 2.5amps into the system (as per the PL20 display). This means that on a good day of say 5hrs sunlight (10am - 3pm), the system would be putting in 12.5ahrs (2.5amps x 5hrs) of charge into the battery. Which roughly means I have to get 4 days solid charge to run the fridge for one day. Right? Currently I cant get more than 48 hours of the fridge running which I think equates to 86.4ahrs (2 x 43.2ahrs). The battery capacitiy is theoretically 225ahr (3 x 75ahr), so my assumption is that the batteries are never getting fully charged. Meaning that the solar panel can't charge them up enough, is this right??? I know it is a balance between power in (solar or wind), storage capacity and load. Now that I have the PL20 in place at least I can start collecting some statistics by using the logging function. This will help me understand if I need my power in or more storage. Thanks so much for your input guys, I would appreciate any more that you may have to contribute based on my revised feedback. Thank you so much. John |
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| Trev Guru Joined: 15/07/2006 Location: AustraliaPosts: 676 |
Yes, a 100m run would be disasterous for 12v. You say you only get 2.5 amps in full sun. How old is the panel?? Who made the panel, like what brand? Sharp and Kyocera 80 watt panels are rated at 4.7 amps. Perhaps another question is, what size cable do you run from panel to bateries?? If this is small then you just don't get full supply. With voltage drop to your fridge, I assume your wire size is too small??? Your calculations seem to add up ok, which means you need to look at more power production. I had a look at the wind generator in the Jaycar website you listed. If you would like a special price from me(for the same generator), then just email me.You can get my email from the windmill kits and parts page - Foundry & Fibreglass. You can connect it using your PL20 regulator. Battery capacity is ok, (& I meant to say before that to go to a 24v system you needed 1 more) and connecting parallel and series is ok. My opinion (12v vs 24v)is the higher the voltage system the better. Trev @ drivebynature.com |
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| JPrel Newbie Joined: 18/02/2007 Location: AustraliaPosts: 6 |
Thanks Trev, My panel is a 60 watt one, not sure the brand. In full sun I would assume I should get approx 5 amps out of the panel (I=P/E). The cable length from the panel to the regulator (PL20) is approx 8 metres. Last weekend I upgraded the cable size from approx 1.5mm to 4mm. I did not notice any increase in charge current after doing this, so I assume the old cable was OK. Oh well, better to be on the safe side. It would appear however that the panel isn't running at full capacity does it? Is there any way you would suggest to test it. Can I just short it out through an Ammeter to test the total max current output. Thanks for the offer to purchase the Wind generator through you. I do however have a friend that can get it for me through the Jaycar disctributor at cost, so it's probably the same price. Appreciate the offer though. Regards John |
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| Trev Guru Joined: 15/07/2006 Location: AustraliaPosts: 676 |
Hi JPrel, A 60 watt panel should be able to deliver 3.6 amps in full sun. You said that you have seen 2.5 in full sun. 5 amps is a bit greedy !. Not quite exactly watts/volts - where volts are battery volts. You need higher volts than the battery to get current (amps) to flow. To test the max amps capable, try a shorter heavier cable directly through an amp meter to the battery. That is, no regulator. Battery must not be fully charged. Not a good idea to just short out a solar panel,heat will be generated and possibly cause some damage. Hav'n Fun Trev @ drivebynature.com |
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| JPrel Newbie Joined: 18/02/2007 Location: AustraliaPosts: 6 |
Thanks Trev, I never thought about the current until you said that. I always assumed a 60w panel would put out 5A (60/12), but you are so right, it's actually a higher voltage to charge the battery, plus the voltage drop across the regulator. Hence if the batteries are being charged at 13.8 volts, plus 0.5 volt for regulator voltage drop, that means the panel is putting out 13.8 + 0.5 = 14.3. Therefore, in that circumstance the current I should see is 4.19A (60/14.3). Is this theoretically correct? Even so, the 2.5 amps that I am seeing is along way off 4.19A (only 60% of what it should be). Does age affect panel output? Thanks for your feedback Trev. John |
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Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Does age affect panel output? Take it from a disgruntled solar panel user, they sure do, and a lot. In one of my banks I have 6 x 75watt panels. Now they say these are good for 25 years, BP are suppose to be good panels. Right? Well I've had two fail (warranty claims). Gee Gill thats a 30% failure rate. Bad luck mate! At new you might expect 5Amps each, so that's 30Amp. At least thats the size regulator you MUST have. Now I live in Far North Queensland and that has the highest solar intensity rate( the sun passes directly overhead twice each year). So why have I never seen more than 25 amps. Typical perfect day gave 20 amps at best and usually 15 to 18amps typical. 10 years down the road and I'm getting 9 Amps. Wow 9 amps! You think I'm happy? 9 whole amps from 6 x 75 watt panels? I am pissed. Further background, the panels were bought over a 2 year period and are not from the same batch (serial numbers confirm this), and the wiring is 60 amp on a mere 3 meter run. Never used a concentrator though tempted to. So you tell me.. ? Sorry John if I have a little moment when I hear you calculating a 60 watt panel should give me more than 2.5 amps. Your doing better than me! Good Luck was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| Chipboy Newbie Joined: 13/12/2006 Location: AustraliaPosts: 16 |
A solar panel's output is measured at a point where voltage and current maximise output ie 60 Watts in your case. This voltage is typically around 17 or so volts and is NOT 12 or 14 volts. So the current you will see will be less than the ideal current at a voltage that is less than the ideal voltage, so do not expect 60 Watts on a 12 or 14.3 volt battery you simply will NEVER get that. A Maximum Power Point Tracking (MPPT) device is required to operate the panels at their maximum output point and then do a power conversion to your batteries or 240V AC if its an inverter. Then there is solar insolation (amount of light) and temperature derating (the maximum output is at 25 degrees, not the 50 or so it will work at in the sun) but that's another disappointment. Its all downhill. Sorry to rain on your parade. Matt Wind wannabe |
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