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Forum Index : Solar : Solar Panel Angles and Tracking
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Madness Guru  Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I am in the process of buying a property which has no grid power available and will be relying on solar as the main source of power. My main question is which is the better way to go between permanently fixed panels (and what angle), seasonally manually adjusting the tilt angle and building a dual axis tracker? I will need to add more panels to my current system regardless of which way I go it will be a matter of how many. What ever panels I buy will most likely be second hand to keep costs down. To complicate matters in winter sunrise will be around 8 am and sunset about 3 PM due to the terrain and trees which can not be removed. To get the most sun I will also need to put the panels about 80 metres from the existing house. At present I have 2.8 KW in total of solar panels, I would like to double this as it is not enough to cover all of our present use. The site is also high up on the escarpment of the range in the Sunshine Coast hinterland and has high rainfall. I don't expect to get 100 percent of our power from the solar in wet weather periods. But would like to be able run totally off solar when there is fine weather with some extra margin to keep batteries topped up. When needed I have 8 KVA Diesel generator that can be auto/manually started from the Trace Inverter Charger. Some of you may say try to cut down on use but our present power consumption is around 14 KW hours per day. Some of this usage will reduce by replacing our present fridge (4.4 KWH per day) I can get a new equivalent that is around 1.8 per day according to the manufacturer. Also the Plasma TV which uses about 350 watts on average which gets used 2 to 7 hours per day depending on when kids are home or at school. This will be getting replaced by an LED soon. Cooking at present is all electric but that will be gas at the new place. Hot water will be solar with a backup from the wood heater. Wind is not really an option on this site however there is a good possibility for hydro during rainy periods only. There is about 40 metres of fall available and I plan to build a large dam at the highest available point of the gully anyway. Any comments/suggestions would be appreciated thanks. Gary There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
Unless you want the "fun" of building a tracking system, I'd stick to fixed panels with the tilt angle set to local latitude and facing north. I got about 20% more power being trackable with very little effect by adjusting the tilt. Much easier to fit 20% more panels and be done with it. Is the system 24 or 48 volts? 48+ would be better or the 80mteres of cable is going to be fairly hefty in size. David M. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
The system is 48 volt but panel output voltage is normally about 85 volts before it goes through the MPPT charge controller. I can buy insulated power line cable from the local scape metal guy at a reasonable price, he has got a roll there at the moment which is 3 phase plus earth, so 4 wires with about 5 mm diameter copper in each. According to a on-line calculator I will have about about 3% loss. It's rated for at least 415 volt with 2 layers of insulation on the outside so should be fine. The property is 26.4 degrees south, if the panels are fixed I am thinking I would want to try to optimise it more for winter than summer. Also as there is an early sunset would it be better to face a little east of north? In order to get the panels up as quick as possible I would be building a dedicated frame to put them on rather waiting till I build a shed there. Time is in short supply for a while too so building a tracker would have be in the future if I went that way. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
Gotta agree with Mobi here, go with fixed facing north at latitude tilt plus, if you have the batteries & regulator close to house and use a regulator that allows you to serial wire your panels to a high voltage, something like the Outback that lets you feed at 120 volts thus less cable loss. You`ll need more than one array so have an switched circuit breaker on each, that allows you test each array occasionally by switching each individual array off and checking input current. But really build a little enclosure under panels with batteries and inverter and run 240v to house, if possible, bugger-all line loss then. We come from the land downunder. Vic |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I am using a Outback MPPT controller, maximum voltage is 150 so need to keep it well under 120 to avoid over voltage in cold conditions. I want to keep the Inverter close to the house so that I can use the remote control which has a limit of 16 metres for the cable. This is so the generator can be started/stopped at a push of a button when the sun is not shining so much. For example if my wife wants to put a load of washing she can just push the button to start the generator rather than draining the batteries. If I was running the 240 AC that far I would still need to allow for 30 amps from the generator to run my welder. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yep agree with Mobi too. My panels face north, mounted on the shed roof. When I bought the place there was no house or shed, so when I bought the shed, I positioned it with its roof faced true north. Made mounting the panels much easier. Tilt the panels to favour the winter sun, thats when you need as many watt hours as you can get, in summer you have an abundance of sunlight so angle isn't as important. Trackers can break down, need maintenance, and you need to worry about wind loading. Its easier to just buy more solar panels, they are a lot cheaper these days than they were a few years ago. Also worth considering adding a wind turbine for those overcast windy days. On some days my turbine is making more than the solar panels, and it means I dont need to budget on power while the weather is yuk. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Wind turbine would be nice but the property is in a little valley hence the late sunrise and very early sunset. It is about 100 metres below the top of the range which rises up fairly steeply. So there would be virtually no wind from the west and from the east there is ridge that would limit wind from that direction. That is why I may put in a hydro system, it would only work in wet weather with run off from rain. If I add a second Outback controller that would allow another 4.2 KW of panels which would give me 6 in total which should be enough for most of the time. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
I'm still not convinced on the worth of a small wind turbine. Mine is an OEM 500watt job (modded by downwind) which spends 99% of its time doing virtually nothing. It is supposed to be windy here, but too often when we get days of overcast, we also get calm conditions and so, no sparks! Mind you, if you can make a decent one or buy one very cheap, it might be worth while. I originally started with a 400w AIREX and I don't think it did anything and eventually totally disintegrated in strong winds. An expensive failure. If you only have a small PV array, rotating the array as one is not too difficult to achieve but if you have a few Kwatts of panels, you need to rotate each panel or groups and end up shading the adjacent panels, requiring more separation. If north-ish facing and variable tilt required, it wouldn't take too much to fit a tilt bar with bolt holes to alter the tilt. Even only two positions to accommodate summer and winter.?? I think you won't get too much difference in output for the two times of the year. But then, I am nearly in Antarctica (Millicent SA) and you are getting tropical.  David M. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
The panels I have are set up at the moment flat on a carport roof. Output is down to 2 KW maximum, they made 8.2 KWH's today with some cloud. In summer I was getting up to 18 KWH's I know there is less hours in the day now, but sitting flat as they are at present certainly has reduced there output. My experience with the Dunlite generator in my avatar was that it did not do well due to turbulence even with lots of wind at that site. This new place has ocean views to the south east but to the west is a steep 100 metres high slope. I would be surprised if wind would do much there, so it this stage I am disregarding it till I am living there and get a better feel for the wind conditions. There will be long periods of wet weather and that is why I am thinking of putting the hydro. As I will most likely put the panels on a dedicated steel frame it would not be too hard to add 3 angle adjustment positions for the seasons. I need to get them up ASAP once we taken possession of the place. There is a 24 volt solar system there now but it is old and last time I looked it was only making 10 amps. Just enough for the guy there now to run a couple lights and a bit of stereo. Our climate might seem tropical compared to yours Mobi but we are still 1700 KM south of Cairns. Here it is subtropical and mostly doesn't get too cold or too hot to complain about. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
From Mobi, to you and Gizmo and them up here in NQ. Fixed panels probably produce the best average at my location almost flat, with summer being when most output is needed in NQ because of refrigeration loads, length of day not so important in NQ, the isle we live on is massive, the setup of solar varies so much at our varying latitudes to get that max efficiency. No one answer for all of us, will be interesting to follow your progress with time Madness as tis a new and rewarding concept being power dependant. Very rewarding. We come from the land downunder. Vic |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Solar panels are pretty forgiving the sun needs to be at 20 degrees or more angle to the panel surface before the efficiency really starts roll off. the rule of thumb is the optimal fixed angle is the same as your latitude. So if your lat is 26.4 then the panels generate the most power over the year at 26.4 degrees from horizontal. In this case I would stand them up an extra 5 degrees, total power for the year would only be down less than 1%. You can put the generator and an auto transfer switch anywhere you like as long as the 240 volt AC from the inverter runs only to the transfer switch and the generator is on the priority connection, having everything else close to the panels will give you a lot more flexibility with wiring those extra banks. I'm confused, no wait... maybe I'm not... |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Thanks Yahoo2, interesting that up to 20 percent off is not a issue. The Inverter I have is a Trace SW4835 which is also a charger and has 2 inbuilt transfer switches. Although they are more than a transfer switch as the inverter sync's with the generator before gradually transferring the load across. It also has a generator support capability too to supply power from the batteries/panels if the load is greater than the maximum generator current setting. It will be easier to keep them close together as there will be AC from the generator to the inverter as well as control wires between them. Also I want the remote control panel for the inverter inside the house, it can only be a maximum of 8 meters away. This will be better for the batteries so my wife can start the genny to do washing, ironing etc in wet weather. Otherwise if the generator and inverter is 80 metres away it won't get started when the weather is bad. Norcold, this is not my first experience of being off grid although my previous set up relied heavily on a generator with no solar (back in late 80's) and wind that did not normally help a lot. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Looks like that side of things is pretty locked down. Only thing I could suggest is there may be some room to tweak the panels depending on what you end up with. I have run 8 strings of 3 panels (72 cell, 5 inch cell)to an 80 amp controller, as long as each string of three panels is a reasonable match that string will produce the wattage of the weakest panel. I had 185's through to 215 watters. if you are still worried about Voc on those rare super cold days, I see that the midnite solar 150 can be bought for under $1000. they will let you go to 150 volts plus the battery voltage for Voc (adjusting panel Voc for cold conditions)it gives you some extra headroom, I am not sure that it will charge in these conditions but it wont damage the controller. with the line loss to the house taken into account you could average 205 watt per panel and still stay under 4800watts total for a new bank. edit http://www.midnitesolar.com/images/classicFrontPage/graphs.p hp I'm confused, no wait... maybe I'm not... |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
At present I have 16 identical panels that produce just short of the maximum current allowable on the Outback MX60 charge controller. So I won't be doing anything to change it's current panel configuration. When I add more panels I plan to use a Outback FM80 controller as it can be linked to the MX60 so they will talk to each other. I would be trying to keep any new panels all the same on the new controller. Having 200 volts 2 play with would be nice but my understanding of the MPPT controllers is they work more efficiently if the panel voltage is not too much higher than the battery voltage. Maybe the losses aren't that great has any one got any comments on it? There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| kitestrings Senior Member  Joined: 23/04/2014 Location: United StatesPosts: 102 |
Madn, I agree with most of what's been said already, except of course being ~20 miles from the Canadian border we tend to face things like this south 
There's a tracker manufacturer in out state (and VT is small). They make I good product, but I've long questioned why you'd want to complicate something that works so well without moving parts. And, from a cost perspective if you put the tracker money into more panels, I think you're better off. We had a real small array for awhile that I pivoted spring and fall. Just my admitted bias. Regarding the wind - and we've lived with both for nearly 30 years - in the right site it can be a real compliment to the solar. Here we get great winds in the late fall, winter and spring, then the solar kicks in and it doesn't much matter. Ours will be mostly shut down, but we also get lots of cloud cover, and snow. For an off-grid home this only leaves a gen-set; not ideal. Your site may have different attributes/sources to consider. We have both OB & MS charge controllers. Happy with both, but the MS has some added flexibility and the support is first-rate. Best, ~kitestrings |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
my personal opinion is that panels only have to be identical wattage on the same string, if you take the time to look at the different efficiency panels in the same cell size and configuration you will see there is usually almost no difference in the voltages, I cant provide any scientific info links to back this opinion up, just my own observations. I am just noting that your total capacity is going to be 7 Kw when the potential limit of the two controllers would be 8 Kw. if you are reluctant to fiddle with your existing panels and get them closer to 3.2 Kw, fair enough, but I dont understand restricting yourself to 4.2 Kw when there is some upside on capacity. As to linking outback controllers.... not convinced, my understanding is you will need some pricy communications gear to get them to work together. I prefer to let one solar bank do all the topping up and equalising and set the other controller at a slightly lower absorption voltage if its running WLA batteries. The link to the graph I posted previously should tell you all you need to know about higher voltage MPPT and bank sizing. The panel I used in my calculator (for a string of 3 panels) give me a Voc @ 25 deg C of 115 volts so that equates to 92 working volts on the graph (4800 watts 83 Amps)and the Voc @ 1 deg C was still under 150 volts but only by a small margin. PS forgot to say before, 1.8 Kw for a fridge seems a lot, surely that is for a fridge/ freezer pigeon pair around the 900 litre mark? I'm confused, no wait... maybe I'm not... |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
My current panels and controller are 320 watts short of the rated maximum of the controller. Changing that set up with 16 identical panels would mean some fiddling around. If I get 2 more panels the same I could change it to 6 strings of 3 instead of 4 X 4 as it is now. However with a second controller with 4.2 KW I think I should cover our power requirements. Just check and the FM80 is rated at 4000 watts at 48 volts that plus 3200 from the MX60 gives a total of 7.2 KW. 1.8 KWH per day is for a new side by side fridge freezer with ice maker. I am not interested in anything less. There is a Panasonic which uses much less but it is not available in Australia. I will look further at the Midnitesolar controllers, though I have had a good run with the outback and feel comfortable with it. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
Gary, I agree with the guys above - a tracking system is a great idea and challenge to impliment but a fixed system is a good initial/simple system to configure. There are a number of factors to cosider however, not the least (and often overlooked) is the daily load profile. Typically, breakfast involves toasters, coffee makers etc. as well as recovering overnight losses so a north east/east facing array will return most power. Lunchtime, more coffee, some cooking, maybe a load of washing, but hopefully, little battery recharging at this point, so North facing is best. Finally, afternoon/evening, dinner, tv, and lighting, north/west facing to extract the most of the afternoon/evening sun. Thus, based on a real live site in southern WA, I created the xls spreadsheet attached to help calculate how many panels and in which direction would give the maximum power into the load/batteries. Note that as most houses have either a single north facing roof (or if a gable is involved, an east and west component which is the ideal situation and is used in the spreadsheet) you have some limitations on maximising results. Note: For our northern hemisphere friends, please replace all references to north with south! Hope this is of interest, Doug. PS. Struggling to include .xls as a zip - will work on it! ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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| panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
Can't seem to include file in Android tablet - going back to MS. 2014-07-02_125416_Solar_Array_Configurator.zip How easy was that - Android says Choose File but nothing happens! Sadly, Firefox under MS7 works a treat. Cheers, Doug. ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Received a PM from neil0mac regarding tracking, however can't reply as your inbox is apparently full Neil. Hi Neil, The link to your PV output is impressive, particularly in the mornings. I have been advised that tracking is more trouble than it is worth when you consider adding extra panels rather than out laying money for a tracker. However if I could build a reliable tracker at a reasonable cost I could easily be swayed. I am quite proficient with welding, electrical, electronics and have dabbled a bit with Arduino's If you can point me in the direction of a cost effective design I could build I would appreciate it. Thanks Gary There are only 10 types of people in the world: those who understand binary, and those who don't. |
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