Solar panels, to track or not track (the sun) - Page 1
Forum section: electronics / general

author: Simon
author_rank: Unknown
timestamp: April 05, 2011, 06:40:42 am
content: Well since my last post about single solar cells I've been toying with the idea of tracking the sun with solar panels/cells. Now the obvious came to mind: when they tilt they will start to shadow each other. So I started on the assumption that I would need to track across 90 degrees (45 each way) and did a sketch. It seems that I will have to space the panes at 50%. Now as tracking gains another 30-50 % surely at that point I might as well just forget the tracking and cover the entire area ? I mean panels and cells are getting ever cheaper and the "extra" expense will be offset by the savings in tracking mechanisms.Anyone ever dabbled in this ?

author: dimlow
author_rank: Frequent Contributor
timestamp: April 05, 2011, 07:26:28 am
content: Not dabbled in this , but have dabbled in astronomy. If your tracking the sun you not only have to think about the earth rotating about it axis,but also about the the earth rotating about the sun. The earth is tilted when it rotates around the sun the hight of the sun also changes relative to the earth during seasons. The position of the sun changes in relation to your position on the earth at a particular time and date.Because of that load of tosh id say stick um static as the tracking could be quite complicated!

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 05, 2011, 10:36:16 am
content: Quote from: Simon on April 05, 2011, 06:40:42 amsounds like a science fiction. or perharps i dont have detailed explanation.

author: johnwa
author_rank: Frequent Contributor
timestamp: April 05, 2011, 10:54:42 am
content: Quote from: Mechatrommer on April 05, 2011, 10:36:16 am'Tracking' is just using a motor or something to aim the panels at the sun, so they generate more power.Simon, I think there are a number of issues to look at with tracking. You probably need to look at what is the most cost effective means of generating the amount of power you require - adding tracking, or simply getting more panels. There is both the cost of the tracking hardware, and the energy 'wasted' in running it - both of these will probably be proportionally greater with a small system.Then there is the issue of reliability - you take something with high inherent reliability, and introduce moving parts, with the potential for breakdowns. Regarding the spacing, most systems mount all of the panels on a large frame, which moves as a unit. This obviously has to be designed to withstand high winds, etc.I think it only really makes sense when the installed cost of the panels is very high (space stations etc), or where the installation needs to be compact.How is your MPPT design going? I have found an article for a simple analogue design I can send you if you like.

author: Simon
author_rank: Unknown
timestamp: April 05, 2011, 11:43:24 am
content: yes that's what I'm thinking, with the added complication of making each cell into it's own panel and making all of the tilting mechanisms yes still end up with lower surface area annulling the gain. it is easier and cheaper to use fixed panels.Well I'm currently using a MTTP GTI but am interested in developing my own MPPT controller for a battery, any info most welcome

author: alvarop
author_rank: Contributor
timestamp: April 05, 2011, 12:40:05 pm
content: Have you seen the passive trackers? No gears!http://en.wikipedia.org/wiki/Solar_tracker#Passive_tracker

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: April 05, 2011, 01:08:05 pm
content: My friend has been doing some research for a large array of panels, probably at a similar latitude to you (47 degrees north). He looked at reflectors in the vertical plane but eventually decided that tracking in the horizontal plane (i.e., rotating around a vertical axis) was the best answer. I don't have any numbers to back up his conclusion but I suspect in part it's based on requiring less structure to accomplish.

author: FxDev
author_rank: Regular Contributor
timestamp: April 05, 2011, 04:42:19 pm
content: I'm working on that.You have not or shouldnt do that. Do you know about your position, N/S or W/E? Yes so do like that.For exmp. My position is 66° 33? 44? NSo your panel angle must be 66° 33? 44?. If you live in north, panel angle can be 56° 33? 44? in summer, 76° 33? 44? in winter.And if you live in north your panel must turn to south.That's it.So save your money, dont buy tracking system with that power.But if you want to generate 10MW, so you can use

author: Simon
author_rank: Unknown
timestamp: April 05, 2011, 05:10:17 pm
content: Quote from: alvarop on April 05, 2011, 12:40:05 pmwould still require "gear" to make it all move.I was thinking of swinging the whole 3 meter length but soon put that out of my mind because I'd be turning 1.5 metre arms that wound cover a lot of ground (my neighbour and overhand my garden) so again in order to have room for that I'd be reducing panels so might as well fill the maximum space with panels, they are now cheaper than the mecanics

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: April 05, 2011, 06:21:39 pm
content: I have a 12.5KW solar array at home and after a lot of consideration of alternatives, I decided to go with a fixed system. The panels face SSW and are fully illuminated by the early afternoon sun. These are large panels, and the cost of a sun tracking system would have more than doubled the (already expensive) cost of the system.

author: tecman
author_rank: Frequent Contributor
timestamp: April 05, 2011, 06:32:16 pm
content: I've been working on solar tracking for the last few years (job work). You can see up to 28% increase with tracking. However the cost of adding tracking for anything than a small panel can be a key factor. Remember that the tracking mechanics must not only hold the static weight, but also wind loading. This is generally several magnitudes greater than the weight alone. Also the power for tracking can also be a consideration in larger installations. All of this really pushes the cost up. I am currently installing 9.2KW of PV and discounted tracking due to the costs. It would push the payback to over 20 years.We are working on systems that have 2000-3000 trackers with a controller at each tracker. These are utility scale systems and tracking accuracies are +/- 0.1 degrees. Fun work with challenges in networking, parasitic power draw and operational reliability.paul

author: Simon
author_rank: Unknown
timestamp: April 05, 2011, 09:45:41 pm
content: only 28% increase ? well for that I can get 50% more [anels in with fixed mount and be quuids in. Yes wind is my big enemy. that's why I want to make my saystem with individual cells and make long thin panels so that they have little wind frontage and are broken down into smaller fixtures rather than a huge sheet that needs industrial grade mounting

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: April 05, 2011, 11:03:31 pm
content: Quote from: Simon on April 05, 2011, 09:45:41 pmDon't underestimate the force of the wind. You need to determine what the worst-case winds in your area are likely to be and engineer the system for that, plus a generous safety margin. Concrete and steel are your friends here. It will be expensive, yes, but cheaper than replacing damaged panels and any collateral damage caused by the panels flying into things in the vicinity.Another thing to keep in mind is security. Some dickhead stole six of the 80 panels that make up my system, and at $900 per panel, the replacement cost was rather dear. Now I have a monitored video surveillance system watching the array 24/7.

author: dimlow
author_rank: Frequent Contributor
timestamp: April 06, 2011, 01:08:07 am
content: How much loss would you get if you just mounted them flat on a flat roof ? Wind would then not be so much of a problem im guessing.

author: AdShea
author_rank: Contributor
timestamp: April 06, 2011, 03:08:35 am
content: If you do the math, you'll generally get more power/land area (kWh/acre or kWh/km^2) with static panels as the extra spacing you need to keep from shading cuts down on your power even though you use your active area more effectively.As for installed cost, it all depends on what grade of cells you're using, and how much your mechanicals cost. Don't forget the maintenance cost/hassle for moving parts exposed to the elements.

author: Lance
author_rank: Frequent Contributor
timestamp: April 06, 2011, 06:14:47 am
content: Would it not be easier to spend the money on more solar panels and increase your total power output?

author: Lightages
author_rank: Unknown
timestamp: April 06, 2011, 06:16:36 am
content: I have a solar system running here in the desert in Chile. I have 9 x 205W panels. Each panel costs me about $700USD by the time I get them here to Chile. If I wanted to increase my solar collection, it would cost me either around $1500-$2000 for an active tracking system (home made) for around 30% gain, or around $2100 for another 3 panels that would give me around 33% gain. The active tracking system would require maintenance and maybe would cost me more than I have estimated. The extra panels are "connect and forget". It seems clear to me that for my setup more panels are a better choice than tracking.I would say that for most setups, tracking does not make much sense.

author: Simon
author_rank: Unknown
timestamp: April 06, 2011, 06:59:05 am
content: Quote from: Sal Ammoniac on April 05, 2011, 11:03:31 pmI'm going to mkae my panels from 3.25X6 inch cells and make them one row high and rather long. That way I've got minimum surface area for wind and each row is seperatly fixed down rather than one large panel with a single set of fixings. That way it is low profile and a low load on each mount. Hopefully mine won't be strolen, it is just 6sq meteres and I suppose being home made won't be worth much unless they are after the cells inside but they are cheap enough to buy.

author: Hypernova
author_rank: Unknown
timestamp: April 06, 2011, 10:30:12 am
content: A few years back in Time I read of a company that did thin films wrapping their panels around rods, they are then set horizontally a meter off the roof. Pretty much the fuck-the-tracking-I-got-the-roof idea taken up to eleven. The efficiency on that set up must have been horrendous.

author: Simon
author_rank: Unknown
timestamp: April 06, 2011, 10:37:59 am
content: well it's all about maximising the area you have available, I'd happily trade efficiency for having more constant power throughout the day

author: PetrosA
author_rank: Frequent Contributor
timestamp: April 06, 2011, 12:52:41 pm
content: The rod systems (Solyndra etc) are designed for flat white rubber coated roofs where you get a lot of reflected light from below. Nowadays they sit about 30-40 cm above the roof and have very little lift requiring much less hardware to hold them down.Typical panels are bolted down like crazy both for wind lift and seismic stability. In addition, the entire mounting frame structure has to be carefully bonded to the earthing system in case of lightning strike. For roof mount systems, it's good to get an engineer to check the roof framing (required in many areas) to make sure that it can handle the lift forces.For your small, home made system, you probably can get away with engineering something yourself, but keep in mind worse case scenarios like a fire in the structure and how you or someone else will disconnect the panels, fusing and/or ground fault protection of the system, strong winds (during storms they can reach 60-70 mph or more), etc.

author: Simon
author_rank: Unknown
timestamp: April 06, 2011, 01:20:35 pm
content: well that's why I'm making them small so that I have less wind force per fixing. I'm not sure how to hold it down to the roof as although it's flat concrete i guess that drilling holes in it for screws will just lead to water ingress and roof damage.I suppose it will end up looking like a miniature solar station will lots of rows of small panels rather than one large one.in the event of fire which should not happen, well it's a concrete roof won't burn the house down. Naturally I'll fuse it etc

author: Lance
author_rank: Frequent Contributor
timestamp: April 06, 2011, 04:48:14 pm
content: Quote from: Simon on April 06, 2011, 01:20:35 pmWater is a major issue. Unless you were extremely careful to seal up everything as you went along.

author: Simon
author_rank: Unknown
timestamp: April 06, 2011, 05:07:42 pm
content: yes quite, I'm considering weighing it down and maybe fixing to the side wall just to make sure. I'll be looking deeper into the fixing though as that is the one thing i need more infor on as I don't want to ruin my outhouse roof

author: PetrosA
author_rank: Frequent Contributor
timestamp: April 06, 2011, 11:40:44 pm
content: Quote from: Simon on April 06, 2011, 05:07:42 pmI'm not 100% sure what your roof construction looks like, but I would think epoxy and threaded rod in holes would be a possibility for you. Just make sure you use stainless hardware up there

author: apex
author_rank: Regular Contributor
timestamp: April 07, 2011, 02:13:31 pm
content: Here is a quite good article about different techniques you could use:(german)http://www.mikrocontroller.net/articles/Sonnenfolger_/_Heliostat(translated)http://translate.google.de/translate?js=n&prev=_t&hl=de&ie=UTF-8&layout=2&eotf=1&sl=de&tl=en&u=http%3A%2F%2Fwww.mikrocontroller.net%2Farticles%2FSonnenfolger_%2F_Heliostat&act=urlapex

author: Lance
author_rank: Frequent Contributor
timestamp: April 07, 2011, 03:00:45 pm
content: Quote from: PetrosA on April 06, 2011, 11:40:44 pmPictures would help. Then we could see what's there to work with.