Energy Matters Forums

[Tracker]

Whilst you don't have to be Einstein to adjust an array having Inclination Adjustment, there is likely an angle below the Zenith, where the total days output is likely optimum. The presumption is that this optimum varies with the years-seasons.

The sun rises low and sets low. If the panels are set to the noon zenith, then one get the highest possible output at that time, but then it falls off at other times. A full Sun-Tracker system will naturally give peak output at all times, resulting in absolute maximum daily totals

Is there an experimentally determined and season variable angle - BELOW the sun's Noon Zenith - where the days average is at it's highest.. ie. higher than adjusting the array purely on being perpendicular to the Noon-Sun-Position?

[BlueSky]

Hi , Im not sure if this will help but heres a link to a free design tool that you can play around with the Azimuth and alot of other varyables and see the added or reduced benefit............

http://www.sma.de/en/products/software/ ... esign.html


Its really quite surprising ....I found that for my North West facing situation, the ideal panel angle was only 20 degrees....not the 30 thats recomended for my latitude....
hope it helps...cheers

[Tracker]

Thanks BlueSky for the hint on the Software Tool.. I had a little play, but it does not seem to do any more than to provide "Peak-Design-Parameters".

I presume that you are saying that the inclination of 20 figure is based on FIXED rather than variable "Inclination Adjust-ability"
In a normal installation, where adjustment is not practical, then one goes for what you can work with.

My engineering basics would suggest that there must be a big difference between Summer and Winter IF one has the capacity to Inclination adjust.
If I adjust for seasonal Noon-Peak, when you get the peak return for the day, then the AM/PM averages will be lower, as the sun traverses the solar arc, which is all LOW in winter and far higher in summer
I would expect that the winter change from AM>Noon>PM would not be as great as in Summer, hence my presumption that somewhere below the Summer Zenith must give the best total for the day..
Anyway I will play with the software. Otherwise I'll just have to experiment.

[domhenry]

Guys

You might also find this tool useful: The PV Watt Photovoltaic Solar System Performance Calculator at

http://www.pvwatts.org/

There are a number of other useful tools there too. Although from the USA it can ne confirgured for Australia - and the orientation angle is based on the direction to the equator so still works.

Dom

[mick_queensland]

Hi,

just trolling through posts and noticed this one.
I saw a web page last year while researching stuff and I thought this it may help someone else too.

http://www.macslab.com/optsolar.html

Cheers
Mick

[Tracker]

.
Thanks for that reference !
I have to say that it supports what I had thought, and had found in practice.
It's nice to see a more academic presentation there of.

In short, adjusting the tilt twice a year gives you a meaningful boost in energy. Adjusting four times a year produces only a little more, but could be important if you need to optimize production in spring and fall.

That sums it up.. That confirms what I thought I was seeing..
..
.

[mick_queensland]

Hi Tracker,

glad that info helped. It helped me quite a lot while I was doing all my calcs and research last year.
Mac puts it very succinctly and its nicely graphed out too.

Cheers, Mick

[Tracker]

BTW...
For anyone not sure what the outcome of the question was, the referenced presenter declared...

Solar panels should always face true NORTH if you are in the SOUTHERN hemisphere.......
Books and articles on solar energy often give the advice that the tilt should be equal to your latitude, plus 15 degrees in winter, or minus 15 degrees in summer.......
But because the sun is higher in the summer and lower in the winter, you can capture more energy during the whole year by adjusting the tilt of the panels according to the season.....
SO..at what angle from HORIZONTAL should the panels be tilted?

The benefits have been calculated to be...

......................Fixed Adj. .....2 seasons Adj........ 4 seasons....... 2-axis tracker
% of optimum........ 71.1% ............75.2% ................75.7% ...............100%.....

Now I must say that I would love to have had the complete picture, and seen what a 1-Axis Tracker might have achieved..
( but perhaps, the figures would suggest that a 1-Axis-Tracker might achieve 75.76512% )

(Panels that track the movement of the sun throughout the day can receive 10% (in winter) to 40% (in summer) more energy than fixed panels.

Gordon has oft'-said the practical relationship between FIXED and Full-TRACKER ..IS.. 30% improvement, SO

If your latitude is between 25° and 50°, then the best tilt angles are:
....•For summer, take the latitude, multiply by 0.92, and subtract 24.3 degrees.
....•For spring and autumn, take the latitude, multiply by 0.98, and subtract 2.3 degrees.
....•For winter, take the latitude, multiply by 0.89, and add 24 degrees.

and just repeating those change-overs...

Adjust to summer angle on October 18
Adjust to autumn angle on February 23
Adjust to winter angle on 7 March 8
Adjust to spring angle on September 4

I must admit that the reason for these dates escapes me ... I suspect that one will find they correspond to intervals compared to Winter and Summer Solstice-susses ... ... being 21June and 22Dec...

These adjustments correspond to:

....•For Summer................ 6.52
....•For Spring/Autumn....... 30.53
....•For Winter................. 51.17

So - how do these figures campare, for those who have really studied the BEST angle-of-dangle..?
( and have the Mathematical prowess to prove it..)

How would you change things and what would be the result??
..
.

[Gordon-Loomberah]

( but perhaps, the figures would suggest that a 1-Axis-Tracker might achieve 75.76512% )

The author doesn't seem to know about proper equatorial mounts (as used for telescopes), that track by rotation around 1 axis- which is parallel to Earth's axis. That's what I have for my large array and it produces 100% of the potential power available.

(Panels that track the movement of the sun throughout the day can receive 10% (in winter) to 40% (in summer) more energy than fixed panels.
Gordon has oft'-said the practical relationship between FIXED and Full-TRACKER ..IS.. 30% improvement,

That 30% is only a typical value, which includes heavily overcast weather, when my tracker faces the meridian, essentially the same as fixed panels tilted to point at the Sun's declination. In sunny winter weather, the improvement is far greater than the quoted 10%, so I dont know where that number comes from. See this thread http://forums.energymatters.com.au/solar-wind-gear/topic2772.html for some discussion of the winter gains to be had with a tracker.

[Tracker]

The author doesn't seem to know about proper equatorial mounts (as used for telescopes),

To we simple mortals, it does get confusing..
I am assuming that you mean 2-axis tracking, such that I could focus on a point in space and track it completely, as distinct to 1-axis tracking (vertical) and 1-Axis (vertical) adjustable.. as is being highlighted by the discussion.

The author excluded 2-axis trackers, I suppose, because they are a significant device, that is generally unachievable in 99.9% of city installations..

Gordon - do you have a Mathematical feeling for the difference a 1-Axis (vertical) tracker would make...
I have often thought how easy it would be to make infinitely adjustable struts..
BUT at what $ cost.. for a minimal gain..
ie - if the author is correct and the advamtage of FIXED over ADJUSTABLE is only about 4%, then why would anyone worrie, except where EVERY Watt counts.. As I hypothesised - would INFINITELY adjustable vertical tracking, simply increase the benefit from 4% to 4.5% ?
..
.