Respectfully I'll have to take Myles to task here;) The important thing to me is to look at the maximum output based on STC ratings for your given 2 D footprint.
If you look at the 135 Sunpower link you'll note the panel dimensions are 1.435 by 0.540 m. Now we need to work out the effective STC output rating per square metre. 1.435 x 0.540 = 0.7749 sq m. So dividing 1 by 0.7749 we get 1.290489095367144. Now times that by the STC rating of the panel of 135 and we get 174.2160278745645 watts output under STC per square meter for a 22% efficient cell. Now do this with some less efficient cells and you begin to realise some rules of thumb.
Look at your actual available flat solar footprint on your vessel and in general use the largest size and therefore the minimum number of panels to fill that footprint with the greatest output per square meter.
So if for example you take a Norwegian Crystals 280 Watt rated panel:
Norwegian Crystals Noor BLK 280W MCS NC-280MP60/B Noor 280 Wp, black frame, black backsheet £241.23 Ex VAT (look at that output and price compared to the Sunpower).
ebay Sunpower 135 is 269 US dollars and converting to pounds (x 0.66) is £176.80 whereas the Nor Crystals is 280 Watts for £241.23 Ex VAT which plus 20% VAT is £289.476. So immdeiately you can see the Nor panel is more than twice the output for less than the price of 2 Sunpower flexis. Also I think Flexi will not last as long as rigid.
http://crystals.no/products/noor/
280 Watts 1660 x 990 = 1.494. 1 divide by 0.67 x 280 = 187.42 Watts per square metre.
So the output for that panel under standard test conditions per square metre is greater than the Sunpower flexi 135 panel.
Even in my case using 13% efficient cells in a low light Mono 100 Watt panel I have an effective 153 Watts per square metre. Enough for me without going to the expense of expensive cells.
Now after doing a cost per sq metre too, you may decide that Sunpower is just not worth it and you need to think about vertical panels in addition as a much more cost effective way.
In fact this all harks back to an article I wrote for Electric & Hybrid Marine Technology International a few years back. And in fact the tech now exists to do this.
Personally and depending on your lat/long I think unless on the same tack for a long time that the weight/complexity of a tracker is simply not worth it, plus of course the added windage. Sailing here round the islands of Scotland I'd have to readjust the tracker around every 30 minutes or less! Why not consider for your footprint vertical solar too?
Using panels in two fixed planes can have a dramatic effect for a given 2D footprint in terms of output and cost or bang for you buck as you US folk say. The best (but expensive) example being the dye sensitised solar cell cloth being used on the Arcona 380Z in the main sail. Add to that solar strips on the boom and mast and you can see how we can achieve decent outputs. If solar clotth is unafforable then an array if possible of inexpensive flat and vertical panels may be the best.
Also much of this depends on your lat/long. Here at 55 degrees North on the west coast of Scotland the best I'll see in the Summer months with my Victron MPPT is 5 times the STC panel rating, plus of course with edge of cloud effect etc we can even exceed STC panel ratings.
It is also worth bearing in mind an earlier discussion and my ref to matching panels to your MPPT and using a much higher panel voltage in series than battery voltage. Especially with vertical panels you'll start charging earlier and finish charging later in the day (longer overall) as the MPPT will be above the required +5v over battery voltage earlier in the day and continue later in the evening. With a flat panel here I may see 10 hours of charging in Summer and a max of 5 times panel rating. i.e. 5 hours of peak sun. Average is about 2.5 times panel rating for me.
As regards MPPTs I favour Victron as that is what I use. As previously said do try this link:
http://www.victronenergy.com/blog/2014/03/28/matching-victron-energy-solar-modules-to-the-new-mppt-charge-regulators/
and use the spreadsheet in which you can enter your own panel data:
http://www.victronenergy.com/support-and-downloads/software#mppt-calculator-excel-sheet
This will show you how high voltage and panels in series can help, but of course being mindful of shading.
If your boat is long enough too and can sail at around 7.5 Knots, then depending on your electric setup you'll likely get 500 Watts hydro gen. My 8m/26ft boat is sadly too small for hyrdo/regen to make any significant difference.
All food for thought I hope....
John Rushworth
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a New Topic | • | Messages in this topic (8) |
No comments:
Post a Comment