solar angle

[Seeb]

What is the right angle for solar panels here? none of the books ive read have hawaii in them.

[mikewj]

Hilo is at 19 degrees 43 minutes N Latitude. Check the chart at this address for the correct angle of tilt.

http://www.oksolar.com/technical/solar_p...ation.html

[Seeb]

So like 19 deg from flat?

[gtill]

I'd say a simple southern facing all year. In June, we have Kona sun day, which is when the sun is directly overhead casting no shadow and flat or nearly so would be appropriate. Asthe winter approaches, it dips deeper into the southern horizon, probably best at 45 deg. or more.

Someone please correct me if i'm very wrong. I am asuming the place is in a good sunshine area!

[mella l]

Seeb yes 19 degrees from flat. However a friend in the business told me that flat would be alright also, but 19 degrees from flat facing SW would be the ultimate.

mella l

[Carey]

The Bishop Musuem site has the dates and times of the two Lahaina noons (May & July)that occur each summer in Hawaii.

Lahaina noon is when the sun is directly overhead, and occurs twice in the summer as the angle of the sun passes to the north -it is actually greater than 90 degrees; about 94 degrees in Hilo- of each of our islands to summer soltice and then travels back to the equator for the fall equinox, where it is about 71 degrees and winter soltice it is about 45 degrees. This is why flat or 19 or 20 degrees are not so critical... but you do want your panel as close to 90 degrees for as much of the of the time... add the incline of you panel to the angle of of the sun ... twenty degree incline will give you a summer value of 116 and a winter value of 65... an adjustable panel frame allows you to maximize the angle even better for the seasons.)

added For Northern Hemishere, the panel facing south would be optimal...to a point (a panel mounted on a south facing wall would not be as optimal as a panel on a 5 degree angle to the east or west...here - doubt this is on anyones' plan, but just clarifying... ) The best angle is the one that gets you closest to 90 degrees the most time at your location & with the improvements that exist on your parcel (ie if you have a house with a 15 degree sloped roof facing SW, a panel would be OK, but not optimal, and better than on a wall that faces south...) The sun overhead (ie noonish) has less atmosphere to reflect the rays, hence the south exposure... that is when you get optimal noon time exposure, and if the panel is at the proper angle & achieves the optimal 90 degree angle, the panel is at optimal placement...

The link for Lahaina noon schedule for this last year (happened already)and lots of other neat sky stuff in Hawaii, is:
http://bishopmuseum.org/planetarium/planetarium.html

[gtill]

Thank you Carey, I had the gist, but that clears it up. And would a southerly direction be right, or other? I know we don't need tracking!

Gordon J Tilley

[JWFITZ]

I would say it's a little more complicated than that. The reason is our seasonal rainfall patterns, and the resultant short days. Depending on where you're located on the island, it may be very prudent to bias for morning or afternoon sun, as that may be the only sun you get. Trackers make a great deal of difference in output, and are very much worth the cost. You must realize that the 100 watt or whatever number they stamp on the panel is dependent on very arbitrary numbers, and is only a wild ass approximation.

Be sure especially you mount your panels in an area where you can get at them to keep them clean, and that the mount itself has good air circulation as they loose an awful lot of power output as they warm up. Mounting them on a roof is about the worst think you can do, as the heat of the roof will cost you 10 percent of your output or more.

I've installed a number of these systems and there are unadvertised tricks to squeeze out every last watt, it's worth a little research. People that sell panels are a poor source of information generally, and few understand the intricacies of the project as a whole.

[gtill]

Has anyone yet experienced the roll out self stick panel for PV roofing. Appearantly not affectd by heat, and capabe of pulling lighter sun loads, (indirect). Plus they're theft resistant. The original manufacturer was Uni Solar, from ENER. Google Em.

[hooligal]

I looked into the Unisolar laminates last year. Now I can't remember why I didn't choose them. I know that my major criteria were:
* weight of each unit ( can i install, adjust myself & remove/secure by myself for hurricanes or bad storms)
* production tolerance
* performance in HEAT and salt air/corrosive conditions
* limited roof area to mount panels

I *think* I avoided the Unisolar laminates because I have limited roof area. For the 136W laminate , I'd need 16" by 18 feet (3348 sq inches of roof area). My roof was only 9' long so I stuck with 130W conventional panels that only take up 1456 sq inches (56"x26").

I'm keeping my eye on NanoSolar in CA. They're doing amazing stuff. Can't wait for their products to hit the market for us residential joes.

Home Power Magazine that did a yearly review/comparison chart of all major panels in Oct/Nov 2007, issue 121. It also explained what all that confusing stuff means when you're reading panel specs. I never would have made a correct decision on my system or panels without that article (plus awesome advice from PunaWebbers). I got an online PDF version for not much money from the Home Power Web Site.