Solar Panels - Any Recommendations?

[Stu Jackson]

Pat, I think you're going wrong with

two house banks and switching daily. That's "old technology."Make the biggest house bank you can and add a small start battery.The larger your house bank the longer your batteries will last.

 

[John Nantz]

Line Shadow Test

This afternoon, ~6pm, I performed a quick-and-dirty "line shadow test". The panel was a Kyocera KC130 and I used the digital readout on a Blue Sky SB2000E controller for the measurements. The test "line" was a boathook, about 1" O.D.The panel output before the shadow was 5.8 amps (the panel was not optomized for solar angle). The boathook was placed across the middle of the width of the panel. When the boathook was actually resting on the panel the output droped to 5.2 amps - not quite anywhere near the "0" amps I thought might happen. As the boathook was raised off the panel the amperage gradually increased until at about two feet the amperage was unchanged from having no shadow.Based on this crude test I'd say if the panel was mounted somewhere near the stern of the boat that one shouldn't worry too much about line shadows caused by shrouds or the mast.Hope this helps folks with "line shadow" concerns. Disclaimer: results on other panels may vary, perhaps considerably. But hopefully panels with the similar type crystaline makeup would be in the ballpark.

 

[RAD]

Line Shadow Test

John, thanks for that test, I've been thinking about where I would put a solar panel on my center cockpit ODay and the only place I could do without custom and exspensive hardware was to put it on top of my dodger and if the mast or boom shadowed it at least you would get some voltage rather than none.

 

[Reudi Ross]

controllers

As John points out, MPPT controllers such as the blue sky maximize panel output. You will see about 20-25% increase in direct sun over a non MPPT controller. When your batteries are low, the % of power boost is greater. If your panel array is under 100-150 watts, it may be cheaper to add more panels than to purchase a MPPT controller, but what you do gain is more power out of the same panel footprint. You don't have to find more area to mount panels for the increase. Another factor that affects panel output, especially when using An MPPT controller is the temperature of the panel. The hotter the panel, the lower the optimum output voltage becomes. This partially negates the advantage of this type of controller. Always try to mount your panels with an airspace behind them for air circulation.The larger the array, the more cost effective it becomes to go with a MPPT controller. I run on at my all solar home with 1600 watts of panels. a $450 controller increases my power output 20-25% in the summer and 30-35% in the winter. At approximately $4.50 a watt for panels, that was money well spent.

 

[Sean]

Thanks for the test John Nantz!!

Thanks for going the extra mile with the test, that's a lot of good information!I really appreciate everyone's feedback, this is such a great forum! Thanks for the examples and pictures, this info has really given me a good leg to stand on. Now I can't wait to get my panels and controller, and go out for a nice extended trip!Thanks again!-Sean

 

[John Nantz]

Unanticipated Downside to Panels

Thanks for the comments. Everything is a compromise - selecting a panel setup is not unsimilar to the situation in selecting a boat.Forgot to mention, one unanticipated downside to panels was a comment from the Admiral that she doesn't have hot water now. As they say, "you win some, and you lose some!".Selecting a panel and a mounting setup involves many tradeoffs as Reudi point out. For the northwest one has to optimize for clouds, fog, and overcast as this is what you get for much of the cruising season. The cooler temperatures also help. For the sunny areas of the country one might optimize with a different type of panel.Wattage: I just wanted something to supplement alternator charging, not to eliminate it. I figured for some occasional bulk charging at 70+ amps the batteries could be bulked up easily. However, I didn't realize the "8 amp panel" could actually put out 11 amps, and maybe more, when paired with the Solar Boost controller. This was a very pleasant surprise. The nearly 11 amps was at below optimal conditions.Although I bought two panels it appears that in sunny weather that one is more than adequate - if it's not in total shade. A second panel on the opposite side of the boat will be needed for redundancy. Cost analysis: It's VERY hard to quantify costs for some items on a boat. In my case the money spent was based on a very subjective cost analysis - I already knew what I wanted and I got it! What more can I say? Refrigeration is a "must have" - that's a given, and it takes power to run it. Ditto the forced air heater. To justify the solar decision I'm assuming a savings in less wear-and-tear on the engine using it as a generator to charge the battery bank. Next, in the area we like to cruise, fuel availability is really sparse so not having to alter ones itinerary to obtain fuel is worth something but very hard to price out. The panel mounting system is really "cheap" - probably going to be around $20 per side. Maybe not the most elegant but it is functional and can be removed without leaving any "personalization" of the boat whenever we go to sell her. With the intended use, the very long life of panels (Kyocera have a 25 year guarantee on rated power), and the guaranteed increase in oil-based energy costs, the decision to go solar, even if the system is somewhat less than optimum, seems to be a no-brainer.Hot Water: On a sunny day I MIGHT be able to run the hot water heater a bit via the inverter utilizing the surplus power - even warm would be good. If this works (it would be an interesting experiment) then the Admiral will be happy; if not, the captain (note the little "c") has more work to do. And I'm open to ideas. We have a plastic bag water heater but that's a last resort method.

 

[Bill Roosa]

Dump the wind gen power to the hot water

This is IMHO why you see cruisers with solar and wind gen set ups. A wind generator can be set up to dump its excess power into a water heater. Yes it is a manual job to cut the water heater up and install a heater element but it can be done. Now if you are in a snug anchorage where the wind is not blowing......you have an issue. But under sail you can have all the hot water you want. Most hot water tanks will stay hot till the morning so you might be able to run a schedule to solve your problem.

 

[RAD]

Bill....

Why would you have to cut up a water heater to install an element?*o they come with them installed already

 

[Bill Roosa]

12 Volt vs 120 volt

Sorry, I should have said "modify your hot water heater"While you could put the 12 volt output through the 120 volt heating element, you will not get much heat out of it.Power dissipated = volts X ampsSince the 120 volt heating element has a much higher resistance it is not going to pass as many amps at 12 volts and therefore you will need a 12 volt heating element. You could get lucky and have a water heater with an extra port in the side. If you only have one port you have to either add another hot water tank and wire it for 12 volts or drill a hole in the existing tank.

 

[Bill Roosa]

OR do this

Google is cool!!They now have a 120/12 volt combo heater that just screws in!

 

[newly anonymous]

wow!

a load diverter that heats water! Thanks, Bill, I think you just converted me to wind power.

 

[rsn48]

Check the wind

Before you get too excited, check the wind in your sailing area. Here in sometimes sunny coastal British Columbia, the winds aren't that constant or heavy on the Straits of Georgia in the summer. In fact, they are famous for stopping at around 4:00 PM (some say for cocktail hour) and then not returning until around 8:00 PM.The word I was given about our weather here is that if you want "free power" you need both solar panels and wind generators. This becomes pricey and on a smaller boat like the Catalina 27, some what difficult unless you have some kind of arch due to space limitations. A smaller quiet generator makes more sense.

 

[Bill Roosa]

Dito rsn48

I ain't the smartest person but every time that I see pictures of a certified blue water cruiser they have huge alternators, solar panels, and a wind generator. Seems redundancy is the key to success.

 

[Ross]

Bill either that or they have an uncommon

need for electricity. A solar panel will meet the needs for keeping a starter battery charged. But how much are we taking with us when we decide to get away from it all.

 

[Bill Roosa]

Well since you asked

Reefer(60AH), radar(28AH), VHF(26AH), SSB(28AH) and the wife's power tools account for over 142 AH per day while at sea. I have around 6 hours to collect (static mount) that with solar so that means (roughly) 142 AH / 6 H = 24 amps. Or 24 A * 14.4 V = 341 watts of solar panel. That is 3 of the biggest but it can be done.Now I could run the radar, VHF and SSB less often but I'm a nervous navigator. I have not found a way to run the reefer or the power tools less.Now if you factor in the "toys" like running lights and pressure water pumps....... Do they have a paint that I can coat the topsides with that makes electricity out of sunlight?I'll be the first to admit this is not a bare bones operation but I really think this is not a toysRus kind of deal either.With all that said, solar, wind and gensets are all great. They give me tools for safety and convenience and toys to play with while cruising. One thing I notice is that solar and gensets charge the batteries in short bursts while the wind generator does the more or less constant trickle charge. When you factor in the constant output of a wind generator you can get some substantial reduction in battery bank size and your batteries tend to stay "topped off" and not cycle deeply. But they don't work when becalmed. I find I need all three to cover all the bases.

 

[Terry]

Solar Panels

Sean, As Bill states, it depends entirely upon your boats usage. I just spent a month sailing with no shore power and very little motoring and my solar panels were able to supply more than enough power.  I have two EC102's which are 100 watt panels. Most days were sunny which is definitely a plus. Equiptment used was refrig,gps,autopilot,wind meter and bidata all used 24hrs/day. The solar panels usually have a blocking diode included in panel to prevent battery from discharging. I wired the two panel in parallel and routed them thru a charge controller, this is needed to prevent overcharging the batteries. And from the charge controller thru a battery isolator to my two battteries. I have used the link below to keep track of prices.Sail On...Terry