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Solar Panels – Flexible Panels vs. Hard Bimini & Rigid Panels

12 Comments

So now that I have put the non-solar powering item to bed (at least for me), I plan to go with running the diesel instead of a small gas generator, it’s time to turn my attention to solar.

Since I had seen this post by the always helpful and inspirational MaineSail, I had planned on going with the flexible Solbian solar panels on my bimini.    At the Newport Boat Show I spent a significant amount of time talking to the people at the Solbian booth.  It was at this point that I began to think my plan for the Solbian panels might not work as I expected.

Sure enough, when I measure and planned out where the panels would be I couldn’t fit what I wanted.  I had hoped to fit two of the CP125 panels on my bimini with room to add some smaller panels down the line.  But I can’t fit those panels without crossing a bow for the bimini support which is a big no, no.  The panels can flex on the bow and break.  This means I would either have to go with the more expensive SP series panels or go for smaller sized panels than I wanted.

Since we are going to cruise in a smaller boat I know we can’t fit enough panels to be entirely self sufficient.   However, I would like to reduce the amount of time we have to run the engine to two hours or less per day.  With that in mind, I worked up the attached power consumptions to help me figure out what my max loads will be and how much solar I should try to add.  I included a watermaker in this analysis and I have played with the refrigerator amount as well because we plan to have a watermaker and a 12 volt freezer (leaning towards the Engel).  I am also in the process of verifying our current 12 volt use based on readings from my battery monitor.  I got the form I used from someone on Cruisersforum.com, I wish I could remember where so I could credit the person who created it.  A copy is attached.

Power Consumption worksheet 2

I divided my usage up into 3 areas, under sail which is the worst case conditions, on the hook and on the hook with no one on the boat (for when we go traveling on land for a couple of days).  I have estimated we will use between 55 and 165 amp hours per day while on the hook and as much as 200 amp hours per day under sail.  With my current alternator, 60 amps, assuming a 75% efficiency (I am not entirely sure what efficiency to use) I can get back 90 amps from running the diesel for 2 hours.  This would leave me with around 75 amps per day I would have to get back from solar (or more so I could run the engine less).

Solbian Panel Option

Under this option the first thing I would need to do is bring my current bimini to a canvas show to have some repairs made (rips and thin spots that have developed in the last 12 years since it was new).  I have estimated this at about $700 based on talks with the canvas shop that made repairs to my dodger last year. Then I would need to make the bimini frame more rigid.  It is currently 1″ thick wall stainless held in place with straps.  I would ditch the straps and then make the structure more ridged with some additional 1″ tubing.  The Solbian panels could then be mounted to the bimini with Velcro a la MaineSail’s method.  Here is what that layout could be.

Solbian Panel Option

If I went with the smaller SL90L panels that would put the cost around $3,700 for 37.4 amps per day.  With the SP125 panels it would be closer to $5,000.  Not a very cheap option.

Hard Bimini & Rigid Panels Option

Another approach would be to rebuild my current bimini with a hard, rigid cover instead of the canvas.  I research this and found a number of people who have done with the King Starboard, purpose made panels from Hard To Top, Azek exterior plastic for houses and expensive, custom made fiberglass hard tops.  The custom fiberglass is out due to cost.  Same with the Hard to Top.  Starboard would cost about $500 for enough material.  But the Azek would only be about $125 and I could make the hard top from one sheet.  Also at only a 1/4″ thick and made from plastic, it wouldn’t weigh too much yet with proper backing plates it would be able to support solar panels and a few other things.  You can work the Azek trim sheets just like wood and I do have access to a really talented carpenter that could likely help me make this look professional.  I could fit 3 large solar panels on this hard bimini (either 3 95 watt panels or 2 160 watt panels and a 95 watt panel).  The cost to constructed the hard bimini would actually be less than getting my canvas one repaired.  Here is what that layout would look like.

Hard Bimini Option

If I went with the larger 160 watt panels and a 90 watt panel I would get about 80 amps per day.  This would cost about $2,500.

NOTE: This is based on the Go Power! solar panels sold by Defender.  I need to do a lot more research to figure out if these are good panels or not.  I suspect I am not making a true apples to apple comparison and may need to update this when I have research solar panels more.  Please feel free to add any comments on these panels or recommend some good ones.

I am attaching a parts list for each approach.  Let me know if you think I have missed anything.

Solar Cost Evaluation

Based on this first bit of research it’s looking like the better way to go is the hard bimini.  I would love to here from others on which approach they think is better.

Cross posted on the C310 Owners Forum.

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12 thoughts on “Solar Panels – Flexible Panels vs. Hard Bimini & Rigid Panels

  1. Great post! We just bought a canvas bimini from a local seamstress .. wish I’d seen this post first! Looking forward to reading other comments, as well as your decision. We’ll definitely need solar panels, and while my husband prefers panels on our future davits I often wonder about on top of bimini. Would make it easier to get on and off the boat.

  2. We have a hard dodger and Bimini Phil made out of plywood and painted with expoxy 2 peat pant and mounted 2 Koycera 140 watt for about $300 each on top. We have refrigeration and LED lights and have excess electricity when the suns out all day. So far has been working well. We use to run the engine daily before solar panels. Now don’t have to do the unless cloudy. If you’re hand, can be done much cheaper.

    Lorraine
    S/V Changes
    C&C 34
    Changesgoingsouth.com

  3. Great post and lots of good info! First of all I’ld like to say that you will just love a solar instillation appose to running the engine. I’m still kicking myself for delaying and loving mine.
    Any shading kills them unfortunately and forgetaboutit on cloudy days. That’s when a wind gen would be nice. Also a tilting mechanism would be nice.
    I don’t want to be rude or anything, but I find your power consumption is pretty high (not that I have any recommendations). But get a controller of high amperage so you can upgrade (or add more) panels if needed. Also make the hard bimini rock solid (for real high winds). Then sit back and enjoy! Go for it!

  4. what you can also use to mount the panels to the stainless frame are the plastic rail mount clamps from west marine, about $10 a pair. You can use 2 pairs per panel, and easily get more wattage up there than the flexible panels, and keep the canvas bimini. Also, check out Arizona solar (or something like that) for panels and charge controllers, a MPPT controller will get you a little more amperage and let you buy a 24v panel to tie into a 12v system. There are a few photos of our install with the clamps on our solar setup over on our blog. And I still think the small honda genny is a better idea than running the diesel 😉

  5. Nice writeup.

    200 amps a day, that is a bunch. Usually under sail I have only my VHF handheld on and turn on the chart plotter as needed. I was looking at adding a fridge and was hoping 150watts would cover it, looking at your chart I may need to rethink.

    Also keep in mind that when anchoring you will probably run the motor for about 30 minutes, same with pulling the anchor in the morning. That gives you an hour of charging.

    The problem with bimini mounts is that I enjoy folding mine down every so often.

  6. OK, so we have made a decision about solar….

    We decided to not do anything this year. We were going to move to a slip with no power starting next year but we figured it would be better to put that off for a year. Clearly my thoughts are not complete on this subject. I still have a lot of planning and research to do before I am ready to commit several thousands of dollars to this project.

    Also, I am hoping that the cost of the Solbians will drop, at least a little, in the next year. My preferred approach would still be the Solbians on our bimini. MaineSail has pointed out some really big problems with going with the hard panels onto of a bimini like mine. Searaven gave me some other installation methods to think about. And Zoots and others have pointed out that I might be over planning the size I need.

    So this project will be delayed for another year or so while I plan and research better. Right now I am thinking I might be able to get what I need for solar with a combination of the Solbian panels on the bimini and some solar wings.

    Thanks for the feed back all.

    Fair winds,

    Jesse

  7. Its advisable to take the help of a good solar panel specialist/seller to get the best panels for your bimini.

  8. I must say I have never thought of putting solar panels on a boat before. I like the idea and am very curious now on how well it works. Last year we had Sungate Energy Solutions install panels on my home so I think I will give them a call to get an estimate for my boat as well.

  9. Great post and really good research, Jesse! I don’t need solar power on our current boat, but definitely will on our cruising boat when that time comes in the near future. Thanks.

    Mike
    http://www.siochana.us

  10. Pingback: Trying to Makesense of Solar Options « s/v Smitty

  11. Pingback: Solar Install |

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