The first project is one I started in December. I would really like to replace the fabric bimini top on the boat with a hard top. There are a number of advantages to having a hard top. First, I won't need to deal with replacing the fabric on a semi-regular basis as the sun takes its toll on fabric and sewing of the top. More importantly, it provides a wide and stable platform for working with the main sail boom, something I consider to be a safety enhancement. It will also be a nice platform for mounting solar panels. And there is no point in creating a new set of dodgers for my current top if I intend to replace it. So, I've been talking with a guy in town about options for creating a simple hard top and looking at other designs for ideas on getting one made for a reasonable cost.
Speaking of solar, that is also on the list of upgrades I would like to make soon. Currently, the only ways I have to keep the batteries charged on the boat are to run the engines, run the diesel generator, or plug it into shore power. Since I would like to spend more time out of marinas and on anchor (and not have to burn lots of diesel), I need a greener way to keep the batteries topped off and solar power seems like the best option. Having a catamaran, and particularly one with a hard top bimini, provides a lot of space to install solar. Recently Kyocera came out with some solar panels that produce up to 325 watts of power at 40 volts DC and they are reasonably priced. With the right maximum power point tracking (MPPT) controller, two of these panels could produce somewhere in the neighborhood of 240 Amp Hours of juice a day. So, I've been looking at solar packages similar to this one to add to the boat. I also performed a power inventory to see how much power I think I will need in a day. Of course, a lot of this is still guess work as I don't have really good numbers for how we will be using power. Things like the refrigerator (one of the big power hogs) is easy, but other lifestyle uses are still somewhat unknown.
I also need rebed both of the large salon side windows on the boat. It seems that Leopard didn't have a good process or didn't use the best materials when they were originally installed. The result is a failure rate on the seals on the windows on most of their older boats is near 100%. The windows have no mechanical fasteners and are only held in by sealant. So, I've spent a lot of time looking through all the questions and pictures on the Leopard owners group on Yahoo. It sounds like a bit of a tedious and messy process, but I think I have a handle on it. Guess I'll find out soon as the sealant needed should arrive later today. Then I just need a couple warm dry days to do the work.
One other task has popped up that I wasn't planning on. When I was showing a fellow Leopard 3800 owner at the marina my new Mantus anchor, we noticed that the fiberglass structure that the anchor roller is mounted to has started to crack. The roller and bail now move some when they shouldn't move at all. Since this area takes a lot of load while anchoring, it will need to be repaired. So, with my very limited knowledge about fiberglass repair, I've been researching that as well. Looking at the other Leopard, his boat has a significantly thicker fiberglass structure than mine, so I guess someone might have figured out an issue with the boat in between when mine was built and when his was. In any case, looks like I'll be doing some pretty serious fiberglass layup work in the near future.
So, filling my head with boat fixing knowledge, hopefully I can execute some of it well.
Hey Mike,
ReplyDeleteThat kit looks really good but I think you might be overestimating the amount of power you will get from them. I used this site to help with my research: http://www.pbase.com/mainecruising/solar_panel
Here is how I would calculate the expected yield.
The panels are rated at 7.99 amps each. You will have a charge inefficiency of about 15% (energy loss going through the process and what the batteries can accept. Might be a little less with a MPPT controller). From your thoughts on the bimini it appears you will flat mount these there. That means you will only get about 5 hours of peak sun giving you the full output. So that's closer to 68 amp hours with some less efficient additional power coming in the rest of the day. So maybe you will get 100 amp hours per day from these but shading will have a lot to do with it.
On the hard bimini, check out http://www.azek.com/products/trim/sheet. You can get it in large sheets. I was thinking of going this route before and this stuff was way cheaper than king starboard and seemed like it could do the job. I got onto it from this thread on the cruising forum: http://www.cruisersforum.com/forums/f55/fiberglass-panels-for-hard-top-bimini-92900.html
Good luck and fair winds,
Jesse
Hey Jesse,
DeleteThe panels are rated at 8.07 A @ 40.3VDC (to get 325 watts - the link to that kit showed the older 320w panels). Using the MPPT controller, the theory is that it will step down the voltage and increase the amps. 325 watts becomes 24 A at 13.6 VDC (charging voltage for a 12V battery). 2 panels @ 24A for 5 hours a day is 240 AH. Now, that is a no loss calculation and I'm sure there is some minor loss in the conversion, but I'm also guessing some partial power outside the 5 hours to make up the difference due to conversion losses. But, unless I'm totally off on my understanding, I'd say it's "in the neighborhood" anyway. ;-)
Of course, this doesn't take shading into account and that could vary the numbers a lot since 15% shading I'm told will pretty much kill a panel. Trying to figure out the best configuration on that. Some say mount the panels on the starboard side since prevailing winds at anchor will help keep them out of the shade...but who knows...and that theory doesn't work well while sailing unless you are heading due east...which won't likely happen without motors. Lots of theories out there.
Still waiting for a reply from the guy regarding the bimini. I was looking at the options for Starboard as well as cored fiberglass. Honestly, if I had a big workshop I could use, I'd do a cored fiberglass layup with integrated support so I wouldn't need a full metal frame. Still going around in my mind on materials and design on that one. And maybe renting a storage building to do the layup myself if I'm a big glutton for punishment.
We are going deep down the rabbit hole today.
DeleteWhat you said about converting excess volts into amps is mostly true from my understanding but you have some other things you need to account for.
The MPPT conversion, DC to AC and back to DC. You will have a 3-7% loss in the conversion.
In the area where we both plan to cruise the ambient temps will be high so that 325 watts will probably be under 300 watts (solar panels are less efficient in the heat).
Now you have to think about battery state. The advantage you are talking about is only when in bulk charging. Once you get over 80% SOC and start absorption charging you lose that efficiency. There is little difference between an MPPT controller and PWM controller once you are in the absorption and float stage.
Then you have the acceptance efficiency on the batteries to think about. Batteries can more readily accept charge up to 80% but that last 20% can be very difficult. Your volts go from 13.6 up to 14.1 and it's harder to push them in.
So let's say you have a 400 Ah bank, that's 200 Ah usable before you get to 50%. But most likely you won't be drawing your batteries that far down each day. If you are you sized your bank wrong. So let's assume you used 100 Ah. That would put you at 75% SOC. You only will get the additional MPPT value for the first 5% of recharge. After that you don't get the benefit. So the first 20 Ah of charging will get the MPPT benefit. By the time you hit peak sun you might be out of bulk and not get the MPPT benefit.
Obviously there will be a lot more that will go into this like what load you are putting on the batteries, etc. And that is why I am still a fan of the MPPT charge controllers. My hope is that if we eventually add a 12 volt water maker, if we run it during peak sun we won't see as much of a power loss. Also, we using our autopilot under sail we may be able to break even. But now we are getting into some hard stuff to predict and I am just going to install it and see how it goes. Monitor and make adjustments. Also, if you have a couple of shady days you might be down to 50% SOC and get better performance from the MPPT. Also, the MPPT reportedly handles shade better.
There are some cruiser that live with their batters in the 50-80% SOC but that is not good for the overall life of the batteries.
Sorry for the long comments. Just some thoughts.
Jesse
I haven't taken a deep look at the MPPT technology, but I hope that current chargers aren't converting DC -> AC -> DC...that would be terribly inefficient. probably more on the order of 10~15% loss. Will definitely need to see how these companies have implemented MPPT.
DeleteAs for Bulk/Absorption/Float...I've dealt with that before. The usual mechanism is to provide constant current for the bulk charging phase, adjusting voltage to keep the current constant. Switching to a constant voltage charge (varying current) at the switch over point to prevent overcharging the batteries (constant current can actually be used to full charge, but one must be very careful not to cook the batteries so most automatic chargers don't do this). This is the main reason that the last X% takes so much longer. Given I've seen temperature probes listed in the mix of connections, I do hope that the chargers take advantage of bulk charging a bit further if they are bothering to monitor battery temperatures, but will need to review the specs on the various chargers.
The "amount of power I would use in a day" is still a pretty big question mark as far as daily habits go. The always running stuff like refrigeration I can figure out easily...but the more random loads are a bit of a question mark...probably won't know until my wife joins me aboard and we actually get going. Could be as little as 100AH or as much as 300AH (under sail with the radar and auto-pilot going, etc.). I still need to dig everything out of the locker to take a look at the batteries, but I think the house bank is somewhere in the neighborhood of 500AH.
So, as you say, probably just going to "see how it goes" once I get to that point. ;-)
Mike,
ReplyDeleteI just took another look at that kit, the wires that come with it are NOT tinned copper. So I wouldn't use that on your boat. You will probably have to source the parts separately. Tinned copper 4 gauge wire will run you around $2.50 a foot while standard copper is under $1 just to give you an idea on cost. I get mine from Defender.com. You don't want to go cheap on wire or lugs. I tried and it's not worth it.
You could also save money by going with ANL fuses instead of the breakers. In a marine setup you only need to fuse where you attach to the batteries. On land, code requires a fuse or breaker between the panel and the controller. Most knowledgeable electrical guys don't think this is necessary.
Jesse
Hey again Jesse,
DeleteYep, I know that several components in the linked kit are not marine grade, and when I get closer I'll see if they can supply marine grade equivalents or source things elsewhere.
BTW, you may want to check out this place for tinned wire (and connectors, etc.). They are actually local to me now and I've bought some other wire from them. The tinned copper 4 ga is $1.92/ft with discounts for larger quantities. US made cable. GenuineDealz Marine Wire
Still working out all the details. Panels will come after the bimini so I'm just in the research phase now. Thanks for the tips/advice and good luck on your solar project.