All good questions. My powernusage is primarily for refrigeration as I have all led lights below. Other power usage is occasional TV via small inverted, stereo and fans. While under sail, have most of the common instruments like autopilot, gps, depth, wind etc running. Have estimated power consumption in the 50-80 amp range with a 320 amp house bank wired in parallel and a small starter battery. Reason my amp range is so wide is that I am getting a new fridge within a month so I expect energy demand from the fridge to improve significantly. Today I estimate 60 amps per day which is why I am replacing it. Long term 50-60 total is probably where I will be. The 160 watt Bosch panel has peak amperage output of 9 amps and since it can be rotated toward the sun i am told this is a realistic number.
The single pole mount used is actually braced at both the bottom and top stern rail and attached to the top of the coming on a swivel ball mount. My windage concern came from my brother-in-law who races his J120 so the concern may not apply to a cruiser like me since I do not race. Still, wanted to ask for opinions on anyway because my concern is both slowing me down and the stress on the stern rail and panel when it is windy. Regarding the bimini mounting options, I am well aware but the issue is we rarely have our bimini deployed. Only when it's raining because otherwise we prefer to be in the sun. So I do not want a bimini mount nor do i want a frame over the bimini. Just prefer sailing without the bimini.
Last question is in regards to the mppt controller. I am told that two battery banks will require two mppt controllers and that the PWM controllers will connect to two banks and allow you to portion how much charge to each bank. Also, this panel is 20 volts so the guy says the improvement with mppt is not that great. Does this sound correct? Thanks....bob
with refrigeration, 160watts wont be enough for a long term, trouble free system.
if you are designing the system around getting the max rated amperage out of the panel, you will be sorely disappointed, because it is
un-realistic...
quoted here from
wholesale solar website....
"The current and power output of photovoltaic solar panels are approximately proportional to the sun’s intensity. At a given intensity, a solar panel's output current and operating voltage are determined by the characteristics of the load. If that load is a battery, the battery's internal resistance will dictate the module's operating voltage.
A solar panel, which is rated at 17 volts will put out less than its rated power when used in a battery system. That’s because the working voltage will be between 12 and 15 volts. Because wattage (or power) is the product of volts multiplied by the amps, the module output will be reduced. For example, a 50-watt solar panel working at 13.0 volts will products 39.0 watts (13.0 volts x 3.0 amps = 39.0 watts). This is important to remember when sizing a PV system."
so there are too many variables... even if you have a lot of sun.
and the hotter a panel gets, the less efficient it is.... a panel in freezing temps with bright sun on it will have a higher output than the same panel set up in the tropics. although the one in the tropics will have sun for a longer period, the point is, the rating of the panel is not at 120 degrees surface temperature, which means it wont produce to its potential. and as the panel ages, the output will drop.
when the max output rating of the panel is created, its in a very cool atmosphere.
there will be too many hours that the panel wont be facing the sun directly, too many days where the power consumption goes on and on, but the panel can only put out a given amount, that is usually a decreasing amount, rather than an increasing amount. (bright sun, cool early morning with the panel facing directly toward the sun is the highest output of the day)
to think you will be a husband to the panel every hour of every day, and keep it rotated and tilted into the sun is expecting too much of yourself, because it wont happen.
more wattage would do you much better for your needs, and its reasonably inexpensive to add more watts by switching your plans to 2 smaller panels before you start buying and assembling. a small investment now in more power, will pay off big later.
if you install (2) 120w panels now and the right sized MPPT controller, and you install the system so its quick and easy to upgrade to 140's or 160's in a few years... you are taking care of your needs now and saving a LOT of money in the end, when you decide the time is right to expand.
always remember, a correctly sized and installed solar power grid/array can add actual value to the boat, but it can also be taken with you if you decide to upgrade the boats so its never a totally lost or bad investment.
you dont need 2 mppt controllers... all you need, and should have regardless if you have soler charging or not, is an ACR for your battery banks...
bracing the pole to the stern rail may not be a great idea... if there is ANY movement in the railing if you grab it and lean into and away from it, it may not be strong enough. even one panel is a lot of weight that high on a single pole, and there will be vibration due to wind and waves, and so over time you may begin to see stress cracks the the railing joints. just be aware...
and do you think a panel that is 48-50 inches long and 20-24 inches wide, mounted to a pole over the cockpit is going to be less ugly than a bimini frame, with out without the bimini canvas on it?
a well braced bimini frame will allow for two panels to lay side by side at a very low profile on top of it, and still be pleasing to the eye..
and yes, we all like the sun, but whether you have a solar panel overhead, or a piece of canvas, its still going to cause shade. and if the sun gets too intense, as it does at times here in the beautiful northwest, a bit of shade to get under is a good thing. in my experienced, but humble opinion
also, in addition to eye pleasing results, its always been my quest to design for "dual purpose" whenever possible.... this prevents having unnecessary protuberances hanging from, or sticking up or out from the boat everytime I want to add something else to it...
