Solar Panels Installed on Daydream!

[Pat Anderson]

Renogy Solar, 2 x 100 watt solar panels and a 30A controller with free shipping for $379. A couple of T adapters and 4 6' MC4 cables added maybe $30 more. The sun is shining, and she must be generating right now! I can see I am going to want some kind of monitor, recommendations welcome, but not likely to spend as much on a monitor as I did on the whole shebang! Can't wait to get to Powell next year, going to stay as LONG as we want to in 2014, now I don't think we are going to have to worry much about running the fridge even if we stay put for days on end!

 

[rogerbum]

Nice work. It looks like it may be a little challenging to go forward now that the hand rails are covered. Do you have some plan for that or do you scoot out the hatch in the berth?

 

[Sunbeam]

I have a Victron BMV 600s battery monitor. I really like being able to see what is going on with a monitor. I haven't used the Victron too much yet, but I have had similar monitors in the past on other boats (Link) so that's how I know I like the function. What won me over to trying the Victron this time was the ease of installation due to the Cat 5 type cable as compared to others (also it has a good reputation in general). Cost is around $150.

 

[thataway]

I have the Link currently--and have used similar systems for a long time. Currently I would buy the Victron BMV 600 or 602 (which allows voltage measurement of second battery). The Link or Victron will measure voltage of primary battery, amount of amps used and amount of amps in and out of the house battery. The Victron is slightly easier to install, since it uses a telephone line type of cable. You have to put a shunt in the ground system for that battery which you are using.

Pat, Is the location of your solar panels where you are going to put them permanently or are you going to make a mount?

 

[journey on]

Pat,

I've got solar panels for the house and I've done some analysis for them. So bear with me and I've got a question for you.

How many watt hrs/day do you get out of those solar panels? Which I assume is 200 watts mounted horizontally (approximately.) I also assume that your battery meter will give you the watt-hrs pumped into the battery.

First and forgive me for this, solar panels operate on a cosine curve. That is, when the sun line is perpendicular to the panel, the incident angle is 0 deg, and the cosine is 1. The panels are putting out the maximum power. Typically, that's at their rated times some derating factor. For terrestrial panels, that's 15 to 20 % ( Calif's Solar Energy factor.) So as the sun diurnal motion is from the East to the West, the incident angle goes from -90 to + 90 and the power output is a positive cosine curve. The energy is, of course power X time and is the integral of the power cosine from 6 am to 6 pm., since the earth turns 15 deg/hr. That's true if the sun is directly overhead. So allowances should be made for the suns declination and the solar panel mounting angle. If they're flat, that's a factor of the cosine of the latitude, which at Seattle is ~0.7 (~45 deg.) And of course the declination varies with the season.

So, my panels are mounted at an angle of 32 deg, the latitude of San Diego, and as is true for the whole earth, the declination is + 24 deg. At the spring and autumn equinox, I get ~ 7 watt hrs for each watt of solar panel. That takes the Kw-hrs I get per day, and fits the cosine curve at my rated power level. Everything fits withing some degree of approximation.

And if anybody will check my assumptions I would be eternally grateful.

So, 7 watt-hrs X 200 watts X cos (latitude) = 1 Kw-hr/day@ autumnal equinox, which we're approaching. That's my best case estimate. Pat, what are you getting? I'd dearly love to check my assumptions.

Boris

 

[jkidd]

Renogy Solar, 2 x 100 watt solar panels and a 30A controller with free shipping for $379. A couple of T adapters and 4 6' MC4 cables added maybe $30 more. The sun is shining, and she must be generating right now! I can see I am going to want some kind of monitor, recommendations welcome, but not likely to spend as much on a monitor as I did on the whole shebang! Can't wait to get to Powell next year, going to stay as LONG as we want to in 2014, now I don't think we are going to have to worry much about running the fridge even if we stay put for days on end!

Nice work Pat.

I also have a Victron BMV 600s battery monitor. Pretty easy to install It will tell you current being used or current being put back into the batteries. So once you get anchored you can move the panels to get the most gain. I can't wait till I don't have to worry about getting back to work and I can stay at Powell as long as I like.

 

[localboy]

It looks like it may be a little challenging to go forward now that the hand rails are covered.

I was thinking the same. Watch your step.

 

[Pat Anderson]

Roger, no problem going forward - I still grab the handrail, the panel is attached to it but does not cover it!

Nice work. It looks like it may be a little challenging to go forward now that the hand rails are covered. Do you have some plan for that or do you scoot out the hatch in the berth?

 

[Pat Anderson]

Boris - I am still sort of like, sun shines, panels make electricity, it is magic! I don't have a monitor, and I don't have a bent for physics or math! So I have no idea! What I do see is that the voltage stays up even when the motor is not running, I go into darkness with fully charged batteries, and they start recharging just as soon as it gets light!

Pat,

I've got solar panels for the house and I've done some analysis for them. So bear with me and I've got a question for you.

How many watt hrs/day do you get out of those solar panels? Which I assume is 200 watts mounted horizontally (approximately.) I also assume that your battery meter will give you the watt-hrs pumped into the battery.

First and forgive me for this, solar panels operate on a cosine curve. That is, when the sun line is perpendicular to the panel, the incident angle is 0 deg, and the cosine is 1. The panels are putting out the maximum power. Typically, that's at their rated times some derating factor. For terrestrial panels, that's 15 to 20 % ( Calif's Solar Energy factor.) So as the sun diurnal motion is from the East to the West, the incident angle goes from -90 to + 90 and the power output is a positive cosine curve. The energy is, of course power X time and is the integral of the power cosine from 6 am to 6 pm., since the earth turns 15 deg/hr. That's true if the sun is directly overhead. So allowances should be made for the suns declination and the solar panel mounting angle. If they're flat, that's a factor of the cosine of the latitude, which at Seattle is ~0.7 (~45 deg.) And of course the declination varies with the season.

So, my panels are mounted at an angle of 32 deg, the latitude of San Diego, and as is true for the whole earth, the declination is + 24 deg. At the spring and autumn equinox, I get ~ 7 watt hrs for each watt of solar panel. That takes the Kw-hrs I get per day, and fits the cosine curve at my rated power level. Everything fits withing some degree of approximation.

And if anybody will check my assumptions I would be eternally grateful.

So, 7 watt-hrs X 200 watts X cos (latitude) = 1 Kw-hr/day@ autumnal equinox, which we're approaching. That's my best case estimate. Pat, what are you getting? I'd dearly love to check my assumptions.

Boris

 

[Pat Anderson]

The panels are probably going to remain where they are while on the boat. The dinghy has to go on the roof (which it does nicely), so the solar panels pretty much have to go where they are. So far so good, but I will no doubt get a Victron BVM 600 to kind of keep tabs on battery state beyond just voltage.

Pat, Is the location of your solar panels where you are going to put them permanently or are you going to make a mount?

 

[potter water]

Boris is pretty much right on. And using solar panels efficiently really requires a lot of math and geometry and electronics. I'm not going to analyze his math, but you probably need to get use to the idea that solar panels aren't magic and your 200 watts will get down to an actual delivery of maybe 50% of that or even significantly less on average, even in good sun. All of us will be interested in your first hand reports of how well the panels handle your needs and expectations, particularly regarding a way to avoid the 5 buck per bag ice penalty we pay for ice at Lake Powell.

Solar panel sales folks are notorious for unrealistic ratings of their panels. I know as I've been putting spacecraft into orbit and planetary explorations for about 35 years. When these things are critical to a 100 million dollar spacecraft, we derate as much as a factor of X10 from advertised to take care of a fairly steep degradation curve over time in the substrates due to the very solar energy that makes the juice, and to inefficiencies in transporting the power around the on board systems. Also, there is a fairly high infant mortality rate of failure of individual cells that make up the whole panel.

I don't say any of this to minimize the value of a well put together solar charging system, but solar gets a bad name from all of the above mentioned issues.

In regards to recreational use of solar panels, if you think you need 100 watts of power for a few hours, then your 200 watt system will probably reliably do that for a couple of hours one side or the other of noon. As you look at the power consumption of your fridge, I'd recommend keeping that 50% derating in mind.

Just an extra note. Just because the panel is putting out "nice" voltage, doesn't mean it will put out that voltage under typical loads. Measure the voltage at the battery with some reasonable load turned on with the panels putting out over the space of sunrise to sunset and you will get a real good idea of the major degradation that occurs in the voltage and current available for use on the boat.

I think your 200 watt panels will be excellent at keeping the batteries topped up with little to no load on the batteries. Well, I'm no brain surgeon, so don't be too critical of me...but wait, I am a rocket scientist!

Keep us posted.

 

[potter water]

Don't you just hate it when you get something cool on your boat and some scmucks who are jealous poo poo your cool thing. I hate that too.

 

[thataway]

Henry good piece. I had a chance to run our RV in the hot Florida climate dry camping when we were having a problem with a transfer switch so that the generator would not run the house loads or battery charger..
We found that our 100 watt panel still was keeping the battery at about 13 volts during the mid afternoon, with several fans and the 12 volt part of the refer running. I don't have a amp meter on that circuit so I don't know the actual output.

My solution to battery power on the boat is a EU1000i running two chargers--one 20 amp for the house batteries and the other 30 amps charging the battery dedicated to the Dometic Freezer. About 2 hours a day keeps the freezer battery topped off.

 

[Pat Anderson]

Harry,

No problem! My "mission" is not "critical"! These solar panels are 1000% better than NO solar panels! At anchor in Matia Cove right now, going into the night with fully charged batteries, fridge running, will post what I have tomorrow morning!

Pat
KD7OAC

 

[potter water]

You are right. Something going into the batteries is much better than nothing going into the batteries. At the very least, you will significantly extend your battery's juice time. Sounds like you have a healthy perspective. Also, the only thing that looks more cool on a C-Dory other than twin engines is twin solar panels.

 

[journey on]

Pat, forgive the work in my previous post. It was merely trying to cive some credence to my statement and question.

Nevertheless, in your first post you said that you were going to get a battery monitor. I think that's an excellent idea and am eagerly anticipating its arrival on YOUR boat. If/when you get one, you can monitor the current going into AND out of the battery, in amps. And even more important in amp-hrs, which shows the battery state of charge.

I assume the amp-hours used and replaced will be available. This should show you how the panels are doing their job. If the amp hours used is always out, then the panels are just partially offsetting the battery drain. If the use is negative (more into the batteries than out,) you've got great panels.

So, what would be really, really nice is if/when you get the meter you measure the battery usage (in amp-hrs) without the panels for a day and then the next day with the panels. This just consists of disconnecting the panels, writing down some numbers, reconnecting the panels and writing down some more numbers. this will give you an idea of exactly what the panels are doing. Not rocket science.

And that would be of interest to the whole C-Brat community.

Boris

 

[Grumpy]

What I like is the weather forecast for the next week which I assume is all part of Pat's plan for which I thank him

BTW I also endorse the Victron system. worth every penny.

M