Solar in PNW: actual output per Summer day?

[MV Content]

I am about to install 500-750 watt array on my 60ft motor yacht. I've done my sums, and I'll be feeding 880 Amp hour golf-cart House bank, through an Outback MPPT controller.

The only gap in my calc is the ACTUAL output: has anyone got any relevant experience in PNW? This would help me to decide on array size.

 

[maxhopper502]

First up I would like to say what a beautiful vessel.
I installed 2800 watts on my old girl and I know it's overkill but I had the room and I designed the Bimini so that the top was covered only in the flexible panels sikaflexed to the frame.
On a normal day my batteries are chockers by midday but overcast wet days like today I'm lucky to see 40 amps (24 volt) going in for the day.
With a relatively flat roof the panels probably only get an hour or so of close to the rated power.
I don't think anyone would ever complain about too much power.
Cheers,
Adam

 

[twistedtree]

I've got 750W of panels with an Outback MPPT sitting in the PNW currently, so pretty much the exact setup you are contemplating. Unfortunately I haven't been on the hook enough, and not at all in the summer, to really have a good sense yet of the output.

What I do know is that 750W isn't enough to run the boat. Not even close. It definitely reduces generator run time, but doesn't eliminate it. So, I would put as much wattage up as you possibly can. More panels is relatively cheap, and your controller can handle it. On most boats, available space is the limiting factor, so use all you can get. I envy Adam's 2800W.

 

[twistedtree]

BTW, you probably already know this, but cutting your power loads is at least as important as getting more solar, arguably more important. Switching to LED lighting, making sure you have TVs and other entertainment systems that actually turn off when you turn them off, making sure all plug in transformers are electronic, not magnetic, etc.

Other owners of my model boat report at-anchor power draw in the 30-50A range. Mine is 9-18A, and it wasn't hard to do.

 

[Donsan]

... making sure you have TVs and other entertainment systems that actually turn off when you turn them off, making sure all plug in transformers are electronic, not magnetic, etc.

How do you identify these qualities in TVs, entertainment systems, and transformers? It would seem to me any system controlled by a remote would need some power draw and how many Admirals can live without remotes.

Is there something on a transformer that identifies it as electronic or magnetic?

 

[DavidM]

A very broad rule of thumb is that a solar panel. mounted horizontally and not tilted will generate 1/3 of its wattage capacity in amphours on a totally sunny day. This works for southerly latitudes in the winter and northerly latitudes in the summer.

But the PNW is northerly and somewhat cloudy. So look at the solar insolation map for a horizontal plate given here: http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/serve.cgi

Somewhat surprisingly it shows the PNW at only 25% less than the SE US on an annual basis.

If you just look at July, here: http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/serve.cgi then that little corner of the PNW is about the same as SE US.

Both the July and annual values are about half of what a fully sunny day would produce.

So cut the above rule of thumb in half for an average summer day and maybe in 1/3 for year round. In the summer a 750 watt solar array will produce about 120 amp hours daily.

Those values are averages and might be suitable for a full time cruiser. If you are like most of us and plan your trips around sun, then maybe you could add 50% to them.

David

 

[kolive]

MVContent,

Here is a link to a post I replied to awhile back that came from The Willard Boat owners group that I am a part of.

mv.VikingStar: A Year with Solar, or is it: “Wait until he figures out what a monumental waste of money that was”. . . . .

He gives some actual data for his solar install in the PNW.

Looking forward to your thoughts as you pursue this.

 

[DavidM]

It takes some searching/reading to find it, but VikingStar has 490 watts of panels and they put out an average of 135 AH (at 12V presumably) during the summer months. That is a bit better than my rule of thumb indicates above, but it is real data.

David

 

[dannc]

How do you identify these qualities in TVs, entertainment systems, and transformers? It would seem to me any system controlled by a remote would need some power draw and how many Admirals can live without remotes.

Is there something on a transformer that identifies it as electronic or magnetic?

For 120 AC, you can use this, http://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU to measure power going to the device.

Not sure why I did not think of this before, but my multimeter has a clamp and I would guess it could see the power draw from a device that was turned off. Never thought to try before.

I have heard of people putting their stereo and TV equipment on power strips so that they can REALLY turn off the equipment.

Later,
Dan

 

[twistedtree]

How do you identify these qualities in TVs, entertainment systems, and transformers? It would seem to me any system controlled by a remote would need some power draw and how many Admirals can live without remotes.

Is there something on a transformer that identifies it as electronic or magnetic?

For TVs and other entertainment devices, reading the specs is the best source of info. A good device will specify the "turned off" power draw. It might be called standby or something like that. EnergyStar improved teh standards a while back and that prompted manufacturers to get better about stand by power draw.

For best results, and LED TV with low standby power would be best. A 40" LED is under 100W operating (probably 60W in practice), and 0.3W in standby. A similar sized LCD could easily be 100-150W and who knows what in standby.

The biggest offenders for remaining on even when turned off are Cable TV and Satellite TV boxes. They typically draw the same power whether they are turned on or off. Turning them off does little more than turn off the lights on the box. I've seen cable boxes that draw 30W 24 hrs a day, 7 days a week, and consume more power than a refrigerator. This continues because the cable and sat companies convinced the EPA to exempt them in the Energy Star rules.

As for plug in power adapters, or "wall warts" as they are often called, the easiest way to tell if it's electronic vs magnetic is to feel it when it's plugged in but not powering anything. If it's warm, then it's just a transformer (magnetic). If it's cool, then it's a switching power converter (electronic). I haven't seen a magnetic wall wart with a new piece of equipment in a long time, but they were pervasive just a few years ago. So any older equipment is likely to have them.

By the way "touch it an feel if it's warm" is a great way to get an idea about other electronic equipment. Feel your cable box after it's been off all night. It will still be nice and warm. Feel your TV too. It should be cool to the touch.

 

[Donsan]

For TVs and other entertainment devices, reading the specs is the best source of info. A good device will specify the "turned off" power draw. It might be called standby or something like that. EnergyStar improved teh standards a while back and that prompted manufacturers to get better about stand by power draw.

For best results, and LED TV with low standby power would be best. A 40" LED is under 100W operating (probably 60W in practice), and 0.3W in standby. A similar sized LCD could easily be 100-150W and who knows what in standby.

The biggest offenders for remaining on even when turned off are Cable TV and Satellite TV boxes. They typically draw the same power whether they are turned on or off. Turning them off does little more than turn off the lights on the box. I've seen cable boxes that draw 30W 24 hrs a day, 7 days a week, and consume more power than a refrigerator. This continues because the cable and sat companies convinced the EPA to exempt them in the Energy Star rules.

As for plug in power adapters, or "wall warts" as they are often called, the easiest way to tell if it's electronic vs magnetic is to feel it when it's plugged in but not powering anything. If it's warm, then it's just a transformer (magnetic). If it's cool, then it's a switching power converter (electronic). I haven't seen a magnetic wall wart with a new piece of equipment in a long time, but they were pervasive just a few years ago. So any older equipment is likely to have them.

By the way "touch it an feel if it's warm" is a great way to get an idea about other electronic equipment. Feel your cable box after it's been off all night. It will still be nice and warm. Feel your TV too. It should be cool to the touch.

That is good info. My boat doesn't have a TV yet so it we get one, it will be EnergyStar compliant. I bought a new LED TV for the home before Christmas and have been amazed at how little power it uses. I think it the rating was $9/yr for electricity. Most of our electronic devices are very new. I plan to install LED lights.

 

[MV Content]

Many thanks for all of the very relevant and useful information, gents. I think I am on the right track.

When I bought Content, she consumed 350+Ah per day, through a heady cocktail of 110, 32 and 12v systems. I had to remove the 1960 Onan genset two years ago, and the original 1928 White Superiors were replaced last year. The daily consumption is now under 200Ah, and will come down to 140 or so in May, when I complete the lighting re-vamp to LED. The fridge and freezer, both 110v, are the main culprits, so I’ll need to monitor those.

The panels will go on my doghouse roof, which is shade-free on almost every point of sail. Judging by what I’ve read here, I should get 225Ah per day or more, during our cruising season, from June to September, and that’ll be just fine.

I’ll post updates along the way!

 

[twistedtree]

Sure sounds like you are on the right track.

 

[rjtrane]

Download Sun Seeker Lite - a free app. It gives you the angle of the sun above the horizon throughout the day for your location. Subtract this angle from 90 to give you the angle of the sun from the perpendicular (to the panels). Multiply the cosine of this angle by the rated watts of your panels. This gives you the MAXIMUM potential of your panels. You will get losses from your controller and from the battery and from the inverter.

At least this gives you an idea of the total potential for your latitude. The Outback is a great controller - mine have been working continuously since 2008.

I suggest you wire your panels in series - mine operate at a nominal 80v charging a 48v/1,000 AH Lithium battery. The boat has not used any other source of power for ALL electrical needs for 3 years. Of course, Sunshine Has 6kW of solar panels.

 

[MV Content]

Well, I installed my 750watts of panels ten days ago, and I'm in love! Excellent service and advice from Jeremy, at Webster Solar in Vancouver. The outback MPPT controller shook hands immediately with my inverter (also Outback, so while I'd expected it to, it was nice to see it seamlessly integrate). I flicked the switches at 07:00, and watched the meter climb straight up to 28amps. This is in the PNW in May, before breakfast.

By the time I'd had my eggs, she was into the 30s, and she peaked at midday on 41amps. I pulled over 300ah that first day.

The next few days were occasionally overcast, but I saw 250+ah each day: I even got 160 on a day where it rained 50% of the time.

All in all, a great success. I even started stretching the batteries, turning the immersion heater on for an hour each morning, and watching the batteries recover (without the engine).

At the same time, I'd increased my house bank from a miserly 440ah to 900ah, and the combination of the two factors now means that I can confidently stay on the hook this summer, probably indefinitely, if the sun is shining.

Really glad I made the jump, and can heartily recommend it to others in the PNW, who might have doubted the sun's potential (as I had done!)
Eamonn.

 

[Moonfish]

REALLY like reading your personal testimonial on this! Glad it worked well for you and your beautiful vessel. We may be following suit next season...

 

[DavidM]

Wow that is great performance. You beat my rule of thumb of 1/3 the wattage rating in amphours on a sunny day, even at PNW latitudes. But we are pretty close to the summer solstice. Maybe I should up it to 40%.


David

 

[fryedaze]

That all lines up with my experience with my new 450 watt semi-flexible panels. I figure we use aprox 300 amp-hrs a day. The 450 watts of panels come up a little short but my gut and napkin calcs tell me that 750 watts would cover me on normal days.
Dave

 

[twistedtree]

I'm finally getting a little feel for mine as well now that I'm anchoring out. It looks like my 750W of theoretical max power actually puts out around 450-500W. That seems a bit low to me, but might be more because my batteries have not been very discharged, so the charger might be throttling back.

But the good part is that during the day while at anchor, the panels pretty much carry the boat's power load.

Just took a look at the charge controller. It says it put out 3.5 kwh today, but I was underway most of the day with the main engine pumping out power, so not the best test. As soon as I get a full, sunny day on the hook - that will be the real test.

 

[Insequent]

Dont underestimate the impact of shading, even if just from an antenna, on the power output. When in the PNW I was regularly getting over 60 A into the batteries from an 1820 watt array. At the time I did not check for shading.

Since being back in Queensland, I have seen up to 90 A if I lower the antenna's, but I am yet to try and quantify Ah for a day on the hook. I agree that it is important to measure consumption of various items. Like me you might get some surprises and modify some things.

 

[MV Content]

I have zero shading on my aft roof, where the panels are mounted. However, they are horizontally oriented, so I'd expected to lose 25-30% efficiency. The reality is looking like 33%, with peak performance logged at 41amps. The really cool thing is that, once I'd stopped checking the numbers every five minutes, the thing just quietly works away in the background. I'm sure I'll just start taking it for granted shortly . Oh, and it does work when it's overcast...20amps is pretty well the minimum I've seen.

Of course, as the bank SOC gets above 85% or so, the controller steps back, and I don't see any amps....

 

[twistedtree]

Looking at your numbers again, it looks like we are getting exactly the same performance once you account for my 24V system. I max out around 20-21A, or at least that's the most I've seen and it was with a good load on the batteries so the charger wasn't throttling at all. And the other equipment is the same - 750W of panels with outback charge controller.

I too have no regrets having installed the system, and only wish I had space for more panels.

Oh, and Insequent's comment about shading is very true, and a good reminder for me. My radar scanner stops at any random location and is as likely to be shading the panels as not. I should get in the habit of climbing up there and swinging it out of the way. What I'd really like to figure out is some way to align/position it without having to climb up on the hard top. It's not my favorite place to go. But I haven't come up with an idea yet.