noun; small and [possibly] particularly interesting item ofgossip orinformation...
The purpose is to share succinct posts about lessons learned, or things we use or do that work [or don't...] that are common to most of us boaters.
The goal is to garner feedback from those of you having first-hand experience with a different approach/ solution/ product/ or additional useful information to share...
Since we are asked this question often, it made sense to post a more detailed response.
We never assume what we are sharing is the ideal or only; it just seems to best suit our needs [and/or habits and/or budget] from our experiences thus far...Sometimes these Tidbits originate from a topic of discussion on one of the forums we participate in, and this happens to be one: Link to original thread [30-Dec-2018]
Since we are asked this question often, it made sense to post a more detailed response.
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Re: Solar panel output high latitudes?
Quote:
Originally Posted by sailingrock
Above 50 degrees latitude, what kind of output will solar panels produce in the real world. "Real world" as in typical weather conditions?
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Following are two real world solar panel installations which include accurate data gathered a bit further north of 50°— on the E Pacific side of things...
Note: I'll provide electrical data in watts [other values listed are nominal...] so you can crunch the numbers to derive your own conclusions and decisions based upon your individual electrical system and requirements...
Also note that climate is likely as much, if not more of a factor than latitude [addressed below...]
If you need a math refresher: [within the context of this post...]
Watts [W] / Volts [V] = Amps [A] Power
Watt-Hours [Wh] / Volts DC [V] = Amp-Hours [Ah (at specified voltage)] Energy
1 Kilowatt-Hour [kWh] = 1,000 Watt-Hours
Here are three handy online calculators:
- Amp-Hours vs Watt-Hours
- Ohm's Law
- Understanding Power vs. Energy [Watt vs Watt-Hour]
Background and reference:
We live onboard our boat fulltime, and are away from the dock [cruising and anchoring] ~9+ months each year.
Denali Rose's house battery bank capacity is ~10.8 kWh [~10,800 Wh, or ~900 Ah @ 12V DC (nominal) flooded lead-acid (FLA) batteries...]
Our average daily [24hr] energy consumption [averaged annually] is ~2.2 kWh [~183 Ah]. This includes running 2 refrigerators and 1 freezer full time, a variety of LED lights, computers and related devices, inverter for AC, the Espar diesel heater and ship's electronics much of the time...
Our 12V DC charging sources include:
- Battery chargers powered by either shorepower or an onboard 10 kW AC generator [2.2 kW combined capacity, all programmable]
- Alternator on the engine [1.4 kW with programmable external regulator]
- Solar panels [3 totaling 460 W; each with its own programmable MPPT controller]
- KISS wind generator [300 W]
First mid latitude solar panel example: [SV Denali Rose]
We cruised between 55° and 59° N along the SE coast [Inside Passage] of Alaska during 2018.
The 3 solar panels [460 W combined] on our boat each have their own Victron MPPT 75/15 controller. This not only helps mitigate [isolate] the affects of partial shading [i.e., loss of output] of a single panel, but also provides redundancy [two panels could share one controller if one became inoperative.
Here is a simplistic but effective demonstration of the effects of partial shading, and also compares series to parallel wiring of solar panels.Our 3 controllers share one battery voltage/temp sensor installed on the house bank, and are the sources of the solar output data in the 1st example, below.
It is worth noting that in our current latitudes, our house bank rarely achieves 100% state-of-charge [SOC] when we are not on shorepower. Therefore, the MPPT solar panel controllers are in a constant Bulk charge state. [i.e., outputting maximum possible into the battery bank when they are active; 100% Bulk duty cycle.]
The following data is for the calendar year 2018: [Aggregated data for 2019-present on will be published one of these days, but as of Aug-2023 the data still support the same conclusions...]
1) One 130W panel on top of bimini.
New in 2005; slightly pivotable. More frequent shadowing in this location— mainly from the 2 masts [and occasionally, a crewmember...]
The Victron controller reported it produced a total of 49 kWh in 2018:
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| You can just see a corner of the solar panel on top of the bimini, and the horizontal tubing it pivots on. [and our first mate, Gus...] |
2) Two 165 W [330 W combined] mounted side-by-side as one assembly on top of davits.
New in 2017; Pivoting to optimize sun angle. Typically fewer shadows than bimini top location.
These 2- 165 W panels produced a combined 193 kWh in 2018.
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| Here the panels are temporarily leveled to provide easy access to the ladder on the transom... Note the shadow [from the mizzen boom..] on the starboard panel. |
What was the approximate solar panel yield on Denali Rose for 2018?
Combined panel energy yield:
- ~49 kWh [bimini]+ ~193 kWh [davits] ≈ 242 kWh [total annual yield]
- 242 kWh [total annual yield] / 2.2 kWh [average daily consumption] ≈ 110 days of electrical consumption coverage from our solar panels
What percentage of our annual energy consumption does this represent?
- ~2.2 kWh daily consumption x 365 days/yr ≈ 803 kWh/year total consumption
- ~242 kWh [total solar/yr] / ~803 kWh [total annual consumption] ≈ 30% of our total 12V DC energy needs were replenished by our solar panels.
Even though this result is a very simplistic average [one that ignores many other variables- including seasons...] it is an indication [for us...] that our solar panels are worthwhile...
Other factors influencing insolation on the boat [besides latitude...]:
Aside from boat infrastructure shadows [e.g., masts and booms...] on the panels, and weather, we are also subject to geographical factors that affect solar gain on the boat.
For example, we often anchor in locations surrounded by tall mountains [e.g., 3-7,000 ft]. This often results in shorter periods of direct exposure to the sun in summer, and blocking it completely in winter... [Take another look at the photos above...]
For example, we often anchor in locations surrounded by tall mountains [e.g., 3-7,000 ft]. This often results in shorter periods of direct exposure to the sun in summer, and blocking it completely in winter... [Take another look at the photos above...]
I strongly suspect climatic factors affect insolation even more than latitude. For estimating climate and weather related factors [e.g., solar intensity and exposure periods, and percentages of cloudy days...] I like to use Weatherspark.com and Climate.gov.
We also optimize any potential gain from our solar panels by running the generator early in the morning [i.e., before the sun is intense enough to power the solar panels...] on days when the house bank needs a deep charge. [i.e., is approaching 50% SOC]
The battery chargers will get the bank back to 80+% SOC fairly quickly. The solar panels will continue bulk charging during the sunny portion of the day. [This is less important in winter months when days are short and solar gain is minimal...]
The battery chargers will get the bank back to 80+% SOC fairly quickly. The solar panels will continue bulk charging during the sunny portion of the day. [This is less important in winter months when days are short and solar gain is minimal...]
Second high latitude solar panel example: [monthly data from an optimized (auto sun tracking) land based system @ 65° N]
Family members in interior Alaska have 2 large grid-tie auto-tilt/tracking [max possible-output] solar arrays on a mountaintop [i.e., optimized insolation for the location...]
The 2 multi-panel arrays have a combined capacity of 5.5 kW.
Their data [kWh] follows: [Note the 2nd array went online in 2010...]
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| Go to live data |
Another personal demonstration of the efficacy of solar panels at mid latitudes:
We also have a truck camper and 2 enclosed trailers stored at 56° N.
Each has its own 100 W rigid solar panel [3 total; each with their own PMW controller] on an adjustable rooftop mount— which is typically tilted ~55° when stationary for long periods. [This angle also helps shed snow...]
Each has its own 100 W rigid solar panel [3 total; each with their own PMW controller] on an adjustable rooftop mount— which is typically tilted ~55° when stationary for long periods. [This angle also helps shed snow...]
These panels keep their respective 2.4+ kW [200+ Ah 12V DC] battery banks topped up year around:
The truck and camper each have 2 batteries [4 total] maintained by one 100W panel.
One of our trailers also has the batteries from our two ATVs tied into that trailer's solar panel circuit with individual DC - DC chargers...
I hope this will help you determine whether solar power is worthwhile for you in the latitudes and climates you are considering.
Related Resources:
Related Resources:
An excellent location based calculator for estimating solar output
Interested in our electrical consumption when at the dock in winter using electric heat?
Interested in our electrical consumption when at the dock in winter using electric heat?
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PS to SELF: DON'T CHANGE THESE IMAGES AS THEY ARE LINKED TO THE ORIGINAL FORUM RESPONSE...
Thanks for a nice, real world assessment of your solar capabilities. I have had to adjust my own expectations of what is possible with the five hundred watts of solar aboard Galapagos. While we have a more consistent source of sunlight in the tropics, shading is cuts actual energy output much more than I realized when I first started cruising.
ReplyDeleteI recently pulled my mppt controller from the system as it was behaving erratically and I feared it would damage the batteries. I have been using my backup PWM controller until I sorted out my options and now in La Cruz I have a source for the victron mppt controllers.
With your usage, would you go with Victron again? I note that you used smaller units rather than one larger unit. I assume this was to mitigate the effects of shading in a a multi panel setup?
Thank you Mike. I'm glad you found the article useful.
DeleteAs you have experienced, partial shading takes a larger toll than we first realize. And yes, that is the main reason I chose to install individual programmable controllers on each panel. [Only the output from shadded panels is affected- instead of the entire array.]
Multiple smaller amperage controllers don't cost much more than one large controller of their aggregate amperage, so it was an easy decision- not to mention the redundancy...
I'll also remind ourselves that, having sailed in the tropics myself, heat also diminishes panel output, so well ventilated panel mounts are advantageous...
RE: Buy Victron again? Absolutely. Their SmartSolar line with built-in BlueTooth [i.e., no dongle needed...] has been stellar. [I replaced a single Blue Sky MPPT controller that wasn't bad, but I wanted the BT networking and individual controllers.]
Download their free VictronConnect app to a laptop and/or an Android and/or iOS device and you have everything you need to configure, monitor, and automatically update firmware in each controller individually.
Victron has put together a very smart and affordable package with these units. [Don't forget to add one of their battery voltage and temp sensors- also BlueTooth. All controllers share one volt/temp monitor...]
Mexico has been good to you guys... 25 years ago we had to head stateside for everything...
Best wishes optimizing your solar output!
PS Mike: Your good questions prompted me to update the article.
DeleteI also included a brief video which does an adequate job demonstrating the effects of partial shading of panels, and also demonstrates the difference between parallel and series wiring of the panels.