Going Green(er)

We've made a couple of big changes aboard Field Trip over the past several months.  We significantly upgraded our solar installation & added wind generation.

Admittedly, I'm not a big believer in wind & solar energy cost effectiveness (no subsidies) for private consumption.  Technology is getting better and the return on investment improving.  The principles are good, the raw economics not so much.  There are no subsidies on a boat to go green.

For us, it is less about cost effectiveness, and more about reducing our need to burn diesel to supply our energy needs.  We have a finite capacity (159Gallons/600L) and prefer to use this for water making & when absolutely necessary - propulsion (that's why we have a sailboat...grin).  We like the idea of being completely 'off the grid', having complete reliance on the weather for energy generation.  

The trick is weather.  Some days it's sunny.  Some days windy.  Some days both.  Some days neither.  The amount of wind, sun and rain you get is dependent on season, latitude and just good ole mother nature.

Sun and Wind Overview

Let's look at how sunshine varies by latitude and time of year.  The farther north from the equator, the more variation you have with sunshine.

Using New England as an example, the variation between 15 hours to 8.5 hours of sunlight is significant.  However, if you are on a boat, this may not be as significant since most people are not living on their boats in the New England winter.

Going farther south, towards the equator, there is a lot less variation in sunshine, less than 2 hours throughout the year.

The second consideration, and in some cases the most variable is wind.  For us, it was a matter of figuring out where was the boat going to be 'most' of the time, and does it make sense to have wind generation?  If we were going to have our boat in New England or the Chesepeake during the summer, having wind generation would be an expensive idea, given the winds are not very strong most of the time.

How strong is strong enough for wind generation?  That depends on the wind generator.  Without getting too technical, a good rule of thumb is you need at least 10 kts of breeze to get 'some' power from your wind generator, 15kts+ to really see some meaningful output.

For Field Trip, we plan on keeping her mainly in the trade wind regions.  Trades blow constantly from 15-20+ knots most of the year around the globe.

Prevailing Trade Winds

Green Power Generation Aboard Field Trip

This is a large topic, that has taken us over a year of living aboard to figure out what works, and what things we would do differently.

Solar Power

Lets start with solar panels.  There are many different types on the market.  In the past several years much has changed with solar panels, their uses, efficiency and overall design.  

View of Solar and Wind Generation on Field Trip
Aboard Field Trip, we have 6 BP panels - four 50 watt and two 80 watt.  These panels are of an older technology, and do not handle shading well.  If there are shadows, even small, the power output drops 90%+.  I've measured this, and have confirmed how painful any shadow can be.  

Newer panels are MUCH more efficient when it comes to shadows, having a reduction in power closer to the % of the panel being shaded.  Ripping off the panels and putting on news ones may happen at some point in the future.

The next important consideration with solar panels is the solar controller.  This is the device that controls the output from the solar panels and converts the power to usable amps for the batteries.  Technology in this space has changed significantly as well.  We had an old style controller installed from the factory.  The newer technology called MPPT is about 30% more efficient in converting solar power to amps for the battery.  Click HERE for a detailed overview of the technology.   

We upgraded our unit to the Outback MPPT controller.  It was one of two manufacturers (Morningstar being the other) recommended by an expert after he assessed our installation in Annapolis.

To the left is a photo of our output on the Outback.  You can see the In of 17.0V and 8.4A. This is what a non MPPT controller will output to the batteries - i.e. our old controller.  

With the Outback, you can see we are getting 10.7A to the batteries, 27% more power than 8.4A.  

Essentially the controller is converting the volt difference 17V vs 13.4V -- 3.6V to amps.  This is the magic of the MPPT algorithm.

It is important to note, not all MPPT algorithms are created equal.  There are some cheaper versions on the market with 'MPPT' algorithms, that are not as efficient as some of the top vendors - Outback and Morningstar.

The next logical question, how many amps per day are we averaging with our MPPT controller?  Well, the good news is this is very easy to answer exactly, as the controller keeps a history of over 100 days of use, so I can see each day how many amps we are dumping into our house bank of batteries. 

Below is a 14 day view of Field Trip while in Puerto Rico on the hook.

So what does an average of 94 amp hours a day mean?  In practical terms, we are staying virtually power neutral to slightly positive on 94 amp hours aboard Field Trip.  Not 100% when we start to use laptops, autopilot and other higher power draw items, but nice to know we can leave our boat for a month and not worry about killing our batteries on refrigeration alone.

It is important to note, you must be sure your refrigeration is properly tuned.  We had ours serviced in Brazil.  They fixed a leak, but ended up overcharging our unit...and we were using more power than necessary to keep the fridge and freezer cold.  More on refrigeration, tips, tricks, etc. in another blog entry.

Wind Generation

This is hotly debated in forums and amongst sailors.  Frankly, if you plan on being in the trade wind zones for most of your sailing, it is a no brainer - if you are not getting your power needs met by solar alone.  

The biggest 'poo poo' I hear against wind is the 'noise factor'.  This is very true for some - but not all generators.  I would only recommend two wind generators - Duogen 400 or Superwind 350.  These are both virtually silent in a blow.

I was sold for over a year on the D400.  It was the generator I was going to get in the states.  After doing more research, and reading Practical Sailor (think Consumer Reports for sailors) - they chose the SuperWind 350 as the best overall generator in light wind - twice.  

So, I said if it was good enough for Practical Sailor, it was good enough for me.  Was I wrong?  Sort of...

Below is a comparison of both the Superwind 350 vs. Duogen 400 - based on manufacturer supplied data.

What do you see?  I saw a potential revision in my decision for the S350.  Why?  Well, 'most' of the time winds are going to be < 20 knots.  In this range, the D400 is superior in output.  Between 20 - 30 knots, the S350 is superior.  What was up with Practical Sailor?  Well, they didn't review the D400.  If I had created my own comparison of the two as I did for this blog, I 'may' have gone with the D400. 

Since we've been sailing hard to the wind since leaving the Bahamas - our apparent wind has not been less than 20kts - and I've been mentally in good shape about our decision.  It's sitting at anchor when it is blowing 15kts that I cringe once in a while...grin.  In the end, either wind generator is leaps and bounds above the alternatives and we are happy to have this as renewable power source aboard Field Trip.


  1. It's nice to be off the grid. Either way, you're still adding power and that will help in the long run. I hope it all works out for you all.

  2. Hello Field Trip Crew,

    Mark, do you have other pics(from the deck) of the S350? How is it mounted and how the wires are run into the cabin area.

    Field Trip has an excellent blog.


  3. Sure Mike. Let me know email address and I will send you picks.

  4. Mark, there's something wrong with your math in comparing the old vs. new solar controllers.
    Remember that power is always measured in watts, and watts are calculated by multiplying the voltage by the current (amps).
    Your two controllers are feeding the same amount of power (measured in watts) to the system - 143 watts. 17.0v x 8.4a = 142.8 watts.
    13.4v x 10.7a = 143.38 watts.

    Statistically identical. It's quite possible that there is less loss in the new technology controller, but according to your own battery monitor, this isn't the case.


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