Tag Archives: solar

Frugal Boater: Pearl Lee Solar 2.0

On Pearl Lee we make our own electricity, mostly from solar. Occasionally we found ourselves falling a bit short of our needs and supplementing our solar with a generator.  This was mainly during the short days of winter, but also during periods of high use. We don’t have an “electricity budget” as many cruisers do. My goal is to have enough power without any worries. Hence, Pearl Lee Solar (PLS) 2.0.

Our PLS 1.0 configuration consisted of two  Hyundai 280 watt solar panels wired in series and mounted on our dinghy davits (hanging over the back of the boat). Power from these went through a Midnite Solar Classic 150 controller which charged our eight golf cart batteries with nearly 900 amp hour capacity.

We found a solar panel dealer in Miami with very competitive prices, so for PLS 2.0 we decided to add two Suniva 280 watt panels. Bonus, our Suniva panels were made in the USA. The new panels are mono-crystalline, 60 cell panels to match our Hyundai’s as closely as possible. They look different because the backing material is black instead of white.

Initially my plan was to mount these over our bimini  (canvas cockpit cover). The problem I ran into was the mounts to do that would raise the panels dangerously close to the boom, and cost as much as the panels themselves. While searching for a solution, I found some very reasonable mounts at McMaster Carr. This meant removing the canvas and using the solar panels themselves as a hardtop. Pro tip: When drilling the frame slide a piece of scrap between the frame and panel to avoid hitting the panel when your drill breaks through.

This location is impossible to keep in full sun throughout the day, so our goal was a 50% increase in electricity production. Early results are showing a bit more.

The mounts worked great and the panels went on easily. Due to the curve of the top bows, I added some inner rails made from aluminum angle to support the outboard edges where I wanted them. They’re cambered a bit for rain runoff.

Wiring was pretty straight forward, the new panels are wired in series and the new and old strings in parallel. This may not be optimal, but it’s the best our present controller, a Midnite Solar Classic 150, can do.

We’re still working out some aesthetic details like properly joining the panels to our dodger (canvas cover/windshield at the front of  the cockpit). I’m also planning to extend the sides out and down a bit to mimic the protection our canvas bimini gave us.

Pearl Lee Solar 2.0 is working well, but needs a few finishing details. Meanwhile, we already have the design and materials for PLS 2.1. Stay tuned.

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Pearl Lee Solar 1.0

 

Frugal Boater: Solar Charge Controller Basics

With all but the smallest of solar panels, you’ll need a charge controller. A charge controller goes between the solar panels and the batteries. It’s job is to limit, or control, the power your panels put into your batteries.  This keeps you from destroying expensive batteries by overcharging. There are two types charge controllers.

Power Width Modulation (PWM) controllers are relatively inexpensive. They work by literally switching the panels on and off very rapidly. That works fine as long as your panel voltage is fairly close to your battery voltage. If you’re a weekend boater who just wants a small panel to keep your battery topped up while you’re away, a PWM controller might do the job. Using a PWM controller will limit the size panels you can use because they don’t have the capability to change the voltage, only turn it on and off.

Multi Power Point Tracking (MPPT) charge controllers are a big step up in performance  and price. These controllers actually adjust voltage/current in an attempt to wring the most power out of your panels. They also have the capability to step the panel voltage down to whatever your batteries need. An MPPT controller takes the 60 volts coming in from our panels and steps it down to our battery charging voltage (around 13.5). When the voltage comes down the amps go up, so very little power is lost in the controller.

Beware of cheap “MPPT” found on Ebay and the like. Some are actually PWM  controllers with “MPPT” printed on them. Since the charge controller is the heart of your system, and could prove dangerous to you and your batteries, it’s best to stick with a quality unit from a reputable manufacturer.

A standard system with one MPPT controller is striving to optimize all panels, meaning that during partial shading some panels are running higher and some lower than optimum. No panels are really performing their best because the controller is working with an average. This is where MPPT optimizers on each panel can be useful. In an environment where shading is unavoidable, this allows each panel to work independently for optimum results. Obviously no two systems and shade scenarios are identical, but tests with optimizers show that during partial shading power output can be increased by 15-25%. In an environment where partial shading can’t be avoided, and space is limited this can be important. That sounds a lot like a sailboat doesn’t it?

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Pearl Lee  Solar 2.0

Frugal Boater: Solar Panel Basics

Solar panels convert solar energy to electricity. A panel is a collection silicon wafers called “cells” wired together to get the required power and voltage. Ideally, all your panels should be exactly the same. In our case they are not, but they’re “close enough” since our old and new panels are all 280 watt, 60 cell panels.

A little spot of shade on the corner of a panel, or a thin line of shade from a rope might not seem like much, but it can drop the power output of the shaded panel significantly. This is because the voltage of the shaded cells drops, rendering them nearly useless. In older panels this shaded area can actually suck power from the sunny cells. Luckily newer panels have bypass diodes that disconnect and bypass the shaded area. The bad news is panels have only three or four bypass diodes, so even a small shadow can result in a large drop in output. This is a big problem on sailboats with masts and rigging casting shadows. I’ve even seen panels mounted with straps over them!

We use mono-crystalline panels because they perform slightly better under less than ideal conditions. You can recognize mono panels because you can see the individual cells which are actually thin slices of a silicon ingot. Multi-crystalline panels are poured, so the entire panel will be one continuous sheet of  silicon, often with some multi-color light refraction. The performance difference is pretty slight, so don’t be afraid of multi-crystalline panels if the price is right.

Ideally, solar panels should be at a right angle to the sun’s rays. Doing so gathers maximum solar energy per square foot of panel. Static installations can easily approximate this, but on a moving boat it’s quite a challenge. I’ve seen a few articulated panels, but  to be effective they take some baby sitting. Most boaters just deal with less output from un-aimed panels.

Solar panels are usually wired in series (+ to -, – to +) to create “strings”. Wiring in series increases voltage, but not amps, so wiring is cheaper and easier because higher amps requires thicker wire. Although there used to be problems with shade on one panel having a negative impact on the entire string, bypass diodes effectively fixed that issue. Strings are then wired in parallel (+ to +, – to -) at the charge controller to keep voltage at manageable levels.

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Pearl Lee Solar 2.0