• Ana and John

How we power our batteries - solar energy

Power, electrical power, is the all-time battle and headache of any long-term sailor, of course, we can plug to shore in the marina or run the engines to top up the batteries, but we want to be at anchor as much as possible and we want to sail not to motor.

If we wanted to be tied to a marina and use our engine's power up our lives we would have just bought a motor yacht instead of a sailing yacht!

How do we keep our batteries running?

With solar energy!

We have the strong conviction that we should be able to fulfil our power needs by capturing solar energy, as architects this is something that grabs our attention.

We have always been keen on the idea of having solar energy on our yacht and have read many stories about solar installations on yachts. But every time we see an installation it’s accompanied by a massive arch on the back of the yacht, which is something we really want to avoid.

We don’t like the idea of adding such heavy structure at the back of the boat even if including dinghy davits. We don’t like the designs or the detailing of how all that structure connects to the boat. It is a very personal opinion and I’m pretty sure many people are happy with that type of solutions and swear by them.


So being architects and hand on designers we decided we would find and build a solution that fitted our needs.

We figured that despite enjoying sailing with a completely clear cockpit the reality is that we don’t usually do much coastal or day sailing, we do mostly passages and we sail with our Golden Retriever, so shade is something quite important for us.

This means that in our case the Bimini is always open, providing cover over the helm and plenty of shaded space for Ella.

After the mishap on our Shakedown Sail when one of the Bimini front straps snapped in 40-45 knot winds we decided to reinforce the structure by replacing the two front webbing straps for stainless steel tubing matching the existing structure making a semi-permanent fixing point. We also added two additional reinforcement pieces in the back of the Bimini to remove a similar webbing strap reinforcement from the original design.

This reinforcement work set the base for what we wanted to do for our solar panels.

Because one of our concerns was the addition of extra weight in the back of the yacht and we wanted to have a very lightweight assembly that could be mounted directly on top of the existing Bimini structure, we decided to get flexible panels weighing around 3kg each.

Although these are much lighter than the conventional solar panels we felt that they weren't light enough to be stitched on the Bimini fabric but also not rigid enough to be attached on the Bimini frame (through the Bimini cover fabrics) and keep their shape with the wind, so we decided to fix them on a core flute plastic base with edge reinforcing the whole unit with zip ties (2 solar panels per base panel) and then zip tie the base panel to the stainless steel frame.

This gives a very sleek line to the yacht without the expense and weight of a “standard” installation.

We haven’t finished the aesthetical details that complete the installation, we are redesigning the Bimini covers to include additional fabric strips/pockets that will cover the edge of the base panels providing a better integration on the Bimini and protecting the panels from catching wind underneath.

Besides this almost imperceptible look of the installation, another thing that was on our mind was the ability to remove the entire assembly in just a few minutes while at sea without resorting to specific tools.

This was important to us in case of a stronger storm, but also if we need to do a fast repair or even an upgrade.

Currently, we have 4 x 180 watts flexible monocrystalline panels installed in parallel giving us 720watts (in theory - because the angle is never perfect and the boat is always moving).

We installed a Victron Energy MMPT 150/100 controller that neatly interfaces with our other Victron Energy products, the controller will allow us to upgrade the panels to 1450 watts. We have our Bimini earthed to the earthing system of the boat to provide protection from the panels.

By now we’ve figured out that while at the marina we discharge between 5-10% from sunset until a bit after sunrise, we expect to discharge 10-15% when at anchor if we leave the chart plotter and some of the other instruments on. Usually, we manage to have the batteries bank topped up between 9-10 am on an average day, but on non-sunny days we are not always able to fully recover the batteries and we are looking for new ways to provide eco power, wind/hydro generator but not yet convinced about efficiency and installation details.

From time to time we still think we will need a generator and this is on the list of things to consider but for now, we are still getting used to living on solar energy and fully understand our needs.

We believe that solar panels technology is getting better by the year so we believe there's a good chance that a simple upgrade of our panels in a couple of years will be sufficient to keep our energy needs fulfilled.

Current panels specifications (bought end of 2016):

• Max Power (Pmax): 180W

• Rated voltage: 12V

• Open Circuit Voltage (Voc): 20.30V

• Short Circuit Current (Isc): 11.57A

• Max Power Voltage (Vmp): 16.80V

• Max Power Current (Imp): 10.71A

• Module Efficiency: 20%

• Cable length: 900mm

• Dimensions: 1305(L) x 796(W) x 3(D)mm

• Weight: 3kg


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