Updated Solar wardrobe

Its been two years since I last posted on Hive and boy, a lot has happened to me in that time.

It is past time for an update post or two.

Where to start?

I've changed marina, but am still in sunny Cyprus, which is a perfect segway to my most obvious upgrade ..

A lot more solar panels

When I last posted I had 3.5kW of solar panels (13 x 270w aluminium framed glass PV panels) mounted on my roof and bimini area.
This was sufficient for house loads in the sunnier part of the year, but electric propulsion has always been my destiny, and this requires a lot more power production.

Vertical Bi-Facial Solar Panels

My first solar upgrade was another 3.27kW of vertically mounted bi-facial solar panels (6 x AEG 545W bi-facial PV panels). They are mounted vertically, allowing sun to hit both sides of the panel and attached outside my deck guardrails (3 starboard and 3 port).

I think I am the first boat in the world to utilise vertically mounted bi-facial solar panels!
And they work amazingly well, producing more than twice as much real world power as my 3.5kW of horizontally mounted upward facing panels.

Vertically mounted bi-facial solar panels are a new and somewhat counter-intuitive development in the world of solar power production, but are gaining substantial following because they produce more real world power than perfectly sited and angled land based single sided panels.

On land solar panels can be permanently fixed at the perfect angle for the latitude to maximise electricity production. But on a boat like me this is impossible, as I'm always moving around!

This means boats usually have solar panels facing directly upwards. But this creates numerous problems:

• they get shadowed by the mast, boom and all the various lines and stays a sailing boat like me has;
• they get dirty quickly, losing efficiency and need to be cleaned regularly;
• they get very hot (which is uncomfortable for me and reduces efficiency by 0.5% per degree Celcius) and are difficult to cool, a huge problem for flexible solar panels mounted on fibreglass or bimini material and the reason sailors are often disappointed with the performance of the much lighter flexible panels;
• their peak output is in the middle of the day with little output early in the morning for recharging batteries drained overnight and in the late afternoon and early evening for peak air-conditioning and cooking loads;
• they are never at the perfect angle unless it is mid-day at the equator (I've never been there and sailors avoid it because of The Doldrums.)

My vertical bi-facial panels address all these problems and have other unexpected advantages:

• no shadowing on the external face;
• stay clean as dirt falls off and is easily washed away by rain;
• stay cool because of excellent air-flow on both sides and because even in still conditions, hot air doesn't get trapped by the panel, it rises vertically along panel and escapes;
• production better matched to usage: they produce substantial power from the moment the sun rises and keep producing power until the sun sets, providing at least 4 hours per day of additional solar production, thus reducing the time that batteries need to cover loads - less expensive battery capacity is needed to cover loads.
• they are often at the perfect angle for maximum production, in mornings when facing east and later afternoon when facing west.
• they gain additional light from reflections from the water and from the light coloured deck further increasing electricity production.

There is only one thing I don't like about them is that they increase windage forward of my pivot point affecting my steering in very strong winds (30+knots). But this can be countered by various means including strong engines, adding windage rear of pivot point and removing other sources of forward windage.

These panels were installed 18 months ago now and I'm very happy with them. They have survived serious storms AND little kids and produced huge amounts of power.

Hull mounted vertical flexible solar panels

As is obvious from the first two photos above, these vertical bifacial panels are not the only side mounted panels I now sport.

Much more recently the trusty Máté, a Hungarian alpinist, and hardworking crew-member installed at further 5.28 kW of 110w flexible Sungold flexible solar panels riveted (using aluminium rivets) to my hull (24 panels on each external hull).

He can be seen here using his alpinist skills (which he gained the love for by climbing my mast) to install the panels. While he is very close to the dock, he said it was easier that standing on the dock. I am so light that pressing the drill and rivet gun on my hull pushes me away from the dock, making installation more difficult.

He was also careful to minimise the covering up of the names on my hull - those people who contributed to my construction. Photos were taken of me before installation and any people's names covered up by panels will be redone elsewhere.

While these panels are not bi-facial, they are lighter, add no windage and my aluminium hull is an excellent heatsink (mitigating the heat problems usually associated with flexible panels).

So far they seem to be performing well but wintertime in a marina with blockages to the sides is not the best time to test them. I look forward to being free on the open sea soon to get better data.

I am not the first catamaran to have hull mounted solar panels, as Sunreef, the Polish luxury catamaran builder, has been integrating them into the fibreglass hulls of their new "Eco" range for a couple of years now.

But I am the first aluminium catamaran to have hull mounted flexible panels with heat sinking into my hulls and into the water.
I don't know how Sunreef addresses the heat issues, but I am sure the Sunreef hull mounted solar panels cost 10x what mine did.

Certainly those Sunreefs need every kW to keep the lights & AC on in their over-weight hulls. The Sunreef 80 "Eco", which is has a slightly smaller footprint than me, displaces 66 tons lightship compared to my 27. That means its solar power to weight ratio is half mine. More on this later.

Those Sunreefs may have more fancy jewellery and clothes than me, but my body is thin, lithe and naturally beautiful in glorious aluminium nakedness.

Enough bitching....

Replacing old glass PV Panels with new flexible ones

The original 6 x 275W (1.65kW) glass solar panels installed by my builder Michel on my bridge deck roof in 2017 were replaced with 11 x 270W (2.97kW) flexible Sungold panels. An unnecessary porthole was welded shut to allow a better use of my roofspace.

These new panels are much more efficient (22.62% vs 16.9%) and lighter (5kg vs 20kg) providing much more power for less weight in the same space and a walkable surface (no more kids being shouted at "Get off the solar panels!). They are also much lower profile and better looking. Hopefully my aluminium roof provides enough heat-sinking into the hull via the aluminium frame which supports it.

3.24kW of flexible solar panels on back platform

Another 3.24kW (12 x 270W) Sungold flexible solar panels were installed on my back platform and an unused boom (shown in photo below) removed to reduce shading.
The surface is still walkable and can still be used for sundowners with beanbag seats in the warmer weather.

Total installed Solar Production so far

A summary of the solar arrays currently installed:

a) 1.65kW (6 x 275W) of old glass horizontal panels installed on bimini 2.5 years ago - these are to be replaced with flexible panels once my cloth bimini is replaced with aluminium to allow heat sinking and avoid fire risk;
b) 2.97kW of new flexible horizontal panels on bridgedeck roof;
c) 3.24kW of new flexible horizontal panels on rear platform;
d) 3.27kW of bi-facial vertical glass solar panels on deck guardrails;
e) 5.28kW of new flexible vertical solar panels on hulls.

Total: 16.41kW
7.86kW horizontal panels & 8.55kW vertical panels.

I still have another 27 x 270W (7.29kW) flexible panels onboard waiting to be installed on a new extended aluminium roof replacing the bimini and as needed on parts of the trampolines (like La Vagabonde III).

Máté is keen to install solar panels on the side of my masts, so more narrow flexible panels will need to be purchased.

Solar Power to Weight Ratio - Why it matters.

I would like to get to 27kW of solar PV panels installed to achieve a solar power to weight (displacement) ratio of 1:1 (27kW & 27T lightship). One watt of solar power per kg of displacement.

This 1:1 solar power to weight ratio is the holy grail for a solar powered vessel and one which, until now, only purpose built solar research vessels like Tûranor PlanetSolar (93kW & 85T) have been able to achieve.

In order to move a boat forward its propulsion mechanisms need to oppose drag, which rises exponentially with velocity.

When an object's velocity is held constant at one meter per second against a constant opposing force of one newton, the rate at which work is done is one watt.

This the definition of a watt.

Thus for a given hull form, drag is directly proportional to displacement and thus the power required to move a given hull form at a set speed is directly proportional to displacement.

A catamaran with long narrow hulls like mine is the most efficient (lowest drag) hull form.

So given the most efficient hull form, the solar power to weight ratio determines both:

1. the maximum speed any vessel can continuously motor 24/7 on solar power alone - ie the speed at which range is unlimited;

2. the shortest time a vessel can cover a given distance on solar and battery power alone (given fixed size battery) .

The vast majority of production solar electric yachts being sold today have ratios below 0.5:1 and often around 0.3:1.

• The Silent 80, from the brand that pioneered long distance solar propulsion weighs in at porky 75T lightship and only has 26kW of solar panels: 0.347
• The SunReef 80 is 66T and has a maximum of 32kW of solar panels: 0.485
• The only production multihull that even comes close is the Serenity 64 with 24T lightship displacement and 15.6kW of solar panels which is 0.65

What this means is that these vessel are not serious long distance solar electric cruisers, unless you are happy with speeds under 4 knots.

In contrast, I am already able to cruise long distances at much higher speeds with a combination of sail and solar propulsion.

I will show you the calculations in my next post when I update you on my new 50kW electric motor and many other upgrades.

Fair winds and following seas!