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  • Writer's pictureSailing The Dream

Flexible solar panels - second season of use update

Last year we started our shakedown season (which we call season 0, since it was more about testing systems than actually sailing) by installing 4x180 watts flexible solar panels, our main concern was the addition of extra weight to the stern of the yacht, plus we got a good deal since these four panels costed us around the same as one rigid panel of 110-140 watts would’ve cost in Portugal according to the quotes we received at that time.

You can read further details on blog post How we power our batteries.

So how are we now on this sensitive matter of power?

I think it’s important to detail the difference between the two seasons to better explain the current train of thought.

On Season 0 - Shakedown, we sailed in the North Atlantic waters from August until November, passing by the South of Portugal and Spain up to Gibraltar, crossing to Morocco and sailing down its Atlantic coast, crossing to Madeira Archipelago and then returned to Lisbon.

At that time of the year, the water temperatures in this big area range between 14ºC-20ºC and the air temperature 20ºC-35ºC.

During that entire season, with the exception of the nights spent at sea and two nights on a mooring ball in the Deserted Islands of Madeira, we stayed always in marinas, although very rarely connecting to shore power. We would only connect when we wanted to use the washing machine, the setting at that time required us to plug to shore power or to a generator in order to use the washing machine.

Despite not being connected to shore power and most of the times with the solar panels oriented to the least favourable direction we managed to use all our appliances normally with the care that had already been established as a rule.

As the temperatures got hotter we identified some insulation problems in the main fridge and the freezer, that we tackled during winter, before season 1 started.

On Season 1 - Sailing the Western Mediterranean Sea, we sailed just like on the previous season from Lisbon to the South coasts of Portugal and Spain, but this time passing through Gibraltar towards the West Mediterranean coast of Spain and then heading towards the Balearic Islands, Sardinia, Corsica, the Tuscan Islands and then down through the Pontine Islands then we will head all the way to Sicily and Tunisia.

This season started late March and will last until October, so the temperatures range was quite diversified starting with 10ºC-15ºC in the first months but settling to 30ºC-35ºC during the summer months, the same reflecting on the water temperatures that started at 14ºC while still in the Atlantic, passing the 20ºC marker in May while in the Balearics and reaching almost 30ºC when we reached the Italian Islands.

During most of this season in particular since arriving the Balearics, we stayed at anchor with occasional stops in marinas when there weren’t any anchorages near where we needed to go (Palma de Mallorca and Rome).

Our power production was affected in a way we were not expecting, considering that the previous season most of the times, whilst docked in a marina, the panels were facing the north quadrant instead of south and we always managed to get to 100% charge by mid-morning, it was quite surprising to find that while at anchor with all the rocking and swinging even on very shiny days getting to 100% charge was happening later and later in the day. And as the summer fully kicked in not even being able to get to fully charged.

As summer advanced the usage of our electrical appliances had to be reduced to pretty much no use at all, the fridges became inefficient again despite the tweaks done during winter, forcing us to give up on the freezer use and reducing for a long period the usable area of our main fridge. Only the drinks fridge coped with the increasing temperatures. A few more tweaks on the main fridge insulation and by mid-August we managed to be able to use the entire fridge again instead of having to section it into a smaller volume.

Our refrigeration systems energy consumption (excluding the use of the freezer that had to be turned off at the beginning of summer) more than doubled while our usage of other electrical appliances simply ceased.

The rising temperatures of air and water are the main cause for this reality, although a water-cooled fridge is supposedly more efficient than an air-cooled one, I’m not sure what to say when the sea water is almost at 30ºC if it makes any difference to an air-cooled fridge when the air temperature is 35ºC+.

Off course we can’t also deny or forget that with such temperatures the solar panels themselves are more inefficient on power production also, long are the days where we would get peaks of production of 500+ watts and averages above the 350 watts. Now the peak of production rarely hits the 300 watts marker staying at an average between 150-220 watts.

Are the solar flexible panels failing?

At the moment we are not sure, I guess only when the temperatures start to drop we can be sure if the reduction of power production is related to the high temperatures or to the end of life of these panels...


- Our fridges are trying to cope with extreme heat (air and water) driving power consumption up

- all refrigeration units insulation should be further upgraded and thermal bridges further investigated

- out of the three separate units we have (main fridge, freezer, drinks fridge) we are only using two of the units, having given up on the freezer and therefore reducing our provisioning options

- with such extreme temperatures, we sometimes need to cool down the yacht interior resorting to a fan or even a portable air conditioner because of our comfort at night but also Ella’s

- power consumption significantly increased despite most appliances not being used at all

Total power production is at best shy off 2Kwh per day, recurrent numbers just slightly above 1Kwh opposed to the almost 3Kwh we were used to on last season and beginning of this season.

Victron Energy Color Control and BMV-700



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