Heaving to to recharge?

[noelex 77]

Originally Posted by Na Mara

I plan to fit (and this is not a theoretical plan, I am ordering the components now) 600W of solar (300W semiflex on the pilothouse roof, 300W of movable rigid panels between the wind turbine masts) and 2 420W silentwind generators. Total daily average generation should then be about 4.7kWh.

Unfortunately, I think you are a little optimistic with these theoretical production calculations and are likely to be disappointed in the real world. Even if I am wrong, your proposed system will at best will only work in areas of very good or excellent solar insolation. This restricts your potential cruising ground.

Originally Posted by Na Mara

There is no more space for solar that can be deployed underway!
There is no more space for wind generators!

An option to consider is also installing LPG cooking. You can still use electric cooking on most occasions, but when electrical energy is short (such as offshore sailing or at anchor with poorer conditions) switching or partially switching to propane will solve your electrical dilemma and remove the need to heave to in ideal sailing conditions (this seems a shame).

[Jammer]

Originally Posted by Na Mara

When sizing my system I'm working on the following assumptions.

2.5kWh daily consumption stationary (covers a cool-box, all LED lights, electric cooking, and appliance charging).

An electric galley will make it hard. People use propane for a reason.

I'm assuming average 10kn windspeeds Rayleigh distributed with 20% wind shear. That equates to an expected/average output from silent wind generator of 35W or 0.85kWh per day.

I'm assuming 5kWh/m^2 daily irradiation, which is the yearly average in the Caribbean and the summer average in the Baltic. I'm assuming 20% efficiency of the panels and that 1m^2 of panel equates to 200W. All of this equates to the assumption that 200W of solar will net me 1kWh of energy per day on average.

For wind, I don't know if that assumption will hold. Most people follow tradewind routes on passage and sail with the wind aft of the beam. Wind turbines run on apparent wind, not true wind.



On solar, as a rule of thumb, it is reasonable to assume average output for (5 hours) x (rated capacity in watts) for most applications, and save yourself a lot of math. The partial shading inherent in a sailboat installation reduces this somewhat.

I plan to fit (and this is not a theoretical plan, I am ordering the components now) 600W of solar (300W semiflex on the pilothouse roof, 300W of movable rigid panels between the wind turbine masts) and 2 420W silentwind generators. Total daily average generation should then be about 4.7kWh.

So you get somewhat less than (5h x 600w =) 3 kwh a day form the solar,

probably less from the wind than you think. I would guess you'll have a little less than 4 kwh a day, gross, on average, on passage. Controller and battery losses will take another 5% or so, with lithium chemistry. I would expect that you'll get around 3.5 kwh a day that you can actually use.

I judge my game to be pretty much upped to the max yet still I do envisage the need to take time out to recharge or run the engine occasionally. As I don't like doing the latter, the former is appealing. Hence the thread.

If you want to "up your game" you will have to work on conservation and power sources other than electricity. Add vacuum insulation to your fridge. Shut off the freezer during passage. Switch from an electric galley to propane or butane, at least while on passage, or at least have it as an option if you find you have an energy deficit.

Now you might say, well you should fit a Watt and Sea or and EFOY or something else and cover the envisaged deficit.

Those are expensive, specialized solutions that make sense only in unusual cases.


Which is why most people are prepared to run an engine when necessary.

[Na Mara]

It’s nice to have the math confirmed.

I am not shifting on electric cooking. It’s about a kWh a day (we typically only boil water twice a day and make one hot meal) and in return for that I have no more sourcing issues for propane, no adapter issues, no safety issues, and I get a cockpit locker back. Further, the present setup is outdated and dangerous and needs replacing anyway. Replacing the whole system with a quality safe replacement cost close to as much as fitting an electric cooker so I went for the cooker.

With 3-4 kWh a day of generation I can cover the cooker when stationary without any issues. It’s the autopilot that blows the energy budget.

What I might ultimately consider if I find myself regularly faced with the choice of stopping to recharge or running the engine is a hydrovane. The hydro vane massively increases redundancy onboard -backup rudder, backup autopilot, backup emergency helm - and for me it’s the equivalent of fitting 300W of solar panels or 2 further wind turbines when underway. It’s a bit ugly but you can remove the rudder and vane to lower its visual impact when not in use. This I might well do, but I’ll try the system above first. They are expensive bits of kit.

[El Pinguino]

Not sure about the Watt and Sea but an old fashioned towed generator works for me - constant 5 amps at 5 knots.
Coupled with a windvane and a bog standard Westerly - designed to keep pommy beer warm in winter - fridge filled with frozen vacuum packed meat I have never felt the urge to 'heave to to recharge' even on 44 day voyages.

Speaking of water turbines. I was looking at this lawn trimmer in a mate's shed recently.
It has a flexible drive shaft made of ?? . Marinise the design a little bit, reverse the energy flow by fitting blades at the bottom and a generator at the top and bingo! a far cheaper option than the Watt and Sea.

[hpeer]

I have a aux rudder vane on my 33’er. It works well enough and is a natural fit for a tiller pilot (Pelagic) when motoring. You lock the wheel to take out any prop walk and the AP has a neutral helm. Same when sailing if you have some wx helm, correct with the wheel.

[Jammer]

Originally Posted by Na Mara

I am not shifting on electric cooking. It’s about a kWh a day (we typically only boil water twice a day and make one hot meal) and in return for that I have no more sourcing issues for propane, no adapter issues, no safety issues, and I get a cockpit locker back. Further, the present setup is outdated and dangerous and needs replacing anyway. Replacing the whole system with a quality safe replacement cost close to as much as fitting an electric cooker so I went for the cooker.

I get it; besides, your boat, your choices.


For many reasons I would like to switch to an electric galley but have chosen not to do so at this time due to impact on electrical energy budget at anchor and on passage. We have therefore retained the gimballed propane range with updates as necessary for safety.



We are experimenting with induction cooking, an electric teakettle, and an electric skillet as means of reducing our propane consumption at times when electricity is abundant.


An alternative to consider is a butane box stove to augment your electrical installation. Each of those 8 oz cans has the same cooking energy in it as 2 kwh in your batteries. Switch over to them when you have to conserve electricity:

[hpeer]

Kerosene is still a viable alternative.

Many hate it but some us love it.

[Na Mara]

I was thinking of a camping stove as a backup for the electric cooker but this butane stove is much more useful. Thanks for the tip Jammer.

[Happ]

I have anchored to just recharge myself. Get a good night sleep. Make a really nice meal. Never for batteries.

[Gianluca]

Hello, I misunderstood the question of recharging, meaning battery power. Many have answered already and I think that just steering by hand half of the watch saves already 50% of the highest consumption, the autopilot.
Heaving to on a long offshore passage is a nice way to recharge the crew, prepare a good meal, take showers, go back to a stable environment.

[Cynara]

We've hove-to to recharge our personal batteries

[svfinlandia]

Originally Posted by Pete7

Why not just run the engine for a few hours and motor sail? In my youth we did that when the lights started to get dim at night. Running the engine also means hot water, so time for the crew to have a good wash every few days.

Pete

That is my solution. Motorsailing at night for a couple of hours usually tops up the batteries well enough that I don’t need to worry about it.

Al, S/V Finlandia

[FlyingScot]

I think you're expectation of kWh harvest/made underway is pretty far off in the wrong direction. I'm amazed at how much shading the sails create. The harvest day is reduced by a few hours significantly reducing the harvest. I also question how your panels won't be shaded most of the time between sails, rigging, wind generator x 2, etc. Rigid panels tend to harvest much more than non rigid ones.

We have a Honda 2.2kw for backup but it is dangerous to use underway on our boat. CO poisoning is a real threat with the way the wind swirls back into our cockpit.

Reduced consumption and use of fossil fuels are your choices.

[MJH]

Originally Posted by Na Mara

Has anyone ever heaved to or even anchored just to allow the renewables systems to catchup and recharge the batteries?

Basically, sailing loads are typically very roughly about 50% higher than stationary loads on most boats. As most people sit stationary for most of the time it makes sense for them to size their charging system accordingly. Thus they are typically sized to cover their stationary usage with a bit of a margin but maybe not quite the sailing usage.

To make the math easier, imagine that you typically use 2kWh a day stationary and 3kWh a day in motion. and that your average input from your charging sources is about 2.5kWh a day. If you have 5kWh of LFP batteries (about 400Ah) then, assuming you set off with full batteries, you can sail for around 8 days before the daily deficit catches up to you. At this point a lot of people would put the engine on and just recharge fully, but why not just stop for a bit, either at anchor or heaved to, and let the bank slowly catchup again before carrying on one's merry way.

Of course one solution is just to increase the amount of charging so that it is sufficient to cover loads underway. That is certainly an option, but what about if you are in circumstances where the generation falls off. Is just pulling over to wait for recharging to catchup a good idea in these circumstances or is it just better to just fire up the engine?

No, I have never hove-to on a passage to charge my batteries, sounds silly to me.

First, complete a daily electrical power consumption plan by including EVERYTHING that consumes power and the number of estimated hours per day it will be used. I recommend the Pacific Cup 2012 Sample Energy Budget that is on their web site. It is an Excel sheet that you can modify to fit your situation. The goal is to learn how much you use and determine how you are going to replenish that power with diesel, solar, etc. I made one for my roundtrip to Hawaii and never had to start my diesel once to charge the batteries. Knowledge is power. "Plan for the worst, hope for the best, but realistically, expect a combination of both."

Second, when your electrical power is diminished for whatever reason you start turning nonessentials electrical items off, that's where a windvane is a savior. As captain I am the "Amp czar" and will always turn nonessentials off. On a passage electrical power and fresh water rule. I once lost complete power crossing the Gulf of Mexico and made my destination with windvane, Garmin portable, and a large stack of AA batteries...that's all you really need but a depth finder (lead line) would be nice approaching the harbor.

[Shaneesprit]

Nope - just turn off what you don’t need. To save power.
I have a small power consumption, but this year I had some charge or battery issues. Yet to be resolved - Auto pilot quits on Low Voltage.
But would never stop due to lack of power, think I would sell my boat if it didn’t work without batteries.