THE ELECTRICAL PROPULSION SYSTEM -THE BASICS       

The good news and the bad....    The great thing about building a hybrid yacht is the you never run out of things that can go wrong; however, now its built, everything seems to be working (Hmm ...so I must have overlooked something).  No seriously....... its true - electric drive is reliable and maintenance is a breeze. 

You will see from these pages that I am happy to point out the negatives as well.  Perhaps the biggest minus is the intial outlay in terms of time and cost.  Not to be underestimated.  However, like many things in life, once the investment is made, benefits will be reaped for many years.  Long after the dinosaur diesel motor has died....your electrics will be almost as good as the day you installed them and with almost no intervenig maintenance.  A sharp contrast to maintaing a marine diesel as any experienced yachtie will agree. 

The System....    There are 2 engines that propell the yacht (1 x Dieasel and 1 x electric sitting side by side) each having its own propellor shaft.    Any vehicle is a hybrid when it combines two or more sources of power.  Hybrid cars are becoming well known; for example Toyota "Prius".

Questions of efficiency....    Sailing Yacht "Solace III"  gets an added boost of power from 12 solar panels a wind generator and "sail regeneration". The lions share of the power still comes from running the diesel, but thankfully I have halved the engine hours, or put in another way I have doubled my fuel economy.  That is my long term average over the last 3 years. 

The user can choose how efficient....  How much of a rush are you in?   The exact ratio of Diesel power to solar power is entirely dependand on the user.  For example, a relaxed cruise amongst islands, meandering from anchorage to anchorage (modus normale for me),  can be carried out entirely on solar power as the daily demand on the battery is matched by the suns input with just enough spare to run the high efficiency (LED) lights and high efficiency refrigeration (water cooled, super insular) and of course music.  Alternately, crossing an ocean against the prevailing wind (some "gung ho" nuts do that), would be almost entirely dependand on running the diesel.  The same is true for the hybrid car, for example the Toyota Prius running at highway speed non stop relies only on the petrol motor; but stuck in traffic "meandering" will just use electric.

 

Start with a few diagrams to explain.

 DIAGRAM 1    XXXXX

 DIAGRAM 2  XXXXX

 DIAGRAM 3  XXXXX

                                  DIESEL MOTOR                                     

The diesel motor can operate as either a normal diesel boat motor with its own direct propellor or it can be a generator to power the electric motor / propellor or a compbination of both to suit conditions.  The elctric motor is always on even if just "idling".  The reson for this is that at "idle" speed the power drain is tiny (200 watts), but the speed gain is significant (1 knot).  This is due to 1/2 knot that would otherwise be lost to the "dead" propellor drag" and 1/2 knot gain due to thrust.  This discovery was unexpected and a win.

 SOLAR PANELS 

"Solace III" has 8 side mounted panels and 4 aft mounted Panels that also provide sun shade.  All Panels fold in for stormy weather and in extreme weather they have a quick release system so they can be taken into the safety of the cabin and clipped in out of harms way.

Toal nominal capacity is 700 watts, though in reality with cloud / low sun etc I average 200 watts.

 WIND GENERATOR 

One Air Marine wind generator one of the industries best.  A noisy bugger to be honest so sometimes I shut it down .  Comes into its own when its blowing like stink, cloudy and I'm at anchor.

SAIL REGENERATION

Regeneration occurs when  sailing at over 4 knots and the propellor "free wheels" thus turning the electric motor into a generator.  This has been a low priority job so its on the "to do list".  This is mostly due to the cost of stepping up  voltages and to do it efficiently.  I have done it as a test set up and poven the my 15" prop will give me about 100 watts of power at 5 knots.  Not a lot of power but every bit helps.

BATTERY STORAGE

The weak link in all hybrid systems is the large bulky size of the battery.  Luckily for yachts we carry a whole lot of lead ballast in the keel and so why not make that lead usefull as a lead- acid battery.  I have 6 large batteries down there now, having dug out 600 kg lead (a non fun job).

This give several hours of silent electric only motoring (actually 24 hrs duration at low power and 3 hours at high power) before the diesel generator gets turned on for recharge.

PUTTING IT ALL TOGETHER 

 A typical day goes like this:  Wake up and do couple of hours on electric motor only.  Maybe some wind so 50/50 sails and electric.  At some point in the trip I estimate my "payback" options of the with respect to recharging batteries.  It may be the elements have been kind and solar, wind generator and sail prop regeneration will do the job but mostly the diesel takes the lions share.  The aim is to have the batteries full again at the end of the day by the time I drop anchor.