Quote:
Originally Posted by aqfishing
Most engines are propped to match the engine horse power. The numbers just don't add up for my simple brain! If you take 20Hp of a 29 or 45 hp engine, it does not leave much to turn the prop. This would lead to over working the engine when you under motor. Unless the system disconnects when not needed?
Using 44% of your engine power to generate electricity cannot be efficient, and will also leave your vessel underpowered, unless you have overpowered your engines to allow for the alternator demand.
As someone said, there are no free watts!
Solar is great, and I will be going strongly in that direction to reduce running the generator...
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While you are correct that props are matched to the engine - without a variable
pitch prop there is only one sweet spot where the prop even gets remotely close to using 100% of the power available for any given
RPM. That is the homework that Integrel did for quite some time and with a lot of proprietary mapping they are able to siphon significant amounts of power from the engine with absolutely no effect on performance.
We've had a dual Integrel system on our Bali 4.8 for about a year and a half and it's life changing. If you know anything about Bali's - they are power hogs with a full size
refrigerator, not to mention we've installed a fully
electric galley, and 6 - 48v air conditioners (though admittedly don't use very often). The Integrel(s) operate completely in the background and gently
ramp up or down depending on your needs of operation and a variety of engine parameters. The large belt has a clever serpentine design that maximizes pully contact and an idler to dampen whatever shock loads there are - though by watching the
charging display you can clearly see that Integrel adds and removes loads smartly and digitally using PWM to where there's never an instantaneous on/off. One interesting data point: I just changed our Integrel belts at 500 hrs not so much due to wear but they have stretched a bit. The actual condition of the belts is far better than the stock alternator belts on the Yanmars.
In our case with 4JH57 Yanmars we see about 7-8kw per engine around 1500-1700 rpms when
charging only. In our case charging rate is limited by heat at the alternator - I suppose if we increased
cooling flow we'd see even more. Regardless, at 16kw going in it doesn't take long to recharge our 43 kWh of MG batteries. After 575 hours the Yanmars run like any others we've operated and
oil consumption is nil.
Fuel useage when charging appears to be about 1 to 1.5 gallons per hour per engine - pretty much in line with what our previous Onan generator used while putting out significantly less power (due to running at a static
RPM regardless of load).
As far as redundancy - obviously 2 engines is nice but in our case there is also the layer of 12v
electrical system originally installed at the factory. You can even leave the 12v
inverter in to power the
refrigerator. By using DC-DC chargers - the 48v bank constantly keeps the 12v fully charged so 12v. appliances/windlass are never starved for voltage and always operate with full power. Should the 48v system fail for whatever reason - the 12v alternators are still operating and, while you won't have Inverter power - almost everything else on the boat remains functional.
As for
solar - I wouldn't call it "great" - we have 2200 watts on a stern mounted rack. We typically average 6 - 7 kWh per fully day of charging in the
eastern Caribbean in
winter months...about what a
single Integrel generates in 45 minutes of operation. By the time you spend the
money on the rack, the
panels, the MPTT's, and the
installation - it's a terrible investment. But overtime it does add up and is a nice shade for the
dinghy.
Disclaimer: other than a satisfied customer I have no interest in Integrel other than to see them succeed. Being successful in any startup business is tough and these guys have gutted through a lot of ups and downs and I believe fully in their
service and product!