Ask SAIL: Generating Energy While Underway

I just read Nigel Calder’s article on the costs of generating energy (“The Cost of Energy,” Dec. 2012) and found it fascinating. I understand there is a high cost for generating energy at anchor by running an engine, but is there an additional cost to generating energy while underway? If my engine is running the alternator to recharge the batteries, as well as moving the boat, surely it must add to the load and increase my fuel consumption. Is the increase significant, miniscule or somewhere in between?
Author:
Publish date:
Social count:
0

Jay Adamsson of Kingston, Ontario asks:

I just read Nigel Calder’s article on the costs of generating energy (“The Cost of Energy,” Dec. 2012) and found it fascinating. I understand there is a high cost for generating energy at anchor by running an engine, but is there an additional cost to generating energy while underway? If my engine is running the alternator to recharge the batteries, as well as moving the boat, surely it must add to the load and increase my fuel consumption. Is the increase significant, miniscule or somewhere in between?

Nigel Calder replies: 

In almost all cases, due to the manner in which a propeller loads an engine, engines are never operating at peak efficiency underway. However, as a general rule, the higher the ancillary loads from things like alternators, refrigerators, etc., the more efficient they become. Fuel consumption rises, because the engine is doing more work, but it rises proportionately less than the increase in work.

NigelCalder_4

To put it in terms of a power bill, instead of paying around $0.20 per kilowatt-hour (kWh) of energy used, you will pay $0.15 per kWh. If usage goes from 10 kWh to 20 kWh, the bill may rise from $2.00 to $3.00, but the unit cost will decline. Running an alternator underway, we are not only getting housepower at a much cheaper rate than when charging at anchor, we also get our propulsion power at a cheaper, more fuel-efficient rate, because the engine is operating more efficiently. The bottom line is that any time you are running your engine for propulsion purposes at less than, say, two-thirds of its full speed, there is a significant benefit to loading it up with other jobs.

Got a question for our experts? Send it to sailmail@sailmagazine.com

Related

GG17-SAONA47-DX0796

Boat Review: Fountaine Pajot Saona 47

Here’s a riddle: What is less than 50ft long, has two hulls, three big cabins and four decks? Answer: The Fountaine Pajot Saona 47. In fact, it may even be five levels if you count the large engine rooms. This boat is a “space craft” in every sense of the word.DESIGN & ...read more

RichardBennettMIDNIGHT-RAMBLER3249x202

Storm Sails: Do you Need Them?

Many sailors embarking on ocean passages will take along the obligatory storm jib and trysail, with the vague idea that they may come in handy. Few sailors, however, have a real understanding of how and when to set them.It doesn’t help matters when we hear from seasoned sailors ...read more

IntheWater(1)

Boaters University Unveils Rescue Course

Boaters University has just announced its latest online course, Safety & Rescue at Sea, taught by Mario Vittone, whose name you might recognize from the pages of our sister publication, Soundings Magazine and his Lifelines blog.Mario Vittone is a retired U.S. Coast Guard rescue ...read more

IMG_20170920_132819

How to: Installing New Electronics

I had been sailing my Tayana 42, Eclipse, for a few years without any installed electronics on board. I’d gone pretty far up and down the New England and Mid-Atlantic coasts with paper charts, the Navionics app on my Android phone, a hand-bearing compass and the ship’s compass. ...read more

02-Douglas-Adkins---Coriolis---Orcas-Island-KevinLightPhoto

A Phoenix-like Concordia

Cutting a fine wake on the cobalt-blue waters of West Sound on Orcas Island, Coriolis sparkles like a diamond. Her lovely silhouette is offset by emerald forests that frame the ocean, within spitting distance of the border with Canada. Seen up close, this Concordia yawl is a ...read more

IMG_1051

The Latest Boat Trends from Dusseldorf

The world’s biggest boat and watersports show, held in Düsseldorf on the banks of Germany’s Rhine River each January, is the place to scope out emerging trends in the boat design and building.What would be the new trends for 2018 and beyond? Hint—sophisticated electronics figure ...read more

TOTW_PromoSite

SAIL's Tip of the Week

Presented by Vetus-Maxwell.Got a tip? Send it to sailmail@sailmagazine.comGood ConnectionsI wish I’d had a dollar for every time I’ve cobbled together an electrical fitting with a “that’s good enough” shrug. An old shipwright once taught me that “good enough is not good enough” ...read more

tides2

Gear Test: Tides Marine Sailtrack

Gravity is an important force at work on a sailboat. It keeps the boat upright, it makes the anchor drop to the bottom, and it makes the mainsail slide neatly down the mast to be flaked and put away at the end of the day… until it doesn’t.In the case of dropping the mainsail, the ...read more