Deciding on a green power strategy is a bit like herding cats. ;D
I've found there are 5 criteria that I need to weigh:
1) load on the system both underway and on the hook
2) converting the claims of green machines to real world/your location numbers
3) determining the storage
bank for your requirements
4) deciding which system(s) give you the best return for your investment
5) determining that generally speaking one system won't do it all
(1) You first need to know what your power requirements are. A good DVM and a shunt can do most of the measurements for you. You also need to investigate alternative low power
alternatives (more efficient fans, LED lighting
, adjusting the freezer/fridge for less power draw, etc).
(2) While I have no doubt the numbers manufacturers provide are real, I don't think they're real world - or based on my location. I tend to divide solar by 4 because I'm not going to keep the solar panels
perpendicular to the sun throughout the day, I may get 8 hours of daylight but not 8 hours of good charge light, panel performance is dependent on an unobstructed view of the sun (including keeping the panels clean), temperatures, and the losses incurred in getting the power from the panel to the controller to the batteries.
The same can be said for wind
generators. While these green power providers can produce power 24/7, chances are the wind isn't consistent where you are, they are mechanical devices rotating at high speeds, and can be a real safety
hazard. Their power curves (wind speed vs output power) look impressive but again, the wind isn't always at the speed you need.
(3) I think the general consensus is that you need a battery
bank that has 4x the capacity of the maximum load you need per day. Deep discharges tend to reduce battery life. If you choose to never discharge lower than say 70% (realistic) and the maximum charge you generally get is 95% (generally unrealistic) then, in reality, you have 25% of the capacity of the battery system to work with. If it's a dark few days your batteries may not reach the magic number, and therefore your capacity will be less.
We all tend to have engines and alternators. Many folks dislike running the engine
to charge batteries so having a large alternator
can both reduce the charge time and provide a higher load on the diesel
. Some folks go the way of gensets, either diesel
or gas, but there are maintenance
considerations as well as noise
and pollution concerns.
OTOH, if you live in a cold climate, running the engine may help heat the boat, charge the batteries, and heat the hot water
(4) There have been very successful and happy cruisers who sailed with only one system. The Pardy's use a small portable solar panel to do their limited charging
. Some boats go with just the engine and sometimes a big alternator
. Others have high power requirements and opt for solar, wind, or gensets. The decision on which to use is dependent on you - and there are no wrong answers or choices; only your decisions.
Everything costs - and you can either pay for it now or later. I think many of the members here tend to have a diesel and one other system. Proponents of a variety of systems have provided real world information on use, problems and features. I agree that there is no perfect solution and that by filling out a spreadsheet, the answer will not magically appear. I also think that mechanical systems are more prone to failure than those with no moving parts
, but at a cost.
(5) A solution that works for you is based on your power requirements, your realization that reducing the load is far cheaper than buying
and adding to the complexity and as a result, reducing the reliability
a boat is unique and therefore presents unique problems. We all have minimum standards in order to be comfortable and safe. We all want to be able to enjoy this unique form of travel, lifestyle, and adventure.
Sometimes you can't get there from here, at least within your budget