Last month we looked at solar panels as a potential energy source aboard. This month we compare wind generators to solar panes and see which system is a better choice for your vessel.
Just like with solar panels, if a boater is considering a wind generator there are some obvious and not so obvious decisions to be made in determining the best possible choice. Of course the first question is whether the turbine has the required output that will keep battery banks topped off. When looking at manufacturers’ specifications, it is important to note that most rate their generator’s output based on high wind speeds in the vicinity of 25-30 knots. I don’t know many boaters that enjoy being on the water in those kinds of winds for any length of time, especially while at anchor. Others rate their units based on steady, unwavering wind speeds, which usually don’t exist except in a test wind tunnel. So whatever the output at those speeds you can do some basic calculations and figure realistic output at lower, closer to real life conditions. You must also determine if there is an appropriate place where a generator can be mounted that will allow for clean wind to drive the rotor and keep its fast spinning blades away from the crew? What kind of wind is there typically in the waters that will be sailed? Is it gusty or will the boat be in protected marinas with little or no wind? Is there room for a larger rotor or is a compact size necessary? Will the unit need to be field serviced in remote locations and if so how difficult would repairs be?
As with solar panels, there are different wind generators or wind turbine designs found aboard vessels today, each with their own output capability, drawbacks and advantages. All are made up of similar components such as a rotor with three or multiple blades and a generator with some sort of internal or external regulator and overload cutoff. Regulators make sure batteries are not overcharged and turn off the generator once a predetermined level is reached and back on when levels drop. Some can be programmed for specific sizes and types of battery banks, such as AGM, gel or wet-cell batteries. The two most common varieties found aboard are smaller turbines that are made up of blades less than 48 inches in diameter and larger turbines that have blades in the five-foot range. Output from wind turbines can be either initially in AC power, which proves to be a better choice, where long wiring runs have to be made (but with a higher cost because more components are necessary), or direct DC output.
Turbines with smaller blades do not have the output power of their larger competitors but do have some advantages. Because the blades are smaller and lighter they require less wind to get them moving, which means they will start spinning at lower wind speeds and will start producing energy or ‘cut-in’ at lower speeds. These units typically perform better than larger models in moderate speeds such as 10-15mph, which is typical in many protected anchorages. So if you plan on spending the majority of your time in protected harbors and anchorages then a smaller wind generator may be your best choice. Test data on multiple small wind generators, completed recently by Practical Sailor, revealed that under the typical conditions found in an anchorage with winds at 10-15mph, an output of 1.3 amps could typically be produced. This falls into realistic output experienced by cruisers with generators of this size.
Larger wind generators with rotors of up to five-feet produce more power at higher speeds and can actually rate an impressive output if the wind is stronger. Their output can average around four amps in 10-15 knots with intermittent gusts. If the wind is consistently low, however, their cut-in speed is higher and their resulting output can be lower than that of a smaller turbine. If that low wind is punctuated with decent gusts, the power created by those gusts can make up for the lower output at lower wind speeds and the average can in fact result in more power generated. If higher output is required then one should consider the winds that will be encountered and, if gusty winds are prevalent, a larger rotor system may be just the ticket.
Unlike solar panels, wind generators are not silent. Some are considerably noisier than others. That noise can be bothersome for some, especially in a quiet anchorage. Smaller rotors with multiple blades tend to be quieter, with larger triple rotor wind generators typically being the noisiest. Manufacturers have diligently been working on getting their units quieter over time and for the most part newer units are quieter, but there is still a big disparity between models, so be aware.
If you are boating in an area with windy and gusty conditions and little sun with limited space aboard then a wind generator (and one with a larger rotor) is definitely your best choice, beating out its smaller competitors and most single solar panels. If conditions are going to consist mostly of fair winds and protected anchorages then a smaller wind generator might be your best choice. Even under ideal wind conditions, newer solar panels, configured and sized appropriately, will generally out-produce any of these wind generators … but only in sunny or relatively bright conditions.
So which is better? I spoke recently with the dockmaster at a local marina who pointed to a boat that was totally off the grid and did not have a shore power cord plugged in, and I posed the question to him. Under ideal conditions and with all things being equal, the answer for him was this simple – a combination of both.