Solar vs Wind
- February 28th, 2009
- in Yachting
Light Blows: Solar vs Wind – Which natural energy source is better? – A common question from those wishing more independence afloat is: Which is better, solar panels or a wind generator? Let's compare benefits and liabilities.
Solar PROS: Solar panels are VERY cool. Fairly inexpensive, completely quiet & clean, no operating cost or maintenance ever, and they work especially well in the Caribbean. By their nature, it is difficult for a solar array to overcharge a significantly-sized battery bank. Recent improvements in efficiency have endowed them with outstanding output from a reasonable size.
Solar CONS: They are big and have to be mounted somewhere. To maximize the potential wattage-per-square-inch, aiming them directly perpendicular to the sun is beneficial. Locating them in an area that avoids shadows is important.
Wind PROS: A wind turbine puts out lots of energy in big wind. Surpasses solar with a smaller footprint—it mounts on a pole or in your rigging. Modern wind generators are brushless with sealed bearings that may last for years, providing perfectly clean energy production.
Wind CONS: A good one is more expensive than a typical solar array. It is a mechanical device, and therefore has the potential for maintenance issues. Although is has a smaller footprint than a good-sized solar array, much thought must be put into mounting so that it is structurally strong and doesn’t tangle in running rigging, sails, someone’s head, etc. Can be noisy and annoying to you and/or your neighbors. They might well need monitoring and attention to prevent overcharging conditions or storm damage. Also, if you love quiet and serene anchorages, or even worse, marinas, the wind will be partially or totally blocked and kill the output of the wind machine.
So to answer the question, Which device should you get first: a) SOLAR or b) WIND, the answer is in fact: c) the largest, highest quality battery bank you can afford to fit on your vessel.
You see, the solar or wind devices only generate at certain times in limited amounts and cannot run the ship’s electrical needs 24/7. The batteries do this.
The best wet-cell batteries for deep-cycle operation have beefy plates that can physically accept a good charge and tolerate the adverse conditions experienced on a boat. They cannot put out the CCA [instantaneous current] that a starting battery is designed for. (Batteries get amps from surface area of the plates; lots of thin plates = lots of instantaneous amps. But thin plates degrade more quickly than thick ones over time and are subject to warping in adverse conditions.) To get decent output from a battery with beefy plates it needs to be big and heavy, but the technology is very old and proven reliable when used properly.
Gel-cell batteries were developed to be physically tougher than wet-cells, but have inherent characteristics which make them a bit more sensitive electrically, so care must be taken to observe these issues. Because of a slight difference in chemistry, the non-fluid state of the electrolyte, and the need to prevent gassing during charging, gel-cells have different charging requirements.
I would recommend AGM [Absorbed Glass Mat] batteries for the small-to-average cruising boat. They are less expensive than the best wet-cell or gel-cell units, and utilize standard charging systems. They are traditional in appearance, but the insides are full of high-tech innovation and utilize recombinant technology. These so-called maintenance-free batteries are very durable and were initially developed for use on military aircraft and have several distinct advantages for use on a boat.
When the batteries have been chosen, they must be placed somewhere on the boat to afford secure installation, adequate access, with much consideration given to the weight distribution aboard. The wiring of the batteries is critical: an expert system designer will allow for direct runs of very large, high-quality cable with accessible, secure, corrosion-proof and physically protected connections. This designer must have a deep knowledge of overcurrent protection and charging requirements and use the simplest devices to allow for proper protection and control.
Once the batteries are installed, get some solar panels. For an off-shore cruising boat, I would recommend simplicity and structural integrity in lieu of maximum daily output—no tracking, although there is a new tracking mount being advertised that seems well thought out. It would increase the output of a smaller panel by allowing you to turn it to face the sun.
Solar technology is growing very fast, so updated information will lead to superior decisions. Second-generation, "thin-film" production techniques have reduced manufacturing cost and recent advances, heralding the third-generation products, have greatly increased efficiency. Light-weight, flexible panels have been used in interesting locations where rigid units wouldn't work.
A wind generator combined with the solar panels can make a boat completely self-sufficient. Choosing a wind turbine you will be happy living with is a bit tricky and making recommendations here is quite difficult. Sales information presented by manufacturers always seem to paint a rosy picture, when in fact, reality is more complicated.
A small, lightweight, low-cost unit may have high-tech features and claim to be the source of tremendous energy; but remember—the electrical energy from the turbine is derived from its interaction with the wind. Thin, short blades simply cannot extract as much power as longer blades with more surface area. Larger blades require a beefier unit to support more weight and torque, and will generally rotate slower requiring a more massive electrical generator.
So the slower-turning large unit can ultimately out-perform a high-r.p.m. small unit, but costs more, requires more careful installation, and needs a higher minimum wind to attain a decent output. Even though the smaller unit may begin to generate in lower wind, its electrical output may be paltry and anemic at any wind speed. Also, higher rotational speed will always produce more noise and most small units are intolerable to turbineless neighbors. Increasing the number of blades may change the pitch and level of noise, but cannot overcome the high-r.p.m. noise, and does not seem to noticeably increase electricity production.
Bottom line for wind generators: YOU must research, observe, compare and decide which compromise is right for your vessel.
Solar panels can easily provide enough power for daily needs—refrigeration, navigation lights, interior lights and instruments.
The wind generator increases the level of lifestyle to include microwaving, vacuuming, other inverter-based appliances, and loud music.
But it is all made possible by having of a lot of amp-hours of dependable, well-installed batteries.