Alternative Power on a Cruising Sailboat William Oldfield ©1990 William Oldfield A cruising sailboat is the ultimate application for alternative power. There is no power utility. Fuel has usually to be carried from a gas station. Even water has to be loaded jug by jug! One approach advocated for cruising is to revert to a pre-industrial lifestyle using little electrical energy. This involves oil lamps, dried food and few instruments. Many hardy sailors can manage this approach and sail without many creature comforts. We feel safer with modern instruments and enjoy amenities like fresh food. Our sailing lifestyle can be supported by extracting the necessary power from the sun and the wind. Cruising in a Sailboat We sold our house in 1986 and sailed for Mexico. Since then, we have cruised in our 36 foot sloop, Longhope, in the Sea of Cortez and off the Mexican coast as far south as Zihuatenejo. We started like most sailboats. The main engine supplied most power, supplemented by a 600 watt generator. This was not very comfortable since running the engine makes the ship noisy and hot. Running the generator is even noisier. Now, the main engine supplies power only when we also need it for travelling in light winds, topping up the batteries and providing additional power for the water maker at the same time. The generator mainly serves as a 120 vac power source for power tools. Alternative power preserves the surroundings and provides a cooler and more peaceful living space. What follows is a semi-technical description of our electrical evolution. The photo shows Longhope at a mooring in San Carlos, Sonora. The wind generator can be seen hoisted behind the mast, above the boom. The solar panels are just visible mounted on a rack above the Bimini cover. Energy Demand and Supply The way to develop alternatives to conventional power supplies is to first understand the power consumption demands of the equipment, then find the possible sources of supply. The main consumer on Longhope is an Adler-Barbour fridge unit which we added to the 9 cubic ftoot ice box. The other major consumer is a Recovery Engineering reverse osmosis unit which makes about 1.4 gallons of fresh water an hour. The key energy requirements are shown in Table one. Since it is sunny most of the time in Mexico, the major supplier of power is the PV panels. INSERT TABLE Solar Power Our panels consist of two Arco M75 and two reconditioned Arco 16-2000 panels. One difference between a boat and a land installation is that a boat points in any direction. Because of this, we mounted the panels horizontally, causing loss of efficiency. The geographic latitude causes about 10% loss in our latitudes (the panel should be tilted south in the northern hemisphere). Because the panels do not actively follow the sun across the sky there is a further loss of efficiency. We obtain about 64% of the energy collected by an active panel if the day length is 12 hours. Despite these losses, we obtain about 62 Ampere-hours on a normal sunny day. Wind Power We bought parts for a wind generator from a longtime cruiser, Fred Turrentine of the trimaran Serape. He has supplied about half the generators used on sailboats in this area. The parts supplied to us were a used computer tape drive motor fitted with an arbor to hold the propeller, a diode and a 60 in. propeller. The design of my completed unit is shown in the illustration. The motor and propeller were fastened to a piece of broom handle using four hose clamps. They were wrapped with tape to cover the sharp edges. The fin was cut from a piece of black plexiglass. A piece of 1/8 in. nylon braid was attached near the fin, long enough to be reached from the deck to stop the generator. Two "V" arrangements were made out of 1/2 in. nylon rope with a metal thimble at the tip of each "V" to avoid chafe. One was mounted inverted above the broom handle, the other below. The "V's" were not quite symmetrical. The attachment points, the thimbles, were skewed forward to lie above and below the center of gravity of the system. The ropes were tied to the motor and the wooden rod (I spliced bowlines on the ends and the unit hung in the loop) and locked in place with plastic cable ties. The top attachment could then be clipped to the line normally used to raise the mainsail and hoisted as high up the mast as necessary for safety. The lower attachment point was fastened to three lines. Two were tied to the grab rails at each side of the cabin, the third to the end of the boom. Lengths were adjusted to pull the generator away from the mast and give it a slight downward tilt. The whole was winched tight by the main halyard. INSERT WIND MACHINE ART A two conductor 16 gauge stranded cable was used to link the generator to the ship's electrical system. The diode was mounted to a heat sink on the positive line. A switch was installed to short circuit the positive and negative leads (on the generator side of the diode of course). Shorting the system provides instant braking. In any reasonable wind, the generator should first be tilted out of the wind using the cord attached near the fin before the brake is switched. The original propeller was damaged within two weeks of buying the system. The halyard was not tight enough and the spinning propeller hit another line running down the mast. This forced me to design and build my own. I have since carved several which have been highly successful. That is, they are quiet and give at least as much power as the original. Propeller carving is fairly easy -I carved the first with a chisel on a beach in three afternoons. The wind generator makes more than 1 Amp in winds of about 10 knots or above. At 14-18 knots it generates about 10-14 Amps. One night when the winds were above 20 knots it reached 26 Amps. Under breezy conditions the wind generator can supply large amounts of power. Water Power Long trans-ocean crossings are an extreme situation. For example, a crossing to Hawaii may take as long as 30 days. The fuel supply is limited, and cannot be used to run the engine except under special conditions. The wind generator cannot be hoisted. PV power may not be adequate, particularly in overcast conditions. Fortunately, water power can fill energy needs. The boat speed averages about four knots under sail and a towed propeller can produce a steady 4 Amps, (90-100 Amp-hrs.). Supplemented by PV, this is sufficient for the instruments, lights and the refrigerator. A suitable unit has a 2 hp outboard motor propeller linked to a DC motor (such as the wind generator motor) and towed about 50 ft.behind the ship on 1/2 in. nylon braid. The propeller is mounted backwards on a 36 in. long stainless steel shaft to keep it below the water surface. Provision must be made to protect the bearings of the generator from the load of the propeller drive system and for easy disconnection of the line. Better carry a spare propeller. The unit on a friend's boat was attacked by a shark! Engine Alternator I fitted our engine with an Automac by Spa Creek. It provides a field current to the coils of the alternator which is adjusted using a solenoid to give an almost constant charging voltage. It cuts out (to the standard voltage regulator) when the voltage reaches a value preset by the user. We limit our charge rate to 30-35 Amps, at which level the alternator does not overheat. We charge to about 13.8 Volts. Portable Generator We have a 600 watt Yamaha unit. Although it works well, it has not proved too successful as a power source for us. We used to run it for four hours at a time and the noise and heat was intolerable in the confined space of the boat. Its best application was to start the main engine on the two occasions when the batteries were flat. It now mainly provides 120v power for tools. When the Yamaha is used for recharging batteries, we connect the 10 Amps/12v DC line into the batteries. The 120v is plugged into a battery charger charging the batteries at 25 Amps. The charger's circuit breaker trips after about 10 minutes if the charge rate is above 15 Amps. Cutting in and out, it takes a long time to recharge the batteries. As the batteries refill, the charge rate slows to a trickle. A smaller version of the Heliotrope HC75 battery charger recently reviewed in HP17 would make this Yamaha generator a really viable recharging option for our boat. Power Storage Battery management has been the major failure of our energy system. We have had to replace all our batteries three times. The last set, expensive sealed gel batteries, only lasted about 8 months. The best so far have been Mexican automotive batteries which give far less stored power but stand up to abuse better. Our major limitation is night travel. We need sufficient power when sailing at night for radar, instruments, running lights and the refrigerator. This requires a minimum of 130 Amp-hr of battery storage. Our design at the outset called for four model 29 batteries (ostensibly over 100 Amp- hr.) in addition to the engine starter battery. This has rarely worked properly. Our battery system always seems to be below specifications and needing replacement. The reason for our failure lies in our inability to maintain batteries, particularly when we have left Longhope in Mexico during the hot summer months. Leaving her on marina dock power for three months destroyed one set. A boat sitter who left the batteries flat for two weeks destroyed another. A set of sealed gel batteries were destroyed because I left two solar panels charging them while away for a month. (I figured five batteries, four house and the engine starter, could handle a trickle averaging only 1.5 Amps. I believe the gel cell batteries were overcharged to failure). Part of the problem lies in our poor choice of batteries, too fragile for the harsh cruising environment. The 6 Volt Trojans which were our initial choice and would have performed better, but they were too tall to fit in the available space. Six volt batteries are a problem in any case. Space forces us to have three of the batteries in one location and one in another, thus complicating the wiring of the system. Alkaline batteries would probably be perfect. Tfhey are resistant to both overcharging and heat- our two main failure problems. Unfortunately, we seem to be driven by events and install what we can get or afford at the instant our old batteries die. Since it is not practical to mix the acid and alkaline batteries, we would have to take out four good batteries and replace them all by alkalines. Our best investment would be a more sophisticated voltage regulator system allowing the batteries to be both recharged quickly and floated for extended periods, all without damage. The main difficulty stems from the different power sources we use. This regulator would either have to regulate each power source seperately, or the system as a whole. Solar power is relatively easy to regulate. PV regulation is best accomplished by series type regulators which intermittently disconnect the power source from the batteries. Regulating the wind machine is more difficult since the load cannot be disconnected during strong winds without possibly causing damage to the wind machine by overspeeding. A shunt style regulator would hold the battery voltage in line regardless of the power source. ((((See Homebrew, this issue for a schematic of just such a beast.RP)))) Last Words Our home power systems on Longhope have progressively improved. In fact, when our batteries are working we never have to start engine or generator set just for electrical power. The most successful has been the solar array. It generates power with the minimum of trouble. It is exciting to realize that solar arrays with three times the power exist now. They use gallium arsenide in addition to silicon solar cells. I hope that the current heavy use of gallium arsenide in fast integrated circuits will help to make the more efficient panels economically viable. Sailboats in Mexico could then have power to spare. Access William Oldfield, 1109 S. Carol Drive, Flagstaff, AZ 86001 ¥ 602-779- 0506.