Friday, December 23, 2011
Watts, Watts, Where to Put the Watts?
The Air-X Marine Wind Generators are smart little gizmos. Electrical power starts generating at as little as a 7 M.P.H. wind. Maximum output of 400 watts is achieved with a 28 M.P.H. wind. Braking occurs when winds approach 35 M.P.H. and complete braking occurs when winds reach 65 M.P.H. Voltage in the battery banks is continuously monitored and when the batteries are charged, the wind generators stop charging and spinning slows down. A minimum voltage of 10.5 has to be detected before charging will occur also, so it's important to not let your battery banks discharge too much. If that would happen, then alternate charging has to take place before the wind generators are functional again. So there is a voltage "window" there, or operating range, that is required for the wind generators, but staying within that "window" is easy once you learn how the generators operate. More on that later, but I want to fill you in on how we decided to transmit that generated electrical power to a source that we could use on the boat.
You can see them spinning in the picture above in this shot at sunset on the Mighty Mississippi.
My initial intent was to have both wind generators charge all of the batteries as needed. Sounds simple, right? No such luck partner. Swing Set came from the factory with five batteries, one dedicated starting battery and four house batteries. For extended life "on the hook", we knew that an inverter was going to be necessary, so more battery space needed to be found. Actually the added battery space was determined before the decision to get the wind generators was made. An "ice keeper", basically a small freezer, was positioned under the stairs to the flybridge. We never did have much use for this unit as it was AC only, and when it started to go "on the blink" it became dispensable. When I first removed the ice keeper for servicing a couple of years ago, I discovered plenty of room behind it and this is where the battery bank for the inverter, and the inverter itself, was going to be placed.
A 2900 watt Magna inverter was chosen, but there would be some limitations to our system. A bigger inverter could have been used, but an inverter can only produce power for so long, depending on how much battery storage you have in the system. We decided that four group 31 AGM batteries would fit nicely in our newly found space under the stairs to the bridge, along with the inverter. The five original batteries were also replaced by group 31 AGM batteries as well, so now we had two separate battery banks. Our simple plan to charge any battery bank with both wind generators became not so simple. To dumb down the system, as I wanted the whole thing to be as passive as possible, we decided to dedicate each wind generator to each separate battery bank.
Dave Ludwig of Bloch Marine chose two control panels to manage and monitor power to each battery bank, and these control panels, along with the control panel for the inverter was installed above or main electrical panel in the salon. The wind generator control panels consist of a switch to turn the units on and an ammeter to monitor output. Dave accomplished all of the required cutting and drilling without leaving so much as a speck of dust in our salon.
I requested that each wind generator be installed with a plug at the unit placed inside each tower, so that replacement, if necessary, would be as easy as possible. Dave was happy to be working in the heated salon to install the control panels and do most of the wiring, but when it came time to run wires up to the wind generators, the stiff 6 gauge, three wire cables, were not very co-operative in the cold February air. While the wiring for the wind generators and inverter was being installed, I was remodeling our second stateroom into a chart room/office, so I was available to assist Dave in running the cable. There was just a little cussing going on during this process, not directed at each other, thankfully.
One method of testing the units is to attach a drill to the propeller hubs and spin the generators, we opted out of this method and the March winds provided testing conditions eventually. I was on the boat shortly after the generators were hooked up and I as the wind would pick up, I could detect one of the generators shutting down, as the braking would cause a slight vibration. Dave determined that a battery isolator needed to be installed and that solved the problem. It was also my intention to have the alternators on each engine charge both battery banks when they were running and this detail got missed with all the other stuff going on. When I discovered the omission, Dave ordered the necessary equipment and had it installed in short order. The braking vibration was eliminated and except for a slight "whooshing" sound, the wind generators are fairly quiet.
We gave our power management system a very good trial over the last summer, spending as much as a week on the hook at a time. As I stated earlier, the system has limitations. One big drawback is that the inverter does not run our reverse cycle heating and air conditioning units. The inverter is big enough, but our battery bank is not for extended AC use. I installed four 12 volt Bora fans, one in each stateroom and two in the salon. If the summer heat became unbearable, we ran the Westerbeke and AC to get things cool, and then shut it down when we turned in. The electric range was also left out of the power grid for the inverter as well, along with the water heater. When under way, the starboard engine heats the water in the water heater and it stays hot for hours. We could still cook in our convection microwave and use the coffee maker with inverter power. We use a percolator coffee pot and also a french press for coffee. (The percolator coffee is better.) The propane grill was also used quite a bit to reduce usage of the diesel generator.
Swing Set now has multiple power sources; shore power, an 8KW diesel generator, the engine alternators, and two wind generators. We spent as much as five days on the hook and only ran the Westerbeke for about two hours total. When we took a trip upriver last August and ran the engines every day, we didn't use the Westerbeke at all, as the alternators along with the wind generators, quickly charged up each battery bank as we were under way. The total project cost was nearly $14,000. Keep in mind that in addition to the wind generators, we acquired an inverter and 9 new AGM batteries. Labor was the biggest expense and J.D. Schmid of Bloch Marine gave us a HUGE deduction on the hours billed, cutting the 95 charged hours nearly in half, being the time of the year and all. I hope John Bloch doesn't read this. :)
Was the expense worth it? It's hard to quantify exactly how much we can reduce the Westerbeke usage when the wind is up. On the river, with the trees, the wind is not as steady as it might be on the coast or on the ocean, so power output fluctuates. As they say, some things are priceless, and one advantage of the wind generators is that they sure are conversation starters, and the first sentence usually goes, "What do them windmills do?"