BACKYARD HOMESTEAD UTILITY

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As the engine stands now, it produces more than enough power at optimal generator speed—which is 1,800 RPM—to do its job effectively. As near as we can figure, the stout little fourbanger, originally rated at 110 HP at 3,800 RPM, kicks out nearly 70 "ponies" on its woodgas diet at that speed . . . which translates to a supply of about 30 usable horsepower to the alternator at 1,800 revolutions per minute (and that also happens to be the speed at which the powerplant develops its maximum torque). Furthermore, these circumstances allow us to utilize a cost-saving direct-drive coupling, rather than a more complicated and power-sapping step-down transmission system for the setup.

The generating unit itself is a standard Kamag 14 self-exciting alternator with a 10-KW continuous rating. It provides either one 240volt or two 120-volt 60-cycle circuits, and is designed to cut in at 210 volts so the plant can come up to operational speed without the burden of a load. By the same token, it incorporates an overspeed governor that cuts the unit out at a voltage of 270.

Because changing load demands directly affect the rotational speed of the engine/alternator setup, and thereby influence power cycling, we had to rely on a speed control to maintain 60 cycles consistently. But rather than use the variable-width pulley arrangement that originally came with the generator, we utilized its speed sensor and servomotor only, then connected the latter component directly to the engine throttle. This layout is far less cumbersome and complicated than the "pulley pincher", though we'll need to do a good deal more testing—and possibly make some modifications—before we can fully vouch for its effectiveness.

COGENERATION PROVIDES HEAT

In addition to producing electricity for our maintenance shop, the system has also been designed to provide that structure with heat. Believe it or not, only about one-third of the energy in a given fuel does any useful work as it's burned in an engine . . . the rest is generally wasted—in the form of heat—as it's dumped out the exhaust pipe or drawn from the radiator. So, to take advantage of this squandered resource, we routed the powerplant's cooling system—along with the "jacket" that surrounds its ex haust manifold—into a 15-gallon "closed loop" . . . which in turn dumps its thermal energy into a 500-gallon storage tank that's connected, through a pump and 1-1/2" line, to a second container of equal volume.

For our summertime demonstrations, we've plumbed a small hot-water space heater into the primary loop from the engine. However, come fall we plan to expand this into a fullscale hydronic system, by installing baseboard heaters in the 1,200-square-foot structure . . . which should make full use of the 170°F water that the engine provides.

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