With water flows of at least 125 liters per second (1,981 gpm), even during extended drought, and an average 1.8-meter (5.9 ft.) head, the new turbine was projected to provide at least 450 watts. Compared to the old machine, the new turbine required about 50 liters per second (800 gpm), so there was enough water to install two of the ES&D machines if need be.
It took half a day to remove the old turbine, and six people and a truck winch to drag the behemoth up the hill, where it remains lying in the long grass like a carcass. I’ve since sold its generator—a washing machine motor—for a couple hundred bucks, assuaging my need to recoup at least something from the beast.
It took just another day and a half to nut things out at the river with Paul. We built the plywood box that channels the water to the turbine and carried it down to the river, where we bolted it to the intake pipe. After making some adjustments, we slipped in the draft tube, clamped the new turbine to it, and opened the butterfly valve at the inlet. Just like that, we were up and running, and everything worked great on the first try! What a relief!
We let our new turbine run for the first summer as-is, experimenting and observing. It worked well, regularly putting out about 450 watts. The debris problem remained, but was greatly diminished. With the old turbine, sticks, stones, and leaves worked their way to the blades. These would either clog the blades, or a stone or stick might even break one. Removing the clog meant the water torture of shutting down the turbine, opening the intake, which was often below water level, reaching and contorting to get an arm down to the blades, and grabbing out the glop bit by bit—all the while kneeling chest-deep in freezing water. Not fun.
But the ES&D turbine needs only minor cleaning. The new and improved muck-out process simply involved shutting the intake butterfly valve, removing one wall of the box, and sticking a finger or two through the vanes to wipe the tiny leaves and algae off the blades—all at eye level, high and dry above the water line. The shape of the inlet vanes prevents sticks from reaching the blades. Although stones can still get drawn into the box, they drop safely to the bottom, awaiting removal the next time the access port is opened. The concern became small leaves and algae, which drape themselves over the blades, slowing the turbine and reducing power.
Through the microhydro list server, I communicated with Michael Lawley of Eco Innovation in New Zealand. He’d been having similar debris problems with his Vietnamese-made, low-head unit, which he’d solved by inventing a simple “leaf-mulcher.” Paul and I decided to adapt this great idea to our turbine.
The mulcher is a little piece of plastic with its end shaped to mirror the blade tops. It extends down below the inlet vanes about 1 millimeter (0.04 in.). Centrifugal force keeps the leaves at the outside edge of the blades, so the mulcher does not need to stick out very far. As the four blades spin, each passes by the mulcher 1,500 times a minute, which knocks or slices off the buildup. We had the mulcher in place all last summer and never once had to clean the blades! Plus, instead of reducing the turbine’s power, its output actually increased!
Now, our cue to clean the new turbine kicks into gear when the meter shows the turbine output dropping to between 10 and 11 amps (from 13 to 15 amps normally), which, in summer or winter, can occur after several weeks, or, in autumn, after several days, instead of just a few hours. One of us strolls down to the falls and turns off the intake butterfly valve to drain the chamber. Then the valve is reopened a crack to direct a high-powered water jet onto one side of the inlet vanes, which washes the leaves and algae from the blades. Once that’s finished, we open the valve fully to fill the box and restart the turbine.
With a few lights and the stereo going, our household loads vary between 100 and 150 watts, depending on whether the fridge and/or freezer are running. If we use the microwave, toaster, or electric tea jug, the load can briefly increase to 1,200 watts. With our microhydro system, these loads are no problem at all, and, within a few minutes, we’re back to dumping the excess energy from the hydro plant. Unlike off-grid homes that rely solely on small PV systems, where “phantom” loads from TVs, stereos, computers, and microwave clocks must be scrutinized, our hydro’s continuous output means that we can just ignore them.
We recently added 492 watts of rooftop PV modules to our off-grid system. It’s a cleaner, quieter backup to the microhydro system than an engine generator and has turned out to be a wonderful complement. During instances of flooding or, more rarely, when the turbine has to be shut down for maintenance, we still have enough energy to run most of our common household loads.
When the sun shines fully, the modules produce up to 450 watts. At the same time, the hydro is producing as much as 450 watts. When everything’s humming, the systems produce as much as 13 kilowatt-hours (KWH) daily! This is much more energy than we normally need, but having the two separate energy sources means that when the river is flooding or we’re doing maintenance on the hydro, or conversely when the sun’s been behind clouds for weeks, we still have plenty of energy.
With solar-made electricity, when the batteries are full, a charge controller cuts back the energy from the modules. But with microhydro, energy production does not stop—as long as water is flowing through the turbine. Switching off the electricity between the turbine and the battery will cause the turbine voltage to go too high. This scenario can create big problems, so those electrons have to go somewhere. When our batteries are full, a diversion controller shunts the excess hydro power to an air-heating resistance “dump load,” dispersing it as waste heat, and keeps the turbine electrically loaded and running at the proper rpm.
We are quite pleased with the way the systems are working. No longer slaves to our turbine, we can leave for days without worrying about food in the freezer thawing. During floods or long bouts of clouds and rain, we don’t have to hassle with a backup generator. Even in rare instances when the river is in flood and there are also several days of heavy cloud cover, we employ energy-conscious practices to make the energy stored in our battery last for two or three days.