The microhydro business is still a small, niche market. Most products, with the exception of the turbines themselves, are adapted from the solar market. The North American turbines are from microhydro pioneers such as Don Harris of Harris Hydro; Paul Cunningham of Energy Systems & Design (ESD); and Jerry Ostermeier of Alternative Power & Machine (APM). It has been nice to be able to call up and talk directly with the people who designed and built the units. When Don Harris retired, I was worried about being able to get parts and new turbines. However, Denis Ledbetter has taken over the production of the turbines and repair parts.
In 2001, Don Harris started producing his adjustable permanent-magnet generators for his hydro turbines. I switched to those and got a 40% jump in power output. I then realized that further improvements were coming from specialized manufacturers.
Today’s typical systems are much larger, and the owners are more concerned with reliability and ease of use than back in my homebrew days. Using permanent magnets eliminates the changing of brushes in alternators. Using self-cleaning intake screens (like the Coanda-type) cuts down on the time required to clean intakes. High voltage/low current (which requires smaller, and therefore less expensive, wire) is now possible with maximum power point tracking (MPPT) adapted from solar-electric systems. Specialized breakers handle the higher voltages. Sine-wave inverters run all of the AC loads without the worry of damaging sensitive electronics, which sometimes occurred with older, modified-square-wave inverters.
Some of my older systems are still 12 V and producing modest amounts of power. Other systems have gradually added more solar-electric modules to the renewable energy mix. The hydro resource is usually limited, so higher efficiency is the only way to get more power. I look at what the owner wants to accomplish and see what improvements are possible.
Many of my hydro systems I upgraded as new products became available, and as more power or better reliability was needed. All the systems are now using permanent-magnet alternators. By continuing to use the original Pelton wheels, Don Harris was able to keep the upgrade costs low.
Some of my clients switch to higher voltage with MPPT controllers to minimize the line losses associated with increased output current. Some systems extend the pipeline to increase the head, if available. The switch to self-cleaning screens cut losses caused by plugged intakes. Upgrading to a larger-diameter penstock to cut friction loss can allow more water flow.
The introduction of reasonably priced MPPT controllers for solar has opened up new design possibilities for small DC hydro systems. Before MPPT controllers were available, the hydro generator had to run at the battery voltage. That meant large wires, or accepting large voltage loss in the long-distance wires.
Now with the DC-to-DC conversions in the MPPT controllers, it is possible to operate the hydro at high voltage to keep the amperage low, minimizing line losses on long-distance wires. The MPPT units also allow the hydro turbine to run at the speed and voltage that produces the most power. Some small hydros allow varying the strength of the magnets to better match the varied flow of a stream, but the MPPT will unload the unit to let it speed up, and do the adjusting automatically.