Each site has its own challenges, but most are overcome by the use of common sense and some basic engineering skills. Steep, wooded terrain and rocky stream courses can make installation more difficult.
Specific challenges include:
Another significant challenge in microhydro installation is finding local, experienced installers. Many more people install solar-electric systems and some also install wind-electric systems with some level of expertise, but microhydro is the most obscure of the renewable technologies.
There have been only a few major advances. Some improvements have been made by tweaking original designs, such as adjustable guide vanes on certain low-head, propeller turbines and adjustable permanent-magnet alternators.
Modern electronic load controllers have freed us from the need for the elaborate and delicate mechanical speed-governing systems used in the past. Inexpensive permanent magnets now allow manufacturers to offer very efficient, simple battery-charging alternators. The use of induction motors as generators has reduced the cost of basic AC hydro systems.
Hydropower systems continue to become more efficient and reliable, but most hydro systems are based on fundamental principles that have been proven for more than 100 years. New on the scene is the ability to maximum power point track (MPPT) a hydro turbine, which can solve some of the mid-range transmission issues mostly for 12- or 24-volt systems. MPPT controllers allow a hydro turbine to run above battery voltage, allowing longer wire runs and more efficient output—both in the operation of the turbine and in the line losses. And rather than having to manually adjust some alternators’ magnetic field as battery voltage and flows fluctuate, a MPPT controller can do it electronically.
Grid-tied equipment is gradually moving into the microhydro world, increasing the opportunities to sell energy to local utilities. “Bleeding edge” technology has experimenters using PV arrays as part of hydro control strategies (using the array as a zener diode) in both battery-based and batteryless systems.