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Microhydro Systems: Advice From The Pros: Page 5 of 6
Issue Date:
December / January 2012
Beginner
- Beginner
Q: What are common challenges encountered in installation?
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:
- Intake site selection and installation
- Proper pipe selection and installation, including dealing with poor access and long distances
- Routing pipeline or power line over rough or steep terrain
- Avoiding private land, public land, or road crossings
- Air blockage in pipes laid with an uphill slant
- Proper transmission cable selection, installation, and protection
- Inaccurate measurements of head, flow, and distances
- Protection of penstock from sun, slides, and other physical damage
- Permitting and regulatory issues
- Freezing conditions (i.e., ice plugging screens and low water levels)
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.
Q: Have there been any notable advances in turbine, control, or system design strategies in recent years?
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.
Comments (2)
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For remote sites where the owner has access to enough water to generate 1+ KW; it may be advisable to install microhydro should the distance to the nearest power line be 2 or more poles away. In Maine, a pole typically costs about $9,000.
On the other hand going off the grid is not for the faint hearted.
Don't dismiss the water wheel so quickly. A large slowly turning water wheel can provide enough torque to power a transmission so that a 300:1 or greater increase in RPM can be obtained. A large wheel with a small amount of water may do the same. Depends on whether it is in the current or powered by the weight of falling water.
There are also large volumes of water impounded in tidal pounds that can power a modern equivalent of the Roman tub turbine. In Maine we have 11' tides and there is an infrastructure of tidal ponds which ran approx. 2,000 tidal water mills.
OREC and others now use variations of the Gorlov turbine in swift underwater ocean currents. Tidal barrages using compression waves can also drive large turbines, i.e. SEABELL of Tokyo.