Water Turbine Basics
Water turbines generate very reliable power with a very simple design. Some kind of "runner" or propeller is attached to a shaft that operates an alternator to generate power when water turns the runner. There are quite a few types of turbines, but they fall into three major styles: impulse turbines, reaction turbines and submersible propeller turbines. Each is ideally suited for a different type of water supply. No matter what source of running water you have on your property, if it supplies a year-round flow of water, there is most likely a water turbine well-suited to provide electricity for you.

Water turbines, like wind turbines, are "active power producers". When the water is flowing and the turbine runner is spinning, the turbine is producing electrical power. That power must be used -- for charging batteries, operating electrical equipment, etc. -- or it can dissipate as heat inside the water turbine, causing damage. Most water power systems have a "load diverting" charge controller which allows for full use of this power. The controller allows needed power to flow to electrical equipment, prevents overcharging of the battery, and diverts any excess power to to a "diversion load" that safely uses the surplus electricity.

Some load diverting controllers work off a simple voltage-regulated shunting system. They are installed between the turbine and the battery bank, and when the battery voltage reaches the high set point, the controller shunts 100% of the turbine's output to a diversion load (usually either a simple heat-sink resistor, or some non-essential electrical appliance). When the battery voltage drops below the low set point, the controller shunts the power back to the batteries until it reaches the high point again.

Other controllers, known as "proportional" controllers, can be installed either inline between the battery and turbine, or "off-line" between the battery and diversion load. These controllers regulate the electrical flow so that -- when the batteries and electrical loads cannot use all the power being produced -- only the surplus energy is transferred to the diversion load.
Once a load-diverting charge controller is installed for the turbine, and the turbine is operational, your electrical system can be connected to the batteries, either directly for a matching-voltage DC system, or through an inverter for an AC or mixed AC/DC system.

Different Styles of Water Turbine
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Impulse Style Water Turbines- An impulse turbine operates on the same principle as a toy pinwheel. Water strikes the turbine runner, and pushes it in a circle. The water is delivered to the runner through a pipeline, and out a small nozzle which maximizes the force available to operate the turbine.

These types of water generator work best in sites where the water source has high head (20 feet or more). Head is the vertical distance between where the water enters the turbine system (in this case, into a pipeline) and where it reaches the turbine runner.

Small impulse water turbines require minimal water flow volume, so they are ideal for sites where a relatively small amount of water runs down a fairly steep hill, as in a hill-side stream or small waterfall. The most well-known type of impulse turbine is the Pelton-wheel style as used in Harris Pelton turbines. But in higher flow sites, a Turgo style runner such as the one use in the Stream Engine has a higher output potential.

Reaction Style Water Turbines- Reaction turbines require a much larger amount of water flow than impulse styles, but can operate with as little as two feet of head, making them ideal for sites where there may be relatively flat land, but a large water flow. They use either a 'traditional' reaction style runner like the Neptune or Nautilus, or a propeller runner like the PowerPal and Niade.

With reaction turbines, the water is routed either through a pipeline into an enclosed housing like the Nautilus model, or through a canal to an open flume like the Niade, PowerPal and Neptune models (note: most open-flume designs can be modified to use a pipeline and enclosed housing if it better suits your installation site). The turbine runner is immersed in the water, which exits the housing through the turbine, turning the alternator as it 'drops' through the runner blades. No matter which runner style a reaction turbine uses, a specially designed outlet tube increases the turbine power output by creating suction as the water exits the system.

Submersible Propeller Water Turbines- These turbines are the least efficient of the three styles, but also the simplest design. A propeller mounted on the front of the turbine is attached to an alternator inside the main turbine housing. When submerged in a fast moving water source, the propeller is rotated by the force of the passing water.

Propeller style generators work well for locations with a fast moving, relatively deep stream or river, where a water diversion system is not possible, or when mounted on a moving boat. The AQUW submersible propeller turbine was originally design for marine use, but can be easily installed in a fast moving river or large stream.

Customizing Water Turbine Power Output

Water turbines come in a range of output voltages, to match the overall voltage of your electrical system. While 12 volt is common for small to mid-sized systems, large systems can be designed in 24 or 48 volt configurations. For marine use, most boats will have a 12 volt system.

For impulse-style turbine systems, power output can be increased in high-flow sites by using multiple nozzles on the runner enclosure and/or using a larger diameter runner. Many reaction style turbine models also come with the option for two or more runner diameters, with the larger option providing more power for higher flow sites.

In sites with sufficient water flow volume, multiple turbines of any style, or a mix of different styles in some cases, can be assembled into a single high-output system.

Using Water Turbines in Alaska
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If you have a steady year-round source of running water near your remote cabin or home, water generators can provide the most constant and reliable alternative power source. However, special precautions need to be taken to protect the turbine during winter freeze-up and spring break-up, and some measure must be taken to keep the system from freezing during winter.

For impulse and reaction turbines, one option is to install a heating system in the water intake, turbine housing and outlet routes, and attach that as the turbine's diversion load. Of course, you would need to make sure the turbine produced enough excess power during the winter to keep the heating system functioning at almost all times. If not, you would have to find an alternate diversion load and attach the heating system as a regular winter load running directly off your battery bank. But any heat-tape and/or heating element system that effectively keeps regular above-ground water pipes and cisterns from freezing would likely work well to keep your water turbine running smoothly.

In order to protect a propeller generator and its mounting assembly, the entire assembly should be removed from a river when the first signs of surface-freezing appear. After the ice layer over the river has formed completely, a hole can be cut in the ice to accommodate the re-installation of the generator and mounting assembly. In spring, the generator should be removed from the river when break-up begins, and can be re-installed once the surface ice has disintegrated to the point of not posing a structural threat to the assembly.

Taking these precautions will result in losing a couple months' use of the water turbine each year, but will prove invaluable in maximizing the generator's useful lifespan.

In marine use, a propeller turbine should be mounted on a hinged pole assembly that allows it to be locked down when in use, and swung up out of the water if the boat is moving through dangerous waters. In most cases a boat mounted turbine shouldn't be a major concern, as the boat will likely be piloted in areas with plenty of underwater clearance. However, the generator mount should extend deeper than the main portion of the boat's hull, so if any significant sub-surface debris is likely to come within a couple feet of the hull bottom, it may be wisest to temporarily pull the turbine out of the water.

Benefits of Micro-hydro Energy

Unlike the seasonal fluctuations of solar and wind energy, micro-hydro power can provide constant year-round electricity for boats or remote locations lucky enough to have constant running water. Like most alternative energy sources, microhydro power is emission-free and very low-impact on the environment.

In marine use, a propeller generator will provide constant power anytime the boat is in motion, and even at anchor in a significant current. Microhydro generators are an ideal marine power source.

For commercial and industrial use, a micro-hydro generator could be used to power river signal buoys, or any riverside installations, as well as commercial marine applications.