When we think hydroelectric, we usually envisage a large reservoir, dammed by artificial means, driving large megawatt turbines, spinning endlessly in order to light our civilization.
This is true for the majority of the green energy produced in North America.
Now if you want to produce your own power, and if you are fortunate enough to own property with a good spring or a small stream, and there is enough change in elevation, a small micro water turbine may be just the ticket.
Water turbines have the distinct advantage of producing current 24/7, and in the world of off-grid, 24/7 is great.
They do have some disadvantages:
• The penstock (feed piping) has to be set up in such a way as to allow the inlet to be screened. This is to prevent debris floating in the water from plugging off the intake.
• The inlet has to be lower than the ice level that develops in winter and the whole system has to be protected from frost. Here in Alberta, frost is a big concern and must be planned for, from reservoir to powerhouse.
Micro turbines are by definition, less than 22.5 kW in size and come in a large assortment of designs.
Generally, turbines are divided into two classes, reaction and impulse. The reaction turbine is the most common type in use today and is generally found in hydro stations. Reaction turbine types, such as the Kaplan, Straflo and water wheel, are designed for lower head pressures, variable flows and provide efficiencies in the 90 per cent range.
The impulse turbine, such as the Pelton wheel, cross flow or Turgo, utilizes a nozzle that directs a stream of water at buckets, or fins mounted on a common shaft. They are designed for high head pressures, higher flow rates and have efficiencies in the 90 to 92 per cent range.
The electrical power units these turbines drive can either be alternating or AC current or direct or DC current. AC or DC voltage is determined by the distance the power has to be transported and the type of electrical equipment it is providing the power for.
The size of the turbine is determined by budget and electrical requirements, and kinetic energy provided by the water source. A small energy efficient home with two semi retired people requires a lot less power than a remote fishing lodge.
The physical properties of the water flow, elevation change from inlet of penstock to outlet at turbine, determine which class of turbine will be the most suitable for the site.
In any event, a micro hydro system can be sized and designed for the application and budget of the end user.
With the cost of diesel fuel rising, micro hydro can go a long way to providing the power needed for the remote home or lodge site, especially if supplemented by solar or wind.
That is of course, if water and local topography work for the particular off-grid situation.
Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003.