FAQ

Micro-Hydro

With an off grid system what happens when my batteries are charged and I don’t need any more energy?

Once the batteries are charged a controller sends the energy to what is known as a diversion load, also known as a dump load. This is usually a water or air heater. Such a diversion load is sized to handle the full peak production capacity of the turbine.

Why do I need a water license?

Water is a limited resource and in BC is owned by the crown. The authority to divert and use surface water is obtained by a license. The Water Stewardship program is a means of protecting the water and facilitating a sharing process for this limited resource while continuing to meet the need ecosystem which it supports.

For information on the water stewardship division please check out their website.

Here is a link to Water License Application Forms

How much of the flow in the creek can I use in my micro hydro system?

The short answer is not all of it, the correct answer comes from a specialist which will look at the factors such as whether or not the creek is fish bearing and calculate what the minimum in stream release will need to be in order to sustain the natural eco-system within the creek. This number is often expressed as a percentage of the mean annual discharge (% MAD).

How do I figure out how much power I can generate from my creek?

The micro hydro power equation:

Power [kW] = Flow (l/s) * Head (m) * Constant * Efficiency

The constant is the specific density of water (1000 kg/m^3) times the gravitational constant (9.81 m/s) all divided by 1000 which is 9.810 (many people in the trade round this number up to 10 which in end doesn't through of your numbers)

Efficiency of the system is commonly assumed to be approximately 50% until designed. This may seem low however this is the efficiency of the penstock, turbine, generator and balance of system.

Example:

Power [kW] = Flow (l/s) * Head (m) * Constant * Efficiency

2.5 l/s * 30 m * 10 * 50% = 375 Watts

How much head do I need for a micro-hydro system?

The more the better, due to the relationship of flow and head more head is always better. Typically micro hydro systems have head anywhere 3 - 300 meters. Please read the power question and answer for more information.

How much flow do I need to generate my own power?

Micro hydro systems need flow and head in order to generate power. If you have very little head you need a very large flow and inversely if you have lots of head you don't need a very large flow. So there is no simple answer to that question, please see the power question.

With a grid tied system, what happens if I am producing more electricity than I am using?

With a grid tied power system any energy produced that you don't use is sold to BC Hydro through an agreement know as the Net Metering. BC Hydro will credit you for electricity that you provide to their system and if you have a large system or use very little energy you could be net zero. Net zero means over the course of the year you produce all of the energy you need.

With a grid tied system, what happens when the power goes out?

On a basic grid tied power system the inverter is dependent on the grid.  You would be without power if the grid signal is lost. If you invest in a battery backup system, when the grid goes offline you will be the only house in your neighbourhood with electricity!

What is “BALANCE OF SYSTEMS”?

Balance of systems is the components which complete the system. Photovoltaic modules are the means of collecting the suns energy, however in order to use the electricity in our houses we need to condition it into AC (alternating current) so that it is compatible with our appliances. There also needs to be components for safety. Balance of systems typically includes combiner boxes, breakers, disconnects, inverters and batteries when off grid.

What is “GRID TIED”?

When a power system is "grid tied" it is connected to the utility provider such as BC Hydro. By connecting to the grid you do not need batteries to provide peak loads and you can sell excess electricity to BC Hydro through the net metering program. Batteries can still be part of the system if you wish to have a backup system.

How big of a power system do I need?

That depends on your goals and if you are connected to the grid or not.

Grid tied systems can be as large as you want. Often budget or emission offsets are influencing factors in the final decision.

Off grid systems are sized based on a load calculation which comes down to a balance of lifestyle and budget.

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