Energy - Flowing water possesses energy. The amount of energy it has is based on two factors -HEAD and FLOW. You need to have both to generate energy from a water source. Flow is the amount of water, usually expressed in gallons per minute or liters per second. Head is the pressure of the water, usually expressed in pounds per square inch (PSI) or in feet of elevation drop (feet of head). The more flow and head and you have, the more energy you can produce. RockyHydro's calculator can calculate the amount of energy you have based on your head and flow, or for a quick estimate you can do: Flow (Gallons per minute) X Head (feet of elevation drop) / 10 = watts. See our Getting Started page to learn about measuring the head and flow.
Because some head (or elevation drop) is required, most systems will use a pipe to carry the water down from the source to the generator. This pipe is called a penstock in the micro-hydro world. The penstock needs to be large enough to handle the available flow. We can calculate how large of a pipe you'll need to minimize any friction in the pipe, which will suck energy from your system. PVC pipe is cheap, can be bought from any hardware store, is super easy to work with, and works great as a penstock.
Some LOW HEAD SYSTEMS may simply use a diversion trench, a small waterfall, or a small dam to create the head, and then the water will flow directly through the turbine and back into the stream below.
Converting the Energy - The device used to capture the energy of the flowing water is the turbine. There are many different types of turbines, but they can be broken down into two different groups - impulse and reaction.
Impulse turbines such as a pelton wheel or a turgo work best when there is a relatively small amount of flow but a relatively large amount of head. The high pressure water stream hits the turbine paddle or spoon, forcing it to turn. The spoons of a turgo and pelton turbine are curved, so the water doesn't just hit a paddle and fall away, the water actually does a 180 degree turn. The extra force of causing the water to completely change directions makes the turbine spin even faster.
Reaction Turbines are best suited in low head, high flow situations. Impellers and propellers are both reaction turbines. They better capture the energy of the water when there is not enough head to create a high pressure water jet. RockyHydro's Low Head systems use reaction turbines.
The turbine is attached to a generator, which converts the energy of the spinning turbine into electricity. There are many types of generators, but they all work using magnets. As the turbine spins the generator shaft, it causes magnets to spin inside the generator. The magnets spin around coils of wire. The motion of the magnets causes the electrons in the nearby wire to move back and forth or around; and moving electrons is electricity!
All RockyHydro systems uses permanent magnet alternators, also known as three phase brushless motors. This style of generator is extremely reliable because they have no brushes to burn out. By using permanent magnets instead of electro-magnets (like in a car alternator) the generator is extremely efficient. Our generators are "three phase" which means they have three wires coming out of them, and the electricity flows back and forth thru the three wires to each other. A special rectifier circuit takes all of this movement and directs it in all one direction; it changes the three wires with alternating current to two wires with direct curent. The two wires will then charge a battery or power an inverter.
The three phase generator is extremely efficient, which is why RockyHydro has chosen to use it in all of their systems. Three phase AC power also travels very well, so if the generator is a long way away from the cabin or whatever you are powering, smaller wires can be used with a minimal loss of power due to line friction. We have a wire loss calculator available to calculate the wire size you'll need for your system.
Most systems will need a water intake, which collects the water before it flows into the penstock. There are many simple self cleaning designs, as pictured.
In a high-head system, the water will flow from the penstock to a nozzle. The nozzle restricts the size of the water flow, creating a high power water jet. The nozzle size should be just big enough to handle the amount of water flow. The nozzle can be as simple as a small PVC pipe with a cap on it that has a hole drilled in it, but we also have finished brass nozzles suppliers that we can forward you to.
The motor will sit on a housing, with the turgo turbine inside. The housing can be as simple as a plywood box protected with a coat of epoxy. As part of our information package we offer an instruction manual on building a alluminum or plywood housing.
From the motor will come wires that can travel a long distance or a short distance to the above mentioned rectifier. From the rectifier will come 2 wires that will go to a charge controller. A charge controller makes sure that batteries are not being over-charged. A more advanced charge controller called a diversion load controller may be needed with some systems. If the batteries are all charged up, the diversion charge controller then sends the electricity to another source such as a heater element. This keeps the generator working hard and actually doing something. If the charge controller simply stops the flow of electricity instead of diverting it, the generator RPM will increase and you'll run the risk of burning it out. It is kind of like taking a race car and putting it on jacks, then gunning the throttle. Since the car isn't going anywhere there is no resistance on the motor and the RPM will go too high and burn out your engine. So because some larger systems require a diversion charge controller, Rocky Hydro has a list of suppliers available so you can purchase them without a middle man.
The charge controller will then be hooked up to a battery. The battery stores the energy created by the micro-hydro systems for use later. It also allows the use of devices that use more energy than what is being generated. For example, if you stream is producing 400 watts, but you want to fire up the 1200 watt microwave, you can let the battery store up the energy for 3 minutes, and then run the microwave for one minute.
From the battery an inverter will usually be connected next. This converts the 12 volt DC power that the battery stores to the higher voltage AC power that comes out of your home outlets. This lets you use your system with all your normal appliances.
There are also "grid-tie" inverters available. These inverters connect to the normal grid power from your utility company and sell the power back to the power company! Your power bill may be reduced, or in some areas the power company may start paying you money! These systems are usually more spendy, but you can find some some cheaper smaller grid tie inverters but they are not UL listed.
You're now ready to get started! If you know your head, flow, and penstock length, we would love to help you put together a system. For the $50 fee you will recieve-
A Micro-Hydro Calculator - used to calculate:
Power or watts your stream can produce
Necessary pipe diameter for your penstock (based on Hazen-Williams pipe-friction formulas)
Amount of money you'll save by generating your own electricity
Number and size of nozzles
Nozzle angle and placement
Supplier Lists - For direct purchasing of generators, turbines, rectifiers, charge controllers, and inverters. We'll you provide you with their websites, and other contact info so you can make all your purchases without a middle man!
Personal contact information - With this you can provide us with your head or elevation drop, flow, and pipe length. We'll provide you with unbiased, honest information about which generator and turbine would work the best, and give you a recommendation on pipe size so you can get the most power out of your site!
A Downloadable Contruction Manual - Concerning how to put your complete system together, from the penstock to the generator and turbines with charge controllers and inverters.
Before you make the purchase - here's a little tip: (Elevation drop in feet) X (Flow in GPM) / 10 = Watts you can produce. Run this quick calculation to see if you'll get enough power to make it all worth it.