Home-scale hydroelectric power systems offer an opportunity for humans to forge an intelligent and sustainable partnership with sunshine, rain and running water. Sometimes dubbed “microhydro,” this approach uses low-impact mechanical systems to harness moving water to generate clean, reliable electric power. Unlike the intermittent power from wind or solar systems, hydroelectric power can flow night and day from year-round streams.

A hydroelectric system converts the force from flowing water into electricity. You take the kinetic energy of water flowing downhill from a stream or river and direct it onto a wheel in a turbine that converts the rotational energy to electricity. The amount of power produced depends on the volume of water flowing onto the turbine and the vertical distance it falls through the system. Equipment costs range from about $1,000 for the smallest, to $20,000 for a system large enough to power several modern homes.

“Many microhydro systems generate 75 to 350 kilowatt hours (kWh) per month,” Scott Davis explains in his book, Microhydro: Clean Power from Water, a new title in the MOTHER EARTH NEWS “Books for Wiser Living” series. Davis is a renewable energy developer with decades of microhydro experience. In fact, it’s his life’s work, and he’s gathered all his knowledge, experience and enthusiasm into this concise, easy-to-understand manual. His book covers the entire subject, from the essentials of site selection to the nitty-gritty of hardware choices and installation.

To implement a successful microhydro system, you will need the following basic

requirements:

At least 2 gallons per minute of flowing water, and a lot of drop; or 2 feet of drop and 500 gallons per minute of water flow.

A proper turbine, alternator and shelter from bad weather.

Permission from the relevant authorities, even if the project is entirely on your own land.

A water intake and enough pipeline or “penstock” to divert water to the turbine and return it to the stream.

A transmission line to move the power from the alternator to the point of use.

Batteries and a power inverter subsystem to convert the electricity to an alternating current (AC), and a controller for the electrical system.

Site Assessment

If you’re lucky enough to have an abundance of flowing water, you may be tempted to envision projects that are larger than what is normally required.avis stresses that you should plan to produce only the power you need, not the maximum amount possible. If you don’t have an obvious microhydro location — but you still have access to running water — you still may be able to set up a system.

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In its simplest form, the energy potential of flowing water depends on its flow rate (usually measured in gallons per minute) multiplied by the pressure behind that flow (related to the overall distance of water drop, called “head” in the business).avis recommends a multistep approach to assess your microhydro potential before buying any equipment. Accurate site assessment is key because it identifies the total energy potential that’s available, and it all begins with a measurement of water-volume flow rates.

“Most microhydro systems use between 2 and 1,000 gallons of water per minute,” Davis says. “If you have a spring or very small creek, the amount of available water may be the factor that limits your power output.”

One of the ways to find the total amount of available water, Davis says, is to use the “container method.” Find a spot where the potential stream’s water enters a culvert and time how long it takes to fill up a container of a known size. The stream’s flow in gallons per minute equals the size of the container in gallons divided by the time it takes to fill in seconds, times 60. For example, if a 5-gallon bucket fills up in 10 seconds, the stream flows at 30 gallons per minute (gpm).

Next, you need information on the pressure behind that flow, which relates to the amount of vertical drop the water undergoes as it travels through your site. Pressure measurement combines with flow rate to determine the raw energy potential of a location. In turn, this defines the universe of choices for the hardware necessary to produce the electricity you need at wall sockets, light fixtures and appliances. Flow rate multiplied by pressure equals power.

You won’t get very far in the microhydro adventure before you realize something important: There’s more to a good system than just flowing water. You also are dealing with terrestrial conditions, and that’s why creating a stream profile is essential and should be the third factor to consider when choosing your optimum site.

“A completed stream profile sounds something like this,” Davis says. “The first 100 feet drops 20 feet. The second 100 feet are not as steep, and drops 16 feet, and so on.” What you’re aiming for is an accurate representation of the water flow over natural landforms, and how those characteristics can be used to good advantage in your plans. By using a surveyor’s transit, a water level or a laser level, you can produce a side-view profile — or cross-section — of the entire stream landscape as water runs from pipeline intake to output port.

A stream profile also helps you determine the best location for the water-intake end of the pipe. This is where most of your regular maintenance will happen (cleaning out brush and stream debris, for instance), so you need to choose a spot with easy access, if possible. Also, if the flow rate of your stream is more than a few gallons per minute, you may find several possible locations for the turbine itself. The stream profile often makes it easier to identify optimal turbine placement, which usually consists of a stable water level, accessibility and water relatively free from debris. Another important consideration is to place the turbine in an area where it won’t be affected by freezing water.

Most microhydro installations include a pipeline that diverts water over land down from an area of high elevation, connecting to an enclosed water wheel (that’s the turbine) at some lower level. This situation raises key questions: Will a 2-inch-diameter pipe give you the best energy potential in relation to the cost of the material and its flow rate? How does this compare with a 4-inch pipe? Will your energy expectations be met with a 500-foot pipeline, or do you need a 1,000-foot pipe to get more head (water pressure)? How will flow volume, vertical drop and friction in the pipe affect the amount of power generated? All these questions are important because they each can have a tremendous effect on power output.

Davis cites one case study where variations in pipe size, flow rate and static head yielded a 350-percent output difference across the four options examined.

The Hardware

Most people who choose hydropower are attracted to the fascinating variety of unusual hardware that makes clean, low-cost electricity.

Turbines complete the first part of the energy-conversion process, and in many ways, they’re the heart of any hydropower system. Many designs are available, but most include some kind of fanlike wheel on a shaft — set within a metal case — that contains and directs water flow to spin the blades. Turbines are designed for both low- and high-pressure applications.

High-head impulse turbines are the most versatile — used for situations with heads ranging from 6 to 600 feet — and can generate enough power to sustain most any requirement given the right conditions. The Turgo impulse turbine uses a jet of water to strike the enclosed water wheel at an angle. Because the impulse turbine uses more water, significant power can be generated with less head, which may result in shorter penstocks. The Pelton impulse turbine sends a jet of water to strike the enclosed water wheel along its circumference, which can be slightly more efficient than the Turgo turbine, Davis says, and is used especially for low-flow, high-head situations.

Low-head turbines are meant for heads under 10 or 12 feet. These turbines are ideal candidates to charge batteries a long way from the powerhouse at low expense. The LH-1000 — made by Energy Systems and Design — will produce power from as little as 2 feet of head, and the Powerpal — made by Asian Phoenix Resources — is a complete small-scale AC system.

Constructing your own microhydro system also can be a viable option. Many different methods can be good alternatives to purchasing commercially produced turbines and alternators, but the efficiency and effectiveness of a homemade system depends much on its design. A centrifugal pump can be made into a backward-running Francis turbine (in which water flows through the turbine runner); an induction motor can be used as an alternator; and a crossflow turbine can be fabricated with readily available materials common to Third World situations, Davis says.

The electrical side of any hydropower facility always includes a device to convert the mechanical energy of a spinning shaft into electrical energy (either a generator for direct current or an alternator for AC). That electrical energy is then sent through a series of components called the “balance of system” equipment, which saves and regulates the electricity once it’s generated. But before you tackle the electrical side of hydropower, you need to understand something about the two basic types of electricity: direct current (DC) and AC.

DC is the sort of electricity delivered by a battery. Imagine a whole bunch of electrons piled up against one pole of a battery, desperately trying to get to the other pole. When you close the circuit across both poles, energy flows in one direction and can spin a motor or light a bulb in the process.C electricity is more complicated to generate than AC, and it travels less efficiently. That said, you can store DC power in a battery, and that makes it more useful for small hydropower applications that need to build up a stockpile of energy to meet large intermittent loads.

AC is the type you get from the grid; just think about it as a series of rising and falling voltage waves. In a typical grid-delivered power system, this rise-and-fall cycle happens 60 times a second. Most appliances are designed to run on AC power only.

Smaller hydropower systems might include a series of deep-cycle batteries for storing DC energy for intermittent high demand, though having a DC foundation to your system doesn’t necessarily rule out the option of AC output, as well. The secret is something called an inverter. “These convert direct-current battery power (DC) into the kind of alternating current (AC) that we’re all familiar with,” Davis says.

If your energy needs are medium to high, you should consider a microhydro system that generates AC power with an alternator right from the start. At that level, you’re nearing the point where electrical space heating can be part of your plans. “A 10-kilowatt system that runs in the winter,” Davis says, “can provide heat that is the equivalent of burning 12 cords of firewood in a six-month heating season.”

To understand how a microhydro setup operates in real life, it’s often useful to look at examples. At the smaller end of the microhydro spectrum, a remote homestead in British Columbia wanted to produce enough electricity to run lights, radio, radiophone and stereo with an existing 1 1/4-inch domestic water supply pipe. The residents had doubts they would still have enough water to run their showers and toilets after the conversion, given the water’s static pressure only amounted to 65 pounds per square inch (psi). They installed a Harris hydroelectric turbine with a Ford alternator close to the house that produces a modest output of 50 kWh per month. They chose a 500-watt inverter as the electrical subsystem. This system provides for the homestead’s lights, radio and stereo, but propane provides other vital home services such as refrigeration and cooking.

And at the larger end of the microhydro spectrum, a remote First Nations American Indian community in British Columbia needed a high-output system, but the area’s geography challenged the development of a microhydro system. Using an excavator, Davis and his crew dug a usable trench and laid a 4-inch-diameter pipeline, traveling over 900 feet and delivering 350 gpm over 315 feet of vertical head. This hydroelectric system generates a whopping 7,200 kWh per month at a continuous output of 10,000 watts using an 8-inch Pelton turbine wheel, directly driving a brushless 12-kilowatt alternator.

Microhydro is a clean, sustainable source of power for homesteads in the right location. By considering some of the preceeding requirements, you’ll know if it can be a possibility for you. If it is, Davis’ book and other resources will give you a more thorough look at the systems and companies on the market, plus a sound foundation for further development.

Steve Maxwell lives and gardens with his wife and four children on Mount Island, Ontario.