Question of the Week
Answer: Farm hydropower projects have existed for many years, from waterwheels used for grinding grain and forging to modern hydroelectric turbines designed to run compressors and motors. Micro-hydro systems — those that produce less than 100 kilowatts of electricity — can offer a sustainable and continuous source of renewable energy on farms. It is one of the most reliable and consistent sources of renewable energy available. A good water resource with a year-round flow and several feet of elevation drop can provide years of continuous power.
Farms often have easy access to lakes and ponds as well as naturally occurring streams and rivers. When farmers possess the rights to use the water resources that are contained on-farm, they usually face fewer obstacles both in permitting and in the efficient use of farm-scale hydropower. Hydropower can be a continuous source of energy as long as enough water is flowing.
To determine the hydropower potential of the water flowing from your spring or in your stream, you must know both the flow rate of the water and the head. The flow rate is the quantity of water flowing past a point during a given period of time. The flow rates of micro-hydro systems are typically measured in gallons per minute or cubic feet per minute. The head is the vertical drop measured in feet from the headwater (in the case of a dam) or the point where the water enters the pipeline (if no dam exists) to the point where the water leaves the turbine housing. With some turbines, such as those that use a "draft tube," head extends to the base of the tube.
Micro-hydro systems generally consist of the following components:
• A trash rack, weir, and forebay to prevent debris from entering the pipeline and turbine
• A pipeline (also called a penstock) to pipe water to the turbine
• A powerhouse that contains the turbine and electronics
• A water turbine that converts the kinetic energy of the flowing water into mechanical energy that can be used directly or to drive a generator or other piece of equipment — this is the main component of a micro-hydro system
• A tailrace to release the water back into the source it came from
• Transmission lines to deliver electrical power where it is needed
The environmental impact of micro-hydro systems is usually small but by no means absent altogether. When water is diverted or dammed, or when structures installed in the stream channel interfere with the natural flow of the water, there is an environmental impact. However, compared to large hydropower dams, micro-hydro systems have a smaller footprint and generally lower environmental impacts. Even so, there are several local, state, and federal agencies that may want environmental impacts to be assessed for a micro-hydro project.
Obtaining the necessary permits from local, state, and federal agencies is a key part of any micro-hydro project. Although the permitting process may appear burdensome, it is intended to protect the water resource and its users, including the fish, plants, and animal communities that also use the water. It is best to identify all the necessary permits and approvals to develop a hydro resource very early on in the process. Doing so will help you avoid wasting time in planning your micro-hydro project.
Any analysis of the economics of a micro-hydro system should include both the initial investment costs and the operation and maintenance costs. The initial investment cost calculation must include not only the turbine and generator, but also other variable expenses such as any pipes, power lines, buildings, dam construction, civil engineering work, permits, and legal work. One characteristic of many micro-hydro systems is that the up-front costs can be high, although the up-front and operating costs may be very competitive with generators, wind-electric systems, and solar-electric systems, as well as with conventional energy sources. Except for small maintenance costs, a micro-hydro system should provide "free" energy for 20 to 25 years or longer.
For more information on micro-hydro, review the ATTRA publications Micro-Hydro Power: Is It Right for My Farm? and Micro-Hydro Power: A Beginners Guide to Design and Installation. Other ATTRA publications you may find useful include Renewable Energy Opportunities on the Farm and Measuring and Conserving Irrigation Water.
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