Microhydro FAQ |
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If your basic questions are not answered here, please send us e-mail and tell us what's missing, superfluous or unclear. Thanks! First... use this web page which presents a bit of information - still far from complete - about microhydro. Second... fill out our secure CLIENT INFORMATION FORM for microhydro systems. This gives us some basic information to begin to address your situation and serve you with much more personal follow-up. We appreciate your understanding and assistance with this. |
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What is meant by "micro" hydro power? |
When most people think of hydroelectric power, images of enormous dams, turbines, Niagara Falls, Hydro Quebec, and perhaps salmon problems in the Northwest come to mind. These installations are, in every sense, large energy development projects which have substantial environmental and social impacts. On the contrary, the term microhydro is meant to distinguish very small-scale, point-of-use hydro power from these industrial scale, centralized power generation projects. Analogous to wind, there are also mid-scale hydro installations with typical outputs of 1 megawatt (MW) power or less, which cause far less environmental disturbance. Like microhydro, mid-scale hydro projects are usually designed to be point-of-use rather than centralized power generation facilities. A fine example of mid-scale hydro is the facility which provides power to WJFF 90.5 FM in Jeffersonville NY. Typical microhydro generators have outputs of 10 kilowatts (kW) or less and are usually connected to an off-grid power system with one or more inverters, batteries, and code-compliant load distribution and safety equipment. |
How does micro- hydro work (in our climate)? |
It should be completely obvious that the most challenging aspect of operating any hydro system is dealing with the water. Too much water can be an overwhelming force capable of destroying even the best engineering. Moreover, here in the Northeast, water freezes. If not planned for, frozen pipes and equipment can seriously damage a hydro installation. Typical "high-head" microhydro installations involve the placement of sufficient water pipe (PVC or polyethylene) to move water harvested from a high point in or adjacent to a stream to a lower point where the generator is located. The difference in height, known as "fall" or "head", determines the pressure at the outlet of the pipe which, in conjunction with the flow rate, determines the amount of energy that the hydro generator can deliver. The minimal useful head for most microhydro generators is around 20-30 feet which corresponds to an outlet pressure of about 10 psi (2.3 ft per psi). The flow rate through the pipe will be a function of its diameter and frictional loss. Ideally, the pipe is sized so as to always remain full throughout its length and, therefore, always maintain the full head pressure. Obviously, you need more water to keep a larger diameter pipe full than a small one. The design challenge is to size the pipe and its outlet nozzle(s) appropriately for seasonally changing conditions. The minimal useful flow for most microhydro generators can be as small as 2 gallons per minute (gpm) depending on the available head pressure. "Low head" microhydro generators can operate on as little as 6 feet of fall, but require a lot of flow to make useful power - typically 100's of gallons per minute. |
How do I know if I have a good microhydro site? |
Following on the preceding question, if you have enough head and flow and have designed the catchment, distribution and generating system so that it can't freeze (or to prevent its operation in freezing weather) and have connected the generator to a suitable energy storage system, then you should have the covered the basics for a useful microhydro installation. Quantitative measurement of both head and flow must be done in order to know how much energy your hydro site is capable of producing. Also, since there will be considerable seasonal variation in the flow rate of area streams, it is important to know how the flow rate will vary over time. Month-to-month and even year-to-year variability needs to be estimated in order to make even a rough approximation of total energy output from a hydro source. In the end, it is usually some combination of actual measurement and guess-timation that yields a final number. Indeed, uncertainty in microhydro potential often discourages its consideration as a feasible renewable energy option. On the other hand, equipment costs can be the lowest among renewable options, which may offset this uncertainty factor. Most manufacturers of microhydro generators have tables that show output as a function of flow rate and head. In addition to generator output, other aspects of system design such as battery capacity, voltage drop (wiring losses) and system loads will affect performance and should be considered. |
What can I expect from a Site Evaluation for microhydro? |
In general, don't even think of contacting us about microhydro unless you've done some preliminary research (suggested by the questions above) and really believe that you have a good site. It is not going to be worth the expense (to you) and the time and effort (for us) to visit your site unless we have a pretty good idea beforehand of its feasibility. During a Site Evaluation we will walk the stream and property (to the extent possible) to determine the best site(s) for the pipe run, hydro generator and balance-of-system equipment. By direct measurement and/or with help from a topographical map, we will estimate the available head. Again, by direct measurement and/or geometric calculation, the estimated flow rate will be a "snapshot" in time of a variable quantity, but will provide a first approximation to the available energy. Finally, we will assess how to couple hydro power generation with the power requirements of the home (or building or whatever) in the context of an off-grid or grid-connected renewable energy system. Hybrid systems incorporating PV and/or wind power in addition to microhydro can be designed to be grid-connected (and, possibly, to qualify for NYSERDA incentives - see the next question). Except under special circumstances, hydro-only generating systems can be accomodated only as off-grid designs (no incentives). |
Can I connect a microhydro system to the utility grid? |
Yes, grid connection of renewable energy systems (large or small) must be allowed under the 1978 Public Utilities Regulatory Policy Act (PURPA), but utilities do not usually allow them to be "net metered." Under existing NY state law, only residential solar electric, wind and biomass systems are allowed to operate as net metered systems in parallel with the utility, and only then where a signed contract exists between the "customer-generator" and the utility. As such, any grid-connected microhydro system is likely to be treated as a "commercial" system whereby its owner is compensated at the wholesale or "avoided cost" electric rate for energy exported to the utility grid. I have little doubt that net-metered small-scale hydroelectric power has been intentionally disallowed based on the potential for political upheaval and economic ramifications to the utilities. The history of small-scale hydroelectric generation in upstate New York is interesting and is the basis for this strong opinion. Nevertheless, Renovus has designed hybrid renewable energy systems with battery storage which utilize more than one charging source (PV and/or wind and/or hydro), and which may be grid-connected, but which do not sell back that portion of energy generated by the hydro source. Perhaps this is very clever, and perhaps not, but it serves to illustrate the artifice of placing any restrictions on what types of renewable, distributed generation systems may (or may not) be connected to and operate in parallel with the utility grid. So long as our environment is not compromised and power quality standards are met (e.g, UL-1741 for grid-interactive inverters), then energy is energy regardless of its source. Period. |
How much does it cost? |
Unfortunately, there are currently no grants or (NYSERDA) incentives to help offset initial costs for microhydro systems. However, on a per watt basis, microhydro generators are not as expensive as photovoltaics or wind turbines. Combine this with the fact that hydro is often a constant-output, 24/7 resource, and you have a compelling argument to invest if you have the resource available to begin with. That said, costs for PVC pipe, wire and other infrastructure have continued to rise along with other building materials (due to wars, hurricanes and attendant rebuiding efforts). "All-in" costs including labor for a small off-grid microhydro system (with inverter, batteries, load panel and code-compliant safety equipment) might come to anywhere between $10K and $30K, where labor is the largest variable. As with the other renewable energy options, a Site Evaluation is necessary to assess the possibilities and the costs. |
Hydro resource? |
Topographic maps showing streams, lakes or ponds which might be used as a microhydro resource are an excellent adjunct to on-site measurement of the actual conditions. For these small projects, USGS 1:24,000 scale orthographic quadrangles are the largest scale maps that are useful. Remarkably, all of the New York state maps have been scanned at relatively high resolution and are available free at this webpage of the NYS Geographic Information Systems Clearinghouse. |
System design? |
People often want to do a bit of research on their own before contacting us. This is good since it gives us some common ground for discussion. The following are links to manufacturers of microhydro generators and related equipment that can be employed in a variety of hydro sites.
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Permitting |
Permitting of microhydro energy projects is essentially uncharted territory which, like small wind energy projects, may involve several "authorities having jurisdiction" (AHJ's) including: local planning and zoning boards, local building department and code enforcement office, NYS Department of Environmental Conservation (DEC) and possibly others. Renovus now has considerable experience dealing with AHJ's throughout the state particularly for small wind projects. Likewise, for well-conceived and environmentally benign microhydro projects, we are prepared to advise clients and offer assistance in obtaining all necessary permits as an integral part of the process of design, permitting, installation, commissioning and ongoing maintenance. Because it pertains to permitting, it is worth noting here that large-scale hydroelectric projects have proven to be of questionable merit because they require substantial alteration of fluvial ecosystems to function. Yes, the dams provide energy, but at what cost to our lives, communities, and ecology? I implore you to read and listen to Arundhati Roy, an astonishing woman and global citizen, and hear what she has to say about "big dams" in India. Your understanding of the consequences of and motivations behind "development" will be changed forever. There seems to be an interesting parallel here with public objection to large-scale wind development projects in New York. Small-scale or micro-hydroelectric projects, like small-scale wind turbines, serve only local energy needs without compromising lives, communities and ecosystems when they are are conscientiously designed and operated. |
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