Microhydro

Nothing is softer or more flexible than water, yet nothing can resist it. ~ Laozi

Small scale hydroelectric (microhydro) power is not a new idea. In fact, harnessing the flow of water to do work is one of the oldest forms of renewable energy (think water wheels). Widespread adoption of microhydro is difficult, because access to a good water resource is not common. However, if you have a stream or pond on your property, you may be a candidate for generating your own electricity using a microhydro turbine.

For more information, fill out our secure Client Information Form for microhydro systems, or send e-mail, or give us a call.

What is meant by "micro" hydro power?
How does microhydro work (in our climate)?
How do I know if I have a good microhydro site?
What can I expect from a Site Evaluation for microhydro?
Can I connect a microhydro system to the utility grid?
How much does it cost?
Where can I read more about microhydro system design?
A word on permitting...

What is meant by "micro" hydro power? (back to top)

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. The term microhydro is meant to distinguish very small-scale, point-of-use hydro power from these industrial scale, centralized power generation projects.

As with 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 microhydro work (in our climate)? (back to top)

It should be 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 engineered system. Moreover, here in the Northeast, water freezes. If not planned for, frozen pipes and equipment can seriously damage a hydro installation.

The two most important parts of a microhydro system are head and flow. The difference in height from the beginning to the end of the installation is known as the "fall" or "head." This distance determines the pressure at the outlet of the pipe. The flow of water measures the amount of water traveling downstream. Typical "high-head" microhydro installations involve the placement of sufficient water pipe (PVC or polyethylene) to move water harvested from a high point to a lower point where the generator is located. The amount of head and flow 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? (back to top)

Following on the preceding question, the two most important parts of a microhydro system are head and flow. It is also important to design the catchment, distribution and generating system so that either it can not freeze, or to prevent its operation in freezing weather. Finally, the generator must be connected to a suitable energy storage system.

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.

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.

In the end, it is usually some combination of actual measurement and guess-timation that yields a final number. Indeed, the 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? (back to top)

Please complete preliminary research suggested by the questions above before contacting Renovus about a microhydro system. 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 of its feasibility beforehand.

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 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 accommodated only as off-grid designs (which means that no incentives are available).

Can I connect a microhydro system to the utility grid? (back to top)

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.

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.

How much does it cost? (back to top)

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 "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 $10,000 and $30,000, 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.

Where can I read more about microhydro system design? (back to top)

It is useful to do a bit of research on your 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.

Harris Hydro: Manufacturer of high-head, low-flow Pelton wheel turbines. Don Harris is one of the pioneers in microhydro technology.
Alternative Power & Machine: Manufacturer and reseller of a wide variety of microhydro turbines and diversion loads.
Energy Systems & Design: Manufacturer of the Stream Engine for high-head, low-flow sites and LH1000 for low-head, high-flow sites.
Hi Power Hydro: Manufacturer of higher voltage AC microturbines for power transmission over relatively long distances (up to 1 mile).
Canyon Hydro: Manufacturer of mid-scale systems for residential and commercial applications. Dan New's website is an excellent introduction and guide to hydro power.

A word on permitting... (back to top)

Permitting of microhydro energy projects is essentially uncharted territory which, like small wind energy projects, may involve several "authorities having jurisdiction" including: local planning and zoning boards, local building department and code enforcement office, New York State Department of Environmental Conservation and possibly others. 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.