Micro Hydro Power

People have been tapping the energy in flowing water for centuries, first for mechanical power, and, in the last hundred years, for electricity.

Early applications included milling, pumping, and driving machinery. Unlike wind and sun, the right hydro resource can be available 24 hours a day, 365 days a year. This allowed pioneers to run irrigation pumps and grain mills, and more.

And it allows people today to make clean, renewable electricity at a reasonable cost.

What is Micro Hydro Power?

Hydro-electricity is fundamentally the combination of water flow and vertical drop (commonly called “head”). Vertical drop creates pressure, and the continuous flow of water in a hydro system gives us an ongoing source of pressurized liquid energy. Pressurized, flowing water is a very dense resource, and hydro-electric systems convert a very large percentage of the available energy into electricity because the resource is captive in a pipe or flume.

A simple formula can give you a rough idea of how much capacity your stream might have. Take the head in feet, multiply it by the flow in gallons per minute (gpm), and divide by a factor of about 12. This will give you the potential wattage of a reasonably efficient, small system. For example, if you have 30 gpm available and 40 feet of head, you will be able to generate something in the range of 100 watts [(30 × 40) ÷ 12 = 100). Over the course of an entire day, the generation would be 2,400 watt-hours or 2.4 kWh (24 hours/day x 100 W).

Within this formula is the understanding that systems with low vertical drop (head) need more flow to generate the same amount of energy. Typically, low-head systems will have high flow, and high-head systems will have lower flow. Adapting the example above, if we have 400 hundred feet of head, we only need 3 gpm to generate the same 100 W.

There are a wide range of small hydro turbine types to suit the head and flow of the site. Large wooden overshot and undershot wheels tend to be less efficient for generating electricity, though they may be appropriate for mechanical work. For electricity generation, systems can be divided into “low head” and “high head.”

Low-head systems may have less than 5 feet of vertical drop—sometimes they may have only 10 or 20 inches. In this case, most or all of the water in a small stream will run through the turbine to maximize output. The runner (the part of the turbine that receives the water and turns its energy into rotation in a shaft) for low-head turbines may be a Turgo or Francis type. These systems typically have short pipelines or sluiceways that then allow the water to drop through the runner.

High-head systems may be defined as any site with more than 10 feet of head. Common runners are Turgos on the low end, and the most common, Pelton, for medium to high heads. These systems may have hundreds of feet of pipeline to develop the head (pressure), with the water delivered to the runner via multiple nozzles.

The basic components of a small hydro-electric system, running from “water to wire” are:

  • Diversion and intake screen—Directs water from the stream or river into the pipe or channel
  • Penstock (pipeline)—Carries the water to the turbine
  • Turbine—Generates electricity (includes nozzles, runner, and generator)
  • Electronics and batteries (if used)—Regulates turbine and stores energy
  • Dump load—Absorbs surplus energy
  • Transmission and distribution—Delivers the energy to its end use

Why Use Micro Hydro Power?

People choose micro hydro-electric systems for a variety of reasons. Environmental motivations are very common. Microhydro-electric systems can eke a large amount of energy out of a small water flow with minimal impact. Because they run 24 hours a day, these systems can be low-wattage while generating enough energy to make a big dent in a typical home’s energy use, and, in off-grid systems, even minimize or eliminate the need for having batteries. While care needs to be taken not to impact wildlife, micro hydro-electric systems can be unobtrusive, use only a portion of stream flow, and quietly produce clean electricity with almost no ongoing impact. While all energy generation and use has some impact, it’s instructive to compare the impact of grid sources such as coal, oil, and nuclear with renewables. If we had a truly level playing field, where all players had to take their cost, embodied energy, and environmental impact into account, small hydro systems would likely be shown to have the least impact.

In situations where the resource exists reasonably close to the end use, and pipeline and transmission distances can be moderate, hydro-electricity may be more economical than tapping other renewable resources. A combination of a solid resource, a well-designed system, good maintenance, available incentives, and utility costs may even make a compelling economic argument to tap that stream on your property. Microhydro systems can, at a minimum, save you dollars, while providing clean, reliable electricity.

These systems can make you entirely independent of the grid, or they can be connected to the grid, allowing you to “sell back” surplus electricity for a credit and providing backup when the utility fails, giving you the best of both worlds. Additional benefits include that maintenance is done at ground level (unlike wind) and the system’s production is around the clock (unIike wind and solar). If you want a reliable electricity supply, it’s hard to beat a micro hydro system.

Types of Micro Hydro-Electric Systems

As with wind- and solar-electric systems, hydro-electric systems can be divided into four configurations:

  • On-grid without batteries. This a simple and efficient system that sends any surplus energy back into the grid to be credited to you for use at other times. These systems typically do not provide backup for utility outages.
  • On-grid with batteries. This system type also sells back surplus electricity, but also provides backup during utility outages. The amount of backup will be determined by the system’s capacity and the battery size.
  • Off-grid without batteries. This configuration is generally for larger, AC-generating systems. The peak load capacity (how many things you can operate at once) is determined by the hydro system’s peak generating capacity. This configuration is generally not used for systems that generate at less than about 2 kW.
  • Off-grid with batteries. This is the most common off-grid option, and is similar to off-grid solar- or wind-electric systems. The charging source puts energy into a battery bank, while loads are run from the batteries—directly, if DC; via an inverter, if AC.

Microhydro-electric systems can power most, if not all, electrical loads, depending on the size of the resource. The smallest systems may only provide for lighting, electronics, and basic refrigeration. But with sufficient head and flow, these systems can run heating and cooling systems, tools, and even commercial equipment in a modern, on-grid home, ranch, or business. The head and flow are the limitation, and it all comes down to how much power (wattage) and energy (kilowatt-hours) you have at your disposal.

While people with solar-electric and small wind-electric systems may be pushed toward serious efficiency and conservation measures because of the cost of these renewable kilowatt-hours, small hydro systems frequently have ample resources behind them, and can be more generous with their output. However, using your energy wisely can mean using less water and smaller equipment, which means lower environmental impact and lower cost.

Get Started with Micro Hydro Power

After you’ve done your load analysis and know how many kilowatt-hours you want to generate, a micro hydro system site survey primarily focuses on four measurements:

  • The flow—how many gallons per minute (or in larger systems, cubic feet per second) are available, and how much water you want to divert from the stream;
  • The head, or vertical drop, between where the water is removed from the stream and where it leaves the turbine runner. Exactly where or how the pipeline runs is not vital for this measurement, though calculations of losses for pipe and fitting friction will need to be made;
  • The pipeline length, which, combined with its diameter, will allow you to price what may be one of the most expensive parts of the system;
  • The length of the transmission wiring, which may also be a significant cost, and must be sized to minimize energy losses, and be well within safety parameters.

For most people, a combination of motives—environmental, independence, reliability, and cost—make hydro-electric systems attractive. The “bottom line” may end up being what the actual cost per kWh is. To arrive at this, you’ll need a complete design along with construction bids or estimates. If it’s a grid-connected system you’re after, you’ll also need to know what your local utility policies are for renewable energy systems, and at what amount you will be credited or paid. You’ll also need to know if any incentives (utility or government) exist. Often, micro hydro system incentives are less than those for solar energy systems, and sometimes non-existent. Available incentives, though, may be generous because of hydro’s 24-hour generation capability. Once you have these figures, you’ll need to predict how many years your system will operate and the annual maintenance costs, and then you’ll be able to calculate the cost per kWh.

Throughout your design, consider strategies to get the most out of your precious flowing water resource. Properly sizing the pipe will get the most energy to your turbine, minimizing friction loss. Choosing the right turbine and runner for the job will maximize production for your stream’s specific head and flow. And sizing the wire correctly will keep the system safe, and keep you from losing energy in the transmission of your hydro-electricity.

Get an education about common hydro myths, and avoid scams or schemes that promise more than they deliver. Lean on professionals and others with experience in the field to discover what has worked well to produce hydro-electricity. If you do your homework, and apply what you learn with care, hydro-electricity can provide low-cost, clean energy for many years.

Micro Hydro Myths and Misconceptions

Making electricity from falling water can seem like magic, and that’s led to lots of misconceptions. Here, we’ll separate fact from fiction when it comes to what micro hydro systems can and cannot do.

Residential-scale micro hydro-electric systems have the reputation of being the holy grail of home renewable-energy (RE) systems. While they lack some of the hype, magic, and bling of solar-electric (photovoltaic) systems, micro hydro systems are a simple technology that most people can understand…at least in general. In this article, we’ll look at some common micro hydro system misconceptions, most of which come from folks looking for shortcuts to the reward of cheap electricity. 

Modern micro hydro equipment comes from proven technology based on designs that have changed very little over the decades. Pelton and turgo wheels, the typical spinning water-wheel component, were invented in 1870 and 1919, respectively. The point is, this technology has proven its reliability and functionality with more than a century of performance.

The cost of these systems, and thus the cost of the resulting electricity, also has the reputation for being very reasonable when compared to other renewable or home-generated sources. While PV module prices have recently dropped, they are still a high-tech and expensive commodity. Microhydro systems can arguably be considered low-tech, with civil works and pipelines often being the majority of the system cost. Of course, the actual cost varies significantly from site to site, and from system to system.

Another element that keeps micro hydro-generated electricity low in cost, and thus high in desirability, is the system’s continuous duty cycle. While PV systems only produce electricity when the sun is shining (and wind-electric systems when the wind is blowing), micro hydro systems aren’t affected by nightfall or weather blocking the sun. Even a small hydro resource can provide electricity 24 hours a day, and often 365 days a year (if the water source is year-round). The bottom line for any renewable energy system is the amount of energy it can produce annually. A low power source working all of the time can often produce a lot more energy than a more powerful source that only works intermittently.

So, why doesn’t everyone have a micro hydro system? Herein lies the challenge. A viable hydro resource is dependent on the availability of falling water at, or near, the site of the electrical loads. It is the weight or pressure of that flowing water that spins the turbine to produce electrical energy. Not everyone has access to a stream or spring of adequate volume on their property, nor does everyone have the topography to create the vertical drop needed to pressurize that water with gravity. See the “Microhydro Rules” sidebar for a formula about how water flow and vertical pressure (head) combine to determine the power available from a potential hydro site. That site-assessment formula will help debunk some of the myths that follow.

Many micro hydro misconceptions are a combination of misunderstanding some of the basic properties of physics, and an overzealous optimism about the potential of RE resources. Here, we hope to correct the misconceptions about physics, while at the same time further encouraging educated optimism. Once you’ve had a little reality check here, we suggest you read some of Home Power’s other articles on the basics of hydro site assessment and micro hydro systems (see Access at the end of this article). Perhaps you really do have untapped hydro potential waiting for you.

Myth 1: Closed-Loop / Pumped Storage

By far, the most common flawed design that we hear about at Home Power is the closed-loop system—that is, some scheme to pump water for the hydro turbine, and then have the turbine produce the electrical power for the pump…ad infinitum. Some of these schemes are simple “hydro-in-a-bucket” designs where the pump is expected to pressurize the water for the hydro turbine. Others are more involved, planning to pump water uphill to a pond or tank, and then let gravity do the job of running the turbine. All the while, the designer is expecting to get extra usable electric power from the turbine’s output—beyond what the pump is using. Whether large or small, all of these designs suffer from the same flaw in thinking.

The first law of thermodynamics says that energy can neither be created nor destroyed. All of the energy systems (renewable and otherwise) that we rely upon convert existing energy into a form that we can use to do the work we want to do. In a hydro-electric system, the energy of moving water is transferred to a rotating shaft, converted to changing magnetic fields, and then converted to moving electrons (electricity). But at no point is energy created. If we use that energy to create magnetic fields again, spinning a shaft and pumping water up to a tank on a hill, we still haven’t created any energy. We’ve just changed its form again. 

In a perfect universe, perhaps it could be argued that such a pump and turbine arrangement could run perpetually. But it wouldn’t do us any good, because we want to use that electricity to do some work besides just running the pump. Using any electricity for other tasks would be robbing the pump of the power it needed to keep up with the turbine, and the loop’s interdependence would break down. That, and the fact that there are always other forces robbing energy from the system, means that such a loop wouldn’t run for long, and that no additional energy could be extracted from it.

Those additional energy-robbing forces, mostly friction, are the imperfections that cripple this closed-loop design. Every component of such a system has an operating efficiency of less than 100%. That means each conversion step in the process wastes some of the potential energy that the system started with. We know that energy is not being destroyed, but it is being allowed to escape the loop in the form of heat, vibration, and even noise. It is being converted into a form that we can’t readily use, or even recover. 

Let’s look at some typical micro hydro system efficiency numbers:

  • Penstock (pipeline) efficiency = 95%
  • Nozzle and runner efficiency = 80%
  • Permanent-magnet alternator efficiency = 90%
  • Wiring and control efficiency = 98%

0.95 × 0.80 × 0.90 × 0.98 = 0.67

By the time the water has moved through this example micro hydro generator system, only 67% of its initial potential energy has been converted to electricity. In fact, this would be considered very good performance—typical systems are about 55% efficient.

Now let’s consider the efficiencies of pumping that water back to the hydro intake for reuse: 

  • Pipe efficiency = 95%
  • Pump (motor and impeller) efficiency = 65%

0.95 × 0.65 × 0.67 (from above) = 0.41

By the time the water had gone all the way through the system, only 41% of it would be returned to the top of the intake. After a second loop around, only 17% (0.41 × 0.41) of the water would be left. 

If there isn’t a water supply with useful head and flow to start with, nothing will happen—the pump won’t run because it won’t have electricity; the hydro turbine won’t have electricity because the pump isn’t running. Adding water (or electricity) to “prime” the loop will make the loop operate only as long as the priming continues. 

This is where creative folks start asking questions about bigger water tanks; larger pipes with less friction loss; tanks on a tower for shorter pipe runs; more head, and less flow; less head and more flow; adding batteries (only 80% efficient themselves); or even just piping right from the pump to the turbine—anything to improve system efficiency. In fact, the simplest thing that could be done to get rid of inefficiencies would be to skip the water components altogether; just hook the shaft of a motor directly to the shaft of the alternator, and the alternators output wires directly to the motor (somehow, the fallacy in that thinking is easier for us to understand). But no matter the variables, the outcome will be the same—total efficiency will be less than 100% and no energy will be gained. 

Moving energy around and changing its form, like from chemical to mechanical to electrical, is only a way to lose some of it. These efficiency losses are part of the price we pay to get energy into a format that we can use. We can lose more, or we can lose less, but adding complexity is inefficiency and will never result in a net gain.

Myth 2: Rooftop / Downspout Hydro

A second common micro hydro-electric scheme that we are often asked about is the viability of putting turbines on a home’s gutter downspouts to generate electricity from the rain. Some imaginative folks know enough about hydro to understand that the energy has to come from somewhere (in this case, from the forces of nature), and that the height of the roof can contribute head (pressure) to spin that turbine.

The mistake in this scenario is a simple and honest one of scale. While some hydro units have been designed that can function on low head, such as from the roofline of typical homes (and even lower), a hydro turbine’s power output is a product of head times flow. And it is a lack of significant flow that is the defeating factor in the power equation when relying on rooftop rainwater collection. The watershed drainages for even small streams are usually measured in thousands of acres or square miles. Home roofs, even big ones, are measured in mere thousands of square feet.

Let’s look at example calculations for a large house in a very rainy place—Seattle, Washington, gets about 40 inches of rain per year, with November being the rainiest month at an average of about 6 inches. 

Let’s assume that a tall two-story house would give us a 25-foot-high roof, and thus 25 feet of head. This 6,000-square-foot home has about 3,000 square feet of rainwater collection area (remember, it’s two stories). That means that in November, this house would receive about 1,500 cubic feet of rain, or 11,220 gallons.

If that rainfall came as a constant drizzle all month long, flow from the roof would be only about 1/4 gallon per minute. Currently there is no turbine on the market to work with that flows that low, but using our micro hydro power formula (see sidebar), we could theoretically get 468 watt-hours that month. 

0.26 gpm × 25 feet ÷ 10 derate = 0.65 watts × 720 hrs./mo.

= 468 Wh

So even if there was a nanohydro plant that could harvest that small flow, it would result in less than 1/2 kWh of electricity—per month!—and only 3 cents worth of electricity in Seattle. It’s a tiny fraction of what even an energy-efficient, 6,000-square-foot home would use in a day, not to mention a whole month. 

Would the available energy increase if we weren’t dealing with a constant drizzle? What if, to increase flows to a usable rate, and hopefully increase viable energy production, we could hope that all that rain came in a great deluge of 1 inch per hour (a 100-year storm, in Seattle) over six hours! At that unlikely amount of rain—practically all at once—flow from our example roof would be about 31 gpm. That is a more viable flow rate for hydro turbines on the market and gives us a projected power production of 77.5 watts, but only for those six hours. The total of 465 Wh per month is about the same energy as the drizzly example above (the minor difference is from rounding significant digits). 

This is when inventive thinkers will begin planning for taller homes, or additional rain-collecting roof areas, and tanks to hold the water for release all at once to increase flow. But even that 11,220 gallons of water that falls on our 3,000-square-foot roof that month would weigh almost 47 tons if stored. Imagine a structure at roof level capable of supporting that kind of load just to generate a minuscule amount of energy. And remember, these discouraging energy production numbers are for the rainiest month, in one of America’s rainiest cities. Other months, other places, and smaller houses can only deliver worse performance.

In this case, it would be better to just spend the money on a PV system. To put things into perspective, even in Seattle, which gets only an average of 1.7 peak sun-hours per day in November, an inexpensive (less than $100) 15-watt PV module would make close to the same amount of energy as the proposed rooftop hydro system.

Myth 3: Hydro from Municipal Water Supply

So, a thinking person might begin wondering where they could get good water pressure and adequate flow necessary to run a micro hydro turbine. It’s the kind of question an inspired hydro wannabe might ponder, say, while standing in the shower. And that’s when another common hydro scheme is hatched.

Typical municipal water pressure is between 40 and 80 psi, the equivalent of 92 to 185 feet of head. That is definitely enough for a hydro system. And if available flow is about 10 gallons per minute, say at the bathtub faucet, then surely there must be some real power available whenever we turn on our faucets. 

However, if we use our example power formula with a common pressure of 60 psi (138 feet), we get a projected power output of about 138 watts.

138 ft. × 10 gpm ÷ 10 derate = 138 W × 24 hrs.

= 3,312 Wh per day

That 3.3 kWh per day is something—but not a lot. An average American household uses about 30 kWh per day, so would need nine of these units.

For the sake of argument, let’s assume a very energy-efficient home that could run on 3.3 kWh per day. Why not then use such a hydro system? Or, why not offset a portion of a home’s loads with hydro? Every little bit helps, right?

The 3.3 kWh figure is based on using 10 gallons per minute—24 hours per day. That’s 14,400 gallons per day. At an average cost in the United States of $1.50 per 1,000 gallons, that’s $21.60 per day in water costs just to generate 36 cents worth of electricity (based on the U.S. average of $0.11 per kWh). 

Then there is the ecological and moral impact—remember, this is water that has been treated and purified for human consumption, and uses pumps to maintain that pressure—processes likely paid for in part with taxpayer money. Costs aside, what are the implications of pouring good clean water down the drain just to make a little electricity?

Finally, just to add a final coup de grâce to this hydro scheme, remember that most of what we do with our domestic water requires water pressure, as well as flow, to get the job done. Taking the energy out of water to make electricity robs that water of its pressure—water merely falls dead (depleted of energy) out the bottom of a hydro turbine. And pressure at other faucets may be anemic at best—imagine trying to rinse shampoo out of your hair while a hydro system is running full-bore in the same home. Not so effective, or enjoyable.

Myth 4: Reducing Pipe Size to Increase Pressure / Power

There is no substitution for head and flow in an effective micro hydro system. When head is inadequate, we begin to think of creative ways to increase pressure. The simple example of watering the garden with a hose comes to mind. Doesn’t putting your thumb partially over the hose opening increase the pressure, shooting water farther across the lawn? What if you use a spray nozzle instead of your thumb? Didn’t you just increase the power of that system by reducing the size of the nozzle? And therefore, couldn’t you increase head (and thus power) in a hydro system by starting off with a large pipe diameter and then reducing the pipe size on the way to the turbine?

Sorry, but no. When a pro measures head in a hydro system, they note two different types. Static head is the pressure at the turbine with the bottom valve closed, and thus no water moving. It is the pressure, from the weight of all the water in the pipe above the turbine. This pressure, measured in pounds per square inch (psi), is in direct proportion to the height of that column of water. For every 2.3 feet of vertical head, you’ll measure 1 psi. Because it is directly proportional, there’s no need to put in pipes and fill them with water to measure it; just measuring the vertical drop between water source and turbine site will give you an accurate static head.

But static head is just a maximum starting point. Dynamic head is the adjusted theoretical pressure in the system when inefficiencies like friction loss of pipes, joints, elbows, and valves are considered. These things hinder the flow of water through the system, and therefore some of its potential energy. Dynamic head is the result of static head minus these power losses, and provides a more accurate estimate of turbine performance.

Adding a smaller pipe section or nozzle is basically adding another restriction in the pipe that creates resistance to the flow of water. It effectively lowers the dynamic head of the system and thus also lowers the total power available in the system.

“Wait,” you say, “what about the hose spraying farther across the yard?” Or maybe you are savvy enough about hydro systems to know that impulse turbines actually use nozzles to shoot a stream of water at the spinning runner. Well, you are right, but neither pressure nor power are being increased by the nozzle. Instead, the existing energy is being concentrated into a smaller point and at higher velocity—which is a more usable form for the turbine—but, in the process, some of that energy is lost to friction.

The purpose of a nozzle is to increase the kinetic energy of the flowing water by increasing its velocity. But this is at the expense of its potential energy in the form of pressure. In fact, on the outlet side of a nozzle, there is no pressure in the water; it is carrying all of its energy in the form of fast-moving kinetic energy. And it is the force of this kinetic energy against the turbine’s runner that makes it spin. But no increase in energy was created. In fact, that water moving faster through a nozzle has more friction loss, reducing our dynamic head and total available power in the system—less power, but in a more useful form.

There is never any more power available than the theoretical maximum based on the initial static head (at a given flow). Every component and change in the form of energy in the system acts as an inefficiency, reducing actual available power. Some of those losses are necessary ones (getting the water down the hill, shooting it at the runner, etc.). Good design can reduce losses, but they can never be eliminated completely. And they definitely can’t be changed to net gains.

Myth 5: In-Flow / No-Head Systems

It’s starting to sound like only those folks with a stream or river on their property have a viable hydro system. But if you do have a good-flowing stream, you’re all set for hydro power, right? Well, it’s even more complicated than that.

We know that the power available to typical hydro turbines is a product of the head (pressure) and flow rate. So we also know that as head decreases, flow must increase to make the same amount of power. But what about folks with a nice river flowing along relatively flat ground? There must be some energy available in that strongly moving mass of water, even though it isn’t falling from a height, right? Well, yes and no.

Besides just turbine size, there are different turbine technologies designed to take advantage of the ratios of head-to-flow at a given hydro site. But as head decreases, the energy gets harder and harder to capture. Reaction turbines, designed for low heads (as low as 2 or 3 feet) spin inside a column of falling water, but need high flow for significant power.

But what about situations with basically no head at all? What about that big river flowing through a flat plain? Well, try putting zero head into our hydro power equation and you will find that, no matter how much flow there is, the power output will be zero, too. To be fair, there must be some head for the water in a stream to be moving at all, and thus there must be some power there to capture. But even though the movement of that flat-water stream looks enticing, there isn’t much potential to start with, compared to the same water dropping down a hillside. And then there’s the challenge in capturing it.

To make up for lack of head, flow would need to be substantial. Either the river must be flowing very fast, and/or a very large area of river must be captured. Both create challenges in the integrity of the mounting structure and turbine runner itself, plus the added danger from river debris. 

A fast-moving river is often only moving fast in the center. Near the banks, shallows, or along the bottom, friction reduces the flow. The speed of the river in the center can’t necessarily be extrapolated to the whole cross-sectional area. Instead, there are specific formulas to account for the reduced flow along the bottom and shallow sides of a stream.

And even a quickly flowing river is moving a lot more slowly than the runner in a jet-driven impulse turbine in a system with higher head. A slowly spinning runner needs to be geared to create the rotational speeds necessary to generate electricity with an alternator. The gearing adds further complexity and friction loss to the system—more inefficiency.

We’re not saying that it can’t be done. But we are saying that it’s unlikely that you can buy anything off the shelf that will do an adequate job for you. There have been, and will continue to be, many inventions intended to capture energy from the flow in a river. These “in-flow” or “current turbine” designs come and go, and come again, but we rarely see anything that performs to a level that warrants a reliable consumer product. There are a couple of in-flow products on the market (Ampair and Jackrabbit) that were originally designed for towing behind sailboats or barges. Some have adapted these to use in streams, but the small swept area of their propeller requires high-velocity flow to make much usable power.

If you are a tinkerer, and enjoy the creative challenge of hydro design, you may be able to fashion an in-flow turbine to make some power (though it may never pay back financially). But if you are being tempted by commercially available in-flow turbine designs, caveat emptor. Do your homework by talking to other reputable hydro installers about your resource and options. Be realistic about your capturable stream area and flow rate. And ask for real-number data, and references, from the turbine manufacturer.

Head & Flow: Check Your Reality

While micro hydro power is a reliable and proven technology, often at a reasonable cost, it’s completely dependent on the resources available on a site-by-site basis. Either your site has reasonable hydro potential, or it doesn’t. And it all depends on the quantities of head and flow. There’s no cheating the laws of physics. There is no way to create energy. There is no free lunch.

That doesn’t mean that there aren’t ways to optimize your hydro potential to get the most energy out of your resource. That’s where professional designers and reputable manufacturers come in. They have the knowledge to make decisions on siting and equipment that will maximize the energy made from the head and flow that is available. Intake type, pipe sizing and routing, the size and number of nozzles, runner type, alternator size and type, controller type, and system voltage are all variables that, when combined properly, will make or break your system performance and financial viability.So give up on the free energy designs. Instead, read some of Home Power’s real-world articles on hydro system design, do a preliminary measurement of your stream’s actual head and flow, and call a reputable micro hydro professional. That’s the best scheme for maximizing your hydro system’s performance.

Originally published at HomePower.com