| Part of the beauty of hydropower lies in its simplicity. | | | | equal, but opposite, reaction force." The water moves |
| Moving water (kinetic energy) spins a turbine or wheel | | | | through the turbine, losing pressure, which forces it to |
| (mechanical energy), which drives a generator | | | | give up its energy. The turbines have to be either |
| (electrical energy). Archaeologists have found | | | | encased (to contain the water pressure or suction) or |
| evidence of water storage dams in Jordan, Egypt and | | | | be completely submerged by the flowing water. Water |
| elsewhere in the Middle East that date back 5,000 | | | | wheels are reaction turbines. Most turbines are |
| years to 3000 BC. One of the earliest designers to | | | | reaction-type turbines. They are used for systems |
| document his plans was Vitruvius (c.70 BC-c.25 BC), a | | | | with low and medium heads. |
| Roman architect and engineer, who described an | | | | A typical microhydro system, then, needs a stream, an |
| undershot waterwheel that could generate power. The | | | | intake system, a penstock, and a powerhouse. |
| Romans built many waterwheels, with the most | | | | Although the actual components are much more |
| ambitious being the one is Barbegal, France, in the 4th | | | | high-tech and specialized, you can envision a high-head |
| Century AD. Connected to a large aqueduct system | | | | microhydro system as this as a box or funnel at the |
| that fed water to the city of Arles, Barbegal was a | | | | top of a waterfall, a garden hose or a trough running |
| massive flour mill with not one but sixteen | | | | downhill from the intake, the water from the hose |
| waterwheels in two parallel rows. The water turned | | | | trough shooting onto a turbine (probably Pelton-style), |
| the first pair of wheels, then flowed downhill to the | | | | and the turbine turning a generator. A low-head |
| second pair, then downhill again and so on until it had | | | | microhydro system is equally simple. They have a |
| flowed through and turned all eight sets, after which it | | | | screened intake (or a mini-dam), and this feeds into a |
| ran into a runoff pool at the bottom of the hill. | | | | settling basin or forebay for any silt to precipitate out; |
| Today hydropower generates about 15 percent of the | | | | this empties into a short canal that feeds into a |
| world's electricity (about 6 percent of the total energy | | | | ten-foot draft tube. The water flowing through turns a |
| supply). Rather than using waterwheels on a moving | | | | turbine (probably Turgo-style). Note that in neither case |
| river or through a duct, most hydroelectric plants | | | | do you block or divert the stream (for which you |
| extract energy from the potential energy that comes | | | | would need a permit anyway, even if the water is on |
| from the vertical distance the water drops (the "head"). | | | | your property, and which may turn out to be prohibited |
| The water is channeled through a sluice or gate, or | | | | in your area). |
| through enclosed pipes that funnel the water down to | | | | Hydropower Advantages |
| the turbines; these channels are called penstocks. | | | | 1. As long as the water is there in sufficient quantity, |
| Hydroelectric Plants The typical hydroelectric plant | | | | hydro stations can generate power 24/7. |
| needs four things to generate power: | | | | 2. Large hydro stations can shift into maximum |
| Dam - The dam holds back a river, raising the level, | | | | capacity to meet peak demands simply by controlling |
| and controls the flow through the penstock(s). Dams | | | | the amount of water released. |
| create reservoirs that can be used for recreation, but it | | | | 3. Microhydro systems produce no pollutants. |
| is the height difference between the stored water | | | | 4. Hydropower is a renewable resource. |
| above and the turbines below that represents the | | | | 5. Most countries have access to waterways that can |
| potential energy. | | | | be used for hydro power. |
| Turbines - The water behind the dam is channeled | | | | 6. Large dams can be useful for flood control. |
| through the penstocks past the blades of turbines, | | | | 7. Microhydro systems can provide power without |
| which spin. This converts the kinetic energy to | | | | affecting water quality, without affecting the habitat, |
| mechanical energy. 2. Turbine. The force of falling | | | | and without altering the course of the river or stream. It |
| water pushing against the turbine's blades causes the | | | | leaves a very tiny footprint. |
| turbine to spin. A water turbine is much like a windmill, | | | | 8. Large and mega-dams can create recreational |
| except the energy is provided by falling water instead | | | | lakes in areas where before there were none. |
| of wind. The turbine converts the kinetic energy of | | | | Hydropower Disadvantages |
| falling water into mechanical energy. | | | | 1. Large hydro stations that create reservoirs actually |
| Generator - The shafts of the turbines turn a | | | | dump huge amounts of methane and CO2 into the |
| generator, thus converting the mechanical energy to | | | | atmosphere. When the area behind the dam is flooded, |
| electrical energy. | | | | the trees and other plant material that get covered up |
| Transmission lines - The electricity is transmitted to | | | | rot and sift to the bottom where they continue to |
| substations and transported to consumers through the | | | | decompose without oxygen. This creates methane, |
| power lines. | | | | which is released when the water flows through the |
| Microhydros Hydroelectrical plants are big and | | | | turbines. |
| powerful, but did you know that you can have your | | | | 2. The reservoirs created by large dams and |
| very own microhydro plant? All you need is a stream | | | | mega-dams destroy local habitats. When the area is |
| or a river with enough water running through it at the | | | | flooded, plant life is submerged, and any animal and |
| right pressure, and you can set up a system that | | | | human life in the area must relocate or perish. |
| feeds into turbines and generators, and into your home | | | | 3. Large hydroelectric dams are expensive to build. |
| or business. Just as you can with your solar and/or | | | | 4. Large hydroelectric dams can only be used in a |
| wind systems, you can design a system that is | | | | limited number of places those with large water |
| grid-connected with battery backup, grid-connected, or | | | | supplies. |
| standalone. | | | | 5. Damming rivers and streams changes the natural |
| Microhydros come in two basic flavors: low-head and | | | | waterways, diverting water from areas that depend |
| high-head. Head, you'll recall, is the height differential | | | | on it. |
| between the water and the turbine. That corresponds | | | | 6. Damming rivers changes the quality, quantity and |
| to pressure. Think of a high-head system as one | | | | even the temperature of the water that flows |
| running off a waterfall, and a low-head system as one | | | | downstream. This can have disastrous effects on |
| running off a fast-moving stream, although that isn't | | | | agriculture as well as potability. |
| always the case. | | | | 7. Changing the path of a river can cause serious |
| In a quick search online for microhydro resources, the | | | | disputes between neighbors, from individuals to nations. |
| names "Don Harris" and "HarrisHydro Systems" turn up | | | | 8. Water moving over a dam can pick up nitrogen, |
| over and over, with good reason: Harris is a well | | | | causing fish kills downstream. |
| known pioneer in microhydro. He designs and | | | | 9. Many small and medium dams built in the past to |
| manufactures turbine and generator systems in a shop | | | | power industries such as mills and factories are no |
| that he powers with a microhydro system of his own. | | | | longer used, and are growing unstable. Allowing them |
| His designed feature a Pelton wheel, a highly efficient | | | | to self-destruct rather than removing them in a |
| tangential-flow impulse turbine with spoon-shaped | | | | controlled manner can lead to serious flooding, including |
| blades that capture a jet of water. | | | | loss of life and property. |
| Impulse turbines transfer energy according to Newton's | | | | 10. Dams alter the spawning patterns of the fish, and |
| second law of motion, which is roughly paraphrased as | | | | often result in absenting entire species from an area. |
| "the momentum of an object, or force, is equal to the | | | | 11. When large amounts of water are released from a |
| object's mass multiplied by its acceleration. It works like | | | | large dam or mega-dam the shores of man-made |
| so: first, the water's potential energy (the head) is | | | | reservoirs naturally recede, leaving behind mud flats |
| converted to kinetic energy by being funneled through | | | | and reducing the surface area leaving less space for |
| a nozzle to form a jet. The jet of water moves at a | | | | fish. Sometimes Mother Nature plays a role, as with |
| given velocity, but when it strikes the spoons/buckets | | | | Lake Powell, created by the Glen Canyon Dam. With |
| of the turbine, it loses velocity or acceleration, so the | | | | reduced flow of the Colorado River, evaporation, and |
| momentum changes. That change in momentum | | | | seepage back into the canyon banks, Lake Powell |
| translates to an exertion of force that turns the shaft. | | | | loses an average of 860,000 acre feet of water each |
| The water pressure itself doe not change. Impulse | | | | year about as much water as Los Angeles consumes |
| turbines are the most commonly used turbines in | | | | annually. While it is perhaps one of the most beautiful |
| domestic systems, and those with high heads. | | | | lakes in the U.S. with its red-rock canyon sides, 150 |
| Reaction turbines transfer energy according to | | | | feet below its 266 surface miles lie centuries of |
| Newton's third law of motion, which is roughly | | | | archaeological riches as well as the canyon itself. |
| paraphrased as "for every action force there is an | | | | |