Hydropower – The original green energy

When the Europeans came to North American over two hundred years ago, they found an abundance of streams and rivers. On some of these water sources, dams and millponds were constructed to provide power for communities.

They were perfect to turn a water wheel that supplied mechanical power to run the mill equipment. When electrification came, the mill ponds and water wheels were replaced by the electric motor.

Today, there is a strong emphasis on green energy production that can be produced using technologies like wind turbines or solar photovoltaic panels.

We are making more green energy than ever, but wind and solar have their limits. At night, solar panels produce no electricity and on cloudy days they make very little. On calm days or on hot and humid days there is little wind for wind turbines to produce electricity.

So, is there a renewable energy source that can produce energy when these two cannot?

The answer can be found in hydropower.

The National Hydropower Association has determined that only 3% of the 80,000 registered dams in the United States are currently being used to generate electricity. There are projections that if less than 20% of the unused dams were to be converted to harness water power, they could easily provide over 10 gigawatts of electricity.

That’s enough to power over 7 million homes.

In today’s energy world, people and organizations are rethinking the architecture of the power grid.

So why not consider hydropower? If small solar farms and rooftop installations can add to the economics of producing green solar power, why can’t small hydro turbine generators do the same?

While hydropower plants are often thought of being very large, not all are.

Mini and micro hydro

Until the beginning of the 21st century, mini hydros (between 100 and 2,000 kilowatts) and micro hydro (up to 100 kilowatts) were not very common in the United States. Mini and micro hydro turbines were mostly found in remote areas supporting very small power demands.

Today the expansion of green energy markets and decentralized grid concepts have stirred a rebirth in the hydro turbine market, particularly the small installations.

Inventors and engineers are working on improving the mini and micro hydro turbine-generator with innovative designs and applications. These same people are looking at ways to harness ocean currents and tidal flows.

Small dams at mill ponds aren’t typically high enough to install hydro turbines. For the mini and micro hydro turbine projects, investors are looking at sustained output with the infrastructure that already exists.

They are simply trying to add to the pool of renewable power available for everyone to use, much like solar. Using new designs of hydro turbines that are available today can utilize the existing mill pond era infrastructure.

New thinking dedicated to innovative water-wheel designs, the use of composite materials, and the use of 3-D printing are all making these smaller machines more economical and competitive with solar and wind power.

The environmental impact small hydro turbines have at a mill pond is often very small to non-existent.

Archimedes’ screw

In a small town in Connecticut, the utility elected to install a hydro turbine called an Archimedes’ screw at the town’s mill pond. The Archimedes’ screw was originally designed between 3 and 5 B.C. to lift water from a lower elevation to a higher elevation.

Believe it or not, this ancient machine can also serve as a hydro turbine.

Archimedes screw

It consists of a ramp-like device that is attached to the downstream side of a dam with a small building at the top. The weight of the water quietly presses the screw causing it to turn. The rotating screw drives a generator in the building.

Because of the slow speed nature of the Archimedes’ screw, it turns out to be fish-friendly and environmentally conscientious.

Cross-flow hydro turbines

Recently, a variant to an old design known as the cross-flow hydro turbine, entered the market, called the hydroEngine™.

Water is directed at blades that are attached to a conveyor-belt-like apparatus. The force of the water hitting the blades causes the belt to rotate.

The belt is connected to an electric generator that can deliver 500 kilowatts of usable electric power. This can be accomplished with a water height of only 20 feet.

The hydroEngine™ is a compact design that does not need a lot of space and can easily be housed in a small building, like an old mill building, at the base of a dam.

Volturnus pod

Another new micro turbine design is called the “Voluturnus” pod (V-Pod) . The V-Pod simply sits in a fast flowing stream bed, a flowing channel or on a river bottom.

The nose of the V-Pod forces water to naturally flow towards the water-wheel blades causing them to rotate smoothly. A simple generator is incorporated into the 3-D printed housing.

Like solar panels, these 10-foot diameter, 3-foot high devices are intended to be interconnected.

With sufficient water flow, each V-Pod is expected to generate 10 kilowatts of electric power and can currently be interconnected to supply 50 kilowatts. For existing dams, it is possible that they can be placed directly into the spillways.

Energy storage

Hydropower can also be used to create an energy storage center. Many people think of energy storage as a big room filled with special batteries.

Hydropower has been serving the nation’s power grids as an energy storage center for years. Some utilities have been using power that is generated during off-peak or low-demand periods from nuclear power plants to run pump-storage hydropower plants in the pump mode.

In the pump mode, water is drawn from a large water source or a river, and pumped to an elevated storage reservoir. When electric demands increase or if there is a drop in other power generation sources, the stored water is allowed to flow back down to the turbines to generate electricity.

With the surge in solar and wind energy, the excess power from these two sources can be used to make pump-storage economical and contribute to the stability of the national power grid.

One of the greatest advantages of hydropower is its flexibility as an energy source. When water is available in an area that wants to be more sustainable and environmentally friendly with its power use, hydropower can be included in making the goal a reality.

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© 2016 The Hartford Steam Boiler Inspection and Insurance Company. All rights reserved. This article is intended for information purposes only. HSB makes no warranties or representations as to the accuracy or completeness of the content of this article.

Edward J. Paprocki

Principal Engineer in Hartford Steam Boiler’s Engineering Group, with over 32 years of experience in equipment maintenance.

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