In 1885 Aspen became the first city in the West to light streets and businesses with hydroelectric power. This continued until 1958 when coal fired electricity became less expensive. 

Hydropower is electric power made from moving water. When water turns the blades of the turbine, if connected to an electrical generator, it produces electricity. The pressure of the water can be measured as “head.”  The more head, the more electricity. Water then flows back into the river. 

Hydropower contributes the greatest share of renewable energy generated in the US.  The majority of this comes from large dams. A reservoir lake is created when water backs up behind a dam. This increases the head, or pressure derived from the flow of water that drains through the dam, which in turn creates more power. The Army Corp of Engineers estimates that there are 75,000 dams larger than 6 feet tall in the United States.  According to the National Hydropower Association, 3% of these are currently in use. 

Historically, large dams have caused great stress on rivers. They significantly disrupt normal flow. Large hydro projects have driven numerous fish species to extinction. Though hydropower does not release carbon dioxide emissions, its other impacts worry those who advocate for the environment. Dams block the essential flow of nutrients, plants, fish and animals. Dams can cause temperature swings that harm species, and can decrease oxygen in the water.  Fortunately, you don’t have to build a dam to harness hydropower!

It’s possible to develop Low Impact Hydro projects.  Placing a turbine in the flow of the river is one alternative. In 2012 ACES installed a 5KW microhydro turbine in a stream at Toklat. It has no dam, returns all water to the river, and ensures safe passage for fish. Our project supplies a little more than the electrical needs of an average home. 

Typically, microhydro projects go in conduits, irrigation ditches, or existing pipelines and have little impact. A note on vocabulary: small hydropower and micro are not the same. Small is a reference to the kilowatt capacity, and not the scale of the infrastructure nor its environmental impacts. 

Though hydropower does not emit CO2, it can hurt rivers and fish. This illustrates why reaching a good decision about energy development asks us to analyze many different factors.