Introduction
Alaska has enjoyed a long and rich history with hydroelectric power. By 1908, southeast Alaska alone had over 30 developed water power sites with a capacity of 11,500 kW. The vast majority, built by private developers, provided power for industrial operations, mainly for the gold mining works in Juneau and on Douglas Island. Today hydropower in Alaska provides 24%1 of the statewide electrical power. Major developers include the State of Alaska and public and privately owned utilities. These power plants have proven to be long-term, reliable, and relatively inexpensive sources of power. Hydropower installations have the reputation for being robust and durable, operating successfully at some sites for more than a century. Hydropower’s low operation and maintenance costs coupled with long lifetimes result in stable power rates. In Alaska, hydropower is currently the largest and most important producer of electricity from a renewable energy source. With increased interest in replacing fossil-fuel-powered generation with renewable energy resources, the statewide inventory of installed hydropower capacity will continue to expand.
Typical High-Wall Reservoir Hydroelectric Dam Structure.
Source: Army Corp of Engineers
How Does Hydroelectric Power Work?
Hydroelectric power uses the gravitational force of water falling falling or flowing water to generate electricity. Most hydroelectric power comes through the use of dams: the potential energy of dammed water drives a water turbine and generator. The power that is generated at a hydroelectric facility depends upon the volume of water moving through the dam and the height difference between the water's source and outflow.
Hydroelectric Power in Alaska
A list of the larger facilities serving utilities opens by clicking below.
In Southcentral Alaska, the Eklutna hydroelectric facility was brought on line in 1955 by the federal government. In 1994 it was taken over by Anchorage Municipal Light & Power. As the cheapest energy source connected to the Railbelt energy grid, it currently produces power at a rate of a few cents per kWh.
The Cooper Lake hydroelectric facility is owned and operated by Chugach Electric Association. It began operation in 1960 and was recently relicensed by the Federal Energy Regulatory Commission. A number of smaller hydroelectric projects owned by individual utilities are located across the state, mostly in Southeast Alaska. There are also some very small private facilities, most of which are owned by fish processors.
Challenges of Hydroelectric Power
Impoundment hydroelectric projects are some of the cheapest and largest producing forms of renewable energy; however, they can have serious damaging impacts on the surround environment, oftentimes making smaller "run-of-the-river" projects more attractive. Although these smaller devices produce less electricity, they can be less detrimental to salmon runs and decrease likelihood of inundating riparian valleys.2
Among the effects that hydro projects can have on the ecosystem are the following:
- Stratification: occurs in reservoirs; colder, oxygen-depleted water discharged downstream
- Supersaturation: air becomes trapped in water spilled over a dam; levels of nitrogen increases, fish get something similar to “ the bends”
- Changing Water Levels and Flows: inundation of the resources and habitats; daily, weekly, or seasonal fluctuations due to “power peaking”
- Sedimentation: no longer providing important organic nutrients, inorganic material [silts, sands, and gravels], and habitat media to the downstream ecosystem; organic nutrients build up behind the dam, called “nutrient loading” results in oxygen levels decreasing in the reservoir; inorganic material [silts, sand, and gravel] not able to migrate downstream decrease the volume of the reservoir
- Erosion: increase in the amount of sedimentation; changing water levels and lack of shoreline vegetation of a reservoir increases the amount of sedimentation; increase flows due to discharge from dam or smaller channel sizes for bypass reach and downstream channel can also lead to removal of streamside vegetation. (Changes to the riparian zone directly impacts the species which it can support.))
- Flow Alterations: bypass reach (general reduction in flow, variations from natural flow cycles, dependent on power generation and demand); downstream reach (variation from natural flow cycles, increase in rates of flow changes due to power generation and demand along with shutdowns)
- Habitat Conditions: varies greatly from project to project; fish movement (resident fish: spawning, seasonal migration and spawning - Cutthroat trout in Juneau to Bull trout in Eastern Washington; Anadromous fish: in-migration, spawning, and out-migration - Pacific Salmon, Steelhead, and others); lack of streamside vegetation, cover for fish and other aquatic organisms3
Hydroelectric Technology
| TECHNOLOGY SNAPSHOT: HYDROELECTRIC | |
|---|---|
| Installed Capacity (Worldwide) | 654,000 MW |
| Installed Capacity (Alaska) | Approximately 423 MW |
| Resource Distribution | Resource potential exists throughout many areas of the state, with most developed projects in the southeast and southcentral portions of the state; Alaska has 40% of U.S. untapped hydropower (192 billion Kwh energy potential) |
| Number of communities / population impacted | 100+ (potentially +80% of Alaska’s population) |
| Technology Readiness | Commercial (mature) |
| Environmental Impact | Requires proper design to mitigate impacts to downstream aquatic life, downstream water quality, and recreational uses |
| Economic Status | Unit costs are variable and site specific. Where found to be economic, hydroelectric installations provide reliable, inexpensive renewable energy |
| Case Studies | Bradley Lake, Four Dam Pool, Southeast Alaska, South Fork Prince of Wales Island, New Hydro Projects |
| Wind Working Group | Recommendations, References |
| News | DOE Hydro News |
To learn more about hydroelectric technology, click on the link below:
HYDROELECTRIC TECHNOLOGY
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Resources and Links
- Alaska Energy Authority (AEA) has established a website about a new 600 MW hydroelectric project at Watana on the upper Susitna River: http://susitna-watanahydro.org/. From Petroleum News: "By feeding electrical power into the Alaska Railbelt power grid in sufficient quantity to meet around 50 percent of the Southcentral Alaska power demand, the state sees the Susitna-Watana hydropower system as a major contributor to achieving a statewide goal of obtaining 50 percent of power from renewable sources by 2025."
Hydro News
