Cold climate limits hydro-power in Alaska
Despite Alaska has large oil and gas resources, electricity, gasoline, and heating oil are rather expensive. Thus, it is not surprising that alternative energy resources are widely used. Given that Alaska has many rivers hydroelectric-power comes into mind. Yes, there exist many hydro-power facilities in Alaska. Indeed hydro-power is Alaska’s largest renewable energy source providing about 21% of Alaska’s electrical energy on average. Nevertheless, the electricity bills of customers with access to electricity from hydro-power are quite high.
In a post earlier this year, I explained why electricity from fossil fuel is more expensive in the Last Frontier than in the Lower 48. Today’s Focus Alaska addresses why electricity is expensive despite of hydro-electrical power.
Why is from hydro-electricity expensive in Alaska?
Alaska has glacier-fed and rain-fed rivers. The Panhandle (Southeast Alaska), which is the area adjacent to British Columbia, receives about 155.08 inch (3939 mm) in Yakutat and 225 inch (5715 mm) in Little Port Walter on Baranof Island south-southeast of Sitka (86.72 inch; 2203 mm) of annual precipitation on average, in the north and south, respectively. In Glacier Bay National Park at Bartlett Cove, annual mean precipitation amounts 70 inch (1778 mm). Everyone, who had visited Glacier Bay on a cruise ship on a rainy day, had the impression this amount purred down all at once on the day of their visit.
No wonder. The Coastal Mountains lift moisture-loaded maritime air thereby enhancing precipitation. The steady precipitation and cool temperatures provide the right conditions for a temperate coastal rain-forest, the Tongass National Forest. In this region, precipitation occurs year round and is more or less equally distributed over the year. This means rain-fed rivers would have low variations in flow. However, in this regions most rivers are glacier-fed. Thus, runoff is higher during summer than winter. In the warm season, the glaciers provide more water to the rivers than they do in the cold season.
Glaciers provide water even at temperatures below freezing
The high weight of the ice and snow accumulated in a glacier leads to high pressure. Thus, ice melts at below freezing temperatures at the rock-glacier interface and runs off. In the warm season, above zero air temperatures contribute to water loss of the ice mass.
The peak demand is offset with the peak of hydro-power availability
Once fall arrives, temperatures go down and so does the glacier runoff. At the same time, daylight hours get shorter as compared to summer. People stay inside more time than during summer and use electrical equipment for entertainment. Thus, energy demand goes up. The reduced river runoff means that the hydro-power plant generates less power than it did in summer. Traditional oil, coal, and/or gas power plants have to make up for the gap from reduced water flow and also from the increased demand. However, these energy sources are expensive for the reasons presented in my first post on energy costs in Alaska.
North of 60 rivers freeze-up in winter
Farther north than the Panhandle, rivers freeze in winter. The ice is often more than 3 ft (1 m) thick. The Tanana River, for instance, freezes about 40 inch deep at Nenana. Note that here the ice depth is determined by drilling wholes into the ice between mid January and mid April for the Nenana Ice Classics, Alaska’s only lottery. The data serves Alaskans to guess/bet on the time of breakup.
Icing is a problem
The annual freezing of rivers is an issue for hydro-power generation. Water will freeze on the super-cooled equipment. Of course, the ice on the rivers acts as a lid. Thus, any precipitation is stored on top of the ice and does not contribute to the flow until breakup. This means that during winter runoff is low and fed by ground water only for rain-fed rivers, and glacier-water and ground-water for glacier-fed rivers.
Typically rivers are totally frozen in November in the Interior. On the North Slope, rivers freeze earlier. Here, the Sun stays below the horizon from end of November to mid January. Thus, availability of energy from hydro-power and energy demand are even more offset than in the South.
Batteries experience drain/freeze
Storing of hydro-power generated energy in batteries comes to mind. However, in the frigid cold environment with temperatures in the double digits below zero mean a huge drain on the batteries and energy loss. Furthermore, batteries freeze easily in the sub-zero temperature environment. Not to mention that many huge batteries would be needed to keep the energy going even of a small town like Nome (about 3,797 inhabitants in 2016).
Despite hydro-power generation has its limits and serious short-comings, there exists plans to build a dam on the Susitna-river for hydro-power production. Some Alaskans argue against this planned project due to the salmon run that will be disrupted by a dam. Others are concerned about the ecosystems that will be destroyed when the valley is flooded. In addition, it is argued that the area is prone to earthquakes. Earthquakes might endanger the dam. To reduce the risk of the dam’s breaking during an earthquake the costs for constructions would be much higher than for dams built in another non-earthquake prone region. However, to protect the people downstream of the dam from a dam break and drowning, the dam has to be built earthquake proof. Consequently, the costs for electricity generated by means of the hydro-dam will go up. It is argued that the energy costs could be even higher than those for fossil-fuel-generated power – even when the oil price is low.
Land-use related concerns
As you know I wrote a book on Land‑Use and Land‑Cover Changes: Impact on Climate and Air Quality. There is another thing about building this dam related to the change in land-cover. The dam would mean a large water surface where the land-cover had been vegetation before. The water surface reflects the Sun’s radiation less than does vegetation. Furthermore, the water stores the Sun’s energy stronger than the soil does. Consequently, near-surface air temperatures would remain higher at night in summer than they do for a vegetation covered surface. The local temperatures around the water reservoir would be slightly higher than before.
Later in fall, the artificial lake would release the heat stored in the water body during summer. Consequently, near-surface air temperatures remain higher along the lake in fall than they would be without the presence of the water reservoir. Thus, soils would freeze later and onset of snow would occur later too.
In winter, ice forms on the water reservoir and snow accumulates on top. The snow reflects the sunlight very strongly. Thus, near-surface temperature would be lower than with the darker spruce trees, shrubs and trees that had been there prior to the dam. Cold air would form over the snow-covered ice. It is well know that at same pressure, cold air is heavier than warm air. Once the cold air dome is high enough that it exceeds the height of the dam, the cold air drains down into the valley behind the dam and down the river valley. Thus, the downstream villages would get this cold air as the heavy cold air would move underneath the relatively warmer air. An inversion forms. This means now air temperatures are lower at the bottom of the valley than in the air aloft in the valley. Any emission from domestic heating to traffic would accumulated in this surface inversion. Over time air quality would degrade until a storm swipes the inversion and contaminants out of the valley.
In spring, solar radiation first goes into melting of the snow and ice on the lake. Once the water is ice- and snow-free, heating of the water sets on in the reservoir. Thus, the environment of the lake would remain cooler than it was when there was still vegetation and soil. Green-up will be later than it used to be.
In summary, the vegetation season would shift to later green-up and a later end, and the quality of life would be reduced at least in winter due to colder conditions and poor air quality. The latter can cause health-adverse effects especially for kids, elderly people pregnant women, and people with preexisting heart and lung diseases.
Permafrost can increase construction costs
As if these difficulties weren’t enough, there is also discontinuous permafrost. I wrote a post how permafrost can affect construction in the post at the link. Furthermore, the groundwater flows underneath permafrost are not well understood and known. Thus, construction of a dam is a challenging task and may bear costly surprises. This means the costs for the project may become higher than planned. You can read about the impact of permafrost on groundwater and the formation of artesian wells due to permafrost at the links.
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