Alternative Energy Options (for Seward)
Because many types of renewable energy resources are developed and utilized locally, Alaska’s lack of energy infrastructure makes renewable energy an ideal means by which communities can generate stably-priced, environmentally responsible energy.
Geothermal is a general term describing the heat generated and contained within the earth. Over 90% of the total volume of the earth has a temperature exceeding 1000°F, and only a small amount of this heat gets close enough to the earth’s surface to be utilized by conventional technology and be considered an energy resource. When it does, the elevated heat manifests itself in uncommon geologic occurrences like lava flows and volcanic eruptions, steam vents or geysers, hot springs, or elevated geothermal gradients creating hot rock. In normal geologic situations, the majority of the heat slowly dissipates into the atmosphere by unseen heat transfer processes known as conduction, convection, and radiation.
At the surface of the earth, heat can also be gained from the sun during daylight hours. The sun, especially during the summer months, can heat to depths of 100 feet. When ground source heat pumps are used for heating buildings, the energy may come from either solar or geothermal sources. Below a depth of several tens of feet, any heat recovered from the earth will usually be geothermal in origin. Geothermal heat comes from two main sources: the original heat of the earth generated at its formation about 4.5 billion years ago and the more recent decay of the radioactive isotopes of potassium, uranium, and thorium.
Geothermal resources are found on all continents and have been used for a wide variety of purposes, ranging from balneology (the science of soaking in hot springs or hot mud baths) to industrial or direct use processes such as space heating, from process heat for drying things like fish or lumber to electrical power generation. Industrial uses require temperatures ranging from 150°F to around 300°F. For large-scale electrical power generation, (measured in megawatts or millions of watts) temperatures in the neighborhood of 300°F to 650°F are needed. In Alaska with its cold climate and abundant cold water resources it is possible to use much lower geothermal temperatures for small-scale electrical power generation.
Geothermal power is cost effective, reliable, sustainable, and environmentally friendly, but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.
Ground source heat pump (GSHP) systems are a feasible use of geothermal energy that is available in Seward. The electrically powered systems tap the relatively constant temperature of surrounding earth or water bodies to provide heating and cooling. More than 50,000 of these systems are installed in the US each year. In Alaska, heat pump systems are used for space heating homes commercial buildings and public facilities. Several local residents from Seward and neighboring communities have installed GSHP systems in their homes or for their businesses. The Juneau Airport GSHP, in operation since 2011, has saved an estimated $190,000 in displaced diesel fuel. GSHP systems are most applicable in areas with low electric rates and high heating costs. Geotechnical conditions like permafrost are also a factor.
Solar energy uses radiation from the sun for heating or electricity generation. “Passive” solar heating utilizes building design and construction to minimize the use of heating fuel. Passive solar design employs windows, thermal mass, and proper insulation to enable a building itself to function as a solar collector. For example, by orienting windows to the south, the sun’s energy is transferred into the building through natural processes of conduction, convection, and radiation. “Active” solar heating systems use pumps or fans to circulate heat (water or air) to a point of use, such as a domestic hot water tank. Solar water heaters use the sun to heat either water or a heat-transfer fluid in the collector. Heated water is then held in the storage tank ready for use, with a conventional system providing additional heating as necessary. Indirect-circulation systems are the best type of water heating system for Alaska. They work by pumping an intermediary heat-transfer fluid through the solar collectors, which then circulates through a heat exchanger and warms the potable hot water held in a tank. In warmer climates, the water is pumped directly through the solar collectors without an intermediary fluid. Despite short winter days, solar water heaters can be used about 9 months out of the year in Alaska, making them one of the most practical applications of solar energy for domestic use.
Photovoltaic (PV), or solar-electric panels, are used to generate electricity from the sun. They are commonly used to power homes or communities that are “off the grid”, or not connected to an electric utility’s power grid. Increased worldwide demand and larger scale production of panel components have cut solar panel costs by 80% over the last five years. Another emerging technology in solar electricity generation is concentrated solar power, which uses mirrors to concentrate sunlight onto receivers that collect the solar energy and heat thermal oil. That thermal energy is then used to produce electricity via a heat exchanger that vaporizes water to drive a steam turbine.
Solar Energy in Alaska
Although Alaska’s northern location presents the challenge of having minimal solar energy during the long winter when energy demand is greatest, solar energy fulfills an important role in space heating and off-grid power generation. The largest amount of solar-electric generation in Alaska comes from the Golden Valley Electric Association’s Sustainable Natural Alternatives Program (SNAP). Members of the electrical coop install their own renewable energy producing systems, the vast majority of which are solar. Non-producing members can choose to donate to an escrow account to support such renewable energy development. The donations are used to pay the producers of the renewable energy. Launched in 2005, the SNAP program is available to systems with a generation capacity of 25 kW or less. GVEA also operates a solar thermal hot water heating system at the Denali Education Center in Denali National Park. The project consists of 36 flat panel solar thermal collectors that offset electricity and propane required to heat water for 13 cabins and other buildings at the facility, saving Denali Education Center about $7,000 annually. To date this is the only solar thermal project funded through the Alaska Renewable Energy Fund.
In addition to solar thermal, some Alaskan communities are starting to incorporate solar PV to offset their fuel consumption. In 2012 Alaska Village Electric Cooperative installed a 10kW solar PV system in the village of Kaltag (pop. 190) to reduce the community’s use of diesel fuel at the local powerhouse. In its first year of operation the solar array produced about 8,200 kWh, saving Kaltag residents over $1,700 in diesel fuel for FY13. To date this is the only solar PV system that has been funded through the Alaska Renewable Energy Fund.
Wind is caused by temperature and pressure fluctuations in the atmosphere as the sun warms the earth. Alaska’s wind resources are abundant, especially on the western coastal regions of the state.
Wind devices are powered by air. Air moving relative to an object such as the blades of a wind turbine (or the wings of a plane) imparts a force on that object.
Wind turbines use this aerodynamic force to convert the kinetic energy of the wind into mechanical energy that can be harnessed for use. The energy in the wind can be defined for a specific unit of area that the wind is flowing through in a unit of time. Wind energy is directly related to the area swept by the turbine blades, air density, and the cube of wind speed. A doubling of the wind speed increases the power from the wind by eight times. For this reason, the most important factor in calculating wind power is determining wind speed. This fact is important when considering the integration of wind into existing power systems. In most instances we need our power to be constant, and wind energy is as variable as the blowing wind.
How Wind Energy Works
A wind turbine generator (WTG) uses a wind turbine rotor, with turbine blades to transform wind energy into mechanical energy; and a generator, to transforms that mechanical energy into electrical energy. Many different types of wind turbines are available. Sizes vary. Small (10 kW or less) wind turbines which are typically used for individual homes or small businesses. Medium-sized (50kW – 1000kW) ones are used for remote communities and other grid-connected, distributed generation. Large turbines (1MW or more) are generally used in large wind farms.
This section focuses on medium and large wind turbines without addressing the application of small wind turbines. More information on small wind turbine applications can be found on the Wind Powering America small wind website, or the Alaska Energy Authority website. Various publications like Wind Power: Renewable Energy for Home, Farm, and Business, by Paul Gipe (2004), might also be helpful.
Bioenergy is a collective term for renewable energy made from the organic material of recently deceased plants or animals. Sources of bioenergy are called “biomass” and include agricultural and forestry residues, municipal solid wastes, industrial wastes, and terrestrial and aquatic crops grown solely for energy purposes. Bioenergy includes the generation of energy from biological sources such as landfill gas and the combustion of organic fuels to produce electricity or heat. Although oil and natural gas are energy sources derived from deceased plants and animals, they are not considered biomass because their organic material has not been a part of the carbon cycle for millions of years.
Biomass is an attractive petroleum alternative because, developed responsibly, it is a renewable resource that is more evenly distributed over the Earth’s surface than finite energy sources, and may be exploited using more environmentally friendly technologies. It is also considered “carbon neutral,” meaning the carbon absorbed during the lifespan of the organisms from which it was created counters the carbon released by the combustion of the biofuel. Today, biomass resources are used to generate electricity and power and to produce liquid transportation fuels, such as ethanol and biodiesel. Ethanol is the most widely used biofuel. Currently, a majority of ethanol in the United States is made from corn, but new technologies are being developed to make cellulosic ethanol from a wide range of agricultural and forestry resources, including organic waste byproducts such as sawdust or cornhusks. In Alaska, primary biomass fuels are wood, sawmill wastes, fish byproducts, and municipal waste, though there is also some potential to grow energy crops such as canola for biofuel development.
Water constantly cycles through a vast global system, evaporating from lakes and oceans, forming clouds, precipitating as rain or snow, then flowing back down to the ocean. The energy of this water cycle, which is driven by the sun, can be tapped to produce electricity or for mechanical tasks like grinding grain. Hydropower uses a fuel, water, that is not reduced or used up in the process. Because the water cycle is an endless, constantly recharging system, hydropower is considered a renewable energy resource.
When flowing water is captured and turned into electricity, it is called hydroelectric power or hydropower. There are several types of hydroelectric facilities, all powered by the kinetic energy of flowing water as it moves downstream. Turbines and generators convert the energy into electricity, which is then fed into the electrical grid to be used by homes, businesses and industry. Impoundment hydroelectric facilities use a dam to store river water in a reservoir and control the amount of electricity being produced by regulating the flow of water through the penstock (which carries water to the turbines). Diversion facilities channel a portion of the river’s water through a canal or penstock, often without the use of a dam. The Tazimina project in Alaska is an example of a diversion hydropower plant. Pumped storage plants act like impoundment facilities during high load hours, but use extra energy produced during periods of low demand to pump water from a lower reservoir to an upper reservoir. Hydroelectric facilities range in size from large power plants (more than 30 MW capacity) that supply many consumers with electricity to small (100 kW to 30 MW capacity) and microhydro systems (up to 100 kW capacity) that individuals operate for their own energy needs, or for sale to utilities.
Seawater heat pumps are water-to-water heat pumps that operate by using electric compressors in combination with the physical properties of an evaporating and condensing fluid known as a refrigerant. The specific heat pump equipment required for this process is not an “off the shelf” or conventional heat pump; it must use a wider heat range to tap into colder temperatures. While conventional heat pumps are typically lifting heat from 45-55°F water sources, seawater heat pumps are lifting heat from much lower temperatures, requiring more innovative compressor technology.
While this technology has been successfully deployed in Europe, this innovative process of removing latent heat from seawater and using it to heat buildings is an emerging technology in Alaska; and the Alaska SeaLife Center is the first installation utilizing this technology in the state.
The basic concept of sea water-generated heat pump system comes from a leading example at the Alaska Sealife Center installed and that has been successfully operating since 2013. How it works is that the raw sea water comes into the system from an intake pipe that is positioned into Resurrection Bay which provides water at temperatures ranging from 38F to 55F. It is pumped through a heat exchanger containing 90 percent fresh water and 10 percent propylene glycol, a vegetable-based antifreeze in common use in commercial and residential heating systems. Then the water is pumped through an electric powered compressor, where it is further heated to 120F, and finally it goes through looped pipes to heat the facility and its outdoor pavements.