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Assessing the Evacuated Tube tube module from F-chart are given in and Talkeetna. This is done to give a Collector for Domestic Hot Water      fairly good perspective on how these (DHW) Heating used for the performance is that obtained collectors will perform in the major from the Beijing Sunda company’s model population areas of Alaska. Since perfor- Since the last revision of this manual, Seido 2-16, and is taken from company         evacuated tube type collector arrays have literature. This is the same company that performance for these locations, similar come on the market and are now in use made the collectors shown in Figure 3-7 extrapolations are reasonable for rural in Alaska. Figure 3-7 is an example of a Alaska locations. The Comparative Notes system installed off the deck of a house (below). at the bottom of each of the tables are in the Nome area of Alaska. To assess the performance of evacu- used to give more precise and important To assess their performance in Alaska,      Factors that impact 2 detailed assessment and interpretations several test runs using the evacuated ft of effective tube area and the Sunda your payback Will solar thermal for me?    of the results of these runs. UNIVERSITY OF ALASKA FAIRBANKS Anchorage, Mer- rill Field data, as Tax incentives — Current tax Solar thermalshown in Table can be viable breaks offset the capital costs of if it can beAC-41. designed The col and- installed Alaska Center for and Power installing solar thermal systems. appropriately.lector Newand sys computer- simulation tem details used Preliminary studies using 2011 tax programsfor allow that Anchordesigners- to inexpensively credits indicate these savings should evaluate variousage run, anddesign all options quickly. always reduce the payback to less To determinethe subsequent if a solar thermal system is Collector evacuated tube than 10 years. right for runs,you, area number shown of factors need to Solar Thermal Tilt Angle be consideredin Tables. AC-41a and AC-41b. A Plumbing — In addition to the cost Collector tabular perfor- Solar Elevation Tilt of the collectors, there is the cost of Does it makemance financial report sense? If Angle Angle installing either a solar water heater economicssimilar are an to important the factor in Energy previous flat or a new double-coil hot water tank. your decisionplate collectorto use solar thermal or Specialized plumbing and controllersFigure 3-7. The Sunda evacuated tube collector system atany Matt alternative reports energy,is then your financial Figure 3-8. Collector tilt angle in relation to the ground surface and the Figure 3-9. An illustration of what is meant The Sunda evacuated tube collector Collectorsolar tilt elevation is optimum angle. Collector when tilt is optimum the sum when the sum by the azimuth of a collector. Any Erickson’s home in Nome shown on a grand solar day in given for the lo- of the collector tilt angle and the solar elevation angle (at noon) nonsouth orientation will reduce are also necessary and will affect the investment should be considered. of the collector tilt angle and the solar        system at Matt Erickson’s home in cations of Fair- for Alaska equals 90°, indicating the maximum solar intensity possible the total daily solar radiation cost of installation depending on Nome shown on a grand solar day in Because of cold weather and limited elevationat noon angle on the (at collector noon) surface. equals This optimum 90°, tilt changes gain in proportion to the azimuth of bright snow, no doubt enhancing the performance of banks, Homer, daily, so an annual optimum tilt must be selected if collectors angle. The largest theoretical indicating the maximum solar inten- how easy it is to integrate them into this array.April 2008. Cooperative Extension Service photo sunlight Kodiak,during Palmer,parts of the year, a solar are not movable. sum of total daily radiation will sity possible at noon on the collector fall on a surface that faces due south. your existing plumbing system. thermal system will not completely surface. This optimum tilt changes 79 daily, so an annual optimum tilt must be displace the need for heating oil, but it can provide nearly 100% of the hot 84 Durability — These systems have water needs of a house during optimal conditions. selected if collectors are not movable. proven durable even in rural Alaska. Once they are installed, little or Payback period no maintenance is required under typical circumstances. However, One way to analyze the economics of a system is to determine your payback Flat-panel collectors in Fairbanks draw in power. Notice the PV power panel for the pump on the solar system. You can hear it running quietly from indoors. Cooperative care must be taken to ensure that period, which is the number of years it takes for your cost savings to pay Extension Service photo potential damage is mitigated. for the expenses of running your system. To estimate your payback, identify Harnessing the energy your current heating costs, then define the amount of that bill you can olar thermal technology (or active solar ) transforms Your heating “load” — Since solar realistically expect to offset with your system. This can be estimated best radiation from the into usable heat, while solar photovoltaic potential of Alaska’s will only be available with a professional assessment of your annual available light, location of technology uses traditional solar panels to create . during a portion of the year due to your collectors and the efficiency of your chosen system. The resulting S natural resources. the lack of sunlight or bad weather, number is your annual savings. Subtract the annual additional costs it is wise to estimate your heating to operate and maintain your solar thermal system for your annual system Modern solar thermal technology has been in use for well over 100 years requirements for those months to savings. Next, identify the initial cost to design, purchase and install your in hot, arid climates around the world, including the American Southwest, Oil determine if the technology will system. Divide this number by your annual system savings for your payback Australia and Israel. Innovations in solar thermal systems have allowed the meet enough of your heating needs period. technology to expand across nearly every latitude below the Arctic Circle. In Gas to justify the costs. Initial system cost addition, recent tax credits have also added to the economic appeal of solar = Payback Annual system savings water heating in the . Despite low levels of light during some Geothermal parts of the year, rising heating oil prices, tax incentives and new innovations Kotzebue Annual fuel savings = Current heating costs minus in technology have now made a viable technology for Wind estimated cost of fuel offset use in arctic communities. with solar thermal system Water One of the challenges with using photovoltaic solar collectors in northern Fairbanks For more information about solar thermal systems in Alaska, please climates, especially high latitudes, is that the peak energy use comes during Biofuels refer to the A Solar Design Manual for Alaska by UAF Cooperative the cold, dark winters, when is relatively unavailable. However, Extension Service Community Sustainability Coordinator Richard the summer months in arctic Alaska bring 24 hours of sunlight, warm Seifert. To order, call Extension at 1-877-520-5211. temperatures and mild weather. This is an optimal environment for solar thermal . Heat derived from these systems can be used to meet domestic hot water demands, which remain fairly constant throughout the year, or supplement low-grade heating requirements sometimes UNIVERSITY OF necessary during arctic summers. ALASKA FAIRBANKS

The University of Alaska Fairbanks is accredited by the Northwest Commission on Colleges and Universities. UAF is an affirmative action/equal opportunity employer and educational institution. Schematic of a typical active solar domestic water heating system An Alaska Case Study: Kotzebue Auxiliary Heater Solar Radiation To Load Kotzebue’s location above the Arctic Circle would typically be considered a challenging environment for a solar thermal system. However, with $6-a-gallon heating oil, nearly 24 hours of sunlight during the summer months and recent advancements in solar thermal technology, opportunity for solar thermal systems in the Storage Tank Heat Solar Exchanger Arctic is growing. Collector In December 2010, Kotzebue Electric Association, working with ABS Alaska and Susitna Energy Systems, installed six solar thermal systems in volunteer houses around Kotzebue. Both evacuated-tube and flat- Water From panel collectors were installed in various configurations to allow for a rigorous assessment of performance. Main at 400 F An engineer checks on a nearly This project, funded through the Denali Commission Emerging Grant program, seeks complete solar hot water installation. Cooperative Extension Service photo to investigate the effectiveness of solar thermal technology in arctic conditions. The Alaska Center for Figure 3-6. Schematic of a typical active solar domestic water heating system. Energy and Power is providing technical assistance for data collection and analysis. Current estimates for Alaska indicate that solar energy advantages and disadvantages for installation in Alaska 55 can provide 40 to 60% of the hot water load on an that should be considered before purchasing. It is believed that the systems will prove to be an economical, environmentally friendly way to displace annual basis. A number of successful solar thermal heating oil in the community. All systems began registering BTUs as of March 2011. The systems are still systems have been installed in Anchorage and the Kenai Flat panel (plate) — These collectors are easy to relatively new, but in the first four months, the six volunteer houses are enjoying hot water heated by the Peninsula. Systems farther north in Denali, Fairbanks, install, will melt snow off the face of the panel and can sun with minimal maintenance on the Nome and Kotzebue have been recently installed with be independently powered by a photovoltaic pump so if collectors. encouraging results. there is a power outage, the collector will not overheat the solar fluid. Installers in rural or remote Alaska also This project will run through How is solar thermal energy collected? report that the flat panel (plate) is easier to transport September 2012 and will be followed without breaking, even by snowmachine, and is easier to by a technical and economic analysis. Currently there are two primary ways to directly gather fix if it breaks or has leaks. and store usable energy from the sun: solar thermal panels and solar photovoltaic panels. Photovoltaic solar Evacuated tube — While these collectors are more panels transform radiation into electricity. Solar thermal complex and more difficult to install, they have panels transfer the energy into a fluid, from which it is advantages over flat-panel collectors. Transport to then extracted for heating purposes. remote locations can result in breakage. However, since the evacuated tubes are connected in series, the collector can continue working even if some of the A flat-panel collector in Kotzebue tests the feasibility of solar in the Solar thermal systems can most easily be used to provide Arctic. energy for use in meeting hot water needs. Since a tubes are broken. One of the biggest disadvantages of significant amount of home energy is used to heat hot installing an evacuated-tube collector in Alaska is that water, solar thermal systems are an attractive option snow will not melt off the collector because it does not colder parts of winter, it does well in summer, so that Alaska homeowner because the heat-exchanging for many homeowners. Systems can also be designed release heat back into the atmosphere. Therefore, these the difference is not significant. With both systems, it is fluid allows the system to generate usable heat at to utilize any additional heat generated to supplement collectors require constant maintenance and should crucial to install collectors vertically (90 degrees). This lower temperatures and, therefore, operate at a space-heating requirements. be installed in a location that is easy to access. An also mitigates the snow buildup issue. higher efficiency. easy solution to this issue is to install evacuated tubes Two types of solar collectors may be installed, a flat- vertically or under an eave to prevent being covered There are two primary types of systems and • Direct systems — Water is heated directly by solar collector (also called “flat plate”) and an by snow. This is important for all collectors in Alaska configurations: radiation and then transported to where it will be evacuated-tube solar collector. Both collectors have situations. • Indirect systems — Instead of domestic hot used. This type of system is strongly discouraged water directly heated by the solar panel, a fluid in Alaska, where the recommendation is to The annual sum of solar energy collected from a flat- flows through the solar panels and the heat is never circulate liquid water outside of the heated plate system and an evacuated-tube system of very transferred to the domestic hot water through shell of the building. See pages 22-23 of the similar size is nearly the same. While the flat-plate a heat exchanger. These systems can use either Cooperative Extension A Solar Design Manual for system is not as good at collecting solar energy in the flat panels or evacuated tubes. Indirect systems Alaska for more details. are typically considered the most beneficial to an

For more information: www.uaf.edu/acep Alaska Center for Energy and Power: Fostering development of innovative solutions to Alaska’s energy challenges through applied energy research at the University of Alaska