Many Alaska communities rely on heating oil for heat and diesel fuel for electricity. For remote communities, fuel must be barged or flown in, leading to high costs. While renewable energy resources may be available, the variability of wind and solar energy limits the amount that can be used coincidentally without adequate storage. This study developed a decision-making method to evaluate beneficial matches between excess renewable generation and non-electric dispatchable loads, specifically heat loads such as space heating, water heating and treatment, and clothes drying in three partner communities. Hybrid Optimization Model for Multiple Electric Renewables (HOMER) Pro was used to model potential excess renewable generation based on current generation infrastructure, renewable resource data, and community load. The method then used these excess generation profiles to quantify how closely they align with modeled or actual heat loads, which have inherent thermal storage capacity. Of 236 possible combinations of solar and wind capacity investigated in the three communities, the best matches were seen between excess electricity from high-penetration wind generation and heat loads for clothes drying and space heating. The worst matches from this study were from low penetrations of solar (25% of peak load) with all heat loads.

Wood and coal cofiring holds great potential for reducing greenhouse gas emissions from grate-fired combustion systems, as well as being widely technically feasible. This research was among the first to evaluate CO and NO_x levels within grate-fired cofiring at small utility scales. We evaluated two wood fuel types—high-quality aspen chips and lower-quality pellet mill residues. Each wood fuel was evaluated at two cofiring rates. Over 6 days of testing, CO contents ranged from 40 to 620 ppm, and NO_x contents ranged from 82 to 145 ppm. We found statistically significant differences in CO content when comparing low versus high cofiring rates, with high cofiring having greater CO concentrations. Relatively high CO emissions were attributed to greater moisture within the combustion chamber at higher levels of wood. Combustion efficiency versus cofiring rate was generally modeled the best as a quadratic relationship; carbon monoxide content versus cofiring rate was best modeled linearly. There were very few changes in combustion efficiency, fuel handing, or plant operation at the utility scale when cofiring at up to 15 percent of the energy value (versus no cofiring). From an operational standpoint, cofiring was relatively easy to implement and well received by plant managers.