This paper presents test results of a 50 kW Organic Rankine Cycle (ORC) system and proposed guidelines for how to effectively apply this system to the rural Alaska power industry. In rural Alaska, approximately 180 villages rely on off-grid diesel generators for power. Most of the generators have capacities of about 1 MW or less. In general, the average operation efficiencies are noticeably less than 40%, with the rest of the fuel energy becoming heat. If the heat is not applied for useful application, it is called waste heat. Most of the wasted heat is contained in engine exhaust and jacket fluid and eventually dissipates into the environment. For rural Alaska, waste heat for heating is most effective; in many cases, waste heat for power may be needed due to a variety of reasons. Many rural Alaskan villages are reluctant to apply exhaust heat recovery due to concerns about corrosion and soot accumulation in the exhaust system and their effect on emissions. Therefore, this work focuses on applying engine jacket fluid heat recovery for power generation; the potential for applying exhaust heat recovery is discussed only briefly.
For this project, heating and cooling systems serving as heat source and cooling sink, along with measurement instruments, have been installed in the ORC system. Measured data were analyzed to give system performance characteristics, which were then used to: generate a procedure to evaluate whether or not applying the ORC system can benefit individual rural villages; develop guidelines for how to effectively apply the ORC system to individual diesel generator sets; and estimate potential fuel savings from applying this system to the rural Alaska power industry. Along with these discussions, examples illustrate how to use the experimental results to match a generator to the ORC system based on expected payback period, and how to estimate the payback period for a selected village applying this ORC system.