Increasing energy security and reliability concerns are intensifying the interest in microgrids. In this setting, design optimization is vital to achieve a reliable infrastructure without overbuilding. This paper considers the impact of frequency and voltage regulation on the optimal design of a conceptual, autonomous military microgrid. This microgrid comprises a solar panel and vehicles as power sources, with each vehicle incorporating a battery and generator. The power output and terminal voltage of these inverter-based sources must be regulated. The paper investigates the effects of battery DC voltage variations on a decentralized regulation scheme, and the resulting influence on optimal component sizing. To this end, controllers are first designed based on the typical assumption that the voltage on the DC side of each inverter is constant. The battery internal resistance is then considered and its impact on regulation performance is investigated. The results show that the battery internal resistance can affect the performance of both frequency and voltage regulation, and consequently must be taken into account in component sizing decisions. Thus, the paper identifies an important coupling between regulation and component sizing problems through battery characteristics, and highlights the need for a combined sizing and regulation framework for microgrid design.

Optimal design of an electrical microgrid and sizing of its components seeks to balance capital investment with expected operational cost while meeting performance requirements. Calculating operational cost requires scheduling each microgrid component over some time period (dispatching) for each design evaluated. Heuristic or rule-based dispatch strategies typically consider only single time instances and are computationally efficient but do not include scheduling energy storage for future time periods. In this paper, we propose to optimize microgrid designs using forward-looking optimal dispatch for future energy storage planning. We present a case study of an ‘islanded’ military base microgrid with renewable and non-renewable electricity generation, battery storage, and plug-in vehicles with electrical export power capability. The optimal design and forward-looking dispatch strategy are compared to results obtained using the publicly available rule-based dispatch strategy in HOMER Energy software. Results show that the forward-looking strategy uses storage batteries to plan for future energy shortfalls rather than simply as a buffer for variable renewable energy supply, resulting in a 7.8% reduction in predicted fuel use. For the given cost assumptions, sensitivity analysis of the optimal design with respect to fuel price shows that investment in renewable energy technology is justified at prices greater than $5 per gallon ($1.32/liter) with an attendant reduction in fuel use of 3–30%.

Organic vapor jet printing with a print head comprised of a microfluidic Si nozzle array is used to deposit parallel lines of an organic semiconductor thin film with a line width of $16\mu \text{m}$ and edge resolution of $4\mu \text{m}$ . Line width and feature size are functions of process conditions, depending strongly on nozzle-to-substrate separation distance. Experimental results are accurately characterized by a direct simulation Monte Carlo model. The model suggests that feature sizes of $<1.5\mu \text{m}$ are attainable by this printing process. The ability of the print head to codeposit doped films is demonstrated by growing the emissive layer of a green phosphorescent organic light emitting diode sandwiched between hole and electron transport layers deposited by vacuum thermal evaporation. This device had an external quantum efficiency of $8.8\pm 1.3\mathrm{\%}$ , comparable to a similar device entirely grown by vacuum thermal evaporation.