Characterizing Electric Grid System Benefits of MPC-Based Residential Load Shaping

Routinely encouraging and discouraging residential electric load throughout the day will be increasingly crit-ical in efficiently managing the smart grid to reliably de-liver clean, low-cost electricity. Yet, manipulating the duty cycles of thermostatically controlled loads such as heating, air conditioning, and hot water heaters can have the effect of destabilizing or stabilizing the grid. This work explores the potential for price-responsive control of residential air conditioning to shape electric demand at the distribution feeder level to minimize electricity production costs. Physical models of the interplay be-tween building thermal and electric loads are used to simulate time-series temperature and load behaviour. In-stantaneous load-adding and load-shedding opportuni-ties are quantified in more than 100,000 individual homes on 204 distribution feeders with results presented for 35 cities across the United States. In the context of distributed model predictive control, simulation of feeder-level response to a residential day-ahead 5-mi-nute pricing vector to 2,146 homes highlights an aggre-gate impact of flexible loads.</p

Empirical Investigations of the Opportunity Limits of Automatic Residential Electric Load Shaping

Residential electric load shaping is often implemented as infrequent, utility-initiated, short-duration deferral of peak demand through direct load control. In contrast, investigated herein is the potential for frequent, transactive, intraday, consumer-configurable load shaping for storage-capable thermostatically controlled electric loads (TCLs) including refrigerators, freezers, and hot water heaters. Unique to this study are 28 months of 15-minute-interval observations of usage in 101 homes in the Pacific Northwest United States that specify start, duration, and usage patterns of approximately 25 submetered loads per home. The magnitudes of the load shift from voluntarily-participating TCL appliances are aggregated to form hourly upper and lower load-shaping limits for the coordination of electrical generation, transmission, distribution, storage, and demand. Empirical data are statistically analyzed to define metrics that help quantify load-shaping opportunities.</p

Quantifying the Opportunity Limits of Automatic Residential Electric Load Shaping

Electric utility residential demand response programs typically do not shape load using intraday, transactive, and local setpoint adjustments of storage-capable thermostatically controlled loads (TCL). In the future, it is envisioned that utilities will continually broadcast forecast dynamic prices of electricity to automatically shape residential load and create load elasticity by alternatively encouraging or discouraging electric energy use. In this research, a binary conditional algorithm was developed and applied to TCL appliance empirical time series data to estimate price-based instantaneous load add and shed opportunities. To overcome limitations of traditional stochastic methods in quantifying diverse, non-normal, non-stationary distributions, recent developments in spectral methods were applied to capture and simulate load in both the frequency and time domains. The performance of autoregressive and spectral reconstruction methods was compared, with phase reconstruction providing the best simulation ensembles. The terminal application of this work is simulating the monetary savings anticipated from wide-scale deployment of price-responsive model predictive control of air conditioning, domestic hot water (DHW) heating, and battery systems.</p

Chronic Exposure of Corals to Fine Sediments: Lethal and Sub-Lethal Impacts

Understanding the sedimentation and turbidity thresholds for corals is critical in assessing the potential impacts of dredging projects in tropical marine systems. In this study, we exposed two species of coral sampled from offshore locations to six levels of total suspended solids (TSS) for 16 weeks in the laboratory, including a 4 week recovery period. Dose-response relationships were developed to quantify the lethal and sub-lethal thresholds of sedimentation and turbidity for the corals. The sediment treatments affected the horizontal foliaceous species (Montipora aequituberculata) more than the upright branching species (Acropora millepora). The lowest sediment treatments that caused full colony mortality were 30 mg l−1 TSS (25 mg cm−2 day−1) for M. aequituberculata and 100 mg l−1 TSS (83 mg cm−2 day−1) for A. millepora after 12 weeks. Coral mortality generally took longer than 4 weeks and was closely related to sediment accumulation on the surface of the corals. While measurements of damage to photosystem II in the symbionts and reductions in lipid content and growth indicated sub-lethal responses in surviving corals, the most reliable predictor of coral mortality in this experiment was long-term sediment accumulation on coral tissue

Hybrid Communication Architectures for Distributed Smart Grid Applications

Wired and wireless communications both play an important role in the blend of communications technologies necessary to enable future smart grid communications. Hybrid networks exploit independent mediums to extend network coverage and improve performance. However, whereas individual technologies have been applied in simulation networks, as far as we know there is only limited attention that has been paid to the development of a suite of hybrid communication simulation models for the communications system design. Hybrid simulation models are needed to capture the mixed communication technologies and IP address mechanisms in one simulation. To close this gap, we have developed a suite of hybrid communication system simulation models to validate the critical system design criteria for a distributed solar Photovoltaic (PV) communications system, including a single trip latency of 300 ms, throughput of 9.6 Kbps, and packet loss rate of 1%. The results show that three low-power wireless personal area network (LoWPAN)-based hybrid architectures can satisfy three performance metrics that are critical for distributed energy resource communications