P5. Aggregated Load Shedding > Outcomes

Technical Outcomes:

• Load shedding potential is a function of many variables, which may be summarized in three building/occupancy characteristics and one control parameter.
  
  • aggregate magnitude of operating loads (primarily lighting and plug loads) that can be shut off at the time that load curtailment is called for;
    
  • cooling plant efficiency (that is, what is the reduction in HVAC plant power that can be realized per kW reduction in lighting and plug loads); and
    
  • potential for thermal storage within the conditioned space (determines what additional reduction in cooling capacity can be achieved).

• Aggregated-load shedding for groups of two or three buildings is effective in reducing peak demand and overall power consumption. Based on the specific building models, load patterns, weather conditions and rate structure used in this research, a peak load reduction of 2 - 14% and a cost-based peak load reduction of 2 - 12% for two or three building aggregation cases with thermostats as control variable was achieved. A 27% peak load reduction and around 20% cost reduction in a two-building case with both fan-based and chiller-based night cooling enabled was observed. Exact numbers depend on the correlation and interdependence of the individual participants.
  
  Short duration (one hour) load curtailment experiments showed that about 330 kVA could be saved in the ECC building and about 250 kVA in the ISD building.

• Night pre-cooling experiments demonstrated that chiller and pump power could be reduced by 20% for an entire day by pre-cooling the building the night before. The researchers noted that extended periods of night pre-cooling, including over weekends would be needed to establish the full potential of the strategy.

• Numerous faults were discovered through analysis of the monitored data and through visual observation during site visits.

Market Outcomes:

Although the results show that aggregated load shedding is feasible, the complexity of simulating and optimizing load shedding on an aggregated basis for only two or three buildings is very high. Defining a set of California guidelines to cover a large range of building types, occupancies, HVAC systems, and climate zones will require a significant amount of additional research.

Independent of the research project, the County decided not to continue participating in the utility load curtailment program after some experience with the costs and benefits. Utilities may need to restructure the incentives to attract a stable pool of participants.

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