Grid-Interactive Efficient Building (GEBS)

The commercial building industry generally understands the potential and benefits of HVAC energy savings and solar generation. However, the market is just starting to comprehend the benefit and potential of battery storage integration to optimize efficiencies in grid-interactive efficient buildings (GEBs), which is defined as “an energy-efficient building that uses smart end-use equipment and/or other onsite distributed energy resources (DER) to provide demand flexibility while co-optimizing for energy cost, grid services, and occupant needs and preferences, in a continuous and integrated way” (Lawrence Berkeley National Laboratory, 2023). This project originated through a response to the U. S. Department of Energy’s (DOE) High Impact Technology Catlayst program and the General Services Administration joint request for proposal for their GEBs initiative. The DOE initiative provided M&V support but offered no project funding. SCE agreed to provide project support and funding for the effort. A building owned and managed by the Judicial Council of California (JCC) was identified as the potential field-testing site due to the magnitude of their building portfolio (450 courts) in California, and aggressive energy and cost reduction goals (30% by 2030). The JCC sites were a good representation of a medium commercial market. AESC worked with JCC to screen forty-nine potential SCE sites between 50,000 and 150,000 sq ft with HVAC systems installed after 2000 and that could accommodate a cost-effective rooftop solar and battery system. Ultimately, a courthouse in Orange County was identified and selected as an ideal demonstration site meeting all criteria above and the necessary characteristics of a GEB (efficient, connected, smart, and flexible). The 52,000 sq. ft. courthouse was constructed in 2009 and therefore the building’s equipment was relatively new and efficient. The building already had an existing building automation system (BAS) that is smart and connected. The courthouse had ample space for the potential installation of solar PV and battery for load flexibility. Another major factor of the host site selection was that the building’s characteristics are common across the medium commercial market, which increased the viability of this project being a model for future replications. The project intended to study real-world operation of a GEB at the courthouse leveraging a low-cost energy Internet of Things (IoT) gateway to evaluate the following GEBs load control hypotheses: Energy Efficiency/Load Shift – Enabling remote optimization of building operation (estimated at 10% of baseline energy savings). Demand Response without Solar and Battery – Enabling load shed (estimated at 10% of baseline demand peak load). Demand Response with Solar and Battery – Enabling load shed (estimated at 40% of baseline demand peak load). Resiliency – Enabling additional hours of emergency islanded resiliency by deploying load control strategies (estimated at four to six hours of operation). The project experienced multiple barriers along the way including repeated delays in contracting for the solar and battery storage installation, delays and the ultimate rejection of control and efficiency measure incentive funding; and COVID-19 associated difficulties including building occupation and equipment supply chain issues. As a result, the project team proposed modeling the operation and impact of the building using engineering analysis and industry modeling tools. An energy model for the courthouse was developed in eQUEST to evaluate whether the GEB’s combined solutions of energy efficiency, demand management, greenhouse gas (GHG) emission reduction, and power resiliency could offer greater value in concert than they can individually. Additionally, the project provided a cross section of financial benefits based on multiple California investor-owned utility (IOU) rates. The following conclusions were drawn from the study: Solar and battery storage are necessary to facilitate greater building control and flexibility to support GEB operations. Implementation of energy efficiency and RCx measures are a critical part of GEBs to reduce overall building load and increase flexibility. Opportunities include all means of energy efficiency, controllable loads, emerging technologies, DERs, and energy storage systems. Traditional energy efficiency measures such as LED lighting replacement and occupancy controls reduce the baseload and increase the potential impact of the DERs, DERs such as rooftop solar allow for site generation and energy storage systems (i.e., battery) allow for load shifting and resiliency. RCx and controls allow for building optimization and load flexibility. Emerging technologies such as smart/connected equipment and an IoT gateway allow further optimization and flexibility. The load shed scenario was simulated by increasing the cooling setpoints during the 4PM-9PM peak. The results showed that a GEB could shed the building’s peak demand by 21% and reduce the five-hour average by 30% by optimizing the battery discharge in the evening. Greater load reduction and flexibility would be possible if the building’s controls system was upgraded to incorporate lighting and plug loads into the GEB network to operate in concert with the other electromechanical systems. The pre-cooling strategy was used to simulate the load shift scenario. By leveraging the battery discharge and the load shift strategy, building loads were successfully shifted from the “neck of the duck” to the “belly of the duck,” maximizing the on-site usage of solar generated (vs exported). However, using the thermal mass of a building to impact its cooling and heating loads requires intelligent controls and may require tests and simulations for successful implementation. In addition, flexing building load to optimize to price signals such as RTP requires complex balancing of the DERs and building load and will need to consider many variables, including solar availability and the battery’s SOC at the start of the event. The simulations showed that four-hour building resiliency could be achieved while reducing the building load to critical loads only. However, the full battery capacity was required for the four-hour operation and therefore the battery needed to be fully charged at the start of a resiliency event. To accommodate this, the battery was charged from the grid at night. The cost analysis showed that the load shed scenario had the highest cost savings with solar and battery under the TOU-GS-2-E rate. As expected, TOU-GS-D RTP was found to be the most expensive but provided the lowest GHG emissions of 120 tons of CO2 equivalent. In general, TOU-GS-E rate provided the highest cost savings for all the scenarios with solar and battery.