Electrical and Thermal Load Impacts of Three District Heating and Cooling Designs for an Existing Community in Washington, DC

District energy systems that provide building heating and cooling are a promising option to provide low-cost, energy efficient heating and cooling solutions for communities. As some buildings move to electrified heating designs, there may be significant increases in electric grid demand, particularly in the winter. District energy systems may be able to help reduce these high electrical demands on the electric grid, while also providing decreased energy consumption and increased flexibility. To evaluate and compare system options for district-based heating and cooling, an existing neighborhood of Washington, DC consisting of 35 buildings was selected as a case study. This study models and compares a fourth generation (4G) district heating and cooling system that provides hot and chilled water from a central plant directly to each prosumer and a fifth generation (5G) district heating and cooling system that provides near-ambient water via geothermal boreholes to interface with an energy transfer station with a heat pump at each prosumer. These district systems are compared against a baseline of the non-connected buildings with their self-contained and current HVAC systems. The URBANopt District Energy Systems (DES) model was used to simulate the buildings and create initial Modelica models for the district systems. Finally, the DES models were tuned and simulated in Dymola. The building and district model outputs were post-processed for verification and to calculate the electrical and thermal grid impact metrics. This is the first documentation of this workflow and its complete analysis. The three designed systems were compared via their grid metrics including: total energy consumption, electrical demand peak loads, and system ramping. Compared to the non-connected buildings, the 4G and 5G DES saw a 15% and 20% reduction in total site annual electricity usage, respectively. The range and median electricity usage by the district systems in the summertime are much lower than the non-connected buildings; however, the DES saw similar or higher electricity usage in the winter compared to the non-connected buildings. A detailed discussion is provided about how each system impacts and interacts with the electric grid.