Buildings account for a significant fraction (~45-75% depending on the region) of total electricity consumed in North America. Electricity demand in buildings vary seasonally, daily, hourly and even on a second scale depending on a wide range of factors including but not limited to: building type, climate, efficiency and controls of lighting and appliances, availability of electricity generation technologies (e.g., solar photovoltaics), and energy source/carrier (electricity vs. natural gas) used for space heating, domestic hot water, or cooking.
Energy performance in building sustainability standards and rating systems is typically assessed in terms of total annual energy costs, primary energy consumption, and GHG emissions. These indicators intrinsically assume that 1) the electricity grid environmental and cost performance is constant throughout the year, and 2) that the load of a building does not affect the performance of the electricity grid. However, both these assumptions are inaccurate.
As the loads of the individual components in the grid change over time, the overall demand in the system varies. Variability in total system electricity demand lead to both economic and environmental costs due to 1) more costly and less efficient power generation units are brought on-line as demand increases, 2) transmission and distribution losses increase during peak demand periods, 3) peaks in electricity demand drive system capacity, 4) marginal generation units operate with lower efficiencies due to frequent ON/OFF cycling or ramp-up/ramp-down.
Variations on electricity load of an individual building are insignificant to the electricity system. However, given that the aggregated load of the built environment dominates the overall electricity system load, an assessment framework that reflects the impact that different building demand patterns have on the electricity grid is needed.
This study proposes “Grid Compensation Scores” (GCS) that assess the contribution of a building electricity demand profile to reducing variability in the system electricity demand profile. The GCS can be calculated on an annual or daily basis, which can provide insights on the building’s impact on system capacity and system operating efficiency, respectively.
The GCS are applied to two building types (single family house and office building), located in two different electricity systems (Alberta and Ontario), and with a variety of building energy technologies (building variants). Results show significant differences in the GCS of different technologies depending on the building type, the electricity system, and the time scale (seasonal vs. daily). The grid compensation scores provide a quantitative assessment of the impact of building variants on the electricity grid at different time scales, which allow for a systematic comparison among building variants. The authors recommend to use a suite of building performance indicators including annual energy and GHG emissions, grid compensation scores at annual and daily scales, and annual peaks of electricity imports and exports. A set of indicators would better inform design teams about the potential consequences of building design decisions.
• Sustainability and resilience metrics , • Infrastructure systems, the built environment, and smart and connected infrastructure , • Decision support methods and tools
