ENERGY FLOW ANALYSIS ON A MULTI-ZONAL BUILDING SCALE USING SANKEY DIAGRAMS

Modern commercial buildings have complex mechanical systems and heat transfer paths, and their performance is typically difficult to visualize. Current data availability and visualization tools do not lend themselves well to identifying inefficiencies and possible solutions. Sankey diagrams have been found to be useful tool in energy management and performance improvement. However, there are limited existing applications on the building level. This paper proposes a method to estimate and visualize energy flow on the building level. The objective is to demonstrate the applicability of Sankey diagrams to identify opportunities for energy savings. The proposed methodology is then applied to an 8,000 m2 multi-zone Canadian university building. Data for resource consumption were obtained from meters and sensors installed in the building. While building energy performance data were obtained from a calibrated building performance simulation (BPS) model of the building to understand the interrelated variables that affect building performance. The outcome of this work is to help identify and quantify the significant measured and unmeasured energy flows. INTRODUCTION Nowadays, commercial and institutional buildings sector energy demand is significantly increasing (NRCan, 2014). Most of modern buildings utilize energy management and control systems (EMCS) for monitoring and optimizing building systems during operation. EMCS could provide spatial and temporal data resolution obtained from meters and sensors installed in buildings. However, the data from metering and logging systems are often inconvenient and difficult to access due to use of multiple systems and technologies of varying vintages and platforms. Furthermore, most of the developed visualization tools for building energy management use simple line or bar charts for presenting and comparing metered energy consumption, greenhouse gasses (GHG) emissions, and other performance metrics (Yarbrough et al., 2014). On the building level, Pulse Energy developed an Energy Dashboard tool that shows real-time building consumption of energy, natural gas, hot water, chilled water, and steam for campus buildings (UBC, 2014 a; McGill University, 2015). Other tools such as Building Dashboard and Energy Efficient Education Dashboard were developed to visualize energy consumption of commercial buildings (Lucid, 2014). The current visualization tools typically only provide an end-use breakdown of energy consumption, depending on installed meter resolution. However, these tools are difficult to provide a comprehensive energy flow analysis on the building scale (i.e. how energy enters and is consumed in buildings). Furthermore, the current data availability and visualization tools do not lend themselves to identification of inefficiencies and possible solutions to improve efficiency or recover energy. Many researchers have been focusing on analyzing and visualizing building energy use (Belzer, 2006; Abdelalim et al., 2015). The building gross energy needs should be quantified, which represents the anticipated buildings energy demands for heating, cooling, lighting, refrigeration, water heating, and equipment. The building’s energy demand is determined by different parameters, such as indoor climate requirements, outdoor climatic conditions, building envelope thermal properties, and infiltration rates (Santamouris, 2010). There are also opportunities for recovering energy and understanding the relationship between heat gains and heating and cooling loads. For instance, the choice of light bulbs/fixtures should incorporate their impact on heating and cooling loads. On the other hand, Sankey diagrams can provide relative flow magnitudes, direction of flows, inputs and outputs of interacting systems, and energy recovery. Moreover, spatial representation (e.g., the order of systems and components can be approximately laid out in a Sankey diagram). A study by (Abdelalim et al., 2015) proposed several methods to analyze and visualize building-level water, natural gas, and electricity consumption and the upstream environmental impacts using Sankey diagrams and other graphical techniques. Belzer (Belzer, 2006) developed energy flow maps to depict