2016 ASHRAE Annual Conference

This paper provides recommendations for data-driven interfaces for advanced building operations and maintenance developed through ASHRAE Research Project 1633 (RP1633). Informing operations and maintenance with data-driven information is critical to achieve high performance buildings. Substantial guidance, such as ASHRAE Guideline 13 and Performance Measurement Protocols for Commercial Buildings, has already been created illustrating how to measure and convey building performance information. RP1633 focused attention on operations and maintenance stakeholders, including control technicians, heating ventilation and air conditioning (HVAC) technicians, service providers, commissioning agents, and facility managers by conducting literature reviews, commercial interface reviews, and stakeholder interviews in order to create guidance about data-driven metrics and visualizations that clearly quantify and communicate building operational performance to these stakeholders. The results of this research are presented here, with recommendations to provide metrics and visualizations at multiple scales, including portfolio-wide, whole building, and for specific building areas, systems, and equipment. Metrics span categories related to operating costs, utility consumption, carbon emissions, system performance, controllability, faults, and energy savings. Metrics may be visualized: on maps, system graphics, and in floorplans; as time-series line c harts, in calendar plots, bar charts, and pie charts; and relative to expected performance, past performance or a relevant benchmark. Feedback is presented from operations and maintenance personnel and our research about the types of metrics, at each scale, in which visualization format are most useful for advanced operations and maintenance.

According to some estimates, pumps account for between 10% and 20% of world electricity consumption (EERE 2001; Grundfos 2011). Unfortunately, about two thirds of all pumps use up to 60% too much energy (Grundfos 2011), primarily because of inefficient flow control. Varying pump speed using a variable frequency drive on the pump motor is one of the most efficient methods of flow control. As a consequence, about one-fifth of all U.S. utilities incentivize variable frequency drives (VFDs) (NCSU 2014), and many of these drives control pumping systems.
However, field studies and research show that few variable-flow systems are optimally controlled and the fraction of actual-to-ideal savings is frequently as low as 40% (Kissock 2014; Ma 2015; Song, L., Assistant Professor, Department of Mechanical Engineering, University of Oklahoma, pers. comm., July, 2013.). Utility incentive programs that rely on ideal energy saving calculations could overestimate savings by 30% (Maxwell 2005).
Previous work has shown the importance of changing motor efficiency, VFD and pump efficiency on savings (Bernier and Bourret 1999; Maxwell 2005). This work considers the difference between actual and ideal savings caused by excess bypass flow, position and setpoint of control sensors, and control algorithms. This paper examines the influence of these factors on energy savings using simulations, experimental data, and field measurements. In general, energy savings are increased when bypass is minimized or eliminated, pressure sensors for control are located near the most remote end use, and the pressure control setpoint is minimized.

Variable frequency drives (VFDs) are widely applied on induction motors that drive fans, pumps and compressors. Under partial loads, VFDs not only adjust frequency to reduce motor speed and mechanical output power (load) but also adjust voltage to reduce motor electrical input power. Traditionally, VFD manufacturers recommend controlling the voltage to be proportional to the square of the frequency for variable torque motor loads on fans and pumps, and controlling the voltage to be proportional to the frequency for constant torque motor loads on compressors. The purpose of this paper is to investigate energy efficient voltage-frequency ratios of VFDs using the motor equivalent circuit method. First, the motor load and speed correlation is derived for different applications; then VFD voltage is optimized for a given VFD frequency to maximize motor efficiency; and finally the motor efficiency is simulated and compared under the optimal voltage and different preset voltages. The simulation results show that the motor efficiency with the ratio of voltage to frequency to the power of 1.5 is mostly close to the optimal efficiency for variable torque motor loads and the motor efficiency with the ratio of voltage to frequency to the power of 0.5 is mostly close to the optimal efficiency for constant torque motor loads with efficiency improvement by up to 3% over the traditionally ratios.