With the constant expansion of the building sector as a major energy consumer in the modern world, the significance of energy-efficient building systems cannot be more emphasized. Most of the buildings are now equipped with an electric dashboard to record consumption data which presents a significant scope of research by utilizing those data in energy modeling. This paper investigates conventional regression modeling in building energy estimation and proposes three models with data classifications to improve their performance. The proposed models are regression models and an artificial neural network model with data classification for predicting hourly or sub-hourly energy usage in four different buildings. Energy data is collected from a building energy simulation program and existing buildings to develop the models for detailed analysis. Data classification is recommended according to the system operating schedules of the buildings and models are tested for their performance in capturing the data trends resulting from those schedules. Proposed regression models and an ANN model with the recommended classification show very accurate results in estimating energy demand compared to conventional regression models. Correlation coefficient and root mean squared error values improve noticeably for the proposed models and they can potentially be utilized for energy conservation purposes and energy savings in the buildings.

Buildings account for a large portion of the total energy use in the US; therefore, improving the operation of typical variable-air-volume (VAV) systems in buildings can provide a tremendous economic opportunity. ASHRAE Guideline 36 recommends a resetting strategy for supply air temperature (SAT) for VAV systems based on outside air temperature. However, this strategy may not produce optimal performance, particularly when simultaneous cooling and heating occurs in zones. In addition, there is no strategy recommended in the Guideline to reset the zone minimum airflow set point in a single-duct VAV terminal unit with reheat, although this setpoint has a great impact on zone reheat requirements and ventilation efficiency. Thus, this paper introduces new strategies to reset both the SAT and zone minimum airflow rate set points to improve the efficiency of typical VAV systems. The strategies were tested under various conditions through experiments performed in fully instrumented VAV systems located in the HVAC lab at the University of Cincinnati. The experiments were conducted on a chilled-water VAV system that serves three controlled zones with hot-water reheat VAV boxes controlled by a typical commercial BACnet web-based building automation system BAS. The simulation studies were performed using the building energy simulation software EnergyPlus to evaluate the strategies at a larger scale in various locations. The simulation results show that the proposed resetting strategies can provide fan energy savings between 1.6% and 5.7% and heating load savings between 7.7% to 33.7%, depending on the location. The laboratory testing shows that the proposed strategies can provide stable control performance in actual systems as well as achieving the anticipated reheat and fan energy savings. The result offers significant improvements that can be implemented in the Guideline for single-duct VAV system operation and control.

The building sector accounts for a substantial amount of energy consumption, resulting in higher carbon emissions and environmental impact worldwide. Electrification and energy efficiency in building systems can be the key to decarbonization in buildings. This research proposes new heating and cooling loops consisting of heat pumps to lower natural gas usage in building systems. Typical chillers and boilers in the cooling and heating loops are replaced with heat pumps to serve the loads and maintain thermal comfort in the building. In addition, a new optimal supply air temperature (SAT) reset strategy is also implemented with the proposed configuration for better system performance. A large multi-zone office building is simulated as a case study to measure the conventional system’s electricity and natural gas consumption and the proposed design. Even with heat pumps that use electricity as the energy source, electricity consumption is reduced by 3.3% to 11.8% in different climate zones for the proposed system. On the other hand, 10.2% to 67% lower natural gas is consumed when the proposed system and the optimal SAT reset are utilized. The carbon emission is also reduced by 10.8% to 38% compared to the conventional system. The results show that the proposed design and optimization strategy can lead to significant energy and cost savings in conjunction with lower carbon emissions.

ASHRAE Guideline 36 recommends resetting the Supply Air Temperature (SAT) for Variable Air Volume (VAV) systems to balance fan power, heating and cooling loads and zone reheat requirements. This is achieved by employing a trim and response algorithm in conjunction with using the outside air temperature and readings from zone cooling loops. However, resetting the SAT for the VAV systems with parallel fan-powered terminal units according to Guideline 36 recommendations may not produce the best performance. Reducing the reheat requirement in parallel fan-powered terminal units can be done by increasing the air recirculating at the zone level rather than at the system level. This will allow keeping the system level SAT as cold as possible to reduce fan airflow for the zones in cooling with no or little effect on heating requirement for the zones in heating. Therefore, this study evaluates SAT control strategies and fan-powered terminal airflow rates to maximize total energy efficiency. Multiple airflow rate designs and operational variables such as the size of the fan-powered terminal unit and minimum airflow rate set point are included in this study. The simulation results for a typical small commercial building in various locations show that the new resetting method with local zone air recirculation enhancement can significantly reduce fan energy use with little effect on the heating requirement. The result may significantly improve the guideline related to the sequence of operation in a parallel fan-powered terminal unit.

As building systems account for almost half of the total energy consumed by the building sector to provide space heating, cooling, and ventilation, efficiently designing these systems can be the key to energy conservation in buildings. Dual VAV systems with an effective control strategy can substantially reduce the energy consumption in buildings, providing a significant scope of further research on this system configuration. This paper proposes to utilize the warm air duct of the dual VAV system as a dedicated outdoor air (DOA) unit when no heating is required, which allows the cooling load to be effectively distributed between two ducts. A specific control sequence is proposed with different supply air temperature reset strategies to estimate the heating, cooling loads, and fan power energy consumption of the proposed system. A simple two-zone office building is taken as a preliminary case study to simulate the airflow rates and fan power of a single duct VAV and proposed dual VAV systems to illustrate the concept. Finally, a larger multi-zone office building is simulated to measure the annual heating, cooling loads, and fan power energy and compare the energy savings among the systems. The results show significant fan power reduction ranging from 1.7 to 9% and notable heating energy reduction up to 76.5% with a small amount of cooling load reduction varying from 0.76 to 2.56% depending on the different locations for the proposed dual VAV systems. Further energy savings from different supply air temperature reset strategies demonstrate the opportunity of employing them according to climates and case studies. The proposed dual VAV system proves to have the potential to be adapted in buildings for the purpose of sustainability and energy savings.