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Buildings are responsible for more than 73% of the total electricity usage in the United States and have a significant contribution to peak electrical demand of the power grid. Thus, proper building demand management could improve the robustness and efficiency of grid operation and could also result in economic benefits for building owners. Almost half of the building electricity usage occurs in the commercial building sector where 60% of the installed cooling capacity is attributed to small commercial buildings employing packaged air-conditioning systems (e.g., rooftop units). Thus, understanding the demand response potential and economic benefits for the small commercial sector is of great importance. In particular, the effect of climate, building type, and utility structure on demand response potential is valuable information for building managers in identifying the most beneficial demand response strategies and for utilities in developing better utility structure rate incentives to achieve demand reduction. This article presents a simulation-based assessment approach and highlights the key assessment results for three demand response strategies—thermostat, shade, and lighting controls—across a range of building types, vintages, locations, and utility rate structures. The control performance is evaluated in terms of utility cost savings, peak demand reductions, and indoor comfort impacts in comparison to a baseline night setup strategy. The tradeoff between cost savings and comfort is also explicitly investigated. The assessment results show that the demand response controls lead to slightly worse indoor comfort compared to the baseline control, with an increase in the median percentage of people dissatisfied from 5.7% to 8.1%. However, significant demand reductions and cost savings could be achieved across all tested cases with the magnitudes dependent on the weather condition and building type. Annual electricity cost savings of 5 to 25 cents/ft2 (54 to 269 cents/m2) were demonstrated for time-of-use energy rates with demand charges, whereas the savings were relatively small, below 5 cents/ft2 (54 cents/m2) for most cases, when buildings subscribed to flat rates without demand charges. [ABSTRACT FROM AUTHOR]

Packaged air-conditioning systems, such as rooftop units (RTUs), are widely used in small commercial buildings in the United States. Although new regulations and standards require new air-conditioning equipment to have multi-speed supply fan operation, most of the installed units employ fixed-speed supply fans. The electrical energy usage associated with constant volumetric air delivery fan systems is on the order of half the total RTU electrical energy usage because supply fans operate continuously during the occupied periods in commercial buildings for ventilation. In addition, compressors within RTUs typically feature single- or two-stage capacity controls leading to frequent unit cycling and thus, deteriorated performance in energy efficiency. This paper presents relatively comprehensive assessment results for three RTU variable-speed retrofit options: 1) retrofits of fixed-speed supply fans with variable-speed fans for single-compressor-speed units, 2) replacement of existing fixed-speed RTUs with RTUs having two-speed compressors with variable-speed supply fans and 3) retrofits of RTUs with new RTUs that incorporate variable-speed compressors and fans (indoor and outdoor). The assessment study involves parametric simulations across different building types and locations in the U.S. to understand the performance variation with respect to location and building use. Performance improvements in terms of energy efficiency, operation cost and indoor comfort delivery for the various retrofit options are demonstrated compared to conventional single-stage RTUs with constant speed supply fans. The assessment results show that all three retrofit options offer significant fan energy savings, but much smaller savings potential for compressor and condenser fan electricity consumption. The variable-speed-unit retrofit provides the highest cost savings potentials, ranging from 40 to 250 $ per rated cooling ton per year depending on the building type and location. In addition to efficiency and economic benefits, the two-stage-unit and variable-speed-unit retrofits also lead to improved indoor humidity regulation performance due to reduced unit cycling. [ABSTRACT FROM AUTHOR]

In recent years, variable electricity pricing has become available to residential consumers to incentivize demand reductions during midday peak hours. Thermal energy storage (TES) systems enable consumers to store cooling energy when demand is low and assist A/C operation during peak demand periods. However, the cost savings achievable using TES are highly dependent on how the system is operated for a given utility rate structure. This study investigates control strategies for a packaged chiller unit integrated with ice storage that leverage available residential utility rate structures in the U.S. to reduce consumer electricity cost. The present work describes the development and evaluation of a generalized rule-based control strategy inspired by the performance of an optimal controller that minimizes monthly electricity cost considering both time-of-use energy and demand charges. The generalized rule-based controller is compared against the optimal controller as well as to heuristic control strategies for TES that were originally developed for commercial buildings for a range of equipment cooling capacities, TES sizes, geographic locations, and residential utility rates. The total electricity cost is determined using a simulation model that includes models for the chiller unit, ice storage tank, and secondary loop components, along with a building load model. Results show that the generalized rule-based controller can approximate the performance of the optimal controller within 20% for all cases tested, and within 10% of the optimal cost in 53% of the cases tested. The controller also performs significantly better than the heuristic strategies for commercial buildings that were evaluated. [ABSTRACT FROM AUTHOR]

The author reflects on the trend and development of heating, ventilation, air-conditioning & refrigeration (HVAC&R) equipment in the U.S. The author cites the trend strated in 1980s wherein intelligent buildings are developed promising effective operational cost savings. The author explains that the said trend has encouraged manufacturing companies to design innovative and environmental friendly HVAC&R equipment systems for intelligent buildings.