Case Study of an Innovative HVAC System with Integral Dehumidifier

In most applications, heating, ventilating, and air conditioning (HVAC) equipment is controlled to maintain an indoor dry-bulb set point temperature. Moisture removal by the HVAC system is considered to be an operational byproduct. During summer months, the operation of the HVAC system is usually sufficient to meet both the sensible and latent cooling loads. However, during other times of the year when sensible loads are reduced, the moisture load can be significantly higher than the available moisture removal capacity of the air conditioning system. This can lead to elevated indoor relative humidity levels and an uncomfortable indoor environment. In many cases, designers, engineers and building occupants combat high indoor relative humidity and associated comfort problems with the use of additional dehumidification equipment for both commercial and residential applications. The use of extra dehumidification equipment can be expensive in terms of first cost and annual operating costs. First costs associated with this type of equipment may include additional electrical circuits, condensate drainage, and additional air distribution systems. The loss of usable floor area, localized noise, and zonal “hotspots” can also be considered a cost penalty. As an alternative to using separate equipment for meeting both the sensible and latent components of a building’s cooling load, off-the- shelf products were used to construct a self-contained air handler. The air handler is controlled using a low-cost thermostat and humidistat. The dehumidification element of the system is completely independent from the air conditioner and works nearly the same as conventional dehumidification equipment. At times, both the dehumidification equipment and the air conditioner operate in unison when the need arises. The use of dehumidification equipment integrated with a conventional AC system provides a unique solution for moisture control applications. This paper describes the development and testing of this integrated equipment. Although this technology is not new, the integration of a dehumidification system with a standard air conditioner is an innovative strategy that can be used to address moisture control in buildings. This new HVAC configuration would provide a low-cost solution for building owners and a more comfortable indoor environment for building occupants

REDUCING ENERGY USE IN FLORIDA BUILDINGS

The 2007 Florida Building Code (ICC, 2008) requires building designers and architects to achieve a minimum energy efficiency rating for commercial buildings located throughout Florida. Although the Florida Building Code is strict in the minimum requirements for new construction, several aspects of building construction can be further improved through careful thought and design. This report outlines several energy saving features that can be used to ensure that new buildings meet a new target goal of 85% energy use compared to the 2007 energy code in order to achieve Governor Crist’s executive order to improve the energy code by 15%. To determine if a target goal of 85% building energy use is attainable, a computer simulation study was performed to determine the energy saving features available which are, in most cases, stricter than the current Florida Building Code. The energy savings features include improvements to building envelop, fenestration, lighting and equipment, and HVAC efficiency. The impacts of reducing outside air requirements and employing solar water heating were also investigated. The purpose of the energy saving features described in this document is intended to provide a simple, prescriptive method for reducing energy consumption using the methodology outlined in ASHRAE Standard 90.1 (ASHRAE, 2007). There are two difficulties in trying to achieve savings in non-residential structures. First, there is significant energy use caused by internal loads for people and equipment and it is difficult to use the energy code to achieve savings in this area relative to a baseline. Secondly, the ASHRAE methodology uses some of the same features that are proposed for the new building, so it may be difficult to claim savings for some strategies that will produce savings such as improved ventilation controls, reduced window area, or reduced plug loads simply because the methodology applies those features to the comparison reference building. Several measures to improve the building envelope characteristics were simulated. Simply using the selected envelope measures resulted in savings of less than 10% for all building types. However, if such measures are combined with aggressive lighting reductions and improved efficiency HVAC equipment and controls, a target savings of 15% is easily attainable

A conserved zinc-binding site in Acinetobacter baumannii PBP2 required for elongasome-directed bacterial cell shape

Acinetobacter baumannii is a gram-negative bacterial pathogen that causes challenging nosocomial infections. β-lactam targeting of penicillin-binding protein (PBP)–mediated cell wall peptidoglycan (PG) formation is a well-established antimicrobial strategy. Exposure to carbapenems or zinc (Zn)-deprived growth conditions leads to a rod-to-sphere morphological transition in A. baumannii, an effect resembling that caused by deficiency in the RodA–PBP2 PG synthesis complex required for cell wall elongation. While it is recognized that carbapenems preferentially acylate PBP2 in A. baumannii and therefore block the transpeptidase function of the RodA–PBP2 system, the molecular details underpinning cell wall elongation inhibition upon Zn starvation remain undefined. Here, we report the X-ray crystal structure of A. baumannii PBP2, revealing an unexpected Zn coordination site in the transpeptidase domain required for protein stability. Mutations in the Zn-binding site of PBP2 cause a loss of bacterial rod shape and increase susceptibility to β-lactams, therefore providing a direct rationale for cell wall shape maintenance and Zn homeostasis in A. baumannii. Furthermore, the Zn-coordinating residues are conserved in various β- and γ-proteobacterial PBP2 orthologs, consistent with a widespread Zn-binding requirement for function that has been previously unknown. Due to the emergence of resistance to virtually all marketed antibiotic classes, alternative or complementary antimicrobial strategies need to be explored. These findings offer a perspective for dual inhibition of Zn-dependent PG synthases and metallo-β-lactamases by metal chelating agents, considered the most sought-after adjuvants to restore β-lactam potency against gram-negative bacteria

Investigate Peak Demand Reduction Strategies In A Large Office Building Using Energyplus

With the rapidly increasing demands placed on utilities, reducing peak loads and minimizing energy use assume greater importance than ever before. To combat these increasing demands, utilities offer incentives to customers that can shift peak demand to non-peak times or reduce peak loads when notified by the utility that the demand on the grid is close to capacity. This study chose to investigate the control strategies used to reduce building peak demand during a fixed window within a utilities on-peak time period in response to short notification of critical peak periods. The window was chosen to be 6 A.M. in winter, and 2 RM. in summer with a duration of three hours in both winter and summer. The selected large office model was primarily developed by the U.S. National Renewable Energy Lab. Energy Plus is used as a simulation tool for this investigation. Light and heavy building constructions are used to investigate thermal mass impact. Two types of HVAC systems are examined: VAV with reheat and constant-volume dual duct system. The selected control strategies are lighting power density reduction, cooling and heating thermostat setpoints setback control, supply air temperature adjustments, and chilled water temperature reset. The work presented in this paper is a partial work of ASHRAE research project 1390-RP: Short-term Curtailment of HVAC Loads in Buildings. The objective of the project is to identify and evaluate peak demand reduction strategies in response to a short notification. The control strategies are found to be dependent on HVAC system types and locations and almost independent of building constructions. The most effective strategy with VAV with reheat system is lighting power density reduction. The chilled water temperature reset is a close second. These two control strategies are easily implemented. The most effective strategy with dual duct system is chilled water temperature reset and supply air temperature adjustment. The light density power reduction is also recommended. However, thermostat setpoint control setback is not recommended