Heating, Ventilation And Cooling System Research Articles

Effectiveness of Air Filtration in Reducing PM2.5 Exposures at a School in a Community Heavily Impacted by Air Pollution

Reducing children’s exposure to air pollution is a priority among California communities heavily impacted by air pollution exposures. We conducted an observational air quality study at a school to investigate the effectiveness of improved Heating, Ventilation, and Cooling (HVAC) system filters and portable air cleaners (PACs) in reducing children’s exposure to fine particulate matter (PM2.5) under real-world classroom conditions. This study included five classrooms, three of which had PACs. Halfway through the study period, high-efficiency HVAC filters were installed in all five classrooms. Continuous measurements of outdoor and in-classroom PM2.5 concentrations were used to evaluate filtration effectiveness. The air filtration strategies, alone and in combination, demonstrated 14–56% reductions in indoor PM2.5 concentrations compared to outdoor levels. There were significant improvements in filtration resulting from HVAC filter upgrades in the two classrooms without PACs (11% and 22% improvement, p < 0.001). Upgrading HVAC filters in classrooms with PACs did not significantly improve filtration effectiveness, suggesting that utilizing both strategies simultaneously may not meaningfully improve air quality under these circumstances. CO2 data, as a proxy for ventilation, helped demonstrate that the observed filtration effectiveness was likely impacted by the variable HVAC system use and open doors.

How sociotechnical norms shape transition pathways: The co-evolution of three European heating, ventilation, and cooling (HVAC) regimes

Countries across Europe have ambitious targets to become carbon neutral. This requires a transformation in the way buildings are heated, ventilated, and cooled (HVAC), with a move away from fossil fuels. Highly divergent pathways currently exist between different European HVAC regimes. However, few studies have examined these differences in detail, or the role of social norms in sustaining or changing HVAC regimes. This mixed methods study examines the decarbonisation of HVAC systems in three European countries of Finland, Greece and the United Kingdom. Based on a quantitative survey of n = 3478 households and 40 qualitative interviews with building users, managers, and designers, we find highly divergent HVAC regimes across the three countries with considerable variability in technologies, user practices, business strategies, institutions and their relationship to ecosystems. We also discover a shifting patchwork of normative perspectives to heating and cooling. These “socio-technical” norms are highly susceptible to peer influence, broader socio-economic and political drivers, and environmental factors such as climate change. Finally, we argue that an appreciation of how these socio-technical norms are formed and influenced, is an essential yet under-explored avenue in research and public policy on sustainability transitions.

Economic Operation of Thermostatic Loads Under Time Varying Prices: An Optimal Control Approach

In this paper, we consider the problem of optimal precooling of thermostatic loads by a load serving entity (LSE) under time varying electricity prices. Specifically, we propose a low complexity dynamic programming based algorithm for controlling the switching of heating, ventilation, and cooling (HVAC) units such that the cost of cooling is minimized while ensuring that the resultant temperatures do not violate the comfort constraints of consumers. Specifically, our algorithm makes use of two facts: first, the price of electricity vary discretely in time; and second, the cost-optimal state trajectory under fixed electricity price and ambient temperature, with given initial and final states, can be characterized explicitly in closed-form. We validate our algorithm with a set of numerical simulation studies using real market prices of electricity from the New York and Texas electricity markets. In addition, we also provide an approximation mechanism to implement this optimization algorithm in HVAC systems that have ON-OFF switching constraints.

Unequal access to energy efficiency in US multifamily rental housing: opportunities to improve

The energy efficiency of US multifamily rental housing is compared with other housing types. A real and growing energy efficiency gap is documented, particularly for lower income households. Findings are based on data from the 2005 and 2009 US Residential Energy Consumption Survey (RECS). Individual energy efficiency features related to HVAC (heating, ventilation and cooling) systems, appliances, and the building envelope are analysed along with weighted and unweighted total energy efficiency indices. Multifamily units occupied by low income renters had 4.1 fewer energy efficiency features in 2005 and 4.7 fewer in 2009 compared with other households. If the number of efficiency features was on par with other housing, the savings could be in the range of US$200–400 per year for most lower-income renters in multifamily buildings. There is an astonishing lack of information on how efficiency retrofits would affect property (real estate) metrics such as cash flow and value. Available evidence suggests that millions of US properties could be good retrofit investment opportunities. Better efficiency would allow renters to increase spending on food, healthcare and other essentials. This is not only an economic issue: it has implications for household health, social equity and environmental problems tied to energy consumption.

Feasibility of retrofitting centralized HVAC systems for room-level zoning

Heating, ventilation, and cooling (HVAC) accounts for 38% of building energy usage, and over 15% of all US energy usage, making it one of the nation's largest energy consumers. A number of projects have attempted to optimize the control of HVAC systems by minimizing the energy wasted in conditioning occupied buildings or rooms. Researchers have proposed systems that turn off air conditioners or heaters when a house is unoccupied, or put the system into an energy saving deep-setback mode when the occupants are inactive, such as when they are asleep. These approaches enable the retrofitting of centralized HVAC systems, that are widely used within the United States, to be more energy efficient. An area that has not been as well explored is the retrofitting of centralized HVAC systems to save energy when the residents are at home and awake. In this paper, we demonstrate how to use cheap, off-the-shelf sensors and actuators to retrofit a centralized HVAC system and enable the heating, or cooling, of rooms individually, in order to reduce waste caused by conditioning unoccupied rooms. We call this approach room-level zoning. Sensors detect room state and learned activity patterns are used to predict occupancy. Based on this information, unoccupied rooms drift away from a user defined comfortable temperature if occupants are less likely to use them in the near future while occupied rooms remain at a comfortable temperature. Thus, conditioning only the rooms with a high probability of occupancy to the setpoint saves energy by decreasing the load on the HVAC system. We implement a room-level zoning system, called Dual-Zone, in a 1400 square foot house by retrofitting an existing centralized HVAC system with wireless temperature sensors to monitor room-level temperature, motion sensors to monitor occupancy, and wirelessly actuatable dampers to control the flow of conditioned air through the house. Dual-Zone statically zones the house into two zones: one conditioned at night and the other conditioned during the day. Initial analysis indicates that this method has a 20.5% energy savings over the existing single-zoned thermostat during a 20 day evaluation.

Occupant comfort in naturally ventilated and mixed-mode spaces within air-conditioned offices

Contemporary concerns for improving environmental performance in buildings have led to an increased interest in natural ventilation (NV) either on its own or in combination with air-conditioning (mixed mode (MM)) as an alternative to traditional heating, ventilation and cooling (HVAC) systems. HVAC systems are widely used because they avoid many of the problems encountered with NV or MM—noise, dust, insects, odours, temperature extremes—and readily conform to steady-state conditions of thermal comfort. However, it is possible that NV or MM can provide improved indoor air quality precisely through variations associated with external climatic conditions. This article introduces an ARC (Australian Research Council) funded project evaluating comfort conditions in MM spaces, using field studies from two buildings. The first, a University campus building in Sydney, offers MM perimeter offices with air-conditioned central spaces, while the second, a commercial building in Melbourne, offers a series of MM spaces that can be used by workers from adjacent air-conditioned office spaces. The aim of the project is to evaluate the feasibility of using MM either in place of or in association with traditional HVAC systems. The outcomes of the project will be used to elaborate the justifications for inclusion of NV spaces and/or NV periods within contemporary office environments. This article presents preliminary results of the fieldwork at each location.