1,721,096 research outputs found
Reduced Order Models for Rapid Analysis of Ambient Loops for Commercial Buildings
Full text linkFifth-generation district heating and cooling (5GHDC) systems are the next generation of district systems which rely on water approaching indoor ambient temperatures (≈20-25°C). The lower temperatures allow for additional heat sources to be added to the network, allowing for some buildings to become prosumers (e.g. data centers, supermarkets through refrigeration heat rejection). The energy performance of buildings served by a 5GDHC network is a strong function of the inlet temperature, which corresponds to the network supply temperature. Optimizing the network’s efficiency and its grid topology leads to an evaluation of many possible network topologies, which is numerically expensive. To be able to analyze and contrast any given district energy system layout, the impact of connecting individual buildings to a 5GDHC network must be quickly evaluated, while allowing for flexibility in deciding which buildings should be connected to the network.
Conventionally, each building on a district heating and cooling network is represented by a physical building energy model that is run in conjunction with the network simulation. Although this setup allows for running the analysis with flexibility on the building load side, it results in long-running simulations, thus limiting the ability to quickly analyze various network topologies. An alternate approach to determine the building loads is to create a surrogate model, allowing the network simulation to request the building loads from a myriad of predefined building types and building characteristics. Three reduced order modeling techniques were investigated to replace the conventional long running physical building energy models: ordinary least squares regression (linear models), random forests, and support vector machines.</p
Evaluation of the Passive Cooling Potential of Mass Inherent in Medium to Large Commercial Buildings
Full text linkWhile the literature on thermal mass and passive cooling is rich, what it means for a building to be thermally massive is not well defined or consistently applied. Most research has been conducted with mass depths far greater than would be seen in typical construction. Meanwhile, some research suggests that because the heat transfer rate at the surface is limited, the focus should be on surface area of exposed mass. Since even lightweight commercial construction typically has large surface areas of mass in the floor slabs, this research investigates how effective that mass is for passive cooling, relative to other mass depths. In all climates analyzed it was found that there was a pronounced shoulder where energy savings from passive cooling of increasing mass depths was steep until roughly 7.5 cm to 10 cm, and thereafter the energy savings diminished rapidly. When considering the embodied energy of concrete, the incremental benefit of added mass beyond a typical topping slab of 10 cm does not justify the incremental embodied energy cost from an energy standpoint alone, unless a very long embodied energy payback period was adopted
Multi-Use Microgrid Communities and Their Impact on Goal-Based On-Site Renewable Generation
Full text linkAs the power grid ages, demand for energy in the United States increases, and climate change concerns become more widespread, newly-designed communities can implement load and generation in tandem, spreading demand and electricity generation across multiple constituents while simultaneously reducing energy consumption and carbon emissions. Microgrids, when designed to meet goals such as net zero energy or resiliency, have potential to introduce benefits into the power grid system. Environmental impact reduction, financial benefits, and resiliency to the microgrid community as well as possible support to the system make microgrids a promising opportunity for developments. This paper investigates a multi-use community of single family homes, multi-family homes, a small office building, sit-down restaurant, fast-food restaurant, and primary school to understand how on-site electricity generation changes based on load behavior given community goals such as net zero energy or resiliency.</p
Reduced Order Models for Rapid Analysis of Ambient Loops for Commercial Buildings
Full text linkFifth-generation district heating and cooling (5GHDC) systems are the next generation of district systems which rely on water approaching indoor ambient temperatures (≈20-25°C). The lower temperatures allow for additional heat sources to be added to the network, allowing for some buildings to become prosumers (e.g. data centers, supermarkets through refrigeration heat rejection). The energy performance of buildings served by a 5GDHC network is a strong function of the inlet temperature, which corresponds to the network supply temperature. Optimizing the network’s efficiency and its grid topology leads to an evaluation of many possible network topologies, which is numerically expensive. To be able to analyze and contrast any given district energy system layout, the impact of connecting individual buildings to a 5GDHC network must be quickly evaluated, while allowing for flexibility in deciding which buildings should be connected to the network.
Conventionally, each building on a district heating and cooling network is represented by a physical building energy model that is run in conjunction with the network simulation. Although this setup allows for running the analysis with flexibility on the building load side, it results in long-running simulations, thus limiting the ability to quickly analyze various network topologies. An alternate approach to determine the building loads is to create a surrogate model, allowing the network simulation to request the building loads from a myriad of predefined building types and building characteristics. Three reduced order modeling techniques were investigated to replace the conventional long running physical building energy models: ordinary least squares regression (linear models), random forests, and support vector machines.</p
Microgrid Design and Considerations for Rural Colorado
Full text linkRural Colorado communities may only have one connection to the macrogrid and are farther away from urban infrastructure so they more vulnerable if their connection to the macrogrid fails. Giving these communities access to electricity if their grid connection fails is an essential resiliency measure. Microgrids can provide this resiliency. The Distributed Energy Resources Customer Adoption Model (DER-CAM) is used to size a microgrid for a small community. DER-CAM varies the optimization weight of overall cost and emissions to properly size the microgrid. 72-hour outage scenarios show that it is possible to serve a small community with only wind, photovoltaics, and energy storage. Introducing a carbon tax further reduces the carbon emissions of the optimized microgrid. 14 models are evaluated to show general microgrid renewable energy system sizing and costs in comparison to current operating procedures.</p
Microgrid Design and Considerations for Rural Colorado
Full text linkRural Colorado communities may only have one connection to the macrogrid and are farther away from urban infrastructure so they more vulnerable if their connection to the macrogrid fails. Giving these communities access to electricity if their grid connection fails is an essential resiliency measure. Microgrids can provide this resiliency. The Distributed Energy Resources Customer Adoption Model (DER-CAM) is used to size a microgrid for a small community. DER-CAM varies the optimization weight of overall cost and emissions to properly size the microgrid. 72-hour outage scenarios show that it is possible to serve a small community with only wind, photovoltaics, and energy storage. Introducing a carbon tax further reduces the carbon emissions of the optimized microgrid. 14 models are evaluated to show general microgrid renewable energy system sizing and costs in comparison to current operating procedures.</p
Modeling Analysis of Ice Rink Performance
Full text linkA new EnergyPlus module is developed to model indoor ice rink facilities. The study outlined in the thesis presents the justifications of needs for an ice rink module for EnergyPlus, the modeling and integration approaches of the module within EnergyPlus, as well as the results of a series of sensitivity analyses carried out using the developed module. The new EnergyPlus module calculates the refrigeration load needed to maintain the ice rink surface temperature at the desired setpoint. Moreover, the module updates the zone heat balance to determine its impact on HVAC loads. The sensitivity analyses investigate the impacts of several design and operating parameters on the energy performance for an ice rink facility. An energy model for the ice rink facility is developed based on an existing ice rink located in Old Bridge, NJ. The results from the sensitivity analyses confirm that ice rink facilities are energy-intensive buildings due to the significant refrigeration loads. Moreover, the EnergyPlus based analyses indicate that a significant improvement of the energy performance of ice rink facilities can be achieved using easy to implement operation and design measures.</p
Demand Controlled Air Curtains to Reduce Respiratory Infection Risks for Indoor Environments with Displacement Ventilation
Full text linkAir curtains are an effective control for separating spaces and reducing infection risks in indoorspaces. In addition, studies show that displacement ventilation is better for indoor air quality than
mixed ventilation. However, displacement ventilation may be susceptible to a phenomenon called
lock-up, whereby contaminants are held in a lower stratified portion of the air and increase infection
potential. This study investigates whether air curtains or fans can reduce the lock-up phenomenon
for displacement ventilation and reduce infection risk across the breathing zone. Specifically, a
test is conducted to see if a diffuser height, 100% ACH air curtain would be sufficient for reducing
infection risk. Additionally, one and two fans are added to determine if they would reduce the
lock-up phenomenon. The conclusions are that neither a 100% ACH side slot, one fan, nor two fan
cases are adequate to reduce infection risk. In fact, all methods tested increased infection risk. This
increase in infection risk is contrary to previous research and is due to changing air flow patterns
throughout the space that disrupted thermal plumes and created contaminant leakage from one
side of the room to the other. Future research will determine if differing locations, sizes, quantities,
orientations, or flow rates of the fans reduce the infection risks
Modeling Analysis of Ice Rink Performance
Full text linkA new EnergyPlus module is developed to model indoor ice rink facilities. The study outlined in the thesis presents the justifications of needs for an ice rink module for EnergyPlus, the modeling and integration approaches of the module within EnergyPlus, as well as the results of a series of sensitivity analyses carried out using the developed module. The new EnergyPlus module calculates the refrigeration load needed to maintain the ice rink surface temperature at the desired setpoint. Moreover, the module updates the zone heat balance to determine its impact on HVAC loads. The sensitivity analyses investigate the impacts of several design and operating parameters on the energy performance for an ice rink facility. An energy model for the ice rink facility is developed based on an existing ice rink located in Old Bridge, NJ. The results from the sensitivity analyses confirm that ice rink facilities are energy-intensive buildings due to the significant refrigeration loads. Moreover, the EnergyPlus based analyses indicate that a significant improvement of the energy performance of ice rink facilities can be achieved using easy to implement operation and design measures.</p
Demand Controlled Air Curtains to Reduce Respiratory Infection Risks for Indoor Environments with Displacement Ventilation
Full text linkAir curtains are an effective control for separating spaces and reducing infection risks in indoorspaces. In addition, studies show that displacement ventilation is better for indoor air quality than
mixed ventilation. However, displacement ventilation may be susceptible to a phenomenon called
lock-up, whereby contaminants are held in a lower stratified portion of the air and increase infection
potential. This study investigates whether air curtains or fans can reduce the lock-up phenomenon
for displacement ventilation and reduce infection risk across the breathing zone. Specifically, a
test is conducted to see if a diffuser height, 100% ACH air curtain would be sufficient for reducing
infection risk. Additionally, one and two fans are added to determine if they would reduce the
lock-up phenomenon. The conclusions are that neither a 100% ACH side slot, one fan, nor two fan
cases are adequate to reduce infection risk. In fact, all methods tested increased infection risk. This
increase in infection risk is contrary to previous research and is due to changing air flow patterns
throughout the space that disrupted thermal plumes and created contaminant leakage from one
side of the room to the other. Future research will determine if differing locations, sizes, quantities,
orientations, or flow rates of the fans reduce the infection risks
- …
