Search NASA⌕ Search

Engineering topics

Shrestha, Prateek

Publications and source records attributed to Shrestha, Prateek.

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Testing of a Whole Home Energy Management System (Cooperative Research and Development Final Report)

NREL and B&B Technology Solutions Inc. will perform verification testing to demonstrate the effectiveness of our whole home energy management system. This energy management system will allow the electrification of various styles of homes reducing the emissions of CO2 by replacing existing fossil fuel-based home systems. CRADA benefit to DOE, Participant, and US Taxpayer: assists laboratory in achieving programmatic scope, and/or uses the laboratory's core competencies, and/or enhances U.S. competitiveness by utilizing DOE developed intellectual property and/or capabilities.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Efficient Air Dehumidification Can Save 15%-50% of Cooling Energy in Commercial Buildings

Current approach to dehumidification in commercial buildings with chilled/hot water AHU systems is to overcool return + supply air to dewpoint, and then reheat before supply to zone. This is energy inefficient, with reheat often being gas-fired. To reduce energy consumption, building operators will often operate at little-to-no outside air, sacrificing IAQ. Decarbonizing commercial buildings requires solutions to reduce and fully electrify dehumidification energy consumption. The Altaire ADAPT and Conservant HEDS systems aim to solve this problem by decoupling humidity control from cooling reduces energy consumption while enabling improved IAQ management.

commercial buildings↗
DOE OSTI2023

Performance Evaluation and Costs of a Combined Ground Source Heat Pump and Solar Photovoltaic Storage System in an Extreme Cold Climate

This report outlines the effectiveness and economics of a ground source heat pump system installed together with solar photovoltaic panels and a battery storage system in a local community building situated in a cold climate. The community building is a tribal building located in Ruby, Alaska. Power from solar photovoltaic panels is supplemented by electricity purchased from the local community microgrid. A ground source heat pump was commissioned three years after the building was occupied, and supplements the heat generated by a boiler for both heat and domestic hot water. Data collected over the 2021-2022 heating season shows that the heat pump is providing heat to the building about 19% of the time with an average coefficient of performance of 2.68, ranging from below 2.5 in winter to above 3.0 in summer. The solar photovoltaic panels provided 4,700 kWh of power used within the building and an additional 2,900 kWh exported to the microgrid. The solar-produced power used within the building nearly offsets the estimated annual electrical draw of the heat pump of 5,700 kWh. Due to the very high costs for shipping and installation to remote locations, projects such as this, while not economically feasible if self-funded, can save the community an estimated $76,051 over a period of 20-years. Fuel prices increasing by more than 25%, or subsidized electricity prices decreasing by more than 25%, make the ground source heat pump a more viable option economically. Unsubsidized electricity prices increasing by 25% or more make a solar photovoltaic system with battery storage nearly economically viable after a 20-year period for commercial or school buildings that are not eligible for Alaska's Power Cost Equalization program.

14 SOLAR ENERGY↗
DOE OSTI2022

Heating and Cooling Energy Modeling of 3D-Printed Concrete Construction of Residential Buildings [Slides]

3D printed concrete construction (C3DP) is an emerging technology that comes with the associated benefits of high thermal mass walls. We investigated using BEopt software the heating and cooling energy use of a single story C3DP-constructed house. We then compared the heating/cooling energy use of the C3DP house against the corresponding energy use in a traditional timber (wood) frame construction (WFC), as well as a concrete masonry unit (CMU) construction. Both peak energy use for heating and cooling (Btu), as well as base energy use for both heating and cooling (MMBtu/yr) of the C3DP design were compared against the WFC and CMU baseline construction of identical geometries and orientations across all eight climate zones defined in the International Energy Conservation Code (IECC). The BEopt models for all three constructions (C3DP, WFC, and CMU) were built to comply with the 2018 IECC code. Results indicate that C3DP construction has significant heating and cooling energy benefits in certain climate zones, with the highest peak cooling energy savings (9% compared to WFC, and 5% compared to CMU) in the IECC Climate Zone 1 in the month of July. The peak heating and cooling energy demand reduction of C3DP were found to be more significant than the base heating and cooling energy demand in all IECC climate zones. The 2018 IECC compliance-related U-Factor adjustments of all models also resulted in more peak energy savings of the C3DP design in the cooling-dominated climate zones (climate zones 1 and 2), moderate energy savings in moderate climate zones (climate zones 3, 4, and 6), and little to no change in energy savings in very cold climates (climate zones 7 and 8).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Multizonal modeling of SARS-CoV-2 aerosol dispersion in a virtual office building

The dispersion of indoor airborne contaminants across different zones within a mechanically ventilated building is a complex phenomenon driven by multiple factors. In this study, we modeled the indoor dispersion of airborne SARS-CoV-2 aerosols within a US Department of Energy detailed medium office prototype building using CONTAM software. The aim of this study is to improve our understanding about how different parts of a building can experience varying concentrations of the airborne viruses under different circumstances of release and mitigation strategies. Results indicate that unventilated stairwells can have significantly higher concentrations of airborne viruses. The mitigation strategies of morning and evening flushing of conditioned zones were not found to be very effective. Instead, a constant high percentage of outdoor air in the supply mix, and the use of masks, portable HEPA air cleaners, MERV 13 or higher HVAC air filters, and ultraviolet germicidal irradiation disinfection were effective strategies to prevent airborne viral contamination in the majority of the simulated office building.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Experimental Plan for the Vermiculite Study

Homes in which vermiculite, which can contain asbestos, is present are often deferred under the DOE Weatherization Assistance Program (WAP) because of uncertainty in how to safely weatherize such homes from a client and worker perspective and the potential costs associated with alternative approaches. Recognizing this situation, the Department of Energy (DOE) tasked the Oak Ridge National Laboratory (ORNL) to perform a research project that scientifically identifies the asbestos exposure risks in weatherizing homes with existing vermiculite insulation. Current approaches being used by Grantees and Subgrantees to weatherize homes with existing vermiculite insulation were identified as part of the development of this experimental plan based on a review of Grantee Health and Safety Plans and communications with weatherization program staff from seven states. Other than deferral, these approaches include the following:1.) Abating (i.e., removing) the existing vermiculite using funding sources other than WAP (e.g., state funds, utility funds, the Zonolite Attic Insulation Trust Fund, and possibly homeowner contributions) because abatement is not allowed using WAP funds per Weatherization Program Notice (WPN) 17-7. 2.) Weatherizing the house as normal after testing reveals that the vermiculite contains less than 1% asbestos. 3.) Avoiding areas of the house where vermiculite is installed and weatherizing the remaining areas of the house as normal. 4.) Encapsulating the existing vermiculite insulation in an attic by blowing cellulose or other insulation over it. 5.) Weatherizing the areas of the house where vermiculite is installed using unique/alternative approaches developed specifically for that house. Blower door testing is also impacted by the presence of vermiculite due to the concern of bringing asbestos fibers into the space. Some states address this by performing pressurized blower door tests, whereas other states prohibit blower door testing entirely when vermiculite is present. This research project will focus on gathering data on home occupant and weatherization worker exposures to asbestos before, during, and/or after the weatherization of the homes containing vermiculite insulation using five of the six approaches identified above. Abatement of the existing vermiculite insulation will not be studied because it is not allowed using WAP funding per WPN 17-7 and, thus, is not a sustainable approach for WAP.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Air Return Strategies and Airborne SARS-CoV-2

Dedicated ducted air return per zone for heating, ventilating, and air-conditioning (HVAC) systems is sometimes claimed to be a superior technique over plenum return strategy from the viewpoint of exposure reduction to airborne pathogens. While both the return strategies have advantages, there is limited evidence in the literature as to which strategy is superior merely from a standpoint of building vulnerability to airborne contaminants. We performed multizonal airborne contaminant dispersion modelling using CONTAM to simulate the overall building vulnerability to airborne SARS-CoV-2 aerosols when released in an office building and evaluated the two air return strategies. Results showed that for ducted returns, maintaining negative pressure in the release zone coupled with 100% outdoor air supply can greatly reduce overall building vulnerability. However, for a building maintained under a slight positive pressure and a recirculated air percentage as low as 31%, ducted returns do not necessarily outperform plenum returns in terms of overall building vulnerability to airborne pathogens. Building-specific details and factors that are not easily represented with multizone modelling are important, making general preferential statements for either strategy difficult to make. Insights from this study can guide new construction and retrofits of buildings both during and after the COVID-19 pandemic with the aim of safe re-occupancy of buildings while keeping the buildings resilient against potential future epidemics spread by airborne agents.

Shrestha, Prateek↗
DOE OSTI2021

Metrics for Interzonal Dispersion Assessment of Airborne SARS-CoV-2 Within Office Buildings

High ventilation rate is increasingly considered as a mitigation strategy in the rapid spread of COVID-19 in existing buildings in addition to other options like UVGI and added filtration. However, this and other similar measures may also impact energy use and the efficiency of the buildings in which they are installed. Without concrete metrics, the impact of all these potential changes to the system cannot be properly assessed relative to the other impacts the measures might have, including additional energy use, added operation and maintenance costs, and reduced system life. Multizone airflow and contaminant transport simulations involving parameters such as infiltration rate, system configuration, and level of occupancy can provide critical information on relative risk distribution within a building. In this study, prototype airflow models are used to assess the degree to which ventilation-related measures can mitigate the spread of a virus like SARS-CoV-2 in a similar way that prototype energy models are used to study energy efficiency measures. A new detailed medium-sized office building prototype model is developed using the CONTAM software to represent contaminant transport in buildings like those modeled by the U.S. Department of Energy’s detailed medium office prototype model. The goal of this study is to generate a set of suitable metrics that will give a whole-building picture of airborne SARS-CoV-2 virus distributions across the different zones of the building under different parameters and scenarios.

DeGraw, Jason↗