David W. Winiarski

Infiltration Modeling Guidelines for Commercial Building Energy Analysis

This report presents a methodology for modeling air infiltration in EnergyPlus to account for envelope air barrier characteristics. Based on a review of various infiltration modeling options available in EnergyPlus and sensitivity analysis, the linear wind velocity coefficient based on DOE-2 infiltration model is recommended. The methodology described in this report can be used to calculate the EnergyPlus infiltration input for any given building level infiltration rate specified at known pressure difference. The sensitivity analysis shows that EnergyPlus calculates the wind speed based on zone altitude, and the linear wind velocity coefficient represents the variation in infiltration heat loss consistent with building location and weather data.

A quasi-steady-state model of attic heat transfer with radiant barriers

Abstract During the cooling season, heat transfer from the attic into the conditioned space of a residence can represent a significant portion of the total envelope heat transfer. Radiant barriers are one method used to reduce this heat transfer. A quasi-steady-state model was developed for predicting attic heat transfer in residences with radiant barrier systems. The model was used to estimate the reduction in cooling load that would occur with a radiant barrier and to identify important construction and environmental parameters that influence this cooling load reduction. The models output consisted of hourly ceiling heat fluxes inside the house based on hourly weather data inputs. Model results were compared with detailed experimental results from two small test houses. The model predicted typical summer heat flux reductions of between 35 and 43% with different radiant barrier configurations and levels of insulation. These compared to measured heat flux reductions of between 29 and 37% in attics under the same conditions. Sensitivity studies were also conducted to show the effect of uncertainty in several of the important physical attic parameters on the final heat flow predictions of the model.

Efficient Low-Lift Cooling with Radiant Distribution, Thermal Storage, and Variable-Speed Chiller Controls— Part I: Component and Subsystem Models

Component and subsystem models used to evaluate the performance of a low-lift cooling system are described. An air-cooled chiller, a hydronic radiant distribution system, variable-speed control, and peak-shifting controls are modeled. A variable-speed compressor that operates over 20:1 speed range and pressure ratios ranging from one to six is at the heart of the chiller. Condenser fan and chilled-water pump motors have independent speed controls. The load-side distribution is modeled from the refrigerant side of the evaporator to the conditioned zone as a single subsystem controlled by chilled-water flow rate for a specified instantaneous cooling load. Performance of the same chiller when operating with an all-air distribution system is also modeled. The compressor, condenser fan, and chilled-water pump motor speeds that achieve maximum coefficient of performance (COP) at a given condition are solved at each point on a grid of load and outdoor temperature. A variable-speed dehumidification subsystem is modeled and simulated as part of a dedicated outdoor air system to condition the ventilation air. A companion paper evaluates the annual cooling system energy use and potential energy savings to be gained by integrating radiant cooling, cool storage, and variable-speed compressor and transport motor controls.

Efficient Low-Lift Cooling with Radiant Distribution, Thermal Storage, and Variable-Speed Chiller Controls—Part II: Annual Use and Energy Savings

This paper evaluates the cooling efficiency improvements that can be achieved by integrating radiant cooling, cool storage, and variable-speed compressor and transport motor controls. Performance estimates of a baseline system and seven useful combinations of these three efficient low-lift inspired cooling technologies are reported. The technology configurations are simulated in a prototypical office building with three levels of envelope and balance-of-plant performance: standard-, mid- and high-performance, and in five climates. The standard performance level corresponds to ANSI/ASHRAE/IESNA Standard 90.1-2004 Energy Standard for Buildings Except Low-Rise Residential Buildings (ASHRAE 2004a). From the savings estimates for an office building prototype in five representative climates, estimates of national energy saving technical potential are developed. Component and subsystem models used in the energy simulations are developed in a companion paper.

Screening analysis for EPACT-covered commercial HVAC and water-heating equipment

PNNL, under direction from DOE, conducted a screening analysis to determine the energy savings potential from the efficiency levels for commercial HVAC and water-heating equipment listed in Standard 90.1-1999, as well as the potential from several higher efficiency levels. We estimated the annual energy consumption for each type of equipment, at various efficiency levels, through engineering simulations for seven building types in 11 U.S. locations. We also conducted an economic analysis to identify the efficiency levels that would provide the highest value of economic benefits. From 2004 through 2030, the estimated national energy savings for the equipment meeting the Standard 90.1-1999 efficiency levels is about 3.8 exajoules (EJ) (3.6 quads). 1 The total estimated carbon emissions reduction is 52 MMtons.

Review of Pre- and Post-1980 Buildings in CBECS - HVAC Equipment

PNNL was tasked by DOE to look at HVAC systems and equipment for Benchmark buildings based on 2003 CBECS data. This white paper summarizes the results of PNNL’s analysis of 2003 CBECS data and provides PNNL’s recommendations for HVAC systems and equipment for use in the Benchmark buildings.

Cost-Effective Integration of Efficient Low-Lift Base Load Cooling Equipment

The long-term goal of DOE’s Commercial Buildings Integration subprogram is to develop cost-effective technologies and building practices that will enable the design and construction of net Zero Energy Buildings — commercial buildings that produce as much energy as they use on an annual basis — by 2025. To support this long-term goal, DOE further called for — as part of its FY07 Statement of Needs — the development by 2010 of “five cost-effective design technology option sets using highly efficient component technologies, integrated controls, improved construction practices, streamlined commissioning, maintenance and operating procedures that will make new and existing commercial buildings durable, healthy and safe for occupants.” In response, PNNL proposed and DOE funded a scoping study investigation of one such technology option set, low-lift cooling, that offers potentially exemplary HVAC energy performance relative to ASHRAE Standard 90.1-2004. The primary purpose of the scoping study was to estimate the national technical energy savings potential of this TOS.

Analysis of Potential Benefits and Costs of Adopting a Commercial Building Energy Standard in South Dakota

The state of South Dakota is considering adopting a commercial building energy standard. This report evaluates the potential costs and benefits to South Dakota residents from requiring compliance with the most recent edition of the ANSI/ASHRAE/IESNA 90.1-2001 Energy Standard for Buildings except Low-Rise Residential Buildings. These standards were developed in an effort to set minimum requirements for the energy efficient design and construction of new commercial buildings. The quantitative benefits and costs of adopting a commercial building energy code are modeled by comparing the characteristics of assumed current building practices with the most recent edition of the ASHRAE Standard, 90.1-2001. Both qualitative and quantitative benefits and costs are assessed in this analysis. Energy and economic impacts are estimated using results from a detailed building simulation tool (Building Loads Analysis and System Thermodynamics [BLAST] model) combined with a Life-Cycle Cost (LCC) approach to assess corresponding economic costs and benefits.

Analysis of Potential Benefits and Costs of Adopting ASHRAE Standard 90.1-1999 as a Commercial Building Energy Code in Michigan

The state of Michigan is considering adpoting ASHRAE 90.1-1999 as its commercial building energy code. In an effort to evaluate whether or not this is an appropraite code for the state, the potential benefits and costs of adopting this standard are considered. Both qualitative and quantitative benefits are assessed. The energy simulation and economic results suggest that adopting ASHRAE 90.1-1999 would provide postitive net benefits to the state relative to the building and design requirements currently in place.

Technology Demonstration of Magnetically-Coupled Adjustable Speed Drive Systems

Adjustable speed drive technologies have the ability to precisely control motor system output and produce a number of benefits including energy and demand savings. This paper examines the performance and cost effectiveness of a specific class of ASDs called magnetically coupled adjustable speed drives, which use the strength of a magnetic field to control the amount of torque transferred between motor and drive shaft.