Model Validation and Testing: The Methodological Foundation of ASHRAE Standard 140; Preprint

Ideally, whole-building energy simulation programs model all aspects of a building that influence energy use and thermal and visual comfort for the occupants. An essential component of the development of such computer simulation models is a rigorous program of validation and testing. This paper describes a methodology to evaluate the accuracy of whole-building energy simulation programs. The methodology is also used to identify and diagnose differences in simulation predictions that may be caused by algorithmic differences, modeling limitations, coding errors, or input errors. The methodology has been adopted by ANSI/ASHRAE Standard 140 (ANSI/ASHRAE 2001, 2004), Method of Test for the Evaluation of Building Energy Analysis Computer Programs. A summary of the method is included in the ASHRAE Handbook of Fundamentals (ASHRAE 2005). This paper describes the ANSI/ASHRAE Standard 140 method of test and its methodological basis. Also discussed are possible future enhancements to Standard 140 and related research recommendations

Home energy rating system building energy simulation test (HERS BESTEST): Volume 1, Tier 1 and Tier 2 tests user's manual

The Home Energy Rating System (HERS) Building Energy Simulation Test (BESTEST) is a method for evaluating the credibility of software used by HERS to model energy use in buildings. The method provides the technical foundation for ''certification of the technical accuracy of building energy analysis tools used to determine energy efficiency ratings,'' as called for in the Energy Policy Act of 1992 (Title I, subtitle A,l Section 102, Title II, Part 6, Section 271). Certification is accomplished with a uniform set of test cases that facilitate the comparison of a software tool with several of the best public-domain, state-of-the-art building energy simulation programs available in the United States. This set of test cases represents the Tier 1 and Tier 2 Tests for Certification of Rating Tools as described in DOE 10 CFR Part 437 and the HERS Council Guidelines for Uniformity (HERS Council). A third Tier of tests not included in this document is also planned

Building Energy Simulation Test for Existing Homes (BESTEST-EX) (Presentation)

This presentation discusses the goals of NREL Analysis Accuracy R&D; BESTEST-EX goals; what BESTEST-EX is; how it works; 'Building Physics' cases; 'Building Physics' reference results; 'utility bill calibration' cases; limitations and potential future work. Goals of NREL Analysis Accuracy R&D are: (1) Provide industry with the tools and technical information needed to improve the accuracy and consistency of analysis methods; (2) Reduce the risks associated with purchasing, financing, and selling energy efficiency upgrades; and (3) Enhance software and input collection methods considering impacts on accuracy, cost, and time of energy assessments. BESTEST-EX Goals are: (1) Test software predictions of retrofit energy savings in existing homes; (2) Ensure building physics calculations and utility bill calibration procedures perform up to a minimum standard; and (3) Quantify impact of uncertainties in input audit data and occupant behavior. BESTEST-EX is a repeatable procedure that tests how well audit software predictions compare to the current state of the art in building energy simulation. There is no direct truth standard. However, reference software have been subjected to validation testing, including comparisons with empirical data

Building Energy Simulation Test for Existing Homes (BESTEST-EX) Methodology: Preprint

The test suite represents a set of cases applying the new Building Energy Simulation Test for Existing Homes (BESTEST-EX) Methodology developed by NREL. (Judkoff et al. 2010a). The NREL team developed the test cases in consultation with the home retrofit industry (BESTEST-EX Working Group 2009), and adjusted the test specifications in accordance with information supplied by a participant with access to large utility bill datasets (Blasnik 2009)

U-Pb Ages of Secondary Silica at Yucca Mountain, Nevada: Implications for the Paleohydrology of the Unsaturated Zone

U, Th, and Pb isotopes were analyzed in layers of opal and chalcedony from individual millimeter- to centimeter-thick calcite and silica coatings at Yucca Mountain, Nevada, USA, a site that is being evaluated for a potential high-level nuclear waste repository. These calcite and silica coatings on fractures and in lithophysal cavities in Miocene-age tuffs in the unsaturated zone (UZ) precipitated from descending water and record a long history of percolation through the UZ. Opal and chalcedony have high concentrations of U (10 to 780 ppm) and low concentrations of common Pb as indicated by large values of {sup 206}Pb/{sup 204}Pb (up to 53,806), thus making them suitable for U-Pb age determinations. Interpretations of U-Pb isotopes in opal samples at Yucca Mountain are complicated by the incorporation of excess {sup 234}U at the time of mineral formation, resulting in reverse discordance of U-Pb ages. However, the {sup 207}Pb/{sup 235}U ages are much less affected by deviation from initial secular equilibrium and provide reliable ages of most silica deposits between 0.6 and 9.8 Ma. For chalcedony subsamples showing normal age discordance, these ages may represent minimum times of deposition. Typically, {sup 207}Pb/{sup 235}U ages are consistent with the microstratigraphy in the mineral coating samples, such that the youngest ages are for subsamples from outer layers, intermediate ages are from inner layers, and oldest ages are from innermost layers. {sup 234}U and {sup 230}Th in most silica layers deeper in the coatings are in secular equilibrium with {sup 238}U, which is consistent with their old age and closed system behavior during the past 0.5 m.y. U-Pb ages for subsamples of silica layers from different microstratigraphic positions in individual calcite and silica coating samples collected from lithophysal cavities in the welded part of the Topopah Spring Tuff yield slow long-term average depositional rates of 1 to 5 mm/m.y. These data imply that the deeper parts of the UZ at Yucca Mountain maintained long-term hydrologic stability over the past 10 m.y. despite significant climate variations. U-Pb ages for subsamples of silica layers from different microstratigraphic positions in individual calcite and silica coating samples collected from fractures in the welded part of the overlying Tiva Canyon Tuff indicate larger long-term average depositional rates up to 23 mm/m.y. and an absence of recently deposited materials (ages of outermost layers are 3-5 Ma). These differences between the characteristics of the coatings for samples from the shallower and deeper parts of the UZ may indicate that the nonwelded tuffs (PTn), located between the welded parts of the Tiva Canyon and Topopah Spring Tuffs, play an important role in moderating UZ flow

Testing the Concept of Drift Shadow at Yucca Mountain, Nevada

If proven, the concept of drift shadow, a zone of reduced water content and slower ground-water travel time beneath openings in fractured rock of the unsaturated zone, may increase performance of a proposed geologic repository for high-level radioactive waste at Yucca Mountain. To test this concept under natural-flow conditions present in the proposed repository horizon, isotopes within the uranium-series decay chain (uranium-238, uranium-234, and thorium-230, or {sup 238}U-{sup 234}U-{sup 230}Th) have been analyzed in samples of rock from beneath four naturally occurring lithophysal cavities. All samples show {sup 234}U depletion relative to parent {sup 238}U, indicating varying degrees of water-rock interaction over the past million years. Variations in {sup 234}U/{sup 238}U activity ratios indicate that depletion of {sup 234}U relative to {sup 238}U can be either smaller or greater in rock beneath cavity floors relative to rock near cavity margins. These results are consistent with the concept of drift shadow and with numerical simulations of meter-scale spherical cavities in fractured tuff. Differences in distribution patterns of {sup 234}U/{sup 238}U activity ratios in rock beneath the cavity floors are interpreted to reflect differences in the amount of past seepage into lithophysal cavities, as indicated by the abundance of secondary mineral deposits present on the cavity floors

International Energy Agency Building Energy Simulation Test and Diagnostic Method (IEA BESTEST) Multi-Zone Non-Airflow In-Depth Diagnostic Cases: MZ320 -- MZ360

This report documents a set of diagnostic test cases for multi-zone heat transfer models. The methodology combines empirical validation, analytical verification, and comparative analysis techniques

IEA BESTEST Multi-Zone Non-Airflow In-Depth Diagnostic Cases: Preprint

This paper documents a set of in-depth diagnostic test cases for multi-zone heat transfer models that do not include the heat and mass transfer effects of airflow between zones. The multi-zone non-airflow test cases represent an extension to IEA BESTEST (Judkoff and Neymark 1995a)

IEA BESTEST Multi-Zone Non-Airflow In-Depth Diagnostic Cases: Preprint

This paper documents a set of in-depth diagnostic test cases for multi-zone heat transfer models that do not include the heat and mass transfer effects of airflow between zones. The multi-zone non-airflow test cases represent an extension to IEA BESTEST (Judkoff and Neymark 1995a)