Josh Apte

Bio: Josh Apte is an academic researcher. The author has contributed to research in topics: Daylighting & Renewable energy. The author has an hindex of 1, co-authored 1 publications receiving 51 citations.

Zero Energy Windows

Abstract: LBNL-60049 To be presented and published in the Proceedings of the 2006 ACEEE Summer Study on Energy Efficiency in Buildings, August 13-18, 2006, Pacific Grove, CA. Zero Energy Windows Dariush Arasteh, Steve Selkowitz, Josh Apte Lawrence Berkeley National Laboratory Marc LaFrance U.S. Department of Energy This work is supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Building Technologies, U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Electrochromic dynamic windows for office buildings

Abstract: The next generation of advanced fenestration products includes dynamic electrochromic (EC) windows which can modulate the solar energy entering a building by application of an applied voltage. The windows can be switched from 62% visible transmittance (Tvis), 0.47 solar heat gain coefficient (SHGC) to a fully tinted state with ⩽2% Tvis, 0.09 SHGC. EC windows save energy in buildings – the total energy use for an eight story ASHRAE 90.1 2007 commercial office building with EC windows was modeled using the eQuest building simulation program and compared with the energy use of the same building with a variety of static glazings. The simulations were carried out in three US climate zones, encompassing a broad range of environmental exposure conditions from hot and dry (Arizona) to very cold (Minnesota). For all climate zones, building energy savings with EC glass were ⩾45% when compared to single pane static glazings common in existing building stock. When EC glass was compared to ASHRAE 90.1 2007 code compliant glazings, energy savings greater than 20% were calculated for the same building configuration. Optimum EC window control and performance strategies were derived from the modeling results. The EC glass and dimmable electric lights were synergistically controlled to maximize the use of natural daylighting and minimize electricity for lighting. Since EC glass can tint to ⩽2%, shades and/or blinds are not required for glare reduction, and building occupants always have a comfortable working environment and an unobstructed view and connection to the outdoors. All static glazing systems were assumed to have manual shading devices that are pulled by building occupants when glare becomes uncomfortable. For integrated building control systems, the peak load is significantly reduced when dynamic glazings are part of the building envelope. Consequently, chiller costs are lower, and the upfront capital costs for new building construction are reduced. Another key benefit of EC glass, elucidated by the simulations is reduction of CO2 emissions. EC glass reduces peak load carbon emissions by as much as 35% in new construction and 50% in renovation projects.

A validation of the Radiance three-phase simulation method for modeling annual daylight performance of optically-complex fenestration systems

Abstract: A new capability that enables annual simulation of optically complex fenestration systems has been added to Radiance. The method relies on bidirectional scattering distribution function (BSDF) input data, which are used in an efficient matrix calculation to compute time-step performance given TMY data. The objective of this study was to explain the value of this capability to designers and developers of innovative daylighting systems and to demonstrate its speed and accuracy via comparisons of simulated to measured illuminance data for a daylight-redirecting optical louver system. The method was shown to provide valid results that accurately replicate real-world conditions with an absolute mean bias error below 13% and a root mean square error below 23%. Routine application of this new capability will not be hindered by slow computational speed for illuminance calculations. Instead, the capability will be dependent on the availability of BSDF data for daylighting, shading and fenestration systems.