Commercial Building Applications Research Articles

A model predictive control optimization environment for real-time commercial building application

A model predictive control (MPC) environment is described. The environment integrates Matlab and EnergyPlus with a modified particle swarm optimizer to predict optimal building control strategies. A supporting framework is described which couples the environment to a building automation system, allowing real-time optimization considering operator overrides and updated weather forecasts. Challenges unique to integration with EnergyPlus for real-time optimization are discussed. Application of the environment is demonstrated in two simulation cases. First, the environment is used to determine hourly cooling set points minimizing daily energy cost for EnergyPlus's Benchmark Large Office building. Results suggest 5% cost savings during the study period. Second, the environment is used to determine hourly supply water temperature and circulator availability that minimize daily energy consumption for a small office building having a thermally activated building system (TABS). Compared to the base case, energy savings up to 54% are reported, with often improved occupant comfort.

Insulation Investment = Energy Savings and Exceptional Financial Returns

Mechanical insulation from an energy savings investment perspective in commercial building and industrial applications, although important to facility operations and manufacturing processes, is often overlooked and undervalued. Whose fault is that, and why is that? For a variety of reasons, the knowledge base of mechanical insulation has eroded over the last 10 years. Combine that with insulation being taken for granted as to providing a simple one-time payback and you have identified the problem. This article will explore this problem and provide evidence; processes and resources for de-mystifying this proven, but often forgotten energy savings and emission reduction technology, simply known as insulation. With today's high cost of energy, our dependency on foreign energy sources; and our renewed focus on the environment, there has never been a more important time to think about insulation differently. You will leave asking yourself why you have not taken advantage of this technology before.

Optimal Technology Selection and Operation of Commercial-Building Microgrids

The deployment of small ( < 1-2 MW ) clusters of generators, heat and electrical storage, efficiency investments, and combined heat and power (CHP) applications (particularly involving heat-activated cooling) in commercial buildings promises significant benefits but poses many technical and financial challenges, both in system choice and its operation; if successful, such systems may be precursors to widespread microgrid deployment. The presented optimization approach to choosing such systems and their operating schedules uses Berkeley Lab's Distributed Energy Resources Customer Adoption Model (DER-CAM), extended to incorporate electrical and thermal storage options. DER-CAM chooses annual energy bill minimizing systems in a fully technology-neutral manner. An illustrative example for a hypothetical San Francisco hotel is reported. The chosen system includes one large reciprocating engine and an absorption chiller providing an estimated 11% cost savings and 8% carbon emission reductions under idealized circumstances.

Removing Unwanted Heat in Lightweight Buildings Using Phase Change Materials in Building Components: Simulation Modelling for PCM Plasterboard

Phase change materials (PCMs) can store much larger amounts of thermal energy per unit mass than conventional building materials and can be used to add thermal stability to lightweight construction without adding physical mass. This paper reviews how PCMs could be incorporated in building materials, particularly in passive applications. A simulation study using IES Virtual Environment package ‘Apache’ was carried out on PCM impregnated plasterboard, investigating various fusion temperatures of the PCM during night, day, and week-long test durations in hot weather conditions. Different ventilation rates and alternative conductivity values of the gypsum in the plasterboard were tested. It was shown that use of PCMs has significant advantages for both commercial and residential building applications, provided sufficient night ventilation is allowed.

Effect of web stiffness on the bending behaviour of timber composite I-beams

The design of timber I-beams with glued OSB web is currently based on simplified analytical model and experimental works. At the ultimate limit state, normal forces in the flanges and shear stresses in the web govern the load-carrying capacity of the beams. Applications in industrial or commercial buildings requires cross-section with greater height. In this paper, the effect of the slenderness of the web is analysed through an experimental program and a finite element model. For beams with finger-jointed flanges and butt-joints between web panels, the effective stiffness and the bending capacity are evaluated considering a web of 12 mm in thickness and height varying from 225 to 495 mm. The experimental values of the effective stiffness were compared to the theoretical evaluation taking into account the shear deformations of the web. For highest heights of the cross-section, the results shown that the ultimate capacity is governed by the plate behaviour of the web, resulting in the failure of the glued joint. On this basis, the internal behaviour is examined using a three-dimensional finite element modelling. The effect of the mains parameters such as the relative stiffness of the components and the gap between web panels is investigated. The stress concentration in the area of the web joint is analysed and a new design criterion is calibrated.

Developing Air-Cooled LiBr Absorption for Light Commercial Combined Heat and Power Applications

This paper summarizes the development status of air-cooled lithium bromide (LiBr)-water absorption chillers to guide future efforts to develop chillers for combined heat and power (CHP) applications in US light commercial buildings (typically 30 to 500 kWTh [10 to 150 RT]). The key technical barrier to air-cooled operation is the increased tendency for LiBr solutions to crystallize in the absorber when heat-rejection temperatures rise. Air-cooled LiBr-water absorption chillers/coolers have been analyzed, designed, and prototype- tested since at least the mid-1970s, primarily in Japan, the US, and Europe, for solar-fired and direct-fired applications. Developers have used several approaches, including chemistry changes to inhibit crystallization, improving heat and mass transfer to lower overall temperature lift, modifying the thermodynamic cycle, combining absorption with vapor compression to lower the temperature lift for each system, and advanced control systems to sense the onset of crystallization and take corrective action. Most air-cooled LiBr absorption development efforts of the past have not adequately addressed operation at high ambient temperatures. Vapor-compression equipment, which can typically deliver over 85% of rated capacity in ambient temperatures up to 50°C (120°F), sets the benchmark for performance expectations in US light-commercial markets. Several alternative design approaches that are not documented in the open literature are briefly considered here. Of these, the most promising appears to be intermittent evaporative cooling. If evaporative cooling is used only at extreme ambient temperatures, it may be possible to avoid many of the disadvantages of full-time evaporative cooling systems, such as high water consumption, high maintenance requirements, and risk of harboring Legionella. However, further evaluation of this approach is needed before drawing firm conclusions. There are other potentially viable approaches to eliminating the need for cooling towers in light-commercial CHP applications, such as LiBr absorption with ground-coupled heat rejection, ammonia-water absorption, adsorption/chemisorption, and Rankine cycles driving vapor-compression equipment. These approaches were outside the scope of our investigation but may warrant consideration.

Application issues for large-area electrochromic windows in commercial buildings : Lee, E. S. and DiBartolomeo, D. L. Solar Energy Materials and Solar Cells, 2002, 71, (4), 465–491

Projections of performance from small-area devices to large-area windows and enterprise marketing have created high expectations for electrochromic glazings. As a result, this paper seeks to precipitate an objective dialog between material scientists and building-application scientists to determine whether actual large-area electrochromic devices will result in significant performance benefits and what material improvements are needed, if any, to make electrochromics more practical for commercial building applications. Few in-situ tests have been conducted with large-area electrochromic windows applied in buildings. This study presents monitored results from a full-scale field test of large-area electrochromic windows to illustrate how this technology will perform in commercial buildings. The visible transmittance (Tv) of the installed electrochromic ranged from 0.11 to 0.38. The data are limited to the winter period for a south-east-facing window. The effect of actual device performance on lighting energy use, direct sun control, discomfort glare, and interior illumination is discussed. No mechanical system loads were monitored. These data demonstrate the use of electrochromics in a moderate climate and focus on the most restrictive visual task: computer use in offices. Through this small demonstration, we were able to determine that electrochromic windows can indeed provide unmitigated transparent views and a level of dynamic illumination control never before seen in architectural glazing materials. Daily lighting energy use was 6-24 percent less compared to the11 percent-glazing, with improved interior brightness levels. Daily lighting energy use was 3 percent less to 13 percent more compared to the 38 percent-glazing, with improved window brightness control. The electrochromic window may not be able to fulfill both energy-efficiency and visual comfort objectives when low winter direct sun is present, particularly for computer tasks using cathode-ray tube (CRT) displays. However, window and architectural design as well as electrochromic control options are suggested as methods to broaden the applicability of electrochromics for commercial buildings. Without further modification, its applicability is expected to be limited during cold winter periods due to its slow switching speed.

Application issues for large-area electrochromic windows in commercial buildings

Projections of performance from small-area devices to large-area windows and enterprise marketing have created high expectations for electrochromic glazings. As a result, this paper seeks to precipitate an objective dialog between material scientists and building-application scientists to determine whether actual large-area electrochromic devices will result in significant performance benefits and what material improvements are needed, if any, to make electrochromics more practical for commercial building applications. Few in situ tests have been conducted with large-area electrochromic windows applied in buildings. This study presents monitored results from a full-scale field test of large-area electrochromic windows to illustrate how this technology will perform in commercial buildings. The visible transmittance ( T v) of the installed electrochromic ranged from 0.11 to 0.38. The data are limited to the winter period for a south-east-facing window. The effect of actual device performance on lighting energy use, direct sun control, discomfort glare, and interior illumination is discussed. No mechanical system loads were monitored. These data demonstrate the use of electrochromics in a moderate climate and focus on the most restrictive visual task: computer use in offices. Through this small demonstration, we were able to determine that electrochromic windows can indeed provide unmitigated transparent views and a level of dynamic illumination control never before seen in architectural glazing materials. Daily lighting energy use was 6–24% less compared to the 11%-glazing, with improved interior brightness levels. Daily lighting energy use was 3% less to 13% more compared to the 38%-glazing, with improved window brightness control. The electrochromic window may not be able to fulfill both energy-efficiency and visual comfort objectives when low winter direct sun is present, particularly for computer tasks using cathode-ray tube (CRT) displays. However, window and architectural design as well as electrochromic control options are suggested as methods to broaden the applicability of electrochromics for commercial buildings. Without further modification, its applicability is expected to be limited during cold winter periods due to its slow switching speed.

Geothermal Heat Pump Performance and Utility Programs in the United States

Geothermal heal pump systems are a promising new energy technology that has shown rapid increase in usage over the past 10 years in the United States. These systems offer substantial benefits to consumers and utilities in energy (kWh) and demand (kW) savings. The purpose of this study was to determine what existing monitored data were available mainly from electric utilities on heal pump performance, energy savings, and demand reduction for residential, school, and commercial building applications. Information was developed on the status of electric utility marketing programs, barriers to market entry, incentive programs, and benefits.

Daylighting for energy conservation in the tropics: The Lumen method and the OTTV

We describe a potential use of the Lumen Method for daylighting applications in commercial buildings in a tropical climate. Calculations of the overall thermal-transfer value show that daylighting and judicious choice of the composition of the building envelope optimize lighting and minimize air-conditioning loads in buildings.

A thin film polyimide based capacitive type relative humidity sensor

A capacitive type relative humidity sensor utilizing newly developed cross-linked fluorinated polyimide has been fabricated using thin film technology and evaluated for commercial building and factory applications. The sensor showed a good initial performance with less than 1% r.h. hysteresis and a 0 ± 0.1% r.h./°C temperature coefficient of capacitance along with good stability especially under high temperature and high humidity conditions. Also, because of the inherent chemical resistance of the polyimide, good sensor stability when subjected to volatile environments has been demonstrated.

The potential of radiant panels as terminal heaters in solar space heating applications

Appreciable attention has recently been paid to the use of radiant heating panels for solar space heating applications in residential and commercial buildings. The present work describes the development of a simple and handy microcomputer theoretical simulation model, suitable to investigate the advantages and performance of using radiant heating, low operating temperature panels in solar space heating applications.

Optimization of Thermal Mass in Commercial Building Applications

Based on results from a one-year intensive monitoring project of a Northern New York commercial building with energy-conserving design features, a thermal storage project was undertaken to optimize the design of a thermal mass storage system for a moderately sized commercial building and transfer the technology to the commercial building sector. A generic commercial building design of 27,000 square feet (2508 m2) was selected for the optimization project. Several different types of thermal mass designs were considered as potentially practical for a commercial building. These included a “sandmass” design such as the mass incorporated in the previously monitored commercial building mentioned above, a foundation slab of sufficient thickness to serve as a significant building thermal mass, and the use of poured cement in interior wall and floor construction. Five different office building thermal designs were selected which represented various thermal storage features and two different building insulation levels (R10 and R20). Energy performance of the five thermal designs was modeled in building energy simulations using DOE 2.1C (Department of Energy 2.1C) energy simulation code. Results of the simulations showed a reduction in peak heating and cooling loads would be experienced by the HVAC equipment. The reduction in peak heating and cooling loads was anticipated because thermal mass within a building serves to average peak heating and cooling loads due to the capacity of the thermal mass to store and release heat from all building heat sources over a period of time. Peak heating loads varied from 1972 kBtuh (578 kW) for the R-10 light construction base case to a minimum of 980 kBtuh (287 kW) for the R-20 heavy construction sandmass storage case. Peak cooling loads dropped from 772 kBtuh (226 kW) for the R-20 light construction case to 588 kBtuh (172 kW) for the R-20 heavy construction sandmass storage case. Results of the simulations also showed annual energy savings for the high thermal mass designs. Energy savings varied from 20 percent [16.0 kBtu/ft2 (50 kWh/m2)] for the R-10 high thermal mass design in comparison to its base case to 18 percent [12.2 kBtu/ft2 (39 kWh/m2)] for the R-20 high thermal mass design in comparison to its base case. The annual energy savings are due to the ability of the thermal mass to absorb heat from all sources of heat generation (lights, occupancy, solar, and auxiliary) during occupied periods and release the heat during unoccupied periods. An optimized thermal design was developed based on results from the DOE 2.1C simulations. The initial cost for the optimized thermal storage design is lower than the initial costs for light construction office buildings, since the lower initial cost of the down-sized HVAC system for the optimized thermal storage design more than offsets the increased cost of wall and floor systems incorporated in the optimized design. Annual energy savings are realized from the high thermal mass system in both cooling and heating modes due to the interaction of building HVAC systems operation in the simulated 27000 ft2 (2508 m2) office building. Annual operating savings of $3781 to $4465 per year are estimated based on simulation results.

Engineering principles and concepts for active solar systems

This current document represents the culmination of an eight-year effort to compile a comprehensive state-of-the-art reference and instructional tool for practicing design professionals, architects, and engineers. It is intended to cover all phases of the design and installation of active solar energy systems for buildings. Although it contains many design guidelines, the emphasis is on providing sufficient knowledge of how these systems work to allow an engineer or architect to make well-informed decisions. It is aimed primarily at commercial building applications, but most of the material is also applicable to residential buildings. The book is divided into 13 chapters: energy and buildings: a perspective; energy use, cost, and load calculations in commercial buildings; fundamentals: solar energy, climate, and human comfort; active solar heating and cooling systems; principal components of active systems; active subsystem components; active system design and sizing methods; detailed design, construction, and installation considerations; collectors: specification and prebidding; start-up and acceptance testing; developing an operations and maintenance manual; instrumentation and monitoring; construction costs. Each chapter has been indexed separately for inclusion on the Energy Data Base. 241 references.