Small Commercial Buildings Research Articles

Cost-effective retrofit technology for reducing peak power demand in small and medium commercial buildings

This article describes a cost-effective retrofit technology that uses collective control of multiple rooftop air-conditioning units to reduce the peak power consumption of small and medium commercial buildings. The proposed control uses a model of the building and air-conditioning units to select an operating schedule for the air-conditioning units that maintains a temperature set-point subject to a constraint on the number of units that may operate simultaneously. A prototype of this new control system was built and deployed in a large gymnasium to coordinate four rooftop air-conditioning units. Based on data collected while operating this prototype, it is estimated that the cost savings achieved by reducing peak power consumption is sufficient to repay the cost of the prototype within a year.

Modeling of Thermal Mass in a Small Commercial Building and Potential Improvement by Applying TABS

With a resistor-capacitor model built in Matlab/Simulink, the role of envelope/interior thermal mass (eTM/iTM) in a small commercial building is investigated systematically. It concludes that light-weight concrete is a little worse than normal-weight concrete but much better than wood as eTM or iTM for controlling operative temperature variation in the building. In order to combine the advantages of radiant cooling/heating with the heat storage of massive building structure, an attractive technique called TABS (thermally activated building systems) is applied to the building to investigate the potential improvement. Simulations demonstrate that TABS can keep the operative temperature level around the comfort zone with small variations. As TABS is a low-temperature heating and high-temperature cooling technique, it suggests that natural energy gradient driven low-power equipment, such as cooling tower and rooftop solar thermal panels, can be used to achieve free cooling/heating combining photovoltaics.

Small Buildings, Big Impacts: Developing a Library of Small Commercial Building Energy Efficiency Case Studies

Small commercial buildings, or those comprising less than 50,000 square feet of floor area, make up 90% of the total number of buildings in the United States. Though these buildings currently account for less than 50% of total energy consumption in the U.S., this statistic is expected to change as larger commercial buildings become more efficient and thus account for a smaller percentage of commercial building energy consumption. This paper describes the efforts of a multi-organization collaboration and their demonstration partners in developing a library of case studies that promote and facilitate energy efficiency in the small commercial buildings market as well as a case study template that standardized the library. Case studies address five identified barriers to energy efficiency in the small commercial market, specifically lack of: 1) access to centralized, comprehensive, and consistent information about how to achieve energy targets, 2) reasonably achievable energy targets, 3) access to tools that measure buildings’ progress toward targets, 4) financial incentives that make the reduction effort attractive, and 5) effective models of how disparate stakeholders can collaborate in commercial centers to reach targets. The case study library can be organized by location, ownership type, decision criteria, building type, project size, energy savings, end uses impacted, and retrofit measures. This paper discusses the process of developing the library and case study template. Finally, the paper presents next steps in demonstrating the efficacy of the library and explores energy savings potential from broad implementation.

PCM-based High-density Thermal Storage Systems for Residential and Small Commercial Retrofit Applications

Environmental cooling loads comprise 11% of overall electric usage in the United States, and during peak cooling months in hot/humid climates these cooling loads can comprise more than 50% of peak electric energy loads. Thermal storage systems can shift these environmental cooling loads to non-peak hours, making better use of baseload generation capacity as well as reducing the need for expensive and environmentally inefficient peak power plants. Residential and small commercial buildings generate much of the cooling responsible for peak electric load, but these structures may not have the space or facilities to support conventional sensible energy thermal storage systems, such a chilled water thermal storage tanks. For these applications a compact, high-density, retrofittable thermal storage system is needed. This paper investigates the development, testing, and modeling of a compact, scalable PCM (phase change material) based latent thermal storage system for these applications. The results show that a simple tube-encapsulated, tetradecane PCM-based thermal storage system can reduce the size of a thermal store by at a factor of between 2 and 4 while providing acceptable energy recovery rates.

Experimental investigation into the thermal performance of a residential hybrid ventilation system

The thermal performance of a new type of residential hybrid ventilation system was investigated experimentally. The novelty of the system is that it is able to provide filtered and tempered fresh air, either to residences or small commercial buildings such as classrooms, using a combination of natural and/or mechanical driving forces. Fresh air passes through a wall-mounted convector unit. Inside the convector unit is a water-to-air heat exchanger, plumbed into the hydronic central heating system of the building. The heat exchanger is used to warm the ventilation air. Also contained within the convector unit is a mechanical damper used to prevent over-ventilation. An extract fan can be used to drive air through the unit at times of low natural driving forces in order to prevent under-ventilation.Experimental investigation was used to characterise the thermal performance of the system, and to assess its potential to be used as a cool-air ventilation device. It was found that the hybrid system was capable of operating effectively to such a purpose. The system was able to provide an indoor/outdoor air temperature difference of 10 K across a range of air flows up to 120 L/s, in either heating or cooling mode.

Thermal environments and thermal comfort impacts of Direct Load Control air-conditioning strategies in university lecture theatres

As a common approach to manage peak electricity demands associated with air-conditioning (AC), the Direct Load Control (DLC) strategy has yielded positive results in residential and small commercial buildings in countries that include USA, Australia and Canada. However, in educational settings with high occupant density and ventilation requirements, thermal comfort impacts of DLC remain unclear. EnergyPlus was used to simulate thermal environments inside a typical Australian university lecture theatre during DLC events under various cycling schemes, cooling set-point temperatures, building envelope thermal performance specifications and ventilation rates. The analysis explores thermal comfort impacts by applying the PMV/PPD index to simulated indoor climates. Results indicate that off cycle fraction (duration of AC compressor being off during an activation period), cycling period (time for a complete cycle) and cooling set-point temperature have relatively large influences on occupant comfort compared to the building envelope's thermal performance and ventilation rate. In order to maintain acceptable thermal comfort for occupants, DLC algorithms must be applied judiciously and customized to the specific building. All else being equal, DLC algorithms with shorter cycling periods have less adverse thermal comfort impacts than the longer ones.

A review of high R-value wood framed and composite wood wall technologies using advanced insulation techniques

The main objective of this study is to indentify advanced wall frame assemblies applicable for residential and small commercial buildings, that have or could reach R-values larger than RSI – 3.5m2K/W (U-value lower from 0.29). An extensive literature review of existing and past practices is used as the main vehicle to analyze: framing and wall insulation methods, architectural details with focus on minimizing thermal bridges, structural adequacy aspects with respect to gravity and lateral loads, and ability to provide fire and sound breaks. In this paper a wide selection of advance framing wall assemblies is discussed in details with main focus on construction methods, architectural details with minimized thermal bridges, and structural (strength) concerns. High performance wall technologies of consideration include: double walls, Larsen truss walls, optimum or advanced framing walls, walls using distance spacers (furring) and walls made of wood-based composites. Since wood framing for wall applications is mostly used in North America, Scandinavia, and Central Europe, this study is focused on research studies from these regions. In addition, field test studies are presented discussing an application of high R-value of new and retrofitted wall assemblies in actual test houses that have been constructed and being currently monitored.

Evaluation of the energy performance and thermal comfort of an air conditioner with temperature and humidity controls in a cooling season

Interest in energy and environmental problems is increasing worldwide, and efforts are being made to reduce the environmental burden of the world's energy needs. Simultaneously, the demand for precise comfort control in buildings has increased as people have acquired a better quality of life. In most cases in residential or small commercial buildings, the desired indoor environment is achieved by set temperature controls for cooling, especially with Variable Refrigerant Flow (VRF) or Variable Refrigerant Volume (VRV) systems. However, this set-temperature control method may not guarantee thermal comfort for occupants in energy efficient operation. In this study, a new comfort control algorithm is suggested to ensure better thermal comfort of residents, taking into consideration indoor humidity and initial status of indoor air to run the air conditioner. Furthermore, the performance of the algorithm in terms of energy consumption and the thermal comfort ratio is examined and compared with that of the set-temperature control method.

Virtual Surface Temperature Sensor for Multi-zone Commercial Buildings

Multi-zone structure is commonly used in small commercial office buildings, retail stores and supermarket. While there is no adjacent partition wall between the zones, the impact of a neighbor zone on the current zone can be approximated and analyzed through the application of virtual walls. It is critical to accurately estimate the virtual wall surface temperature in order to evaluate the model uncertainty and apply improved supervisory control on multiple rooftop air-conditioning units (RTUs). We propose an innovative virtual surface temperature sensor based on system-identification to solve this challenge. The validation of the virtual temperature model is processed by the three validation criteria: goodness of fit (G), mean squared error (MSE) and coefficient of determination (R2) through off-control conditions with data obtained from a building simulation platform. Further, the sensitivity analysis using the on-control three conditions (under-sizing, properly sizing and oversizing condition) is conducted for analyzing and evaluating the performance of this system-identification based virtual sensor.

A parametric study of energy savings from cleaning coils and filters in constant air volume HVAC systems

This study evaluates the energy savings resulting from the remediation of coil and filter fouling in constant air volume HVAC systems in residential and small commercial buildings. A computer model was developed to simulate the behavior of buildings and their duct systems under various levels of fouling. The model was verified through laboratory and field testing. Parametric simulation and sensitivity analysis results suggest that although fouling can have an impact on both air conditioner and furnace energy use, for the levels of fouling found in the literature, energy savings will be negligible for residential buildings and negative for small commercial buildings.

Load Forecast Model Switching Scheme for Improved Robustnessto Changes in Building Energy Consumption Patterns

This paper presents a new, accurate load forecasting technique robust to fluctuations due to unusual load behavioral changes in buildings, i.e., the potential for small commercial buildings with heterogeneous stores. The proposed scheme is featured with two functional components: data classification by daily characteristics and automatic forecast model switching. The scheme extracts daily characteristics of the input load data and arranges the load data into weekday and weekend data. Forecasting is conducted based on a selected model among ARMAX (autoregressive moving average with exogenous variable) models with the processed input data. Kalman filtering is applied to estimate model parameters. The model-switching scheme monitors the accumulated error and substitutes a backup load model for the currently working model, when the accumulated error exceeds a threshold value, to reduce the increased bias error due to the change in the consumption pattern. This switching reinforces the limited performance of parameter estimation given a fixed structure and, thus, forecasting capability. The study results demonstrate that the proposed scheme is reasonably accurate and even robust to changes in the electricity use patterns. It should help improve the performance for building control systems for energy efficiency.

Indoor Particle Levels in Small- and Medium-Sized Commercial Buildings in California

This study monitored indoor and outdoor particle concentrations in 37 small and medium commercial buildings (SMCBs) in California with three buildings sampled on two occasions, resulting in 40 sampling days. Sampled buildings included offices, retail establishments, restaurants, dental offices, and hair salons, among others. Continuous measurements were made for both ultrafine and fine particulate matter as well as black carbon inside and outside of the building. Integrated PM(2.5), PM(2.5-10), and PM(10) samples were also collected inside and outside the building. The majority of the buildings had indoor/outdoor (I/O) particle concentration ratios less than 1.0, indicating that contributions from indoor sources are less than removal of outdoor particles. However, some of the buildings had I/O ratios greater than 1, indicating significant indoor particle sources. This was particularly true of restaurants, hair salons, and dental offices. The infiltration factor was estimated from a regression analysis of indoor and outdoor concentrations for each particle size fraction, finding lower values for ultrafine and coarse particles than for submicrometer particles, as expected. The I/O ratio of black carbon was used as a relative measure of the infiltration factor of particles among buildings, with a geometric mean of 0.62. The contribution of indoor sources to indoor particle levels was estimated for each building.

Ventilation, temperature, and HVAC characteristics in small and medium commercial buildings in California

This field study of 37 small and medium commercial buildings throughout California obtained information on ventilation rate, temperature, and heating, ventilating, and air-conditioning (HVAC) system characteristics. The study included seven retail establishments; five restaurants; eight offices; two each of gas stations, hair salons, healthcare facilities, grocery stores, dental offices, and fitness centers; and five other buildings. Fourteen (38%) of the buildings either could not or did not provide outdoor air through the HVAC system. The air exchange rate averaged 1.6 (s.d. = 1.7) exchanges per hour and was similar between buildings with and without outdoor air supplied through the HVAC system, indicating that some buildings have significant leakage or ventilation through open windows and doors. Not all buildings had sufficient air exchange to meet ASHRAE 62.1 Standards, including buildings used for fitness centers, hair salons, offices, and retail establishments. The majority of the time, buildings were within the ASHRAE temperature comfort range. Offices were frequently overcooled in the summer. All of the buildings had filters, but over half the buildings had a filter with a minimum efficiency reporting value rating of 4 or lower, which are not very effective for removing fine particles. Most U.S. commercial buildings (96%) are small- to medium-sized, using nearly 18% of the country's energy, and sheltering a large population daily. Little is known about the ventilation systems in these buildings. This study found a wide variety of ventilation conditions, with many buildings failing to meet relevant ventilation standards. Regulators may want to consider implementing more complete building inspections at commissioning and point of sale.

건물의 외주부 존에 대한 동적 부하모델 이용 피크냉방부하 저감효과 분석

In this paper, inverse building modeling was applied to building perimeter zones which have different window orientation. Two test zones of east-facing and west-facing zones in ERS(Energy Resource Station) building, which is representative of small commercial building, was used to test performance of cooling load calculation and peak cooling load reduction. The dynamic thermal load model for the east and west zone was validated using measured data for the zones and then it was used to investigate the effect of peak cooling load reduction by adjustment of indoor cooling temperature set points during on-peak time period. For the east zone, the peak load can be reduced to about 60% of the peak load for conventional control even without any precooling. For the west zone, PLR is nearly independent of the start of the on-peak period until a start time of 1pm. Furthermore, PLR has a small dependence on the precooling duration. Without any precooling, the peak cooling load can be reduced to about 35% of the peak load associated with conventional control.

Financial Reporting And Tax Issues At JC Construction Corporation: An Instructional Case

JC Construction Corporation (JCCC) is a privately held corporation with 10 shareholders, who are all members of the Carpenter family. The company was founded by Joe Carpenter in the late 1990s. The companys projects involve mostly comparatively small commercial building construction, such as restaurants and smaller-scale stores. JCCC specializes in renovation and restoration projects rather than new construction, but does occasionally take on some new construction projects. The company does not build or renovate single family homes. JCCC is located in Minnesota, near the Minneapolis/St. Paul area where remodeling contractors are in high demand.

Ventilation and Indoor Air Quality in 40 Small and Medium Sized Commercial Buildings in California: Indoor Air Quality Methods and Findings

PP-30-137 Background/Aims: As buildings become increasingly conscientious about energy use related to heating and cooling, it become more important to raise awareness of potential sources of indoor sources of both VOCs and particulate matter. A survey of forty of California's (CA) small and medium sized commercial buildings (SMCBs, 1000–50,000 sq ft, 90–4600 m2) was conducted to characterize their ventilation and indoor air quality (IAQ). Methods: The study was designed to include a wide variety of building types, such as offices, retail, restaurants, grocery stores, beauty salons, gas stations, and other building types. A suite of VOCs, aldehydes, and particulate matter were measured inside and outside the buildings over several hours. Results: Based on the results from the first 21 buildings, mean indoor concentrations for some of the traditionally measured compounds include 0.8 μg/m3 for benzene, 9.5 μg/m3 for toluene, 22 μg/m3 for formaldehyde, and 13 μg/m3 for acetaldehyde. The study also included compounds only more recently measured in indoor spaces, reported as median values, such as 2-butoxy ethanol (3.9 μg/m3), d-limonene (6.4 μg/m3), TXIB (1.0 μg/m3), and D5-Siloxane (24 μg/m3). There was a considerable range in the actual concentrations for each of the contaminants. The majority of the buildings had indoor/outdoor ratios less than 1.0 for both ultrafine and PM2.5. However, some of the buildings had clear indications of indoor PM sources with higher indoor levels than outdoor levels. Results on all 40 buildings will be presented at the conference. Conclusion: There is considerable variability in the levels of indoor air pollutants across the wide range of building types found in the small and medium commercial building stock. The views expressed are those of the author and not necessarily those of the funding agencies, California Air Resources Board and California Energy Commission.

Analysis and optimization of the use of CHP–ORC systems for small commercial buildings

The use of combined heating and power (CHP) systems is increasing rapidly due to their high potential of reducing primary energy consumption (PEC), cost, and carbon dioxide emissions (CDE). These reductions are mainly due to capturing the exhaust heat to satisfy the thermal demand of a building. However, when the CHP system is operated following the electric load, the recovered exhaust heat may or may not be sufficient to satisfy the thermal demand of the facility. When the recovered exhaust heat is more than the heat required, the excess is usually discarded to the atmosphere. An organic rankine cycle (ORC) can be used to recover the surplus exhaust heat to generate extra electricity. Therefore, combining the ORC system with the CHP system (CHP–ORC) reduces the electricity that has to be produced by the CHP system, thereby reducing the total PEC, cost, and CDE. The objective of this paper is to study the energetic, economical, and environmental performance of a combined CHP–ORC system and compare its performance to a standalone CHP system and a reference building for different climate zones. A comparison of a CHP–ORC system operating 24 h with a system operating during typical office hours is also performed.

A review on energy, economical, and environmental benefits of the use of CHP systems for small commercial buildings for the North American climate

The use of combined heating and power (CHP) systems to produce both electricity and heat is increasing rapidly due to their high potential of reducing primary energy consumption (PEC), cost, and emissions in domestic, commercial, and industrial applications. In addition to producing both electricity and heat, CHP systems can be coupled with vapor compression systems to provide cooling. This paper analyzes a natural gas engine CHP system together with a vapor compression system for different American climate zones. Performance is measured in terms of operational costs, PEC, and carbon dioxide emissions as a percent of a reference building. The objective of this paper is to compare the performance of a CHP system operating 24 h a day with a system that only operates during typical office hours. Furthermore, the system is optimized based on reducing PEC, minimizing costs, and reducing emissions. In addition, the benefits of CHP systems based on the Energy Star program and the Leadership in Energy and Environmental Design (LEED) program are presented. Results show that, in general, it is more beneficial to operate the CHP system during typical office hours than to operate the system 24 h a day. Also, the CHP system performance strongly depends on the location where it is installed. In addition to reductions in cost, primary energy, and emissions, CHP systems can help achieve the Energy Star label for commercial office buildings and help obtain LEED points that go toward achieving LEED certification status. Copyright © 2009 John Wiley & Sons, Ltd.

On the heat transfer rate reduction of structural insulated panels (SIPs) outfitted with phase change materials (PCMs)

This paper presents a study on the integration of two building technologies into one new unified form for application in residential and small commercial and industrial buildings. Structural insulated panel (SIP) technology was utilized as a structural vehicle, and also for thermal insulation, and phase change materials (PCMs) provided distributed thermal mass. This new type of wall panel was termed phase change material structural insulated panel (PCMSIP). The research conducted during this study provided the foundations for the development of this type of thermally enhanced wall panels and evaluated their thermal performance, based on heat transfer rate reduction, under full weather conditions. On average, the peak heat flux reductions produced by the PCMSIPs in combination with 10% and 20% PCM were 37% and 62%, respectively. The average reductions in daily heat transfer across the PCMSIPs were 33% and 38% for concentrations of 10% and 20% PCM, respectively. The percent PCM concentration was based on the weight of the interior wallboard.

Thermoeconomic modeling of micro‐CHP (micro‐cooling, heating, and power) for small commercial applications

The increasing demand for electrical power as well as energy for heating and cooling of residences and small commercial buildings is a growing worldwide concern. Micro-cooling, heating, and power (micro-CHP), typically designated as less than 30 kW electric, is decentralized electricity generation coupled with thermally activated components for residential and small commercial applications. The number of combinations of components and parameters in a micro-CHP system is too many to be designed through experimental work alone. Therefore, theoretical models for different micro-CHP components and complete micro-CHP systems are needed to facilitate the design of these systems and to study their performance. This paper presents a model for micro-CHP systems for residential and small commercial applications. Some of the results that can be obtained using the developed model include the cost per month of operation of using micro-CHP versus conventional technologies, the amount of fuel per month required to run micro-CHP systems, the overall efficiency of micro-CHP systems, etc. A case study is used to demonstrate differences in the system performances of micro-CHP systems driven by a natural gas internal combustion engine and a diesel engine. Some of the results show that both systems have similar performance and that system total efficiencies in cooler months of up to 80% could be obtained. Also, modeling results show that there is a limit in fuel price that economically prevents the use of CHP systems, which is $11 MBTU−1 for this specific case. Copyright © 2008 John Wiley & Sons, Ltd.