Commercial Building Applications Research Articles

Evaluating the impact of off-design CHP performance on the optimal sizing and dispatch of hybrid renewable-CHP distributed energy resources

The maturation of distributed energy resources (DER) has prompted the exploration of their deployment in commercial building applications due to their potential to supply energy at lower costs and emissions rates compared to centralized generation. While several software tools exist for evaluating the techno-economic potential of integrated renewable energy and combined heat and power (CHP) systems for distributed generation applications, many suffer from poor accuracy in capturing off-design (part load and changes in ambient air temperature and pressure) performance characteristics of microturbines, combustion turbines, or internal combustion engines. Thus, this paper presents a methodology for integrating these off-design characteristics in the mixed-integer linear program within REopt, a hybrid DER screening tool. The economic impact of the CHP off-design performance is observed through several application studies of various hybrid system configurations in different climates. Each study indicates how CHP off-design performance influences optimal sizing and dispatch decisions and therefore overall system economic value. We observe through case studies that modeling without the off-design effects, depending on the CHP prime mover and site, can result in Net Present Value predictions of hybrid systems that can be overoptimistic in frequently hot climates (up to 52 %), too conservative in frequently cold climates (up to 11 %), or unaffected (＋/−1 %) in temperate climates. Cases also highlight several advantages of hybrid systems relative to non-hybrid systems such as total economic value and the systems’ ability to mitigate potentially negative consequences attributed to off-design performance.

Laboratory testing methods to evaluate the reliability of occupancy sensors for commercial building applications

The energy performance of commercial buildings is greatly influenced by occupants which are highly variable and among the most unpredictable components of a building's operation. While most building control systems use fixed, predetermined occupancy schedules, these fixed occupancy levels can be quite different from actual occupancy. This can cause unnecessary energy consumption, particularly from heating, ventilation, and air conditioning (HVAC) and lighting systems which are responsible for approximately 60% of commercial buildings' energy use. The use of occupancy counting sensor systems integrated with building management system controls is one method that can be used to improve the energy-consuming performance of buildings. However, there is no standardized universal methodology and metrics to evaluate their reliability. The aim of this research is to develop a uniform evaluation methodology to assess the reliability of occupancy counting sensor systems in a controlled laboratory environment. The developed testing methodology includes both “typical” scenarios representing the occupancy scenarios of a typical commercial building, and “failure” testing scenarios which represent a range of potential scenarios that may impact a sensor system's reliability. These methods were then implemented in a case study to evaluate the performance of two novel occupancy counting sensor systems (i.e., door-centric, and camera-based). Results suggest that typical testing results can be used to compare the overall performance of the occupancy counting sensor systems; however, failure testing is also important to understand the weaknesses of the sensor system in order to select the suitable one for the intended use of the commercial building. In addition, the proposed methodology includes a modified confusion matrix which enables the ability to identify if failures are caused by over or under counting occupants and to what extent this occurs over the testing period.

Experimental Assessment of Rotary Solid Desiccant Dehumidifier Assisted Hybrid Cooling System

"The prime objective of the present investigation is to assess the performance evaluation of rotary solid desiccant dehumidifier integrated vapor-compression integrated hybrid thermally cooling system by experimental investigation for the transient humid conditions. The experimental test set up is precisely designed and practically fabricated so as to obtain the consistent experimental data during performance testing. The main aim of the experimental investigation is to measure the overall system performance of the rotary solid desiccant assisted hybrid dehumidification and cooling system in terms of COP by measurement at various ambient conditions, air stream flow rates and different regeneration temperatures. The desiccant integrated hybrid thermally cooling system (DAHCS) is primarily the environmental protection technique for indoor comfort cooling purpose of the various residential and commercial building applications. This system also reduces the CFC level in the environment because it minimizes the use of conventional refrigerant. It is found that the rotary solid desiccant dehumidifier assisted hybrid cooling system (DAHCS) is alternate suitable option against vapor compression integrated conventional cooling system in transient humid climates. The desiccant assisted hybrid cooling system (DAHCS) has proven their feasibility and energy saving in the field of built environment. It is concluded that this innovative cooling technology is feasible and demand low energy for comfort cooling. This study is very useful in enhancing opportunities to extend further innovation and core research in different areas of desiccant integrated hybrid thermally cooling system.

Advanced smart trigeneration energy system design for commercial building applications – Energy and cost performance analyses

Smart building-integrated trigeneration technology has the potential to meet the world goals for significant reduction of greenhouse gas (GHG) emissions. Some of the new research and development policies are aimed at development of novel and renewable hybrid systems, shift from unit to integration technology; implementation of demand-side management; move from centralized macro to decentralized micro technologies, etc. Recognizing the importance of trigeneration in future energy mix, hybrid renewable trigeneration systems - with integration of photovoltaic-thermal (PVT), ground source heat pump (GSHP) and smart control - were developed for a small commercial building. This paper discusses the energy and cost performance as well as GHG emissions of these systems sized to meet building space heating/cooling loads and HVAC electric power requirements. The results enhance the knowledge and provide useful information to designers on how these trigeneration systems should be applied under variety of conditions, what are their advantages in comparison to a single ground source heat pump system, and what are the energy, economic and GHG emission impacts of smart communications and artificial intelligence controls.

Energy Management Strategy of a Reconfigurable Grid-Tied Hybrid AC/DC Microgrid for Commercial Building Applications

This paper proposes an energy management strategy (EMS) of a reconfigurable grid-tied hybrid ac/dc microgrid (HMG) architecture for commercial building (CB) applications. This HMG architecture consists of a multi-mode configuration (MMC) with renewable-based distributed generators (DGs), energy storages (ESs), and genset. The main advantage of this architecture is its capability to reconfigure its structure based on the predicted building load power (BLP) and renewable-based DGs power. However, minimizing the building electricity cost (BEC) and maximizing the reliability index (RI) of a reconfigurable grid-tied HMG architecture is a challenging task due to the stochastic behaviors of BLP and renewable-based DGs power. In this context, the BLP and renewable-based DGs behaviors are modeled using an artificial neural network approach to predict future time slot values. Then, system level models are developed for HMG energy sources and grid-tied converters/switches. Furthermore, BEC and RI models are developed based on the dynamic pricing of grid/HMG electricity cost and supplied energy. Then, an EMS is proposed for the developed reconfigurable grid-tied HMG architecture, which consists of a two-stage control strategy, i.e., stage I and stage II. Stage I control strategy minimizes BEC and maximizes RI using multi-objective particle swarm optimization (MOPSO) and MMC. Stage II control strategy generates control signals for HMG energy sources, converters, and grid-tied converters/switches based on stage I reference signals. Historical data is used to demonstrate the effectiveness of the proposed EMS for a reconfigurable grid-tied HMG architecture. Through numerical simulation studies, it is shown that the proposed EMS is capable of reducing BEC and increasing RI by concurrently enabling MMC of a reconfigurable grid-tied HMG architecture.

Ultra-fine nano-CaCO3 based-epoxy composites: A high-strength nano-filler engineered via planetary ball milling for advanced structural applications

CaCO3 fillers offer high stiffness and impact resistance, but their rigid, brittle behaviour makes it challenging to attain good tensile properties in epoxy matrices. Herein, we report a high tensile strength and stiff nano-CaCO3 /epoxy composites engineered via planetary ball milling for the first time. Remarkable improvement in strength of ∼ 51% (51.90 MPa) and modulus of ∼ 28% (522.62 MPa) at 1 wt% was observed with respect to micron-sized counterparts. A fascinating observation of ∼ 40% enhancement in ductility was also seen. The results imply that nano-CaCO3 particles (38–52 nm) showed promising results to be used as sustainable concrete nanofiller in greener construction industry and other commercial building applications.

Potential retrofits in office buildings located in harsh Northern climate for better energy efficiency, cost effectiveness, and environmental impact

The current study evaluates the potential measures for enhancing energy efficiency in a commercial building application. It is directed towards addressing Northern climate conditions that are scarce in literature. To highlight the recommended measures, a case study involving a two-storey office building that was built in the late 1970s in Ottawa, Canada is presented. As typical for commercial buildings in Northern climates, building heat is provided by natural gas. Cooling, lighting, and other building needs are supplied by electricity. The building current operational condition deviates from what is recommended by the building code. The authors were consulted to propose energy efficiency measures for the building. The building was simulated using the eQuest software. Verification of the simulation results was performed against historic site data. The model highlighted several parameters that can reduce energy consumption and greenhouse gas emission. Major influencers on energy consumption were: building envelope, water heating system, and building air tightness. Amongst them, increasing building air tightness is the cheapest to implement. On the other hand, the parameters that are functions of occupancy had minor effect on the reduction of energy consumption. A detailed economic analysis has been conducted to evaluate the feasibility of the proposed retrofit strategies. The analysis quantified that the wall, roof insulation, boiler upgrade and building air tightness have a high impact on reducing energy consumption by more than 52%. The improvements have the potential to reduce the emissions by around 82 tons of CO2 per year. The return on investment was found to be 5 years. The incorporation of renewable energy to the building was also investigated. Solar energy is not commonly integrated in cold climates in most of the reported research. For the current study, a solar heating system was installed to supply needed hot water and a PV system is used for electricity generation. This causes the payback period to increase to 5.6 years if solar water heating is added and to 9.1 years with solar water heating and photovoltaic integration. Debt ratio and interest rate have detrimental effect on return on investment for the project. The results of the current study are valuable recommendations for people interested in retrofitting commercial applications in Northern climates.

White-Model Predictive Control for Balancing Energy Savings and Thermal Comfort

To save energy consumed by a building, utilizing optimal predictive control with model predictive control (MPC) makes the most of energy storage systems (ESSs) to reduce the electrical energy consumption of peak and heavy loads. This study evaluated MPC applicability in a multi-zone commercial building using the EnergyPlus model and conducted multi-objective optimization of thermal comfort and energy savings. As a result of the simulation, optimal ESS charging scenarios responded to the fluctuating electricity pricing system, and changing the peak load time reduced the electricity bill of the grid by 55% compared to the existing operating method. At the same time, room temperatures stayed within the thermal comfort range, and the Pareto curve showed a proper balance between energy saving and thermal comfort. Especially, the proposed method with a white model is applicable for MPC applications in commercial buildings, as it gave optimal solutions within the target time interval.

Development of a PCM-HE to harness waste greywater heat: A case study of a residential building

Waste greywater (GW) from non-industrial buildings has considerable exergy that must be exploited for a sustainable future. Scavenging this low-grade heat from GW into cold water (CW) before storage in a phase change material (PCM) is a novel approach to decouple demand and supply along with integrating storage and transfer in a single heat exchanger (HE). A methodology to optimally select an appropriate PCM along with the heat transfer enhancement procedures both internal and external to the flow pipes is presented. This procedure can be extended to reduce the hot water heating demand for applications in both residential and larger commercial buildings. Furthermore, a design technique to numerically assess the performance of a full-scale HE based on empirical formulations of a unit-volume are also put forward. As a case study, the performance of a counter-flow PCM-HE with vertically cascaded GW and CW finned-corrugated pipes is assessed for heat recovery in household appliances of a residential building. Such HE with 9 m piping length can increment the incoming CW temperature by 9.5 K with complete phase change of 30 kg of PCM in 900 s. A transfer of about 5,100 kJ of heat for PCM melting with GW outflow and freezing with CW inflow occurs within this time frame. Furthermore, to fully exploit the temperature differences between the fluids a three-cascaded PCM arrangement enhances the CW outlet temperature by 64%. The installation of this PCM-HE in a four-member UK household, can save 4,687 kWh of energy annually with a payback time of 4.44 years.

Development of a High-Efficiency, Low-Cost Hybrid SOFC/Internal Combustion Engine Power Generator

The unique and beneficial characteristics of solid oxide fuel cell (SOFC) technology hold much promise for their eventual widespread adoption in numerous residential and commercial building applications. Nevertheless, cost and durability challenges remain that currently limit SOFC technology penetration in stationary energy applications. Under the U.S. DOE ARPA-E INTEGRATE program, the Colorado School of Mines and it partners are developing a novel hybrid stationary power system comprised of an intermediate temperature (600°C), metal-supported solid oxide fuel cell stack (from Ceres Power) integrated with a high efficiency stationary engine and novel balance-of-plant (BOP) equipment. In collaboration with Colorado State University, Kohler Power Systems, and Air-Squared, Inc., the project aims to demonstrate a system that can generate power (125 kW) from natural gas at high electric efficiency (>70%-LHV), and low cost (<900 $/kW). Project development activities on the hybrid SOFC/IC engine system development and requirements are presented and discussed, including experimental results from critical balance-of-plant equipment and techno-economic outlook. Figure 1

Development of a High-Efficiency, Low-Cost Hybrid SOFC/Internal Combustion Engine Power Generator

The unique and beneficial characteristics of solid oxide fuel cell (SOFC) technology hold much promise for their eventual widespread adoption in numerous commercial building applications. Nevertheless, cost and durability challenges remain that currently limit SOFC technology penetration in stationary energy applications. Under the U.S. DOE ARPA-E INTEGRATE program, the Colorado School of Mines and its partners are developing a novel hybrid stationary power system comprised of an intermediate temperature (600-degreeC), metal-supported solid oxide fuel cell stack integrated with a high efficiency stationary engine and novel balance-of-point (BOP) equipment.

A Glance On Radiant Cooling Technology For Heating And Cooling For Residential And Commercial Building Application

As we know that nowadays due to the hot and humid weather and the increasing temperature, a high amount of energy consumption is used for heating and cooling purposes in residential as well as in commercial buildings for air conditioning systems. To overcome this problem and to reduce energy consumption is a challenging task. People required good thermal comfort in an indoor environment so, the use of radiant heating and cooling system is a better way. This concept is used to cool or heat by absorbing or taking sensible heat in the indoor environment by thermal radiation. This system uses water as a thermal medium to cool or heat the room space. The radiant system has three types discussed in these papers for cooling and heating. The paper describes an overall study regarding radiant heating and cooling systems. It includes types of the radiant cooling system, comfort level from the radiant system, energy-saving and cooling load calculations for the designing of the system. It reduces the energy lost due to the duct leakage and reduces the manufacturing cost for the ducting system. It also has a lower life cycle cost compared to conventional. The paper includes the rules formed for the radiant design system i.e. ASHRAE Standard 55 and ISO7730. The Paper concludes that the radiant cooling and heating system is efficient as compared with conventional air-conditioning systems.

Investigation on the effect of different backsheet materials on performance characteristics of a photovoltaic/thermal (PV/T) system

Photovoltaic/Thermal (PV/T) systems are identified as attractive renewable energy technologies for residential and commercial building applications. They provide higher conversion efficiency and better space utilization than independent photovoltaic (PV) and solar thermal systems. The collector design and choice of backsheet are of utmost importance for meeting the long-term reliability, life and performance of a PV/T system. Generally, Copper (Cu)/Aluminum (Al) and Tedlar-Polyester-Tedlar (TPT) are utilized for collector design, whereas glass is also identified as potential backsheet material having specific advantages. The present work analyzes the performance of a refrigerant-based PV/T system with three backsheet materials namely Glass, TPT and Cu using a validated numerical model. It was found that PV/T collector with the TPT backsheet has low cell temperature, whereas the collector with Cu backsheet provides the highest coefficient of performance (COP). Besides, the effect of packing factor and thickness of the backsheet on cell temperature and COP was also studied and reported.

A Glance on Radiant Cooling Technology for Heating and Cooling for Residential and Commercial Building Application

As we know that nowadays due to the hot and humid weather and the increasing temperature the high amount of energy consumption is used for the heating &amp; cooling purpose in residential as well as in commercial building for air conditioning systems. To overcome this problem and to reduce the energy consumption as well as good thermal comfort to people in the indoor environment, use the radiant heating &amp; cooling system is a better way. This concept is used to cool or heat the room and absorbs the indoor sensible heat by thermal radiation. The system removes heat by using less energy and more energy-efficient. This system uses water as a medium to cool or heat the room space. There are three types discussed in these papers for cooling &amp; heating. In this paper, we did an overall study regarding radiant heating and cooling systems. It reduces the energy lost due to the duct leakage. It also has a lower life cycle cost compared to conventional. In this paper, we have reviewed how to reduce energy consumption and give thermal comfortable air-condition through radiant cooling and chilled ceiling panel system.

Evaluation of Bursa metropolitan greenhouse Gas inventory and reduction targets

This study summarizes the greenhouse gas (GHG) emission levels and Sustainable Energy Action Plan (SEAP) of Bursa, where is an industrial, touristic, and historic metropolitan city with a dense population in Turkey. This study summarized direct (scope 1), indirect (scope 2), and other indirect (scope 3) GHG emissions. Urban GHG emissions including scope 1, 2, and 3 activities were determined as 14,148,597 tCO2e for 2016. Industrial fuel consumption, transportation, and residential heating activities were the main sources. GHG emission control sectors were determined according to the last consecutive workshops in 2017. Control actions, such as Energy efficiency/renewable energy applications in residential and commercial buildings, increasing the share of public transport in transportation, and reducing the number of private vehicles in traffic, were planned. Future projections for 2030 were estimated with and without reduction activities. Sectors (industry, agriculture, and animal husbandry) which are not within the jurisdiction of local governments or which cannot be intervened by local governments were excluded. It showed that with the mitigation measures to be implemented. Public transport problems, renewable energy conversion, and reduction of the green texture of the city are the main obstacles.

An overview of renewable energy resources and grid integration for commercial building applications

This paper presents an overview of the integration of renewable energy resources in the urban sector. The article also describes the current global energy demand and growth challenges that the world is currently facing. The literature survey on the global energy scenario and renewable energy integration, which mainly involves solar photovoltaic (PV) and battery energy storage systems (BESS), is presented. The paper also addresses the different contexts of using renewable energy resources (RERs) and grid-connected applications. It develops the concept of PV energy storage integration in commercial building applications. Since the common RERs such as wind and solar vary according to seasonal and geographic locations, an outline of the energy storage system that provides a platform for optimal use of RERs is also presented. This structure refers to their ability and dynamic structure that can combine with the renewable power generation to maximise the use of RERs and to ensure the total energy supply to the load. It was observed that the integration of distributed energy resources (DERs) which are connected to the grid is beneficial when the PV and energy storage system (ESS) are smartly mixed with the utility grid. The primary purpose of this energy mix is to assist in improving the dynamic performance of any electrical network operating in a commercial building setup. Thus, this research work analyses the possibility of designing dynamic behaviour for energy management for commercial building applications in South Africa.

Experimental and theoretical analysis of functional controllability for multi-condenser heat pumps

Multi-split air conditioning systems are finding increasing applications in both residential and commercial buildings. Control of multi-split air conditioning systems have received considerable attentions. Most studies focused on control methods for the cooling mode, while very few control methods were developed for the heating mode. A widely adopted heating control strategy for a typical multi-condenser heat pump is regulating the indoor electronic expansion valve (EXV) openings to control subcooling or supply air temperature of each indoor unit and simultaneous regulating the outdoor EXV opening to control suction superheat. We found from experimental study that this control strategy may cause unstable EXV openings and poor command-following performance. By performing functional controllability analysis, we provide a theoretical insight into the uncontrollable problem and prove that the system is functionally uncontrollable when the conventional heating control strategy is used. Based on findings from functional controllability analysis, a modified system configuration is proposed, with a refrigerant receiver added between the indoor EXVs and the outdoor EXV. The modified system proves to be functionally controllable. Moreover, simulated command-following controllability tests show that the modified system has better performance. This paper verified the ability of functional controllability analysis in detecting structural control problems for refrigeration systems, which can be used as a general method for practical applications.

Development of a Novel High Efficiency, Low Cost Hybrid SOFC/Internal Combustion Engine Power Generator

The unique and beneficial characteristics of solid oxide fuel cell (SOFC) technology hold much promise for their eventual widespread adoption in numerous residential and commercial building applications. Nevertheless, cost and durability challenges remain that currently limit SOFC technology penetration in stationary energy applications. Under the U.S. DOE ARPA-E INTEGRATE program, the Colorado School of Mines and it partners are developing a novel hybrid stationary power system comprised of an intermediate temperature (600°C), solid oxide fuel cell stack integrated with a high efficiency stationary engine and novel balance-of-plant (BOP) equipment. In collaboration with Colorado State University, Kohler Power Systems, and Air-Squared, Inc., the project aims to demonstrate a system that can generate power (125 kW) from natural gas at high electric efficiency (>70%-LHV), and low cost (<900 $/kW). Project activities on the hybrid SOFC/IC engine system development and system requirements are discussed.

A Comparative Energy Efficiency Study of Different Glazing Systems in Residential and Commercial Building Applications

A Comparative Energy Efficiency Study of Different Glazing Systems in Residential and Commercial Building Applications

Performance maps for an air-cooled air conditioning system as a preliminary instrument for the diagnosis of evaporator fouling

During the past few decades, there has been increased interest in the development of automated approaches for detecting and diagnosing faults in air conditioning systems. Among them, thermoeconomic diagnosis is a technique which involves the use of exergy analysis. As a first step towards improving its performance, this work is focused on the thermodynamic and exergy analysis of a direct expansion air conditioning system used in small commercial building applications. The analysis was carried out by means of experimental activities on a 17.5 kW rooftop unit installed at the Herrick Laboratories, Purdue University, Indiana (USA). The system under investigation was equipped with a variable-speed compressor and variable-speed fans, thus allowing the unit to meet different loads. A detailed mapping of the performance of this system was carried out by considering the effect of the outdoor temperature and the cooling load. In addition, the effect of evaporator fouling was investigated. Results showed that poor exergy performance were achieved due to the exergy destruction occurring in the evaporator. Also, when testing evaporator fouling, results showed that this fault contributed to increase the consumption of the mechanical exergy of the air, thus allowing for an easy detection of this fault.