Search

The development of control strategies is a challenge for optimal use of low-temperature heat in complex energy systems. In the energy system of the considered building, several different combinations of active system components lend themselves to supply a given energy demand. Within preceding research, we transformed the considered building into a multi-functional test bench for control techniques that offers optimal conditions for the demonstration and evaluation of control strategies. This paper describes a control strategy for the complex heat pump system based on operation modes. It enables us to integrate a geothermal field into the system with respect to exergetic principles. The paper presents results of the control strategy's first year of operation. It correlates between active operation modes and the respective electrical consumption of the building. We derive the potential of the implemented operation modes for demand response applications. A mode-based control strategy enables the robust and efficient operation of complex building energy systems. We show that the integration of renewable energy sources becomes easy and flexible. [ABSTRACT FROM AUTHOR]

Abstract: Most air handling units (AHUs) in commercial buildings have an air economizer cycle for free cooling under certain outside air conditions. During the economizer cycle, the outside air and return air dampers are modulated to seek supply air temperature at its setpoint. The supply air temperature is typically set at 55F (13°C) to control humidity in the space. However, dehumidification is not necessary when the outside air is dry. Meanwhile, the space may have less cooling load due to envelope heat loss and/or occupant schedule changes. These facts provide an opportunity to use higher supply air temperature to reduce or eliminate mechanical cooling and terminal box reheat. On the contrary, a higher supply air temperature requires increased air flow as well as fan power. Therefore, an optimization question is formed, through which an optimal supply air temperature is identified to minimize total energy consumption. In this paper a steady-state energy consumption model is established for AHU systems under the economizer, and then an analytical optimization method is used to seek an optimal supply air temperature setpoint to minimize the energy cost. This paper presents AHU system energy modeling, supply air temperature optimization, simulated energy savings, and control sequence development. [Copyright &y& Elsevier]

Abstract: This paper presents the optimization of chillers operating using artificial neural networks and genetic algorithms. For the needs of generating chiller models, an artificial neural network was used, trained with data collected from an actual chiller. For that purpose the basic characteristics of artificial neural networks are shown as well as the process of making specific chiller models used for testing the results of application of the genetic algorithm in usage optimization. The optimal criteria with the shown steps for the use of the genetic algorithm and optimization results is also displayed in the paper. The results of use of artificial intelligence methods in optimization of chiller operation are verified through an actual office building model created in the simulation software EnergyPlus and through a series of experiments on an actual office building, equipped with a modern integrated BMS. [Copyright &y& Elsevier]

The impact of glass facades and dynamic shading controls on energy use for lighting and air-conditioning should be carefully investigated to determine ways of saving energy while maintaining comfortable conditions for the occupants. Automated control of interior roller shades may result in improved conditions and reduced energy use if advanced algorithms are used, however recent studies have shown that proper control set points are not easily applied in practice. This paper presents details of a simplified model-based shading control using as a variable criterion the “effective daylight” transmitted into the space; shades move to intermediate positions, aiming to maximize daylight utilization while satisfying visual comfort restrictions. Shade properties and control are linked in this approach, with control operation varying depending on the shade optical properties and facade orientation. The method was implemented in full-scale offices and experimental results are presented in terms of daylight metrics, lighting energy use and visual comfort performance. Furthermore, the control strategy was implemented in an integrated lighting model, validated with experimental data, to investigate the annual daylighting performance of perimeter spaces with one or multiple exterior facades. The method is generalized and can be applied to any shading/glazing properties, location, orientation and room configuration, as well as to spaces with multiple exterior facades equipped with roller shades. Overall, this study presents the principle of synchronized control of multiple window shades on different facades (orientations) of commercial buildings. Integrated with efficient lighting and HVAC controls, it can lead to improvement of daylighting conditions and reduced energy use. [ABSTRACT FROM AUTHOR]

A ground-source heat pump system in combination with different low temperature heating systems was installed in a new school building in Belgium. During the first two years of operation, measurement data indicated that the difference between heating and cooling load could affect the long term thermal stability of the ground storage and thus may result in poor energy efficiency of the GSHP system. This paper describes two low-cost measures that can be taken in order to reduce or prevent such unfavourable conditions. The school building and HVAC system were modeled and on-site measurement data was used for validation. First, the HVAC system was optimized by integrating an additional cooling coil in the exhaust airflow of the air handling unit in order to recuperate waste heat from the exhaust ventilation air. Additionally, the effect of passive cooling during summer holidays on the annual energy balance was investigated. Results indicated that heat recuperation of the exhaust ventilation air and passive cooling of the school building during weekends and summer holidays are complementary and contribute to a more stable ground temperature, consequently significant energy savings can be achieved. [ABSTRACT FROM AUTHOR]

Buildings account for a significant amount of global energy use and CO 2 emissions. Thermally Activated Building Systems (TABS) are a technology with potential for significantly reducing buildings energy use. TABS are heating and cooling systems that are integrated in the building structure. They mainly exchange heat through radiation and are able to store heat in the building thermal mass. TABS high thermal mass and their interaction with the building structure make their energy evaluation and design process difficult. Development of simulation models has been essential to study the design and control of TABS. Control of TABS is challenging due to the slow response time and storage capacity. A lot of research has been conducted to develop control strategies that fully exploit its energy saving potential and that maximize the use of renewable energies. This paper summarizes the main characteristics of TABS and presents the developed simulation models and control strategies. [ABSTRACT FROM AUTHOR]

A variable capacity heat pump, with variable speed drives on the secondary circuits, needs an adequate control for achieving the maximum energy efficiency. In the present paper, experimental data and a modeling procedure of a ground source heat pump (GSHP) with variable speed compressor, variable speed water pumps and variable speed fans in the coils are reported. Both data and model are used to evaluate the operating conditions that lead to the maximum seasonal coefficient of performance of the system. The control parameters that can be varied are the followings: frequency of compressor, frequency of water pump to the borehole heat exchangers, frequency of the water pump to the user, velocity of the fans, water temperature to the user. From the experimental data, it was possible to define a control variable which is the ratio of compressor electric power consumption to the power absorbed by the water pumps. The model is also the baseline to develop a control strategy that is implemented in the present GSHP system, developed in the framework of the European Project Ground-Med, with the final objective of maximizing the seasonal coefficient of performance of the system. [ABSTRACT FROM AUTHOR]

This paper proposes a new method for an optimal control of the heating system at the building scale. This control is a new approach of energy planning that aims to decrease the heating consumption/expenses over a defined prediction horizon while respecting the occupants’ thermal comfort. It employs a simplified building thermal model to simulate the building thermal behavior taking into consideration the weather predictions. This approach is based on the application of Monte Carlo method, i.e., a random generator for the heating system scenarios. The aim is to determine the optimal heating plan for the prediction horizon that fulfills the constraints regarding the thermal comfort of occupants and the minimization of the energy consumption/expenses together with achieving a load shedding. [ABSTRACT FROM AUTHOR]

Abstract: In the last few years, thermal comfort research in summer has significantly increased the electricity consumption in buildings. This is mainly due to the use of conventional air conditioning systems operating with mechanical vapor compression. Solar cooling systems appear to be an interesting solution to solve this problem. But the understanding of this technology has to be refined through fundamental studies by developing numerical simulations. Moreover, the study of pilot plants is a practical method to gain experience by analyzing all the processes behind solar cooling technology. This paper presents an experimental study of a solar cooling absorption system implemented in Reunion Island, located in the southern hemisphere near the Capricorn Tropic. The particularity of this project is to achieve an effective cooling of classrooms, by a solar cooling system without any backup systems (hot or cold). The aim of this experimental study is to define the limits of the use of such system under tropical climate conditions without setting a set point temperature. Indoor thermal comfort is achieved by a self-stabilizing operating system that maintains the indoor temperature 6°C below the outdoor temperature. During some critical periods of the year, when the outdoor temperature is very high and when the solar cooling system cannot provide enough refrigerating production, thermal comfort inside the building is achieved by using ceiling fans. Firstly we will present the installation and the choices we made in the control and design process. In the second part, an analysis of the experimental results will be presented. [Copyright &y& Elsevier]

Abstract: Impact of the natural ventilation on the building depends on the design of the several components of the building like façade, HVAC and control system. Paper presents several tests of the building with different selection of the components. The double skin façade is compared to the single skin façade with the external or internal shading device and with climate wall. Furthermore, impact of the mechanical or natural night cooling, predictive control is discussed. Final solution represents the possible reduction in HVAC system to balance the costs of the double skin façade. The tests were carried out with the simulation program built in Simulink™ validated with the measurements taken in Test cell at TU Delft as well as in the real office building. Each solution is qualified based on differences in capacities, energy consumptions and costs for various solutions of façade, HVAC system and control. As a final solution optimization of the HVAC system is presented [Copyright &y& Elsevier]