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Buildings consume a significant amount of energy worldwide in maintaining comfort for occupants. Building energy management systems (BEMS) are employed to ensure that the energy consumed is used efficiently. However these systems often do not adequately perform in minimising energy use. This is due to a number of reasons, including poor configuration or a lack of information such as being able to anticipate changes in weather conditions. We are now at the stage that building behaviour can be simulated, whereby computer programs can be used to predict building conditions, and therefore enable buildings to use energy more efficiently, when integrated with BEMS (i.e. simulation assisted control [1]). In this paper we demonstrate a low cost BEMS that uses building simulation to predict optimised electrical heating startup control points. Those that use electricity for heating in Scotland, where this study was based, tend to be fuel-poor, hence there is a strong case for optimisation, particularly when electricity costs nearly three times as much as the equivalent unit of gas for heating applications. The proposed system demonstrated a 50% energy saving in the reduced heating time compared to scheduling when retrospectively evaluated. [ABSTRACT FROM AUTHOR]

Developing BEPS models which predict energy usage to a high degree of accuracy can be extremely time consuming. As a result, assumptions are often made regarding the input data required. Making these assumptions without introducing a significant amount of uncertainty to the model can be difficult, and requires experience. Even so, rules of thumb from one geographic region are not automatically transferrable to other regions. This paper develops a methodology which can be used to determine useful guidelines for defining the most influential input data for an accurate BEPS model. Differential sensitivity analysis is carried out on parametric data gathered from five archetype dwelling models. The sensitivity analysis results are used in order to form a guideline minimum set of accurately defined input data. Although the guidelines formed apply specifically to Irish residential dwellings, the methodology and processes used in defining the guidelines is highly repeatable. The guideline minimum data set was applied to practical examples in order to be validated. Existing buildings were modelled, and only the parameters within the minimum data set are accurately defined. All building models predict annual energy usage to within 10% of actual measured data, with seasonal energy profiles well-matching. [ABSTRACT FROM AUTHOR]

Building retrofits provide a large opportunity to significantly reduce energy consumption in the buildings sector. Traditional building retrofits focus on equipment upgrades, often at the end of equipment life or failure, and result in replacement with marginally improved similar technology and limited energy savings. The Integrated System (IS) retrofit approach enables much greater energy savings by leveraging interactive effects between end use systems, enabling downsized or lower energy technologies. This paper presents a case study in Hawaii quantifying the benefits of an IS retrofit approach compared to two traditional retrofit approaches: a Standard Practice of upgrading equipment to meet minimum code requirements, and an Improved Practice of upgrading equipment to a higher efficiency. The IS approach showed an energy savings of 84% over existing building energy use, much higher than the traditional approaches of 13% and 33%. The IS retrofit also demonstrated the greatest energy cost savings potential. While the degree of savings realized from the IS approach will vary by building and climate, these findings indicate that savings on the order of 50% and greater are not possible without an IS approach. It is therefore recommended that the IS approach be universally adopted to achieve deep energy savings. [ABSTRACT FROM AUTHOR]

This paper explores the potential of thermotropic (TT) windows as a means of improving overall building energy performance. Capitalising on their ability to dynamically alter solar and visible light transmittance and reflectance based on window temperature, they have the ability to reduce solar heat gains and subsequently reduce cooling loads when the external conditions exceed those required for occupant comfort. Conversely when the external conditions fall short of those required for comfort, they maintain a degree of optical transparency thus promoting opportunities afforded by passive solar gains. To test their overall effectiveness, thermotropic layers made of varying hydroxypropyl cellulose (HPC) concentrations (2 wt.%, 4 wt.% and 6 wt.%) were firstly synthesised and their optical properties measured. Building performance predictions were subsequently conducted in EnergyPlus for four window inclinations (90°, 60°, 30° and 0° to the horizontal) based on a small office test cell situated in the hot summer Mediterranean climate of Palermo, Italy. Results from annual predictions show that both incident solar radiation and outdoor ambient temperature play a significant role in the transmissivity and reflectivity of the glazing unit. If used as a roof light, a 6 wt.% HPC-based thermotropic window has a dynamic average Solar Heat Gain Coefficient (SHGC) between 0.44 and 0.56, this lower than that of 0.74 for double glazing. Predictions also show that in the specific case tested, the 6 wt.% HPC-based thermotropic window provides an overall annual energy saving of 22% over an equivalent double glazed unit. By maintaining the thermotropic window spectral properties but lowering the associated transition temperature ranges, it was found that the lowest temperature range provided the smallest solar heat gains. Although, this is beneficial during periods where cooling may be needed, in those periods where heating may be required, opportunities gained through passive solar heating are limited. In addition, with lower solar heat gain, there is a possibility that artificial lighting energy demand increases resulting in additional energy consumption. [ABSTRACT FROM AUTHOR]

Variable refrigerant flow (VRF) systems vary the refrigerant flow to meet the dynamic zone thermal loads, leading to more efficient operations than other system types. This paper introduces a new model that simulates the energy performance of VRF systems in the heat pump (HP) operation mode. Compared with the current VRF-HP models implemented in EnergyPlus, the new VRF system model has more component models based on physics and thus has significant innovations in: (1) enabling advanced controls, including variable evaporating and condensing temperatures in the indoor and outdoor units, and variable fan speeds based on the temperature and zone load in the indoor units, (2) adding a detailed refrigerant pipe heat loss calculation using refrigerant flow rate, operational conditions, pipe length, and pipe insulation materials, (3) improving accuracy of simulation especially in partial load conditions, and (4) improving the usability of the model by significantly reducing the number of user input performance curves. The VRF-HP model is implemented in EnergyPlus and validated with measured data from field tests. Results show that the new VRF-HP model provides more accurate estimate of the VRF-HP system performance, which is key to determining code compliance credits as well as utilities incentive for VRF technologies. [ABSTRACT FROM AUTHOR]

Traditionally, in building energy modeling (BEM) programs, occupant behavior (OB) inputs are deterministic and less indicative of real world scenarios, contributing to discrepancies between simulated and actual energy use in buildings. This paper presents a new OB modeling tool, with an occupant behavior functional mock-up unit (obFMU) that enables co-simulation with BEM programs implementing functional mock-up interface (FMI). The components detailed in the development of the obFMU include an overview of the DNAS (drivers-needs-actions-systems) ontology and the occupant behavior eXtensible Markup Language (obXML) schema, in addition to details on the creation of the obFMU that contains the co-simulation interface, the data model and solvers. To demonstrate functionality of the tool, three examples of occupant behaviors were simulated, including: (1) turning on and off lights, (2) opening and closing windows, and (3) turning on and off the air conditioners. The obFMU can be used via co-simulation with all building simulation programs that implement the FMI, thus users are not limited to a particular tool. Another advantage is the use of obXML schema to represent occupant behavior, standardize the description of occupant behavior enabling information exchange. [ABSTRACT FROM AUTHOR]

The paper presents the results of 1-year measurement of indoor environment parameters (temperature, relative humidity, CO 2 concentration) in exhibition rooms of one Polish museum in various periods of the year, and the results of simulation on thermal model of this building. The influence of a temperature control scheme in museum rooms on heating and cooling demand was analysed. The actual state (poor control of internal temperature) and ideal control of internal temperature were analysed – two cases in the winter and two cases in the summer. Simulations were performed by ESP-r program. The multi-zone model of the building was validated based on measurement data. Measurements and simulations revealed significant variations in the temperature in the rooms of the museum. The analysis showed that the maintaining internal temperature at constant level of 20 °C in winter reduces monthly heat demand in most of the exhibition rooms. Obtained effect is 5–16% depending on the premises. Provision the raise of a temperature by 1 K results in the increase of heat consumption by 6%. Maintenance of a desired internal temperature, which does not exceed 24 °C in the summer, requires the provision of coolness to the museum premises. [ABSTRACT FROM AUTHOR]

Abstract: Thermally Activated Building Systems (TABS) are regarded as top-cooling systems rather than full air-conditioning systems. Therefore, adaptive thermal comfort models (ASHRAE55, ISSO74 or EN15251) are supposed to be applicable to TABS buildings, although the comfort model conditions are not necessarily satisfied. This paper investigates whether, for a moderate climate and with the heating and cooling set points chosen according to the adaptive models, the building’s energy use reduces. After all, applying adaptive models, if appropriate, is thought to lower energy use because higher maximum operative zone temperatures T op,max are allowed, compared to the conventional ISO7730 model. For purpose of generality, a building with an ideal heating and cooling system is considered. Analysis of moderate climate weather data reveals a low energy reducing potential for the ASHRAE55 and ISSO74 model, because high reference outdoor temperatures hardly occur. EN15251 on the other hand, allows very high T op,max and will lower the cooling need. A 2-zone building simulation demonstrates a higher cooling need for ASHRAE55 and ISSO74, compared to ISO7730. Because cooling is needed during the whole year, the lower winter T op,max of these adaptive models causes these unexpected results. With real data of warmer years or varying gains, this conclusion holds. [ABSTRACT FROM AUTHOR]