• Energy Research

Abstract As energy availability and demand often do not match, thermal energy storage plays a crucial role to take advantage of solar radiation in buildings: in particular, latent heat storage via phase-change material is particularly attractive due to its ability to provide high energy storage density. This paper analyzes the performance of a building-integrated thermal storage system to increase the energy performances of solaria in a cold climate. A wall opposing a highly glazed facade (south oriented) is used as thermal storage with phase change materials embedded in the wall. The study is based on both experimental and simulation studies. The concept considered is particularly suited to retrofits in a solarium since the PCM can be added as layers facing the large window on the vertical wall directly opposite. Results indicate that this PCM thermal storage system is effective during the whole year in a cold climate. The thermal storage allows solar radiation to be stored and released up to 6–8 h after solar irradiation: this has effects on both the reduction of daily temperature swings (up to 10 °C) and heating requirements (more than 17% on a yearly base). Coupling of the thermal storage system with natural ventilation is important during mid-seasons and summer to improve the PCM charge-discharge cycles and to reduce overheating. Results also show that cooling is less important than heating, reaching up to 20% of the overall annual energy requirements for the city of Montreal, Canada. Moreover, the phase change temperature range of the material used (18–24 °C) is below typical summer temperature levels in solaria, but the increase in thermal capacity of the room alone can reduce annual cooling requirements by up to 50%.

AbstractA solarium/greenhouse attached to a building can provide many benefits, such as collecting solar energy, allowing the cultivation of plants and providing an enjoyable living space to its occupants. Integrating moveable shading devices with fenestration is a recognized way to reduce heat losses and control solar gains. The control strategy for operating shades can have a significant impact on the energy performance of fenestration systems.The aim of this study is to develop an algorithm for the optimum control of combined interior and exterior motorized shading devices based on an energy balance method. The algorithm developed here is designed to maximize solar heat gains while reducing heat losses during the heating season for a cold climate. An attached solarium with motorized shading devices located in Montreal is simulated during the heating season. Results show that heating requirements can be reduced by up to 76% using the proposed algorithm compared to a control scheme based on a fixed solar radiation level. The solarium could collect up to 3.2 MWh (or 134 kWh/m2 of floor area) of excess heat that could be supplied to the house during the heating season. This algorithm could be useful especially in solariums/greenhouses and could be of interest also for solar houses and high efficiency buildings when increasing solar gains and reducing heat losses is a priority.

Abstract This paper presents a new control strategy for improving the performance of one interior and/or exterior planar shade(s). The control strategy is based on performing an energy balance on the fenestration system and calculating the total heat flow (i.e. solar gains + overall heat losses). The heat flow can be maximized or minimized depending on the needs of the space. A solarium model was developed in order to assess the performance of the proposed shading strategy. The solarium model can simulate passive and active thermal storage using sensible and phase change materials. A prototype solarium with motorized interior and exterior shadings has been instrumented and subjected to controlled conditions. The numerical simulations are in good agreement with experimental results. The simulation model has then been used to perform annual simulations of an attached solarium for the location of Montreal, Canada. The year was divided in a heating mode and a mixed mode. During the heating mode (i.e. October through April), heating is provided to keep a minimum temperature of 10 °C and surplus heat is considered when the temperature reaches 28 °C. By using the proposed algorithm for the control of one interior and/or exterior shade(s) in the heating mode, heating requirements of the simulated solarium have been reduced by 3–9% and an additional 9–14% of surplus heat have been collected when compared to a control based on near optimum global horizontal solar radiation levels. During the mixed mode, thermal comfort can be improved significantly (+1822 h) when the interior shade is controlled with the proposed algorithm.

The cultivation of mushrooms in controlled environments generates a significant amount of CO2 as a by-product. This presents opportunities for carbon dioxide (CO2) enrichment in leafy green production. This study aimed to develop a model for CO2 emission and heat exchange rates that can be used to support the synergistic cultivation of mushrooms and leafy greens. This was achieved by aggregating data from literature with experimental data gathered in two different testing spaces. The average CO2 emission and heat exchange rates for shiitake incubated at 21 °C were determined and a CO2 emission rate model for mixed substrate in incubation was developed based on indoor temperature variations. The results indicated that oyster mushrooms have a notable CO2 enrichment potential, twice that of shiitake in the incubation stage and five times more in fructification. Additionally, oyster mushrooms released a significant amount of heat during incubation. In contrast, shiitake mushrooms with their minimal heat exchange rate during incubation could offer an energy-efficient option for synergistic cultivation with leafy greens in environments where cooling is required year-round. Moreover, it was observed that the CO2 emission rate of a full-scale incubation chamber is strongly correlated with indoor temperature. These findings offer valuable information for modeling the CO2 emission and heat exchange rates of mushroom and leafy green farms.

Abstract Thermal energy storage (TES) systems can be designed in order to maximize their impact on a specific design target, such as reducing indoor temperature diurnal swings. Identifying the foremost design objective(s) is highly important since different design objectives result in distinct optimal designs. This paper compares several design concepts and associated criteria that can be satisfied with passive TES in various applications with a focus on isolated gain spaces like solaria and greenhouses. Potential design targets for thermal mass design strategies are compared along with common metrics used to characterize the performance of TES systems. Different design objectives/parameters are discussed, such as: 1) optimal time lag; 2) optimal decrement factor and transfer admittance; 3) reduction of space heating and cooling energy consumption; 4) minimizing indoor temperature swings; 5) maximizing the room average temperature under passive response; 6) reducing peak temperatures. This review of targets and metrics provides a basis for identifying the most relevant performance variables for solaria and greenhouses. A novel metric is presented for characterizing the time lag between the peak absorbed solar radiation and the peak TES surface temperature: τ [ Q a − T s ] . A methodology and design recommendations for integrating TES into solaria and greenhouses are presented in Part 2.

Abstract Selecting optimum windows in heating dominated climates is a complex task because of the inherent trade-off between their U -value and solar heat gain coefficient. In addition, the use of shades is known to reduce heat losses, but they are rarely selected for this intent and considered as an integrated fenestration system at the design stage. This paper presents a method for selecting optimum fenestration systems (windows with shades) to maximize the annual net energy balance. The method has the capability to simulate a one or two layer shading system with one exterior and/or one interior planar shade(s). This methodology generates 2D schematics indicating the net energy balance of different fenestration systems. Such schematics are useful at an early design stage when there is a need to compare different design options for different orientations on a relative basis. Diagrams are presented for five glazings with an interior roller shade, an exterior roller shutter and a combination of both, for the four cardinal orientations for the city of Montreal, Canada. A comparison of simulated and experimental U -values of four shading devices indicates results reasonably close to each other.

Abstract This paper presents a methodology for sizing passive thermal energy storage (TES) systems in solaria and greenhouses. Six different configurations are investigated, which encompass the most frequent cases. These configurations are studied with two complementary approaches: frequency response (FR) and finite difference thermal network (FD). FR models are used for sensitivity studies under short periodic design sequences while FD models are used in full-year performance assessments with real weather data. The most relevant performance variables for characterizing TES in solaria and greenhouses were identified in Part 1. In this paper, simulation results of these key variables are presented under varying conditions. A methodology for sizing TES in solaria and greenhouses is presented along with design recommendations. The energy balance equations for six different configurations are included in order to make the methodology applicable to a variety of designs. The methodology is based on a FR model with a simulation design period of five cold sunny days followed by five cold cloudy days; this sequence is representative of the most extreme conditions in a year and thus provides a good basis for the comparative assessment of design improvements.

Abstract Most natural building materials are hygroscopic and permeable to water vapour. These two characteristics have the potential to improve the longevity and indoor air quality of buildings. However, the potential of winter condensation due to vapour diffusion and the risk of mold growth should be assessed for safeguarding the longevity of building assemblies. This study investigates the relative importance of driving rain, plaster capillarity and the presence of a vapour barrier on the moisture content of building materials and the risk of mold growth for a hygroscopic and permeable building envelope (HPBE). Hygrothermal simulations of a single-family house in Denmark mainly made of wood and clay are performed with WUFI. Results indicate that the presence of an overhang is essential to ensure the durability of a HPBE rendered with a capillary active lime-based plaster while the presence of an overhang has a negligible impact for a mineral cement-based plaster. Including a vapour barrier did not introduce significant changes on the moisture content of this wall assembly. Simulation results indicate that the type of plaster and the wind-driven rain exposure are the most critical variables affecting the hygrothermal performance of this wall assembly.

AbstractThe European Union has set a goal that the energy use in the built environment shall be reduced by 41% to the year 2050 compared to 2005-2006. This could introduce new opportunities for solar thermal systems in cold countries. In such countries, like Sweden and Canada, the economy in solar thermal collector installation projects is often spoiled by the fact that most of heating energy demand of the building occurs during periods when the available solar energy is low.The present paper investigates the performance of solar thermal systems subjected to different quota between space heating and domestic hot water demand (DHW). This study investigates the performance of a solar thermal system integrated to four different buildings with varying heating loads in two different locations, Sweden and Canada. Models of single family houses are created which are able to simulate the total heating demand with different heating demand profiles but the same DHW demand. Simulations are performed in TRNSYS, an advanced tool used to simulate transient systems. Results indicate that solar combisystems tend to generate more useful energy and therefore be more cost effective when installed in buildings with higher heating demands.