EFFECT OF A NOVEL INTERNAL ROLLER SHADING SYSTEM ON ENERGY PERFORMANCE

The purpose of this research is to investigate the impact of movable solar shading on energy performance in subtropical regions of China.An office building retrofitted with a novel internal roller shading system consisting of two shading layers was selected to carry out field measurements and numerous computer simulations were conducted in order to quantify the energy saving performance of this solar shading system,which was further compared with commonly used Low-E windows and regular fabric roller shades.The results show that the solar transmittance ratio is only 1.3%to 7%depending on used solar shading layers in summer and there is almost no negative impact on heating season in winter.The room base temperature reduction ranges from 4-14oC in summer,indicating a significant indoor thermal performance improvement.Meanwhile,the total energy saving for this shading system is 26.06%,24.42%and over 50%,respectively,compared to Low-E windows,fabric roller shades and the bare window case.Thus,this novel solar shading system is a high energy saving measure and can be widely used in a subtropical zone.

Thermal comfort in winter incorporating solar radiation effects at high altitudes and performance of improved passive solar design-Case of Lhasa

The solar incidence on an indoor environment and its occupants has significant impacts on indoor thermal comfort.It can bring favorable passive solar heating and can result in undesired overheating(even in winter).This problem becomes more critical for high altitudes with high intensity of solar irradiance,while received limited attention.In this study,we explored the specific overheating and rising thermal discomfort in winter in Lhasa as a typical location of a cold climate at high altitudes.First,we evaluated the thermal comfort incorporating solar radiation effect in winter by field measurements.Subsequently,we investigated local occupant adaptive responses(considering the impact of direct solar irradiance).This was followed by a simulation study of assessment of annual based thermal comfort and the effect on energy-saving potential by current solar adjustment.Finally,we discussed winter shading design for high altitudes for both solar shading and passive solar use at high altitudes,and evaluated thermal mass shading with solar louvers in terms of indoor environment control.The results reveal that considerable indoor overheating occurs during the whole winter season instead of summer in Lhasa,with over two-thirds of daytime beyond the comfort range.Further,various adaptive behaviors are adopted by occupants in response to overheating due to the solar radiation.Moreover,it is found that the energy-saving potential might be overestimated by 1.9 times with current window to wall ratio requirements in local design standards and building codes due to the thermal adaption by drawing curtains.The developed thermal mass shading is efficient in achieving an improved indoor thermal environment by reducing overheating time to an average of 62.2% during the winter and a corresponding increase of comfort time.

A model to determine soiling,shading and thermal losses from PV yield data

Apart from being a clean source of energy,photovoltaic(PV)power plants are also a source of income generation for its investors and lenders.Therefore,mitigation of system losses is crucial for economic operation of PV plants.Combined losses due to soiling,shading and temperature in PV plants go as high as 50%.Much of these losses are unaccounted initially,which can jeopardize the economic viability of PV projects.This paper aims to provide a model to determine losses due to soiling,shading and temperature using quantities like irradiance,cell temperature,DC power and current,which are readily available in PV yield data captured by the remote monitoring system,without involving any additional sensors or equipment.In this study,soiling,shading and thermal losses were calculated using PV yield data obtained from a 30-kWp PV plant located in Kharagpur,India.The results showed soiling and shading losses as high as 25.7%and 9.7%,respectively,in the month of December.Soiling loss was verified by measuring transmittance loss of coupon glasses installed in the vicinity of the plant.Shading loss was verified by shadow simulation using an architectural tool(SketchUp).Array thermal loss obtained using the proposed methodology was found to be in line with the estimated value obtained from PVsyst simulation.Additionally,using time-series data,the energy losses corresponding to soiling,shading and temperature effects were calculated by a numerical-integration technique.The monetary loss due to these energy losses thus obtained provides criteria for deciding when to mitigate the sources of these losses.

IDENTIFYING OCCUPANTS’APPROPRIATE SEATING POSITION AND VIEW DIRECTION IN OFFICE BUILDINGS:A STOCHASTIC SHADE CONTROL BASED MULTI-OBJECTIVE VISUAL COMFORT OPTIMIZATION

Manually operated solar shades have a significant impact on indoor visual comfort.This research investigates occupants’appropriate seating position and view direction in a west-facing office cell using a previously developed shade behavior model.The non-dominant sorting genetic algorithm(NSGA-II)based Multi-objective optimization was adopted to identify the optimal and near optimal solutions.Daylight and glare index were used as two visual comfort objectives for optimization and robustness of optimization results against shade behavior uncertainty that was analyzed using statistical analysis.Results show that near optimal solutions can be used instead of the optimal one since they provide more flexibility in seating positions while maintaining almost the same visual comfort performance.And thus,the appropriate seating position considering occupants’preference is 1.5m away from the external window with two view directions near parallel to the window for west-facing office rooms.

Architectural quality of the productive facades integrating photovoltaic and vertical farming systems: Survey among experts in Singapore

Buildings could play a critical role in energy and food production while making highdensity cities more resilient.Productive facades(PFs),as flexible and multi-functional systems integrating photovoltaic(PV)and vertical farming(VF)systems,could contribute to transforming buildings and communities from consumers to producers.This study analyses the architectural quality of the developed PF concept drawing on the findings of a web-survey conducted among experts e building professionals in Singapore.The developed design variants are compared with regards to key design aspects such as facade aesthetics,view from the inside,materialisation,ease of operation,functionality and overall architectural quality.The study also compares and discusses the results of the web-survey with the results of a previously conducted door-to-door survey among the potential users-residents of the Housing&Development Board(HDB)blocks.The findings confirm an overall acceptance of the PF concept and reveal a need for synergetic collaboration between architects/designers and other building professionals.Based on the defined PF design framework and the results of the two surveys,a series of recommendations and improved PF prototypes are proposed for further assessment and implementation in order to foster their scalability from buildings into communities and cities.

Reassessment of fenestration characteristics for residential buildings in hot climates: energy and economic analysis

This paper attempts to resolve the reported contradiction in the literature about the characteristics of high-performance/cost-effective fenestration of residential buildings,particularly in hot climates.The considered issues are the window glazing property(ten commercial glazing types),facade orientation(four main orientations),window-to-wall ratio(WWR)(0.2–0.8),and solar shading overhangs and side-fins(nine shading conditions).The results of the simulated runs reveal that the glazing quality has a superior effect over the other fenestration parameters and controls their effect on the energy consumption of residential buildings.Thus,using low-performance windows on buildings yields larger effects of WWR,facade orientation,and solar shading than high-performance windows.As the WWR increases from 0.2 to 0.8,the building energy consumption using the low-performance window increases 6.46 times than that using the highperformance window.The best facade orientation is changed from north to south according to the glazing properties.In addition,the solar shading need is correlated as a function of a window-glazing property and WWR.The cost analysis shows that the high-performance windows without solar shading are cost-effective as they have the largest net present cost compared to lowperformance windows with or without solar shading.Accordingly,replacing low-performance windows with high-performance ones,in an existing residential building,saves about 12.7 MWh of electricity and 11.05 tons of CO_(2) annually.