Total Building Energy Consumption Research Articles

Method and case study of quantitative uncertainty analysis in building energy consumption inventories

Collections of building energy consumption data are often uncertain due to unavoidable measurement errors, random errors, non-representativeness of sample data, etc. On the basis of the quantitative uncertainty and Monte Carlo uncertainty propagation methods, the uncertainty of building energy consumption data is quantified. A real case study is conducted on the electricity and gas consumptions of buildings in Ma’anshan city in China in 2009. The results show that the electricity consumption distributions of four kinds of buildings fit Weibull distribution, gamma distribution, normal distribution and lognormal distribution respectively. The total energy consumption of buildings in the city at the cumulative probability of 97.5% is 16.6% higher than that obtained using the conventional method. The uncertainty of random sampling error in total energy consumption is about 14%. The sensitivity analysis results can provide information about the main sources that can help in reducing the uncertainty of the overall energy consumption inventory. This kind of quantification of uncertainty in energy consumption inventories could assist the decision-makers in determining the likelihood of complying with energy reduction objectives, and framing more scientific energy-saving strategies that may reduce building energy consumption.

Life cycle assessment approach for the optimization of sustainable building envelopes: An application on solar wall systems

Design of sustainable building envelopes requires the analysis of environmental performances in every stage of their life cycle. As a matter of fact, the production phase of building materials and components can significantly contribute to the total energy consumption and environmental loads of buildings. However, façade systems such as passive solar systems, ventilated walls and double skins, are usually not designed considering aspects related to their life cycle. Furthermore, there are still few studies concerning the optimization and the combined effect of different design features of complex façades on environmental and energy performances.This paper introduces an integrated approach for the optimization of energy and environmental performances of complex building envelopes that combines life cycle assessment, energy simulation and optimization analysis with factorial plan technique. The environmental performance was calculated in terms of energy demand and CO2 emissions in the production phase and operational phase. The methodology was applied to an exemplary case study with solar wall systems.The results showed that solar walls have high environmental impact both in the production and operational phases. Results of the optimization analysis demonstrated that it is possible to reduce the CO2 emissions and cumulative energy demand of solar walls for both the production and use phases up to −55% in comparison with a traditional design. This methodology may be generally applied to the sustainability analysis, design and optimization of efficient façade systems.

Application of PCM thermal energy storage system to reduce building energy consumption

The building sector is known to make a large contribution to total energy consumption and CO2 emissions. Phase change materials (PCMs) have been considered for thermal energy storage (TES) in buildings. They can balance out the discrepancies between energy demand and energy supply, which are temporally out of phase. However, traditional PCMs need special latent storage devices or containers to encapsulate the PCM, in order to store and release the latent heat of the PCM. The proper design of TES systems using a PCM requires quantitative information and knowledge about the heat transfer and phase change processes in the PCM. In Korea, radiant floor heating systems, which have traditionally been used in residential buildings, consume approximately 55% of the total residential building energy consumption in heating. This article reviews the development of available latent heat thermal energy storage technologies and discusses PCM application methods for residential building using radiant floor heating systems with the goal of reducing energy consumption.

APPLICATION OF HYDROCARBON BASED REFRIGERANTS FOR AIR CONDITIONING IN INDONESIA

Electrical energy consumption in air conditioning systems reaches 60% to 70% of the total electric energy consumption in buildings. Therefore, saving electrical energy consumption in air conditioning systems would have a significant impact on the national electrical energy consumption. Currently, the air conditioning sectors were having a dilemma on finding the alternative substitutes for CFC and HCFC refrigerants which are proven to cause destruction of the ozone layer and contribute to the effects of global warming. This paper will discuss the problems faced by an Article 5 country similar to Indonesia in phasing-out HCFC especially in air conditioning and refrigeration sectors. This paper will also discuss the possibility to use hydrocarbon-based refrigerants, which have zero ozone depletion potential (ODP) and low global warming potential (GWP), in air conditioning sectors. Some results of field applications of this refrigerant will be reported, and in general it can be concluded that the air conditioning retrofitted with hydrocarbon refrigerant consumes 10%–20% less electrical energy. Mixture of R-290 and R-134a was also investigated. R-134a is used to reduce the flammability of R-290 and to make the saturation pressure close to R-22. The results show that at composition of 0.6 R-290/0.4 R-134a mole fractions, the mixture behave as an azeotrope refrigerant mixture and can be used for R-22 replacement. At this composition, lower flammability limit (LEL) is 3693%, which is higher than pure R-290. Hence, the refrigerant mixture can be classified as less flammable A2 class refrigerant. The performance test shows that the refrigerant mixture can be used as a drop-in refrigerant in the R-22 machine. The measurement of refrigeration capacity and compressor input work at the same chilled water temperature shows that the calculated COP of the refrigerant mixture is better than R-22's but lower than R-290's.

A new method to develop typical weather years in different climates for building energy use studies

Principal component analysis of 30-year long-term meteorological variables was conducted. Typical principal component years (TPCYs) were determined for Harbin, Beijing, Shanghai, Kunming and Hong Kong representing the five major architectural climates across China: severe cold, cold, hot summer and cold winter, mild, and hot summer and warm winter. In each climate zone, the TPCY was compared with the 30 individual years and the widely used typical meteorological year (TMY). The monthly principal component and the predicted total building energy consumption based on the TPCY and TMY were very close to the 30-year long-term mean estimation. TPCY for the 21st century in each of the five cities was also identified using predictions from general climate models. The TPCY approach is a good alternative to the TMY method. Firstly, predicted building energy use from TPCY is closer to the long-term estimation than that from the TMY in different climates. Secondly, because only monthly data are considered, the development of TPCY is much simpler and less time-consuming. This would have important applications in the regular updating of typical weather years for building energy studies and in the assessment of the impact of climate change on energy use in the built environment.

Benchmarking energy consumption and CO2 emissions from rainwater‐harvesting systems: an improved method by proxy

AbstractLife cycle analyses (LCAs) show the main operational energy contribution for rainwater‐harvesting (RWH) systems come from ultraviolet (UV) disinfection and pumping rainwater from tank to building. Simple methods of estimating pump energy consumption do not differentiate between pump start‐up and pump‐operating energy or include pump efficiency parameters. This paper outlines an improved method incorporating these parameters that indirectly estimates pump energy consumption and carbon dioxide (CO2) emissions using system performance data. The improved method is applied to data from an office‐based RWH system. Comparison of the simple and improved methods identified the former underestimates pump energy consumption and carbon emissions by 60%. Results of the improved method corresponded well to directly measured energy consumption and energy consumption represented 0.07% of an office building's total energy consumption. Consequently, the overall energy consumption associated with RWH systems is a very minor fraction of total building energy consumption.

Climate change adaptation pathways for Australian residential buildings

Climate change can significantly impact on the total energy consumption and greenhouse gas (GHG) emissions of residential buildings. Therefore, climate adaptation should be properly considered in both building design and operation stages to reduce the impact. This paper identified the potential adaptation pathways for existing and new residential buildings, by enhancing their adaptive capacity to accommodate the impact and maintain total energy consumption and GHG emissions no more than the current level in the period of their service life. The feasibility of adaptations was demonstrated by building energy simulations using both representative existing and new housing in eight climate zones varying from cold, temperate to hot humid in Australia. It was found that, in heating dominated climates, a proper level of adaptive capacity of residential buildings could be achieved simply by improving the energy efficiency of building envelop. However, in cooling dominated regions, it could only be achieved by introducing additional measures, such as the use of high energy efficient (EE) appliances and the adoption of renewable energy. The initial costs to implement the adaptations were assessed, suggesting that it is more cost-effective to accommodate future climate change impacts for existing and new houses by improving building envelop energy efficiency in cooling dominated regions, but installing on-site solar PVs instead in heating and cooling balanced regions.

Performance analysis of supply and return fans for HVAC systems under different operating strategies of economizer dampers

HVAC systems and associated equipment consume a relatively large fraction of total building energy consumption, a significant portion of which is attributed to fan operation. The operation of economizer dampers when installed can cause high energy consumption in fans if they are not functioning in proper and optimal manner. This will mainly be due to the potential high pressure drops through those dampers and associated high total pressures that should be developed by supply and/or return fans. It is then necessary to ensure that a proper strategy to operate optimally the economizer dampers is implemented with minimum fan energy use. The paper examines several operation strategies of the economizer dampers and investigates their effects on the performance of both the supply and return fans in HVAC system. It also discusses a new operating strategy for economizer dampers that can lead to lower fan energy use. The strategies are evaluated by simulations for a typically existing HVAC system. Several factors such as the building locations, system characteristics, resistance in the duct where the dampers are installed, supply air temperature and economizer control, and minimum ventilation requirements are also considered during the evaluations. The results show that the way of the economizer dampers been controlled has a significant effect on fan performance and its energy use. The proposed strategy if properly implemented can provide fan energy saving in the range of 5–30%, depending mainly on the number of hours when the system operates in the free cooling mode, damper characteristics, and minimum outdoor air.

Modelica-Based Dynamic Modeling of a Chilled-Water Cooling Coil

For heating, ventilating, and air-conditioning (HVAC) systems for commercial buildings, the cooling coils in air-handling units (AHUs) account for a significant fraction of total building energy consumption and have a major impact on comfort conditions and maintenance costs. Development of cost-effective advanced control strategies will enhance the performance and efficiency of AHUs. The control design process can be greatly facilitated with simulation on a high-fidelity dynamic model prior to experimental validation and implementation. This paper presents a dynamic model for a chilled-water cooling coil. The model development was based on Dymola and Air Conditioning Library with some revision on heat exchanger modeling. For chilled-water cooling coil modeling, the major challenges include the variation of coil surface conditions under flow rate changes and partially-dry-partially-wet operations. This study proposes a dynamic coil model that is capable of predicting cooling performances under fully dry, partially-dry-partially-wet, and fully wet conditions. Validation with experimental data from a benchmark study was conducted under both dry and wet surface conditions. The model predicted the experimental results quite well for both transient and steady-state behaviors. Such a transient model will lay a more quality foundation for controller validation at the simulation phase.

Impact of modelled global solar radiation on simulated building heating and cooling loads

Two-parameter regression models were used to predict global solar radiation (GSR) for the nine major thermal zones and sub-zones – severe cold (I, II and III), cold (I, II and III), hot summer and cold winter, mild, and hot summer and warm winter – across China. The impact of using modelled GSR on building energy simulation was investigated. A total of nine cities were selected, one for each thermal zone. Generic office buildings were developed for each of the nine cities according the local design/energy codes. Two sets of energy simulation were conducted for each city, one with the measured GSR and the other the modelled data. The computed results were analysed in four aspects – solar heat through the windows, building heating loads, building cooling loads and the corresponding building energy consumption. It was found that simulated annual heating/cooling loads could differ by 0.1–6.2% and total building energy consumption 0.1–1.2%. These differences were also compared with the mean bias error and root-mean-squared error of the modelled GSR.

Chinese kang as a domestic heating system in rural northern China—A review

The Chinese kang is an ancient integrated home system for cooking, sleeping, domestic heating and ventilation. It is still widely used today in nearly 85% of rural homes in northern China. In 2004, there were 67 million kangs used by 175 million people. Existing kang designs are mostly based on the intuition and accumulation of craftsman experience. There is a trend that Chinese kang is gradually replaced by bed and coal-burning radiators, domestic heating stoves, etc. using commercial energy. As rural building heating constitutes 25% of total building energy consumption in China, we consider that the transition and new technologies for rural home heating in northern China is crucial for managing future building energy consumption in China. This paper reviews the basic heat transfer and airflow principles of Chinese kang, as well as describing the traditional grounded kang and the relatively new elevated kang. The thermal performance of the kang is shown by data from literature and field surveys. The future of Chinese kang and research needs is also briefly discussed. There is also a need for scientific study in addition to experience accumulation, to form basis for engineering design.

Renovation of existing office buildings in regard to energy economy: An example from Ankara, Turkey

Unit energy consumption of existing buildings in Turkey is excessive. While average energy consumption of residential buildings in Europe is 100 kWh/m 2 per year, it is about 200 kWh/m 2 per year in Turkey. The principle reason for this, is that there was not any regulation on thermal insulation issues until recent years. However, the fiscal value of total energy consumption in residential buildings is about $2.5 billion. Recent research has shown that 40% of this energy consumption could be saved, provided that using energy efficiently. Furthermore, every reduction in energy-usage has a significant influence on environmental protection and CO 2 emissions. This study has focused on energy efficiency in a building of public sector that had been inaugurated in 1988 in Ankara. During the pre-investigative step, it has been determined that 47% of total energy consumption of the building could be saved.

実測調査による熱源システムのエネルギー利用効率に関する研究 : システムCOPを指標とした熱源システムの効率評価

The growing energy consumption of commercial buildings in the field of civilian sector strongly requires to take effective energy saving measures. Especially as the energy consumption of heat source system in office buildings occupies as high as about 30% of the total building energy consumption, the efficiency of the heat source system should urgently be upgraded. For this purpose, it is essential to grasp the annual thermal load fluctuation and corresponding operation status of the heat source system for analysis. At present, however, the examples of measurement survey of the energy efficiency ratio of the system in commercial buildings can scarcely be found. Backed by such circumstance as above, this study conducted actual measurement on the heat generation and energy consumption of the heat source system in three typical commercial buildings to grasp the operation status and energy efficiency ratio by employing the system COP as a performance index.

Daylight performance of lightpipes

Increasing the use of natural daylight for lighting purposes in buildings can offer large savings in electricity usage, up to 20–30% of total building energy consumption. One solution is the use of lightpipes that can not only bring light into otherwise inaccessible or dimly lit places, but also improve the internal environment without generating excessive heat. The performance of six light pipes has been monitored in three different areas, a workshop, a residential landing, and a small office. The highest illuminance was 1538 lux, obtained underneath the straight lightpipe on the landing, with an aspect ratio of 2.1. The lowest was 41 lux in the darkest corner of the workshop. The average illuminance for the whole landing was 366 lux and a mean internal to external ratio of 0.48%. The results show that lightpipes are proficient devices for introducing daylight into buildings, the most effective lightpipes being straight, short ones with low aspect ratios; consequently, larger diameter lightpipes would probably be more effective. However, the benefits of lightpipes also include energy savings, user satisfaction and a healthier and improved indoor environment.

Applications of Thermal Energy Storage in Saudi Arabia

In Saudi Arabia, the heating, ventilating and air conditioning (HVAC) system typically accounts for 65% of the total electrical energy consumption in buildings. This is due to a very high ambient temperature which persists for a long period of time in a summer season. Moreover, gas turbines efficiency decrease also with the high ambient temperatures. In the HVAC industry cool storage, or commonly known as Thermal Energy Storage (TES) is the most preferred demand side management (DSM) technology for shifting cooling electrical demand from peak daytime periods to off-peak night-time. The most popular and well-suited TES concept for Saudi Arabia is either chilled water or ice storage system, depending upon the applications and the required storage capacity. This paper shows how TES offers a means of reducing the electrical demand in large commercial buildings. Additionally, it is seen that efficiencies of the air cooled chillers are increased if they run overnight. Similarly efficiencies of gas turbine is also increased when a TES based pre-cooled air is used as an inlet to the turbine. This paper also discusses favouring conditions and other aspects of cool storage applications in Saudi Arabia. TES economics are considered and a cost analysis is presented to illustrate the potential savings that can be achieved by the use of TES in Saudi Arabia. Copyright © 1999 John Wiley & Sons, Ltd.