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Energy performance contracts (EPC) are types of agreements in which a service provider guarantees that customers' buildings will achieve a specified energy performance (i.e., minimum energy savings) to reduce the risk of their investment in energy efficiency improvements. EPC requires prediction of future energy consumption of the building, at the design stage, before construction or major retrofit. To this end, building energy simulations taking into account all the major energy-using components are performed. In particular, fans can contribute significantly to the total building consumption. The overall efficiency of fans is the combination of three factors: mechanical, motor, and variable frequency drive (VFD). Manufacturers usually provide fan mechanical efficiency curves for a broad operating range. In contrast, motor and VFD efficiencies are generally given at rating conditions only. To represent part-load conditions, correlations are typically used to estimate motor and VFD efficiency variations, to evaluate the overall electricity consumption. The first aim of this study is to evaluate existing correlations for motor and VFD efficiency as a function of load and speed, by comparison with manufacturer data, for a vendor that has shared its detailed test data. While VFD efficiency correlations from the literature provide reasonable accuracy against real data, motor correlations under predict actual motor efficiency at low loads. The second aim of the paper is to improve such correlations using Bayesian inference to fit the available data. [ABSTRACT FROM AUTHOR]

The decrease in heat demand in low energy buildings and the development of new heating, ventilation and air conditioning systems call for a re-examination of the usual modelling approaches in building simulation. A comparison methodology is developed to confront different modelling approaches with experimental data. The methodology is applied to four models of variable speed air-to-air heat pumps. Two classical empirical models (a static and a dynamic one) and a detailed physical model are selected. Moreover, a simplified physical model is developed for this study. The detailed control of the experimental heat pump and a model of the defrost cycle are given. The four modelling approaches are compared toin situmeasurements for outdoor temperatures betweenandincluding defrost phases. The simulation results are analysed from the point of view of building energy simulation. [ABSTRACT FROM PUBLISHER]

Abstract: Dwellings represent more than 40% of final energy consumption in France. They also present the highest potential of energy savings, while using technology already substantiated, without huge investments, in contrast to other sectors. Ventilation is one of the main sources of heating loss in buildings, so recovering heat from exhaust air could reduce significantly heating loads. In airtight and well insulated buildings, heat recovery ventilation (HRV) systems are often recommended to save heat energy. However, these savings should be balanced against the electrical power requirements of the fans. A HRV unit is modeled, using TRNSYS, and studied in order to characterize its annual performance when integrated into residential and commercial low energy buildings. The energy performance of HRV is compared to one of the standard ventilation systems. This comparison is based on the heating, cooling and ventilation primary energy consumption for different climatic zones. It is found that the adequacy of using HRV system depends on the building types, the heating loads and ventilation device characteristics. A sensitivity analysis by simulation is undertaken to investigate the influence of exchanger efficiency and specific fan power on the global energy performance of the HRV system. [Copyright &y& Elsevier]

Abstract: A desiccant wheel model has been developed in the aim to be adapted to building simulation tools. This model fulfils several criteria such as simplicity of parameterization, accuracy, possibility to characterize the equipment under all operation conditions and low computation time. The method of characteristics has been applied to the heat and mass transfer partial differential equations. This transformation provides new equations which are similar to those of a rotary heat exchanger. Then, the model is described by the Effectiveness-NTU method and it is identified from only one nominal rating point. The model has been compared to experimental and manufacturers’ data for a broad range of operating conditions. A good agreement has been found. [Copyright &y& Elsevier]

Abstract: A desiccant-wheel behavioural model has been developed. This model fulfils several criteria, such as simplicity of parameterization; accuracy; ability to characterize the equipment behaviour under all operation conditions; and short computation time. The method of characteristics has been applied to the heat-and-mass transfer partial-differential equations. This transformation provides equations which are similar to those of a rotary heat-exchanger. Then, the model is described by the effectiveness-NTU method and identified from only one nominal-rating point. The model predictions have been compared with experimental and manufacturers’ data for a broad range of operating conditions. Good agreement has been found. [Copyright &y& Elsevier]

A simplified model for indirect cooling towers behaviour is presented. The model is devoted to building simulation tools and fulfils several criteria such as simplicity of parameterisation, accuracy, possibility to model the equipment under various operation conditions and short computation time. On the basis of Merkel''s theory, the model is described by using the Effectiveness-NTU method. The model introduces only two parameters, air-side and water-side heat-transfer coefficients which can be identified from only two rating points, data easily available in manufacturers'' catalogues. Thus, the model allows one to estimate energy and water consumptions under different operating conditions such as variable wet-bulb temperatures or variable airflow rates. [Copyright &y& Elsevier]

Highlights: [•] Six heating systems are compared in a low energy house for different climates. [•] MCHP and electric HPs are more efficient than gas or wood boilers and absorption HP. [•] The absorption HP would be the most efficient if small size products were developed. [•] The merit order of electric heat pumps drops with the current oversizing practice. [•] The intermittent heating has a limited interest in low energy houses. [ABSTRACT FROM AUTHOR]