Exerav as a Parameter for Buildina Enerav Assessment

The energy and environmental impacts resulting from the buildings sector are one of the impending problems which address the international action. The main strategies implemented to answer to this problem are the energy efficiency improvement, the CO2 emissions reduction and the renewable energy share increase in the energy mix. The key subject discussed in this paper is the ＂building energy impact＂, aimed to leading the building sector towards the energy efficiency improvement. The paper＇s aim is to show that an energy assessment is not able to give a consistent evaluation of building energy use, and it could be misleading. Therefore, the paper proposes the exergy assessment as complementary evaluation method, in order to achieve a complete description of the concept ＂building＇s energy impact on the environment＂. In the first section, we describe the parameters currently used for the building energy assessment, focusing on the primary energy index and the CO2 emissions index. In the second section, we introduce the exergy as a complementary index. This index is a possible answer to the problems previously identified. Finally, in the third section, we present three test-cases, analyzed through transient simulation software TRNSYS. The purpose of the test-cases analysis is to show the difference between energy and exergy assessment.

A Review on the Heat Pipe Photovoltaic/Thermal(PV/T)System

The Photovoltaic/thermal(PV/T)system combines the conventional PV panel with solar collector into one integrated system,which could achieve the function of generating power and providing thermal energy at the same time.Recently,it has become the most promising solar system for building applications.Most of the PV/T systems use water as the coolant,which could cause freezing problem in winter.To overcome this problem,the heat pipe PV/T system is developed to provide electrical and thermal energy stably without the seasonal barrier.Although some published review works have involved this type of PV/T system,they just stated a simple introduction on it,acting as a small part of their works.This paper focuses on the heat pipe PV/T system independently and provides a comprehensive and in-depth analysis of its performance.Firstly,the structure and operational principles of the heat pipe PV/T module and system are introduced concisely.Then the features and performance of different types of heat pipe PV/T systems,i.e.,integral heat pipe,loop heat pipe,and pulsating heat pipe PV/T system,are presented and analyzed.This is followed by the review on the performance of the systems which combine heat pipe PV/T module and other devices.Finally,the research gaps in this field are identified,and some future research trends and directions are recommended.

Experimental Investigation on an Absorption Heat Transformer for Production of Hot Water or Steam Generation

The absorption heat transformer is widely used to utilize low-temperature waste heat in the field of distributed energy,industrial processing,and long-distance indoor heating,because it can upgrade energy level and deliver heat to heated medium.In this work,an experimental system of a vertical single-stage LiBr/H2O absorption heat transformer was established to study its performance in the case of producing high-temperature water or low-pressure steam generation under different heating water flow rates.The useful output heat,coefficient of performance,exergy coefficient of performance,and gross temperature lift of the single-stage heat transformer have all been tested.The results show that the absorber cannot directly generate low-pressure steam under the condition of counter-flow heat exchange but can obtain more useful output heat.The largest useful output heat is 20.3 kW,which is higher than that in the case of parallel-flow heat exchange.The generation of low-pressure steam has certain requirements on the mode of heat transfer.The largest internal gross temperature lift of 28.1℃corresponds to the smallest coefficient of performance of 0.22 when the heating water flow rate is 2.1 m3/h.The performance of the single-stage absorption heat transformer can be improved to some extent by increasing the heating water flow rate.