An investigation of air and water dual adjustment decoupling control of surface heat exchanger

The terminal equipment of central cooling system accounts for a significant proportion of the total system's energy consumption. Therefore, it is important to reduce the terminal equipment energy consumption in central air conditioning system. In this study, the difference of the effect of the chilled water flow rate and air supply rate on the surface cooler during the heat transfer process is taken into full account. Matlab/Simulink simulation software is used to model and simulate the heat transfer of surface cooler of the main terminal equipment of air conditioning system. Simulation tests and experimental validations are conducted by using variable chilled water flow rate and variable air supply rate control mode separately. The experiment results show that the simulation model can effectively predict the heat transfer performance of heat exchanger. Further, the study introduced a dual feedback control mode, which synchronously regulates the chilled water flow rate and air supply rate. Also, under certain conditions, the complex heat transfer process of the surface cooler can be decoupled, and single variable control pattern is used to separately regulate the chilled water flow rate and air supply rate. This can effectively shorten the system regulation time, reduce overshoot and improve control performance

Sub-hourly simulation of residential ground coupled heat pump systems

Residential Ground Coupled Heat Pump systems are usually characterised by an ON/OFF behaviour of the heat pump with typical cycling frequencies of 1 - 4 cycles per hour. The ground loop fluid pump has the same ON/OFF behaviour and the borehole heat exchanger operates either in full flow or no flow conditions. Typical hourly simulations of GCHP systems use steady-state models for the heat pump and the borehole fluid (transient models being used for buildings and heat transfer in the ground). This paper reviews the models used in typical hourly simulations as well as transient models that are available and compares the results obtained using the two classes of models within the TRNSYS simulation environment. Both the long-term energy performance and the optimum system design are compared. It is shown that using steady-state models leads to an overestimation of the energy use that ranges from a few percents with oversized borehole heat exchangers to 75% for undersized exchangers. A simple Life Cycle Cost analysis shows that using steady-state models can lead to selecting a very different design than the one that would have been selected using dynamic models

Specifications for modelling fuel cell and combustion-based residential cogeneration device within whole-building simulation programs

This document contains the specifications for a series of residential cogeneration device models developed within IEA/ECBCS Annex 42. The devices covered are: solid oxide and polymer exchange membrane fuel cells (SOFC and PEM), and internal combustion and Stirling engine units (ICE and SE). These models have been developed for use within whole-building simulation programs and one or more of the models described herein have been integrated into the following simulation packages: ESP-r, EnergyPlus, TRNSYS and IDA-ICE. The models have been designed to predict the energy performance of cogeneration devices when integrated into a residential building (dwelling). The models account for thermal performance (dynamic thermal performance in the case of the combustion engine models), electrochemical and combustion reactions where appropriate, along with electrical power output. All of the devices are modelled at levels of detail appropriate for whole-building simulation tools

Energy rating of a water pumping station using multivariate analysis

Among water management policies, the preservation and the saving of energy demand in water supply and treatment systems play key roles. When focusing on energy, the customary metric to determine the performance of water supply systems is linked to the definition of component-based energy indicators. This approach is unfit to account for interactions occurring among system elements or between the system and its environment. On the other hand, the development of information technology has led to the availability of increasing large amount of data, typically gathered from distributed sensor networks in so-called smart grids. In this context, data intensive methodologies address the possibility of using complex network modeling approaches, and advocate the issues related to the interpretation and analysis of large amount of data produced by smart sensor networks. In this perspective, the present work aims to use data intensive techniques in the energy analysis of a water management network. The purpose is to provide new metrics for the energy rating of the system and to be able to provide insights into the dynamics of its operations. The study applies neural network as a tool to predict energy demand, when using flowrate and vibration data as predictor variables

The influence of thermal storage on microgeneration flexibility

In a future power system, the ability to manipulate generation and load will be a critical factor in providing a secure and stable supply of electrical energy to consumers. Using a simulation-based approach, this study assesses the ability of thermal storage to help deliver flexibility in the operation of domestic micro-generation technologies without sacrificing householder comfort and convenience. A typical UK detached dwelling is modelled along with its heating system, which features a retro-fitted air source heat pump (ASHP). The model is used to determine the maximum possible temporal shift for different capacities and configurations of thermal storage, taking into account the influence of climate, building fabric, control settings and occupancy. The limits of time shifting are dictated by the living space temperature and the hot water temperature delivered to the occupants. The storage mechanisms examined are: the basic thermal inertia of the building fabric; increasing the space heating set point temperatures to increase fabric storage and inserting a dedicated thermal buffer between the ASHP and the heat distribution system. The simulation results indicate that back-shifting of the ASHP start/stop times of between one and two hours are possible without causing serious discomfort or inconvenience to the occupants

The influence of thermal storage on microgeneration flexibility

In a future power system, the ability to manipulate generation and load will be a critical factor in providing a secure and stable supply of electrical energy to consumers. Using a simulation-based approach, this study assesses the ability of thermal storage to help deliver flexibility in the operation of domestic micro-generation technologies without sacrificing householder comfort and convenience. A typical UK detached dwelling is modelled along with its heating system, which features a retro-fitted air source heat pump (ASHP). The model is used to determine the maximum possible temporal shift for different capacities and configurations of thermal storage, taking into account the influence of climate, building fabric, control settings and occupancy. The limits of time shifting are dictated by the living space temperature and the hot water temperature delivered to the occupants. The storage mechanisms examined are: the basic thermal inertia of the building fabric; increasing the space heating set point temperatures to increase fabric storage and inserting a dedicated thermal buffer between the ASHP and the heat distribution system. The simulation results indicate that back-shifting of the ASHP start/stop times of between one and two hours are possible without causing serious discomfort or inconvenience to the occupants

Building energy performance characterisation based on dynamic analysis and co-heating test

A demonstration zero-carbon neighborhood is being raised in the city of Kortrijk, Belgium in the framework of the ECO-Life project within the CONCERTO initiative. A holistic approach is applied to achieve the zero-carbon targets, considering all aspects that are relevant for energy supply. Accordingly, alongside the integration of renewable energy sources in the community, a low-temperature district heating system is being implemented to cover the heat demand. In this context, full scale testing of building thermal performances, by use of a co-heating test and flux measurements, can be useful to analyze the thermal performance of the building envelope in situ. For that reason, as part of a more general study regarding low-energy building, co-heating test, blower-door test and flux measurements in several apartments were executed. Therefore, the paper focuses on characterization of the thermal dynamic behavior of an apartment, as a first approximation of data analysis of a monitoring system involving whole buildings. In addition, in the present study, the capability of linear regression techniques to characterize the thermal behavior of a newly built low-energy apartment in Belgium is investigated. The strengths and weaknesses of different models are identified. The limitation and possibilities of regression models are evaluated in the face of their applicability as a simplified building equation model. The identified model structure is going to be used within a complex simulation model of an entire district heating system with around 200 dwelling. Finally, the potential of this kind of regression models to be used as part of the operational control scheme of a district heating system is presented

Advanced Exergy Analysis in the Dynamic Framework for Assessing Building Thermal Systems

This work applies the Dynamic Advanced Exergy Analysis (DAEA) to a heating and domestic hot water (DHW) facility supplied by a Stirling engine and a condensing boiler. For the first time, an advanced exergy analysis using dynamic conditions is applied to a building energy system. DAEA provides insights on the components’ exergy destruction (ED) by distinguishing the inefficiencies that can be prevented by improving the quality (avoidable ED) and the ones constrained because of technical limitations (unavoidable ED). ED is related to the inherent inefficiencies of the considered element (endogenous ED) and those coming from the interconnections (exogenous ED). That information cannot be obtained by any other approach. A dynamic calculation within the experimental facility has been performed after a component characterization driven by a new grey-box modelling technique, through TRNSYS and MATLAB. Novel solutions and terms of ED are assessed for the rational implementation of the DAEA in building energy installations. The influence of each component and their interconnections are valuated in terms of exergy destruction for further diagnosis and optimization purposes.BMWi, 03ET1218B, Anwendung exergiebasierter Methoden zur Verbesserung von Gebäudeenergiesysteme

Analysis and design of a drain water heat recovery storage unit based on PCM plates

© 2016. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/This paper is focused on the detailed analysis of a PCM plate heat storage unit with a particular configuration, looking for the maximum contact area with the fluid (water) and the minimum volume to be used in a real household application. In that sense, a numerical study of the thermal and fluid dynamic behaviour of the water flow and the PCM melting-solidification processes, together with the thermal behaviour of the solid elements of the unit, has been carried out. On the other hand, an experimental set-up has been designed and built to validate the numerical model and characterise the performance of the heat storage unit. The purpose of the numerical and experimental study is to present a series of results to describe the heat storage unit performance in function of the time. Thus, after a preliminary design study three different cases have been simulated and tested. A 7.2% of discrepancy between numerical results and experimental data has been evaluated for the heat transfer. The PCM heat storage unit designed is capable to store approx. 75% of the thermal energy from the previous process wasted water heat, and recover part of it to supply around 50% of the thermal energy required to heat up the next process.Peer ReviewedPostprint (author's final draft