Stochastic model-predictive control of district-scale building energy systems using SpineOpt

Model predictive control of buildings is a vibrant field, but mostly focuses on buildings as “pricetakers”. While simplified resistance-capacitancebuilding models have previously been employed within large-scale energy system frameworks to analyse market impacts, tools for stochastic programming are scarce. In this work, we demonstrate the viability of the SpineOpt energy system modelling framework for stochastic model predictive control of an imaginary six-building district using different weather and price forecasts, achieving reasonable performance and cost savings comparable with existing literature. The used methods could be scaled up to city or nation scale energy system studies, or be utilised for electricity market bidding of aggregated building flexibility

Editorial: Special Issue “Net-Zero/Positive Energy Buildings and Districts”

The important goal of decarbonization of communities and cities has resulted in the emergence of new concepts and implementations of Net-Zero/Positive-Energy Buildings and Districts (NZPEBD) in recent years [...

Stochastic model-predictive control of district-scale building energy systems using SpineOpt

Model predictive control of buildings is a vibrant field, but mostly focuses on buildings as “pricetakers”. While simplified resistance-capacitancebuilding models have previously been employed within large-scale energy system frameworks to analyse market impacts, tools for stochastic programming are scarce. In this work, we demonstrate the viability of the SpineOpt energy system modelling framework for stochastic model predictive control of an imaginary six-building district using different weather and price forecasts, achieving reasonable performance and cost savings comparable with existing literature. The used methods could be scaled up to city or nation scale energy system studies, or be utilised for electricity market bidding of aggregated building flexibility

Energy Flexibility and towards Resilience in New and Old Residential Houses in Cold Climates: A Techno-Economic Analysis

One of the main sectors that contribute to climate change is the buildings sector. While nearly zero-energy buildings are becoming a new norm in many countries in the world, research is advancing towards energy flexibility and resilience to reach energy efficiency and sustainability goals. Combining the energy flexibility and energy resilience concept is rare. In this article, we aim to investigate the effect of energy efficiency in a new single-family building on the energy flexibility potential and resilience characteristics and compare these with those for an old building in the cold climate of Finland. These two objectives are dependent on the buildings’ respective thermal mass. The heat demands of the two buildings are compared. Their technical and economic performance are calculated to compare their flexibility and resilience characteristics. Dynamic simulation software is used to model the buildings. The results show that the old building has better flexibility and higher energy cost savings when including the energy conservation activation strategy. In the old building, savings can be around EUR 400 and flexibility factor can be around 24–52% depending on the activation duration and strategy. The new building, due to higher efficiency, may not provide higher energy cost savings, and the energy conservation activation strategy is better. In the new building, savings can be around EUR 70 and the flexibility factor reaches around 7–14% depending on the activation duration and strategy. The shifting efficiency of the new house is better compared to that of the old house due to its higher storage capacity. For energy resilience, the new building is shown to be better during power outages. The new building can be habitable for 17 h, while the old building can provide the same conditions for 3 h only. Therefore, it is essential to consider both energy flexibility and resilience as this can impact performance during the energy crisis.<br/

Energy flexibility and resiliency analysis of old and new single family buildings in Nordic climate

Climate change and energy crises are the two challenges faced by societies. To address these issues, buildings have to be both flexible and resilient. The aim of this paper is to simulate and compare the performance of two types of a single-family house, i.e. an old building (1970) and a new building (2000), integrated with and without photovoltaic (PV) for the two objectives of energy flexibility and energy resilience in the cold climate of Finland. Depending on the PV size, it is found that the old building has a flexibility factor of up to 84% and the new building has 17% and the energy cost reduced. For resilience, the PV made the old building robustness period 15 h and the new building 32 h. With the PV, the amplitude of the buildings failure is lower and the recovery speed is faster. To meet future sustainability and resilience goals, energy resilience and flexibility for different types of buildings have to be studied together, which are impacted by both the characteristics of the bulding’s thermal mass and the onsite energy generation

Performance analysis of heat transfer processes from wet and dry surfaces : cooling towers and heat exchangers

The objective of this work is to study the thermal and hydraulic performance of evaporatively cooled heat exchangers, including closed wet cooling towers, and dry tube heat exchangers with various geometries. Applications utilising such equipment exist in almost every thermal process. The investigation includes theoretical analysis, computational approaches, and experimental measurements. In this work, a computational model is presented for the thermal performance of closed wet cooling towers intended for use in conjunction with chilled ceilings in cooling of buildings. A variable spray water temperature inside the tower is assumed. A prototype tower was subjected to experimental measurements to find its characteristics. Optimisation of the tower geometry and flow rates for specified design conditions is carried out in order to achieve a high value of the coefficient of performance (COP). Results from a global simulation program (including the tower model, a transient building model, a chilled ceiling model, system control etc.) show that closed wet cooling towers can be used with chilled ceilings to achieve acceptable indoor air temperatures in locations having suitable climatic conditions. This is supported by published results from a performance test of an office building using this method of cooling. Simplification of the model is obtained by assuming a constant temperature for the spray water. The tower performance predicted by the simplified model and the computational model shows comparable results. The results of the simplified model are then incorporated with Computational Fluid Dynamics (CFD) to assess the temperature distribution inside the tower. It is shown that CFD can be implemented to study the effect of air distribution inside the tower on its performance. The effect of introducing plate fins in evaporatively cooled plain circular tubes is experimentally studied. The measurement results show a 92% to 140% increase in the amount of heat transfer for the finned tubes. This is accompanied by an increase in the pressure drop, so that an indication of the combined thermal hydraulic performance is found to be close for the two geometries. However, it shows higher heat transfer rates per volume for the finned tubes. The performance of oval tubes in the evaporatively cooled heat exchanger is then experimentally investigated. The measurement results for the oval tubes show good heat and mass transfer characteristics; its average mass transfer Colburn factor is 89% of that for the circular tubes. Furthermore, it shows low friction factor for the air flow, which is 46% of that for the circular tubes. It is concluded that the tested oval tube is better than the circular tubes in combined thermal hydraulic performance. The features of oval tubes appear clearer in a dry heat transfer process. Five shapes of dry oval tubes are experimentally investigated in a cross-flow of air. The measurement results for the oval tubes are compared with those for an equivalent circular tube. It is found that the Nusselt numbers NuD for the studied tubes are close for Reynolds numbers ReD < 4000. While for higher ReD, the NuD decreases with the increase of the oval tube axis ratio. The drag measurements indicate lower drag coefficients Cd avg for the oval tubes. It is revealed that the investigated oval tubes have favourable combined thermal-hydraulic performance, which is expressed in terms of (NuD / Cd avg). The ratio of (NuD / Cd avg) for the oval tubes to that for the circular tube is from 1.3 to 2.5.reviewe

Social Networking Applications: A Comparative Analysis for a Collaborative Learning through Google Classroom and Zoom

Recently, social network applications were developed intensively due to the increasing compaction and user demands. These applications provide different services to their users like learning, awareness, chatting with friends, sharing global news, etc. Simply, this work introduces the advantages of these software applications, specifically in the field of education during the COVID 19 spread. Google Classroom and Zoom meetings had gained the attention of many educational institutes for using them as a learning platform for students and educators. This research used two methodologies SWOT analysis and the information system success model of DeLone and McLean\u27s updated to evaluate the effectiveness of these applications. SWOT analysis was performed for the Zoom meetings and google classroom, then evaluated their effectiveness. Likewise, DeLone and McLean\u27s model was deployed for evaluation, an empirical survey was used and distributed in our college. The results were collected, analyzed, and studied using various statistical parameters. Practically, each application has its pros and cons. However, google classroom showed more functionality for the learning process than the Zoom application

A MILP Optimization Method for Building Seasonal Energy Storage: A Case Study for a Reversible Solid Oxide Cell and Hydrogen Storage System

A new method for the optimization of seasonal energy storage is presented and applied in a case study. The optimization method uses an interval halving approach to solve computationally demanding mixed integer linear programming (MILP) problems with both integer and non-integer operation variables (variables that vary from time step to time step in during energy storage system operation). The seasonal energy storage in the case study uses a reversible solid oxide cell (RSOC) to convert electricity generated by solar photovoltaic (PV) panels into hydrogen gas and to convert hydrogen gas back to electricity while also generating some heat. Both the case study results and the optimization method accuracy are examined and discussed in the paper. In the case study, the operation of the RSOC and hydrogen storage system is compared with the operation of a reference system without energy storage. The results of the study show that installing an RSOC and hydrogen storage system could increase the utilization of onsite renewable energy generation significantly. Overall, the optimization method presents a relatively accurate solution to the case study optimization problem and a sensibility analysis shows a clear and logical pattern