Imperial College London

Dr Salvador Acha

Faculty of EngineeringDepartment of Chemical Engineering

Research Fellow
 
 
 
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Contact

 

+44 (0)20 7594 3379salvador.acha Website

 
 
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Location

 

c410Roderic Hill BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
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29 results found

Acha S, Mariaud A, Shah N, Markides CNet al., 2018, Optimal design and operation of distributed low-carbon energy technologies in commercial buildings, ENERGY, Vol: 142, Pages: 578-591, ISSN: 0360-5442

JOURNAL ARTICLE

Delangle A, Lambert RSC, Shah N, Acha S, Markides CNet al., 2017, Modelling and optimising the marginal expansion of an existing district heating network, ENERGY, Vol: 140, Pages: 209-223, ISSN: 0360-5442

JOURNAL ARTICLE

Mariaud A, Acha S, Ekins-Daukes N, Shah N, Markides CNet al., 2017, Integrated optimisation of photovoltaic and battery storage systems for UK commercial buildings, APPLIED ENERGY, Vol: 199, Pages: 466-478, ISSN: 0306-2619

JOURNAL ARTICLE

Acha Izquierdo S, Cedillos D, Shah N, 2016, Optimal Technology Selection and Operation of Bio-methane CHP Units for Commercial Buildings, 2016 ASHRAE Annual Conference, Publisher: ASHRAE

This paper explores the optimal implementation of bio-methane fuelled combined heat and power (CHP) systems to satisfy heat and electricity demands ofcommercial buildings; with the overarching goal of making cost-effective investments and decarbonizing building operations. The research work consisted inthe development of a CHP technology selection and operation (TSO) optimization model. Its results can be utilized to develop a strategy for investment inbio-methane CHP projects for a portfolio of buildings. The TSO model enables a new approach for the selection and operation of CHP units thatencompasses whole life costing, carbon emissions as well as real-time energy prices and demands, providing a more comprehensive result than current methods.Utilizing historic metered energy demands, projected energy prices and a portfolio of available CHP technologies, the mathematical model simultaneouslysolves for an optimal CHP unit selection and operational strategy for a determined building based on a preferred objective: minimizing cost, minimizingGHG emissions, or a mix of both. Results of this model prove that attractive cost and emissions savings are possible through the optimal selection andoperation of CHP technologies fuelled by bio-methane

CONFERENCE PAPER

Acha Izquierdo S, Dalpane P, Shah N, 2016, Operational and Economic Analysis of GSHP Coupled with Refrigeration Systems in UK Supermarkets, 2016 ASHRAE Annual Conference, Publisher: ASHRAE

Ground Source Heat Pumps (GSHP) are capable of reducing energy consumption by operating at higher efficiencies than conventional gas systems, especiallyif coupled with refrigeration units such as in supermarkets. In principle, the heat rejected by refrigerators can be harnessed to raise the efficiency of the heatpumps. This paper presents the results of an operational and economic analysis conducted on this innovative system. Overall, the efficiency of all the GSHPsystems under consideration appears to be above the eligibility threshold for the UK Government’s incentive (Renewable Heat incentive, RHI), with theaverage Seasonal Coefficient of Performance (SCOP) of the stores being 3.0 in 2014. From an economic perspective, such average performance leads tomore than £120,000 of operational savings per year compared to gas boiler systems. Calculations show an investment Payback Time (PBT) of less than8 years. Finally, the paper highlights potential cost reductions achievable through operational and design modifications. Overall results show that GSHPcoupled with refrigeration systems present sound fundamentals to be considered as an attractive investment opportunity for food retailers.

CONFERENCE PAPER

Acha Izquierdo S, Shah N, 2016, Re-commissioning Energy Conservation Measures in Supermarkets: An UK Case Study, CLIMA 2016, Publisher: Aalborg University, Department of Civil Engineering

Considering the UK’s ambitious carbon emission reduction target (i.e. reducingCO2e emissions by 80% below 1990 levels by 2050), it is evident that energyconservation measures in food retail buildings can substantially contribute inmeeting this goal. Supermarket buildings in particular are complex energy systemsthat require careful study to make sure they perform in a sensible manner. Retailpressure on quick store delivery makes commissioning teams prone to mistakes andtherefore, despite stores being newly built or refurbished, their systems are notideally set up. This circumstance makes buildings underperform by excessivelyconsuming energy which is a detriment in terms of costs and carbon emissions. Theobjective of this paper is to disseminate the energy savings that can come from lowcost re-commissioning measures linked to best operating practices; this is achievedby gathering insights from the monitoring of refrigeration, HVAC, and lightingsystems. A case study in a 3,300 m2 UK supermarket showcases the energyperformance of these systems before and after measures are implemented. The trialsconducted have the feature of being holistic by working closely with store staff andcontractors. Results show store energy use in Year 2 improved by 20% against itsbenchmark (Year 1); consequently reducing the carbon footprint and energy bills ofthe building. Furthermore, the learning’s are transferable and have quick paybackperiods; thus making clear a large potential exists in reducing energy bills ofretailers while simultaneously contributing to carbon mitigation in the UK.

CONFERENCE PAPER

Acha S, Bustos-Turu G, Shah N, 2016, Modelling Real-Time Pricing of Electricity for Energy Conservation Measures in the UK Commercial Sector, IEEE International Energy Conference (ENERGYCON), Publisher: IEEE, ISSN: 2164-4322

CONFERENCE PAPER

Acha S, Du Y, Shah N, 2016, Enhancing energy efficiency in supermarket refrigeration systems through a robust energy performance indicator, INTERNATIONAL JOURNAL OF REFRIGERATION-REVUE INTERNATIONALE DU FROID, Vol: 64, Pages: 40-50, ISSN: 0140-7007

JOURNAL ARTICLE

Alvarado DC, Acha S, Shah N, Markides CNet al., 2016, A Technology Selection and Operation (TSO) optimisation model for distributed energy systems: Mathematical formulation and case study, APPLIED ENERGY, Vol: 180, Pages: 491-503, ISSN: 0306-2619

JOURNAL ARTICLE

Bustos-Turu G, van Dam KH, Acha S, Markides CN, Shah Net al., 2016, Simulating residential electricity and heat demand in urban areas using an agent-based modelling approach, IEEE International Energy Conference (ENERGYCON), Publisher: IEEE, ISSN: 2164-4322

CONFERENCE PAPER

Acha Izquierdo S, Loh C, Noye S, Shah Net al., 2015, Retail Building Thermal Efficiency Improvement Through an Enhanced Re-Commissioning Framework, 2015 ASHRAE Annual Conference, Publisher: ASHRAE, ISSN: 1088-8586

End-use energy efficiency is recognized as a predominant contributor to achieve UK carbon reduction target that is still far from reach today. Theopportunity in retail buildings is apparent, especially supermarkets that account for 4 MtCO2e of total UK carbon footprint. This paper outlinesan enhanced re-commissioning (Re-Cx) framework that aims to mitigate supermarkets with poor energy performance, known as “cold-stores”. Theframework delivers a holistic approach with four critical strategies – Identification, Monitoring, Rectification and Prevention in sustainingsupermarket thermal efficiency throughout its operational lifecycle. This includes a comprehensive store characterization to identify “cold-store”, keyperformance indicators (KPIs) proposal for supermarket thermal efficiency monitoring, a cost-effective fault indication flowchart development for“cold-store” rectification, and the introduction of a novel Re-Cx and maintenance integration approach to prevent “cold-store” in a sustainablemanner. A case study is carried out on 350 stores from one of the biggest UK supermarket chains. Seven “cold-stores” are identified from thecomprehensive store benchmarking and characterization analysis. These results are also validated through the proposed KPIs. Moreover, acomparison between EnergyStar Re-Cx strategies and the supermarket maintenance procedures found 80% of the Re-Cx measures could beintegrated into the maintenance activities. This ascertains the feasibility of the suggested integration approach. In a nutshell, this framework bringsa new perception to retail Re-Cx regime, which can be implemented to effectively identify, monitor, rectify and prevent “cold-stores”.

CONFERENCE PAPER

Andrianopoulos E, Acha S, Shah N, 2015, Achieving net zero carbon performance in a commercial building by aligning technical and policy alternatives - An UK case study

Quantifying a detailed inventory of carbon emissions attributed to a retail building is of vital importance to minimize (or offset) their environmental impact. However, quantifying the environmental impact of a commercial building's operation has attracted great controversy regarding both the carbon fields considered within the building's operational boundaries and the different responsibility levels among participants. This paper details a robust framework on how businesses operating under UK policy can measure the operational carbon performance attributed to their buildings. Furthermore, the paper investigates how the quantified emissions can be offset in order to reach net zero carbon operational performance. The analysis is structured in three levels and its applicability is showcased through an industry-sourced example of a supermarket building. The first level aims to classify building emissions according to their sources namely electricity consumption, on-site fuel burning, water supply, transport operations and waste management & disposal. The developed carbon fields' analysis technique treats a commercial building as an on-going energy consuming system where different operations (e.g. transport activities) contribute to the building's commercial use as well as to its operational carbon footprint. In the second level, the study compares a food store's carbon footprint across different supply and operation scenarios in order to analyse how each sector can influence emissions. In the third stage, the research details the carbon off-setting achieved by installing a bioenergy combined heat and power (CHP) unit in its premises and thus achieving net zero carbon performance. Results illustrate the environmental benefits for different CHP capacity solutions. These results show how urban cogeneration plants can de-carbonise UK buildings. However, the UK carbon accounting framework is still evolving and therefore is constantly subject to regulatory changes. Con

CONFERENCE PAPER

Caritte V, Acha S, Shah N, 2015, Enhancing Corporate Environmental Performance Through Reporting and Roadmaps, BUSINESS STRATEGY AND THE ENVIRONMENT, Vol: 24, Pages: 289-308, ISSN: 0964-4733

JOURNAL ARTICLE

Bustos-Turu G, van Dam KH, Acha S, Shah Net al., 2014, Estimating Plug-in Electric Vehicle Demand Flexibility through an Agent-Based Simulation Model, 5th IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT Europe), Publisher: IEEE, ISSN: 2165-4816

CONFERENCE PAPER

Acha S, 2013, Modelling Distributed Energy Resources in Energy Service Networks, Publisher: IET, ISBN: 9781849195591

Focuses on modelling two key infrastructures (natural gas and electrical) in urban energy systems with embedded technologies (cogeneration and electric vehicles) to optimise the operation of natural gas and electrical infrastructures under ...

BOOK

Acha S, Mavromatidis G, Caritte V, Shah Net al., 2013, Effective low-cost energy saving strategies in supermarkets: An UK case study

Supermarket buildings are complex energy systems that require careful study to make sure they perform in a sensible manner. The retail pressure of delivering stores in a short time makes engineering commissioning teams prone to mistakes and therefore, despite stores being newly built and carefully designed, their systems are not ideally set up; thus making the building underperform from day one. Consequently, energy savings are within easy reach if an effort is made to re-evaluate stores shortly after their opening date. This paper focuses on how adequate monitoring and good housekeeping can lead to effective energy saving strategies for a better management of services such as lighting, refrigeration, heating and ventilation. Additionally, a focused effort in curtailing energy use in supermarkets can also seriously reduce operational carbon related emissions; an ever-growing concern for retailers in an environment where sustainability practice is highly valued by consumers. A case study of a 35,000 ft2 supermarket located in the south-east of England serves as a vehicle to present and quantify effective, low-cost energy saving strategies. Extensive monitoring capabilities allow us to set a benchmark for all systems which then serves to assess the effectiveness of trials performed. Trials consist of: a) enhancing the dimming capabilities of the lighting system by improving sensor location and code, b) improving settings of fans and boiler system that reduce heating and ventilation requirements, and c) advocating the proper use of night-blinds in cabinets coupled with suction optimization of compressors that save energy use in the refrigeration system. All of these live trials have the feature of working closely with store staff and management, specialised contractors and academics. The synergy of parties allows the energy trials to succeed since aside from having solid technical foundations they have the full support from the people that work day in and day out in th

CONFERENCE PAPER

Acha S, Mavromatidis G, Caritte V, Shah Net al., 2013, Techno-economical technology assessment for operational zero carbon supermarkets

Supermarkets are very energy intensive buildings resulting in a large carbon footprint that needs to be addressed. Demand reduction measures are not sufficient, since even after intensive actions have been taken, the remaining footprint is still significant. Therefore, comparative technology frameworks that focus on the energy supply side are necessary in order to reduce carbon emissions. These frameworks need to be straightforward as decision makers generally lack engineering expertise. This paper focuses on depicting the various challenges low carbon technologies need to overcome to be successfully applied in supermarkets while also identifying core technologies that can deliver sustainable supermarkets today. A review of multiple technologies is presented and graded according to standard criteria. A generic UK supermarket is used to describe the different store services and to characterize energy load profiles which explain the complex relationship between electricity and heat requirements the building has throughout a year. A business as usual store design is presented to benchmark current key performance indicators (KPIs) concerning emissions, capital and operational costs; these KPIs can be used by decision makers when considering the implementation of low carbon technologies. Results of the analysis indicate designing and delivering a zero carbon supermarket is possible, however careful detail must be dedicated to address multiple issues that come along with project implementation; such as the manner in which the energy systems should be operated or potential hazards to customers or employees. Useful guidelines on how energy technologies can complement each other are included. Overall, defining the technologies going into a sustainable building is just one step towards achieving a zero carbon supermarket, nonetheless it is its most critical stage, where trade-offs are assessed and priorities are given to guarantee the success and longevity of such ambitious p

CONFERENCE PAPER

Acha S, Van Dam KH, Shah N, 2013, Spatial and temporal electric vehicle demand forecasting in central London

If electricity infrastructures are to make the most of electric vehicle (EV) technology it is paramount to understand how mobility can enhance the management of assets and the delivery of energy. This research builds on a proof of concept model that focuses on simulating EV movements in urban environments which serve to forecast EV loads in the networks. Having performed this analysis for a test urban environment, this paper details a case study for London using an activity-based model to make predictions of EV movements which can be validated against measured transport data. Results illustrate how optimal EV charging can impact the load profiles of two areas in central London - St. John's Wood & Marylebone/Mayfair. Transport data highlights the load flexibility a fleet of EVs can have on a daily basis in one of the most stressed networks in the world, while an optimal power flow manages the best times of the day to charge the EVs. This study presents valuable information that can help in begin addressing pressing infrastructure issues such as charging point planning and network control reinforcement.

CONFERENCE PAPER

Keirstead J, Shah N, 2013, Urban Energy Systems: An Integrated Approach, Publisher: Routledge, ISBN: 9780415529020

Energy demands of cities need to be met more sustainably. This book analyses the technical and social systems that satisfy these needs and asks how methods can be put into practice to achieve this.

BOOK

Mavromatidis G, Acha S, Shah N, 2013, Diagnostic tools of energy performance for supermarkets using Artificial Neural Network algorithms, ENERGY AND BUILDINGS, Vol: 62, Pages: 304-314, ISSN: 0378-7788

JOURNAL ARTICLE

Acha S, Shah N, Ashford J, Penfold Det al., 2012, Optimal lighting control strategies in supermarkets for energy efficiency applications via digital dimmable technology, Pages: 196-212

Electricity consumption in the UK commercial sector accounts for 19% of total annual electricity demand. This implies any step taken towards energy efficiency applications for commercial buildings can generate important reductions in both energy use and carbon emissions. Sainsbury's supermarkets, one of the UKs largest grocers, recognises the challenges climate change brings to businesses and hence is conducting efforts to reduce the operational carbon footprint of their stores. Lighting in stores is an essential service and is an important component of a stores power demand; ranging from 15 to 35% based on design features. This paper details the innovative lighting control application Sainsbury's is currently employing in its new stores with the objective to maximise the benefits digital dimmable technology possesses. Basic lighting concepts are described which explain the priorities supermarkets have when using this service, while the tradeoffs of using digital signal interface (DSI) controls are also discussed. The non-linear relationship between DSI settings, lux drawn from ballasts, and power consumed by the system are showcased as a proper understanding of this concept is paramount in achieving energy savings. In addition, using a Sainsbury's 3,300 m2 eco-store, a thorough case study is presented in which various lighting strategy settings are applied; having very attractive results in monetary, energy, and environmental metrics without being detrimental to the shopping experience. Hence, it is proven digital dimmable technology controls can effectively provide 20 to 25% savings in lighting services if sensors and settings are established properly. Furthermore, due to the robust and fast response capability digital dimming offers, the authors argue this technology is suitable for demand side management applications that can greatly benefit the operability of the grid and as a consequence provide an additional revenue stream for businesses in a smart-grid envir

CONFERENCE PAPER

Acha S, van Dam KH, Shah N, 2012, Modelling Spatial and Temporal Agent Travel Patterns for Optimal Charging of Electric Vehicles in Low Carbon Networks, General Meeting of the IEEE-Power-and-Energy-Society, Publisher: IEEE, ISSN: 1944-9925

CONFERENCE PAPER

Acha S, Green TC, Shah N, 2011, Optimal charging strategies of electric vehicles in the UK power market

In order to gain the most from their deployment, it is imperative for stakeholders to exploit the main benefits electric vehicles bring to utilities. Therefore, this paper focuses on the aspects required to model the management of electricity supply for electric vehicles. The framework presented details a time coordinated optimal power flow (TCOPF) tool to illustrate the tradeoffs distribution network operators (DNO) might encounter when implementing various load control approaches of electric vehicles. Within an UK context, a case study is performed where the TCOPF tool functions as the intermediary entity that coordinates cost-effective interactions between power markets, network operators, and the plugged vehicles. Results depict the stochastic but optimal charging patterns stakeholders might visualise from electric vehicles in local networks as they are operated to reduce energy and emission costs. Furthermore, results show current emission costs have a negligible weight in the optimisation process when compared to wholesale electricity costs. © 2011 IEEE.

CONFERENCE PAPER

Acha S, Green TC, Shah N, 2010, Effects of Optimised Plug-in Hybrid Vehicle Charging Strategies on Electric Distribution Network Losses, 2010 IEEE PES Transmission and Distribution Conference and Exposition - Smart Solutions for a Changing World, Publisher: IEEE

CONFERENCE PAPER

Acha S, Green TC, Shah N, 2010, Techno-economical Tradeoffs from Embedded Technologies with Storage Capabilities on Electric and Gas Distribution Networks, IEEE-Power-and-Energy-Society General Meeting, Publisher: IEEE, ISSN: 1944-9925

CONFERENCE PAPER

Acha S, Green TC, Shah N, 2009, Impacts of plug-in hybrid vehicles and combined heat and power technologies on electric and gas distribution network losses

Distribution network operators (DNOs) require strategies that can offset the tradeoffs new embedded technologies have on their assets. This paper employs modelling to show that through control device manipulation, gas and electric (G & E) network operators can influence savings in energy losses under the presence of plug-in hybrid vehicles (PHEVs) and combined heat and power technologies (CHPs). An integrated gas and electric optimal power flow (OPF) tool is introduced to undertake various case studies. The OPF tool evaluates the technical impacts experienced in the networks when DNOs apply a "plug and forget" operation strategy and then compares the results against a "loss minimisation" strategy. Results show the benefits in applying different strategies are more considerable in electric networks than in gas networks. The study corroborates that an integrated G & E analysis offers a fresh perspective for stakeholders in evaluating energy service networks performance under different operation strategies.

CONFERENCE PAPER

Acha Izquierdo S, Hernandez Aramburo C, 2008, Integrated Modelling of Gas and Electricity Distribution Networks with a High Penetration of Embedded Generation, CIRED Seminar 2008: SmartGrids for Distribution, Publisher: IET, ISSN: 0537-9989

Gas-based combined heat and power (CHP) has maturedenough to be regarded as the next evolutionary step inpromoting energy efficiency use in the urban environment.Although its potential market is increasing, little researchhas been conducted into the combined technical effects thata high penetration of these units may have on both naturalgas and electric (G&E) distribution networks. This paperpresents a power flow tool that performs a simultaneousassessment on some technical impacts that a highpenetration of heat-driven cogeneration units may have onG&E networks. A case study is presented and results showthat as expected, the gas demand increases as well as thelosses associated with its delivery, while the opposite effectsoccur in the electrical system. However, less evident is theload profile variations distribution networks will experienceand that overall energy losses will vary according to theCHP penetration and the type of technology used. The studyshows that an integrated G&E analysis offers a freshperspective in quantifying the effects cogenerationtechnologies will have on energy distribution networks.

CONFERENCE PAPER

Acha Izquierdo S, Shah N, Bos J, Cost effective low carbon store analysis and replication, CIBSE Technical Symposium 2015

This paper explores how low carbon buildings can be easily and cost effectivelyreplicated for a commercial retailer. The analysis investigates zero carbonsupermarkets using bio-methane combined heat and power (CHP). Results showthat CHP & district heating is the most cost effective design for a sustainablesupermarket. However, its implementation depends greatly on third parties and thusis not easy to replicate. The second best alternative is to use a CHP coupled with anOrganic Rankine Cycle (ORC) when the buildings heat-to-power ratio is below 0.5.Otherwise, a CHP with no heat recovery solution is deemed best. Overall, the mostcost effective ZCS projects are the ones implemented in stores with a high heat-topowerratio, high energy intensities and large surface floor area.

CONFERENCE PAPER

Acha S, van Dam KH, Keirstead J, Shah Net al., Integrated modelling of agent-based electric vehicles into optimal power flow studies, Frankfurt, Germany

CONFERENCE PAPER

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