Evaluation of the energy impact of PCM tiles in an Airport Terminal Departure hall

Copyright @ 2013 CIBSEIn most past studies, passive PCM (phase change materials) systems have been tested for relatively small office spaces where the airflow is of minimal consequence in the overall energy consumption of the space. This paper on the other hand, reports on the application of PCM tiles on the floor of an Airport terminal space, similar to London Heathrow Terminal 5 departure hall, where in such large open spaces, the influence of airflow is crucial for the evaluation of the energy performance of AC units. In this paper, the evaluation of the energy performance of PCM tiles is obtained through a coupled simulation of TRNSYS and CFD. TRNSYS simulates the AC unit and PID control systems, while CFD is used to simulate the airflow and radiation inside the terminal space. The phase change process is simulated in CFD using an in-house developed model which considers hysteresis effects and the non-linear enthalpy-temperature relationship of PCMs. Although, a displacement ventilation (DV) system is actually employed at Heathrow Terminal 5, this study also compares the performance of the PCM tiles for a mixed ventilation (MV) system. Due to large computing times associated with CFD, discrete time-dependent scenarios under different UK weather conditions are used. The yearly energy demand is then determined through the heating/cooling degree day concept using base temperatures of 18 and 23 °C for HDD and CDD, respectively, similar to the comfort temperature range in the Terminal. The results show that the use of PCM tiles on the floor of the Terminal departure hall can lead to annual energy savings of around 3% for the DV system and 6% for the MV system, corresponding to 174 MWh/year and 379 MWh/year for the Terminal building.This work was funded by the UK Engineering and Physical Sciences Research Council (EPSRC), Grant No: EP/H004181/1

Cool roof technology in London: An experimental and modelling study

This is the post-print version of the final paper published in Journal of Energy and Buildings. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.One of the primary reasons for the application of cool materials is their energy and associated environmental impact on the built environment. Cool materials are usually applied on the roof of buildings to reduce cooling energy demand. The relative benefits of this reduction depend on the construction of the building, external weather conditions and use of the building. This paper examines the impact from the application of a reflective paint on a flat roof in a naturally ventilated office building in the area of London, UK where the climate is moderate with high heating demand by buildings. The environmental conditions (internal/external air and surface temperatures) of the building were monitored before and after the application of the cool roof during the summer. It was found that internal temperatures were reduced after the application of the cool roof. The building was modelled using TRNSYS and the model was calibrated successfully using the measurements. A parametric analysis was carried out by varying the reflectivity and insulation of the roof and ventilation rate; the heating and cooling demand for a year was calculated using the Summer Design Year for London as the weather file. It was found that cooling demand is significantly reduced, heating demand is increased and the total energy savings vary between 1 and 8.5% relative to an albedo of 0.1 for the same conditions. In free floating (naturally ventilated) buildings summer comfort is improved but there is a penalty of increased heating energy during the winter. Thermal comfort can be improved by an average of 2.5 °C (operative temperature difference for a change of 0.5 in albedo) but heating demand could be increased by 10% for a ventilation rate of 2 air changes per hour. The results indicate that in the case of temperate climates the type, operation and thermal characteristics of the building should be considered carefully to determine potential benefits of the application of cool roof technology. For the examined case-study, it was found that a roof reflectivity of 0.6–0.7 is the optimum value to achieve energy savings in a cooled office, improve summer internal thermal conditions in a non-cooled office (albeit with some heating energy penalty). It indicates that it is a suitable strategy for refurbishment of existing offices to improve energy efficiency or internal environmental conditions in the summer and should be considered in the design of new offices together with other passive energy efficient strategies.Intelligent Energy Europe (IEE

Energy aspects and ventilation of food retail buildings

Worldwide the food system is responsible for 33% of greenhouse gas emissions. It is estimated that by 2050, the total food production should be 70% more than current food production levels. In the UK, food chain is responsible for around 18% of final energy use and 20% of GHG emissions. Estimates indicate that energy savings of the order of 50% are achievable in food chains by appropriate technology changes in food production, processing, packaging, transportation, and consumption. Ventilation and infiltration account for a significant percentage of the energy use in food retail (supermarkets) and catering facilities such as restaurants and drink outlets. In addition, environmental conditions to maintain indoor air quality and comfort for the users with minimum energy use for such buildings are of primary importance for the business owners and designers. In particular, supermarkets and restaurants present design and operational challenges because the heating ventilation and air-conditioning system has some unique and diverse conditions that it must handle. This paper presents current information on energy use in food retail and catering facilities and continues by focusing on the role of ventilation strategies in food retail supermarkets. It presents the results of current studies in the UK where operational low carbon supermarkets are predicted to save 66% of CO2 emissions compared to a base case store. It shows that low energy ventilation strategies ranging from improved envelope air-tightness, natural ventilation components, reduction of specific fan power, ventilative cooling, novel refrigeration systems using CO2 combined with ventilation heat recovery and storage with phase change materials can lead to significant savings with attractive investment return

The vulnerability of refrigerated food to unstable power supplies

This paper describes a simplified model for estimating the vulnerability to spoilage of a number of refrigerated foods in households, resulting from interruptions to the electricity power grid. The tool is demonstrated on a sample of three foods (milk, chicken and fish) in India, which historically has suffered significant interruptions. The effect of interruptions is quantified in terms of tonnage and monetary value of potential losses, in a number of simple scenarios. These losses are estimated for rural and urban areas of each Indian state. Our model indicates that extensions to the duration of power supply interruptions increases potential losses in domestic refrigerators, and that these losses are considerable when compared to losses expected in previous stages of the food supply chain. The current model’s estimation of weight of food lost may be converted to a nutritional value, which opens an opportunity for new multidisciplinary areas of research

Potential for Energy Production from Farm Wastes Using Anaerobic Digestion in the UK: An Economic Comparison of Different Size Plants

© 2017 by the authors. Anaerobic digestion (AD) plants enable renewable fuel, heat, and electricity production, with their efficiency and capital cost strongly dependent on their installed capacity. In this work, the technical and economic feasibility of different scale AD combined heat and power (CHP) plants was analyzed. Process configurations involving the use of waste produced in different farms as feedstock for a centralized AD plant were assessed too. The results show that the levelized cost of electricity are lower for large-scale plants due to the use of more efficient conversion devices and their lower capital cost per unit of electricity produced. The levelized cost of electricity was estimated to be 4.3 p/kWhe for AD plants processing the waste of 125 dairy cow sized herds compared to 1.9 p/kWhe for AD plants processing waste of 1000 dairy cow sized herds. The techno-economic feasibility of the installation of CO2 capture units in centralized AD-CHP plants was also undertaken. The conducted research demonstrated that negative CO2 emission AD power generation plants could be economically viable with currently paid feed-in tariffs in the UK.The authors would like to acknowledge the funding received from the Research Councils UK (RCUK) and particularly the Engineering and Physical Sciences Research Council (EPSRC) under Grant Number: EP/K011820/1 (Centre for Sustainable Energy Use in Food Chains-CSEF) and EP/M007359/1 (Recovery and re-use of energy, water and nutrients from waste in the food chain-Redivivus)

The impact of renewable energy policies on the adoption of anaerobic digesters with farm-fed wastes in Great Britain

This paper explores the effects of the feed-in tariff (FiT) and renewable heat incentive (RHI) schemes on the adoption of anaerobic digesters (AD), and the potential energy generation from farm-fed wastes in Great Britain. This paper adopts a linear programming model, developed in the International Energy Agency (IEA) TIMES platform, aiming to quantify the degree of adoption of AD and the type of energy generation technologies that can be driven by digester biogas to reduce farm energy costs. The results show that the adoption of AD is cost-beneficial for all farms, but different rates of the FiT and RHI schemes will influence the competitiveness between the implementation of combined heat and power (CHP) systems and the utilisation of biogas to only generate heat. The choice of technology is further dependent on the electricity/heat use ratio of the farms and the energy content of the feedstock. The results show that pig farms will more readily adopt CHP, because of its relatively higher electricity-to-heat use ratio, compared to other types of farms, which will favour biogas boilers.This study was made possible from the funding received from RCUK for the establishment of the National Centre for Sustainable Energy Use in Food Chains (Grant No. EP/K011820/1), as well as contributions made by industry partners and other stakeholders in the Centre

The impact of the UK's emissions reduction initiative on the national food industry

© 2017 The Authors. Published by Elsevier Ltd. This study aims at determining the technology combination that provides the lowest emissions and energy cost for the food-industrial sector. Using a linear optimization objective function in determining the least-cost pathway, data from various sources were compiled to perform simulations on two scenarios; a business as usual (BAU) case and an 80% greenhouse gas (GHG) emissions reduction. Even in the base case, the emission level reaches 21% of 1990 levels; a reduction of 39% over the simulation period. This indicates that even without the imposition of GHG constraints on the food sector, it is economically more beneficial for the industry to migrate from fossil fuels. This migration takes place by replacing energy from LPG, LFO, Kerosene, HFO, Coal and Natural gas with biomass, biogas and CHP electricity. Economic benefits arise from the fact that biogas and biomass are produced from wastes which are generated onsite within food factories, hence the avoidance of purchasing energy feedstock from the market. The change in energy consumption between the two scenarios is similar due to the prevalence of least-cost solutions and similar energy and food demand requirements. However, the reduction in emissions are greater in the 80%-GHG case than the BAU case; 52% compared to 39% for the BAU case, for 2050 relative to 2010. This is largely owing to decarbonization of grid electricity. This study finds that the food-industrial sector has the potential to exceed this 80% reduction target to a value of 92%, due to the availability of onsite feedstocks to generate biogas. In this simulation, of all waste produced, 92% of waste feedstock is consumed in AD and CHPs, whilst the remaining 8% is dried and processed to be burned in biomass boilers

Experimental and CFD investigation of overall heat transfer coefficient of finned tube CO <inf>2</inf> gas coolers

This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) The overall heat transfer coefficient of two CO2 gas coolers was investigated through experiment and Computational Fluid Dynamics (CFD). The CFD modelling provided prediction accuracy for the overall heat transfer coefficient with a maximum error of 9% compared to the CFD predictions. Comparing the two gas cooler designs, and from the experimental and modelling results it has been shown that the performance of the gas cooler can be improved by up to 20% through optimization of the circuit design of the gas cooler. A horizontal slit between the 1 st and 2 nd row of tubes of the gas cooler can increase the overall heat transfer coefficient by 8% compared with the a fin without the slit.DRPM RISTEK DIKTI and RCU

Thermal simulation of a supermarket cold zone with integrated assessment of human thermal comfort

This work seeks to analyze the thermal comfort of the occupants in a large building of Commerce and Services, integrating measures of assessment and energy efficiency promotion. The building is still in the construction phase and at its conclusion, will correspond to a supermarket located in the Central region of Portugal. For the evaluation of thermal comfort, Fanger’s methodology was used, where the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) were calculated based on a detailed analysis of the environmental variables. These are essential to obtain, namely, mean air velocity, mean radiant temperature, mean air temperature and relative humidity. The other crucial variables are the metabolic rate and the thermal clothing resistance. The simulations necessary for the thermal comfort assessment were performed in ANSYS Fluent, in order to minimize the energy consumption in the cold thermal zone of the building, the sales area with frozen and chilled food, by means of reducing the inflow of air, without compromising thermal Comfort. The final results showed that the reduction of the amount of air to be inflated did not compromise the thermal comfort of the occupants. The Computational Fluid Dynamics (CFD) methodology allowed the creation of comfort maps, albeit for a single zone due to computational limitations. According to the results, the most comfortable zone was located right below the air insufflation with the summer being a more comfortable season. In winter, the main problem detected was the cold located near the floor.The authors would like to express their gratitude for the support given by FCT within the R&D Units Project Scope UIDB/00319/2020 (ALGORITMI) and R&D Units Project Scope UIDP/04077/2020 (MEtRICs)