Paris A. Fokaides

Phase change materials (PCMs) integrated into transparent building elements: a review

Abstract Phase change materials (PCMs) represent an innovative solution that can contribute to the improvement of the energy performance of buildings. Recently a trend towards integrating PCMs into transparent envelope components is observed. This study aims to present the main solutions proposed in the literature for applications in the past few years for PCMs integrated into transparent buildings elements. The temporal development of this application as well as the fundamental principles of its operation is described in detail. The concept of the existing transparent PCM systems is presented, and the rationale of selecting appropriate materials is discussed. This is followed by the current practices in testing the thermal performance of transparent PCMs. The future trends in terms of the current barriers and the potential improvements are discussed. To this end the future technologies of transparent PCMs are also considered.

A review of olive mill solid wastes to energy utilization techniques.

In recent years, the utilization of olive industry by-products for energy purposes has gained significant research interest and many studies have been conducted focused on the exploitation of olive mill solid waste (OMSW) derived from the discontinuous or continuous processing of olive fruits. In this review study, the primary characteristics of OMSW and the techniques used to define their thermal performance are described. The theoretical background of the main waste-to-energy conversion pathways of solid olive mill wastes, as well as the basic pre-treatment techniques for upgrading solid fuels, are presented. The study aims to present the main findings and major conclusions of previously published works undertaken in the last two decades focused on the characterization of olive mill solid wastes and the utilization of different types of solid olive mill residues for energy purposes. The study also aims to highlight the research challenges in this field.

Investigation of building integrated photovoltaics potential in achieving the zero energy building target

Since the photovoltaic (PV) scientific community started exploring innovative ways of incorporating solar electricity into buildings, a whole new vernacular of solar electric architecture emerged. Currently, there is a growing consensus that building integrated photovoltaics (BIPV) systems will be the backbone of the zero energy building (ZEB) European target by 2020, through their widespread commercialization. BIPV systems often produce however less energy than conventional PV systems due to architectural constraints in the design of BIPV arrays. This paper presents a conceptual study regarding the energy yield and feasibility of BIPVs in several locations in Europe. Specific conclusions on the energy yield and economic feasibility of BIPVs with regard to the implemented PV module technology, the climatic zone, the orientation of the building and the mounting disposition are drawn. The findings of this work that were also validated using hourly time step computational analysis, reveal the necessary conditions under which BIPVs could have a major contribution to fulfilling the European 2020 targets by enabling the achievement of the ZEB goal.

A review of quantification practices for plant-derived biomass potential.

The quantification of biomass potential is a useful task that may deem necessary under various circumstances. This study aims to identify the practices that have been followed in the recent past for the quantification of the plant-derived biomass potential. The employed methodology was based on an extensive literature review of recent studies in the field of biomass quantification. The review was classified in two fields: agriculture and crop residues potential, and forest residual potential. Within this study, the best quantification practices were collected and categorized and the main principles of plant-derived biomass quantification models were identified. Databases of typical properties of various types of biomass were established and a matrix of options for calculating biomass potential, depending on incoming data was delivered.

Numerical simulation of phase change materials for building applications: a review

ABSTRACT The incorporation of phase change materials (PCMs) into building elements is an effective technique that has been gaining momentum in the construction industry for achieving reductions in the energy consumption of buildings. The operation of PCM-incorporated building elements has been widely proven experimentally; however fundamental problems are encountered when it comes to its numerical simulation, where non-linear phenomena that change in time and space also have to be considered. This paper reviews the existing literature on the numerical simulation of PCMs for building applications, and identifies the basic parameters that are required to be taken into account for conducting the numerical simulation of PCM-incorporated building systems. These parameters include the geometry and discretization of the simulated PCM-incorporated building system, the physics of heat transfer embracing thermophysical properties and heat transfer mechanisms, and boundary conditions to be considered for the numerical simulation, and the implementation of experimental validation studies. The focus of this paper is to provide evidence for the significance of considering heat convection to the calculation of the thermal performance of PCM. In view of the findings of the literature review, numerical studies for a building wall incorporating PCM are conducted. The results of the simulation studies assess the impact and emphasize the importance of accounting for natural convection within the liquid PCM in numerical simulation studies.

Multicriteria analysis for the selection of the most appropriate energy crops: the case of Cyprus

Energy crops are considered key actors in meeting the international and European carbon reduction targets, increasing the national energy security through renewable energy production, mitigating climate change impacts, and promoting sustainability. Multicriteria analysis is a suitable decision-making tool for the energy sector, where the final decisions have to consider for a range of aspects, and can be utilised as well for deciding on appropriate energy crops. In this paper, a popular multicriteria method, PROMETHEE, is employed for the identification of the most optimal energy crops for their exploitation in Cyprus. The criteria and the weights of each are defined, and accordingly five different scenarios are developed and examined. The obtained results indicated that the promotion of second-generation energy crops is more ideal in terms of the set objectives, as well as more sustainable than the exploitation of any first-generation energy crop.

Monte Carlo parametric modeling for predicting biomass calorific value

Due to the nonlinear relationship between the calorific value and the elemental concentration of biomass, methods such as linear regression, widely used in the literature to model this relationship, produce models that fail to provide well-grounded results. In this study, a novel approach, based on Monte Carlo parametric modeling, for calculating the calorific value of biomass from measurements provided by elemental analysis, is presented. Olive husk, a biomass source widely used in the Mediterranean basin, was the subject under investigation. A comprehensive analysis of the thermal properties of olive husk was conducted. The elemental analysis, as well as the calorific value, the moisture content the sampling and the preparation of the examined biomass were performed using the appropriate CEN standards and procedures. Based on the Monte Carlo parametric modeling, the parameters of an exponential model linking the elemental analysis and the calorific value of olive husk were estimated. This study is anticipated to provide further insight to the discussion on models for predicting the calorific value of biomass, by introducing a novel mathematical approach.

Integration Potentials of Insular Energy Systems to Smart Energy Regions

Abstract Smart energy regions are defined as regions that offer maximal quality of living to their inhabitants with a minimal consumption of energy by intelligently joining of infrastructure (energy, mobility, transport, communication, etc.) on different hierarchical levels (building, district, city). The development of insular energy systems into smart energy regions, due to their special character, is presented with some challenges. The focus of this article is on presenting the potential of insular energy systems transforming into smart energy regions. Insular energy systems are defined based on data retrieved from Energy Information Administration (EIA) and classified according to their size and the nature of their isolation. In terms of this study, two novel indexes are introduced: the necessity index, which quantifies the need, and the ability index, which represents the capability of an insular energy system to develop into a smart one. These indexes are defined for those insular systems that are considered potentially upgradable. The analysis revealed that the main prerequisites to achieve the development of insular energy systems into smart ones are the reduction of GHG emissions, the introduction of political obligation toward promoting environmentally friendly policies, and the increase of RES utilization for energy production.

Experimental Investigation of the Stability Mechanism and Emissions of a Lifted Swirl Nonpremixed Flame

We report on the experimental investigation of a confined lifted swirl nonpremixed flame by applying a novel Airblast nozzle (Zarzalis, N., et al., 2005, Fuel Injection Apparatus, Patent No. DE 10 2005 022 772.4, EP 06 009 563.5). 3D-laser doppler anemometry, a nonintrusive, laser-based measurement technique, is adapted for the measurement of all three mean velocity components and of the six Reynolds stress components. The determi- nation of the temperature and mixture field occurs by employing in-flame measurement techniques. Valuable information concerning the mixing procedure, the temperature distribution, the turbulence level, and the velocity field of the flame is provided. The results demonstrate that there is sufficient residence time in the precombustion area of the lifted flame in order to achieve spatial and temporal uniformity of the mixture, leading to a quasi-premixed state. It was also found that hot reaction products, carried upstream by an annular zone of reverse flow, react with fresh unburnt mixture in a re-ignition process. The determination of the flow pattern revealed the presence of an inner weak recirculation zone in the nozzle vicinity and a dominant external recirculation zone. The examination of the probability density function of the velocity measurements was also found to be a very useful tool in terms of the analysis of the turbulence structure of the flow. The bimodal distribution in the shear layer between the downstream flow and the recirculated gases yields the existence of large scale eddies. Finally, the significant reduced NO x emissions in the lean area were also shown by means of emission measurements for elevated pressure conditions.

Life Cycle Assessment of concrete manufacturing in small isolated states: the case of Cyprus

ABSTRACT Life Cycle Assessment (LCA) is an effective and valuable methodology for identifying the holistic sustainable behaviour of materials and products. It is also useful in analysing the impact a structure has over the course of its life cycle. Currently, there is no sufficient knowhow regarding the life cycle performance of building materials used in the case of small isolated states. This study focuses on the LCA of the production of concrete for the investigation of its environmental impact in isolated island states, using the case of Cyprus as an example. Four different scenarios for the production of 1 tonne of concrete are examined: (i) manufacturing of concrete by transporting raw materials from different locations around the island, (ii) manufacturing of concrete using alternative energy resources, (iii) manufacturing of concrete with reduced transportation needs, and (iv) on-site manufacturing of concrete. The results, in terms of environmental impacts of concrete produced, indicated that the use of renewable electricity instead of fossil-fuelled electricity in isolated states can drastically improve the environmental performance of the end product. Also, the minimisation of transportation distances and the use of locally available resources can also affect, to a degree, the environmental impact of concrete production. Abbreviations: AP: Acidification Potential; CRC: Completely Recyclable Concrete; GWP: Global Warming Potential; HFO: Heavy Fuel Oil; LCA: Life Cycle Assessment; LCI: Life Cycle Inventory; LCIA: Life Cycle Impact Assessment; MPA: Mineral Products Association; ODP: Ozone Depletion Potential; POCP: Photochemical Ozone Creation Potential; PV: Photovoltaics