Abstract: In the present paper, the finite element method is used to perform an exhaustive analysis of the thermal behavior of encapsulated phase change materials (EPCMs), which includes an assessment of several materials in order to identify the best combination of PCM and shell material in terms of thermal energy storage, heat transfer rate, cost of materials, limit of pressure that they can support and other criteria. It is possible to enhance the heat transfer rate without a considerable decrease of the thermal energy storage density, by increasing the thickness of the shell. In the first examination of thermomechanical coupling effects, the technical feasibility can be determined if the EPCM dimensions are designed considering the thermal expansion and the tensile strength limit of the materials. Moreover, when a proper EPCM shell material and PCM composition is used, and compared with the current storage methods of concentrated solar power (CSP) plants, the use of EPCM allows one to enhance significantly the thermal storage, reaching more than 1.25 GJ/m(3) of energy density.

Abstract: In order to improve the thermal efficiency of building thermal energy storage (TES) systems, the feasibility of using encapsulated phase change materials (EPCMs) as heat storage media is analysed in this work. Specifically, the finite element method is used to perform thermal behaviour analyses of several EPCMs. These analyses include technical and economic assessments in order to identify the best combination of PCM and shell material, using as main parameters: thermal energy storage, heat transfer rate, materials cost, among others. The results show that EPCMs composed by Na2SO4 center dot 6H(2)O as PCM and covered by stainless steel highlight as TES materials.

Abstract: Worldwide, environmental regulations such as Renewable Portfolio Standards (RPSs) are being broadly adopted to promote renewable energy investments. With corresponding increases in renewable energy deployments, there is growing interest in grid-scale energy storage systems (ESS) to provide the flexibility needed to efficiently deliver renewable power to consumers. Our contribution in this paper is to introduce a unified generation, transmission, and bulk ESS expansion planning model subject to an RPS constraint, formulated as a two-stage stochastic mixed-integer linear program (MILP) optimization model, which we then use to study the impact of co-optimization and evaluate the economic interaction between investments in these three asset classes in achieving high renewable penetrations. We present numerical case studies using the 24-bus IEEE RTS-96 test system considering wind and solar as available renewable energy resources, and demonstrate that up to $180 million/yr in total cost savings can result from the co-optimization of all three assets, relative to a situation in which no ESS investment options are available. Surprisingly, we find that co-optimized bulk ESS investments provide significant economic value through investment deferrals in transmission and generation capacity, but very little savings in operational cost. Finally, we observe that planning transmission and generation infrastructure first and later optimizing ESS investments as is common in industry captures at most 1.7% ($3 million/yr) of the savings that result from co-optimizing all assets simultaneously. (C) 2016 Elsevier Ltd. All rights reserved.

Abstract: Climate change has led to intensification and poleward migration of the Southeastern Pacific Anticyclone, forcing diverging regions of increasing, equatorward and decreasing, poleward coastal phytoplankton productivity along the Humboldt Upwelling Ecosystem, and a transition zone around 31 degrees S. Using a 20-year dataset of barnacle larval recruitment and adult abundances, we show that striking increases in larval arrival have occurred since 1999 in the region of higher productivity, while slower but significantly negative trends dominate poleward of 30 degrees S, where years of recruitment failure are now common. Rapid increases in benthic adults result from fast recruitment-stock feedbacks following increased recruitment. Slower population declines in the decreased productivity region may result from aging but still reproducing adults that provide temporary insurance against population collapses. Thus, in this region of the ocean where surface waters have been cooling down, climate change is transforming coastal pelagic and benthic ecosystems through altering primary productivity, which seems to propagate up the food web at rates modulated by stock-recruitment feedbacks and storage effects. Slower effects of downward productivity warn us that poleward stocks may be closer to collapse than current abundances may suggest.

Abstract: The number of residential consumers with solar PV and batteries, aka prosumers, has been increasing in recent years. Incentives now exist for prosumers to operate their batteries in more profitable ways than self-consumption mode. However, this can increase prosumer exports or imports, resulting in power flows that can lead to voltage and thermal limit violations in distribution networks. This work proposes a framework for Distribution Network Operators (DNOs) to ensure the integrity of MV-LV networks by using dynamic operating limits for prosumers. Periodically, individual prosumers send their intended operation (net exports/imports) as determined by their local control to the DNO who then assesses network integrity using smart meter data and a power flow engine. If a potential violation is detected, their maximum operating limits are determined based on a three-phase optimal power flow that incorporates network constraints and fairness aspects. A real Australian MV feeder with realistically modelled LV networks and 4,500+ households is studied, where prosumers' local controls operate based on energy prices. Time-series results demonstrate that the proposed framework can help DNOs ensure network integrity and fairness across prosumers. Furthermore, it unlocks larger profitability for prosumers compared with the use the 5kW fixed export limit adopted in Australia.

Abstract: Phase change materials (PCMs) designate materials able to store latent heat. PCMs change state from solid to liquid over a defined temperature range. This process is reversible and can be used for thermo-technical purposes. The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management. The experiment is conducted in two test rooms in Antofagasta (Chile) during summer, fall, and winter. The PCM is integrated into the rooftop of the first test room, while the roof panel of the second room is a sealed air cavity. The work introduces a numerical model, which is built using the finite difference method and used to simulate the rooms' thermal behavior. Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates. Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1 degrees C +/- 10.6 degrees C, while the one of the air-panel room varies 28.3 degrees C +/- 18.5 degrees C. Under the experiment's conditions, the PCM room's indoor temperature observes smoother diurnal fluctuations, with lower maximum and higher minimum indoor temperatures than that of the air-panel room. Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter, as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures. This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs, and improve indoor thermal comfort in different climates of Chile.

Abstract: Thermal energy storage (TES) transfers heat to storage media during the charging period, and releases it at a later stage during the discharging step. It can be usefully applied in solar plants, or in industrial processes, such as metallurgical transformations. Sensible, latent and thermo-chemical media store heat in materials which change temperature, phase or chemical composition, respectively. Sensible heat storage is well-documented. Latent heat storage, using phase change materials (PCMs), mainly using liquid solid transition to store latent heat, allows a more compact, efficient and therefore economical system to operate. Thermo-chemical heat storage (TCS) is still at an early stage of laboratory and pilot research despite its attractive application for long term energy storage. The present review will assess previous research, while also adding novel treatments of the subject. TES systems are of growing importance within the energy awareness: TES can reduce the LCOE (levelized cost of electricity) of renewable energy processes, with the temperature of the storage medium being the most important parameter. Sensible heat storage is well-documented in literature and applied at large scale, hence limited in the content of the present review paper. Latent heat storage using PCMs is dealt with, specifically towards high temperature applications, where inorganic substances offer a high potential. Finally, the use of energy storage through reversible chemical reactions (thermo-chemical Storage, TCS) is assessed. Since PCM and TCS storage media need to be contained in a capsule (sphere, tube, sandwich plates) of appropriate materials, potential containment materials are examined. A heat transfer fluid (HTF) is required to convey the heat from capture, to storage and ultimate re-use. Particle suspensions offer a valid alternative to common HTF, and a preliminary assessment confirms the advantages of the upflow bubbling fluidized bed and demonstrates that particulate suspensions enable major savings in investment and operating costs. Novel treatments of the TES subject in the review involve the required encapsulation of the latent and chemical storage media, the novel development of powder circulation loops as heat transfer media, the conductivity enhancement of PCMs, the use of lithium salts, among others. (C) 2015 Elsevier Ltd. All rights reserved.