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AbstractAlthough facility scale thermal energy storage of sensible heat in the range of 200-550°C has achieved a high maturity, state-of- the-art approaches are still not very cost effective. An innovative storage concept is thus proposed that avoids the two major cost- driving factors of the concrete storage and 2-tank molten salt systems. First, the storage volume is comprised of low-cost sensible storage material such as concrete, natural stone or clinker bricks. These materials are several times cheaper than eutectic salt mixtures used in the 2-tank-storage system. Secondly, the system uses an intermediate air cycle, allowing for direct contact with the storage material. The necessary heat exchanger for transferring the heat from the primary oil loop to the intermediate air cycle consists of significantly less steel compared to the tube register inside the concrete storage. Dynamic models of the storage system have been implemented in a Matlab/Simulink environment to analyze its performance theoretically. The investigations show, that the overall performance and profitability of the storage system are mainly linked to the thermal efficiency and pressure drop of the heat exchanger, as well as the operation strategy. To demonstrate the feasibility of the storage concept and to investigate its performance characteristic under realistic conditions, a pilot scale test facility is set up.

This paper proposes a building energy management framework, described by mixed logical dynamical systems due to operating constraints and logic rules, together with an aquifer thermal energy storage (ATES) model. We develop a deterministic model predictive control strategy to meet building thermal energy demand. At each sampling a mixed integer quadratic optimization problem is formulated. We then provide a simulation study using an agent-based model and a geohydrological simulation environment (MODFLOW) to illustrate the performance of the framework.

AbstractSolid ceramic particles have proven to be an effective heat transfer and thermal storage media for central receiver power production for a heat input temperature up to 1000°C. In the directly illuminated solid particle receiver, a cascade of ∼0.1-1mm diameter particles is directly heated within a receiver cavity by concentrated solar energy. The efficiency of this approach, with respect to the energy balance on the receiver itself, is dependent on the physical properties of the particles. In this work, the radiative properties, solar weighted absorptance and thermal emittance, have been measured for several commercially available particle candidates both in the as-received state and after thermal exposure to simulate extended operation at elevated temperature in air between 700∘C-1000∘C. Heating the particles is shown to significantly reduce the solar weighted absorptance of as-received particles within 24hours of exposure to air at 1000°C, while heating at 700°C in air has relatively little effect. In the as-received state, solar weighted absorptance can be as high as 93%, dropping to 84% after 192hours at 1000∘C. Particle stability is better at 700∘C, and the solar absorptance remains above 92% after 192hours of exposure. Analysis using x-ray diffraction (XRD) shows evidence of multiple chemical transformations in the sintered bauxite particle materials, which contain oxides of aluminum, silicon, titanium, and iron, following heating in air. However, the XRD spectra show only small differences between as-received and heat treated particles leaving open the possibility that the observed change in radiative properties results from a change in oxidation state without a concomitant phase change. Regardless of the specific degradation mechanism, t he solar weighted absorptance of the particles can be increased beyond the as-received condition by chemically reducing the particles in forming gas (5%H2 in N2 or Ar) above 700°C, providing a possible means of periodically rejuvenating degraded particles in situ.

Sugar alcohols are potential phase change materials candidates as they present high phase change enthalpy values, are non-toxic and low cost products. Three promising sugar-alcohols were selected: D-mannitol, myo-inositol and dulcitol under high melting enthalpy and temperature criterion. Thermal cycling tests were performed to study its cycling stability which can be determining when selecting the suitable phase change material. D-mannitol and dulcitol present poor thermal stability. Myo-inositol shows almost no decrease in thermal properties after 50 cycles for the heating process, however in the solidification part a decrease of 20 % of enthalpy and 11 % of temperature values is observed. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement 296006.

AbstractGEOTABS combines a GEO-thermal heat pump with a Thermally Activated Building System (TABS). It is one of the most interesting technical solutions for energy efficient and healthy building. The study's objective is to research the characteristics of an optimized GEOTABS office building design. The two most important calculation methods used are the application of dynamic building simulations in TRNSYS and daylight simulations in Dialux. A trade-off of the evaluation variables ‘adaptive thermal comfort’, ‘energy consumption’ and ‘thermal balance of the ground’ has to be made in order to define the optimal solution and desired equilibrium for each specific demand.

AbstractA family of composite cool thermal insulation materials has been developed as part of the DICOM research project, in order to provide building materials optimized for the retrospective insulation of existing buildings, which contribute in particular to the reduction of cooling loads in summer. An integrated evaluation of the materials was carried out in 2013-2014, by means of in vitro and in situ measurements, in order to determine and evaluate the materials’ performance and the thermal comfort conditions before and after the retrofitting. Finally, a Life Cycle Analysis was carried for the materials, in order to evaluate their environmental impact.

This paper discusses the specific design strategy of a novel compact unglazed Solar Thermal Facade (STF) for building performance research in architectural practice. It identifies the basic role of such STF in the building performance simulation and analysis. A dedicated design strategy based on the BIM (building information modelling) concept for application of the proposed STF is then developed in details. This research work clarifies the necessary steps in ensuring that the environmental/economic factors and energy-efficiency strategies of the STF are integrated with the building design and analysis process at the early stage.