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This paper approaches the energy transition towards decarbonization and lower primary energy use in the steel and glass industries through the exploitation of radiant waste heat. In contrast with exhaust gases heat recovery, radiant waste heat has typically not been used. This energy waste is found in energy intensive processes in which high temperatures are reached. For instance, in the steel making process, the cast steel is red hot and emits a considerable amount of radiant energy. In this paper the conceptual design of a radiant heat capturing device is presented. This device enables the recovery of currently unused energy while solving the radiative emission-related problems. The achieved design gets to an optimized solution regarding view factors and optical properties of the involved surfaces. In this research work, those factors are optimized to maximize the amount of heat recovered by the presented device. Simulation tools are used to test different designs and define the most appropriate solution for a given case.

Two different dynamic models of a flat-plate solar collector have been developed in the Modelica language under Dymola ® software. These models have been developed within the Ambassador Project (Onillon, 2014). In this project, models of district heating components are conducted for control purposes, including a solar plant model. The present article describes in detail each of these models along with the development process (e.g., assumptions taken into account). The model validation process and results are also presented, as well as the corresponding discussion and conclusions. The model's validation has been conducted by comparing the model's simulation results with the experimental results obtained in the IK4-TEKNIKER Solar Thermal Test Rig.

In a district cooling system different types of cooling generation can be combined (e.g., vapour compression chillers, absorption chillers, and free cooling). Controlling such complex systems in an efficient way is challenging: the cooling demand is much more difficult to predict than the heat demand and, as for absorption chillers, heat sources such as the solar energy and the waste heat are not predetermined by the designers. The EU project INDIGO deals with the improvement of District Cooling (DC) systems. Its main goal is the development of a more efficient, intelligent, and cheaper generation of DC systems (Loureiro, 2018;Costa, 2017). The results of INDIGO will include: -predictive controllers; -system management algorithms; -an open-source planning tool. To validate the results, the consortium is analysing some case studies. The proposed solutions for DC systems will be installed in the Basurto Hospital campus in Bilbao. Different models regarding the buildings and all the relevant components of the DC system are being developed: 1. generation systems; 2. distribution and storage systems; 3. HVAC systems; 4. thermal behaviour of the buildings, considering also internal loads and building use. The first three parts are being simulated by means of Modelica (Modelica, 2016), an open-source objectoriented modeling language that provides dynamic simulation models for building energy and control systems. The fourth part is being modelled with EnergyPlus (EnergyPlus, 2016). They are going to be integrated through the Functional Mock-up Interface (FMI) for co-simulation . The models of certain building envelope elements are validated using experimental measurements (heat flow rates, temperatures, entering solar radiation). Component models for the air handlers and for the fancoils found in the studied buildings are developed in Modelica. Different kinds of chillers are modelled too. Particular attention is paid to the distribution system, where thermal and hydraulic effects are coupled and thus must be considered jointly.All the developed models will be validated, both independently and considering the integration, using data acquired at the test-site. The validated models will be considered as reference for the development of the innovative controllers, of the management strategy, and of the planning tool. The new models developed in Modelica will be part of a District cooling open-source library (DCOL).

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