Innovative solar energy technologies and control algorithms for enhancing demand-side management in buildings

The present thesis investigates innovative energy technologies and control algorithms for enhancing demand-side management in buildings. The work focuses on an innovative low-temperature solar thermal system for supplying space heating demand of buildings. This technology is used as a case study to explore possible solutions to fulfil the mismatch between energy production and its exploitation in building. This shortcoming represents the primary issue of renewable energy sources. Technologies enhancing the energy storage capacity and active demand-side management or demand-response strategies must be implemented in buildings. For these purposes, it is possible to employ hardware or software solutions. The hardware solutions for thermal demand response of buildings are those technologies that allow the energy loads to be permanently shifted or mitigated. The software solutions for demand response are those that integrate an intelligent supervisory layer in the building automation (or management) systems. The present thesis approaches the problem from both the hardware technologies side and the software solutions side. This approach enables the mutual relationships and interactions between the strategies to be appropriately measured. The thesis can be roughly divided in two parts. The first part of the thesis focuses on an innovative solar thermal system exploiting a novel heat transfer fluid and storage media based on micro-encapsulated Phase Change Material slurry. This material leads the system to enhance latent heat exchange processes and increasing the overall performance. The features of Phase Change Material slurry are investigated experimentally and theoretically. A full-scale prototype of this innovative solar system enhancing latent heat exchange is conceived, designed and realised. An experimental campaign on the prototype is used to calibrate and validate a numerical model of the solar thermal system. This model is developed in this thesis to define the thermo-energetic behaviour of the technology. It consists of two mathematical sub-models able to describe the power/energy balances of the flat-plate solar thermal collector and the thermal energy storage unit respectively. In closed-loop configuration, all the Key Performance Indicators used to assess the reliability of the model indicate an excellent comparison between the system monitored outputs and simulation results. Simulation are performed both varying parametrically the boundary condition and investigating the long-term system performance in different climatic locations. Compared to a traditional water-based system used as a reference baseline, the simulation results show that the innovative system could improve the production of useful heat up to 7 % throughout the year and 19 % during the heating season. Once the hardware technology has been defined, the implementation of an innovative control method is necessary to enhance the operational efficiency of the system. This is the primary focus of the second part of the thesis. A specific solution is considered particularly promising for this purpose: the adoption of Model Predictive Control (MPC) formulations for improving the system thermal and energy management. Firstly, this thesis provides a robust and complete framework of the steps required to define an MPC problem for building processes regulation correctly. This goal is reached employing an extended review of the scientific literature and practical application concerning MPC application for building management. Secondly, an MPC algorithm is formulated to regulate the full-scale solar thermal prototype. A testbed virtual environment is developed to perform closed-loop simulations. The existing rule-based control logic is employed as the reference baseline. Compared to the baseline, the MPC algorithm produces energy savings up to 19.2 % with lower unmet energy demand

Design of a low-temperature solar heating system based on a slurry Phase Change Material (PCS)

Flat-plate solar thermal collectors are the most common devices used for the conversion of solar energy into heat. Water-based fluids are frequently adopted as heat carriers for this technology, although their efficiency is limited by certain thermodynamic and heat storage constraints. Latent heat, which can be obtained from microencapsulated Phase Change Slurry (mPCS) – that is a mixtures of microencapsulated Phase Change Materials (mPCM), water and surfactants – is an innovative approach that can be used to overcome some of the aforementioned limitations. The viscosity of these fluids is similar to that of water, and, as a result, they can be pumped easily. Some of the thermo-physical and rheological properties and the material behaviour of flat-plate solar thermal collectors with an mPCS as the heat carrier fluid are analysed in the present work. Solar thermal systems filled with an mPCS are proposed and a prototypal system is presented. The possible advantages and drawbacks of this technology are also discussed

A Supervisory Control Strategy for Improving Energy Efficiency of Artificial Lighting Systems in Greenhouses

Artificial lighting systems are used in commercial greenhouses to ensure year-round yields. Current Light Emitting Diode (LED) technologies improved the system efficiency. Nevertheless, having artificial lighting systems extended for hectares with power densities over 50W/m2 causes energy and power demand of greenhouses to be really significant. The present paper introduces an innovative supervisory and predictive control strategy to optimize the energy performance of the artificial lights of greenhouses. The controller has been implemented in a multi-span plastic greenhouse located in North Italy. The proposed control strategy has been tested on a greenhouse of 1 hectare with a lighting system with a nominal power density of 50 Wm−2 requiring an overall power supply of 1 MW for a period of 80 days. The results have been compared with the data coming from another greenhouse of 1 hectare in the same conditions implementing a state-of-the-art strategy for artificial lighting control. Results outlines that potential 19.4% cost savings are achievable. Moreover, the algorithm can be used to transform the greenhouse in a viable source of energy flexibility for grid reliability

Natural ventilation as sustainable response to Covid-19: Designing an airborne disease treatment centre in Burkina Faso

Climate, pandemic and energy have often shaped and characterised the transformations of our built environment. Today, under the current pandemic conditions, we are witnessing the ability (or not) of the built environment in responding to such emergency through changes and adaptation. Among many approaches to such changes and emergencies, we are presenting the idea of relying on passive design as a medium to manage and prevent pandemic events. In particular, this paper will focus on the tight relation between natural ventilation and architectural design as a sustainable response to Covid-19. To do so, the work focus on the design of a Severe Acute Respiratory Infection (SARI) Treatment Centre in Dori, Burkina Faso, in collaboration with an International humanitarian Institution. This experience shows the ability of passive design and natural ventilation to deliver a sustainable and resilient health facility able to engage the local community and optimise resources in a context of scarcity. The importance of this work is to inform design guidelines for further health facilities in the same climatic area, as well as to set the example of passive design support the prevention of the spread of air borne diseases

Characterization and energy performance of a slurry PCM-based solar thermal collector: a numerical analysis

Flat plate solar thermal collector is the most common technology for solar energy conversion at the building scale. This technology has been established since long time and continuous developments have been achieved as time passed by; significant improvements of flat plate solar thermal collectors are thus now limited. A novel approach to increase further the performance of this technology is based on the exploitation of the latent heat of the heat carrier fluid. In order to assess this strategy, a previously developed numerical model of flat plate solar thermal collector with slurry PCM as heat carrier is herewith used to simulate the technology. The characterization and energy performance of such a system are herewith presented, based on the outcome of the numerical analysis. The results demonstrate that the novel approach is able to improve the performance of the system under different boundary conditions and in different climates: the improvement in the instantaneous efficiency is in the range 5-10%, while during the winter season the converted heat by the slurry PCM-based system is 20-40% higher than that of a conventional water based solar collector, depending on the climates – the colder the climate, the larger the improvement

Ethical issues of monitoring sensor networks for energy efficiency in smart buildings: A case study

Abstract The development of Internet of Things (IoT) based sensors has become crucial for analyzing and optimizing the energy-performance of buildings. However, researchers and professionals should be prepared to deal with the social and thus ethical issues arising from the use of such technologies. Based on a real case-study, we present a detailed analysis of the networks of stakeholders and the consequent ethical issues related to the implementation of energy and IEQ sensors network in an Italian university campus. Alternative scenarios for eliminating or reducing the criticalities related to security and privacy issues are proposed

Experimental Measurement and Numerical Modeling of the Creaming of mPCM Slurry

The slurry of mPCM has been widely used for enhancing heat transfer and reducing building energy consumption. Because of intrinsic density differences between mPCM and water, the slurry is subject to creaming phenomena. As a consequence the viscosity of slurry increases and the thermal properties decrease. Up to now no quantitative analysis about the creaming of mPCM has been done. In the paper experimental measurement and numerical modeling of the creaming of mPCM slurry is presented. Using the optical method, the temporal-spatial distribution of volume concentration is recorded. Based on the conservation model, the process of creaming has been simulated

Thermal Energy Storage with Super Insulating Materials: A Parametrical Analysis

AbstractThe adoption of super-insulating materials could dramatically reduce the energy losses in thermal energy storage (TES). In this paper, these materials were tested and compared with the traditional materials adopted in TES. The reduction of system performance caused by thermal bridging effect was considered using FEM analysis. Afterwards, parametrical analysis of the most influencing variables that affect super insulated TES tanks was carried out, to investigate effective benefits and drawbacks due to the adoption of these materials. Possible future applications and outlooks were discussed

Data mining for energy analysis of a large data set of flats

energy; statistical analysis; sustainabilit

Potentialities of a Low Temperature Solar Heating System Based on Slurry Phase Change Materials (PCS)

AbstractFlat-plate solar thermal collectors are the most common devices to convert solar energy into heat. Water-based fluids are commonly adopted as heat carrier for this technology, although their efficiency is limited by some thermodynamic and heat storage constraints. To overcome some of these limitations, an innovative approach is the use of latent heat, which can be available by means of microencapsulated slurry PCMs (mixtures of microencapsulated Phase Change Materials, water and surfactants). The viscosity of these fluids is similar to that of water and they can be easily pumped. In the present work, some of the thermo-physical and rheological properties and material behaviour that interest flat-plate solar thermal collectors with slurry PCM as the heat carrier fluid are analysed. Concepts of solar thermal systems filled with a slurry phase change material are proposed and a prototypal system is presented. Possible advantages and drawbacks of this technology are also discussed