Adaptive Control for Flow and Volume Regulation in Multi-Producer District Heating Systems

Flow and storage volume regulation is essential for the adequate transport and management of energy resources in district heating systems. In this paper, we propose a novel and suitably tailored -- decentralized -- adaptive control scheme addressing this problem whilst offering closed-loop stability guarantees. We focus on a system configuration comprising multiple heat producers, consumers and storage tanks exchanging energy through a common distribution network, which are features of modern and prospective district heating installations. The effectiveness of the proposed controller is illustrated via numerical simulations

Soil as an Extended Composite Phenotype of the Microbial Metagenome

We use a unique set of terrestrial experiments to demonstrate how soil management practises result in emergence of distinct associations between physical structure and biological functions. These associations have a significant effect on the flux, resilience and efficiency of nutrient delivery to plants (including water). Physical structure determining the air-water balance in soil as well as transport rates is influenced by nutrient and physical interventions. Contrasting emergent soil structures exert selective pressures upon the microbiome metagenome. These selective pressures are associated with the quality of organic carbon inputs, the prevalence of anaerobic microsites and delivery of nutrients to microorganisms attached to soil surfaces. This variety results in distinctive gene assemblages characterising each state. The nature of the interactions provide evidence that soil behaves as an extended composite phenotype of the resident microbiome, responsive to the input and turnover of plant-derived organic carbon. We provide new evidence supporting the theory that soil-microbe systems are self-organising states with organic carbon acting as a critical determining parameter. This perspective leads us to propose carbon flux, rather than soil organic carbon content as the critical factor in soil systems, and we present evidence to support this view

Modeling and Passivity Properties of District Heating Systems

We propose a comprehensive nonlinear ODE-based thermo-hydraulic model of a district heating system featuring several heat producers, consumers and storage devices which are interconnected through a distribution network of meshed topology whose temperature dynamics are explicitly considered. Moreover, we analyze the conditions under which the hydraulic and thermal subsystems of the model exhibit shifted passivity properties. For the hydraulic subsystem, our claims on passivity draw on the monotonicity of the vector field associated to the DH system's flow dynamics, which mainly codifies viscous friction effects on the system's pressures. For the temperature dynamics, we propose a storage function based on the {\em ectropy function} of a thermodynamic system, recently used in the passivity analysis of heat exchanger networks

Control of flow networks with constraints and optimality conditions

Meer dan 40% van de totale energieconsumptie wordt gebruikt voor gebouwverwarming terwijl het grootste gedeelte wordt gegenereerd door fossiele brandstoffen. Gelukkig is er een verschuiving naar meer hernieuwbare bronnen zoals geothermie, restwarmte en warmtepompen. Echter, de productie van deze bronnen kan fluctueren en bevind zich vaak niet op dezelfde locatie als de vraag. Om deze redenen kan een warmtenetwerk met opslagmogelijkheden gebruikt worden voor het transport en garantie van aflevering. Een nadeel is dat een deel van de warmte verloren gaat in de pijpen. Deze verliezen kunnen kleiner gemaakt worden door de pijpen te verkleinen maar heeft als gevolg dat de wrijving in de pijpen toeneemt. Om dit op te lossen kunnen meerdere pompen geïnstalleerd worden.Door de extra pompen en de toevoeging van meerder producenten die niet noodzakelijk worden beheerd door één partij, volgt het dat de volgende generatie van warmtenetten nieuwe regeltechnische strategieën nodig hebben. In dit proefschrift ontwerpen en analyseren we zulke strategieën om de productie optimaal te coördineren en de opslagniveaus te reguleren zodanig dat de warmtelevering gegarandeerd kan worden. Om schaalbaarheid te garanderen, een ‘single point of failure’ te voorkomen en informatie-uitwisseling te minimaliseren stellen we een gedistribueerd mechanisme voor dat een peer-to-peer communicatienetwerk gebruikt. We ontwerpen ook regelaars die de druk in de netwerken met meerdere pompen reguleert. Omdat deze pompen vaak alleen een positieve druk kunnen leveren zorgen we er voor dat aan deze voorwaarde wordt voldaan.More than 40% of the total consumed energy is used for space heating and most of it is generated form fossil fuels. Fortunately there is a shift towards more sustainable sources such as geothermal energy, waste heat and heat pumps. However the supply of these heat sources can be intermittent and is often not co-located with the demand. For this reason a district heating network with storage capabilities can be used for the transportation and security of delivery. A downside is that some heat dispersion occurs in the transportation pipes. This dispersion can be lowered when smaller pipes are used, but this increases the friction in the pipes. To overcome this, the number of pumps in these networks can be increased.Due to the extra pumps and the introduction of multiple producers that are not nessecarily owned by the same entity it follows that the next generation of heat networks require new control strategies in which communication is crucial. In this thesis we design and analyze such control strategies to optimally coordinate the generation and regulate the storage levels such that the heat supply can be guaranteed. In order to guarantee scalability, avoid a single point of failure and minimize the information that companies need to share, we suggest a distributed mechanism that uses a peer-to-peer communication network. We also design controllers that can regulate the pressure in a network with multiple pumps. As these pumps can often only generate positive pressures we guarantee that this constraint is satisfied