Fifth generation district energy systems for low carbon cities

The focus and challenge for energy engineering in the context of rapid climate change is summarised by the Europe 20-20-20 targets, committing to a reduction in energy consumption of 20%. The most logical approach to achieve these goals is to target the most energy intensive sectors, namely residential and industrial. In the residential sector, centralised district energy networks are favoured as the best means of heat distribution. In the industrial sector, process integration must be performed on site, to ensure optimal resource utilisation and recovery is achieved. Extending these concepts, heat and mass integration must also be performed between different industries, and between industry and other sectors, such as residential.

In this context, this thesis addresses a series of open questions and offers methods and solutions for improvement. Chapter 1 addresses the lack of demand data in the residential sector. In view of this, it presents a geographically parameterized residential sector profile based on heating signature models for heating and cooling demands, on real consumption profiles for domestic hot water and on Swiss society of engineers and architects norms for electricity and refrigeration. Additional demands such as mobility and waste treatment are also provided.

The following chapter makes use of the sector profile introduced in chapter one to integrate the latest refrigerant-based DEN in four climate zones in Europe. Additional to the state of the art CO2 network, this chapter examines many possibilities of natural resource valorization, such as fresh water thermal sources (e.g. lakes), geothermal sources, municipal waste and solar energy. The contributions of each additional urban resource is highlighted and the variations across the climate zones in Europe are underlined.

Chapter 3 takes the parameterized sector profile one step further, extending the boundaries to include consumption of major products and their associated production requirements. The urban profile is thus extended to include industrial production from 10 different industries, namely oil refining, cement, brewing, aluminum, steel, waste incineration, sugar, pulp and paper, plastics, and dairy production. The temperature-enthalpy profiles of the different industries were taken from previously-developed industrial blueprints, while the production data was considered according to European reference documents. The updated parameterized sector profile is utilised in this chapter to study industrial waste heat recovery potential for three typical European city scales (those of Zurich, Munich and London) and a real city (Rotterdam,NL) with its 4 main oil refineries and cement plants and the city brewery.

Chapter 4 bridges the gap between building- and urban-scale analysis, therefore adding a more precise spatial scale to the optimisation problems, and proposes a method to integrate renewable energy and low-carbon resources in cities.

This thesis contributes to the field of future urban energy system planning by developing models and methods for generating optimal solutions to efficient urban energy provision. Results from each chapter show large improvement potentials in energy requirements and associated environmental impacts which could lead to zero- or negative-emission, autonomous cities.