Sustainable District Research Articles

Urban Renovation from Precarious to Sustainable Districts: Study Case of Mvog-Ada in Yaounde

This article explores the possibility of transforming precarious neighbourhoods, commonly known as slums, into good-living and environmentally- friendly places by rethinking their layout. It examines the state of the study case and highlights the relationships between the road system, parcels of land and other components of the urban fabric, with the aim of resolving the problems caused by the poor occupation of urban space and the lack of architectural knowledges and basic infrastructure necessary for people's lives in Cameroon. This research addresses the problems of anarchic urbanisation, urban densification and unhealthy living conditions, it proposes concrete solutions for decongesting the area, strategically redeveloping the space and ensuring the sustainable development of the site, while incorporating a biomimetic and circular approach. To achieve this goal, it was important to put in place a renovation strategy that is both up-to-date and adapted to the local context. With this in mind, this work presents a comprehensive and innovative master plan designed to solve the problems of development, bad urban traffic and degradation of the area through the use of an appropriate methodology of sustainable urban planning. Finally, the concept of sustainable district is presented as a pillar of the development of precarious districts and as an opportunity of growth for the development of their country.

Booster heat pump with drop-in zeotropic mixtures applied in ultra-low temperature district heating system

The pursuit of sustainable district heating solutions has driven a growing interest in ultra-low temperature district heating (ULTDH) systems, where booster heat pumps (BHPs) play a pivotal role despite challenges posed by their efficiency limitations under large temperature glide conditions. This paper investigates the potential of drop-in R-1234yf/R-32 zeotropic mixtures in BHPs compared to a baseline R-134a system, within the context of a ULTDH framework. This study focused on the viability of the mixtures of R-1234yf/R-32 with the composition ratio of 80 %/20 % and 90 %/10 %. The investigation reveals disparities in compressor efficiency and heat exchanger pressure drop at the component level. Device-level analysis unveils increased COP for R-1234yf/R-32 mixtures, alongside with maximum second-law efficiencies reaching 0.32. A remarkable enhancement in heating capacity up to 58 % was found. System-level analysis demonstrated exergetic efficiencies and identified preferable district heating temperatures. Exergetic efficiencies of 0.47, 0.55, and 0.59 were achieved for domestic hot water preparation at district heating supply temperatures of 30 °C, 35 °C, and 40 °C, with a subsequent shift in optimal district heating temperatures as central heating station efficiency decreased. Temperature profile analysis underscored challenges stemming from excessive subcooling, highlighting the need for configuration refinements.

A Showcase for Resilient and Sustainable District Heating in Denmark

This presentation gives a description of the Danish district heating company, Hvide Sande District Heating, which has become independent of fossil fuels by using wind and solar energy. This has resulted in lower consumer heating prices in a time when other fossil fueled district heating plants are raising their heating prices due to higher fossil fuel prices.Besides participating in the Day-ahead market it also participates in the balancing markets.Hvide Sande is a small fishing town. The district heating plant provides heat to 1,700 consumers. From being a natural gas fired Combined Heat and Power plant, it has in recent years become more resilient by investing in a solar collector, wind turbines, a heat pump, an electrical boiler as well as more large thermal storages, and is now independent of natural gas.The two thermal storages of 2,000 m3 and 1,200 m3, respectively, can store around 200 MWh-heat, which allows flexible market-based productions of the different production units. The heat delivered to consumers can thus be produced many hours or days before delivery.Even in the Day-ahead market, the market-based productions are a challenge to plan. Because of the large thermal storages, the manager must look more days ahead as well as consider the heat amount in the thermal storages, when deciding the hourly bids for tomorrow. Biddings are based on forecasts more days ahead of wind velocity, solar radiation, ambient temperatures, and Day-ahead prices.Besides participating in the Day-ahead market it also participates in the balancing markets. However, to take advantage across more electricity markets of this flexibility, a vast digitalization of the plant using advanced bidding methods has been required. This presentation illustrates examples of the daily earnings the plant has had participating across more electricity markets. It is also important that the manager maintains a digital twin of the plant. The digital twin of the plant will in this presentation be used for simulating the resilience of the plant against large changes in electricity prices and fuel prices.

Alternative Backfill Materials for Sustainable District Heating Systems

Abstract District heating pipes are usually installed in open trenches that are refilled with backfill material. Special requirements were set for this material in standards and codes of practice and in the most cases natural sands were used in the past. Today natural sands are a scarce resource and must be protected. Furthermore, regulations of the circular economy challenge existing construction methods. In sustainable energy systems natural sands should only be used in exceptional cases. Against this background the general planning process and the significant calculation methods for district heating pipes were analysed and other material options and the hindrances for the use of alternative backfill were identified. Necessary modifications in the planning and calculation process were elaborated. It was shown, that the transition to a more circular economy approach in district heating systems is realistic, if conventional planning methods will be adjusted.

Sustainable district optimization with coupled power and district heating networks

In a framework where the integration of renewable energy sources has a crucial role for addressing global energy challenges, optimal operations of the heating must be correctly addressed. This paper addresses the optimization of integrated electric and thermal networks in the context of smart grids with District Heating Networks (DHNs). It presents an Energy Management System (EMS) for efficient management, considering thermal models for buildings. Through a real case study at the Savona Campus, encompassing a smart polygeneration microgrid and DHN, the proposed model ensures temperature regulation while minimizing costs. Results demonstrate precise temperature control, particularly in highly responsive buildings like the Savona Campus.

Analysis of the influence of district thermal properties for enhancing energy flexibility through thermal mass activation

This study investigates the use of thermal mass within a smart sustainable district (SSD) to facilitate the renewables’ integration. The aim is to pinpoint the most suitable archetypes in a SSD and the most optimal energy flow to each of them; moreover, to establish a relation between the suitability to activate thermal mass and the properties of the archetypes, namely Heat Loss Coefficient (HLC), Structural mass (SM) and time constant (TC). First a dummy residential district is defined, then using construction and envelope properties, archetypes are defined. Based on the archetypes, the district is clustered and then it is modelled using Artificial Neural Networks (ANN). The energy optimization and renewable integration is casted as an Optimal Control Problem (OCP). Solving this OCP ensures thermal comfort within the building clusters and the renewable energy is stored optimally through the thermal mass. Finally, conclusions are drawn on which clusters of buildings offer the most opportunities to store the renewables through their thermal mass within a district and which criteria best reflect on that. The results signify that HLC and TC are more suitable criteria.

Exploring the health and energy savings dilemma in swimming facilities and the potential influence of Positive Energy Districts

Positive energy districts (PED) are neighborhoods with a net positive energy balance with the main goal to create sustainable districts that contribute to the energy transition. The three pillars energy efficiency, renewable energy, and energy flexibility forms the foundation of PEDs, and ‘Quality of life’ is one of the key principles.Indoor swimming facilities for recreation and sports, also called aquatic centers or swimming halls, are important for healthy lifestyles. They are highly energy-demanding facilities due to the large volumes and strict heating- and ventilation requirements to ensure the health of staff, visitors, and bathers. The large energy consumption indicates good potential to reduce their energy use. One possibility might be to include aquatic centers in PEDs: the district could support the facility with locally produced renewable energy. There are also studies that investigates innovative solutions regarding aquatic centers that might have potential to increase resilience and flexibility in the district.However, one important aspect in studies on energy use in aquatic centers that is often neglected is the presence of disinfection by-products (DBP), which are found in the air and water of chlorinated swimming pools. Several DBPs can lead to health issues, such as asthma, eye irritation, and even cancer.There are often conflicting goals in studies on swimming halls. The connection between DBP and energy is currently missing, and it could lead to projects compromising health over energy savings. Based on a literature review, this study highlights the research gap between DBPs and energy use in swimming facilities. A suggestion is also presented to integrate swimming halls into PEDs with the aim of increasing possibilities for a healthy lifestyle, supporting the aquatic center’s energy demand with renewable energy, and exploring new solutions for flexibility and resilience in the district.

Liquid Natural Gas Cold Energy Recovery for Integration of Sustainable District Cooling Systems: A Thermal Performance Analysis

This paper investigates the heat transfer properties of liquefied natural gas (LNG) in a corrugated plate heat exchanger and explores its application in cold energy recovery for enhanced energy efficiency. The study aims to integrate this technology into a 500 MW gas-fired power plant and a district cooling system to contribute to sustainable city development. Using computational fluid dynamics simulations and experimental validation, the heat transfer behaviour of LNG in the corrugated plate heat exchanger is examined, emphasising the significance of the gas film on the channel wall for efficient heat transfer between LNG and water/ethylene glycol. The study analyses heat exchange characteristics below and above the critical point of LNG. Below the critical point, the LNG behaves as an incompressible fluid, whereas above the critical point, the compressible supercritical state enables a substantial energy recovery and temperature rise at the outlet, highlighting the potential for cold energy recovery. The results demonstrate the effectiveness of cold energy recovery above the critical point, leading to significant energy savings and improved efficiency compared to conventional systems. Optimal operational parameters, such as the number of channels and flow rate ratios, are identified for successful cold energy recovery. This research provides valuable insights for sustainable city planning and the transition towards low-carbon energy systems, contributing to the overall goal of creating environmentally friendly and resilient urban environments.

Economic and environmental optimal design of a multi-vector energy hub feeding a Local Energy Community

One of the main ways to reach the important targets of the European Commission in the energy field set by 2030 is to implement sustainable energy systems to cover electrical and thermal energy demands, as well as transportation needs, in urban areas. In the aforesaid scenario, multi-vector energy hubs consist of installing small and medium size power plants, mainly fed by renewable sources, and charging infrastructures for electric vehicles in sustainable urban districts. The optimal design of such systems can be faced from different points of view and using different methods, one of the most adopted being the development of mathematical programming algorithms typically aimed to minimize global costs and emissions. The contribution of this paper is to propose an innovative methodology to optimally design a multi-vector energy hub able to supply electricity and thermal energy, for space heating and cooling, to a set of buildings within a sustainable district acting as a local energy community. The developed mixed integer linear programming model is characterized by very detailed models of the technologies and by a multi-objective function which is proposed to evaluate the impact of the optimal solution on global costs and emissions. The proposed mathematical model is very comprehensive as it involves a wide range of energy technologies with detailed modelling by considering the impact of external ambient conditions and energy vector temperature values on the plant conversion efficiency, thus showing high replicability potential in real contexts. In the case study, the model is applied to a university campus in the North of Italy.

Assessing Urban Sustainability and the Potential to Improve the Quality of Education and Gender Equality in Phnom Penh, Cambodia

This research assessed the urban sustainability of all 14 districts of the Cambodian capital Phnom Penh to identify weaknesses and improvement potentials to achieve the national development goals; the New Urban Agenda (NUA); and the Sustainable Development Goals (SDGs) 11 (sustainable cities and communities), 4 (quality education), and 5 (gender equality). The indicators’ selection was based on available data. The analysis of the indicators and their weights was based on the analytic hierarchy process (AHP). Indicator weights were used to improve assessment accuracy and identify each district’s unique characteristics and specific strengths and weaknesses. The normal distribution model was used to standardize the variables before comparison. Among the quality education indicators, the access to education and vocational training obtained the highest weight of 0.38, followed by education staff with 0.33 and facilities with 0.29. Among gender-equality-related indicators, the indicators related to professions obtained the highest weight with 0.34, followed by schools with 0.33 and decision-making with 0.32. The most sustainable district was Boeng Keng Kong, with a consolidated result of 22.81 for quality education and gender equality assessment based on indicator weights, followed by the districts Doun Penh with 20.51, Prampir Makara with 19.95, and Chamkarmon with 19.75. This research identified district-specific strengths and weaknesses, whereas the weak points unveil the improvement potential of specific districts.

Comparison of Space Cooling Systems from Energy and Economic Perspectives for a Future City District in Sweden

In this study, the performance of different cooling technologies from energy and economic perspectives were evaluated for six different prototype residential Nearly Zero Energy Buildings (NZEBs) within a planned future city district in central Sweden. This was carried out by assessing the primary energy number and life cycle cost analysis (LCCA) for each building model and cooling technology. Projected future climate file representing the 2050s (mid-term future) was employed. Three cooling technologies (district cooling, compression chillers coupled/uncoupled with photovoltaic (PV) systems, and absorption chillers) were evaluated. Based on the results obtained from primary energy number and LCCA, compression chillers with PV systems appeared to be favorable as this technology depicted the least value for primary energy use and LCCA. Compared to compression chillers alone, the primary energy number and the life cycle cost were reduced by 13%, on average. Moreover, the district cooling system was found to be an agreeable choice for buildings with large floor areas from an economic perspective. Apart from these, absorption chillers, utilizing environmentally sustainable district heating, displayed the highest primary energy use and life cycle cost which made them the least favorable choice. However, the reoccurring operational cost from the LCCA was about 60 and 50% of the total life cycle cost for district cooling and absorption chillers, respectively, while this value corresponds to 80% for the compression chillers, showing the high net present value for this technology but sensitive to future electricity prices.

OPERATIONALISING SUSTAINABLE DEVELOPMENT PRACTICE FOR AREA-BASED SUSTAINABILITY IMPLEMENTING UN-SDGS (2015-2030) AT THE LOCAL DISTRICT AREA

This paper discussed district sustainability as a set of system delimitations that are practically appropriate and manageable to implement the seventeen UN-SDGs to balance environmental, social, and economic development. By default, the district system is a socio-ecological system and a geographically defined area where the sustainability pillars are balanced to provide a symbiotic condition. However, the consideration and operationalisation of environmental role in the district’s socio-economic development decision-making process not explicitly emphasised. The emphasis should focus on the critical role of communication, participation, and collaboration among diverse stakeholders in implementing and operationalising the natural environmental role, the fundamental component of district sustainability, and further democratising natural resources and landscape planning to guarantee district sustainability. If replicated all the districts within state, provincial, regional, and national levels, the sustainable district could aid in the achievement of the 17 UN-SDGs.

Measurement of management and development deficit on sustainability in neighbourhood unit. Case of the new city Ali Mendejeli Constantine

Wastewater and household waste management are among the most significant issues for sustainable districts. Their management requires quantifying spatial relationships between the appreciation spaces rate and well-being. This research aims to quantify the effect of development and management deficits on the sustainability of social housing districts. The case study is the neighbourhood unit in the new Ali Mendjli Constantine, Algeria, characterized by high urban concentration. The critical points marking the latter relate to health and well-being problems. The methodology used in this research is a qualitative survey based on J.P. Thibaud’s commented course approach. It involves the surveyed population selection who create the course according to the issue asked. The results show that more than 50% of the neighbourhood’s spatial configuration directly affects the appropriation feeling, with a high dissatisfaction rate of approximately 85%. Furthermore, the interviewees declared that intermediate spaces within their neighbourhoods are spread over large areas without delimitation and specific development and management, making space assumption difficult. Thus, these spaces become sources of conflict and tension.

An Energy Management System for microgrids including costs, exergy, and stress indexes

In this paper, a multi-objective Energy Management System (EMS) for polygeneration microgrids is presented. The proposed tool has been developed within the LIVING GRID project, funded by the Italian Ministry of Research (actions related to the Italian Technology Cluster on Energy), and it is characterized by a detailed representation of generation units and flexible loads, as well as electric/thermal networks and storage systems that can be present in microgrids and sustainable districts. A new optimization model has been developed in which the objective function is related to the minimization of costs, the maximization of the overall exergy efficiency of the system, and the minimization of stress indexes. To solve efficiently the optimization problem, a novel algorithm based on an accelerated version of the Bregman Alternating Direction Method of Multipliers (with Heavy Ball dual acceleration term) has been developed and discussed. The decision model has been applied to a real case study represented by the Savona Campus of the University of Genova in Italy. A sensitivity analysis has been performed for evaluating the effect of each term of the objective function on the solution.

A method for global potential assessment of roof integrated two-stage solar concentrators (TSSCs) at district scale

This paper proposes a core method for integrating two-stage solar concentrators (TSSCs) as roof-integrated energy supply systems at the district scale. However, the performance of these systems not only depends on good configurations but also on optimal building typologies. The design process of buildings-integrated TSSCs on a district scale reflects a complex multi-criteria problem, where several conflicting concerns from multiple stakeholders need to be addressed. Thus, the proposed method aims to support the multi-criteria decision-making process in the early-stage design of sustainable districts utilizing TSSC technology. The method contributes to the design of the TSSCs relative to district designs. Our method enables design generation according to a set of decision variables related to the district (roof type and slope, orientation, building height, width, and length), and TSSC (type, geometric ratio, separation distance between mirrors, modules number, and solar cell size). The method uses a parametric modeling approach combined with a multi-objective optimization algorithm (NSGA-II) that enables design optimization of the district and TSSCs in two consecutive steps. The two-step design optimization allows finding optimal district designs for maximizing cumulative direct normal irradiance (DNI) and minimizing the total energy demand, and TSSC designs for maximizing average monthly load match index (av.LMI) (a ratio of energy yield to demand) and minimizing the average covered roof area occupied by modules. We validated the proposed method in an illustrative case study of ‘Buckower Felder’, a district in the city of Berlin (Germany). The illustrative application shows that our method enables the performance-driven, generative design of both; district and building-integrated TSSCs and searches for the most appropriate solutions i.e., urban designs for maximum DNI and minimum demand, and TSSC designs for maximum av.LMI and minimum covered roof area. Results indicate that there is a trade-off between objectives, where district design with high DNI (>4500 kW/m2/h/month) reflects high energy demand (8.6e + 05 kWh/month). Similarly, TSSC designs ensuring high av.LMI (>1.0) require a large roof area (>47 %). Given these trade-offs, the method can meaningfully support the decision-making process. Thus, the method allows for large-scale integration of TSSCs with buildings at an urban scale and supports solar energy planning and energy transition policies for sustainable districts.

Towards the Integration of Sustainable Transportation and Smart Grids: A Review on Electric Vehicles’ Management

In this paper, a survey is presented on the use of optimization models for the integration of electric vehicles (EVs) and charging stations (CSs) in the energy system, paying particular attention both to planning problems (i.e., those problems related to long term decisions such as the siting and sizing of CSs), and operational management problems (i.e., the optimal scheduling of EVs in smart grids, microgrids and buildings taking into account vehicle-to-grid (V2G) capabilities). Moreover, specific attention was dedicated to decision problems that couple transportation and electrical networks, such as the energy demand assessment for a vehicle over a path and routing and charging decision problems for goods and people transportation. Finally, an effort was dedicated to highlighting the integration and the use of EVs in very recent regulation frameworks, with specific reference to the participation in the balancing market through the figure of an aggregator and the inclusion in the management of Energy Communities (ECs) and sustainable districts.

Whose Knowledge Counts in the Planning of Urban Sustainability? – Investigating Handbooks for Nudging and Participation

When planning sustainable districts, planners mediate between the knowledge claims of citizens and experts. The planning strategies nudging and participation provide contradictory ideas about how planners can perform this mediation. We analyse handbooks for the two strategies, guided by the question: whose knowledge counts? These handbooks provide citizens, experts and planners with varying degrees of authority. While nudging positions behavioural experts as holding authority, and citizens are central in participation, planners feature in the background in both strategies. We show how these seemingly apolitical strategies are actually value-laden. Implementing them literally will undermine planning for urban sustainability.

Identification of Sustainable Development Priorities for Agriculture through Sustainable Livelihood Security Indicators for Karnataka, India

To cope with worsening climate change and widening intergenerational equity issues, more impetus should be given to sustainable development. India, predominantly an agrarian economy, faces most pressing issues of sustainable development with a complex territorial hegemony of the population and their dynamic food demands. Regional production systems play a vital role in strengthening national sustainable development priorities in India. Hence, to realize the dimensions of sustainable development in a more meaningful way, sustainability needs to be prioritized in an agrarian economy. Sustainability is a complex phenomenon encompassing economic, ecological and equity dimensions. A modest attempt in this regard has been made to estimate normative sustainable indicators for Karnataka state considering 20 crucial indicators or variables governing different dimensions. Using principal component analysis and linear scoring techniques, a minimum dataset including forest cover, livestock and human population density, and cropping intensity governing ecological issues, groundwater availability and milk availability governing social equity issues, and net cropped area, land productivity, labor productivity, food grain productivity and fertilizer use governing economic efficiency was identified, constituting crucial indicators for the development of the sustainable livelihood security index. The computed index was used to classify districts in Karnataka into various sustainable categories. Among 27 districts, 13 districts were grouped as less sustainable, 4 as highly sustainable and 10 as moderately sustainable categories. This classification and knowledge provide clues for policy makers to transform less sustainable districts into moderately/highly sustainable ones by formulating suitable policies related to crucial factors. Formulated policies on crucial factors have a domino effect/causation effect and bring about desirable changes in all other indicator variables, leading to the sustainable development of the target districts in Karnataka. This approach can be used at different scales in other states in India and in other developing countries.

Graph-based algorithmic design and decision-making framework for district heating and cooling plant positioning and network planning

Although buildings are the single largest users of energy in cities, many individual building HVAC (heating, ventilation, and air conditioning) systems are energy inefficient. Sustainable district heating and cooling systems have been developed to address this inefficiency, however, the implementation of district heating and cooling systems is a complex, capital intensive multivariate problem. One critical engineering problem, the location of energy production plant and pipe network topology, has a major influence on the system performance as well as the life cycle cost, and therefore should be comprehensively studied and chosen. This paper proposes a novel algorithmic design and decision-making framework that uses multiple simultaneous criteria to generate and evaluate design alternatives of site selection and pipe network layout. The framework consists of three components: site location and topology generation, network sizing and evaluation, and multi-objective decision-making assistance. The proposed framework has been validated in a real-world district cooling greenfield project in China's metropolitan area. Results were compared against the engineers’ best practices. It has shown that the proposed framework could find equally good or better designs in engineering and financial performance with CAPEX reduction of up to 15%.

Distributed Energy Systems and Energy Communities Under Negotiation

New decentralized energy-generation technologies have turned economies of scale upside down while becoming more economically viable. At the same time, the increased penetration of information technologies has led to new opportunities to manage infrastructure in a less hierarchical, more flexible way. Together with citizen demands for control over energy, these two converging trends has put energy communities (ECs) on the agenda, potentially advancing the transition towards more sustainable energy systems, despite hindrances encountered on the way. This paper presents a case study of the planning process of a sustainable city district in Sweden, using participatory observations and interviews conducted with included stakeholders. We analyse how the included stakeholders has reasoned about establishing a sustainable energy system in the area, including a microgrid. The discussions on a microgrid comprised two parallel discourses, coexisting but seldomly explicitly confronted. The distribution system operator in the area promoted a distributed energy system (DES) solution, while the property developers opted for a microgrid organized more as a citizen energy community (CEC). We discuss why the CEC proponents so far has lost the battle of creating a community owned smart grid. We conclude that the different models, a DES and a CEC, comprise different values and an increased focus on energy communities could shift the transition pathway towards a more decentralized system involving other prioritise than just economical.