Environmental impacts of natural gas distribution networks within urban neighborhoods

This study uses the life cycle assessment methodology to analyze the type and origin of environmental impacts related to natural gas distribution networks in high and low density neighborhoods, and compares the environmental performance of two infrastructures in low density neighborhoods: a standard natural gas grid and a discontinuous system based on propane tanks. The results show that the impact per dwelling in the environmental categories studied is between 1.9 and 4.8 times higher in a low density neighborhood, depending on the impact category. Besides, in high density areas the main impact originates from components and materials related to the buildings and dwellings, whereas in low density areas the main impact originates on the neighborhood network. Given this last result, the advisability of substituting the neighborhood network by a discontinuous system based on propane tanks has been evaluated, obtaining as a result that when a single neighborhood pipe, longer than 1 km, is required to reach one user, it is environmentally preferable for all the studied environmental categories to use the propane tank system.     

Conflicting strategies towards sustainable heating at an urban junction of heat infrastructure and building standards

Approaches to ‘sustainability transitions’ stress the possibility of aligning actors around a shared vision of the future, e.g. at the scale of a city. Empirical accounts reveal how difficult such coordination often is due to contradictory views involved. How can we better understand related processes of searching and negotiation? What does this mean for the organization of decision making processes regarding long-term infrastructural change?We analyze a conflict which erupted in Freiburg, Germany when two strategies of reducing environmental impacts of space heating were to be applied in the Vauban ‘model district’: A) Efficient co-generation of heat and power (CHP) combined with district heating systems (DHS), and B) Reducing heat demand by low-energy designs and ambitious energy standards (‘passive house standard’). In order to understand the politics of infrastructure development, we unravel 1) enabling factors and driving forces of the conflict, 2) normative content of opposing viewpoints, 3) resources tapped into for settling the disagreement, and 4) the institutional setup of such decision making about energy policy priorities in the municipality.We reflect on implications of such a perspective on how policies and how governance arrangements should ideally be shaped and take a brief outlook on further research needed.     

Economic and environmental impacts of insulation in district heating pipelines

The determination of optimum thickness of insulation is often applied to energy technologies and building projects. In this study, the energy, economic and environmental evaluations of thermal insulation in district heating pipeline are discussed. The optimum insulation thickness, energy saving over a lifetime of 10 years, payback period and emissions of CO₂, CO and SO₂ are calculated for nominal pipe sizes and fuel types based on heating loads in Afyonkarahisar/Turkey. The life cycle cost analysis is used to determine the optimum thickness of the pipeline material in order to take into account the change in inflation that directly affect both the cost of pipeline material and fuels depending on fuel type. The results show that the highest value of optimum insulation thickness, energy savings, emissions and the lowest payback period are reached for a nominal pipe size of 200 mm. About three times more energy saving results by making 200 mm nominal pipe instead of 50 mm. Considering the economical and environmental advantages, the geothermal energy is a better choice and then fuel-oil. When thermal insulation is done in a district heating pipeline, there will be a significant reduction of 21% in the amount of CO₂ emitted to the atmosphere.     

Life cycle assessment of fuels for district heating: A comparison of waste incineration,biomass- and natural gas combustion

The aim of this consequential life cycle assessment (LCA) is to compare district heating based on waste incineration with combustion of biomass or natural gas. The study comprises two options for energy recovery (combined heat and power (CHP) or heat only), two alternatives for external, marginal electricity generation (fossil lean or intense), and two alternatives for the alternative waste management (landfill disposal or material recovery). A secondary objective was to test a combination of dynamic energy system modelling and LCA by combining the concept of complex marginal electricity production in a static, environmental systems analysis. Furthermore, we wanted to increase the methodological knowledge about how waste can be environmentally compared to other fuels in district-heat production. The results indicate that combustion of biofuel in a CHP is environmentally favourable and robust with respect to the avoided type of electricity and waste management. Waste incineration is often (but not always) the preferable choice when incineration substitutes landfill disposal of waste. It is however, never the best choice (and often the worst) when incineration substitutes recycling. A natural gas fired CHP is an alternative of interest if marginal electricity has a high fossil content. However, if the marginal electricity is mainly based on non-fossil sources, natural gas is in general worse than biofuels.     

A model for predicting the potential diffusion of solar energy systems in complex urban environments

The necessity to reduce greenhouse gases emission produced by energy building consumptions and to cut the energy bill (mainly due to the use of fossil sources) leads to the employment of renewable energy sources in new planned scenarios. In particular, more and more often municipal energy and environmental plans pay great attention to the possibilities of employment of the solar technologies at urban scale.     

北京市集中供热热源的探考

通过对北京市集中供热主要热源的分析,提出了存在的主要问题,认为解决方案是:扩大燃煤热电厂所占的供热比例,尽可能加快燃煤热电厂的建设,并提出实施要点。     

Development of a numerical simulation system toward comprehensive assessments of urban warming countermeasures including their impacts upon the urban buildings'' energy-demands

One of the detrimental effects caused by the urban warming phenomena is the increase of energy consumption due to the artificial air-conditioning of buildings in summer. In greater Tokyo, the temperature sensitivity of the peak electricity demand reaches up to 3%/°C in recent years, and about 1.5 GW of new demand is required as the daily maximum temperature increases by 1.0 °C. This huge demand for summer electricity is considered to be one of the common characteristics of big cities in Asian countries. In order to simulate this increase in cooling energy demands and to evaluate urban warming countermeasures from the viewpoint of buildings' energy savings, a numerical simulation system was developed adopting a new one-dimensional urban canopy meteorological model coupled with a simple sub-model for the building energy analysis. Then, the system was applied to the Ootemachi area, a central business district in Tokyo. Preliminary verification of the simulation system using observational data on the outdoor and indoor thermal conditions showed good results. Simulations also indicated that the cut-off of the anthropogenic heat from air-conditioning facilities could produce a cooling energy saving up to 6% with the outdoor air-temperature decrease by more than 1 °C in the summer urban canopy over Ootemachi area.     

Model-based assessment of the environmental impacts of fuel cell systems designed for eVTOLs

Hydrogen fuel cells have increasingly gained relevance for electric vertical take-off and landing aircraft due to their potential to overcome the main challenges related to batteries. Previous studies have investigated their feasibility for urban air mobility; however, a robust assessment of their environmental implications is still lacking. To fill this gap, this study follows a model-based life cycle engineering approach to quantify the environmental impacts of a fuel cell system designed for three ranges. The production burdens distributed along the lifetime are demonstrated, showing that, for the best case scenario, 70g CO₂-eq. per passenger-kilometer is achieved. Under the premise of green hydrogen production, the stack is the main contributor to the environmental impacts. This changes for non-renewable hydrogen production pathways, where hydrogen has the highest impact contributions. Better environmental performance results from short design ranges; however, systems designed for longer ranges will likely increase attractiveness in the future.     

EnerGis: A geographical information based system for the evaluation of integrated energy conversion systems in urban areas

A geographical information system has been developed to model the energy requirements of an urban area. The purpose of the platform is to model with sufficient detail the energy services requirements of a given geographical area in order to allow the evaluation of the integration of advanced integrated energy conversion systems. This tool is used to study the emergence of more efficient cities that realize energy efficiency measures, integrate energy efficient conversion technologies and promote the use of endogenous renewable energy. The model is illustrated with case studies for the energetic planning of the Geneva district (Switzerland).     

Mode selection of China's urban heating and its potential for reducing energy consumption and CO2 emission

China's carbon dioxide (CO₂) emission ranks the highest in the world. CO₂ emission from urban central heating, which has an average annual growth rate of 10.3%, is responsible for 4.4% of China's total CO₂ emission. The current policy for improving urban central heating focuses on replacing coal with natural gas. This paper analyzes the existing situation and problems pertaining to urban heating, and evaluates the potential for reducing energy consumption and CO₂ emission by heat pump heating. The results show that the current policy of replacing coal with natural gas for urban central heating decreases energy consumption and CO₂ emission by 16.6% and 63.5%, respectively. On the other hand, replacing coal-based urban central heating with heat pump heating is capable of decreasing energy consumption and CO₂ emission by 57.6% and 81.4%, respectively. Replacing both urban central and decentralized heating with heat pump heating can lead to 67.7% and 85.8% reduction in energy consumption and CO₂ emission, respectively. The decreases in CO₂ emission will account for 24.5% of China's target to reduce total CO₂ emission by 2020.     

An economic model for energisation and its integration into the urban energy planning process

It is widely recognised that access to and supply of modern energy play a key role in poverty alleviation and sustainable development. The emerging concept of energisation seems to capture this idea, and if implemented in its full complexity it should have multiple beneficial effects. To demonstrate this, an economic model is developed for an urban developmental context, drawing on the theory of urban ecosystems and illustrating energy and waste production and consumption issues with current South African data sets. This new understanding of the concept of energisation is then integrated into a local government energy planning process, by means of a checklist for energy planners, covering 18 aspects that between them affect all 7 identifiable tiers of the energy service supply network. A 6-step structured approach is proposed for integrating sustainable energisation into the first four phases of the advanced local energy planning (ALEP) tool.     

Realising local government visions for developing district heating: Experiences from a learning country

District heating (DH) has an important role to play in enabling cities to transition to low-carbon heating. Although schemes are commonplace in some countries, in ‘learning countries’ where building-level technologies make up the majority of heating systems there are numerous barriers to introducing DH. Local governments are seen as key actors in helping to create a ‘shared vision’ for DH amongst stakeholders.This study uses interviews with stakeholders from a range of sectors in the UK (an example of a learning country) to examine the visions of local actors for developing DH and the types of national policy that would support local implementation of these visions.The analysis shows that in engaging with DH development local governments seek multiple types of value. Realising this value will most likely happen by taking a long-term, planned approach to development. In contrast, national government policy is geared towards techno-economic criteria and may lead to only a minority of potential sites being developed, without realisation of wider social or environmental benefits aligned to local visions.The work highlights the importance of local strategic planning, enabled by aligned national policy, in realising the full economic, environmental and social benefits of DH.     

The effect of urban layout,street geometry and orientation on shading conditions in urban canyons in the Mediterranean

The paper presents the results of shading analysis which was carried out as part of a wider comparative analysis of two sites with different characteristics in terms of street geometry and urban density. The first experiment site was a traditional settlement in the island of Tinos, Greece, and the second was a relatively newly built part of the capital city of the island. Also a parametric shading analysis was carried out in order to examine a number of parameters that influence shading conditions in urban canyons.The paper aims in analyzing the effect of parameters such as urban layout, street geometry and orientation on solar access and shading conditions, which strongly affect urban canyon microclimate. The results of shading simulations are compared to the results of experimental measurements of air and surface temperatures and to parametric thermal analysis results. The conclusions can contribute in the formulation of urban design guidelines.     

Lifecycle impacts of natural gas to hydrogen pathways on urban air quality

In this paper we examine the potential air quality impacts of hydrogen transportation fuel from a lifecycle analysis perspective, including impacts from fuel production, delivery, and vehicle use. We assume that hydrogen fuel cell vehicles are introduced in a specific region, Sacramento County, California. We consider two levels of market penetration where 9% or 20% of the light duty fleet are hydrogen fuel cell vehicles. The following three natural gas to hydrogen supply pathways are assessed in detail and compared in terms of emissions and the resulting changes in ambient air quality: (1) onsite hydrogen production; (2) centralized hydrogen production with gaseous hydrogen pipeline delivery systems; and (3) centralized hydrogen production with liquid hydrogen truck delivery systems. All the pathways examined use steam methane reforming (SMR) of natural gas to produce hydrogen. The source contributions to incremental air pollution are estimated and compared among hydrogen pathways. All of the hydrogen pathways result in extremely low contributions to ambient air concentrations of _NOx${\mathrm{NO}}_x$, CO, particulates, and _SOx${\mathrm{SO}}_x$, typically less than 0.1% of the current ambient pollution for both levels of market penetration. Among the hydrogen supply options, it is found that the central SMR with pipeline delivery systems is the lowest pollution option available provided the plant is located to avoid transport of pollutants into the city via prevailing winds. The onsite hydrogen pathway is comparable to the central hydrogen pathway with pipeline systems in terms of the resulting air pollution. The pathway with liquid hydrogen trucks has a greater impact on air quality relative to the other pathways due to emissions associated with diesel trucks and electricity consumption to liquefy hydrogen. However, all three hydrogen pathways result in negligible air pollution in the region.     

地热+高温水源热泵区域供暖工程的环境影响分析

经过分析计算，对区域燃煤锅炉房供暖方式和地热＋高温水源热泵供暖方式对环境的影响做出比较．证明了地热＋高温水源热泵同燃煤锅炉供暖方式相比具有巨大的环境效益。     

Heat planning for fossil-fuel-free district heating areas with extensive end-use heat savings: A case study of the Copenhagen district heating area in Denmark

The Danish government plans to make the Danish energy system to be completely free of fossil fuels by 2050 and that by 2035 the energy supply for buildings and electricity should be entirely based on renewable energy sources. To become independent from fossil fuels, it is necessary to reduce the energy consumption of the existing building stock, increase energy efficiency, and convert the present heat supply from fossil fuels to renewable energy sources. District heating is a sustainable way of providing space heating and domestic hot water to buildings in densely populated areas. This paper is a theoretical investigation of the district heating system in the Copenhagen area, in which heat conservation is related to the heat supply in buildings from an economic perspective. Supplying the existing building stock from low-temperature energy resources, e.g. geothermal heat, might lead to oversized heating plants that are too expensive to build in comparison with the potential energy savings in buildings. Long-term strategies for the existing building stock must ensure that costs are minimized and that investments in energy savings and new heating capacity are optimized and carried out at the right time.     

Impact comparison of PV system integration into rural and urban feeders

This paper is directed to evaluate the impact that the future widespread use of photovoltaic grid connected systems (PVGCSs) will have on feeder operation. With a view to achieve a global vision of this impact, the present work investigates representative feeders located in different latitudes. Actual rural and urban distribution feeders belonging to the Spanish electric utility have been selected and analyzed in both northern and southern latitudes.

The analysis identifies the operating variables to assess the PV impact in the different feeders. These critical variables are related to the design and performance characteristics of the feeder. Meteorological conditions at the installation site, load patterns, PV allocation and penetration are the main factors affecting this PV impact.     

Merging of energy and environmental analyses for district heating systems

District heating (DH) systems, together with combined heat and power (CHP) plants, have been increasing both in number and interest over the last decade, but the environmental improvements are still controversial, because although there is usually a reduction in CO₂ emissions, a positive effect concerning other pollutants is not always certain. A limited number of works that pay particular attention to the local environmental effect due to DH plants have been found in a brief overview of DH papers. The energetic and environmental impact of a new DH+CHP plant has been investigated in the present paper, where this plant has been proposed to substitute the existing heating systems. The environmental aspects concerning the local variations due to some pollutants, such as sulfur oxides (SO_x), particulate matter (PM) and nitrogen oxides (NO_x), are in particular taken into account. The main data necessary for the analysis and the hypotheses that are useful to simulate the behavior of the local heating plant and DH plants (e.g. efficiency, the heating demand, etc.) are discussed. A dispersion model (Gaussian model) has been used to evaluate the effect at a local scale. Finally, a case study concerning a new DH+CHP plant in Northern Italy is presented and discussed.     

Heat distribution and the future competitiveness of district heating

The competitiveness of present and future district heating systems can be at risk when residential and service sector heat demands are expected to decrease in the future. In this study, the future competitiveness of district heating has been examined by an in depth analysis of the distribution capital cost at various city characteristics, city sizes, and heat demands. Hereby, this study explores an important market condition often neglected or badly recognised in traditional comparisons between centralised and decentralised heat supply.     

Life cycle impacts and costs of photovoltaic systems: Current state of the art and future outlooks

The photovoltaic energy sector is rapidly expanding and technological specification for PV has improved dramatically in the last two decades. This paper sketches the current state of the art and drafts three alternative scenarios for the future, in terms of costs, market penetration and environmental performance. According to these scenarios, if economic incentives are supported long enough into the next ten to twenty years, PV looks set for a rosy future, and is likely to play a significant role in the future energy mix, while at the same time contributing to reduce the environmental impact of electricity supply.