Indicators for the optimization of sustainable urban energy systems based on energy system modeling

Background Urban energy systems are responsible for 75% of the world’s energy consumption and for 70% of the worldwide greenhouse gas emissions. Energy system models are used to optimize, benchmark and compare such energy systems with the help of energy sustainability indicators. We discuss several indicators for their basic suitability and their response to changing boundary conditions, system structures and reference values. The most suitable parameters are applied to four different supply scenarios of a real-world urban energy system. Results There is a number of energy sustainability indicators, but not all of them are suitable for the use in urban energy system optimization models. Shortcomings originate from the omission of upstream energy supply chains (secondary energy efficiency), from limited capabilities to compare small energy systems (energy productivity), from excessive accounting expense (regeneration rate), from unsuitable accounting methods (primary energy efficiency), from a questionable impact of some indicators on the overall system sustainability (self-sufficiency), from the lack of detailed information content (share of renewables), and more. On the other hand, indicators of absolute greenhouse gas emissions, energy costs, and final energy demand are well suitable for the use in optimization models. However, each of these indicators only represents partial aspects of energy sustainability; the use of only one indicator in the optimization process increases the risk that other important aspects will deteriorate significantly, eventually leading to suboptimal or even unrealistic scenarios in practice. Therefore, multi-criteria approaches should be used to enable a more holistic optimization and planning of sustainable urban energy systems. Conclusion We recommend multi-criteria optimization approaches using the indicators of absolute greenhouse gas emissions, absolute energy costs, and absolute energy demand. For benchmarking and comparison purposes, specific indicators should be used and therefore related to the final energy demand, respectively, the number of inhabitants. Our example scenarios demonstrate modeling strategies to optimize sustainability of urban energy systems.

Telecommuting as a Sustainable Transportation Measure in Ecuador

The purpose of this article is to provide information to determine that telecommuting in Ecuador can be used as a measure of sustainable transport. Briefly, sustainable development is described, and certain definitions and approaches related to sustainable transport are covered, for instance, the Avoid-Shift-Improve (ASI) approach, as well as the Transport Demand Management (TDM), which serve to validate from a conceptual point of view the application and usefulness of telecommuting. An overview of the current situation in the transport sector in Ecuador is analyzed; the final energy demand; the environmental aspects related to transport, and the amount of public and private employees that are telecommuting. Taking into consideration some hypothesis, such as car ownership rate, the total amount of kilometers driven per year, the assumption of the distance travelled by employees who take public transportation; the assumptions helped to determine the savings that can be obtained through telecommuting in the present time. Therefore, these results would provide adequate information for decision makers to establish a conclusive pronouncement on whether or not support telecommuting as a valid working approach, and to develop the necessary policies to maintain it over time.

Actual energy savings of more than 1000 renovated buildings in Geneva

This study quantifies the annual energy-related retrofit rate of the Geneva building stock (1.7%), based on data concerning the delivered construction permits over the 2010 – 2018 period. By cross-cutting with final energy demand before and after retrofit, we derive an energy-efficient retrofit rate (0.6% for an improvement of 1 class at least, 0.2% for 2 classes at least). Results are analysed as a function of the construction period, as well as of the energy demand before retrofit.

Positive Energy Building Definition with the Framework, Elements and Challenges of the Concept

Buildings account for 36% of the final energy demand and 39% of CO2 emissions worldwide. Targets for increasing the energy efficiency of buildings and reducing building related emissions is an important part of the energy policy to reach the Paris agreement within the United Nations Framework Convention on Climate Change. While nearly zero energy buildings are the new norm in the EU, the research is advancing towards positive energy buildings, which contribute to the surrounding community by providing emission-free energy. This paper suggests a definition for positive energy building and presents the framework, elements, and challenges of the concept. In a positive energy building, the annual renewable energy production in the building site exceeds the energy demand of the building. This increases two-way interactions with energy grids, requiring a broader approach compared to zero energy buildings. The role of energy flexibility grows when the share of fluctuating renewable energy increases. The presented framework is designed with balancing two important perspectives: technical and user-centric approaches. It can be accommodated to different operational conditions, regulations, and climates. Potential challenges and opportunities are also discussed, such as the present issues in the building’s balancing boundary, electric vehicle integration, and smart readiness indicators.

From using heat to using work: reconceptualising the zero carbon energy transition

Recent evidence indicates that the key sources of energy for the zero carbon transition will be renewable electricity sources. The most rapidly expanding sources, photovoltaics and wind produce work, as electricity, directly rather than via heat engines. Making the assumption that these will be the dominant sources of energy in a future zero carbon system, the paper makes two new related and innovative contributions to the literature on the energy transition. First, it shows that the energy transition will be more than just a shift away from carbonaceous fuels, and that it is more usefully thought of as including a systemic shift from heat-producing to work-producing energy sources. Secondly, it shows that this enables very large improvements in the conversion efficiency of final energy, through the use of electricity and hydrogen, in particular in heating and transportation. The paper presents a thought experiment showing a reduction in final energy demand of up to 40% is likely from this effect alone. Technical standards and product regulation for end use conversion efficiency and/or service delivery efficiency seem likely to be key policy instruments.

COVID-19 impacts on energy demand can help reduce long-term mitigation challenge

The COVID-19 pandemic caused radical temporary breaks with past energy use trends. However, how a post-pandemic recovery will impact the longer-term energy transition is unclear. Here, we present a set of global COVID-19 shock-and-recovery scenarios that systematically explore the demand-side effect on final energy and GHG emissions. Our pathways project final energy demand reductions of 12 to 40 EJ/yr by 2025 and cumulative CO2 emissions reductions by 2030 of 28 to 53 GtCO2, depending on the depth and duration of the economic downturn and demand-side changes. Recovering from the pandemic with low energy demand practices - embedded in new patterns of travel, work, consumption, and production – reduces climate mitigation challenges. A low energy demand recovery reduces carbon prices for a 1.5°C consistent pathway by 19%, lowers energy supply investments until 2030 by 2.1 trillion USD, and lessens pressure on the upscaling of renewable energy technologies.

Analysis of the Impact of Self-Isolation of Residents during a Pandemic on Energy Demand and Indoor Air Quality in a Single-Family Building

This work presents the results of analysis of the final energy demand (Qk) for a single-family house in a pandemic situation and accompanying self-isolation of residents. It was assumed that the object of study is located in Bialystok (Poland). This analysis covers the impact of various factors such as specific periods of the active pandemic phase, the length of the inhabitants’ self-isolation period, the number of residents at home, and the type of energy source used in the building. Based on the results of computational experiments, a deterministic mathematical model of the relationship between these variables was developed, and the effects of the selected factors on the final energy demand were analyzed for the typical meteorological year (TMY) weather data. It turned out that the change in the length of the self-isolation period from 0 to 31 days caused an increase of Qk by about 6.5% for the analyzed building. When the number of inhabitants changed from 1 to 4, Qk increased by 34.7%. A change from 4 to 7 people causes an additional 26.7% increase in Qk. It was found that the structure of energy demand for this building operation during the period of inhabitants’ self-isolation also changed. With the increase in the length of the self-isolation period from 0 to 31 days, the electricity demand (Eel) increases by about 40–42%, while the demand for energy related to fuel consumption (Qg) decreases by about 7–10%. The article also presents an analysis of the impact of residents’ self-isolation on indoor air quality (IAQ) and thermal comfort. The simulation results showed that the use of variable air volume ventilation allows the CO2 concentration to be kept significantly below the limit value.

Renewable Energy Equivalent Footprint (REEF): A Method for Envisioning a Sustainable Energy Future

We present an alternative approach to estimating the spatial footprint of energy consumption, as this represents a major fraction of the ecological footprint (EF). Rather than depicting the current lack of sustainability that comes from estimating a footprint based on uptake of carbon emissions (the method used in EF accounting), our proposed “Renewable Energy Equivalent Footprint” (REEF) instead depicts a hypothetical world in which the electricity and fuel demands are met entirely from renewable energy. The analysis shows that current human energy demands could theoretically be met by renewable energy and remain within the biocapacity of one planet. However, with current technology there is no margin to leave any biocapacity for nature, leading to the investigation of two additional scenarios: (1) radical electrification of the energy supply, assuming 75% of final energy demand can be met with electricity, and (2) adopting technology in which electricity is used to convert atmospheric gases into synthetic fuel. The REEF demonstrates that a sustainable and desirable future powered by renewable energy: (i) may be possible, depending on the worldwide adoption of consumption patterns typical of several key exemplar countries; (ii) is highly dependent on major future technological development, namely electrification and synthetic fuels; and (iii) is still likely to require appropriation of a substantial, albeit hopefully sustainable, fraction of the world’s forest area.

Boosting Energy Efficiency and Solar Energy inside the Residential, Commercial, and Public Services Sectors in Mexico

The residential, commercial, and public sectors consume between 20% and 30% of final energy demand worldwide. Due to the intensive use of fossil fuels and conventional electricity, they also have an important participation in the emission of greenhouse gases (GHG). Taking Mexico as a case study, this article develops an alternative scenario that considers that in these sectors, buildings can generate energy for self-consumption or to supply it to the power network—for which four solar energy options are analyzed. In addition, to manage and rationalize the energy demand of these buildings, eight energy efficiency measures are studied. These options were selected on the basis that they are technically and economically feasible to implement in buildings in Mexico. The results reveal that by 2030, in relation to the GHG trend scenario, this mitigation scenario reduces 23.5 million tons of carbon dioxide equivalent (MtCO2e) in the residential (19 MtCO2e), commercial (2.6 MtCO2e), and public services sectors (1.9 MtCO2e), while by 2035 it reaches 45 MtCO2e; which far exceed the avoided emissions goals established in Mexico’s nationally determined contributions (NDC) for 2030 (5 MtCO2e) for the residential and commercial sectors. Therefore, it is possible to increase the ambition for mitigation in these sectors, as well as including the public sector, in a renewed Mexico’s NDC. This mitigation scenario generates a total economic benefit of $7.7 billion, which means that it does not generate an overall incremental cost, but requires an incremental investment of over $9 billion USD, which is a financing challenge to achieve this scenario.