Carbon Intensity Of Electricity Research Articles

Factors influencing the life-cycle GHG emissions of Brazilian office buildings

Effective mitigation of greenhouse gas (GHG) emissions in the buildings sector requires a full understanding of the factors influencing emissions over the life-cycle of buildings, particularly in places where large additions to the building stock are expected. Currently, little is known about what affects the GHG emissions of buildings located in warmer climates, a typical situation for many emerging economies. This paper presents a study of emissions from Brazilian office buildings using building archetypes. A sensitivity analysis explores possible parameter ranges, various contributions to life-cycle impacts and their key drivers. For each of the 1000 building variations in the sample, the emissions were calculated using a life-cycle assessment. Multivariate regression analysis enabled the study of the results’ sensitivity to 10 parameters, influencing building operation, design and others. The emissions ranged from 20 to 106 kg CO₂-eq/m² gross floor area and year. Electricity mix, climate and cooling efficiency were the most impactful parameters, but building component service time was also significant. <em><strong>Policy relevance</strong></em> Emerging economies are expected to rapidly increase their building stock and energy use, particularly for cooling in the coming decades. The findings show the key factors influencing the GHG emissions of office buildings in warm climates, typical for many emerging economies, such as Brazil. For effective mitigation, priority should be placed on reducing the carbon intensity of electricity and encouraging highly efficient heating, ventilation and air-conditioning systems. Policymakers may want to offer incentives for office buildings with a combination of natural ventilation and mechanical cooling, because they were less emission-intensive in every investigated city. The benefits are the biggest for buildings in which a high proportion of windows can be opened for natural ventilation.

Carbon emission and cost analysis of vehicle technologies for urban taxis

Our study compared vehicle technologies to reduce the carbon emissions of the Hong Kong taxi fleet. An environmental cost-benefit analysis was developed to measure the tons of carbon dioxide equivalent (CO2-eq) potentially abated and the incurred cost over the period 2021–2030 by the substitution of the current fleet with electric vehicles (EVs), fuel cell electric vehicles (FCEVs), and more efficient internal combustion engine vehicles (ICEVs). Our result highlights that FCEVs fueled with hydrogen from renewables and EVs with battery swap stations have lower abatement costs (i.e., cost incurred/carbon saved). The selection of a relatively low-cost option between EVs with battery swap stations and FCEVs with hydrogen from renewables depends on the reduction of electricity carbon intensity versus whether an economic and reliable import of hydrogen from renewables can be secured. Taxi miles traveled affect the vehicle technology abatement cost ranking. Overall, our study provides insight into sustainable urban taxi transition.

Quantification of the carbon intensity of electricity produced and used in Europe

The EU has a comprehensive legislation to facilitate the energy transition towards a low carbon energy system and achieve the EU’s Paris Agreement commitments for reducing greenhouse gas emissions. The European Green Deal is an integral part of the EU strategy for a sustainable and climate neutral economy by 2050. The decarbonisation of the power generation is essential to achieve the goal of decarbonising the energy and transport sectors. This paper presents a study conducted to quantify the carbon emissions associated to the production of electricity produced and used in European countries, based on a comprehensive methodology developed for this purpose. A spreadsheet model has been developed that considers the various sources for electricity generation, the type of plants, conversion efficiencies, upstream emissions and emissions from power plant construction, as well as the electricity trade. The results show the greenhouse gas emissions from the production and use of electricity in all European countries, revealing significant variations between countries. The carbon intensity of electricity shows a clear reduction trend since 1990, for most of the European countries. In the European Union, carbon intensity of electricity used at low voltage degreased from 641 gCO2eq/kWh in 1990 to 334 gCO2eq/kWh in 2019, and this trend is expected to continue in the coming years.

A comparative life cycle assessment of silicon PV modules: Impact of module design, manufacturing location and inventory

Life Cycle Assessments (LCA) of single-crystalline silicon (sc-Si) photovoltaic (PV) systems often disregard novel module designs (e.g. glass-glass modules) and the fast pace of improvements in production. This study closes this research gap by comparing the environmental impacts of sc-Si glass-backsheet and glass-glass modules produced in China, Germany and the European Union (EU), using current inventory data. Results show lower potential environmental impacts for glass-glass compared to glass-backsheet modules and lower impacts for production in the EU and Germany compared to China for most impact categories. Concerning climate change, glass-backsheet (glass-glass) modules produced in China, Germany or the EU are linked to emissions of 810 (750), 580 (520) and 480 (420) kg CO2-eq/kWp, respectively. This corresponds to CO2-eq emission reductions of 30% for German and 40% for European production compared to Chinese production, and 8–12.5% reduction in glass-glass compared to glass-backsheet modules. Carbon intensity of produced electricity, excluding balance of system (BOS), amounts to 13–30 g CO2-eq/kWh, depending on production location and electricity yield calculation method. A warranty-based yield calculation method shows the influence of different lifetime electricity yields of glass-glass and glass-backsheet modules on the potential environmental impacts. This study identifies module efficiency, energy requirements, silicon consumption and carbon-intensity of electricity during production as significant levers for future reductions of environmental impacts. It emphasizes the importance of up-to-date inventories and current modelling of electricity mixes for representative LCA results of PV modules. Lastly, this paper argues that more differentiated methodological guidelines are needed to incentivize the development of sustainable module designs.

The potential of direct steam cracker electrification and carbon capture & utilization via oxidative coupling of methane as decarbonization strategies for ethylene production

Ethylene is one of the most important building blocks in the chemical industry, making its decarbonization a natural starting point for achieving emission targets of the industrial sector. We here present an in-depth analysis of carbon and energy flows of two main strategies that could potentially reduce emissions from ethylene production: (i) direct electrification of heat supply in the traditional steam cracking process and (ii) indirect electrification through a novel production route based on Power-to-Gas and Oxidative Coupling of Methane (OCM–PtG). By calculating carbon footprints of all processes as a function of electricity carbon intensity, we show that fueling the steam cracker with renewable electricity can achieve a maximal emission reduction of 30% while OCM–PtG can achieve a net-zero emission production process if electricity supply is completely decarbonized and resulting products are at least partially recycled at the end of their life cycle. An integrated analysis within an economy-wide, global climate policy scenario shows that these conditions are likely to be met only after 2030 even under very stringent climate policy in line with the climate targets of the Paris agreement. If not met, OCM–PtG can actually increase the carbon footprint of ethylene. We also show that OCM–PtG is currently not cost-competitive, but can become so under suitable boundary conditions. It becomes clear that policy instruments that support the market introduction of carbon capture utilization technologies like OCM–PtG are only justified, if conditions are ensured that enable a positive mitigation potential over their life cycle.

Low-carbon production of iron and steel: Technology options, economic assessment, and policy

Summary Given increased urgency to transition the global economy to net-zero CO2 emission, governments and industry have increased focus on decarbonizing hard-to-abate sectors, including steel making, which contributes roughly 6% of global CO2 emission and 8% of energy-related emission (including power consumption emission). This paper reviews current global iron and steel production and assesses available decarbonization technologies, including hydrogen injection, solid biomass substitution, zero-C electricity substitution, carbon capture and storage (CCS) retrofit, and combinations of these decarbonization approaches. Blast furnace-basic oxygen furnace (BF-BOF) dominates production (71%) and is particularly stubborn to any decarbonization technology. Direct reduced iron to electric arc furnace (DRI-EAF) production is 5% and growing, it appears to have better decarbonization potential to move toward net-zero. Secondary steel production using mainly steel scrap in electric arc furnace (EAF-scrap) is 24% of global production and has both the lowest energy consumption and is technically simplest to decarbonize through electrification but is limited in market share to recycled steel capacity. Of the options assessed, blue hydrogen, carbon neutral biomass, and CCS appear to have the lowest cost and highest technical maturity. However, no single approach today can deliver deep decarbonization to the iron and steel industry and all approaches lead to substantial production cost increase. No uniform ideal solution exists, and different geographies, infrastructure, and economies will determine the local optimum solution with viability and cost. Policy measures will be required to provide financial incentives for decarbonization and to avoid unwelcome outcomes such as emissions leakage or job loss.

Well-to-wheel greenhouse gas emissions of heavy-duty transports: Influence of electricity carbon intensity

There are several alternatives for how to phase out diesel in heavy-duty transports, thereby reducing the sector’s climate change impact. This paper assesses the well-to-wheel (WTW) greenhouse gas (GHG) emissions of energy carriers for heavy-duty vehicles, analyzing the effect of the carbon intensity of the electricity used in production. The results show that energy carriers with high electricity dependence are not necessarily better than diesel from a WTW perspective. In particular, fuels produced through electrolysis are not well suited in carbon-intense electricity systems. Conversely, waste-based biofuels have low GHG emissions regardless of the electricity system. Battery-electric buses show a large reduction of GHG emissions compared to diesel buses and many other alternatives, while battery-electric trucks have higher GHG emissions than diesel in carbon intense electricity systems. Thus, electrifying transports or switching to renewable fuels will not suffice if the electricity system is not made renewable first.

The Role of National Energy Policies and Life Cycle Emissions of PV Systems in Reducing Global Net Emissions of Greenhouse Gases

The energy sector and electricity generation in particular, is responsible for a great share of the global greenhouse gas (GHG) emissions. World electricity generation is still largely based on the burning of fossil fuels. However, Brazil has already a very low electricity carbon intensity due to the country’s large hydropower capacity. In countries with low grid carbon intensities such as Brazil, the investment in photovoltaic solar systems (PVSS) even if it is cost-effective, might become challenging as any new generation competes essentially against other renewable generation and the carbon offset is not a key driver for investment anymore. This study builds further upon that case to examine if national renewable energy incentives could actually lead to an increase of global net carbon emissions from the installation of PVSS in countries with a low grid carbon intensity. The study presents a life cycle analysis (LCA) of ten photovoltaic systems representative of the different operational conditions in regions across Brazil. It was found that the average energy payback time of the studied PV plants is between 3 and 5 years of operation. This result shows the feasibility and viability of such investments in the Brazilian context. When the LCA was integrated into the analysis though, the results showed that the “local” direct emissions avoidance from two out of ten studied PV plants would not manage to offset their “global” life cycle emissions due to the 2020 projected Brazilian grid emission factor which is already low. It is important to recognize that public policies of unrestricted, unconditional stimulus to photovoltaic systems investment might not help towards reducing global net emissions when the PV systems are installed at countries with a low carbon emission electric matrix. That is also something to consider for other countries as the carbon intensity of their grids will start reducing at levels similar to Brazil’s. It is likely that in the near future, the real net carbon offset achieved by PV systems at the global level will be largely defined by the manufacture procedures and the production’s carbon intensity at the country of origin of the PV panels.

Limited climate benefits of global recycling of pulp and paper

A circular economy is expected to achieve sustainability goals through efficient and circular use of materials. Waste recycling is an important part of a circular economy. However, for some materials, the potential environmental benefits of recycling are unclear or contested. Here, we focus on the global paper life cycle, which generates 1.3% of global greenhouse gas emissions, and estimate the climate change mitigation potential of circularity. We model material use, energy use and emissions up to 2050 for various levels of waste recycling and recovery. We show that emission pathways consistent with a 2 °C global warming target require strong reductions in the carbon intensity of electricity and heat generation. We also show that additional recycling yields small or negative climate change mitigation benefits when it requires high-carbon grid electricity and displaces virgin pulping that is powered by low-carbon pulping by-products. The results indicate that circular economy efforts should carefully consider the energy implications of recycling.

Decarbonizing US passenger vehicle transport under electrification and automation uncertainty has a travel budget

The transportation sector is at the beginning of a transition represented by electrification, shared mobility, and automation, which could lead to either increases or decreases in total travel and energy use. Understanding the factors enabling deep decarbonization of the passenger vehicle sector is essential for planning the required infrastructure investments and technology adoption policies. We examine the requirements for meeting carbon reduction targets of 80% and higher for passenger vehicle transport in the United States (US) by midcentury under uncertainty. We model the changes needed in vehicle electrification, electricity carbon intensity, and travel demand. Since growth in fleet penetration of electric vehicles (EVs) is constrained by fleet stock turnover, we estimate the EV penetration rates needed to meet climate targets. We find for a base case level of passenger vehicle travel, midcentury deep decarbonization of US passenger transport is conditional on reducing the electricity generation carbon intensity to close to zero along with electrification of about 67% or 84% of vehicle travel to meet decarbonization targets of 80% or 90%, respectively. Higher electricity generation carbon intensity and degraded EV fuel economy due to automation would require higher levels of fleet electrification and/or further constrain the total vehicle travel allowable. Transportation deep decarbonization not only depends on electricity decarbonization, but also has a total travel budget, representing a maximum total vehicle travel threshold that still enables meeting a midcentury climate target. This makes encouraging ride sharing, reducing total vehicle travel, and increasing fuel economy in both human-driven and future automated vehicles increasingly important to deep decarbonization.

Consequential LCA for territorial and multimodal transportation policies: method and application to the free-floating e-scooter disruption in Paris

The indirect environmental impacts of transportation disruptions in urban mobility are frequently overlooked due to a lack of appropriate assessment methods. Consequential Life Cycle Assessment (CLCA) is a method to capture the environmental consequences of the entire cause and effect chain of these disruptions but has never been adapted to transportation disruption at the city scale. This paper proposes a mathematical formalization of CLCA applied to a territorial mobility change. The method is applied to quantify the impact on climate change of the breakthrough of free-floating e-scooters (FFES) in Paris. A FFES user survey is conducted to estimate the modal shifts due to FFES. Trip substitutions from all the Parisian modes concerned are considered – personal or shared bicycles and motor scooters, private car, taxi and ride-hailing, bus, streetcar, metro and RER (the Paris metropolitan area mass rapid transit system). All these Parisian modes are assessed for the first time using LCA. Final results estimate that over one year, the FFES generated an extra thirteen thousand tons of CO2eq under an assumption of one million users, mainly due to major shifts coming from lower-emitting modes (60% from the metro and the RER, 22% from active modes). Recommendations are given to enhance their carbon footprint. A scenario analysis shows that increasing the lifetime mileage is insufficient to get a positive balance: reducing drastically servicing emissions is also required. A sensitivity analysis switching the French electricity mix for eleven other country mixes suggests a better climate change effect of the FFES in similar metropolitan areas with higher electricity carbon intensity, such as in Germany and China. Finally, the novelty and the limits of the method are discussed, as well as the results and the role of e-scooters, micromobility, and shared vehicles towards a sustainable mobility.

Quantifying the effects of vehicle technical performance and electricity carbon intensity on greenhouse gas emissions from electric light truck: A case study of China

The concept of an electric light truck (ELT) with green environmental protection has been accepted by governments and purchasers with the promotion of Made in China (2025) and the Blue Sky Protection Campaign. However, the ELT's characteristics of low gas emissions and zero pollution should be further investigated. An electric light truck emissions index (ELTEI) is established to explore the greenhouse gas (GHG) emissions of ELT. The ELTEI considers electricity carbon intensity and vehicle technical performance that includes temperature-capacity compensation coefficient, battery attenuation coefficient, energy consumption per unit load and battery system energy density. Results of a case study in China show that sub-zero temperature leads to significant fluctuations in the temperature-capacity compensation coefficient, which can increase the GHG emissions of ELT in the northern provinces. In the southern and central provinces, ELT can replace diesel light truck to reduce GHG emissions after improving the battery attenuation coefficient by 15% when ELT is utilized for 4 years. Compared with increasing the battery weight to decrease the value of energy consumption per unit load, increasing the battery system energy density to reduce the vehicle weight can fundamentally lower GHG emissions. The reduction ratio is inversely proportional to the minimum average temperature in the first quarter by reducing the electricity carbon intensity to minimize the GHG emissions of ELT. Insights derived from this study can provide available suggestions for research on the GHG emissions of ELT.

Renewable OME from biomass and electricity—Evaluating carbon footprint and energy performance

AbstractRenewable drop‐in fuels provide a short‐ to medium‐term solution to decreasing carbon dioxide emissions from the transport sector. Polyoxymethylene ethers (OME) are among interesting candidates with production pathways both from biomass (bio‐OME) as well as electricity and CO2(e‐OME) proposed. In the present study, both bio‐ and e‐OME production via methanol are assessed for energy performance and carbon footprint. Process integration methods are applied to evaluate synergies from colocating methanol production with further conversion to OME. Even a hybrid process, combing bio‐ and e‐OME production is evaluated. The energy efficiency of bio‐OME is considerably higher than for the e‐OME pathway, and colocation synergies are more evident for bio‐OME. Carbon footprint is evaluated according to EUs recast Renewable Energy Directive (RED II). If renewable electricity and natural gas are used for power and heat supply, respectively, results indicate that all pathways may be counted toward the renewable fuel targets under RED II. The largest emissions reduction is 92.8% for colocated hybrid‐OME production. Carbon footprints of e‐ and hybrid‐OME are highly sensitive to the carbon intensity of electricity, and the carbon intensity of the heat supply has a major impact on results for all pathways except colocated bio‐ and hybrid‐OME.

Multiobjective component sizing of a hybrid ethanol-electric vehicle propulsion system

Concerns over energy efficiency and greenhouse gas (GHG) emissions are driving research investments into advanced propulsion technologies. Plug-in hybrid electric vehicles (PHEVs) can provide a bridge that connects transport electrification to renewable bioenergy sources such as ethanol. However, it remains unclear how this pathway can simultaneously address economic, energy and environmental goals. To tackle this challenge, the present study explores, for the first time, the multiobjective optimal sizing of PHEVs powered by low-carbon sources of electricity and ethanol-gasoline blend. The empirical ethanol-gasoline blend model is incorporated into the PHEV simulation whose relevant parameters are validated using laboratory data from the European Commission – Joint Research Centre. We develop a full picture of the use-phase well-to-wheel (WTW) GHG emissions from ethanol, gasoline and grid electricity and their energy consumptions. Consequently, market-oriented PHEV sizing solutions are provided as per the power utility generation portfolio and automobile fuel properties of the target region. The results indicate that better performances of the PHEV, regarding GHG emissions and energy consumption, are associated with larger battery size and smaller engine displacement but result in a higher cost-to-power ratio. Specifically, for E25-fuelled PHEVs in markets with world average electricity carbon intensity, every 1.0 USD/kW increase in cost-to-power ratio leads to savings of 1.6 MJ energy consumption and 1.7 g CO2-eq/km WTW GHG emissions. Moreover, a clear benefit of using E25 in the hybrid propulsion system is identified, where the energy consumption and GHG emissions can be reduced by 5.9% and 12.3%, respectively.

Trends in life cycle greenhouse gas emissions of future light duty electric vehicles

The majority of previous studies examining life cycle greenhouse gas (LCGHG) emissions of battery electric vehicles (BEVs) have focused on efficiency-oriented vehicle designs with limited battery capacities. However, two dominant trends in the US BEV market make these studies increasingly obsolete: sales show significant increases in battery capacity and attendant range and are increasingly dominated by large luxury or high-performance vehicles. In addition, an era of new use and ownership models may mean significant changes to vehicle utilization, and the carbon intensity of electricity is expected to decrease. Thus, the question is whether these trends significantly alter our expectations of future BEV LCGHG emissions.To answer this question, three archetypal vehicle designs for the year 2025 along with scenarios for increased range and different use models are simulated in an LCGHG model: an efficiency-oriented compact vehicle; a high performance luxury sedan; and a luxury sport utility vehicle. While production emissions are less than 10% of LCGHG emissions for today’s gasoline vehicles, they account for about 40% for a BEV, and as much as two-thirds of a future BEV operated on a primarily renewable grid. Larger battery systems and low utilization do not outweigh expected reductions in emissions from electricity used for vehicle charging. These trends could be exacerbated by increasing BEV market shares for larger vehicles. However, larger battery systems could reduce per-mile emissions of BEVs in high mileage applications, like on-demand ride sharing or shared vehicle fleets, meaning that trends in use patterns may countervail those in BEV design.

Techno-economic analysis of coke oven gas and blast furnace gas to methanol process with carbon dioxide capture and utilization

This paper documents a process for converting coke oven gas (COG) and blast furnace gas (BFG) from steel refineries into methanol. Specifically, we propose the use of blast furnace gas (BFG) as an additional carbon source. The high CO2 and CO content of BFG make it a good carbon resource. In the proposed process, CO2 is recovered from the BFG and blended with H2O, H2, and CH4-rich COG to reform methane. Optimized amounts of H2O and CO2 are used to adjust the (H2 – CO2)/(CO + CO2) molar ratio in order to maximize the amount of methanol that is produced. In addition, the desulphurization process was modified to enable the removal of sulfur compounds, especially thiophene, from the COG. The process design and simulation results reported herein were then used to determine any potential environmental and economic benefits. This research is based on off-gas conditions provided by ArcelorMittal Dofasco (AMD), Hamilton, Ontario. In order to determine which conditions are most desirable for this retrofit strategy, potential greenhouse gas reduction and economic benefits were analyzed. In particular, this analysis focused on the heating utility chosen for methane reformation prior to methanol synthesis. To this end, COG, BFG, and natural gas (NG) were compared. The results showed that using BFG/NG as a heating utility can produce greater economic gains, and that synthesizing COG + BFG to methanol results in greater economic and environmental gains than solely producing electricity (the status quo). Compared to current operating procedures, the proposed process could potentially increase net present values by up to $54 million. The carbon efficiency achieved was up to 72%. An additional 0.73 kg of CO2 from BFG is needed for every 1 kg of MeOH produced. About 52% of feedstock energy is converted to MeOH, with another 33% recovered in the form of utilities. The exergy efficiency of the recommended version of the system is about 61%. The business case for converting CO2 into methanol highly depends on the local electricity grid carbon intensity. For Ontario, it can reduce direct CO2 emissions by 228 ktonne per year, and fix up to 246 ktonne CO2 into methanol per year. In addition, analyses of location effects, CO2 taxes, electricity prices, electricity carbon intensity, methanol prices, and income taxes indicated that MeOH production is highly recommended for Ontario, Mexico, the USA, and China applications. For USA, build MeOH plant is recommended for Finland, whether to do this retrofit or not is inconclusive. For Finland, the results are inconclusive, other strategies may be equally suitable. Aspen Plus Simulation files and other source code have been open-sourced and are available to the reader.

Пріоритетні напрями довгострокового розвитку національної атомної енергетики

We established that the formation of prospects of the development of national nuclear power depends, first of all, on such key factors as the term of extension of the service life of existing NPP units, the hardness of regime constraint on their operation in an energy system, and system-wide economic efficiency and environmental friendliness of a certain structure of generating capacities in the United Power System of Ukraine. We carried out an analysis of the current state of implementation of new light-water reactors of high power and promising small modular reactors. Based on the estimates of prospects of the implementation of new nuclear power units, obtained by using the mathematical model of long-term forecasting the development of structure of generating capacities in the power system, taking into account the need to replace operating NPPs, we determined the priority areas of long-term development of national nuclear power. In the formation of decisions concerning the introduction of new power units, it is quite important to take into account the dynamics of their commission and decommission with regard for their operation life and unit capacity at the projected growth of demand for electrical energy. It has been established that, in the case of hardening the requirements to carbon-intensity of electricity, including an increase in the CO2 emissions charge, it is advisable, instead of construction of new coal-fired power units of TPPs in the period 2036–2040, to increase the capacity of NPPs, including the introduction of maneuvering units with small modular reactors as a low-carbon source of electricity production with enhanced operational safety to ensure sustainability, reliability, and efficiency of the functioning of Ukrainian UPS. We also determined the feasibility of replacing existing nuclear power units that are decommissioning by new advanced third-generation powerful nuclear power units.

Optimal coordinated operation of a multi-energy community considering interactions between energy storage and conversion devices

An optimal coordinated operation model of comprehensive energy storage and conversion devices was built by considering interdependency in a multi-vector energy community, to achieve an overall optimum. The model determined the storage size, the operation strategies of energy storage and conversion devices and scenario analysis was further conducted. The proposed sequential method solved the complex mixed-integer nonlinear programming (MINLP) problem by decomposing the multi-energy system into a subsystem of conversion devices and a PV-battery subsystem, which reduced the computation complexity. Firstly, electricity, heat and gas networks were modelled in an integrated manner and with a suitable level of detail for operational purposes. The integrated electrical-hydraulic-thermal-gas flow equations imposed by multi-energy networks were formulated as equality constraints in the optimization. The optimal operation of conversion technologies with increasing net-load variability on the consumer load profiles was determined. Secondly, the design and operation of PV-battery systems was investigated to provide economic incentives for storage owners. The total costs, the self-consumption ratio (SCR), the internal return rate (IRR) of PV-battery systems were calculated. In scenario analysis, interactions between multi-energy network operation limits as well as the impact of energy conversion devices on PV-battery systems were demonstrated. It showed that the option of Combined Heat and Power (CHP) was advantageous without considering PV-battery systems using 2016 financial data. However, considering the profit of PV-battery systems and the declining grid electricity carbon intensity, the option of heat pumps was advantageous and may be a favorable option in the long term.

Lifecycle Environmental Impact Assessment of an Overtopping Wave Energy Converter Embedded in Breakwater Systems

Overtopping breakwater systems are among the most promising technologies for exploiting wave energy to generate electricity. They consist in water reservoirs, embedded in piers, placed on top of ramps, higher than sea-level. Pushed by wave energy, seawater fills up the reservoirs and produces electricity by flowing back down through low head hydro turbines. Different overtopping breakwater systems have been tested worldwide in recent years. This study focuses on the Overtopping BReakwater for Energy Conversion (OBREC) system that has been implemented and tested in the harbor of Naples (Italy). The Life Cycle Assessment of a single replicable module of OBREC has been performed for analyzing potential environmental impacts, in terms of Greenhouse Gas Emissions, considering construction, installation, maintenance, and the operational phases. The Carbon Footprint (i.e. mass of CO2eq) to build wave energy converters integrated in breakwater systems has been estimated, more specifically the “environmental investment” (i.e. the share of Carbon Footprint due to the integration of wave energy converter) needed to generate renewable electricity has been assessed. The Carbon Intensity of Electricity (i.e. the ratio between the CO2eq emitted and the electricity produced) has been then assessed in order to demonstrate the profitability and the opportunity to foster innovation in the field of blue energy. Considering the impact for implementing an operational OBREC module (Carbon Footprint = 1.08 t CO2eq; Environmental Investment = 0.48 t CO2eq) and the electricity production (12.6 MWh/yr per module), environmental benefits (avoided emissions) would compensate environmental costs (i.e. Carbon Footprint; Environmental Investment) those provided within a range of 25 and 13 months respectively.

Insights from Past Trends in Exergy Efficiency and Carbon Intensity of Electricity: Portugal, 1900–2014

We use the societal exergy analysis to identify periods and factors controlling efficiency dilution and carbon deepening of electricity in Portugal from 1900 to 2014. Besides estimating the carbon intensity of electricity production, we propose a new indicator, the carbon intensity of electricity use, which quantifies CO2/kWh of electricity derived useful exergy. Results show final to useful efficiency dilution until World War I (50% to 30%) due to a decrease in share of the high-efficiency transport sector and from mid-1940s to 1960 and mid-1990s onwards (58% to 47% and 47% to 40%) due to an increase in share of the low efficiency commercial and residential sector. Decarbonization from 1900 to mid-1960s, with carbon intensities of electricity production and use dropping respectively from 12.8 to 0.2 and from 33.6 to 0.4 kg CO2/kWh due to an increase in thermoelectricity efficiencies and an increase in share of hydro. Then, a period of carbon deepening until 1990 with carbon intensities tripling due to a shift in shares from hydro to thermoelectricity and more recently a period of decarbonization with carbon intensities decreasing to 0.35 and 0.9 kg CO2/kWh, due to the increase in renewable electricity despite a dilution in final to useful efficiency.