Low-carbon measures for Fiji's land transport energy system

Road transport in Fiji is fully dependent on petroleum fuels. This study is a first for Fiji where fuel demand for land transport is studied under some clean transportation strategies. Long-range Energy Alternatives Planning (LEAP) tool is used with 2016 as the base year and 2040 as the end year. In 2016, approximately 337 million litres of fuel was used with an associated GHG emission of around 864 Gg of CO_2e, which increases to 1158.4 Gg by 2040 in Business as usual (BAU) scenario. Several measures are explored to reduce the fuel consumption in the land transport sector in Fiji.     

Two smart energy management models for the Spanish electricity system

This paper evaluates two smart energy management models for the Spanish electricity system in terms of power consumption savings, CO₂ emissions, and dependence upon primary energy from abroad. We compare a baseline scenario with two alternatives. The first model entails the reduction of the power demand through energy savings measures, smart meters, and self-supply. The second model entails the application of all measures included in first scenario, plus measures oriented to electric vehicles. For each model a sensitivity analysis was performed. Results show that both models can result in reductions of peak loads, CO₂ emissions, and energy dependence.     

Life cycle primary energy use and carbon emission of an eight-storey wood-framed apartment building

In this study the life cycle primary energy use and carbon dioxide (CO₂) emission of an eight-storey wood-framed apartment building are analyzed. All life cycle phases are included, including acquisition and processing of materials, on-site construction, building operation, demolition and materials disposal. The calculated primary energy use includes the entire energy system chains, and carbon flows are tracked including fossil fuel emissions, process emissions, carbon stocks in building materials, and avoided fossil emissions due to biofuel substitution. The results show that building operation uses the largest share of life cycle energy use, becoming increasingly dominant as the life span of the building increases. The type of heating system strongly influences the primary energy use and CO₂ emission; a biomass-based system with cogeneration of district heat and electricity achieves low primary energy use and very low CO₂ emissions. Using biomass residues from the wood products chain to substitute for fossil fuels significantly reduces net CO₂ emission. Excluding household tap water and electricity, a negative life cycle net CO₂ emission can be achieved due to the wood-based construction materials and biomass-based energy supply system. This study shows the importance of using a life cycle perspective when evaluating primary energy and climatic impacts of buildings.     

Effect of green roof on ambient CO2 concentration

Plants can improve air quality by removing pollutants. The air purification capability of plants has been receiving increasing attention because of the rapid deterioration of the environment. However, research on evaluating quantitatively the effect of plants on the environmental pollutant concentrations is still scarce. This paper studies the effect of a green roof on the ambient CO₂ concentration as an example to assess the benefit of urban greening. The study comprises three parts: (1) Field measurement of the difference of CO₂ concentration at a location in the middle of the plants in a small plot of green roof and one in the surrounding area, (2) Experiments to measure the plant’s CO₂ absorption velocity and emission rate using a sealed glass chamber; and (3) Computer simulation of the CO₂ concentration distribution around a green roof using the measured CO₂ absorption velocity and emission rate to quantify the effects of the green roof on the ambient CO₂ concentration.     

The effects of warmth and CO2 concentration,with and without bioeffluents,on the emission of CO2 by occupants and physiological responses

The emission rate of carbon dioxide (CO₂) depends on many factors but mainly on the activity level (metabolic rate) of occupants. In this study, we examined two other factors that may influence the CO₂ emission rate, namely the background CO₂ concentration and the indoor temperature. Six male volunteers sat one by one in a 1.7 m³ chamber for 2.5 h and performed light office-type work under five different conditions with two temperature levels (23 vs. 28°C) and three background concentrations of CO₂ (800 vs. 1400 vs. 3000 ppm). Background CO₂ levels were increased either by dosing CO₂ from a cylinder or by reducing the outdoor air supply rate. Physiological responses to warmth, added CO₂, and bioeffluents were monitored. The rate of CO₂ emission was estimated using a mass-balance equation. The results indicate a higher CO₂ emission rate at the higher temperature, at which the subjects were warm, and a lower emission rate in all conditions in which the background CO₂ concentration increased. Physiological measurements partially explained the present results but more measurements are needed.     

Sustainable energy pathways for land transport in Nigeria

We used a bottom-up optimisation model to explore the energy system implications of five alternative policy pathways for the Nigerian transport sector. Our study considered fuel switching, improved fuel economy, modal shifting, improved logistics, and carbon tax for the period 2010–2050. Results show that the alternative pathways will reduce energy demand and CO₂ emissions significantly. Particularly, we found that improved vehicle fuel economy and a carbon tax can lower Nigeria's CO₂ emissions by 42.8% and 26.9% respectively, in 2050 when compared with the reference case. Additionally, low-carbon pathways will enhance air quality, energy security, and the productive use of energy.     

Climate change impact and risks of concrete infrastructure deterioration

Atmospheric CO₂ is a major cause of reinforcement corrosion in bridges, buildings, wharves, and other concrete infrastructure in Australia, United States, United Kingdom and most other countries. The increase in CO₂ levels associated with global warming will increase the likelihood of carbonation-induced corrosion. Moreover, temperature rises will increase corrosion rates. Clearly, the impact of climate change on existing and new infrastructure is considerable, as corrosion damage is disruptive to society and costly to repair. The paper describes a probabilistic and reliability-based approach that predicts the probability of corrosion initiation and damage (severe cracking) for concrete infrastructure subjected to carbonation and chloride-induced corrosion resulting from elevated CO₂ levels and temperatures. The atmospheric CO₂ concentration and local temperature and relative humidity changes with time over the next 100 years in the Australian cities of Sydney and Darwin are projected based on nine General Circulation Models (GCMs) under (i) high CO₂ emission scenario, (ii) medium CO₂ emission scenario, and (iii) CO₂ emission reduction scenario based on policy intervention. The probabilistic analysis included the uncertainty of CO₂ concentration, deterioration processes, material properties, dimensions, and predictive models. It was found that carbonation-induced damage risks can increase by over 400% over a time period to 2100 for some regions in Australia. Damage risks for chloride-induced corrosion increase by no more than 15% over the same time period due to temperature increase, but without consideration of ocean acidity change in marine exposure. Corrosion loss of reinforcement is not significant. The results were most sensitive to increases in atmospheric CO₂.     

Effect of biodiesel fuel properties and formation of NOx emissions: a review

Biodiesel is revealed as an environmentally friendly alternative fuel for a CI engine and it can palliate regulated and unregulated emissions. Biodiesel is substantially found to reduce the emissions of hydrocarbons, carbon monoxide, and particulate matter, but increasing (10–15%) oxides of nitrogen (NO_x) emissions compared with conventional diesel fuel. The accurate cause for NO_x emission is still vague. This paper reviews the effect of biodiesel properties and formation of NO_x emissions and it is classified in three sections. The first section bestows the NO_x formation mechanisms. The second edition deals with the influence of formation and biodiesel properties on NO_x emissions. Finally, a few prevailing conclusions are epitomised, and more researches are pointed out.     

A novel methodology for estimating space air change rates and occupant CO2 generation rates from measurements in mechanically-ventilated buildings

It is useful to know ventilation rates and carbon dioxide (CO₂) generation rates for evaluating indoor air quality and ventilation efficiency in mechanically-ventilated buildings. A strong limitation of the current models is either they focus solely on a whole building or they are too complicated for practical use in studies of individual spaces. This paper develops a new method for accurately quantifying ventilation rates (i.e. space air change rate) and CO₂ generation rates from measured CO₂ concentrations for individual spaces. The proposed method firstly determined space air change rate using Maximum Likelihood Estimation (MLE). Additionally, a novel coupled-method was initiated for further estimating CO₂ generation rates. Both simulated and experimental data were used to validate the model. Experiments were conducted in a school office by measuring indoor CO₂ concentrations and pressure differences between the return air vent and space. Excellent agreement was obtained. At least 0.998 R² values were obtained for fitting measured CO₂ concentrations when conducting MLE for estimating space air change rate, and the corresponding residual plots showed no pattern and trend. The estimated numbers of occupants were same as the actual ones. Furthermore, the predicted space air change rates showed great consistencies with those from CO₂ equilibrium analysis. The model is simple, handy and effective for practical use. Moreover, the model is also capable for dealing with time-varying space air change rates.     

Study of operational parameters improvement of natural-gas cogeneration plant in public buildings in Thailand

This paper presents two case studies of performance improvement alternatives. The first one is the 52.5 MWe cogeneration plant at the Suvarnabhumi Airport, and the second is the 9.9 MWe cogeneration plant of the government office building complex. Both plants are located in Bangkok. Performance improvements assume changing system design and operational plans during on-peak and off-peak periods with applying chilled water storage for more flexible operation. Such analysis gives opportunity for improvement of plant efficiency, primary energy saving, emission reduction and economical benefits. In case study 1, the selection of new prime mover results in overall efficiency improvement from 48% to 61%, 24% increase of primary energy saving, and 27% improvement of CO₂ emission reduction. Significant amount of primary energy is saved 1451 TJ/a and CO₂ emission reduction is 129,271 tCO₂/a. The profit is increased to 24.80 Million US$/a and the payback period is 4.77 years. In case study 2, the application of chilled water storage leads to maximum profit of 2.63 Million US$/a. The results show that the selection of plant components should be made very carefully in the design stage, as well as that permanent control and optimization of plant operation in the exploitation phase is essential. Economic aspects of cogeneration plants are more sensitive to changeable input parameters than classical separate heat and power generation since cogeneration plants are more complex in the aspects of process configuration and products costs/values (electricity, steam, hot water, and chilled water). Having in mind the future development of the natural gas distribution network in Thailand, it can be estimated that the potential of power generation in public buildings is around 1.3 GWe. Comparing the Thailand total primary energy supply for commercial buildings, it means reduction of about 9.1%.     

Effects of experimental CO2 leakage on solubility and transport of seven trace metals in seawater and sediment

The impact of CO₂ leakage on solubility and distribution of trace metals in seawater and sediment has been studied in lab scale chambers. Seven metals (Al, Cr, Ni, Pb, Cd, Cu, and Zn) were investigated in membrane-filtered seawater samples, and DGT samplers were deployed in water and sediment during the experiment. During the first phase (16 days), “dissolved” (< 0.2 µm) concentrations of all elements increased substantially in the water. The increase in dissolved fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb in the CO₂ seepage chamber was respectively 5.1, 3.8, 4.5, 3.2, 1.4, 2.3 and 1.3 times higher than the dissolved concentrations of these metals in the control. During the second phase of the experiment (10 days) with the same sediment but replenished seawater, the dissolved fractions of Al, Cr, Cd, and Zn were partly removed from the water column in the CO₂ chamber. DNi and DCu still increased but at reduced rates, while DPb increased faster than that was observed during the first phase. DGT-labile fractions (Me_DGT) of all metals increased substantially during the first phase of CO₂ seepage. DGT-labile fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb were respectively 7.9, 2.0, 3.6, 1.7, 2.1, 1.9 and 2.3 times higher in the CO₂ chamber than that of in the control chamber. Al_DGT, Cr_DGT, Ni_DGT, and Pb_DGT continued to increase during the second phase of the experiment. There was no change in Cd_DGT during the second phase, while Cu_DGT and Zn_DGT decreased by 30% and 25%, respectively in the CO₂ chamber. In the sediment pore water, DGT labile fractions of all the seven elements increased substantially in the CO₂ chamber. Our results show that CO₂ leakage affected the solubility, particle reactivity and transformation rates of the studied metals in sediment and at the sediment-water interface. The metal species released due to CO₂ acidification may have sufficiently long residence time in the seawater to affect bioavailability and toxicity of the metals to biota.     

Experimental analysis of DI diesel engine using dual biofuel blended with diesel

ABSTRACT

In recent years, biodiesel has become more attractive as an alternative fuel for diesel engines because of its environmental benefits and the fact is that it is made from renewable resources. The role of biodiesel is not to replace petroleum diesel, biofuels help to improve the economical growth and positive impacts on the environment. The main purpose of this research is to reduce the emission such as carbon monoxide (CO), nitrogen oxides (NO_X), hydrocarbons (HC) and carbon dioxide (CO₂). And to increase the performance characteristics such as break thermal efficiency (BTE), specific fuel consumption (SFC) of diesel engines. Here we used dual biofuel (lemongrass oil plus mint oil) blended with diesel and cerium oxide is added as an additive and undergone the test of engine performance and emission parameters of diesel. The measuring parameters are BTHE, specific fuel conception, CO₂, CO, NO_x and HC.     

Influence of injection timing on engine performance,emission characteristics of Mimusops Elangi methyl ester

ABSTRACT

The improvement in engine performance and exhaust emissions reduction are the major important issues in developing a more efficient engine. The injection timing is one the major parameters that affect the engine performance and emissions for a diesel engine. The present work focused on characterising the in?uence of injection timing on engine performance and exhaust emissions. This has been critically investigated for B20?+?25?ppm (20% Mimusops Elangi methyl ester-80% diesel fuel?+?25?ppm of TiO₂ nanoparticle) additive as alternative fuel. The B20?+25 ppm TiO₂ nanoparticle additive produces more HC and CO emission, but reduce NO_X emission when injection timing is retarded. Advancement in injection timing for B20?+25?ppm TiO₂ nanoparticle additive results in an increase of brake thermal efficiency, decreases brake specific fuel consumption and giving out less HC, CO, smoke emissions but the marginal increase in the NO_X emission.     

A review of bottom-up building stock models for energy consumption in the residential sector

Efficient and rational implementation of building stock CO₂ emission reduction strategies and policies requires the application of comprehensive building stock models that have the ability to: (a) estimate the baseline energy demand of the existing building stock, (b) explore the technical and economic effects of different CO₂ emission reduction strategies over time, including the impact of new technologies, and (c) to identify the effect of emission reduction strategies on indoor environmental quality.     

Effects of carbon dioxide deficiency and metal toxicity on biological oxygen demand

In this study, the effects of carbon dioxide (CO₂) deficiency on the biological growth under respirometric conditions, first‐ and second‐order biological oxygen demand (BOD) progressions using two different BOD measurement techniques and metal toxicity effects on the respirometric BOD are investigated. The effects of CO₂ deficiency in the growth of bacteria and related effects on the first‐ and second‐stage BOD progressions are investigated using various media with respirometers in comparison with the BOD dilution method. CO₂ deficiency causes significant retardations on the growth of bacteria and the second‐stage respirometric BOD values are suppressed. CO₂ seems to be an essential nutrient for the growth of microorganisms and for the oxygen uptake progressing rates. HgCl₂, HgSO₄, CuSO₄, K₂Cr₂O₇, ZnSO4 and Al₂(SO₄)₃ inorganic metal compounds cause significant retardations in the respirometric BOD values obtained from a synthetic autotrophic medium. Effects are found to be dependent on the applied concentrations of these chemicals in the medium.     

Emission characteristics of neat rapeseed oil fuel in diesel engine

Studies show that the combustion of fossil fuel is the main cause of increasing global atmospheric carbon dioxide (CO₂) levels, which is the cause of the greenhouse effect. This has promoted increased research world-wide in a bid to source a greener alternative fuel substitute for conventional fossil fuel. Biofuel appears to be an alternative energy source for diesel engines. Although the combustion of biofuels produces CO₂, the same quantity is absorbed by plants during photosynthesis, hence CO₂ levels are kept in balance. The sulphur content of plant fuels is also low and less than 0.01% by weight compared to 0.05% by weight for diesel fuel. The effect of acid rain is therefore reduced or ameliorated. High viscosity is one of the major problems relating to the direct use of neat vegetable oils as fuels. One method of reducing viscosity is by blending with a low viscosity and volatile fuel. This paper investigates the emission characteristics of neat rapeseed oil and its blend with diesel fuel in a single cylinder unmodified diesel engine. Tests were also conducted on pure diesel fuel so that a comparative assessment could be made. Test results showed reduced hydrocarbon (HC) emissions when running on biofuels. The CO production was higher when running on biofuel at high engine speed and was significantly reduced at low speed operations. The CO₂ emissions were similar for all fuels. The analyses of lubrication oil after the runs on plant fuels showed a net reduction in viscosity.     

Variability in energy and carbon dioxide balances of wood and concrete building materials

A variety of factors affect the energy and CO₂ balances of building materials over their lifecycle. Previous studies have shown that the use of wood for construction generally results in lower energy use and CO₂ emission than does the use of concrete. To determine the uncertainties of this generality, we studied the changes in energy and CO₂ balances caused by variation of key parameters in the manufacture and use of the materials comprising a wood- and a concrete-framed building. Parameters considered were clinker production efficiency, blending of cement, crushing of aggregate, recycling of steel, lumber drying efficiency, material transportation distance, carbon intensity of fossil fuel, recovery of logging, sawmill, construction and demolition residues for biofuel, and growth and exploitation of surplus forest not needed for wood material production. We found the materials of the wood-framed building had lower energy and CO₂ balances than those of the concrete-framed building in all cases but one. Recovery of demolition and wood processing residues for use in place of fossil fuels contributed most significantly to the lower energy and CO₂ balances of wood-framed building materials. We conclude that the use of wood building material instead of concrete, coupled with greater integration of wood by-products into energy systems, would be an effective means of reducing fossil fuel use and net CO₂ emission to the atmosphere.     

Experimental analysis of Deccan hemp oil as a new energy feedstock for compression ignition engine

This study investigates the biodiesel from Deccan hemp oil and its blends for the purpose of fuelling diesel engine. The performance and emission characteristics of Deccan hemp biodiesel are estimated and compared with diesel fuel. The experimental investigations are carried out with different blends of Deccan hemp biodiesel. Results show that brake thermal efficiency is improved significantly by 4.15% with 50 BDH when compared with diesel fuel. The Deccan hemp biodiesel reduces NO_x, HC and CO emission along with a marginal increase in CO₂ and smoke emissions with an increase in the biodiesel proportion in the diesel fuel. The improvement in heat release rates shows an increase in the combustion rate with different percentage blends of Deccan hemp biodiesel. From the engine test results, it has been established that 30–50 BDH of Deccan hemp biodiesel can be substituted for diesel.     

Stochastic hybrid embodied CO2-eq analysis: An application to the Irish apartment building sector

Although embodied CO₂-eq analysis has seen recent developments as evident in the establishment of the ISO 14040 and 14044 LCA standards, it is recognized that due to weaknesses in gathering data on product-related emissions, embodied CO₂-eq values are probabilistic. This paper presents a stochastic analysis of hybrid embodied CO₂-eq in buildings to account for this weakness in traditional methods and, by way of example, applies it to an Irish construction-sector case study. Using seven apartment buildings, 70,000 results are simulated with Monte Carlo analysis and used to derive probabilistic and cumulative embodied CO₂-eq intensity distributions for apartment buildings in Ireland. A Wakeby distribution with known statistical parameters and uncertainty was derived for the average embodied CO₂-eq intensity of apartment building in Ireland. The mean hybrid embodied CO₂-eq (ECO₂-eq) intensity was estimated to be 1636 gCO₂-eq/€ with an uncertainty of 73 gCO₂-eq/€. The stochastic analysis helps to account for variability in input variables into embodied CO₂-eq analysis. The application of the stochastic embodied CO₂-eq analysis as demonstrated in this study can be extended to other building sectors and countries and can form the basis for the development of evidence-based policy formulation since it provides greater information on embodied CO₂-eq intensities of buildings than deterministic approaches.     

Optimisation of performance and emission characteristics of CI engine fuelled with Mahua oil methyl ester–diesel blend using response surface methodology

ABSTRACT

The aim of present study is to optimise the performance and emission characteristics of compression ignition engine fuelled with biodiesel blended diesel fuel using response surface methodology (RSM). During engine trials, two parameters, viz. blend ratio and load torque, were varied and the responses like brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), carbon monoxide (CO), hydrocarbon (HC), nitrogen oxides (NOx) and smoke opacity were investigated. Statistical tool like RSM was used to design experiments. Optimisation of parameters was performed using the desirability approach of RSM for superior performance and lower emission. The results revealed that at optimal input parameters (40% fuel blend and 15?Nm load torque), the values of performance and emission parameters in optimal solutions: BSFC (kg/kWh): 0.2252, BTE (%): 29.2885, CO (vol. %): 0.00757, HC (ppm): 5.7195, NO_x (ppm): 319.78, smoke (vol. %): 4.50 were found for the Mahua oil methyl esters blended with diesel.