Wind turbine availability: Should it be time or energy based? – A case study in Ireland

This paper describes a method for quantifying wind farm availability using two different approaches and comparing the results. Wind turbine suppliers regularly guarantee turbine availability in terms of time. A typical value of 97% is generally taken as the industry standard. This paper shows that this guarantee can potentially under-compensate the wind farm operator for losses sustained depending on when the period of non-availability occurs. Here we present an alternative method to quantify wind farm availability based on energy, which relates the energy losses in an Irish wind farm in 2007 to periods of turbine non-availability. It is shown in this analysis completed at this operational wind farm that while the technical non-availability as a percentage of time is 3%, the percentage of energy lost during downtimes is actually 11%. Based on the financial analysis above, the financial losses are significant. To answer the question should wind turbine availability be time or energy based, this paper shows that it can be advantageous for wind turbine owners to have energy-based calculations as long as the developers have sufficient monitoring of not only wind speed but also SCADA data.     

Which is the preferable transport fuel on a greenhouse gas basis; biomethane or ethanol?

Biomethane and ethanol are both biofuels which are generated from agricultural crops that can be utilised to meet the Biofuels Directive. In Ireland with the demise of the sugar industry 48,000 Ha of land is readily available for biofuel production, without unduly effecting food production. Which biofuel should dominate? This paper investigates biofuel production for three different crop rotations: wheat, barley and sugar beet; wheat, wheat and sugar beet; wheat only. A greenhouse gas balance is performed to determine under what conditions each biofuel is preferable. For both biofuels, the preferred crop on a weight basis is wheat, while on an area basis the preferred crop is sugar beet. Biomethane scenarios produce more gross energy than ethanol scenarios. Under the base assumption (7.41% biogas losses, and biomethane utilised in a converted petrol engine, such as a bi-fuel car, and thus underperforming on a km/MJ basis) ethanol generated more net greenhouse gas savings than biomethane. This was unexpected as biomethane produces twice the net energy per hectare as ethanol. If either biogas losses were reduced or biomethane was utilised in a vehicular engine optimised for biomethane (such as a bus powered solely on gaseous biofuel) then biomethane would generate significantly more net greenhouse gas savings than ethanol. It was found that if biogas losses were eliminated and the biomethane was used in a vehicle optimised for biomethane, then the net greenhouse gas savings are 2.4 times greater than those from ethanol generated from the same feedstock.     

Steam reforming of ethanol into hydrogen-rich gas using microwave Ar/water “tornado” – Type plasma

Microwave plasma steam reforming of ethanol under vortex gas flow and atmospheric pressure conditions has been investigated. The main gas products of the steam reforming are H₂ and CO as detected by mass spectrometry and Fourier transform infrared spectroscopy. A “black” carbon deposit on the wall has been observed. A previously developed theoretical model for ethanol decomposition accounting for the gas thermal balance and the chemical kinetics has been further extended to account for the addition of steam to the argon/ethanol feeding background gas. The mechanisms of ethanol and water decomposition depend on the ethanol/steam ratio, and several hydrogen production regimes have been identified and discussed. An integral reaction scheme for ethanol/water decomposition is suggested.     

Solar XXI building: Proof of concept or a concept to be proved?

Solar XXI building is a low energy office building where passive and active solar strategies have been applied to reduce the use of energy for heating, cooling and lighting, combining also an extensive photovoltaic façade for electricity production. Solar XXI opened in 2006 and is considered a high efficient building, close to a net zero energy building (NZEB), where the difference between the energy consumed and that produced is 1/10^th of the energy consumed by a Portuguese standard new office building. Its design includes many energy efficiency concepts, such as a high insulated envelope, south sun exposure, windows external shading, photovoltaic panels heat recovery, ground-cooling system, daylighting, stack effect and cross ventilation. The solar gains of the windows and the effectiveness of shading devices were evaluated in order to correlate solar radiation, external and indoor air temperatures. It was also verified that amplitude-dampening of ground-cooled air ranged between 5 and 8 °C, following the trend of the analytical solution for heat diffusion of a cylindrical air/soil heat-exchanger.     

Can hydrogen or natural gas be alternatives for aviation? – A life cycle assessment

Between 1989 and 2011 the aviation traffic has been growing 4.6% per year. The increase on aviation traffic had consequences in terms of greenhouse gases (GHGs) and local pollutant emissions (e.g. carbon monoxide – CO, hydrocarbons – HC, nitrogen oxides – NO_x). In order to minimize this problem, the evaluation of sustainable alternatives to current fuel (jet fuel A) has been discussed but their impact on emissions is still unclear. The main research goals of this paper are: (i) to evaluate if the well-to-wake energy consumption in aviation can be reduced with alternative fuels as liquid natural gas (LNG) and/or liquid hydrogen (LH₂) and (ii) to assess if alternative fuels can be used in aviation to minimize carbon dioxide emissions and local pollutants.     

Renewable energy carriers: Hydrogen or liquid air/nitrogen?

The world’s energy demand is met mainly by the fossil fuels today. The use of such fuels, however, causes serious environmental issues, including global warming, ozone layer depletion and acid rains. A sustainable solution to the issues is to replace the fossil fuels with renewable ones. Implementing such a solution, however, requires overcoming a number of technological barriers including low energy density, intermittent supply and mobility of the renewable energy sources. A potential approach to overcoming these barriers is to use an appropriate energy carrier, which can store, transport and distribute energy. The work to be reported in this paper aims to assess and compare a chemical energy carrier, hydrogen, with a physical energy carrier, liquid air/nitrogen, and discuss potential applications of the physical carrier. The ocean energy is used as an example of the renewable energy sources in the work. The assessment and comparison are carried out in terms of the overall efficiency, including production, storage/transportation and energy extraction. The environmental impact, waste heat recovery and safety issues are also considered. It is found that the physical energy carrier may be a better alternative to the chemical energy carrier under some circumstances, particularly when there are waste heat sources.     

Should we educate the public about exergy?

The author explains his views that the public is often confused when it discusses energy, and needs to be better educated about exergy if energy issues and problems are to be addressed appropriately.     

V2G or VEG?An investigation into the business model for future electric vehicles based on technological developments

基于目前电动汽车产业发展的困境认识,提出未来电动汽车技术发展与商业实现的VEG模式(Vehicle-Energy station-Grid).在VEG模式中,电动汽车充电方式由用户自己选择,可以在能量站快充,也可以在停车场或家庭车库进行慢充.能量站安装有低成本,长寿命的MW级储能电池,能够从电网充电储存电量后给电动汽车快速充电;同时,能量站能够与电网互动,用于电力调峰或调频.作者认为,开发低成本长寿命的新型储能电池和可以安全快速充电的新型动力电池是实现VEG模式的两大技术关键.只有这两大技术关键突破后,纯电动汽车产业发展的春天才能够真正到来.     

Mitigating ethanol crossover in DEFC: A composite anode with a thin layer of Pt50–Sn50 nanoparticles directly deposited into Nafion membrane surface

A composite anode comprising an outer and an inner catalyst layer is proposed to 1) suppress the ethanol crossover in direct ethanol fuel cell (DEFC), and 2) improve the cell performance as well as the utilization efficiency of ethanol fuel. The inner catalyst layer contains a thin layer of Pt₅₀–Sn₅₀ nanoparticles directly deposited on the Nafion® membrane surface through impregnation-reduction (IR) method, and acts as the reactive ethanol filter. In this paper, several aspects of the research are reported. First, the mitigation of ethanol crossover and the performance of membrane electrode assembly (MEA) of the proposed structure are compared to those with normal structure. Next, a candidate mechanism of the mitigation of ethanol crossover and the improvement of MEA performance is investigated. Third, SEM, X-ray, EDS and EPMA analysis are used to characterize microstructures, phases, chemical composition and distributions of the obtained Pt₅₀–Sn₅₀ layer. Finally, the ethanol crossover rate in a DEFC is determined through measuring the CO₂ concentration at the cathode exhaust in real time. Experimental results demonstrate that the composite anode with an inner layer of Pt₅₀–Sn₅₀ nano-catalyst particles on Nafion membrane surface suppresses ethanol crossover up to 17% more than the anode without the inner layer, and yield a 6% better MEA performance than the normal-MEA. The inner Pt₅₀–Sn₅₀ catalyst layer serves both as an ethanol filter and an electrode. Its dual-role contributes to the suppression of ethanol crossover, and improvement of both cell performance and the utilization efficiency of ethanol fuel, both of which are dependent on the catalyst activity of the ethanol electro-oxidation over the thin catalyst layer directly deposited on Nafion membrane surface.     

Local ownership of ethanol plants: What are the effects on communities?

The rapid expansion of ethanol plants across the U.S. state of Iowa has fueled debate about the burdens and benefits of local (in-state investors) versus non-local ownership of biorefineries. Central to these concerns is the extent to which non-local, absentee owners might reap the benefits of the ethanol industry at the expense of local communities. A key argument within the rural development literature is that local ownership of firms has a positive effect on the long-term well-being and sustainability of the communities in which they are situated. This literature asserts that firms operate at different scales, with local firms embedded within local supply chains and institutions, and non-local firms embedded within national and international networks and institutions. Conversely, there is a growing body of work within the alternative agrifood systems literature that cautions against the ‘local trap’; the assumption that the local scale is inherently good and therefore advantageous. Despite this broader debate, the literature on local ownership and renewable energy remains limited. This paper addresses this gap by drawing on case study research of the community effects of ethanol plant ownership structure from the perspective of community leaders. My findings suggest that differences between the structure and effects of local versus non-local ownership of firms on communities are rather more ambiguous than the literature asserts. Therefore, assumptions about the benefits of local ownership may be overstated and concepts of ‘local’ and ‘non-local’ may be inadequate for considering firm outcomes on the civic welfare and socioeconomic well-being of a community.     

Autothermal reforming of ethanol in a Pd–Ag/Ni composite membrane reactor

The main objective of this project is to study the hydrogen production reaction from oxidative steam reforming of bio-ethanol in the pertinent characteristics of a palladium–silver alloy membrane reactor. The enhancements of hydrogen permeation and of H₂/N₂ permselectivity were studied in a Ni–Pd–Ag ternary alloy membrane, which was fabricated by successive electroless plating of palladium and silver on stainless steel (PSS) supports modified with nickel electroplating. XRD, SEM, and EDS were used to characterize the surface morphology of the membranes. Ethanol–water mixture (n_water/n_ethanol = 1 or 3) and oxygen (n_oxygen/n_ethanol = 0.2 or 0.7) were fed concurrently into the membrane reactor packed with Zn–Cu commercial catalyst (MDC-3). The reaction temperatures were set at temperatures of 593–723 K and pressures of 3–10 atm. The amount of oxygen added in the feed has a significant effect on the steam reforming reaction of ethanol. At high pressures, autothermal reaction of ethanol with no need for external heating to the composite membrane reactor to produce high purity hydrogen was easily processed.     

Should a vehicle fuel economy standard be combined with an economy-wide greenhouse gas emissions constraint? Implications for energy and climate policy in the United States

The United States has adopted fuel economy standards that require increases in the on-road efficiency of new passenger vehicles, with the goal of reducing petroleum use and (more recently) greenhouse gas (GHG) emissions. Understanding the cost and effectiveness of fuel economy standards, alone and in combination with economy-wide policies that constrain GHG emissions, is essential to inform coordinated design of future climate and energy policy. We use a computable general equilibrium model, the MIT Emissions Prediction and Policy Analysis (EPPA) model, to investigate the effect of combining a fuel economy standard with an economy-wide GHG emissions constraint in the United States. First, a fuel economy standard is shown to be at least six to fourteen times less cost effective than a price instrument (fuel tax) when targeting an identical reduction in cumulative gasoline use. Second, when combined with a cap-and-trade (CAT) policy, a binding fuel economy standard increases the cost of meeting the GHG emissions constraint by forcing expensive reductions in passenger vehicle gasoline use, displacing more cost-effective abatement opportunities. Third, the impact of adding a fuel economy standard to the CAT policy depends on the availability and cost of abatement opportunities in transport—if advanced biofuels provide a cost-competitive, low carbon alternative to gasoline, the fuel economy standard does not bind and the use of low carbon fuels in passenger vehicles makes a significantly larger contribution to GHG emissions abatement relative to the case when biofuels are not available. This analysis underscores the potentially large costs of a fuel economy standard relative to alternative policies aimed at reducing petroleum use and GHG emissions. It further emphasizes the need to consider sensitivity to vehicle technology and alternative fuel availability and costs as well as economy-wide responses when forecasting the energy, environmental, and economic outcomes of policy combinations.     

Investigation into hydrolysis and alcoholysis of sodium borohydride in ethanol–water solutions in the presence of supported Co–Ce–B catalyst

The efficacies of attapulgite clay (ATC)-, titanium dioxide (TiO₂)- and silica gel (SG)-supported cobalt–cerium–boron (Co–Ce–B) substances as catalysts were investigated for the alcoholysis and hydrolysis of sodium borohydride (NaBH₄) in ethanol–water solutions. Ce served as a helpful co-catalyst among the prepared Co–Ce–B catalysts, and the catalytic activity decreased in the following sequence: TiO₂-supported > ATC-supported > SG-supported > unsupported. The effects of Ce/(Co+Ce) molar ratio, ethanol concentration, reaction temperature, NaBH₄ concentration and NaOH concentration on the hydrogen production rate were investigated. For the ATC-supported catalyst, when the Ce/(Co+Ce) molar ratio was 10%, the catalyst exhibited the best catalytic activity. Optimal NaBH₄ concentration, NaOH concentration and ethanol concentration to promote hydrogen generation rate was around 8 wt.%, 15 wt.% and 30 wt.%, respectively. It can be found that the addition of ATC greatly improved the recycle ability of the catalysts in the multi-cycle tests. The surface morphology of the catalysts before and after the recycle tests was studied from SEM images. The compositions of the catalysts were determined by XRD and EDS analyses. The occurrence of NaB(OH)₄ in the alcoholysis by-product provided pertinent indications of ethanol recovery after the tests. The value of activation energy in the hydrogen generation process in the presence of ATC-supported Co–Ce–B catalyst was calculated to be 29.51 kJ/mol. An overall kinetic equation was also proposed.     

Should the US clean air act include CO2 emission control?: Examination by data envelopment analysis

This study proposes a new use of Data Envelopment Analysis (DEA) to measure the operational, environmental and both-unified efficiency measures of US coal-fired power plants. The power plants produce not only desirable outputs (e.g., electricity) but also undesirable outputs (e.g., CO₂ and NO_x) as a result of their plant operations. A Range-Adjusted Measure (RAM) is used as an original non-radial DEA model. Then, it is reformulated for handling undesirable (bad) outputs. The proposed use of DEA models measures the environmental and unified performance of power plants under two variable alternatives (with and without CO₂ emission control) in order to examine both the influence of US Clean Air Act (CAA) on the acid rain causing gases (NO_x and SO₂) and its extension to the CO₂ regulation. This study finds that the acid rain program under the CAA has been effective on the emission control of SO₂ and NO_x produced at US coal-fired power plants. Moreover, additional regulation on CO₂ may enhance their environmental and unified performance. Thus, it is recommended that the US federal and state governments need to expand the legal scope of CAA to the emission control on CO₂ because the gas is considered as a main source of global warming and climate change.     

Transforming shortcomings into opportunities: Can market incentives solve Lebanon's energy crisis?

Over the past decades Lebanon's energy sector has been largely ignored and this has led to high economic and environmental costs. The sector is characterized by electricity poverty, an expanding and mainly unregulated transport sector and a lack of energy savings spanning through all sectors of the economy. Recently, the Government of Lebanon has committed to increase the share of renewable energy to 10% of the total energy supply by 2013 and to 12% by the year 2020; it also aims at reducing energy consumption by 6% by the year 2013. This paper aims at contributing to the formulation of a more comprehensive energy strategy for Lebanon by analyzing the recent changes in policy direction and by recommending legal, regulatory and policy measures in order to transform current shortcomings into opportunities allowing the country to become a regional ‘success story’ in the deployment of renewable energy and energy efficiency.     

Should policy-makers allocate funding to vehicle electrification or end-use energy efficiency as a strategy for climate change mitigation and energy reductions? Rethinking electric utilities efficiency programs

In order to reduce greenhouse gas emissions in the United States by an order of magnitude, a portfolio of mitigation strategies is needed. Currently, many utilities pursue energy efficiency programs. We study a case where utilities could choose whether to allocate their energy efficiency budget to either end-use efficiency or vehicle electrification as a means to reduce CO₂ emissions. We build a decision space that displays the conditions under which utilities should pursue either strategy. To build such decision space, assumptions are needed on how consumers respond to electric vehicle incentives, and what would be the baseline vehicle selected by consumers if no incentives were in place. Since these two aspects are highly uncertain, we treat them parametrically: if consumers are replacing a conventional vehicle with a PHEV, utility incentive programs to induce PHEV adoption appear to be cost-effective for a wide range of efficiency program costs and grid emissions factors.     

What crop rotation will provide optimal first-generation ethanol production in Ireland, from technical and economic perspectives?

This paper describes a technical and economic analysis of the potential ethanol production from wheat, barley and sugar beet in Ireland for three different combinations of the crops. Scenarios are investigated which include for three crop rotations: (1) wheat, barley and sugar beet; (2) wheat, wheat and sugar beet; and (3) wheat only.Ethanol production facilities typically employ either starch or sugar feedstocks which may not be optimised if both starch and sugar feedstocks are used. Thus, the scenarios which include sugar beet require two separate facilities.The study shows that technical optimisation gives a different rotation to an economic optimisation. It was found that the starch feedstocks (wheat and barley) produce more ethanol per tonne of feedstock than the sugar feedstock (sugar beet). However, on a land area basis, sugar beet produces significantly more ethanol, and hence more energy, than either wheat or barley. In order to meet the EU Biofuels Directive, it is crucial to maximise the energy return per unit of land. Thus, optimisation on the basis of minimisation of land take gives a rotation of wheat, wheat and sugar beet, as this scenario produces the greatest quantity of energy per hectare, whereas optimisation on an economic basis suggests wheat alone with the lowest production cost of €0.6/l.     

Do energy prices stimulate food price volatility? Examining volatility transmission between US oil,ethanol and corn markets

This paper examines volatility transmission in oil, ethanol and corn prices in the United States between 1997 and 2011. We follow a multivariate GARCH approach to evaluate the level of interdependence and the dynamics of volatility across these markets. The estimation results indicate a higher interaction between ethanol and corn markets in recent years, particularly after 2006 when ethanol became the sole alternative oxygenate for gasoline. We only observe, however, significant volatility spillovers from corn to ethanol prices but not the converse. We also do not find major cross-volatility effects from oil to corn markets. The results do not provide evidence of volatility in energy markets stimulating price volatility in the US corn market.     

Low-quality or high-quality coal? Household energy choice in rural Beijing

Household low-quality coal consumption contributes to severe haze pollution in China. In response, subsidy policies on high-quality coal consumption and the adoption of new-type coal stoves have been implemented. Using survey data in rural Beijing, this paper characterizes the determinants of coal consumption and switching behavior between low-quality and high-quality coals. To this end, we apply bivariate probit regression and Tobit regression to evaluate the effectiveness of government policies and the influence of cognitive & psychological and socioeconomic factors on coal consumption behaviors. Our empirical results reveal that prosociality and local environmental concern play crucial roles in household choices and consumption behaviors between two types of coals, but global environmental concern does not. The promotion of new-type coal stoves significantly facilitates the transition from low-quality to high-quality coal, while price subsidies on high-quality coal do not influence market acceptance of high-quality coal. These results demonstrate the importance of cognitive & psychological factors and promotion policies on coal consumption behavior. Overall, we suggest that an education campaign or program regarding local environmental awareness, prosocial values and behaviors and on new-type coal stoves should be further promoted to accelerate the transition from low-quality to high-quality coal.