The boiler concept for combustion of large soya straw bales

In one of the largest agricultural companies in Serbia, with over 2000 ha of soya plantations, there are 4000 t/year of baled soya straw produced. Soya straw biomass is planned to be used as a renewable energy source for heating the greenhouses, with 5 ha in area. Therefore, efforts have been made to develop a technology for utilizing large bales of soya straw for energy production. In the first phase, a demo energy production facility-furnace was developed and built. The facility had been tested in order to examine the quality of combustion of large soya straw bales. Since experimental results of testing of this facility have proved to be very satisfactory, in the second phase of the development, a hot water boiler of similar characteristics (burning soya straw bales, with dimensions 0.7×1.2×2.7 m³) has been designed.     

Economic feasibility assessment of rice straw utilization for electricity generating through combustion in Thailand

The economic feasibility of biomass based combustion projects of various capacities to generate electricity from rice straw is evaluated for Thailand. For an assumed lifespan of 20 years, rice straw-fueled combustion facilities would generate Net Present Values (NPV) of −3.15, 0.94, 2.96, 9.33, and 18.79 million USD for projected 5, 8, 10, 15, and 20 MW_e plants, respectively. Examining the effects of scale on the cost of generated electricity (COE) over the considered range of capacities indicates that COE varies from 0.0676 USD/kWh at 20 MW_e to 0.0899 USD/kWh at 5 MW_e. By scaling up the power plants, the variations of the financial parameters, namely NPV values, become less sensitive to the critical variables. As an example, if the fuel price, selling price of electricity, and the plant factor change by +36% (31.0 USD/t), −16% (0.0758 USD/kWh), and −14% (5650 h/yr), respectively, the largest scale project is still appealing for investment. Nevertheless, to ensure a secure fuel supply, smaller scale power plants, i.e., 8 and 10 MW_e may be more practicable. A further sensitivity analysis is discussed in terms of the financial feasibility of the projects (i.e., NPV ? 0), and the investment appraisal condition (here, Internal Rate of Return or IRR ? 11%).     

SHAM—a simulation model for designing straw fuel delivery systems. Part 2: model applications

A dynamic simulation model for designing straw fuel delivery systems, called SHAM (Straw HAndling Model), has been used to evaluate the performance, costs and energy needs of various straw handling systems. The prerequisites of straw harvest were investigated for three Swedish regions with different climatic and geographical conditions. As a fuel in district heating plants, the simulations showed that straw has the best opportunity of becoming economically competitive in agricultural districts in south Sweden. The simulations demonstrated, however, that the costs can be lowered and the system performance increased for these places by using appropriate management strategies. SHAM was also used to determine the number of machines in the handling operations in order to minimize the total fuel costs for a straw- and oil-fired district heating plant. The optimizations showed that straw can be delivered to the plant at a cost of 29.9 SEK GJ⁻¹. Finally, two alternatives to the conventional high-density baler systems were evaluated; systems based on compact rolls and systems based on chopped straw stored outdoors. It was demonstrated that these technologies cost about 5–20% more compared with high-density bales. However, their prospects of becoming competitive harvest methods for the future are good.     

Thermo-economic optimization of an indirectly coupled solid oxide fuel cell/gas turbine hybrid power plant

Power generation using gas turbine (GT) power plants operating on the Brayton cycle suffers from low efficiencies, resulting in poor fuel to power conversion. A solid oxide fuel cell (SOFC) is proposed for integration into a 10-MW GT power plant, operating at 30% efficiency, in order to improve system efficiencies and economics. The SOFC system is indirectly coupled to the GT, in order to minimize the disruption to the GT operation. A thermo-economic model is developed to simulate the hybrid power plant and to optimize its performance using the method of Lagrange Multipliers. It predicts an optimized power output of 18.9 MW at 48.5% efficiency, and a breakeven per-unit energy cost of USD 4.54 ¢ kW h⁻¹ for the hybrid system based on futuristic mass generation SOFC costs.     

Thermo-economic modeling of an indirectly coupled solid oxide fuel cell/gas turbine hybrid power plant

Power generation using gas turbine (GT) power plants operating on the Brayton cycle suffers from low efficiencies, resulting in poor fuel to power conversion. A solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency, in order to improve system efficiencies and economics. The SOFC system is indirectly coupled to the gas turbine power plant, paying careful attention to minimize the disruption to the GT operation. A thermo-economic model is developed for the hybrid power plant, and predicts an optimized power output of 20.6 MW at 49.9% efficiency. The model also predicts a break-even per-unit energy cost of USD 4.65 ¢ kWh⁻¹ for the hybrid system based on futuristic mass generation SOFC costs. This shows that SOFCs may be indirectly integrated into existing GT power systems to improve their thermodynamic and economic performance.     

Geographic distribution of economic potential of agricultural and forest biomass residual for energy use: Case study Croatia

This paper provides methodology for regional analysis of biomass energy potential and for assessing the cost of the biomass at the power plant (PP) location considering transport distance, transport costs and size of the power plants. Also, methodology for determination of an upper-level price of the biomass which energy plant can pay to the external suppliers has been proposed. The methodology was applied on the case of Croatia and energy potential of biomass in the Croatian counties was calculated, using different methodologies, for wheat straw, corn stover and forestry residues, types of biomass considered economically viable at the moment. Results indicate that the average energy potential of wheat straw is 8.5 PJ, corn stover 7.2 PJ and forestry residues 5.9 PJ.     

Thermo-economic modeling of a solid oxide fuel cell/gas turbine power plant with semi-direct coupling and anode recycling

Power generation using gas turbine (GT) power plants operating on the Brayton cycle suffers from low efficiencies, resulting in poor fuel to power conversion. A solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency in order to improve system efficiencies and economics. The SOFC system is semi-directly coupled to the gas turbine power plant, with careful attention paid to minimize the disruption to the GT operation. A thermo-economic model is developed for the hybrid power plant, and predicts an optimized power output of 21.6 MW at 49.2% efficiency. The model also predicts a breakeven per-unit energy cost of USD 4.70 ¢/kWh for the hybrid system based on futuristic mass generation SOFC costs. Results show that SOFCs can be semi-directly integrated into existing GT power systems to improve their thermodynamic and economic performance.     

Passive direct methanol fuel cells for portable electronic devices

Due to the increasing demand for electricity, clean, renewable energy resources must be developed. Thus, the objective of the present study was to develop a passive direct methanol fuel cell (DMFC) for portable electronic devices. The power output of six dual DMFCs connected in series with an active area of 4 cm² was approximately 600 mW, and the power density of the DMFCs was 25 mW cm⁻². The DMFCs were evaluated as a power source for mobile phone chargers and media players. The results indicated that the open circuit voltage of the DMFC was between 6.0 V and 6.5 V, and the voltage under operating conditions was 4.0 V. The fuel cell was tested on a variety of cell phone chargers, media players and PDAs. The cost of energy consumption by the proposed DMFC was estimated to be USD 20 W⁻¹, and the cost of methanol is USD 4 kW h. Alternatively, the local conventional electricity tariff is USD 2 kW h. However, for the large-scale production of electronic devices, the cost of methanol will be significantly lower. Moreover, the electricity tariff is expected to increase due to the constraints of fossil fuel resources and pollution. As a result, DMFCs will become competitive with conventional power sources.     

Forest biomass supply logistics for a power plant using the discrete-event simulation approach

This study investigates the logistics of supplying forest biomass to a potential power plant. Due to the complexities in such a supply logistics system, a simulation model based on the framework of Integrated Biomass Supply Analysis and Logistics (IBSAL) is developed in this study to evaluate the cost of delivered forest biomass, the equilibrium moisture content, and carbon emissions from the logistics operations. The model is applied to a proposed case of 300 MW power plant in Quesnel, BC, Canada. The results show that the biomass demand of the power plant would not be met every year. The weighted average cost of delivered biomass to the gate of the power plant is about C$ 90 per dry tonne. Estimates of equilibrium moisture content of delivered biomass and CO₂ emissions resulted from the processes are also provided.     

An assessment model for collecting and transporting cellulosic biomass

Feedstock supply is one of the key obstacles for cost-effective production of cellulosic biofuels. This paper proposes an assessment model to study the feedstock costs, energy consumption, and CO₂ emissions associated with collecting and transporting cellulosic biomass from farm to storage sites. To illustrate the utility of the proposed model, four logistics options for collecting and transporting corn stover are studied: (A) round bales via tractor, (B) rectangular bales via tractor, (C) round bales via tractor (on-farm) and truck (road), and (D) rectangular bales via tractor and truck. Results show that option A is the lowest-cost option when storage capacity is less than 110,000 ton. For larger storage capacity, option D is more cost-effective. In terms of energy consumption and CO₂ emissions, option A consumes the least energy and generates the least CO₂ emissions when storage capacity is less than 45,000 ton. For larger storage capacity, option D performs better.     

Biomethanol production from gasification of non-woody plant in South Africa: Optimum scale and economic performance

Methanol production from biomass is a promising carbon neutral fuel, well suited for use in fuel cell vehicles (FCVs), as transportation fuel and as chemical building block. The concept used in this study incorporates an innovative Absorption Enhanced Reforming (AER) gasification process, which enables an efficient conversion of biomass into a hydrogen-rich gas (syngas) and then, uses the Mitsubishi methanol converter (superconverter) for methanol synthesis. Technical and economic prospects for production of methanol have been evaluated. The methanol plants described have a biomass input between 10 and 2000 MW_th. The economy of the methanol production plants is very dependent on the production capacity and large-scale facilities are required to benefit from economies of scale. However, large-scale plants are likely to have higher transportation costs per unit biomass transported as a result of longer transportation distances. Analyses show that lower unit investment costs accompanying increased production scale outweighs the cost for transporting larger quantities of biomass. The unit cost of methanol production mostly depends on the capital investments. The total unit cost of methanol is found to decrease from about 10.66 R/l for a 10 MW_th to about 6.44 R/l for a 60 MW_th and 3.95 R/l for a 400 MW_th methanol plant. The unit costs stabilise (a near flat profile was observed) for plant sizes between 400 and 2000 MW_th, but the unit cost do however continue to decrease to about 2.89 R/l for a 2000 MW_th plant. Long term cost reduction mainly resides in technological learning and large-scale production. Therefore, technology development towards large-scale technology that takes into account sustainable biomass production could be a better choice due to economic reasons.     

The net cost of biofuels in Thailand—An economic analysis

Biofuels are expected to represent a growing portion of liquid fuel consumption in Thailand due to environmental and social considerations in conjunction with policy goals supporting their domestic production and consumption. This paper reviews the economic costs associated with biofuel policy implementation in Thailand in the short term target year of 2011. Internal (production) and external (environmental, social, etc.) costs and benefits are evaluated, and, where possible, monetized. Domestic production of biofuel is calculated to be 9.5 billion THB (317 million USD) more expensive than importing the equivalent amount of petroleum. The environmental benefits from GHG savings as well as losses due to increased ground level ozone formation and government expenditure to support the biofuel industry yield a total “net cost” of 8.6 billion THB or 121 THB (4.04 USD) per capita for the year 2011. This result is contextualized with the (non-monetized) consideration that although biofuels are somewhat more expensive in the short term, their domestic production allows virtually all of the money to stay within the Thai economy as opposed to being sent abroad. This fact, coupled with significant uncertainty in future petroleum prices, could strongly influence the direction of Thai policy with respect to biofuels.     

The economic effects of energetic exploitation of straw in Vojvodina

The autonomous province of Vojvodina is an autonomous province in the Republic of Serbia. It is located in the northern part of the country, in the Pannonia plain. Vojvodina is an energy-deficient province.Assessment of the effects of energetic use wheat straw is performed for certain types of systems for storing straw and straw stored specifically in the form of small square bales, and especially for the cylinder-shaped straw bales. The method of evaluation of economic effects is based on the total cost of collecting, transportation, handling and storing, with corrections for the difference in the cost of the energy conversion and combustion.With comparison of the costs of energy production from baled straw to the costs of energy production from hard coal, it was found that the energy obtained from the straw from own farm is cheaper than energy from hard coal by 28%, in the case of the using small square bales and by 34% in the case of the using cylinder-shaped bales. Through sensitivity analysis it was concluded that the two systems of collecting straw, economically, are relatively resistant to changes in prices of the most important inputs. However, there is a relatively high sensitivity to changes in performances of machines with a larger percentage increase of costs for the system with cylinder-shaped bales. However, this system is generally more resistant to changes of influencing factors due to lower basic costs per ton of the pretreated straw. Differential costs analysis, i.e., the development of differential calculations, shows that the energy from straw in the form of small square bales is cheaper than the energy from hard coal by 51%, while the energy from the straw in the form cylinder-shaped bales is cheaper by 60%.     

Fuel cell systems for transportation: Status and trends

The U.S. program for the development of direct hydrogen-fueled automotive fuel cell systems has established ambitious performance and cost targets for the 2010 and 2015 time frames. These targets include peak and rated power efficiencies of 60% and 50%, respectively, specific power and power densities of 650 We kg⁻¹ and 650 We L⁻¹, and manufactured costs of $45 and 30 kWe⁻¹ for 80 kWe⁻¹ net systems in the 2010 and 2015 systems, respectively. In this paper, we discuss the use of fuel cell system models to examine the performance and projected manufactured costs of 2005 systems and the improvements needed to meet the 2010 and 2015 system level targets. It appears possible to meet most of the 2010 performance targets with advances such as the nano-structured thin film electrocatalysts and a modified electrolyte membrane capable of operating at up to 95 °C, at least for short periods. To meet the 2015 targets, however, the fuel cell systems may need to operate without pressurization at higher temperatures of up to 120 °C without the need to humidify the fuel gas and air, along with several other improvements in stack and balance-of-plant components. Our simulations provide quantitative estimates of the various performance and cost parameters of the near-term and the advanced systems that can achieve the targets set for automotive fuel cell system development.     

Potential of practical implementation of rice straw-based power generation in Thailand

This paper uses life cycle assessment to evaluate the potential of rice straw power plant implementation in Thailand in terms of GHG emission savings from avoided open burning and from implementing rice straw power production, which can substitute that from natural gas. Annually, 8.5–14.3 Mt rice straw burning contributes 5.0–8.6 MtCO₂-eq which could be converted to 786–1325 MW of power, yielding a total greenhouse gas (GHG) reduction of 7.8–13.2 MtCO₂-eq. Moreover, 1090–1837 Mm³ of natural gas could be substituted annually. A total of 25 provinces in central Thailand have potential to generate electricity with a total capacity of 210–292 MW (plant efficiency 20–27%), resulting in an annual GHG emission savings of 2.3–2.6 MtCO₂-eq, and with a provincial capacity of over 20 MW in 6 provinces, 10–20 MW in 7 provinces, 1–10 MW in 6 provinces and less than 1 MW in 6 provinces.     

Microbial changes during the on-farm storage of canola (oilseed rape) straw bales and pellets

The effect of on-farm storage on microbial growth on baled and pelletised Brassica napus (oilseed rape/canola) straw was investigated. Canola straw collected in 2008 and 2009 was stored baled in an open shed for 3, 4, 7, 10 and 20 months in 2008 and for 1 and 3 months in 2009. Pellets were produced from straw stored for 3, 7, and 10 months in 2008 and straw stored for 3 months in 2009, and stored for up to 48 weeks.The moisture content (MC), water activity (a_w), bacterial and fungal colony-forming units (CFU), and carbon-to-nitrogen ratio (C:N) of canola straw bales and pellets were measured during storage. In addition, temporal environmental conditions (ambient temperature and relative humidity) and bale temperature were monitored. The moisture content showed a tendency to stabilise during storage, with an equilibrium moisture content of approximately 155 g kg⁻¹ total weight for straw bales and 110 g kg⁻¹ total weight for straw pellets. Consequently, the water activity of canola straw bales remained below 0.8 and that of pellets below 0.66 during storage, providing an explanation for relatively low microbial growth. The number of bacterial and fungal CFU present in the straw bales and pellets followed the trend of ambient relative humidity and no correlation was found with the C:N ratio of the biomass. Canola straw pellets were considered a superior combustion fuel to straw bales due to lower moisture content and less microbial deterioration during storage.     

Highly efficient electricity generation from biomass by integration and hybridization with combined cycle gas turbine (CCGT) plants for natural gas

Integration/co-firing with existing fossil fuel plants could give near term highly efficient and low cost power production from biomass. This paper presents a techno-economical analysis on options for integrating biomass thermal conversion (optimized for local resources ∼50 MW_th) with existing CCGT (combined cycle gas turbine) power plants (800–1400 MW_th). Options include hybrid combined cycles (HCC), indirect gasification of biomass and simple cycle biomass steam plants which are simulated using the software Ebsilon Professional and Aspen Plus. Levelized cost of electricity (LCoE) is calculated with cost functions derived from power plant data. Results show that the integrated HCC configurations (fully-fired) show a significantly higher efficiency (40–41%, LHV (lower heating value)) than a stand-alone steam plant (35.5%); roughly half of the efficiency (2.4% points) is due to more efficient fuel drying. Because of higher investment costs, HCC options have cost advantages over stand-alone options at high biomass fuel prices (>25 EUR/MWh) or low discount rates (<5%). Gasification options show even higher efficiency (46–50%), and the lowest LCoE for the options studied for fuel costs exceeding 10 EUR/MWh. It can be concluded that clear efficiency improvements and possible cost reductions can be reached by integration of biomass with CCGT power plants compared to stand-alone plants.     

The impact of feedstock cost on technology selection and optimum size

Development of biomass projects at optimum size and technology enhances the role that biomass can make in mitigating greenhouse gas. Optimum sized plants can be built when biomass resources are sufficient to meet feedstock demand; examples include wood and forest harvest residues from extensive forests, and grain straw and corn stover from large agricultural regions. The impact of feedstock cost on technology selection is evaluated by comparing the cost of power from the gasification and direct combustion of boreal forest wood chips. Optimum size is a function of plant cost and the distance variable cost (DVC, $ dry tonne⁻¹ km⁻¹) of the biomass fuel; distance fixed costs (DFC, $ dry tonne⁻¹) such as acquisition, harvesting, loading and unloading do not impact optimum size. At low values of DVC and DFC, as occur with wood chips sourced from the boreal forest, direct combustion has a lower power cost than gasification. At higher values of DVC and DFC, gasification has a lower power cost than direct combustion. This crossover in most economic technology will always arise when a more efficient technology with a higher capital cost per unit of output is compared to a less efficient technology with a lower capital cost per unit of output. In such cases technology selection cannot be separated from an analysis of feedstock cost.     

Techno-economic comparison of series hybrid, plug-in hybrid, fuel cell and regular cars

We examine the competitiveness of series hybrid compared to fuel cell, parallel hybrid, and regular cars. We use public domain data to determine efficiency, fuel consumption, total costs of ownership and greenhouse gas emissions resulting from drivetrain choices. The series hybrid drivetrain can be seen both as an alternative to petrol, diesel and parallel hybrid cars, as well as an intermediate stage towards fully electric or fuel cell cars.We calculate the fuel consumption and costs of four diesel-fuelled series hybrid, four plug-in hybrid and four fuel cell car configurations, and compared these to three reference cars. We find that series hybrid cars may reduce fuel consumption by 34-47%, but cost €5000-12,000 more. Well-to-wheel greenhouse gas emissions may be reduced to 89-103 g CO₂ km⁻¹ compared to reference petrol (163 g km⁻¹) and diesel cars (156 g km⁻¹). Series hybrid cars with wheel motors have lower weight and 7-21% lower fuel consumption than those with central electric motors.The fuel cell car remains uncompetitive even if production costs of fuel cells come down by 90%. Plug-in hybrid cars are competitive when driving large distances on electricity, and/or if cost of batteries come down substantially. Well-to-wheel greenhouse gas emissions may be reduced to 60-69 g CO₂ km⁻¹.     

Local-scale analysis of carbon mitigation strategies: Tompkins County,New York,USA

The costs and potential for several carbon mitigation options were analyzed for Tompkins County, NY, within several categories: terrestrial carbon sequestration, local power generation, transportation, and energy end-use efficiency. The total county emissions are about 340 Gg C/year, with current biomass sequestration rates of about 121 Gg C/year. The potential for mitigation with the options examined, assuming full market penetration, amounts to at least 234 Gg C/year (69%), with 100 Gg C/year (29%) at no net cost to the consumer. Effective carbon mitigation strategies for this county based on costs per mg carbon and maximum potential include reforestation of abandoned agricultural lands for terrestrial carbon sequestration, biomass production for residential heating and co-firing in coal power plants, changes in personal behavior related to transportation (e.g., carpooling or using public transportation), installation of numerous residential energy-efficient products and development of local wind power. The principal barriers to the implementation of these approaches are discussed and policies for overcoming these barriers are analyzed.