• Energy Research
• Closed Access close
• Restricted close
• Embargo close
• 13. Climate action close
• 15. Life on land close
• 1. No poverty close
• SE close

The delayed harvest system for grass crops in which the harvest of the previous year's crop is undertaken after it has over-wintered in the field significantly improves the fuel quality for both combustion and gasification. The critical elements that cause fouling and corrosion problems in boilers are alkali and chlorine which are released during combustion. The concentrations of these are reduced by a factor of 2 to 6 by using the delayed harvest system rather than harvesting in the end of the growing season. The loss of some leaf material and leaching of alkali also contributes to an increase in the ash fusion temperature from 1070°C to 1400°C. This work is part of a project in progress involving 14 different field trials distributed all over Sweden. Results are presented demonstrating that ash content is influenced by the type of soil. The most extreme variations are between reed canary grass grown on high clay content soils and those produced on very humic soils, with ash contents of 10.1% and 2.2%, respectively.

Abstract For biomass/waste fueled power plants, stricter regulations require a further reduction of the negative impacts on the environment caused by the release of pollutants and withdrawal of fresh water externally. Flue gas quench (FGQ) is playing an important role in biomass or waste fueled combined heat and power (CHP) plants, as it can link the flue gas (FG) cleaning, energy recovery and wastewater treatment. Enhancing water evaporation can benefit the concentrating of pollutant in the quench water; however, when FG condenser (FGC) is not in use, it results in a large consumption of fresh water. In order to deeply understand the operation of FGQ, a mathematic model was developed and validated against the measurements. Based on simulation results key parameters affecting FGQ have been identified, such as the flow rate and temperature of recycling water and the moisture content of FG. A guideline about how to reduce the discharge of wastewater to the external and the withdrawal of external water can be proposed. The mathematic model was also implemented into an ASPEN Plus model about a CHP plant to assess the impacts of FGQ on CHP. Results show that when the FGC was running, increasing the flow rate and decreasing the temperature of recycling water can result in a lower total energy efficiency.

Over the past three decades, Swedish energy policy has evolved in three major stages—oil reduction, phase-out of nuclear energy, renewable energy—each with a different focus. Since 1977, Swedish law has required municipalities to develop an energy plan that addresses the supply, distribution, and use of energy. Whether such plans have contributed to the development of local energy-systems has been a subject for debate. This paper is based on a study of 12 municipal energy-plans that attempted to control and develop local energy-systems in southern Sweden. The analysis examines how municipalities promote oil reduction, efficient energy use, and the use of renewable energy. The plans varied in planning processes, contents, and level of ambition. The results of the study show that the contents of the plans follow the national energy-policies with respect to reduction of oil use, improved energy efficiency, and increased use of renewable energy.

This paper is a contribution to the discussion on the relation between thermodynamics and economic theory. With respect to thermodynamic constraints on the economy, there are two diametrically opposite positions in this discussion. One claims that the constraints are insignificant (‘of no immediate practical importance for modelling’) and in the intermediate run, do not limit economic activity and, therefore, need not be incorporated in the economic theory. The other holds that thermodynamics tells us that there are practical limits to materials recycling, which already puts bounds on the economy and, therefore, must be included in the economic models. Using the thermodynamic concept of entropy, we show here that there are fundamental problems with both positions. Even in the long run, entropy production associated with material dissipation need not be a limiting factor for economic development. Abundant energy resources from solar radiation may be used to recover dissipated elements. With simple, quantitative analysis we show that the rate of entropy production caused by human economic activities is very small compared to the continuous natural entropy production in the atmosphere and on the Earth’s surface. Further, the societal entropy production is well within the range of natural variation. It is possible to replace part of the natural entropy production with societal entropy production by making use of solar energy. Society consumes resources otherwise available for coming generations. However, future generations need not have less resources available to them than the present generation. Human industrial activities could be transformed into a sustainable system where the more abundant elements are industrially used and recycled, using solar energy as the driving resource. An economic theory, fit to guide industrial society in that development, must not disregard thermodynamics nor must it overstate the consequences of the laws of thermodynamics. © 2001 Elsevier Science B.V. All rights reserved.

A factorial design was used to study direct effects of external biomass-producing factors such as light, temperature and photoperiod on cadmium (Cd) uptake and indirect effects, via change in biomass production in two ecotypes of Scots pine (Pinus silvestris). The aim was to find out if the external factors affect the Cd uptake directly or via change in biomass production, and if the effect differs between ecotypes. Seedlings were grown under 10 combinations of external factors, i.e. temperature (15 and 20 degrees C), light intensity (50 and 200 micromol photons m(-2) S(-1)), photoperiod (18 h light/8 h darkness and continuous light) and external Cd concentration (totally 1.88 and 7.50 micromol). The treatment lasted for 18 days and Cd concentrations in roots and shoots were determined by AAS. The results showed that an increased biomass production increased the total Cd uptake but had a dilution effect on the Cd concentration, especially in the root tissues. The external factors tested did not have any direct effects on the Cd untake, only in the case of Cd translocation to the shoot did the higher temperature show a direct increase, but only in the southern ecotype. The two ecotypes reacted differently in Cd uptake and translocation to the external factors studied. The relative Cd uptake creased with increasing photoperiod in the northern but not in the southern ecotype. The southern ecotype decreased the Cd concentration in the shoot with increased light intensity caused by a dilution effect due to extensive shoot growth of this ecotype. The conclusion is that the uptake in pine seedlings is mainly regulated via biomass production, and not directly by light and temperature and that resulting plant Cd contents to a certain extent depend on plant origin.

Abstract To reduce greenhouse gas (GHG) emissions and fossil fuel consumption, addition of renewable alcohols to Diesel fuel may offer a potential solution. However, use of such alcohol/Diesel blends in existing Diesel engines is not yet fully understood. In the present study, alcohol/Diesel blends were tested by examining engine performance and emissions in both a light duty (LD) engine and a heavy duty (HD) engine with settings typical of those used in production engines. In addition, cold start tests of the blends were performed in a multi-cylinder LD Diesel engine. Four different alcohols were selected to mix with Diesel, i.e. n-butanol, isobutanol, 2-ethylhexanol and n-octanol. These alcohols were blended separately with either hydrotreated vegetable oil (HVO) or di-tertiary-butyl peroxide (DTBP), acting as cetane number (CN) improvers, in Diesel fuel. The mixtures were prepared to have the same CN as Diesel fuel. The results indicated that with similar CN and the same engine settings, the alcohol/Diesel blends and Diesel fuel exhibited the same start of combustion and almost identical heat release processes. The blends generated slightly faster combustion and a higher indicated thermal efficiency than Diesel fuel under most of the tested conditions and in both engines. Diesel blends of n-butanol and 2-ethylhexanol showed good cold start performance in the multi-cylinder LD engine. Results regarding emissions demonstrated that the total particulate matter (PM) number was reduced when using alcohol/Diesel blends and the PM diameter seems to decrease as the amount of oxygen in the fuel was increased in the LD engine. It was concluded that alcohol/Diesel blends produce much less soot than Diesel fuel in both types of engine owing to the higher oxygen content in the blends but cause slightly increased NO formation.

The current and future costs of willow short rotation coppice production in Sweden are analysed, considering all relevant cost factors explicitly. The future production costs are estimated considering effects of coppice area expansion and learning. The current and future costs of land and of risk premiums are subsequently estimated. Subsidies for farmers are not considered. If the area of willow cultivation were to expand enough to generate economies of scale, the production cost could be cut by about 10% compared to the current level. When learning effects are also considered, the total cost reduction potential is about 35%. Two major cost components (fertilization and road transport) are roughly stable while two other major cost components (establishment and harvest) have larger prospects for cost reduction, primarily due to potential for learning. Land costs and risk premiums vary and are uncertain, but both are estimated to be potentially significant compared to other cost components. Requirements of risk premiums may become lower as a consequence of area expansion and learning. Land costs are subject to many factors that are inherently uncertain, not the least future food prices. Efficient policies promoting an expansion of willow cultivation are discussed.

System downtime and unplanned outages massively affect plant productivity; therefore, the reliability, availability, maintainability, and safety (RAMS) disciplines, together with fault diagnosis and condition monitoring (CM), are mandatory in energy applications. This article focuses on the optimization of a maintenance plan for the yaw system used in an onshore wind turbine (WT). A complete reliability-centered maintenance (RCM) procedure is applied to the system to identify which maintenance action is the optimal solution in terms of cost, safety, and availability. The scope of the research is to propose a new customized decision-making diagram inside the RCM assessment to reduce the subjectivity of the procedure proposed in the standard and save the cost by optimizing maintenance decisions, making the projects more cost-efficient and cost-effective. This article concludes by proposing a new diagnostic method based on a data-driven CM system to efficiently monitor the health and detect damages in the WT by means of measurements of critical parameters of the tested system. This article highlights how a reliability analysis, during the early phase of the design, is a very helpful and powerful means to guide the maintenance decision and the data-driven CM.

In this study we estimate the effects of climate change on forest production in north-central Sweden, as well as the potential climate change mitigation feedback effects of the resulting increased carbon stock and forest product use. Our results show that an average regional temperature rise of 4 degrees C over the next 100 years may increase annual forest production by 33% and potential annual harvest by 32%, compared to a reference case without climate change. This increased biomass production, if used to substitute fossil fuels and energy-intensive materials, can result in a significant net carbon emission reduction. We find that carbon stock in forest biomass, forest soils, and wood products also increase, but this effect is less significant than biomass substitution. A total net reduction in carbon emissions of up to 104 Tg of carbon can occur over 100 years, depending on harvest level and reference fossil fuel. (C) 2011 Elsevier Ltd. All rights reserved.