Interest in use of small scale biogas digesters in rural communities of Sub-Saharan Africa to generate cooking fuel, and to treat and utilise organic wastes is increasing, with numerous organisations promoting their use for both socioeconomic and environmental reasons. Small-scale biogas digesters have great potential to contribute to sustainable development by providing a wide variety of socioeconomic benefits, including diversification of energy (cooking fuel) supply, enhanced regional and rural development opportunities, and creation of a domestic industry and employment opportunities. Potential environmental benefits include reduction of local pollutants, reduced deforestation due to logging for fuel, and increased sequestration of carbon in soils amended with the digested organic waste. Ecosystem services that are potentially delivered through implementation of biogas digesters in rural communities are carbon sequestration, improved water quality and increased food production. Carbon can be directly sequestered in the soil through application of soil organic matter originating from the digested material. Indirect carbon sequestration can also be achieved through reduced carbon losses due to logging as household fuel is replaced by methane produced by the digester. Replacement of household fuel by biogas has added benefits to household air quality. Water quality can be improved through reduced runoff of waste material and reduced erosion of sandy soils due to stabilisation of the soil through increased input of organic matter. Food production can be improved by application to the soil of digested material containing readily available nutrients. The productivity of the soil can also be improved through improved soil structure and water holding capacity achieved by the organic amendments of digested material to the soil.
The global trend towards sustainability has led to increased interest in alternative power sources to coal and other fossil fuels. One of these sustainable sources is wind energy, which we can harness through wind turbines. However, a significant hindrance preventing the widespread use of wind turbines is the noise they produce. This study reviews recent advances in the area of noise pollution from wind turbines. To date, there have been many different noise control studies. In order to successfully reduce or prevent the noise generated, the sources of noise must be identified. Two major sources of noise are present during operation: mechanical noise and aerodynamic noise. Mechanical noise generally originates from the many different components within the wind turbine, such as the generator, the hydraulic systems and the gearbox. Different mechanical noise prevention strategies such as vibration suppression, vibration isolation and fault detection techniques are presented in this paper. Aerodynamic noise prevention strategies are also discussed. Aerodynamic noise is the dominant source of noise from wind turbines, with a sound power level of 99.2 dB A. Breaking this noise source down, the largest contributor to aerodynamic noise comes from the trailing edge of wind turbine blades. Strategies for reducing aerodynamic noise include adaptive solutions and wind turbine blade modification methods. There are a number of adaptive noise reduction solutions including varying the speed of rotation of the blades and increasing the pitch angle. Although such strategies have been successfully implemented for noise reduction purposes, they can cause significant power loss. Therefore, alternative methods of adaptive solutions are sought. Blade modification methods such as adding serrations have proven to be beneficial in reducing noise without any power loss. The aim of this paper is to critically analyse and compare the different methods currently being implemented and investigated to reduce noise production from wind turbines, with a focus on the noise generated from the trailing edge.
Many chemical suppliers are looking to alternative, eco-friendly raw materials. One of the main sources of renewable feedstocks are plant oils. The use of vegetable oils in organic synthesis is consistent with principle of sustainable development and reduces demand for imported oil. It is important to use the fuels containing biocomponents from renewable sources. Rape is one of the most cultivated oil plant which is a renewable raw material for production of liquid biofuels. The work presents both process of obtaining rapeseed oil and describes stages of transesterification process efforts to receive biodiesel.
Promotion of use of renewable energy sources are among the priorities of energy policy in Lithuania. District heating (DH) technology is promising tool for implementing energy and environment policy goals. Lithuania acceded to the European Union (EU) in 2004. Integration of new member states to the EU has created a new situation in the frame of implementation of EU sustainable development. At the moment the use of renewable energy is relevant for Lithuania not only for sustainable development targets, but also for practical reasons. After the closure of Ignalina Nuclear Power Plant Lithuanian energy sector development faced with significant challenges. Energy sector, including district heating, became dependent on natural gas. Lithuania imports natural gas from the sole energy supplier - Russia (Gazprom). New challenges for district heating sector are related to the possibilities of integration of renewable and local energy resources. A wider use of renewable energy can help to diversify of energy supply and to meet the targets of sustainable development. The paper presents an overview of the present Lithuanian and EU legal regulation of the use of renewable energy sources. Also the problems related to the use of renewable energy sources in district heating supply and measures that promote the use of these sources are analysed in the article.
In this study, the self sufficiency of a photovoltaic (PV) system installed on the roof of a single house is assessed in its response to the particularly severe weather conditions of Canada. Since the local climate presents large daily and yearly temperature fluctuations, in addition to the presence of snow, drizzle and freezing rain the design of renewable energy systems is very challenging. This research presents the investigation of both passive and active solar designs for a Canadian house. Self and transfer admittances of all surfaces were calculated. Furthermore, the zone admittance matrix has been derived for three different harmonics of the weather inputs. An explicit finite difference model is used to calculate the temperature of the all nodes which are considered. Further, the equations resulted from the finite difference model are solved by MathCAD. The passive response of the house shows around 20°C difference between room-air and ambient average temperature in a winter day. The second part of this study includes the simulation of the PV system and house energy consumption. It has been carried out by use of PVSOL. Consequently, by making a comparison between total consumption of the house and the electricity production by a PV system, the self sufficiency of a PV system was evaluated. This system is theoretically self-sufficient since the designed PV system provides 70 kWh in a sunny winter day when the maximum required energy for the building is 30 kWh approximately.