ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675697

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The modal behaviour of wind turbine support structures can be assessed using the techniques of Rayleigh [10] and Stodola [11]. Guyed wind turbines are lighter and therefore cheaper than free-standing ones. Guyed structures are in a permanent state of stress due to the pre-tension in the cables. Further, wind turbines are subject to a large horizontal force during normal generation of electricity due primarily to axial thrust on the powertrain. Many of the forces on the structure fluctuate significantly at frequencies of P and nP (the rotor frequency and the rotor frequency multiplied by the number of blades on the rotor). Other forces due to turbulence and the spatial distribution of wind velocities are stochastic. Changes in the axial thrust on the powertrain are relatively slow since this load is dependent on the average windspeed calculated over the rotor disk and on the rotational frequency. If the wind turbine is connected to a strong electrical grid, the rotational frequency is fixed by the grid frequency. This therefore constitutes another pre-stress on the structural system.

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675698

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

If a wind turbine is located on a floating structure, it will experience rigid-body motions which could have a significant effect on the power output. This paper examines and develops methods for calculating the rigid body motion response in ocean waves of semi-submersible floating vessels suitable for mounting wind turbines. These methods are then utilised to optimise the layout candidate designs in order to minimise velocities and accelerations. It is found that the optimum layouts are an in-line design with stability abutments or a polygon based design, depending on whether or not the moorings allow the vessel to align with the wind direction.

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675699

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this paper we investigate the applicability of the parametric model normally applied for crystalline Silicon solar cells to thin film devices. We start with a short overview of the standard model and discuss several assumptions that should be investigated when the model is to be applied to thin film devices. It is explained that it is necessary to distinguish two separate cases, polycrystalline thin film devices and amorphous Silicon devices. Both classes violate the essential principle of superposition that is essential in the derivation of the standard Shockley theory. These violations are explained in this paper and solutions to overcome the problems are suggested. Finally the applicability of these models is investigated by applying them to measured current-voltage characteristics. The results show that the methodology described is adequate for the modelling of thin film devices.

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675700

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Pico hydro power is a renewable energy system which has the potential to provide millions of rural people world-wide with a cheap, sustainable source of electricity. The development of new, cost-reducing approaches, including local manufacture and implementation in developing countries, has increased the accessibility of this technology to large numbers of people. The new approaches are investigated and some of the present constraints to wider adoption of this technology are analysed.

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675701

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Experimental investigation into the effect of various blade shapes on the performance of the Wells turbine is presented. The aim was to discover if the backward swept and optimised designs of blade shape could alter the shape of the pressure distribution around the profile, so as to postpone separation and stall. It was found that the backward sweep of the blades did not delay stall, but it was much less abrupt, with the turbine countinuing to produce power after it had begun to stall. It gave an almost constant torque and therefore power value over a wide flow range. The optimised blades gave a higher positive value of efficiency and increasing torque value over a wide flow range, up to the point where stall suddenly occurs.

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675702

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper describes an EPSRC (Engineering and Physical Sciences Research Council) funded CASE project (in collaboration with BG (British Gas) PLC.) to develop and test a small-scale solar powered absorption cooling system for domestic or small industrial use. A rig has been constructed consisting of a solar collector system, incorporating sixty Thermomax evacuated collector tubes with a total surface area of 6m2, and an absorption system. The absorption system consists of generator, condenser, evaporator and absorber sections which are of shell and tube construction. The shells are glass vessels to enable the processes of absorption and desorption to be observed. The system will initially be tested using the common absorbent-refrigerant pair of lithium bromide and water. Other salt and water based pairs will then be tested and compared to the results from the standard lithium bromide and water combination.

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675703

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675704

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675705

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0143-0750    

DOI:10.1080/01430750.1998.9675696

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor