The suitability of the IEC 61400-2 wind model for small wind turbines operating in the built environment

This paper investigates the applicability of the assumed wind fields in International Electrotechnical Commission (IEC) standard 61400 Part 2, the design standard for small wind turbines, for a turbine operating in the built environment, and the effects these wind fields have on the predicted performance of a 5 kW Aerogenesis turbine using detailed aeroelastic models developed in Fatigue Aerodynamics Structures and Turbulence (FAST). Detailed wind measurements were acquired at two built environment sites: from the rooftop of a Bunnings Ltd. warehouse at Port Kennedy (PK) (Perth, Australia) and from the small wind turbine site at the University of Newcastle at Callaghan (Newcastle, Australia). For both sites, IEC 61400-2 underestimates the turbulence intensity for the majority of the measured wind speeds. A detailed aeroelastic model was built in FAST using the assumed wind field from IEC 61400-2 and the measured wind fields from PK and Callaghan as an input to predict key turbine performance parameters. The results of this analysis show a modest increase in the predicted mean power for the higher turbulence regimes of PK and Callaghan as well as higher variation in output power. Predicted mean rotor thrust and blade flapwise loading showed a minor increase due to higher turbulence, with mean predicted torque almost identical but with increased variations due to higher turbulence. Damage equivalent loading for the blade flapwise moment was predicted to be 58% and 11% higher for a turbine operating at Callaghan and PK respectively, when compared with IEC 61400-2 wind field. Time series plots for blade flapwise moments and power spectral density plots in the frequency domain show consistently higher blade flapwise bending moments for the Callaghan site with both the sites showing a once-per-revolution response

Financing mechanisms of solar home systems for rural electrification in developing countries

Photovoltaic (PV) based solar home systems (SHS) are often the least expensive electrification option in sparsely populated areas with low electric loads. This makes the SHS appropriate for rural electrification in the developing countries. However, the acquisition of a SHS requires high initial investment and moderate operating and maintenance cost. The lack of financial services for users of SHS is often regarded as the main barrier for their commercial dissemination. Several financing approaches have been practiced in different countries and reflected both positive and negative impacts. This paper reviews various financing mechanisms used worldwide for dissemination of SHS and discusses the potential of commercialization of SHS in remote rural areas in presence of a financial service. The success of a mechanism depends on various factors ranging from selection of the right mechanism for right location to implementation strategy of the selected mechanism. Donated or highly subsidized projects are found not to sustain for long term. Cash sale approach has lower market penetration record. Hire purchase and fee-for-service approaches are found to have higher success records than the others. However, financial schemes should be designed in such a way that financing institutions and financial intermediaries can recover their operational costs

Design and fabrication of low cost solar water heaters

We designed two types of very low cost solar water heaters which do not need a water supply connection. The first one consisted of two plastic bowls, one inside the other with 5 cm thickness of insulation in between. A transparent plastic cover was tied around the smaller vessel. It was found that water placed inside the smaller vessel had its temperature raised by 18°C from the ambient temperature within four hours when the average insolation was about 600 kWh/m2. The second one consisted of two earthen vessels in place of plastic bowls. The water temperature rise was 20°C under the same radiation. If either of the heaters was covered with cotton-wool insulation in the afternoon, the temperature remains 13°C above the ambient early next morning. The cost of the material was around US$4.50 for the plastic bowl heater while this is around US$ 3.50 for the earthen vessel water heater

Performance testing of lead acid batteries as a function of depth of discharge and yemperature in photovoltaic application in rural Bangladesh

In this paper, we report the results of short-term tests on three types of stand-alone systems. These tests are carried out in Grameen Shakti's laboratory. According to the battery manufacturer depth of discharge affects the life and performance of battery. The battery performance also depends on the temperature. Deep cycle batteries have been tested for a number of combinations of depth of discharge and temperature. The tests are carried out to find the depth of discharge at different temperature. For flooded lead - acid batteries the water loss is directly related to the state of charge in the battery. In general, higher the state of charge corresponds to greater water loss. Allowance of this water loss needs to be included in system design or maintenance plans. The experimental results show that the life of the battery depends on depth of discharge and is also affected by the temperature. The cycle life of the battery significantly reduces at higher temperatures. Also the process contributing to battery degradation is generally enhanced at these temperatures. Considering the environmental condition of Bangladesh the battery should be used down to 60% or below discharge for better performance

A photovoltaic solar home system dissemination model

Dissemination of photovoltaic (PV) electricity generation systems in developing countries faces a multitude of financial, technical, institutional and policy barriers. Demonstration of the system by appropriately selecting sites and users, providing an appropriate financial mechanism and technical support, and creating awareness among users can serve to trigger significant spontaneous propagation of PV systems. A strategy/approach adopted in promoting dissemination of solar home systems (SHSs) in Bangladesh is described, together with details of the methodology, including the planning, maintenance and training efforts undertaken. Progress in propagation of PV systems has been monitored since the installation of the demonstration systems; the success of the approach adopted can be gauged by the fact that since the installation of ten demonstration units in the selected area, a tremendous increase in the sale of PV SHSs has been observed