Pumped-storage in Bulgaria – Developments, Current Situation and Some Perspectives

AbstractThe objective approach requires that the hydropower development cannot be analyzed outside the economical and overall national development of a particular country during a considered time period. Yet the current presentation addresses exclusively the Hydropower development in Bulgaria, and moreover, concentrated only on the features of pumped-storage as a reliable and still highly competitive energy storage technology.The pumped-storage as part of the hydropower development in Bulgaria and the situation as in 1989 are introduced. The overall development in Bulgaria after November 1989 and its impact on both running and future hydropower and pumped-storage projects are shortly presented. Particular features of the current situation are outlined. Furthermore, special attention is paid to the national legislative environment in the frame of the crucial policies, strategies and directives of the European Union.Finally, some ideas and project possibilities for the use of the still available pumped-storage potential in Bulgaria are discussed in more detail. The work ends with conclusions on the Bulgarian hydropower development with respect of pumped-storage mainly after 1989. Needed research activities in particular fields are identified for a possible future pumped-storage development in Bulgaria as an EU member state in the sense of global electricity market conditions

Determination of added mass for earthquake induced hydrodynamic loadings on vertical structures

Earthquakes can induce severe hydrodynamic loadings on dams and their equipment. The dynamic dam-reservoir interaction is usually modelled by the so-called added mass. There are two theoretical approaches in the literature, employing either momentum or compressibility theory. Both assume zero pressures at the top of the structure, leading to comparatively low design pressures for control structures. A new theory was developed for a simple approximation for added mass and hydrodynamic pressures. The added mass is assumed to be uniform over the dam height. The added mass becomes a linear function of acceleration and water depth. Comparison with 'classic' theories showed good agreement for accelerations up to 0.3g, and higher pressures for higher accelerations

Hydropower converters with head differences below 2·5 m

Hydropower with very low head (VLH) differences constitutes a largely unused potential source of renewable energy. A literature review of hydropower converters for VLH differences covering the engineering literature from the 1830s onwards was conducted to assess the potential of historic, current and emerging technologies. The results showed that a large number of different interesting technologies were used/developed, and that several novel and promising concepts are currently under development. Technologies emerged for different market segments: water wheels for low flow rates, turbines for large flow volumes. To take account of increased ecological demands and the desire for cost reduction, further improvements of existing technologies and new converter technologies have been developed. Other concepts described in the literature were apparently never applied although they promise development potential. The information gathered allowed for a comparison of available technologies with respect to area of application, performance, ecological impact and cost level

Fish Pass Functionality in Relation to the Dynamics of Hydrological Conditions in the Upper Course of the River Iskar (Case Study)

The investigated fish pass is a part of construction of а very low-head hydrostatic pressure machine (HPM) located on existing weir in the upper Iskar River. Monitoring of the hydraulic features of the fish pass during the different hydraulic conditions was performed. Diversity and abundance of the local fish fauna was carried out with the aim to verified target fish species. A major limiting factor for using of the fish pass during flood periods was high water velocity (both inside the fish pass and at the fish pass downstream entrance), while during the low water discharge periods it was the insufficient water depth in some pools and the significant differences between water levels in the adjacent pools. The difference between the water levels at the entrance and exit of the fish pass reduces the chances for access of small-sized fish species. For improving fish pass functionality, some measures were developed. Several re-construction solutions were proposed in attempt to help solving the identified problems