Tag Archives: efficiency

xxx M. Polák
The influence of changing hydropower potential on performance parameters of pump in turbine mode
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The influence of changing hydropower potential on performance parameters of pump in turbine mode

M. Polák

Czech University of Life Sciences in Prague, Faculty of Engineering, Kamýcká 129, CZ16521 Praha 6, Czech Republic
Correspondence: karel@tf.czu.cz

Abstract:

Various types of hydromotors that enable energy recovery simultaneously with the required pressure reduction can be used in the field of fluid pumping systems. Similar principle is applied, for example, in the case of use of hydrodynamic pumps in turbine mode (PAT), which are also used as an alternative to conventional turbines in small hydropower plants. However, these pumps do not usually have the possibility of regulating hydraulic parameters, as it is common with conventional turbines. This specific feature needs to be taken into account, when designing such system. Article analyses computational methods for the conversion of the performance characteristics and compares these results with experimentally measured data on a particular pump in turbine mode. The results indicated that conversion can be well used in practice to predict outputs as well as to determine the optimum total head and flowrate to ensure maximum efficiency of PAT operation. Further computations were influenced by deviations resulting from the change in efficiency during PAT operation.

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1824-1829 M. Polák
Application of conversion model for designing hydrodynamic pumps in turbine mode
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Application of conversion model for designing hydrodynamic pumps in turbine mode

M. Polák

Czech University of Life Sciences in Prague, Faculty of Engineering, Kamýcká 129, CZ16521, Praha 6, Czech Republic
Correspondence: karel@tf.czu.cz

Abstract:

The use of the smallest water resources has been coming again to the centre of interest in recent years. A water engine – turbine, is the heart of these power plants. This is usually the highest expense for the investor, in terms of cost. The effort is therefore to seek investment less demanding alternatives. One of them is the use of hydrodynamic pumps in reverse turbine operation. This paper provides a methodology for conversion of parameters of the smallest power pumps (micro hydro sites) to turbine operation. The conversion model is based on the results of experimental research at the author’s workplace and is suitable for pumps with low specific speeds and outputs. The pump design process for turbine mode is complemented by a practical example for a specific deployment site. This example also serves to verify the accuracy of the conversion model.

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1189–1197 M. Polák
Experimental evaluation of hydraulic design modifications of radial centrifugal pumps
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Experimental evaluation of hydraulic design modifications of radial centrifugal pumps

M. Polák

Czech University of Life Sciences in Prague, Faculty of Engineering, Kamýcká 129, CZ165 21, Praha 6, Czech Republic
Correspondence: karel@tf.czu.cz

Abstract:

In the field of small hydropower, pump units in turbine mode (PAT) are frequently used as alternative to conventional turbines. In order to maximize their operation efficiency, it is possible to optimize the performances of these engines through various simple innovative modifications which relate mainly to the geometry of the flow parts. This paper deals with the results of several successful modifications verified on one such engine. While various simple modifications led to the increase of overall efficiency and power output by few percentages, power output increased by nearly 30% with the innovated runner blades geometry. The modifications also had positive effects on the pump’s operation, with significant increases in flow rate, head and total efficiency.

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1652-1658 R. Neděla and R. Neděla
Support scheme for CHP and its sensitivity on heat wasting
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Support scheme for CHP and its sensitivity on heat wasting

R. Neděla¹* and R. Neděla²

¹Czech University of Life Sciences Prague, Technical Faculty, CZ 16521 Prague 6 – Suchdol, Czech Republic
²University of Economics, Prague, Faculty of International Relations, CZ 13067 Prague 3, W. Churchill 4 SQ, Czech Republic
*Correspondence: nedela@tf.czu.cz

Abstract:

This paper describes basic principles of the CHP, advantages and disadvantages, technologies. In first part of article are described principles of CHP from the viewpoint of the energy customer. Second part describes basic Directives by the European Commission on promotion CHP and third part the most important part focus on the sensitivity of primary energy saving (PES) on outputs especially heat wasting.

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280-286 I. Ziemelis, H. Putans and L. Kancevica
Investigation of Solar Collector Irradiated from Both Sides
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Investigation of Solar Collector Irradiated from Both Sides

I. Ziemelis, H. Putans and L. Kancevica

Research Institute of Agricultural Machinery, Latvia University of Agriculture,
Institute Street 1, LV–2130, Ulbroka, Riga region, Latvia
e-mail: Imants.Ziemelis@llu.lv; Liene.Kancevica@llu.lv

Abstract:

The ordinary flat plate solar collector receives solar radiation only from one side of its surface. Another side is covered with a heat barrier. The solar collector with reflectors has been developed and examined to track the sun. The absorber of this type of a collector was irradiated from both sides. The experimentally obtained energetic parameters of the collector tracking the sun have been compared to those of the ordinary flat plate solar collector. In order to complete the experiment, a special stand has been developed. The experimental investigation has been carried out at the intensity of radiation 2,000, 1,000 and 500 W m -2 in different combinations. The temperature has been measured in certain points of different parts of the collector by several thermocouples. With the aid of a multi-meter, the obtained results were collected to the memory of a computer, and later processed and analyzed. When a collector surface is tracking the sun, the heat energy produced by the collector is 1.4 to 1.5 times higher in comparison with a stationary solar collector of the same size. A solar collector tracking the sun and irradiated from both sides depending on the reflection quality of the reflector’s material is able produce about 2.5 times more heat energy then a stationary flat plate solar collector irradiated only from one side.

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