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Growth responses of sessile oak to climate and hydrological regime in the Zbytka Nature Reserve, Czech Republic

100%

Čejková A. , Poláková S.

tom Vol. 39, no. 4

285-294

Complex of Nature reservation Zbytka is the rest of various fen vegetation in the northeast part of the Czech Republic. It represents an important spring area which provides high quality potable water for more than 150 000 inhabitants. Waterworks utilization was started in the 1960s and the change of land-use practices has had a strong effect on the ecosystem. Oak chronology has been showing different tree growth trends since the start of the waterworks utilization. Also the occurrenc-es of negative pointer years differ markedly before and after initiation of pumping underground water. Dendroclimatological analyses primarily revealed a close relationship between the temperature and tree growth - positive influence of spring and summer temperature. The period 1983-1992 of maxi-mum artesian water pumping is expressed as higher tree-ring increments, but linear model analyses showed that the growth reaction of oak is not due to simple causality between temperature and under-ground water level. The radial increments reacted positively to the combination of high temperature during the vegetation season and low or, the contrary, high depth of underground water level. No di-rect relationship was detected between tree growth and fluctuation of underground water level; de-spite of the results dendrochronological data may be useful in historical ground water modelling stud-ies. Results are also crucial for conflict of interests between nature preservation and potable water supply.

Analiza możliwości programu komputerowego przeznaczonego do symulacji przetłaczania wody na duże odległości

75%

Gałaj J. , Drzymała T.

TTS Technika Transportu Szynowego

2012

tom R. 19, nr 9

1055--1065, CD

W artykule omówiono model cyfrowy symulujący pracę układów przetłaczania wody na duże odległości. Ze względu na wysokie koszty badań laboratoryjnych i poligonowych, analizę taktycznych układów do symulacji podawania wody na duże odległości (przetłaczanie, przepompowywanie, dowożenie) prowadzi się obecnie coraz częściej przy zastosowaniu specjalistycznych programów komputerowych. Główna idea działania modelu polega na wyznaczeniu maksymalnej długości, na jaką można przetłoczyć wodę, przy założonej konfiguracji układu (liczba i typ pomp, wartości nadciśnień na stronach ssawnych pomp, typ zastosowanych węży, typ rozdzielacza i prądownic, liczba i długość linii gaśniczych, różnice poziomów między pompami) i wartości minimalnego wydatku. Jedyny w Polsce tego typu program został opracowany, przetestowany i zaimplementowany jako ćwiczenie w ramach laboratorium Hydromechaniki w Szkole Głównej Służby Pożarniczej w Warszawie.

Due to the high cost of laboratory and full scale fire hose lines tests more often computer program for simulation of such system are implemented. Unique computer program of water pumping system parameters was presented in this paper. Algorithms applied in the program are also given. Advantages and disadvantages of the program are discussed.

In-situ performance evaluation of photovoltaic solar water pumping system in the rural region

63%

Maka A. O. , Chaudhary T. N. , Hasan A. , Gatou A.

tom Vol. 3, No 1

69--76

The Photovoltaic solar cells convert the radiant energy from the Sun directly to electricity. Solar photovoltaic systems can help to fulfil the entire energy demands in rural areas by harnessing all the opportunities and potentials. The water is an important element in the life of plants, animals and human being. In this paper, it has been studied that solar energy could be used for water pumping applications such as providing water to rural and remote areas. It is being practiced in south Libya. The data is being collected over two years by measuring the water flow on daily basis at pumping head of (35m). In addition, this presents an evaluation of PV system in water pumping and piping systems and estimation of pumping energy cost. The solar pumping systems depend on water flow rate, pumping head and solar irradiance. The system components contain inverter, pump and PV generator. Besides, the effects of the climate and operating conditions on the performance of PV pumping systems has been discussed.

A comparison between directly connected and MPPT connected solar powered water pumping system using PMDC motor

51%

Sikder P. S. , Pal N.

tom Vol. 98, nr 1

80--88

This paper represents a comparative analysis of two photovoltaic pumping systems. To study the performance of the Maximum Power Point Tracking (MPPT) system, two models were simulated using Matlab/Simulink and the performance of a directly connected photovoltaic (SPV) pumping system was compared to an MPPT connected SPV pumping system at various levels of solar irradiance. The MPPT system maximizes overall system efficiency, but makes the system complex compared to the directly connected SPV pumping system. Instead of the conventional boost converter the MPPT system contains a buck converter to maintain overall system voltage at the lower levels required by the permanent magnet DC (PMDC) motor. For simplicity, the MPPT controller follows the perturbation and observation (P & O) algorithm and controls the buck converter to maximize overall system efficiency at various levels of solar irradiance. The PMDC motor provides high weight-to-torque density, better speed control, low inertia, and lower losses compared to induction and the conventional DC motor. The comparative analysis shows that the MPPT connected SPV system is more efficient than the directly connected SPV system for water pumping purposes using a PMDC motor.