Method of estimating the efficiency of pumping unit frequency regulation (to be discussed)

Summary

The method of estimating energy saving from using frequency regulation of the pumping unit capacity in water supply systems is presented. The estimation of the capacity efficiency of pumping units is carried out only from the energy saving resulting from the use of frequency regulation instead of throttling (other saving components are not considered). To estimate energy saving it is required to compare the power consumed from the grid in the existing scheme of the regulation by penstock gate throttling and in the frequency regulation scheme. Then the energy saving in monetary form shall be compared with the expenses for retrofitting the frequency regulation system. The method is based on the graphical analysis of the pump operation point parameters in the operating group and optimized for the use in water supply systems operating by the pressure.

Key words

capacity , power saving , frequency regulation , pumping unit , efficiency evaluation , throttling

Method of evaluating the effectiveness of frequency regulation of the performance of sewage pumping units

Summary

The method of evaluating energy savings through the use of frequency regulation of the pumping unit performance at sewage pumping stations is considered. The method is based on a graphical analysis of the parameters of the operation point of the pumps in the working group and is developed for the use in sewer networks that operate according to the level in the receiving tank. The proposed method of evaluating the effectiveness of frequency regulation at sewage pumping stations has been proved by many years of experience of using and is precisely evaluative. Energy savings at sewage pumping stations are significantly lower than at water pumping stations. This applies to the systems with start/stop control because the effect of frequency regulation consists in reducing the velocity of fluid in the pressure pipeline. The bigger the dynamic component of the network characteristic in relation to its static component (in the range of the station capacity change), the stronger effect is manifested. In practice, this is extremely rare. The energy savings in the above examples with the start/stop mode does not exceed 10% (excluding the losses in the frequency converter).

Key words

sewerage pumping station , power saving , frequency regulation , pumping unit , efficiency evaluation

The experience of evaluating the efficiency of the actions of the investment program of a water supply and wastewater disposal enterprise

Summary

The communal infrastructure of the water supply and wastewater disposal in Russia needs renovation. The need in reconstruction and upgrade of the public water supply and wastewater disposal systems increases year by year. In this context any enterprise in compiling targeted lists of development program actions faces the problems of substantiating and evaluating the efficiency of the actions, prioritizing their implementation. The approaches determined in the branch regulatory legal acts do not provide for evaluating adequately the efficiency of construction, renovation and upgrade of the public water and wastewater facilities and substantiating the need in them. Taking into account the specificity of the enterprise and the experience gained SUE «Vodokanal of St. Petersburg» developed an additional tool for evaluating the efficiency and substantiating the actions; prepared and put in force the guidance documents. The suggested tool includes the evaluation of the economic efficiency of an action, its contribution to the achievement of the planned reliability, quality and energy efficiency as well as of the implementation risk. The tool has been approbated in the process of developing the investment program of SUE «Vodokanal of St. Petersburg».

Key words

water supply , water disposal , investment program , efficiency evaluation , technology audit