An Electrical Energy Audit of Water Pumping Machines

The study involves an energy audit of Pumps used to pump fluid from lower level to higher level by using electrical energy. A case study was conducted on centrifugal pumps at Ahmadu Bello University Water treatment plant, series of energy audit was conducted to record various parameters v iz., discharge, pressure, voltage, current, power, power factor and efficiencies to calculate the total electrical energy consumption per day and total actual energy use per day, maximum (VA )demand, maximum (KW )demand, consumption figures of the whole pump in the p lant, energy cost figures of the plant in (KWh), where we discovered very high energy wastage during operation .Therefore ways to reduce energy consumption by the replacement of the present pumps with inverter compatible energy efficient pumps and various conservation methods are recommended for optimum utilizat ion, this study will help other pumping stations.


Introduction
An energy aud it is the study o f a p lant or facility to determine ho w and wh ere energ y is used and id ent ify metho ds fo r energy sav ings . Th ere is no w a un iversal recogn it ion o f the fact that new techno logies and much greater use of some that already existed provide the most hopeful prospect for the future opportunities lie in the use of existing renewable energy technology , g reater effo rts at en erg y ef ficien cy an d th e d is s emin at io n o f th es e technologies and options. This energy audit o f the water works at Ah madu Bello University samaru main campus with emphases to electrical energy consumption in the pump stations is a step towards our destination of achieving energy efficiency and would like to emphasize that an energy audit is a cont inuous p rocess, in th is reg ard the research list possible actions to conserve and efficiently utilize our scares resources and identify various savings potentials .Over the years ,there has been significant progress at the university in all acad e mic an d res earch activ ities , an d p ara llel imp rovement in facilit ies and in frastructure, without any improvement in the water treat ment section and the present capacity cannot sustain the un ivers ity coup le with h igh electricity problems of low voltage which makes operation not possible at all time. M ino r and majo r mod ificat ions process des ign of th e p lant will resu lt in the d ramat ic imp rovement in the plant energy efficiency, the need for such modificat ions will be brought out by comparison of specific energy consumption per unit product.
The actual use of electrical energy has been calculated/measured at the output of electrical equip ment in the preliminary audit, improving the efficiency of energy conversion process will result in lo wer loading levels in the electrical equip ment and lower use of electrical energy. In examining the majo r low efficiency energy conversion processes and arrive at ways to reduce the energy consumption in those process. The possibility of using automatic controls in order to switch off electrical equip ment when the process does not really need energy and to adjust the efficient operation of electrical equip ment against varying process load levels should be critically examined. It is often possible to reset the process variables to new levels conducive for lower energy consumption after a critical examination of the process.
The Ahmadu Bello University water supply treatment scheme was established in 1970, by the Estate Department of Ahmadu Bello University, with a v iew to independently meet ing the university water supply demand.
The plant was designed to supply 13.64 million litres of portable water per day. It entails an impounded reservoir called kubanni Dam, water intake structures, water treatment works a booster station, main pressure pipeline and several small sized over-head tanks scattered over the campus.
The main pressure pipelines ranging fro m 350mm in diameter to 75mm distributes treated water fro m the treatment plant to all the lo w-pressure zones, these are:

Treatment Plant
This is where the raw water is treated and the treated water is finally pu mped out to the University community. So many changes occurs in the treatment p lant which also affect the loading condition of the pumps example replacement of the 600A mps electrical panel to 1000 sub standard panel with no necessary protective safety devices, high lift pumps are of lower capacity and lower speed with h igh consumption with any installation of energy saver.

Water Demand
Water demands are based on the guideline set forth in the National Un iversity Co mmission Standards guide as follows: 1-Residentail population =300litres per head 4 hours On the bases of the above figures, the total demand for the samaru campus is shown below; pumping system pumps and control panels including historical and present.
The main objective of this study is for the presentation of energy efficiency measure as bankable pro ject and viab le installation and to improve the overall efficiency of the p lant.

Methodol ogy
The study involves the calculating daily operation of energy consumption of pump ing mach ines used for the water distribution at minimu m and maximu m voltage demand of operation, visual inspection and data collection of hours of operation for a period of one year. Total electrical energy consumption per day and total actual energy use per day, ma ximu m VA de mand, ma ximu m KW de mand, consumption figures of the whole pu mp in the plant, energy cost figures of the plant in KWh.

Li mitati on
The following are the limitations of the project: -The non-availab ility of power supply fro m PHCN delayed the realization of the hour of operation of pumps.
-Frequent voltage drop from 400 amps to 300 amps fro m the PHCN necessitate the use of generator.
-Pu mps are not operated simultaneously.
-Preliminary Audit results are exp ressed in the form of load factor of the plant, power factor and average daily consumption.
-Electricity bill is centralized for the whole university the demand in KWh of electricity of can only calculated by the consumption of the unit by the PHCN charges wh ich is N8.50 per KWh.

Data Required on the Pump Operation
Pump No 1, No2, No3, No4: Daily operation hours 6hour morn ing, 6hours afternoon, 6hours night, voltage requirement fo r daily operat ion of the pu mps, isolations of pumps.
The Bar chart above shows the consumption rate in kWh on y axis and the cost of power in various hours of operation. At the first hour the operation, the consumption rate and cost of electricity is high which indicate good voltage of operation at the period, which is about 5:00am to 6:00am at a voltage of 348volt to 400volt. While the fourth hour shows lower consumption and cost it a period of low voltage and very high demand of electricity within the campus which 12:00p m to 1:00p m afternoon. Energy consumption for the above working hours was conducted without the use of any energy conservation strategy. The water supply to the university is taking from the water works lines wh ich pass through the campus .The supply begins at the main station to other areas close to the water treatment plant and to the booster station for supply to the areas far fro m the water treat ment plant.

Reduction of Ac tual Use of Electrical Energy
The actual use of electrical energy has been calculated / measured at the output of electrical equip ment in the audit. But the final value of electrical energy content in unit output will be less due to losses in energy conversion process. Improving the efficiency of energy covers ion process will result in lo wer loading levels in electrical equip ment and lower use of electrical energy. As far as electrical energy conservation is concerned, reducing the use of electrical energy is the primary action phase in the hierarchy of conservation strategies.

Load Management
Examination of daily active and react ive load curves for typical day at the incomer will reveal the need for load management in the system. Load management at primary level as envisage here involves techniques aimed at improving the daily act ive power load factor and bringing it close to unity and techniques aimed at bringing down the daily average reactive load factor to unity.

Reduction of Losses in Electrical Motors
Minimization of losses in pumps is a good strategy considered during the study. Induction motors constitute 70 to 80% of electrical load hence reduction of losses in these motors assumes special significance, so loading level are minimize in the study by better utilization of energy in the energy conversion process.

Motor Loading Analysis in Electrical Energy Audit
-Classify the motors into various categories depending on type of loading viz. continuous constant load duty, continuous variable load duty, intermittent duty with or without starting/electrical braking, short time duty etc. In each category, we classify the motor into lo w HP, mediu m HP and high HP Classes.
-Short time duty motors all rat ings may not offer much in terms of possible loss reduction, however, they may be used for peak shaving applications.
-Low HP motors may need only a cursory evaluation since the loss reduction achievable fro m them may not be enough to justify the effort and expense. However, the final decision in this matter will depend on the number of such motors in the plant, their HP d istribution, loading levels.
-The adequacy of rating (under rating or over rating or wrong type of motor etc, where checked in the study close attention was paid on duty with frequent starting/reversing/plugging etc.
-Determination of continuous constant load and continuous variable load which can offer possibilities of loss reduction. Their loading level must be determined, through load transfer. The water supply to the university is taking from the water works lines which pass through the campus. The supply begins at the main station to other areas close to the water treatment plant and to the booster station for supply to the areas far fro m the water treat ment plant.

Energy Consumption Audit
Almost all known energy conservation and management techniques aim at one or more reasons examp le, reduction of actual use of energy without much modification in the process design, reducing the payment to be made for energy and reduction of energy losses by identifying priority order, to arrive at a reco mmendations by introduction of new changes in operation, changes in sequence of operations, replacing inefficient equip ment/process with energy efficient equipment.

Reduction of Ac tual Use of Electrical Energy
The actual use of electrical energy has been calculated/measured at the output of electrical equip ment in the preliminary audit. But final value of electrical energy content in unit output will be less than the value obtained due to losses in energy conversion process .Improving the efficiency of energy conversion process will result in lower loading levels in equip ment and lower use of electrical energy.

Auditing Tools
The following tools were used during the study. -Visual inspection -Volt meter, ammeter -Power analyser (measures active, reactive, apparent power, power factor energy consumed)

Benchmarking
Energy benchmarking involves the development of quantitative and qualitative indicator through the collection and analysis of energy and energy management practices. Benchmarking in simp listic terms is the process and to improve the standard of the process to improve quality of the system, product, services etc. It allows the research to develop plans on how to adopt best practice, usually with the aim of increasing some aspect of performance. assessment and logical evolution of avenues for improvement where emp loyed in this study .Historical data, well documented in this study which help to bring out energy consumption and cost trends month-wise /daily. Trend analysis of energy consumption, cost, relevant production features, specific energy consumption, help to understand effects of capacity utilizat ion on energy use efficiency and cost on a broader scale.
The Study was conducted to create a data baseline energy measurement for reference during post implementation measurement and verification and presentation of efficiency measures as bankable pro ject and viable installation by doing so quantifying energy losses and energy saving potential performance trends and specific energy consumption. This chapter present results obtained from the operation of the four selected most functional pumps in the plant.

Pump Study
Existing efficiency of the pump is evaluated by measuring of flow head and head losses and power, operating characteristics curves of pumps are known by the measurement of all parameters at various load conditions. Reco mmendation made to imp rove the overall efficiency pumping system with the review and understanding the operational conditions and process of operation of pumping system. Study pattern of operation of indiv idual pu mps including number of operating hours of the individual pumps for the past 12 month. Logged details of daily measurements like flow head, power parameters are referred to where available, and used as appropriate, in arriv ing at conclusion regarding energy measures.
Determination of power consumption of pumps while running the pumps in parallel, every minute data logging and power is made for a min imu m period of 20minutes.Based on this study suggestions were made.

Energy Saving Calcul ati ons
Annual energy savings, system modifications suggested, cost benefit analysis. Energy consumption patterns for the (PHCN), it has been assessed that the total consumption of energy and the amount paid to Power Ho lding Co mpany of Nigeria and the specific data on energy consumption for the water treat ment plant which is on the estimate of the university consumption. However, with the data availab le about utilization of power in the campus and electricity bill over a period of one year has been gathered and computed on the whole university per month to a time of 81.41M wh out of which the water treatment plant has a lion's share off about 55%.
Calculation for and reco mmendations, replacement of the existing normal pu mps with inverter co mpatib le energy efficient pump at Ahmadu Bello Un iversity water treatment plant (45kw with 30kw pump ) which will reduce power consumption.

Discussions
To determine ways of reducing energy consumption per unit product or the lower operating cost, energy audit reduce the specific electrical consumption, and modificat ion in plant processes also help in the reduction of consumption of energy .The need for such modification will be brought out by a comparison of specific energy consumption of the plant standard values pertaining to that particular product. Issues regarding process design were examined in energy audit as far as to their imp lication on reducing the load level on electrical equip ment and reducing losses in the electrical system.
The intensity and depth of planned electrical energy audit will depend on a comparison between the best specific energy consumption figures of the product achieved in any industry on a world wide scale and figures for the plant in question or references values for specific energy consumption. The bulk metering g ive an overall estimate of the cost of electricity wh ich fluctuate with time and error may occur in the process of reading the meter of otherwise, and also the university have very little control over their electricity cost.

Conclusions
The finding of the study serves as the basic for making the following conclusions;  There is an absolute power problem in the treat ment plant basically lo w voltage.
 Continuous duty rated motors are used for an intermittent duty with frequent starting, which increases losses.
 The electricity consumed is not proportional to the production of water at the treatment plant.
 Results obtained shows wrong types of pumps are use at the plant without any energy conservation emp loyed during operation.
 Electricity b illing method use by the power Ho lding Co mpany of Nigeria is not accurate.