Investigation of Pumped Storage Hydro Electricity

Transcription

1 International Conference on Machine Learnin, Electrical and Mechanical Enineerin (ICMLEME'04) Jan. 8-9, 04 Dubai (UE) Investiation of Pumped Storae Hydro Electricity rsalan F. Latif, and Soorkeu. trooshi bstract In this work pumped storae hydro is studied within the context of numerical representation of the workin equations with respect to two variables; head and flow rate. The results are verified aainst the outcome of a test ri, assembled for this purpose. Usin the approved computational model, a parametric study has been performed to show the effect of the workin parameters on such a system. By increasin the flowin water temperature from (0-40 o C), the power production in the experimental ri indicated a reduction of (.848 kw) when the friction factor in the penstock showed a reduction of (0.005 e-3). The relation obtained between the head and the flow rate is linearly proportional and at specific workin conditions it has shown (6.67%) reduction in flow rate over a heiht of (0m). There are a lare number of water storae and reservoirs available in this reion of Iraq includin over (60) sites in Erbil Province alone. Based on this study, it can be estimated that each source can help in eneratin (-5 MW), which can collectively account for up to (5-40%) of the power demand in the reion (Erbil; o N, o E). Keywords flow rate, head, hydro, pumped storae I. INTRODUCTION NE of the reatest technical and commercial obstacles for Orenewable enery is enery storae. Weather a renewable enery source is available or stronest only at certain times of day, like solar and wind or available 4 hours a day like wave enery or run of the river hydro, makin that electricity accessible when it is needed most is a challene that must be overcome. The storae of electricity offers sinificant benefits for the eneration, distribution and use of electric power. Combinin some form of enery storae with a renewable enery source helps remove this uncertainty and increase the value of the electricity enerated, []. Enery storae technoloies can provide a vital link between the primary source of enery and its actual use. In particular, the inclusion of an enery storae system allows flexibility in matchin the availability of an enery source to the demand profile in terms of where and when power is required and at what level, []. Despite the reduction in lobal rainfall levels and the increase in the frequency of drauhts, pumpin hydro is still rsalan F. Latif is with the Municipality of the city of Erbil, Erbil, IRQ (00964(0) ; arsalan_faruq@yahoo.com). Soorkeu. trooshi, is with the Department of Mechanical Enineerin, Salahaddin University, Erbil, Kirkuk Road IRQ ( soorkeu@ mail.com). one of the most established means of enery storae. It is rapidly deployable to the power rid as in a matter of minutes it can reach full capacity and in many cases a common network is used for hydro-power eneration and pumpin storae hydro. In the northern reion of Iraq, there are more than (30) suested potential sites for dam construction, fiure (), [3] which can actively participate in small-size pumped storae hydro systems. It is aimed in this work to arrive at a verified computational model throuh comparison of head and flow rate with a minimal capacity experimental ri. The model is used to run a parametric study on the system performance and based on obtained outcomes; conclusions are drawn to the applicability of such a system in the reion.. Environmental Issues, Hybrid Enery pplications and Economic Justifications New state of the art hydro power plants have an efficiency of well above 93% and new pumped storae plants may have an enery ratio of 76% (European Commission, 008), [4]. Based on the assessment and verification of the most efficient operation point with the best environmental implications, it is suested that it is neither the electricity from thermal sources saved nor the cost saved at peak hours that should drive the decision on water pumpin. The social profitability index should be the net increase in surplus, that is the difference between the larer ross surplus of an increased quality consumed at peak period but partially produced at low coast at off-peak periods on one hand, and the welfare loss of the offpeak period where more is produced than consumed on the other hand. In villaes and areas where it is difficult to be connected to a reliable source of electricity, pumped storae can play an active role in extendin the power supply. The joint participation of solar, wind, with diesel enerator back up [5], has already been discussed but the collective effect provided by includin seasonal micro hydro systems supported by pumped storae is addin fresh environmentally justified momentum into off-rid power supply in mountainous areas. In pumped-hydro systems pumps shutdown and chaneover are major sources of instability and the complex dynamics and balancin of the process [6],[7],[8] are major causes of irreularities and deficiencies in the system. Therefore more emphasis is placed on improvin the simulation of individual systems with different environmental and workin conditions includin the followin setup indicated in this work, specific for improvin micro-plant experimental verification. 05

2 International Conference on Machine Learnin, Electrical and Mechanical Enineerin (ICMLEME'04) Jan. 8-9, 04 Dubai (UE) II. THEORY ND COMPUTTIONL MODEL The computational model divides the flow area into discretized elements. These elements are considered as separate control volumes in which the workin equations rule. The workin equations take into consideration the effect of property variation and friction factor for each element. The output of each control volume is considered as the input into the next section. Collectively they form the domain that is considered for investiation as the water flows throuh, from the upper reservoir into the lower reservoir. The analysis of the dominatin equations for hydropower eneration is based on combinin the basic mass, enery and momentum equations to establish the workin equations for the flow, losses and the consumed time as derived explained and cateorized in the followin section bellow: Water can enerate power when it moves from a hih potential enery state to a low potential enery state [9]. The chane in potential enery (ΔPE) of water is: dt PE = m h water water For volumetric flow rate as in fiure (-a) To calculate the volume consumed in (dt): For a decreasin rate = v Since for the same system, accordin to Torricelli: dt In the limit from (h ) to (h a ) Q dt = v dt V = dh dh = v dt dh h = dt = h dh t ha dt = h dh t h dh () () (3) (4) (5) (6) (7) = t ha h = t h ha = a t h h (8) (9) (0) () The total loss coefficient of the pipe is (kt) and it is equal to combinin the minor (km) and the major (kf) loss coefficient as in fiure (-b): v = h kt Incorporatin this into equation () ives: = kt () (3) III. DESCRIPTION OF THE TEST RIG The test ri was assembled to verify the findins of the computational model, developed in this work. The ri construction was carried out keepin in mind the simplest desin to lower the costs and minimize the required time to make the experimental evaluation. The test ri is composed of the followin components as in fiure (, a & b). Two water tanks were used, the upper tank havin the followin dimensions; diameter = m, tank heiht =.5m, and the dimensions of the lower tank were; diameter = 0.57 m, and tank heiht = 0.9m. They were made of alvanized steel, ae 0.4 mm, similar to the type used in residential units. Pipin was made of PVC tubes with an inside diameter of m and the outside diameter was restricted to 0.05 m when the tube lenth reached 8m. One ball valve was used to control the descendin flow of water from the upper tank and a pump (PK 60, 0.5 hp, 0.37 kw) was used to move the water from the round level. The assembly of the components produced a small model of a pumped hydrostation. The two tanks represented the upper and lower reservoirs. The two reservoirs were connected by the PVC tubes, representin the pipin network. The turbine performance in the actual pumped hydro station was numerically modeled with the help of the fiures from the t h ha 06

3 International Conference on Machine Learnin, Electrical and Mechanical Enineerin (ICMLEME'04) Jan. 8-9, 04 Dubai (UE) exit flow line of the experimental ri passin throuh the pump (whose details were mentioned earlier) on the way down from the upper reservoir. Since this pump and its electrically driven motor are not desined to operate as a enerator unit (tables & show ri data for 9.5 & 5m elevations), the obtained data were used with the micro turbines readins of similar flow rates from the literature, (table 3) to indicate the obtained output. Water comin down from the upper reservoir was stored in the lower reservoir to be pumped up aain at the appropriate time. IV. RESULTS ND DISCUSSION In this work the obtained experimental results are presented for verification of the computational model and then the emphasis is placed on takin into consideration the workin parameters that affect the performance of hydro-storae systems with a note for the feasibility of the pumpin hydrostorae systems within the local framework, slihtly underlinin the available and established resources of hydro power in the reion. To distinuish between pump flow and pumped storae hydro it is important to identify the head as the available potential altitude in the storae reservoir and the flow rate as the correspondin flow out of the penstock into the turbine room. The SI unit for manetic field strenth H is /m. However, if you wish to use units of T, either refer to manetic flux density B or manetic field strenth symbolized as µ 0 H. Use the center dot to separate compound units, e.., m.. Verification of the computational model Fiure (3) shows the depiction of computational aainst the experimental results for available head aainst the existin flow rate. The fiure indicates the relation between the existin head and flow rate for both computational and experimental results at elevations of (5) and (9.5) meters. The results indicate ( %) deviation between the computed and experimental results for (5) and (4.433 %) for (9) meter head. Fiures (4) & (5) show the variation of head and flow rate with time, comparin the results obtained from the computational model with those acquired by the experimental ri. The curves indicate an inversely proportional relation with time for both cases of head and flow rate and at the same time, a comparison between the computational and experimental results. The maximum observed deviation between computed and experimental results for head was ( %) while for flow rate it was limited to (.08*0-4 %). It is concluded from considerin head and flow rate, which are the most important parameters in performance evaluation that the computational model performs satisfactorily and can be used for further parametric analysis. B. The observed effect of temperature Fiure (6) shows the effect of temperature variation on the flow rate. The fiure shows a sliht proportional chane in the flow rate with temperature chane. For a temperature chane of (40-0 ºC) which assumed to be approximatin the seasonal water temperature chane, a variation of 0.3 liters/min has been recorded. This is equal to ( %) of the total flow rate which in this analysis was restricted to (7899.) liters/minute. Fiure (7) shows the chane in the turbine output accordin to the temperature chane. The indication obtained from the fiure is that in the temperature rane ( T = 30 ºC) the power eneration is chaned by ( MW). This is related to the variation in the flow and thermal characteristics of water and the way they are affected by the restricted temperature chane and it enerally indicates a reduction in output results in case of hiher water temperature, for this temperature and flow rane. Fiure (8) shows the effect of temperature chane on the sum of the friction factors affectin the flow of water in the penstock to the turbine room. The fiure shows a relation that is inversely proportional, for the specified temperature rane of (30 ºC) a variation of ( f = ) has been recorded. C. More realistic analysis based on comparative head and flow rates for actual pumped storae hydro The acquired calculation skills were used to run a more realistic analysis based on much hiher flow rates (500, 000, 500 & 000 m 3 /hr), to check the deviations induced by temperature variation, effective for pumped storae hydro. Fiure (9) indicates the variation of flow rate for the recommended temperature chane (0 40 o C). It is shown that the increase in temperature leads to a correspondin increase in flow rate and for the considered rane of (0 40 o C) water temperature chane, induces the increase of (0.36%, 0.56%, 0.76% and 0.874%) in flow rate, respectively. This outlines the fact that the stored enery is consumed faster in summer in comparison to winter. This conclusion is considerable for manain storae release and can be accounted for by reducin the flow area to achieve equal flows despite different water temperatures. Consequently, this improves the enery storae manaement and uarantees a more reliable enery storae system. D. The effect of head on flow rate Fiure (0) shows the effect of head variation on the flow rate when other parameters are fixed. The relation is proportional and indicates that reduction in head leads to reduction in the flow rate. s shown in the fiure; for the available rane of almost ( h = 0 m) the variation induced in the flow rate amounts to (6.667%) reduction in the flow. The reduction is because of the chane in the kinetic enery of the flowin water inside the penstock, which is directly proportional to the potential head. E. Pumpin hydro-storae electricity eneration in the reion The followin discussion briefly outlines the potential for the application of pumpin hydro-electricity storae in the different application continencies for the reion. It is attempted to base the arument on facts and realities of the reion. The oal is to attempt to challene the complex problem of satisfyin the need and if possible exceedin the electricity demand even durin the peak hours. 07

4 International Conference on Machine Learnin, Electrical and Mechanical Enineerin (ICMLEME'04) Jan. 8-9, 04 Dubai (UE) Fiure () is constructed based on the available data from table (4), [3] to show the percentae of distribution of water resources in the reion. It is obvious from the fiure that Erbil overnorate with its extended suburbia dominates the water resources cateory and there is plenty of potential for small dam construction. This in effect means that pumpin hydroelectricity is a very attractive option to maintain these small reservoirs and promote their continuous power production. Fiure () shows the rowth of demand and the state of power eneration in the province of Erbil from 005 to 009, [0]. It is obvious from the raph that there is a soarin demand for electricity that is rowin by the year. The fiure also indicates that the power production has never been able to meet demand. The fact that the production of electricity shows some contradictin values when comparin the maximum produced amounts that should be able to meet the demand in the months of lower demand is related to the factors that affect the policies of power eneration. Water level issue is a very serious matter that can be properly boosted by the implementation of the pumpin hydro storae. The fact that there are (33) potential sites for water storae, as indicated in fiure (), fully supports the idea and when appropriately implemented it can be an exceptionally clean supportin sources of peak and backup electrical power. Fiures ( a & b) are based on the hourly readins for an averae day in the two most extreme months of the year in electric power demand, [0]. ccordin to the obtained data for the year 009, the hihest demand was recorded durin an averae day in the month of December while the lowest demand was observed durin an averae day in the month of October. Both raphs show that the period between to 6 M indicates the lowest demand. This period can be used to boost the storae or the potential for power eneration. Pumpin hydro-electricity storae can be used with the existin dams to redirect water from lower reservoirs to the main up stream storae area. The lower reservoir for the existin dams should be properly desined and be as environmentally friendly as possible. lso based on table (4) a sufficient number of water resources can be interconnected or individually employed for electric power eneration that durin the hours of lowest demand can be effectively reversed to work as a storae pumpin station. The available four hour time (-6 MW) indicated in fiures ( a & b) can provide the required time marin needed for both ideas discussed above. V. CONCLUSIONS. The rane and intensity of the parameters affectin the performance of a pumpin hydro-electricity storae system can be identified and calculated by usin the computational model developed in this work.. Increasin the temperature of water in the temperature rane (0-40 ºC) leads to 0.95% increase in the flow rate. 3. Increasin the temperature of water in the temperature rane (0-40 ºC) leads to (.848 kw) reduction in output power production at fixed flow rate. 4. Increasin the water temperature leads to a reduction in friction factor in the penstock connectin the upper and lower units. 5. The relation between head and flow rate is linearly proportional and it depends on the actual altitude of water in the upper reservoir. 6. There is plenty of potential (around 60 sites in Erbil province alone) for the application of pumpin hydro-electric storae systems. This indicates a level of storae that can play an effective role in supportin the power eneration durin the peak hours. ssumin (-5MW) at support from each of these sites can lead to (0-300 MW) of supportive power. These amounts to (5-40%) of demand for the month of December of 009. NOMENCLTURE Symbol Definition Unit Cross Section rea m Tank Cross Section rea m Orifice Cross Section rea m Gravitational cceleration m/s H, h Elevation (Head) m h eff Effect Head m m Mass of water k P Power Generation W PE Potential Enery J Q Flow rate of Water m 3 /s t Time sec. V Volume m 3 v bsolute Velocity of water m/s v Orifice Velocity of water m/s Greek letters Definition Unit ρ Density of water k/m 3 η Hydraulic efficiency Dimensionless factors Kt Km Kf Definition Total Loss Coefficient Minor Loss Coefficient Major Loss Coefficient REFERENCES [] Breeze, Paul, "Power Generation Technoloies", Paul Breeze. ll rihts reserved 005. [] Dell, Ronald M. and David. J. Rand, "RSC Clean Technoloy Monoraphs, Clean Enery", the Royal Society of Chemistry 004 [3] Directorate of Water Resources [Erbil Iraq] [4] Crampes, Claude and Michel Moreaux, Pumped storae and cost savin, enery economics 3 (00) [5] Bekele, Getachew and Getnet Tadesse, Feasibility study of small hydro/pv/wind hybrid system for off-rid rural electrification in Ethiopia, pplied Enery 97 (0)

5 International Conference on Machine Learnin, Electrical and Mechanical Enineerin (ICMLEME'04) Jan. 8-9, 04 Dubai (UE) [6] Morado, P.. and Helena M. Ramos, Dynamic effects in reversible hydro systems towards safety solution, International Journal of Enery & Environment, volume, issue 6, 00 pp [7] Lian, J. and Ronald G. Harley, Pumped storae hydro-plant models for system transient and lon-term dynamic studies, IEEE Conference 5-9 July, 00 [8] Warland, G., B. Mo and. Helseth, Handlin balancin power in a power market with a lare share of hydropower, IEEE Conference 9-3 June, 0. [9] Fanchi, John R. "Enery Technoloy and directions for the future", 004, Elsevier Inc. [0] Directory of Control and Distribution of Electricity in Erbil, data book, January Head (m) H 9.5 m experimen tal Time (min.) Fi. 4 depreciation of head with elapsed time (5 to 9.5 m) Fi. suested number of small dams to be constructed in the reion. Fi. 5 depreciation of flow rate with elapsed time (5 to 9.5 m) Fi. the layout of the experimental ri. Fi. 6 variation of flow rate with to water temperature at constant head Fi. 3 variation of head with the available flow rate (5 to 9.5 m) 09

6 International Conference on Machine Learnin, Electrical and Mechanical Enineerin (ICMLEME'04) Jan. 8-9, 04 Dubai (UE) Fi. 7 variation of enerated power with water temperature at constant head Fi. averae supply and demand load Fi. 8 variation of friction factor accordin to water temperature Fi. a demand load for the city of Erbil for December 0 th 009 Fi. 9 variation of flow rate with temperature chane at hiher flow rates Fi. b demand load for the city of Erbil for October 9 th 009 Fi. 0 relation between flow rate and head at constant temperature 0