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A small hydro power (SHP) system in Taiwan using outlet-water energy of a reservoir: System introduction and measured results

A small hydro power (SHP) system in Taiwan using outlet-water energy of a reservoir: System introduction and measured results
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   1    Abstract -- This paper introduces a small hydro power (SHP) system using outlet-water energy of a reservoir in southern Taiwan. The rated capacity of this SHP system is 8.75 MW and the generated power is delivered to the 69-kV system of Taiwan Power Company (TPC). Since the studied Reservoir Wushantou with abundant water offers available water for irrigation of farmlands, industry, people’s livelihood, etc., the generated power of the SHP system is very stable and continuous as comparing with the intermittent generated powers from wind turbine generators and photovoltaic arrays. The studied SHP plant is also one of the investments of the multiple managed businesses of the largest farmland irrigation association in Taiwan, Chia-Nan Farmland Irrigation Association. This paper presents some details of the finished SHP system including engineering, electricity prices, capital cost, revenue of power generation, etc. Some measured results of the SHP system including harmonics and flickers are also demonstrated.  Index Terms -- small hydro power (SHP), reservoir, measurements, capital cost, harmonics, flickers. I. I NTRODUCTION  MALL hydro power (SHP) and micro hydro power (MHP) systems [1] have gained increasing attractions due to their lower prices and easy installation for generating electrical power without producing air pollution, ashes, acidic or poisoned materials, green-house gases, etc. Both SHP and MHP systems can also be considered as environmentally friendly renewable- energy sources since they can be sized and designed to limit the interference with river or canal flow. The irrigation canals can also be used to store a large amount of sudden heavy raining water to minimize calamity due to bad weather conditions. The employed generators for SHP This work was supported by Council of Agriculture, Executive Yuan, Taiwan under Grant 95AS-4.1.1-IE-b2. Li Wang, Dong-Jing Lee, Jian-Hong Liu, Zan-Zia Chen, and Zone-Yuan Kuo are with the Department of Electrical Engineering, National Cheng Kung University, Tainan City 70101, Taiwan (e-mail: Wei-Jen Lee is with the Energy Systems Research Center (ESRC), The University of Texas at Arlington (UTA), Arlington, TX 76019, USA (e-mail: Jin-Shyi Shyu, Cheng-Mei Chen, and Shen-Syi Chiu are with Chia-Nan Farmland Irrigation Association, Tainan City, Taiwan. Ming-Hua Tsai, Wei-Taw Lin, and Yuan-Chung Li are with the Department of Irrigation and Engineering, Council of Agriculture, Executive Yuan, Taipei City, Taiwan. and MHP plants for power generation may be induction generators or synchronous generators with field excitation. The small- capacity permanent-magnet generators (PMGs) can also be used for power generation of SHP or MHP systems. With the fast development of power semiconductor devices, the generated power from SHP and MHP systems can be easily converted to stable power sources with excellent power quality using well-designed IGBT-based power converters and power inverters embedded with digital control systems. From the historical view of the various applications of MHP and SHP systems, a simple and economical method for controlling a three-phase, 7.5 kW, 1500 rpm self-excited induction generator of a stand-alone MHP plant respectively using an IGBT-based chopper for unity-power-factor loads and a switched-capacitor-based VAR compensator for reactive loads was shown in [2]. Transient responses of an induction generator employed as distributed-system generation (DSG) unit of a SHP plant subject to disturbances on the utility’s transmission and distribution systems were presented in [3]. Regarding power generation and tests of SHP and MHP systems, the applications of load control using a novel frequency and voltage sensing device were proposed in [4]. The test system in [4] was an 18 kW, single-phase, 230 V, 50 Hz, MHP set at Polmood, UK while the fuzzy controllers were also developed to control the frequency without distorting the voltage waveform of autonomous renewable-energy systems. Design criteria to find the value of excitation capacitors and the loading on 1-10 kW induction generators for SHP applications in Sri Lanka was explored in [5]. Optimal dispatch of 18 identical 700-MW hydro generating units of Itaipu 12.6-GW hydro plants located on River Parana of South American using dynamic programming model designed to determine the number of hydro generating units during a single day on an hourly basis was presented [6]. An hourly-discretized optimization algorithm to identify the optimal daily operational strategy for a wind-hydro power plant through the utilization of water storage ability to improve wind park operational gains and to attenuate active power output fluctuations was reported [7]. Dynamic performance of three identical SHP systems consisting of a 2.9-MVA power transformer, a 2.5-MW induction generator, and a power factor correction bank for each set integrated into A Small Hydro Power (SHP) System in Taiwan Using Outlet-Water Energy of a Reservoir: System Introduction and Measured Results Li Wang, Senior Member, IEEE  , Dong-Jing Lee, Jian-Hong Liu, Zan-Zia Chen, Zone-Yuan Kuo, Wei-Jen Lee, Fellow ,  IEEE  , Jin-Shi Hsu, Cheng-Mei Chen, Shen-Syi Chiu, Ming-Hua Tsai, Wei-Taw Lin, and Yuan-Chung Li  S 978-1-4244-4241-6/09/$25.00 ©2009 IEEE   2 grid under the operational conditions of load importing and exporting, sequentially starting, and a three-phase balanced fault was presented in [8]. The use of two voltage-source inverters (VSI) for control both field weakening operation and for control over twice the rated speed range of a 600-kW doubly-fed induction generator for SHP applications was shown in [9]. Optimal planning of multiple micro-scale hydro generating units over a catchment area consisting of 16 potential installation sites at the upper Ganga basin located in Northern India to extract maximum possible energy per-unit investment cost was presented in [10]. Arrangement of proper reserve capacity to handle intermittent energies such as wind energy and SHP energy was presented while capacity expansion in regional power system during a not long period to perform a reasonable energy restructuring to enhance generating efficiency of the studied system was proposed in [11]. The economic analyzed results of several canals of Chia-Nan Farmland Irrigation Association (FIA) in Taiwan was carried out in [12] for considering future MHP installation. Installation and field measurements of a MHP system with a PMG using the irrigation water flowing in a ditch of a FIA in Taiwan was demonstrated in [13]. A new finished MHP system with two parallel-operated self-excited induction generators has become a good candidate for sustainable Microgrid development in rural electrification of Africa [14]. The contribution of this paper is that it presents the details of a commercial 8.75-MW SHP system using outlet-water energy of Reservoir Wushantou in southern Taiwan. Both economic analysis of investing the SHP system and some measured electrical results such as active power, harmonics, and flickers of the SHP system are also shown to demonstrate the advantages of the SHP system. This paper is organized as follows. Section II introduces the details of the studied SHP system. Section III shows some measured results of the studied SHP system. Section VI draws specific conclusions of this paper. II. I NTRODUCTION TO T HE S TUDIED SHP  SYSTEM  A. Chia-Nan Farmland Irrigation Association Fig. 1 shows the distribution chart of 17 Farmland Irrigation Associations (FIAs) in Taiwan. The FIAs in Taiwan that has operating history of 390 years hold the privilege of 70-75% water resources of Taiwan. The largest FIA and one of the six urban-rural style FIAs in Taiwan, Chia-Nan FIA, has the farmland area of 78422 hectares and it is about 20.66% of the total farmland area of 379528 hectares in Taiwan. The management area of Chia-Nan FIA locates in the south-western part of Taiwan. It covers Chiayi County, Chiayi City, Tainan County, and Tainan City. It is bounded by the Mountain Central range to the east, River Peikang to the north, River Erhjen to the south, and Strait Taiwan to the west. The climate is subtropical with an average temperature of 21-24 ° C and an annual average rainfall of 1600 mm which 80% of total concentrated in the wet season from May to September. All FIAs in Taiwan need to obtain sufficient incomes from different ways in order to successfully operate since agricultural techniques and developments can not catch up with the fast growth of international scientific and technical developments. Moreover, the agricultural technology and products that are inferior to the modern 3C devices can not obtain higher budgets, significant attraction, and outstanding breakthrough in the whole world today. To effectively raise and manage all possible incomes of FIAs in Taiwan from different ways and methods, several related topics are currently proposed and involved. For example, (a) revenue obtained from generated power of SHP and MHP systems, (b) transfer of planted bamboo neighboring water resources to carbon, (c) extension of distribution water services, (d) installation of base stations on buildings that can be rented by telecommunication companies, (e) deployment of pipes for transferring gas, oil, water, etc., (f) set up of large signboards that can be rented by private companies, (g) prevention and cure of water-quality pollution, (h) water collection and drainage in district areas, (i) manage and sell of mineral waters, etc. Fig. 1 Geographic distribution chart of the 17 Farmland Irrigation Associations (FIAs) in Taiwan  B. Introduction to Reservoir Wushantou Reservoir Wushantou is located on the borders of Lioujia and Guantian Townships of Taiwan. Looking down from the sky, one can see the intricate and zigzagging shore, resembling the appearance of corals. In previous times, this   3 place was called “Coral Lake”. This lake is formed from the convergence of over 30 rivers, and the water surface area is close to 1300 hectares. There are close to 100 small islands and peninsulas on the lake. It is surrounded by over 4700 hectares of mountain forests. This exquisitely beautiful scenery is extremely enchanting. Reservoir Wushantou not only irrigates over 150000 hectares of farmlands, it also promotes Tainan County's tourism. Nowadays, Reservoir Wushantou is connected with Reservoir Zengwen, located in the upper reaches of the River Zengwen, and they both provide hydroelectric power and water for the residents and industries of the greater Tainan area. C. SHP System of Reservoir Wushantou The building project of the studied SHP system of Reservoir Wushantou started in October 2000 and finished in July 2002. The license of power generation of the SHP system was obtained from Ministry of Economic Affairs, Taiwan, on July 30, 2002 while the commercial-operation license was obtained on August 27, 2002. The studied SHP system has the net peak-power output capacity of 8.75 MW and the annual generated electric energy of 421.7 GWh. The civil-engineering subsystems of the SHP system cost US$ 3,477,000, and it includes the factory building which is a semi-underground type with dimensions of 25 m ×  25 m ×  33.9 m, a steel pipe which has the length of 52.4 m and the diameter of 3.2-3.6 m, and a tail water construction which has the dimensions of 25 m ×  5.2 m ×  4.4 m. The power-engineering subsystems of the SHP system cost US$ 1,498,711, and it includes a three-phase 6.6/69-kV step-up transformer which is an outdoor type with dimensions of 20 m ×  8 m and over-head 6-km transmission lines to 69-kV Longtien and Nanhua line of TPC. Fig. 2 shows the electromechanical-engineering construction diagram of a water turbine (vertical-shaft Kaplan type with designed water head of 24 m and designed water flow rate of 41 m 3  /s) and a synchronous generator (semi-umbrella vertical type of three-phase, 60 Hz, 8.75 MW). This part costs US$ 5,785,000. The total capital cost of the SHP system is around US$10,790,720. The employed synchronous generator of the SHP system has the followings on its nameplate: three-phase, nominal power of 9750 kVA, rated voltage of 6.6 kV, power factor of 0.9 lagging, rated frequency of 60 Hz, rated rotational speed of 300 rpm, pole number of 24, inertia of 280 Nt ⋅ m 2 , insulating class of F, thermal class of B, rated exciting current of 785 A, and rated exciting voltage of 65 V. Fig. 3 shows the top view of the studied SHP system neighboring the srcinal outlet-water cannel of Reservoir Wushantou. The top blue part shown in Fig. 3 is the outlet- water cannel of the Reservoir Wushantou and the outlet water injects into a large canal for irrigation of farmlands. The orange path at the bottom of Fig. 3 represents the bypass of the outlet-water cannel. The water of Reservoir Wushantou is introduced into the inlet steel pipe of the SHP system. The red circle at the middle part of the orange bypass is the water turbine-synchronous generator set inside a semi-underground factory building. After driving the water turbine of the SHP system, the used water is sent to a tail water channel to combine with the water in the blue channel shown in Fig. 3. Fig. 2 Construction diagram of water turbine and synchronous generator of the studied SHP system   Fig. 3 Top view of the complete SHP system   4  D. Economic Benefits of The Studied SHP System After negotiating the prices of generated electricity of the SHP system between TPC and Reservoir Wushantou, the calculated single price and the contract price are respectively listed as below. (a) Calculated single price. Capacity price is NT$ 2.154/kWh. Summer energy prices are NT$ 3.0237/kWh for peak, NT$ 1.6432/kWh for half peak, NT$ 0.8142/kWh for Saturday half peak, and NT$ 0.5194/kWh for off peak, respectively. Non-summer energy prices are NT$ 1.5861/kWh for half peak, NT$ 0.7570/kWh for Saturday half peak, and NT$ 0.4713/ kWh for off peak, respectively. (b) Contract single price including tax. Capacity price is NT$ 2.154/kWh. Summer energy prices are NT$ 3.1749/kWh for peak, NT$ 1.7254/kWh for half peak, NT$ 0.8549/kWh for Saturday half peak, NT$ 0.5454/kWh for off peak, respectively. Non-summer energy prices include NT$ 1.6654/kWh for half peak, NT$ 0.7949/kWh for Saturday half peak, and NT$ 0.4049/ kWh for off peak, respectively. The exchange rate for one US$ (US Dollars) is equal to 33.5 NT$ (New Taiwan Dollars) when writing this paper. Fig. 4 shows the economic benefits of the power generation of the studied SHP system of Reservoir Wushantou from January to September 2007. The curves shown in Fig. 4 represent the quantities of electric-energy production in kWh (A), selling of electric-energy in kWh (B), cash of selling electricity (C), profits (D), cash return (E), respectively. It can be clearly observed from Fig. 4 that the both profits and cash returns of the SHP system increase with the increase of the operation time. Table I lists the scheduled operation results, practical operation results, and cash-return results of the studied SHP system of Reservoir Wushantou from the beginning operation in August 2002 to December 2007. Most the units for cashes or capital costs in Table I are in NT$ and only the results listed in the last column of Table I show the cash-return results in US$. It is worth noting that the low electric-energy productions in 2003 and 2004 were due to no power generation during the low-water seasons. These seasons were from April to June and November in 2003 as well as from January to June in 2004. It can be clearly seen from the results listed in Table I that the practical operation results can catch up with the scheduled operation results. Although the practical operation results is lower than the schedule operation results, they are close and the differences could be due to some unexpected shutdowns of the SHP system, severe weather conditions such as typhoons, low rainfall seasons, etc. Comparing to the total capital cost of US$ 10,790,720 listed in the previous subsection and the total cash-return results listed in Table I, the payback year of this SHP system could be as low as 10 years. This low value can compete with the one of wind turbine generators installed in a good wind farm using intermittent wind energy. Fig. 4 Operation results of the SHP system from January to September 2007  III. A NALYSIS OF F IELD M EASURED R ESULTS  To demonstrate stable power generation and good power quality of the studied SHP system, the results of electrical quantities, harmonics, and flickers of the SHP system from 11:00 am, September 22, 2006 to 9:25 am, September 31, 2006 were recorded using two intelligent power-system recorders. During the 39-day measurements, the duration of the only one low-power output of the SHP system was due to the regular arrangement of decreasing water for irrigation of farmlands. Fig. 5 shows the measured voltage, current, active power, reactive power, apparent power, and power factor at the low-voltage side of the step-up transformer of the SHP system. Table I S CHEDULED AND P RACTICAL O PERATION R ESULTS OF R ESERVOIR W USHANTOU SHP   S YSTEM F ROM A UGUST 2002  TO D ECEMBER 2007 Year Schedule Operation Results Practical Operation Results Cash-Return Results Energy Production (kWh) Profits of Selling Electricity (NT$) Net Profits (NT$) Energy Production (kWh) Profits of Selling Electricity   (NT$) (A) Net Profits (NT$) (B) Depreciation (NT$) (C) Sum (C) = (A) + (B) (NT$) [US$] 2002 27,020,432 37,483,292 10,397,696 10,774,394 12,929,832 313,879 4,710,467 (5,024,346) [150,600] 2003 32,910,700 40,340,018 12,458,416 23,067,100 29,849,200 8,421,290 14,446,692 (22,867,982) [685,450] 2004 33,809,850 42,432,099 17,890,439 26,379,406 33,049,026 10,965,154 14,451,380 (25,416,534) [761,840] 2005 36,163,000 45,347,522 20,992,227 36,775,200 46,951,242 23,260,316 14,502,948 (37,763,264) [1,131,924] 2006 41,520,000 50,436,648 23,094,954 50,473,500 63,452,486 38,907,832 14,502,948 (53,410,780) [1,600,946] Total 171,423,982 216,039,579 84,833,732 147,469,600 186,231,786 81,868,471 62,614,435 (144,482,906) [4,330,762]   5   Fig. 5 Measured electrical quantities of the SHP system It is found from Fig. 5 that the voltage is varied between 6.6 kV and 7.0 kV while the average voltage is around 6.85 kV. Both waveforms of current and active power are similar, and the generated maximum and minimum active powers (currents) are 9.5 MW (850 A) and 5 MW (450 A), respectively. Since the output power factor of the SHP system is kept around 0.96 lagging, the delivered reactive power of the SHP system follows the generated active power to vary between 1400 kVAR and 2600 kVAR. Fig. 6 (Fig. 7) shows the results of time-domain total harmonic distortion of voltage (current), probability distribution, and 95% cumulative probability of the SHP system using the recorded voltage (current) data shown in Fig. 5. It is found that the total harmonic distortion of voltage (THD V ) and current (THD I ) under 95% cumulative probability are 0.707% and 2.349%, respectively. Both values are obviously lower than the grid-connection code of TPC of 5% and they exhibit good power-quality results. Fig. 6 Results of total harmonic distortion of voltage of the SHP system
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