Okawachi Pumped Storage Power Station

{{coord|35.1281691|134.7148408|display=title}}

{{Infobox dam

| name = Okawachi Pumped Storage Power Station

| name_official =

| image = File:Ota Dam (Hyogo) lake 2.jpg

| image_caption = View of the upper reservoir

| image_alt =

| country = Japan

| location = Hase, Kanzaki district, Hyōgo

| status = O

| construction_began = 1980

| opening = 1992–1995

| demolished =

| cost =

| owner =

| operator = KEPCO

| res_name = Ota Reservoir

| res_capacity_total = {{convert|10150000|m3|acre.ft|abbr=on}}

| lower_res_name = Hase Reservoir

| lower_res_capacity_total = {{convert|9604000|m3|acre.ft|abbr=on}}

| plant_pumpgenerators = 2 x 329, 2 x 331 MW reversible Francis turbines

| plant_turbines =

| plant_pumps =

| plant_hydraulic_head = {{convert|394.7|m|ft|abbr=on}}

| plant_capacity = {{convert|1280|MW|abbr=on}}

| plant_capacity_factor =

| website =

| extra =

}}

File:Okawachi power station substation 1.jpg

File:Ota Dam 1976.jpg

The {{nihongo|Okawachi Pumped Storage Power Station|大河内発電所|Ōkawachi Hatsudensho|lead=yes}} is a large pumped-storage hydroelectric power station in Kamikawa Town in the Kanzaki District of Hyōgo Prefecture, Japan. With a total installed capacity of {{convert|1280|MW}}, it is one of the largest pumped-storage power stations in Japan.{{cite web|title=The Electric Power Industry in Japan|url=http://www.jepic.or.jp/en/data/EPIJ2012Japan%20data.pdf|publisher=Japan Electric Power Information Center, Inc. (JEPIC)|accessdate=16 November 2015|archive-date=2 August 2014|archive-url=https://web.archive.org/web/20140802064145/http://www.jepic.or.jp/en/data/EPIJ2012Japan%20data.pdf|url-status=dead}} The facility is run by the Kansai Electric Power Company (KEPCO).{{cite web|title=発電所詳細表示：大河内(上池／下池)|url=http://www.jepoc.or.jp/hydro/index.php?_w=usData&_x=detail2&pp=2&OwnerNo=006&AreaNo=06&RiverSys=6200&fd=1|publisher=Electric Power Civil Engineering Association|accessdate=12 November 2015}} The power plant started operation in October 1992 and all four units were commissioned by June 1995.{{cite web|title=Kansai Electric Power Okochi power plant |url=http://www.suiryoku.com/gallery/hyogo/ookawati/ookawati.html|publisher=Suiryoku|accessdate=18 November 2015|language=Japanese}}

Like most pumped-storage facilities, the power station uses two reservoirs, releasing and pumping as the demand rises and falls.

The Ota artificial lake is the upper reservoir, and is contained by five dams, numbered Ota Dam 1 to 5. The reservoir is fed by the river Ota. Hase reservoir is the lower reservoir and is contained by the Hase Dam. The upper Ota dams are rock-fill dams, while the lower Hase Dam is a gravity dam.{{cite web|title=Hase Dam (Hyogo)|url=http://damnet.or.jp/cgi-bin/binranA/enAll.cgi?db4=1518|publisher=The Japan Dam Foundation|accessdate=16 November 2015}}

The upper Ota reservoir was built during the Meiji period to feed the {{nihongo|Minamioda conventional hydroelectric power plant|南小田第一発電所|Minamioda Dai Ichi Hatsudenjo}}. The plant started operation in December 1909 with a maximum output of 1450 kW.{{cite web|title=関西電力の水力発電所 (Hydroelectric Power Plants of Kansai Electric Power Co.)|url=http://www.kepco.co.jp/corporate/energy/water_power/plant/list.html|website=www.kepco.co.jp|publisher=KEPCO|accessdate=23 November 2015}}{{cite web|title=発電機出力および発電電力量にかかるデータ（１２０発電所）|url=http://www.kepco.co.jp/ICSFiles/afieldfile/2007/02/23/0214_1j_05.pdf|website=www.kepco.co.jp|publisher=KEPCO|accessdate=23 November 2015|archive-date=23 November 2015|archive-url=https://web.archive.org/web/20151123143335/http://www.kepco.co.jp/ICSFiles/afieldfile/2007/02/23/0214_1j_05.pdf|url-status=dead}} {{nihongo|A second conventional hydroelectric power plant|南小田第二発電所|Minamioda Dai Ni Hatsudenjo}} with a generation capacity of 720 kW was added in May 1919.

The enlargement of the Ota reservoir and the building of the new Hase lower reservoir was implemented by Kansai Electric Power Company, with start of operation of the new pumped storage plant in 1992. The plant reached the current capacity in 1996 with all the four units in operation.

The power station employs four generation/pumping units. Two of the units are adjustable speed systems manufactured by Hitachi, allowing for a rapid variation of power levels during both pumping and generation. This allows the power station to respond more effectively to grid requests for the balancing of demand and supply, a role which is usually performed by thermal power plants.{{cite web|title=Electric power supply systems that contribute to low-carbon society|url=http://s3.amazonaws.com/zanran_storage/www.hitachi.com/ContentPages/2533604279.pdf|publisher=Hitachi Review|accessdate=16 November 2015|date=2011}} These units were the first large-capacity adjustable-speed pumped storage hydroelectric systems in the world.{{cite web|last1=Kita|first1=E.|title=400-MW adjustable-speed pumped-storage hydraulic power plant|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=3628410|publisher=Hitachi Review|accessdate=16 November 2015}}

Ota I Dam.jpg|Ota Dam 1

Ota II Dam.jpg|Ota Dam 2

Ota V Dam.jpg|Ota Dam 5

Hase Dam (Hyogo) 3.jpg|Hase Dam