Implementation of water energy has a long history of technological development. The first waterwheels were developed and became the main energy source during the Middle Ages and were still the main source of energy until the 19th century, which was replaced by steam engines. Over the past few centuries hydropower has been exploited for the process of milling grain into flour. Hydropower mills appeared in the Roman era of the 3rd and 4th centuries, which later developed for irrigation systems driven by waterwheels.
In the early days of its development, generally waterwheels were used is undershot type (water passed from under the propeller of the wheel), the undershot type of wheel was easy to install and mostly used directly in river flow. In the late middle ages, these waterwheels became a source of energy for a wider range of uses, including pumps, forging machines, mills, sawmills, and lathes
At the end of the middle ages the development of the waterwheel was increasing, with the discovery of the overshot type waterwheel (water flowing from above the wheel), this type of waterwheel was more efficient because it used greater energy from the flow of water. Overshot waterwheels are the basis of modern turbines.
John Smeaton, a British Scientist, Civil and Mechanical Engineer in the 17th century, calculated that the undershot wheel type uses 22 percent of the energy in the water flow, while the overshot wheel is capable of producing 63 percent (efficiency). The development of the overshot type waterwheel continues to grow rapidly, one of which is to provide electrical energy, but now waterwheels have been replaced by various types of water turbines that have better efficiency.
In some countries hydropower still plays an important role in providing electrical energy. In Indonesia, water turbines were first introduced by the Dutch in the late 19th century. Hydropower plants were installed in almost all parts of Indonesia to provide electrical energy for processing facilities in plantations, mineral mining, and supplying electricity to colonial settlements. In West Java, one of the main tea plantation areas in Indonesia, the first water turbines were installed between 1880–1890. At that time the turbine was coupled directly with the tea roller machines and other processing machines in the factory, but did not directly drive the electric generator. With the advancement of turbine and generator technology, hydropower plants to generate electricity began to be built.
In 1910 about 40 private tea plantations had hydroelectric power. In 1925 there were around 400 hydropower plants with a total capacity of 17,000 HP (12.5 MW), where the capacity of each generator ranged from 40 – 200 HP (30 – 150 kW). At that time generating electricity using fuel oil was 5 times more expensive than hydroelectric power.
Since 1970s the number of hydropower plants left behind by the Dutch era that are still operating has remained low. Most were left without maintenance and repair. The main cause was mostly due to economic reasons where diesel-fueled generators at that time were considered more economical and easy to maintain, compared to hydropower plants, along with the cheap price of fuel due to large government subsidies.
The following are examples of a Dutch heritage Hydroelectric Power Plant which is still in operation today :
- PLTA Plengan, Kab.Bandung-Jabar, 6.87 MW, operated since 1922.
- PLTA Lamajan, Kab.Bandung-Jabar, 3 x 6.5 MW, operated since 1925.
- PLTA Cikalong, Kab.Bandung-Jabar, 19.20 MW, operated since 1925.
- PLTA Dago benkok, Bandung-Jabar, 3.2 MW, operated since 1925.
- PLTA Kracak, Bogor-Jabar, 3 x 6.3 MW, operated since 1926.
- PLTA Ketenger, Purwokerto-Jateng, 2 x 3.5 MW, operated since 1939.
- PLTM Salido Keci, Painan-Sumbar, 1 MW, operated since 1913.
- PLTA Ubrug, Sukabumi-Jabar, 18.26 MW, operated since 1923
- PLTA Tes, Rejang Lebong -Bengkulu, 1.2 MW, operated since 1923.
- PLTA Mendalan, Malang-Jatim, 2 x 5.6 MW, operated since 1927.