|Fig. 1: Lombok Island, located on the Indonesian Archipelago, is flanked by fast moving, narrow straits. (Source: Wikimedia Commons)|
Marine energy is a subsector of renewable energy focused around capturing the kinetic motion of the ocean through waves and tidal flows. Like that of wind turbines, tidal and wave turbines are rotated not by wind but by the moving water of currents as it passes through the blades. Under the constraint of current marine energy technology, there is the capability of providing roughly 2-5% of the worlds end use energy consumption.  In fact, in the US alone tidal and wave energy has the potential to match the countrys current hydro-electrical power production of 10% of total US consumption, with tidal energy alone capable of supplying 3.5% of the total US needs.  Environmentally benign and nonpolluting, this source of energy surpasses conventional forms of hydroelectricity in that it doesnt completely obstruct water routes, thereby giving fish and marine life the ability to migrate through the area. Furthermore, the tides are relatively consistent and therefore provide a scheduled and reliable stream of energy, unlike wind energy with is dependent on variable conditions.
Indonesia has recently been seen in the global community as an ideal candidate for marine renewable energy. Due to its heavily exponential population growth and increased energy consumption requirements, the country has been dependent on oil for its main source of energy, however oils fickle prices paired with a relatively poor government has led to numerous blackouts across the country.  The result of this has been a switch in economics from energy-exporting to energy-importing, which has alarmed citizens and inspired an increasing desire to enact renewable energy projects.
A presidential decree made in 2016 stated that the new goal of the country was to have renewable sources contribute towards 17% of total national energy requirements by 2025, of which 5% must come from hydroelectric means.  Marine energy, and in particular tidal energy, has been a highlighting subject of research for the country as it has begun its campaign, due to the fact that the countrys geography is mainly narrow channels and straights in between island archipelagos, amplifying currents and providing multiple locations of possibility to exploit the tides.
Significant studies have been enacted to determine the energy potentials of these straights and channels in Indonesia, such as one area of interest, Lombok Island, shown in Fig. 1. When using a hydrodynamic model to simulate the current and tidal flow of the region, researchers can find the best tidal projects, done so by assuming peak flow speeds in various straits and channels, then determining optimized tidal array configurations to maximize energy capture.  Furthermore, estimates from 10 separate locations in Indonesia noted that the Alas Strait combined with the Riau Islands hold 1.26 × 1010 W of potential tidal power, nearly 70% of the total tidal potential measured from these scattered locations.  Given that the country's goal has been set to target marine energy to produce roughly 3.1 × 109 W by 2025 and 4.5 × 109 W by 2030, these locations certainly provide the potential to reach these figures.  Lastly, given that Indonesia's total energy needs in 2016 were 175 MTOE = 7.33 × 1018 J, corresponding to an average power of 
|7.33 × 1018 J/y
60 sec/min × 60 min/h × 24 h/d × 365d/y
|=||2.32 × 1011 W|
these locations for tidal energy capture would go most of the way to meeting the 5% hydroelectric goals (1.16 × 1010 W).
Creating programs and developments for marine energy will be one of the country's first major steps towards increasing renewable energy sources, while other benefits will be achieved as companies can manage offshore surveys, perform environmental impact studies, install electro-mechanical components, and provide system integration testing. This data will provide Indonesia with information towards improving the efficiency and effectiveness of new marine energy ventures in different domestic locations. Overall, marine energy is an exciting new endeavor from an economically growing company, helping to provide the world with optimism towards a hopeful future of complete renewable energy.
© Charles Skolds. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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 D. Gielen, D. Saygin, and J. Rigter, Renewable Energy Prospects: Indonesia," International Renewable Energy Agency (IRENA), March 2017.
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