4.2.1. Wind Energy

Wind energy is the type of energy that uses the conversion of wind speed into a useful source of power, and it can be used for multiple purposes, such as electricity generation, mechanical power wind turbines, water-driven wind turbines, or ship propellers [26]. Wind energy is one of the renewable energy innovations, as it does not contribute to air pollution or greenhouse gases and has a slight impact on the climate.

The use of wind power as an energy source in Indonesia has great potential for further growth, especially in coastal areas where the wind is quite abundant. According to the previous research, Indonesia has an estimated total potential for onshore wind energy of 9.3 GW. With the range of wind speeds between 2 and 6 m per second, Indonesia is suitable for installing small-scale (10 kW) and medium-scale (10–100 kW) wind-driven generators [27]. Indonesia has installed five units of windmill generators across the country each with a capacity of 80 kW and seven other units with the same capacity have been established in four places, North Sulawesi, the Pacific Islands, Selayar Island, and Nusa Penida in Bali [28]. Several wind-based power plants, namely, Sidrap, Tanah Laut, and Jenepoto, have currently been under construction, while the ones in Sukabumi, Banten, and Bantul are currently being considered to be placed under construction planning [28].

Price is one of the biggest obstacles that Indonesia faces in installing wind energy. The initial cost of developing wind energy is very high, particularly with the use of offshore wind turbines. IRENA suggests that it costs about US\$3–US\$4 million per megawatt (MW) to install offshore wind turbines compared to geothermal power plants that cost about US\$2–US\$3 million [29].

However, wind energy has some issues associated with the geographical locations the jeopardises the consistency of supply, as pointed out by a participant,

*"* ... *indeed, we know that it [wind] is a promising form of energy in our country [Indonesia]. But its intermittent nature, makes it hard to provide electricity 24/7. It generates unstable and fluctuating electricity, and good source of wind power is only available in certain parts of our country [Indonesia]".* (FI)

Another difficulty is caused by the availability of other renewable energy sources available in Indonesia, such as geothermal, hydropower, biomass, and solar, which makes the cost analysis method challenging to carry out [29].

#### 4.2.2. Solar Energy

Solar energy is a source of renewable energy that uses the power of the sun to produce electricity. Globally, solar energy has the fastest and highest growth compared to the rest of renewable energy types. It is currently considered as one of the most promising sources of clean, renewable energy and has greater potential than any other energy source to solve the world's energy problems.

As Indonesia is a tropical country situated on the equator line, the country has an abundant capacity for solar energy. Many areas of Indonesia have very strong solar radiation with average daily radiation of approximately 4 kWh/m<sup>2</sup> [27]. According to the report from Directorate of New and Renewable Energy (Ditjen EBTKE) in 2018, Indonesia has the potential to harness solar energy of up to 207.8 gigawatts peak (GWp) [30]. However, as of 2019, Indonesia has only installed 25.19 megawatts (MW), which is mainly used to meet energy demand in rural areas, including lighting for public service areas and places of worship [28]. The Institute for Energy Economics and Financial Analysis (IEEFA), an energy research institute, has reported that about 48 MW of solar power is currently under construction and about 326 MW is under construction planning [31].

Indonesia is still far behind other ASEAN countries in solar power utilisation. Thailand has 2.6 GW of installed solar capacity and the Philippines 868 MW of installed solar capacity [32]. Vietnam is also working on an expansion of more than 3000 MW in solar and wind power capacity by 2019 and 2020, and Malaysia is targeting an additional 3000 MW in 2020 [33].

There are many obstacles to the implementation of solar energy in Indonesia. One of them being the high prices of the solar cell, including the solar panels, inverters, batteries, wiring, installation, and battery storage [33]. This situation not only impacts financial institutions to provide resources to implement this program but also limits local communities' confidence and interests in using this system due to its exorbitant costs. Because of that, the implementation of this program is highly dependent on government funding. Despite its huge potential, a solar panel is very dependent on sunlight to effectively capture solar energy. Even though it can capture the energy during cloudy and rainy days, it can also give measurable technical effects on the energy system. Due to its intermittent nature, solar energy might be more suitable for a household scale, but it might not be the best option for a larger scale energy system. This is emphasised by one of the participants:

*"It's fortunate that being in the equator, we [Indonesia] are blessed with warm climate all year round. We have the potential to develop solar energy. However, much like wind, it is intermittent and it [solar] will require storage systems to generate electricity after daylight".* (DK)

#### 4.2.3. Ocean Energy

Ocean energy, or sometimes referred to as marine energy, is a type of energy that is carried by ocean's elements, such as ocean's tide, wave, salinity, and temperature. Each one of these elements can be exploited as different types of energy, namely, tidal energy, wave energy, salinity gradient energy, and ocean thermal energy conversion (OTEC). Wave energy converts the ocean waves to produce electricity, while tidal energy harvests the power that was produced during high and low tides [34]. Salinity gradient energy can generate electricity due to the difference in salt concentration between freshwater and seawater [35]. OTEC converts the temperature difference between cold seawater and warm surface seawater, typically at around 800 to 1000 m of depth, to produce electricity [36].

Indonesia is the world's largest archipelago with 70% of its area is covered by ocean, thus it has the largest potential of ocean energy. According to the research from the Indonesian Ocean Energy Association (INOCEAN), the potential of ocean energy resource

that can be exploited is around 92.2 GW. The majority of its potential is coming from OTEC, with 43 GW of resource potential, followed by tidal and wave energy with 4.8 and 1.2 GW of resource potential, respectively. Despite its considerable amount of potential for harnessing ocean energy, the installed capacity for ocean energy is only 0.3 MW or 0.002% of the total energy use [24]. As of 2020, ocean energy is still under the stage of Research and Development, and this type of renewable energy has yet to be commercially developed in Indonesia [28].

*"* ... *unlike solar and wind, ocean energy can provide electricity throughout the entire day since it does not require the sun or the wind to harness electricity. Nevertheless, ocean energy is still rather far from the full commercialisation in Indonesia".* (DK)

#### 4.2.4. Biomass

Biomass energy is one of the types of natural renewable energy that are generated from organisms, and it mostly comes from farm crops and residues, forest waste, farm foods, and animal waste [37]. Biomass is the only renewable energy that can be used to generate three types of fuels: liquid, solid, and gas. A proper biomass energy development could also reduce not only energy issues but also waste management issues.

As an agricultural country, the potential of biomass resources in Indonesia is relatively abundant. According to the report from Directorate of New and Renewable Energy in 2018, Indonesia has a potential of harnessing 32.6 GW of biomass energy [24]. However, only 167.54 MW of biomass energy in Indonesia has now been properly exploited. Currently, Indonesia's estimated total biomass production is around 146.7 million tons, which is equivalent to 470 gigajoules per year (GJ/y) [38]. Most of the biomass energy source comes from the rice residue and rubberwood, which contributes to 150 GJ/y and 120 GJ/y, respectively [38]. These are followed by sugar residues (78 GJ/y), palm oil residues (67 GJ/y), and other types of residues (20 GJ/y) [38]. Such biomass sources can help supply both heat and electricity to rural households and sometimes small-scale industries.

Bioenergy, in general, has faced similar problems as other renewable energy sources. One of the primary issues is the high investment cost for bioenergy installations, as claimed by one participant:

*"* ... *while Indonesia has an abundant amount of biomass energy that can be utilised to generate liquid, solid, and gas, it is still expensive to invest in and the lack of support from financial institutions has hindered its growth".* (DK)

Part of the reason is that bioenergy deployment feasibility studies are mostly not attractive for bank loans [39]. From the perspective of technology, the reliability and efficiency of the existing technology for biomass energy is still lower than those of fossil fuels [39], hence hindering bioenergy development.

#### 4.2.5. Hydropower

Hydropower energy is a type of renewable energy source that extracts energy from flowing water, to produce electricity. As a potential future source of energy, hydropower has become an increasingly attractive choice for small capacity of the renewable energy. This type of energy, as well as other renewable energy sources, are the clean energy sources as they emit a negligible amount of greenhouse gas.

Hydropower is one of Indonesia's large-scale, commercially viable, renewable energy sources. According to the report from the Nippon Koei, the hydropower capacity in Indonesia is projected at around 26,321 MW [40]. Currently, the installed capacity of hydropower is 4938.64 MW from various hydropower plants all across the nation; the largescale plants are operated by the state-owned electricity company (PLN), and many smallscale plants are owned by small enterprises. According to 2019–2028 Electricity Supply Business Plan issued by PLN, it has been reported that 5956 MW of hydropower capacity is currently under construction scattered in many places, while the new 16,027 MW of

potential capacity has just been built as of 2018 and is considered for being placed under construction planning [24].

To date, the hydropower energy in Indonesia is still the most established and the most utilised small-scale renewable energy source, particularly for the rural areas. Hydropower systems provide unique operational versatility in that they can adapt to sudden fluctuating demand for electricity, which means that it can be tailored to satisfy market demand [41]. Hydropower is also able to provide the supports for the development of other renewable energy sources, for example, its storage capacity and flexibility can be the most costeffective and efficient to support the utilisation of intermittent renewable energy sources such as solar and wind energy. Hydropower can generate vast quantities of energy, and the price is relatively stable, as it is less affected by market price fluctuations such as oil and gas, although the price advantage is proportional to the capacity of the plant, i.e., relatively small capacity. There is, however, a major drawback of hydropower development as it is heavily dependent on the geographical features (i.e., large rivers) to generate electricity. Therefore, large-scale utilisation of hydropower is only limited to certain places with specific geographical features, making micro-hydropower-with a lower price advantage-a more viable option, as asserted by FI:

*"* ... *no, the majority of them [sources] are only suitable for small-scale power plants. Only certain areas of Indonesia have the full capability to generate large scale electricity".* (FI)
