Indonesia has been dependent on its abundant coal reserves to meet its increasing electricity demand. The Indonesian government is aware of the negative environmental effects of coal combustion and pledged to become carbon neutral by 2060 or earlier by transitioning towards renewables. In principle, it is known that Indonesia has large renewable energy resources. However, these resources have not yet been mapped in high spatial and temporal resolution for the entire country and have not been assessed from an economic as well as electricity system perspective. This dissertation maps the technical and economic potential of solar, wind, and ocean thermal energy in Indonesia, and explores full power system decarbonisation scenarios. The mapped technical potentials amount to up to 22 PWh/year and could cover Indonesia’s expected 2050 7–23 times. Solar PV would become the center piece of Indonesia’s fully decarbonised power system with 468 GWp of PV covering half of 2050 electricity demand. Another key element are 50 GW of sub-sea power lines from Kalimantan and Sumatera to cost-effectively supply Indonesia’s economic center Java, where local available land for renewables is limited. Moreover, we found that recent tariffs limited the economic potential of renewables to the rural, less-developed East. The economic potential could be spread to the rest of the country via different policies, e.g., a carbon tax of 100 US$/tCO2e for onshore wind or a feed-in-tariff of 11.50 USct/kWh for solar PV. The findings of this dissertation are valuable for the bookkeeping of renewable energy resources in Indonesia and could motivate the revision of current decarbonisation targets towards more ambitious levels.@en

Energy transition on small islands is limited by the scarce availability of land, restricting large-scale implementation of onshore renewable energy technologies such as solar photovoltaics and wind power. Ocean energy technologies provide novel opportunities for land-constrained islands to achieve 100% renewable energy systems. While wave power is increasingly implemented in energy system modelling research, ocean thermal energy converters are not yet a standard technology in renewable energy technology portfolios. This research aims to study the impacts of ocean thermal energy converters on the energy system of the Maldives through a structured sensitivity analysis for the two scenario clusters covering e-fuel import and domestic production. The ocean thermal energy conversion plants are modelled using spatially and temporally resolved resource data and cost assumptions from a global upscaling scenario, considering the technology's current development stage. Results show that ocean thermal energy converters play a limited role in 'purely' cost-optimised sub-scenarios due to the availability of very low-cost offshore floating photovoltaics, making it difficult for them to compete. Nevertheless, reduced requirement of energy storage technologies due to the stable electricity production of ocean thermal energy converters offers an option to diversify the renewable energy technology portfolio with only a minor increase in cost.

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Indonesia has large renewable energy resources that are not always located in regions where they are needed. Sub-sea power transmission cables, or island links, could connect Indonesia's high-demand islands, like Java, to large-resource islands. However, the role of island links in Indonesia's energy transition has been explored in a limited fashion. Considering Indonesia's current fossil fuel dependency, this is a critical knowledge gap. Here we assess the role of island links in Indonesia's full power sector decarbonisation via energy system optimisation modelling and an extensive scenario and sensitivity analysis. We find that island links could be crucial by providing access to the most cost-effective resources across the country, like onshore photovoltaics (PV) and hydropower from Kalimantan and geothermal from Sumatera. In 2050, 43 GW of inter-island transmission lines enable 410 GWp of PV providing half of total generation, coupled with 100 GW of storage, at levelised system costs of 60 US$(2021)/MWh. Without island links, Java could still be supplied locally, but at 15% higher costs due to larger offshore floating PV and storage capacity requirements. Regardless of the degree of interconnection, biomass, large hydro, and geothermal remain important dispatchable generators with at least 62 GW and 23% of total generation throughout all tested scenarios. Full decarbonisation by 2040 mitigates an additional 464 MtCO2e compared to decarbonisation by 2050, but poses more challenges for renewables upscaling and fossil capacity retirement.@en

Indonesia has large renewable energy resources that are not always located in regions where they are needed. Sub-sea power transmission cables, or island links, could connect Indonesia's high-demand islands, like Java, to large-resource islands. However, the role of island links in Indonesia's energy transition has been explored in a limited fashion. Considering Indonesia's current fossil fuel dependency, this is a critical knowledge gap. Here we assess the role of island links in Indonesia's full power sector decarbonisation via energy system optimisation modelling and an extensive scenario and sensitivity analysis. We find that island links could be crucial by providing access to the most cost-effective resources across the country, like onshore photovoltaics (PV) and hydropower from Kalimantan and geothermal from Sumatera. In 2050, 43 GW of inter-island transmission lines enable 410 GWp of PV providing half of total generation, coupled with 100 GW of storage, at levelised system costs of 60 US$(2021)/MWh. Without island links, Java could still be supplied locally, but at 15% higher costs due to larger offshore floating PV and storage capacity requirements. Regardless of the degree of interconnection, biomass, large hydro, and geothermal remain important dispatchable generators with at least 62 GW and 23% of total generation throughout all tested scenarios. Full decarbonisation by 2040 mitigates an additional 464 MtCO2e compared to decarbonisation by 2050, but poses more challenges for renewables upscaling and fossil capacity retirement.@en

Geospatial analysis is useful for mapping the potential of renewables like solar PV. However, recent studies do not address PV’s bankable potential for which project financing can be secured. This paper proposes a framework that incorporates project finance into geospatial analyses to obtain the bankable potential of renewables. We demonstrate our framework for Indonesia, and compare the bankable potential with the socio-economic potential mostly used in literature. Using average inputs On average, the technical potential is 12,200 TWh/year and the socio-economic potential is 152.7 TWh/year if capped by 2030 demand (34% coverage). Considering PV’s financing risks, PV’s bankable potential is 16.0 TWh under current conditions if capped by 2030 demand (3.6% coverage). Both economic potentials are mainly in East Indonesia and absent on Java due to tariffs and land availability. For the bankable potential, the risk perception by banks and investors is another key influence. With a feed-in tariff of 11.5 US¢(2021)/kWh and temporary lift of import restrictions, the bankable potential is 23 TWh if capped by 2030 demand (5.2% coverage) and spreads to Java. For more widespread bankability, additional temporary measures are recommended until the PV’s costs have decreased further and trust by financial institutions has increased.@en

Ocean Thermal Energy Conversion (OTEC) is an emerging renewable energy technology using the ocean’s heat to produce electricity. Given its early development stage, OTEC’s economics are still uncertain and there is no global assessment of its economic potential, yet. Here, we present the model pyOTEC that designs OTEC plants for best economic performance considering the spatiotemporally specific availability and seasonality of ocean thermal energy resources. We apply pyOTEC to more than 100 regions with technically feasible sites to obtain an order-of-magnitude estimation of OTEC’s global technical and economic potential. We find that OTEC’s global technical potential of 107 PWh/year could cover 11 PWh of 2019 electricity demand. At ≥ 120 MWgross, there are OTEC plants with Levelised Cost of Electricity (LCOE) below 15 US¢(2021)/kWh in 15 regions, including China, Brazil, and Indonesia. In the short-to-medium term, however, small island developing states are OTEC’s most relevant niche. Systems below 10 MWgross could fully and cost-effectively substitute Diesel generators on islands where that is more challenging with other renewables. With the global analysis, we also corroborate that most OTEC plants return the best economic performance if designed for worst-case surface and deep-sea water temperatures, which we further back up with a sensitivity analysis. We lay out pyOTEC’s limitations and fields for development to expand and refine our findings. The model as well as key data per region are publically accessible online.@en

Ocean Thermal Energy Conversion (OTEC) produces electricity using the temperature difference between warm surface and cold deep-sea water. OTEC systems in literature only limitedly consider seasonal seawater temperature
variations and thus might not be adequately sized for off-design conditions. This potentially leads to techno-economically sub-optimal design choices. This paper sheds light on which design approach yields the most economically feasible OTEC system considering off-design conditions with 19 years of seawater temperature data in 3-h time steps. We find that systems sized for worst-case thermal resources yield the highest and steadiest electricity production. If seawater temperature variations are moderate, these systems also perform best economically in terms of Levelized Cost of Electricity (LCOE). We demonstrate our model for a 136 MWgross plant in Ende, Indonesia, with an LCOE of 15.12 US¢(2021)/kWh against a local electricity tariff of 15.77 US¢(2021)/kWh. The model is validated for different cost assumptions, system sizes, and temperature profiles to be useful globally. We give recommendations to curb costs and to move large-scale OTEC closer to today’s state of the art,
e.g. by using multiple smaller seawater pipes instead of few large pipes. The model is useful to prove OTEC’s global economic feasibility and to promote the technology’s commercialisation.@en

Ocean Thermal Energy Conversion (OTEC) is a promising renewable energy technology that is the most economical at large scale. But contemporary literature does not address how OTEC could reach such scale with current technology, and what the techno-economic impact of location-dependent factors and technological learning are. This paper tackles these issues by simulating OTEC's upscaling with a model that implements OTEC to meet local electricity demand and extrapolates to the global relevance of OTEC. The model uses a learning rate for investment costs and cost of finance. This study shows that up to 45 GW of OTEC capacity can be installed in Indonesia with national demand coverage of 22% in 2050. Even with small cost reduction rates, OTEC could be profitable and cost-competitive against other power generation technologies with an aggregated Net Present Value (NPV) of up to US$ 23 billion. OTEC's upscaling could be funded via state budget reallocation or international financial institutions, e.g. via the feed-in tariff suggested in the paper. However, large-scale OTEC is only feasible in regions with high electricity demand and until that size is reached, upscaling must be coordinated globally, e.g. with the proposed upscaling strategy. To contribute to the global energy transition, OTEC needs to grow by 28% per year, a rate similar to wind power and solar PV. This paper provides good reasons to fight for the attention of global decision makers and future research could focus on refining the concepts of this study.@en

Onshore wind potentials are commonly mapped with site selection criteria that either fully include or exclude land for wind farms. However, current research rarely addresses the variability of these criteria, possibly resulting in overly conservative or optimistic potentials. This paper proposes a method to account for the variability of site selection criteria in resource assessments. We distinguish between static and flexible, non-binary criteria and assess onshore wind's technical and economic potential with bias-corrected ERA5 data, 28 turbine power curves, and a turbine-specific cost model. For Indonesia, we show that our flexible mapping approach improves the transparency of resource potential assessments and could contribute to more informed and useful recommendations. These recommendations could address the (1) calibration of site exclusion thresholds, (2) dilemmas of preferring one land type over others, (3) location-specific challenges of wind farm deployment, and (4) more direct support schemes for affected stakeholders and wind farm operators.. We report a technical potential of 207–1,994 TWh/year in Indonesia, which could cover more than 50% of 2030 electricity demand on all islands. LCOEs range between 5.8 and 24.5 US¢(2021)/kWh with an economic potential of 16 TWh/year, which improves to 31–212 TWh/year with a carbon tax of 100 US$(2021)/tCO2e.@en

The current focus of offshore wind industry and academia lies on regions with strong winds, neglecting areas with mild resources. Photovoltaics' cost reductions have shown that even mild resources can be harnessed economically, especially where electricity prices are high. Here, we study the technical and economic potential of offshore wind power in Indonesia as an example of mild-resource areas, using bias-corrected ERA5 data, turbine-specific power curves, and a detailed cost model. We show that low-wind-speed turbines could produce up to 6,816 TWh/year, which is 25 times Indonesia's electricity generation in 2018 and 3 times the projected 2050 generation, and up to 166 PWh/year globally. Although not yet competitive against current offshore turbines, low-wind turbines could become a crucial piece of the global climate mitigation effort in regions with vast marine areas and high electricity prices. As low-wind-speed turbines are not yet on the market, we recommend prioritizing their development.

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Indonesia has an increasing electricity demand that is mostly met with fossil fuels. Although Indonesia plans to ramp up Renewable Energy Technologies (RET), implementation has been slow. This is unfortunate, as the RET potential in Indonesia might be higher than currently assumed given the archipelago’s size. However, there is no literature overview of RET potentials in Indonesia and to what extent they can meet current and future electricity demand coverage. This paper reviews contemporary literature on the potential of nine RET in Indonesia and analyses their impact in terms of area and demand coverage. The study concludes that Indonesia hosts massive amounts of renewable energy resources on both land and sea. The potentials in the academic and industrial literature tend to be considerably larger than the ones from the Indonesian Energy Ministry on which current energy policies are based. Moreover, these potentials could enable a 100% renewables electricity system and meet future demand with limited impact on land availability. Nonetheless, the review showed that the research topic is still under-researched with three detected knowledge gaps, namely the lack of (i) economic RET potentials, (ii) research on the integrated spatial potential mapping of several RET and (iii) empirical data on natural resources. Lastly, this study provides research and policy recommendations to promote RET in Indonesia.@en

Indonesia strives for a renewable energy share of 23% by 2025. One option to contribute to this goal is Ocean Thermal Energy Conversion (OTEC). Despite a global theoretical potential of up to 30 TW, its economically deployable share remains unknown. This paper proposes a novel methodology, which enables to determine OTEC's economic potential for any regional scope considering technical, economic and natural variables. The methodology was tested for 100 MW_e OTEC in Indonesia on a provincial and national level. Against a regionally variable electricity tariff of 6.67–18.14 US$ct.(2018)/kWh, the national economic potential is 0–2 GW_e with a Levelized Cost of Electricity (LCOE) as low as 15.6 US$ct.(2018)/kWh. With an annual electricity production of 0–16 TWh, OTEC could provide up to 6% of Indonesia's electricity demand in 2018. The capacity factor, capital expenses and discount rate are the most sensitive variables of the LCOE on average. A nationally uniform feed-in tariff of 18 US$ct.(2018)/kWh or more could increase the economic potential significantly. The proposed methodology can be a helpful quick-scan tool for determining economically interesting OTEC sites for follow-up in-depth feasibility studies. Limitations are discussed and future research, amongst others upscaling scenarios with cost reducing effects like technological learning, is recommended.

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Ocean thermal energy conversion (OTEC) is a Renewable Energy Technology (RET) with a global theoretical potential of up to 30 TW. However, OTEC's economic potential is unknown as it is still an immature technology with no commercial plant operating. This paper reviews recent academic and industrial literature since 2005 to provide an overview and critical discussion of current practices in assessing OTEC's economics. Seven knowledge gaps are identified; (1) Current economic analyses focus on individual plants instead of the collective economic potential within spatial boundaries; (2) Natural, location-specific influences on the real net power output are mostly omitted. There is uncertainty about (3) the capital costs on both system and component level as well as the (4) operational costs and properties like useful lifetime. (5) The impact of interest rates and its selection are often not argued for in literature. (6) Technological learning is predominantly omitted in OTEC literature and if treated, it deviates from insights on technological learning. (7) Economic analyses are mostly limited to the Levelized Cost of Electricity (LCOE), while other tools like payback period and Internal Rate of Return (IRR) are neglected. These shortcomings originate mainly from the lack of experience and long-term operational data. For each knowledge gap a recommendation for future research is proposed resulting in a research agenda on OTEC and its economics.

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