Declining resource and negative environmental impact of fossil energy have led to the development of clean and sustainable energy, especially in the power sector. IEA statistic shows that electricity and heat contribute to almost half of the world carbon emission at 42% level in 2016 [1]. Renewable energy sources, such as wind, solar, geothermal, and hydro, offers low-emission energy utilization, especially in the power sector. Figure 1 shows the notable contribution of renewable energy in reducing emission in the power sector. Based on the IEA study, wind and solar PV could potentially reduce the emission in the electricity sector by 22% in 2050 [2]. Besides, the continuing reduction of wind and solar PV costs leverages their competitiveness with fossil fuels and promises to increase their utilization in the future. Thus, wind and solar PV are predicted to play a bigger role in the future for reducing the world’s carbon emission of the power sector as seen in Figure 2.

Figure 1. Cumulative CO2 ­reductions by sector in 2050

Figure 2. Historical and outlook of the world’s energy supply

Despite promising carbon reduction, integrating renewable energy to the power system faces the challenge of its intermittent characteristic. Renewable energy sources, such as wind, solar PV, wave, and tidal, have a variable output depending on their availability of the resource. Wind-generated power output will depend on wind flow and direction, which varies with season. While solar PV, for instance, reaches its peak in the middle of the day and significantly drops towards the sunset. This variable characteristic demands a new power system operating strategy, especially for grid integration, to cater renewable’s distinct characteristic with conventional generation. Thus, integration of the intermittent renewable energy requires a flexible power system network to cater to their output variation.

Integration of intermittent renewable energy source will change the generation dispatching strategy. System operator should ensure the electricity supply meet the demand at all time to maintain the system’s reliability and to avoid any stability issue. The system operator should response the fluctuation of intermittent renewable energy supply and balance the supply-demand within a short period. Fossil fuel generators, such as coal and gas generator, have a different ramping rate to adjust its output level to match current demand. Coal generator often serves as base-load generator due to its low ramping rate while the gas generator is more flexible to follow fluctuation in the network with its higher ramping rate. Fluctuation of renewable energy’s output demands a high ramping generator to cover its up and down generated output. Thus, the system operator requires to schedule and dispatch the available generators to respond to the variation of renewable energy quickly.

The integration of intermittent renewable energy also faces a challenge of fossil fuel generation efficiency and emission reduction. Fluctuating operation of fossil fuel generator, especially gas generator, results in lower efficiency level. Fossil fuel generation efficiency depends on the output of the generation. Operating a fossil fuel generation in a partly-loaded condition will result in lower generation efficiency. Additionally, the output of the generation also affects the emission level of the generation. The emission factor, which tells the emission level relative to the output of the generator, of a partly-loaded fossil generator is higher than a full-load generator [4]. Those factors need to be considered when the system operator insist on integrating the high capacity of intermittent renewable energy to avoid counterproductive impact.

Power system operators require extra flexibility to handle the RE’s generator intermittency. Power system flexibility is the system ability to respond to variation in power system supply and demand [5]. In a conventional operation, operators need the flexibility to deal with load fluctuation and failure of power system component which may impact the system reliability. Increasing the system flexibility can be achieved by running a high-ramping generator, such as gas and diesel power plant, as a reserve. Increasing capacity of intermittent generation introduces a more unpredictable event to the power system. Inability to cope with the supply fluctuation will result in unreliable power system and inadequate supply for the demand. In an inflexible system, the operator will curtail the power from PV or wind to maintain supply-demand balance when the supply of renewable energy exceeds the available demand. Thus, a flexible power system is essential to maintain the reliability and balance of the system while increasing the integration of clean yet intermittent energy sources to the system.

Source of flexibility could come from various technologies, be it in supply, demand, and network sides. In the supply side, gas turbine generator as often said above, could provide flexibility to the system with its quick ramping time such as Combined Cycle Gas Turbine (CCGT) and Open Cycle Gas Turbine (OCGT) [6]. Storages, such as a battery, freewheel, pumped storage hydropower, or other technologies, serve as a backup when renewable energy is not available. Storage technologies can accumulate excess energy, when the demand is lower than the available supply so that renewable energy curtailment can be avoided. From the demand side, flexibility could be provided by implementing demand response. Customers can voluntarily or involuntarily reduce their demand responding to an event occurred in the power system. For example, when the supply from wind or PV is low, the customer will curtail their energy consumption to certain of the level. In return, the customer will be benefited from the compensation for their demand reduction. While in the network side, interconnectivity promises interchange and trade of power across the region or even border. With network interconnection, low renewable output in a region could be covered by other generations in a different region. Sufficient capacity of the grid, however, is required to transfer the power.

A concept of a smarter network, called Smart Grid, comes up to efficiently utilize the capacity of the available grid while avoiding reconductoring the network to increase the capacity. With a smarter network, scheduling of connected generators, including the intermittent generator, could be more optimal [7]. Flexible Alternating Current Transmission System (FACTS) technology would regulate the voltage of the system, as well as improve the power quality. Additionally, the smart meter will be the enabler of a demand response strategy, which enhances the system from the consumer side. Smart Grid, combined with holistic data acquisition, will help the network operator to operate the system more reliable and efficient. Smart Grid could play a role in improving the integration of intermittent renewable energy to the network by computed past information and optimized control action. Smart Grid concept, however, requires communication infrastructure improvement in the power system network to allow information acquisition, information exchange, and the control signal.

Indonesia has put Smart Grid in the country’s plan of electricity provision by including its implementation in the General Plan of Electricity Supply (Rencana Umum Penyediaan Tenaga Listrik, RUPTL). The Smart Grid implementation plan firstly indicates in the RUPTL 2018 – 2027 document issued by PT. Perusahaan Listrik Negara (PT. PLN), Indonesia’s State-Owned Company and sole business player in transmission and distribution. The document is published yearly and comprises PT. PLN ten years strategic plan of national electricity provision including investment, electricity infrastructure construction plan, and operation strategies. In the latest RUPTL (RUPTL 2019 – 2028), Smart Grid implementation is intended to reinforced electricity infrastructure development by:

  1. Ensuring efficient operation planning to provide adequate supply to the power system,
  2. Improving power system reliability,
  3. Improving the electricity access to increase electrification ration and economic growth,
  4. Developing a pre-paid metering system and Advance Metering Infrastructure (AMI).

Smart Grid implementation purposes are not limited to above priorities but also to support the utilization of renewable energy sources, enable customer participation in electricity provision, and provide supporting infrastructure for smart house, smart city, and smart nation development.

Several initiations have been conducted by PT. PLN according to the company’s smart grid road map such as:

  1. Smart Community Project in Surya Cipta Sarana Industrial Estate,
  2. Independent power system prototype in Sumba Island, NTT,
  3. Advance Metering in UID Jakarta Raya.

Smart Grid could support the integration of Indonesia’s vast potential for renewable energy to the power network. In the power generation sector, Indonesia renewable energy sources are dominated with solar power, with 207,898 MW of available resource, due to the country’s location in the equator line as seen in Table 1. As seen in Figure 3 (a) and (b), the solar potential is spread almost in every Indonesia’s provinces. Wind power, though its potential is considerably lower than solar, concentrated in the Sulawesi, Nusa Tenggara, and even in Java, where the demand is highly concentrated. The location of wind and power potential promises integration of clean energy to the Java-Bali grid to supply the high demand for electricity.

Table 1. Indonesia’s renewable energy potential for electricity generation

(a)

(b)

Figure 3. Location of (a) Solar Power and (b) Wind Power potential in Indonesia

The technical side development, such as Smart Grid development, requires a supportive regulation to develop Indonesia’s renewable potential successfully. PT. PLN vision to develop Smart Grid puts Indonesia in the right track of integrating more renewable and clean energy to the network, including intermittent energy. Wider implementation of Smart Grid will also cost PT. PLN more investment in the communication infrastructure in the power system network. In the transition, Indonesia should invest more in a gas power plant in Java to increase the system flexibility as the preparation for future integration of intermittent renewable energy. Compared to coal generation, the utilization of the gas power plant also emits lower emission.

The regulation should also align with country and PT. PLN agenda to integrate more renewable energy into the system. Newly issued Ministry of Energy and Mineral Resource (MEMR) Regulation No. 49/2018 has enabled integration of rooftop solar power to the system. The regulation brings a potential increase of renewable integration from the customer side as well as potential challenges if not managed well. In the meantime, the customer is required to report the proposed specification of their solar PV installation to assess its impact to the power system stability and resiliency. In addition, the regulation must be supportive to tap the renewable potential, especially in Java Island, where the demand is concentrated. The current feed-in regulation, which is limited by the regional cost of generation (Biaya Pokok Pembangkitan, BPP), put a challenge for the development of renewable energy in Java. The regulation encourages the shifting from the expensive fossil generation to the lower cost renewable energy generation, especially in a region which depends on diesel generation. The regulation, however, is seen as less supportive for renewable energy exploitation in a region which has the low regional cost of generation.

References:

  1. IEA, “CO2 emissions from fuel combustion 2018 overview,” CO2 Emissions Statistics, 2018. [Online]. Available: https://www.iea.org/statistics/co2emissions/. [Accessed: 06-Sep-2019].
  2. IEA, “IEA Energy Technology Perspectives 2015,” IEA, p. 14, 2015.
  3. S. Evans, “Analysis: BP’s outlook for fossil fuels could be undermined by slowing energy demand,” energypost, 2019. [Online]. Available: https://energypost.eu/analysis-bps-outlook-for-fossil-fuels-could-be-undermined-by-slowing-energy-demand/. [Accessed: 26-Mar-2019].
  4. C. Graf and C. Marcantonini, “Renewable Energy Intermittency and its Impact on Thermal Generation,” SSRN Electron. J., 2016.
  5. J. Cochran et al., “Flexibility in 21st Century Power Systems,” 21st Century Power Partnersh., vol. May, p. 14, 2014.
  6. M. Rautkivi and M. Kruisdijk, “Flexible energy for efficient and cost effective integration of renewables in power systems,” Wärtsliä Tech. J., p. 16, 2013.
  7. Z. Hu, C. Li, Y. Cao, B. Fang, L. He, and M. Zhang, “How smart grid contributes to energy sustainability,” Energy Procedia, vol. 61, pp. 858–861, 2014.
  8. Purnomo Yusgiantoro Center, PYC Indonesia Renewable Energy Outlook. Purnomo Yusgiantoro Center, 2019.

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