CONSTRUCTION ANALYSIS OF SOLAR PANEL FOUNDATION ON THE SURFACE OF DAM WATER BODY WITH DAM SLOPE (Case Study: Jatibarang Dam Solar Power Plant - Semarang)

Indonesia's potential solar panel renewable energy capacity is 207.8 GW, currently only 0.135 GW has been realized or 0.02% has only been achieved. The development is still very broad and far ahead. The best place for a PLTS (Solar Power Plant) location is in the dam area. Why? The dam has a very large area and is owned by the government. This paper investigates the comparison of the cost and time of implementing PLTS foundation construction at the location of the Dam Slope (Landed) and on the Surface of the Dam Water Body (Floating). The research was conducted based on a case study of the application of PLTS in the Jatibarang Dam. Where in 2017 the construction of PLTS has been realized at the location of the Dam Slope. The PLTS Floating model was developed with a design simulation based on real data at the same dam location. The cost and time indicators for both Landed and Floating foundation models are then calculated and compared. From the analysis results, in terms of costs, the application of the PLTS Floating foundation is 41% higher than the foundation on the slopes. But in time 31% faster than the Slope foundation. By knowing the cost and time comparison between the two PLTS laying models, the aim is to design a PLTS development strategy for the Dam area based on the most optimal considerations.


INTRODUCTION
The Indonesian government is actively participating in efforts to control the ongoing issue of climate change.This commitment aligns with Law No. 16 of 2016, which ratifies the Paris Agreement under the United Nations Framework Convention on Climate Change.
During a presentation by the Ministry of Energy and Mineral Resources Directorate General of New Energy and Renewable Energy, specific policies, regulations, and initiatives for solar energy development in Indonesia were discussed.The aim is to accelerate the establishment of solar power plants in the country, targeting a capacity of 6.5 GW by the year 2025.This presentation, titled "Accelerating the Development of Solar Power Plants in Indonesia to Reach 6.5 GW by 2025" and held on October 10, 2019, emphasized the Indonesian government's commitment to reducing greenhouse gas (GHG) emissions.They have pledged to reduce emissions by 29% using their own resources and achieve a reduction of 41% with the help of international support.The promotion and development of renewable energy (EBT) are significant factors contributing to this reduction in GHG emissions.
Indonesia possesses considerable potential for renewable energy sources, particularly solar energy, which is estimated to have a potential of 4.8 kWh/m2/day (as reported by the Ministry of Energy and Mineral Resources News on "Indonesia's Renewable Energy Potential" on August 24, 2008).Thus, solar energy in Indonesia has great potential to be utilized.One of them is what the Ministry of Public Works through the Directorate General of Water Resources has done by pioneering a pilot project for solar energy development in the form of PLTS (Solar Power Plant) in the dam area, with the installation of 936 solar panels measuring 1.6 meters x 1 meter on the north slope of Jatibarang Dam, Semarang City, Central Java in 2017.The installed electricity capacity generated is 304.2 kilowatt-peak (kWp) or equivalent to 291,000 kilowatt-hours (kWh) per year.
Along with the development of technology and government regulations (PerMen PU on floating foundations) related to EBT Solar Panels, the "Floating PV" pilot project is now being introduced.This type is different from the one that was implemented in 2017 and operated in 2018 at the Jatibarang dam.As the name Floating PV implies, this type of PLTS is placed on the water surface of the dam, with a floating system.The trial has been conducted by the University of Indonesia (Floating Solar Photovoltaic owned by the Faculty of Engineering, University of Indonesia, November 25, 2020).Meanwhile, when this research was written, there were still no projects that applied this type in existing dams in Indonesia.Even though there are research results about the results of solar energy produced by floating PV is greater than that produced by solar panels installed on the ground (Andri Agus Sasmanto, Tresna Dewi, Rusdianasari, Eligibility Study on Floating Solar Panel Installation Over Brackish Water in Sungsang, South Sumatra, Emitter International Journal of Engineering Technology, 2020).This paper will examine the comparison between the construction costs of solar panel foundations installed in the water body of the dam compared to those installed on the dam slope with reference to solar panel installation project data at Jatibarang Dam.The construction cost of solar panel foundations is one of the things that is very influential in determining the policy of where solar panels will be installed.
Through this research, it is hoped to provide a comprehensive comparison of the construction costs between solar panel foundations installed in the water body of the dam and those installed on the slopes of the Jatibarang Dam.This valuable comparison will assist stakeholders and the government in making informed decisions regarding the type of Photovoltaic Solar Power Plant (PLTS) to be implemented in the dam area in the future.Additionally, the findings can serve as a crucial reference point for policy-making and further research endeavors.

LITERATURE REVIEW
In Secondary data used refers to real data at the case study site at Jatibarang Dam and related Government Regulation data.The data are in the form of: a. Siteplan contour drawing of Jatibarang Dam. b.Cross section and long section drawings.c.Technical planning documents for the foundation of the solar panel dam slope (DED and BoQ).d.PerMen PUPR no 28 th 2016, as the basis for preparing AHSPK (Analysis of Unit Price of Work).e. Perwali Kota Semarang no 61 of 2020 (Standard unit price of labor and materials).

Construction Costs
Construction costs are the costs required to carry out a project activity.In this study, the construction costs to be calculated are aspects of labor, material, equipment and overhead costs according to applicable regulations.

Foundation
Foundation is the strong base of a building that sits beneath the building being erected.The foundation serves to support and maintain the stability and safety of a building structure from vertical and lateral loads acting on it.Foundations are usually underground and are an important part of building construction, as the quality and strength of the foundation will affect the overall robustness and lifetime of the building.

Solar Panel
Solar Panels are electronic devices consisting of several solar cells or photovoltaic cells designed to capture and convert sunlight energy into electricity.Solar cells in solar panels are made of semiconductor materials, such as silicon, which have the ability to generate electric current when illuminated by sunlight.

Water Body Dam
A body of water is a collection of water whose size depends on, among other things, the relief of the earth's surface, the size of the barrier rock, rainfall, temperature and so on, such as rivers, swamps, lakes, dams, seas, and oceans.So, a dam water body is a body of water that exists in a dam.

Dam Slope
A slope is the sloping side of the land.The dam slope is part of the dam structure which is a sloping surface or basin on the upper and lower sides of the dam.These slopes play an important role in holding and distributing the water pressure generated by the water behind the dam.

RESEARCH METHODS
The research subject of this paper is PLTS Jatibarang Dam Semarang-Central Java, which is a pilot project for the application of PLTS on the slopes of dams (reff news Kemeterian PUPR 6 April 2018), and researchers are actively involved in realizing the project.
The data collection procedures in this study were as follows: a. Determine the primary data used in the study.
The Based on the results of the calculation analysis of the solar panel foundation on the dam slope and in the dam water body, a comparison of the cost and construction time of the foundation will be analyzed.

RESULTS AND DISCUSSION
The data used by researchers in conducting research consists of two types of data.For the analysis of the cost and time of the foundation of the solar panel on the dam slope using existing primary data, namely planning data on the Jatibarang Dam Solar Panel System Procurement Project in 2017.As for the cost and time analysis of the foundation of solar panels on the surface of the dam water body, with secondary data referring to journal data and research and similar project reports.

Figure 4 .
Figure 4. BoQ items for foundation installation Source: Jatibarang Dam solar panel system procurement project document

Figure 5 .
Figure 5. Schematic of Floating Solar Panel structure Source: Solar Energy Research Institute of Singapore (SERIS)

Figure 8 .Figure
Figure 8. Location of Floating Solar Panel Source: Google Earth imaging 2021

Figure
Figure 12.Cross Section Source: researcher engineering