Solar photovoltaic technology has become one of the leading solutions for advancing renewable energy. However, despite its enormous potential, its performance is often constrained by a significant challenge, particularly in tropical countries such as Indonesia. As solar panels become hotter under prolonged sunlight exposure, their electrical conversion efficiency decreases. Addressing this issue, Rudi Darussalam has developed a water-based photovoltaic-thermal (PVT) system capable of generating electricity while simultaneously capturing solar heat as useful thermal energy.
Through his doctoral research at the Faculty of Engineering, Universitas Indonesia (FTUI), Rudi designed and built a prototype water-based PVT system featuring a twin spiral collector specifically engineered for tropical climatic conditions. This innovation enables the recovery of waste heat from photovoltaic modules for water heating, allowing a single system to produce both electrical and thermal energy simultaneously. Additionally, he developed an integrated mathematical model that accurately predicts the system’s performance under a wide range of real-world operating conditions.
In recognition of this achievement, Rudi was awarded a doctoral degree from FTUI’s Department of Electrical Engineering. He graduated with a perfect Grade Point Average (GPA) of 4.00 and the distinction of Cum Laude. Rudi is the 201st doctoral graduate of the Department and the 671st of FTUI. His dissertation is entitled “Investigation of the Effectiveness of a Water-Based Photovoltaic-Thermal System with a Twin Spiral Collector in Tropical Climates.”
Indonesia possesses abundant solar energy resources, but it also faces the challenges of high solar irradiance and elevated ambient temperatures. In conventional photovoltaic systems, a significant portion of the incoming solar energy is converted into heat, thereby increasing the temperature of the photovoltaic modules and reducing their electrical efficiency. The photovoltaic-thermal approach addresses this limitation by recovering the excess heat and utilizing it as a valuable source of thermal energy for various applications.
Rudi’s prototype includes photovoltaic modules, a twin spiral collector, a circulation pump, a water storage tank, a heat exchanger, a piping system, and various monitoring instruments. The system was tested under actual conditions in Bandung and demonstrated stable performance. It successfully generated both electricity and thermal energy simultaneously in tropical climate conditions.
Experimental results showed that higher solar irradiance not only increased the electrical power output of the photovoltaic modules but also produced hot water suitable for practical use. During testing, the system generated electrical power of up to approximately 175.8 watts while increasing the water temperature to 36.57°C. These findings demonstrate that the water-based photovoltaic-thermal system equipped with a twin spiral collector can significantly improve the overall utilization of solar energy compared with conventional photovoltaic panels.
Beyond its technological innovation, the research also offers broad opportunities for real-world implementation. The thermal energy generated by the system can be utilized for hot water supply in households, hotels, hospitals, and commercial facilities. The technology also has the potential to support production processes for micro, small, and medium-sized enterprises (MSMEs), sanitation systems, and agricultural applications requiring clean and sustainable energy sources.
Rudi further recommends future research involving the integration of Internet of Things (IoT) technology for real-time system performance monitoring, as well as the use of nanofluids as cooling media to enhance heat transfer efficiency. Additional long-term studies are also needed to evaluate system performance under extreme tropical conditions, including prolonged high temperatures, high humidity, fluctuating solar irradiance, dust exposure, and corrosion risks in coastal environments.
Rudi Darussalam explained that the primary objective of his research is to maximize the utilization of solar energy—not only by generating electricity but also by recovering heat that would otherwise be wasted.
“Heat generated by solar panels has traditionally been regarded as a factor that reduces electrical generation efficiency. Through a photovoltaic-thermal system, this excess heat can instead be recovered and converted into useful energy, allowing solar energy to be utilized more comprehensively. I hope this research will contribute to the development of more efficient solar energy technologies that are well-suited to Indonesia’s tropical climate,” said Rudi.
The Dean of the Faculty of Engineering, Universitas Indonesia, Prof. Kemas Ridwan Kurniawan, S.T., M.Sc., Ph.D., praised the research as an example of engineering innovation capable of addressing Indonesia’s energy transition challenges.
“This research demonstrates how engineering can provide practical solutions to the unique challenges faced by tropical countries while opening new opportunities for the development of more applicable solar energy technologies. Innovations like this are essential for advancing the efficient and sustainable utilization of renewable energy,” said Prof. Kemas.
The research findings were presented during an open doctoral promotion session held on 23 June 2026 at the Smart Meeting Room, FTUI Dean’s Building. The session was chaired by Prof. Kemas Ridwan Kurniawan, S.T., M.Sc., Ph.D., with Prof. Dr. Ir. Iwa Garniwa, M.K., M.T. serving as the principal supervisor, and Chairul Hudaya, Ph.D., and Ahmad Fudholi, Ph.D. as co-supervisors. The examination committee comprised Prof. Dr. Ir. Rudy Setiabudy, DEA; Faiz Husnayain, S.T., M.Sc., Ph.D.; Ismi Rosyiana Fitri, S.T., Ph.D.; and Prof. Ir. Syamsir Abduh, M.M., Ph.D., IPU., ASEAN Eng.
This research demonstrates that the tropical climate, often regarded as a limitation for photovoltaic systems, can instead become an opportunity to develop technologies that utilize solar energy more comprehensively. Through innovations such as this, FTUI reaffirms its commitment to producing research that not only achieves academic excellence but also contributes to the advancement of clean energy technologies, strengthens national energy security, and supports the achievement of the Sustainable Development Goals (SDGs).
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Public Communication Office
Faculty of Engineering Universitas Indonesia
