Acknowledgements

We would like to express our sincere gratitude to our project supervisor, Prof. Lim Li Hong Idris, for her invaluable guidance, encouragement, and continuous support throughout the course of this project. We are also deeply grateful to our industry partner, Mr. Tan Toh Hian, for providing direction, insights, and consistent support.

Our appreciation extends to the SolarReborn UROP team for the support and assistance they have provided throughout the project. We would also like to thank Ms. Annie Tan and the staff at the Electronics Lab, Mr. Dickson Foo and the staff at the Central Workshop, Mr. Vincent Bay and the staff at the Fabrication Lab, as well as the IDP staff, whose support and expertise were essential in bringing this project to completion.

1.0 Introduction

There is a growing adoption of large-scale Concentrated Solar Power (CSP) plants worldwide, such as Crescent Dunes and Noor Energy 1. These plants are typically hundreds of megawatts in capacity and use mirrors or lenses to concentrate sunlight onto a central receiver, heating a fluid like molten salt. This stored thermal energy allows them to generate electricity even when the sun isn’t shining, providing reliable, dispatchable power [1].

However, limited research exists on small-scale CSP systems for independent buildings. The smallest deployed systems are typically in the kW range or larger and are mostly used for rural electrification, and limited research is being conducted on water heating applications. Examples include:

• Small scale concentrating solar plants for rural electrification [2]
• Design optimization, fabrication, and performance evaluation of solar parabolic trough collector for domestic applications [3]

The aim of this project is to evaluate the technological and economic feasibility of small-scale CSP systems. In collaboration with E&ST Environmental, a potential deployment site has been identified at a hotel in Tanjung Balai, Indonesia, where solar conditions are favourable. Situated 3° north of the equator, Indonesia benefits from consistently high solar exposure, with a three year average Direct Normal Irradiance of 385 W/m², exceeding Singapore’s average of 335 W/m² during sunlight hours [4]. This exceeds the 228 W/m² threshold [5] for CSP viability approximately 54.1% of the time, compared to 44.75% in Singapore, where the prototype was tested.

In addition, the greater availability of land in Indonesia makes it well suited for CSP installations, in contrast to land-constrained countries such as Singapore, where higher energy density solutions are typically prioritised.

In hotels, approximately 15 - 25% of electricity consumption is attributed to hot water generation, with primary uses including showering, kitchen operations, and laundry [6],[7],[8]. This project will focus specifically on hot water for showering, as it represents the largest share of hot water demand [9].

According to recent news, the electricity costs are expected to rise by 2.1% if oil prices stay high [10]. Although current business tariffs in Indonesia are around IDR 1,114.7 per kWh and have been kept stable through government subsidies [11],[12], this approach is unlikely to be sustainable in the long term. Enhancing energy resilience through increased domestic energy production and reduced reliance on external sources would help alleviate fiscal pressure and support more effective allocation of resources for national development.

By supplementing the energy supply of the hotel with an alternate source, we aim to decrease the electricity cost by approximately 10% [13], which is the proportion used for hot water showering. Considering the escalation cost, the total amount of electricity cost reduction is 12%.

This project evaluates the potential of a small-scale CSP system for hotel hot water production to reduce long-term operating costs and mitigate exposure to fluctuating energy prices, through the design and assessment of a system based on an enhanced CSP rig developed by the team from August 2025 to April 2026.

1.1 Competitor Analysis

1.1.1 Existing small-scale CSP systems

A Gazi University study presents a small-scale 3.6 m² parabolic trough CSP system with solar tracking that uses water as the heat transfer fluid but has no thermal energy storage [14]. Although it shows the feasibility of small-scale CSP, it is not well suited for hotel hot water supply, which requires continuous high-volume heating. Meeting this demand would require either multiple units, which need spacing to avoid shading, or a larger rooftop system, which may affect hotel aesthetics.

Another study by Taylor & Francis reports a 1.5 m² parabolic trough system for domestic water heating in Pakistan [3]. It heated 100 L of water to 60 °C in 5 hours using water and thermosiphon circulation, but it also lacked thermal energy storage. This limits its suitability for hotel use, where hot water must remain available beyond daylight hours.

Figure 3: CSP system by Gazi University [14]	Figure 4: CSP system by Taylor & Francis [3]

1.1.2 Solar water heater

The closest competitor to our system is the conventional solar water heater, as both directly use solar energy for hot water production without continuous electricity. These systems are mature and widely available. In Indonesia, brands such as Handal, with over 35 years of experience, and WIKA offer solutions like the Handal 303 PRIME and WIKA Solar Water Heater SR300L2 for hotel scale applications [15][16].

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Typical commercial systems deliver hot water at around 60 °C [17][18]. In contrast, our system is better positioned for applications requiring significantly higher temperatures at lower water volumes and improved heat retention, although it remains at the prototype stage.

In terms of efficiency, the CSP TES system currently delivers about 13.6 W/m² on a 24 hour average basis, compared to approximately 83.3 W/m² for a certified commercial collector under Category B medium radiation conditions, about 196 W/m², which is similar to Singapore’s average irradiance [19]. This corresponds to about 16% of the benchmark. As this comparison is based on ICC SRCC OG 100 standardized ratings, it provides a reliable basis for evaluation [20]. Hence, the prototype is significantly less efficient than mature systems on a unit area basis.

In terms of cost, while commercial collectors in the Indonesian market are priced around S$630 to S$1,011 per m² based on WIKA products [21][22][20][23], the current rig is not yet cost competitive. Its value lies instead in its potential as a compact CSP system with integrated TES, offering opportunities for higher temperature operation, storage integration, and future scalability with further optimization.

1.2 Value Proposition

The proposed CSP system harnesses freely available solar energy to deliver a reliable supply of hot water at 40 - 45 °C [24] for showering between 8:00 AM and 4:00 PM, reducing electricity costs by approximately 10% and offering an affordable, sustainable solution for hot water production in Indonesia.