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2.0 System Design

2.1 Case study

The layout of the hotel is approximated below, with a usable implementation area of 1288sqm (greyed out) identified from the total land area of 0.5 hectares, using standard hotel width dimensions as a reference. [1]

2.2 Proposed System Design

The functional requirements of the client are as follows:

Table 1: Functional requirements of hotel [2] [3]

The final proposed system is as follows:

The proposed system consists of modular islands, where each island consists of multiple rigs (receiver and reflectors) connected to a thermal energy storage (TES) tank (see below). This aims to reduce overall cost per rig by having common components across multiple rigs.

Water is supplied to the TES tank via the water mains, which also provides pressure to drive flow to the hot water storage tank and subsequently to the showers. The hot water storage tank is located in the hotel where it reduces delay in hot water delivery, stores excess thermal energy for periods of low solar irradiance, and provides additional heating to maintain water temperatures.

Proposed System Design Specifications

Our system design specifications are as follows to meet the clients requirements:

The derivation of the design specifications are located in the appendix.

2.3 Improvements on Rig Design

Previous Rig Design from August to Dec 2025

In Semester 1, the solar tower and parabolic dish configurations were tested independently, and the resulting static water temperatures were recorded. The solar tower configuration achieved a maximum temperature of 82 °C, while the parabolic dish reached a maximum of 61.6 °C. However, a fully integrated system combining the light capture, thermal transmission, and thermal energy storage subsystems was not developed at that stage.

Enhanced Rig Design from Jan to Apr 2026

By the end of Semester 2, all subsystems, light , thermal transmission, and thermal energy storage were successfully integrated to form a fully functional system. The final test rig was able to heat 10 L of water to a maximum temperature of 55 °C and maintain the water temperature above 40 °C for 9 hours.

This performance was achieved by increasing the reflective surface area, incorporating insulation to minimise heat losses, and integrating a thermal energy storage system to sustain the water temperature above the desired range.



Appendix A: Design specifications for light subsystem

The sunlight conditions in Indonesia are assumed to be 1,000 W/m² and AM1.5 based on standard test conditions [4]. The average Direct Normal Irradiance is assumed to be 385 W/m², based on data from Solcast, and the sunlight hours are assumed to be 5.5 hrs [5].

The reflectivity of commercially available cost-effective mirrors ranges between 85% – 95%.

Based on the weather data assumed above, the required reflector area needed if 100% of the captured rays are reflected and absorbed by the water (thermal transmission fluid) in the receiver would be 0.165 m². However, accounting for losses from the reflectors, receiver, thermal transmission and thermal energy storage, the reflector area can be scaled up to a minimum of 1 m², as the test rig area is 1 m².

The absorptivity of the material used in the receiver is crucial, as it determines how effectively the receiver can absorb sunlight reflected by the mirrors. Therefore, an absorptivity of 90% is chosen for the receiver material.

A highly absorptive material is also highly emissive. In the case of the receiver, we aim to maximize absorption while minimizing emissivity. Therefore, the emissivity will be controlled within 1.5%–70%, as the emissivity of black paint is 90% [6], and surfaces with measured emissivity values for temperatures in the 100 – 400 °C range fall within this range.

Thermal conductivity is also an important factor, as the absorbed thermal energy by the receiver must be efficiently transferred to the water inside. The receiver can be built using different materials such as metals or ceramics. Among commercially available options, metals are easy to shape, cost-effective, and have thermal conductivities in the range of 300 – 400 W/mK [7].

The surface area of the receiver is another key factor. Increasing the surface area allows for greater thermal absorption but may also increase heat losses due to convection and radiation [8]. For low-temperature applications (<200 °C), the concentration ratio (area of reflector / area of receiver) is typically 1:5 [9]. However, based on data from a solar tower configuration conducted by the UROP team, we will scale up the receiver area to match the aluminum pot used in their experiments.

The weight is not considered as a critical factor as the installation will be fixed in place after setup. Additionally, the rig will be transported in parts, allowing for easy assembly, so weight considerations are minimal.



Appendix B: Design specifications for thermal transmission subsystem

Power consumption per rig is estimated against power available per meter square for solar panels, and 1288m^2 of rigs available, and 1176m^2 of area available for solar panel (front of hotel rooftop). Total power produced by solar panels is 176,400W (assuming minimum produced of 150W/m^2). [10] Hence, maxiumum power that can be consumed by each rig assuming full space usage is 136.96W. Thus, the power consumption per rig is set at ≤136.96W.

The efficiency of the system's insulation is measured by:

  1. Heat loss per meter
  2. Pipe losses as percentage of total energy delivered, and

Heat loss per meter is the main measurement of the insulation's effectiveness. In residential units, the heat loss per meter is within the range of 5.1-10.8W/m for insulated domestic hot water systems. [11] For our system usage, the representative threshold value of 7.95W/m will be used in design specifications.

Pipe losses as percentage of total energy delivered is on average 16-19% in residential units. [12] In conventional hot water systems, pipe losses are expressed as a percentage of the total energy input to the water heater. However, in the CSP system, there is no heater supplying energy as all the energy is collected from solar energy. In the prototype, the total energy delivered is defined as the total thermal energy that the water absorbs at the receiver. Hence, we set the value in the design specifications as 17.5% for reference which is the average estimate for pipe losses based on residential hot water systems.



Next section: 03. CSP Rig Development

References