Feasibility study on tidal energy harnessing using underground cavern

• Main Author: Lim, Yong Siang
• Other Authors: Tan Soon Keat
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Business::Management::Feasibility studies; DRNTU::Engineering::Mechanical engineering::Alternative, renewable energy sources
• Online Access: http://hdl.handle.net/10356/72917
• Institution: Nanyang Technological University

The purpose of this report is to determine the feasibility of utilizing an underground cavern as a water storage while harnessing tidal energy. This study will benefit countries with excellent open water body networks, but lack surface land space to cater for massive water storage. Thus, Singapore had been chosen to be the test-bed for this project. In the preliminary proposal, the site location, storage, pipe, turbine and pump designs were examined. The Jurong area is suitable as an underground cavern due to the beneficial properties of Jurong Rock Formation. Storage design was based off the Jurong Rock Cavern concept whereas Galvanized Steel was selected for essential properties such as corrosion and marine fouling. Finally, Kaplan Turbines and Piston Pumps were selected based off its capability in coping with large discharge rates. Thereafter, calculations were based on theoretical formulas, and 12 parameters were selected to be in the optimization of the system design – 1) Depth of the underground water storage; 2) Horizontal length of the outlet and inlet pipes; 3) Number of Inlet; 4) Number of Outlet pipes; 5)Number of stages throughout an Inlet pipe; 6) Inner radius of the Inlet pipe; 7) Inner radius of the Outlet pipe; 8) Discharge rate of the pump; 9) Efficiency of Turbines; 10) Efficiency of Pumps; 11) Total operational volume of the storage; 12) Price difference between the buying and selling of electricity. After tabulating the result, 4.2m3 was selected as the storage capacity, as it can generate 16.7GWh per quarter. This surpasses the total amount of electricity generated (136.3MWp) from all the solar panels in Singapore. However, the setbacks for the designed system are the volume of underground space required and the selling price of electricity generated. For this project to be profitable, a minimum price difference of SGD $5/kWh must be achieved with the consideration of breakeven point less than 20 years. The limitation in designing this system is that the result is derived solely based on theoretical formulas with some assumptions made. The actual implementation of the system must cater for uncertain discrepancies from our theoretical model. To minimize discrepancies between theoretical model and actual performance, this paper recommends future experiment to use software modelling capable of considering more variables to model the system’s performance. In sum, the designed system is currently infeasible to be implemented in Singapore as it requires a huge price difference to be a profitable. However, this does not preclude future possibilities with more in-depth research conducted to decrease the price differential required for economic feasibility.