CIVIL & STRUCTURAL ENGINEERING
A REALISTIC DESIGN OPTION FOR LARGE-SCALE
RENEWABLE ENERGY GENERATION by Bob L Y Cheung, Bob Cheung Offshore Consultants, Singapore Singapore is a small land-constrained island nation situated next to the equator, with a land area just over 720 m2 and a coastline of about 190 km. The main island is basically flat with few hills. The tallest hill is the Bukit Timah Hill which stands at a height of just over 160 m and is shorter than some of the skyscrapers in the downtown area of Singapore. There are few large reservoirs dotted over Singapore. Wind speed is usually very low. Even the Building Design Code does not specify high Design Wind Velocity in practice. Wave height around Singapore is also very small. The daily Significant Wave Height is usually less than 1.5 m. But there is a monsoon season that brings in heavy rainfall and modest wind although the season is relatively short. The population of Singapore is about 5.5 million. Having an undulated landscape, instead of a mountainous one, it is relatively less costly to build physical infrastructure and numerous HDB flats that are now home to 75% of its citizens. In fact, we now have over one million HDB flats in Singapore and 200 km of covered walkways. Keeping in mind all these natural constraints of Singapore, do we have the potential to harness large scale green energy within the boundaries of Singapore in a short time-frame and at a reasonable cost? The answer is a definite ‘Yes’ and the reason lies in a simple structural design concept that can provide Singapore the space it needs without having to intrude into its valuable land reserve. In this article, we shall discuss how we can use this simple structural design concept to generate large-scale green renewable energy that can provide electricity to 100,000 four-room households on a regular basis. When demand surges, this concept can be extrapolated to cover 200,000 households or more. Moreover, renewable energy generated through this design concept can be utilised to generate Green Hydrogen for other energy needs, if desired. Green Hydrogen is the fuel of the future. RENEWABLE ENERGY OPTIONS FOR SINGAPORE We will look at two options: wind energy and solar energy. As both are fluctuating energy sources, a standard electricity grid is still necessary to complement the renewable energy component. Each option has its own limitations and cost implications and we shall investigate each one in more detail.
Wind energy Wind energy is well developed in many countries in recent years. Is it suitable for Singapore? Electricity is generated using wing turbines. Bigger turbines and stronger wind speed will produce more electricity and more noise. Wind speed, which is governed by a mathematical equation in the Design Code, increases with height. Hence, taller and bigger turbines will collect stronger wind energy. This may pose a problem for low-lying Singapore as the basic daily wind speed near the ground is much less than 30 km per hour (18.6 mph). As a result, only limited electricity can be produced even if many wind turbines are collectively placed on top of 12
THE SINGAPORE ENGINEER May 2020
Bukit Timah Hill. In densely populated Singapore, it is often difficult to find large plots of empty land to install that many wind turbines, which are much taller than the neighbouring HDB blocks. Another problem we may encounter in Singapore is that tall wind turbines may interfere with the taking off and landing of aircraft at civilian and military airports. Building an offshore wind farm in Singaporean waters will also cause problems for shipping traffic. If the offshore farm is installed far out at sea, the cost of installing the turbines, building the needed central control platform, laying the subsea cables and the provision of security and maintenance will be astronomical. If we were to use the reservoirs in Singapore for a wind farm, water pollution issues during the construction, installation and maintenance phases will be a major concern. In addition, decision-making complications such as deciding on the ideal location (either in a shipyard or onsite) to fabricate the structures, deciding on the ideal location to assemble all the pieces including the turbines, deciding on the ideal method to put the turbines in the
