SINGAPORE – A second discovery of high temperatures underground in northern Singapore has shown the potential of using geothermal energy to generate electricity here.

But whether this energy form could eventually become part of the Republic’s energy mix needs further study to determine if it is cost-effective to do so, say experts.

Currently, 95 per cent of Singapore’s total energy is generated by the burning of natural gas, a fossil fuel. The country is studying alternative energy sources, such as geothermal energy, to reduce emissions from energy generation.

On July 3, researchers from Singapore said they have, at a site in Gambas Avenue in Sembawang, found temperatures of up to 122 deg C about 1.76km underground.

The research team from Nanyang Technological University (NTU) and TumCreate – the Technical University of Munich’s multidisciplinary research platform based in Singapore – added that underground temperatures have the potential to go up to 230 deg C at depths of 5km.

Electricity can be generated with temperatures above 150 deg C.

Dr Jonathan Poh, research fellow at the Energy Research Institute at NTU (Eri@n), who was part of the study, said the latest finding shows that this renewable energy source could be viable for Singapore.

The discovery of high underground temperatures in Sembawang comes after the team had in March 2023 found temperatures of 70 deg C in Admiralty, located 1.12km underground .

To determine if technical feasibility can translate into reality, however, the economic viability of geothermal energy as a carbon-free energy source warrants greater probing, said Dr David Broadstock, senior research fellow and energy transition research lead at the Sustainable and Green Finance Institute at NUS.

“We see the technological potential, which confirms a viable pathway for geothermal energy... but now we need to see if there is feasibility for sustained energy provision. Until then, we can’t tell if this is economically feasible,” Dr Broadstock added.

Sustained energy provision refers to whether the underground heat reservoirs are able to provide sufficient energy to generate electricity in a stable way.

Other renewable energy sources, such as solar, can be intermittent as electricity generation stops when the sun does not shine.

The heat supplied from the earth’s core, however, is consistent, and can last for decades, which makes it a much more stable source of energy, said NTU’s Professor Alessandro Romagnoli, one of two researchers leading the research.

Supported by the National Research Fund, the study officially started in October 2020 and concluded in February 2025.

The Sembawang site is located just 600m away from the hot spring, which is open to the public to enjoy .

Heat from the earth’s core reaches around 6,000 deg C at a depth of about 6,400km.

Singapore is not situated near a volcanic region, but the Republic has a surface heat flow and granite heat production that is twice the global average, said Prof Romagnoli, who is also the cluster director of multi-energy systems and grids at Eri@n.

Heat flow refers to the rate at which heat generated in the earth’s core travels towards the surface. A higher heat flow reduces the depth needed for drilling to determine the Republic’s geothermal potential.

This higher-than-average heat flow is due to how the granite formed under Singapore over the last 230 million years, he noted.

The heat generated by geothermal sources is derived from the heat flow from the core, and also from heat generated through the decay of granite.

As granite decays, radioactive elements found within – such as uranium and thorium – release heat naturally.

The Republic’s geothermal potential, in particular, is contributed mainly by granitic decay.

For instance, the bedrock in Sembawang is made of a material known as Simpang granite, which carries high concentrations of uranium and thorium.

The heat flow range at the Sembawang site was 125 to 131 milliwatts per square metre (mW/sq m) – more than twice the global continental average of 65 mW/sq m.

In Cornwall in Britain, a geothermal site sits on a granitic body alike to the site found in Sembawang, with a heat flow of more than 120 mW/sq m. Currently operational, it produces heating for nearby buildings .

“The earth’s crust towards the Sumatran heat anomaly west of Singapore has been stretched and thinned, allowing heat from deeper layers to travel a shorter distance and be absorbed more easily by the surrounding rocks,” Prof Romagnoli added. The Sumatran heat anomaly refers to the unusually high geothermal heat flow observed in Sumatra in Indonesia.

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Compared with a forecast of the cost of producing electricity using hydrogen gas – another form of clean energy – between 2020 and 2050, the researchers found that geothermal energy could reduce electricity generation costs by at least 38 per cent, and chilled water costs by up to 39 per cent.

They also found that electricity generated from geothermal sources could bring a reduction in greenhouse gas emissions by at least 90 per cent, compared with that generated from the burning of natural gas.

Prof Romagnoli said: “Based on our findings, if a future geothermal plant in Singapore were to generate 50 megawatts of electricity, it could potentially reduce electricity costs by over 40 per cent compared to a typical gas-fired power plant.”

However, Dr Broadstock said there are other costs to consider as well in the establishment of geothermal energy infrastructure.

For example , factors that are less well-known, such as the quality of the bedrock, could affect tunnelling costs.

Mr Darryl Chan, director of the Energy Technologies Department at the Energy Market Authority (EMA), told The Straits Times that the authority’s current focus is to map out Singapore’s underground heat resource.

EMA has commissioned another study to investigate this. The results are expected to be completed in 2026 .

“This information, which will be acquired through the on-going nationwide non-invasive geophysical survey, is required for EMA to ascertain the techno-economic viability of deploying deep geothermal energy systems in Singapore for electricity generation,” he added.

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Besides Admiralty and Sembawang, another known hotspot is on Pulau Tekong.

Mr Chan noted that EMA is also studying other aspects of geothermal energy deployment, such as how deep geothermal systems would need to be regulated, and what their potential impact to the environment is.

Dr Swati Sharma, who does research on environment and resource economics at NTU’s School of Social Sciences, said Singapore’s limited space is a constraint to alternative energy it can harness.

“There is also potential in innovative deployment strategies,” she said. “For example, co-locating geothermal plants with other low-carbon technologies, such as green hydrogen production facilities, can optimise resource use and improve project economics,” she added.