Innovative solutions to tackle the energy crisis

One of the world’s greatest challenges for the next 50 years is to ensure enough clean, affordable and reliable sources of energy. However, this is also one of the most complex problems facing society today, and there are many technological hurdles to jump over first.

To effectively combat the energy crisis, we must reduce our reliance on non-renewable sources of energy and be more efficient in storing and using energy. At NUS, scientists are pioneering technologies to improve all aspects of these three key areas.

Renewable sources of energy

Renewable energies come from sources that are not depleted when used, such as wind or solar power, or natural processes that are replenished faster than they are used. One of the most common usages of renewable energies is the direct conversion of sunlight into electricity using the photovoltaic (PV) effect. While virtually inexhaustible and almost maintenance-free, solar PV faces some challenges that need to be addressed through continuous research and development, such as increasing the solar cell efficiency, finding alternative deployment options (as not every country has vast landmasses available, such as Singapore), and mitigating the effects on the power grid that result from the inherent variability of solar power that comes from changes in cloud cover.

This is why researchers at the NUS Solar Energy Research Institute of Singapore (SERIS) are focusing on making solar power a cost-effective and trusted source of electricity. The bright minds at SERIS are researching everything from how to make the next generation of high-efficiency industrial solar cells, to how to predict the amount of solar energy at a particular location and time. The team, working closely with Singapore’s national water agency PUB, and the Singapore Economic Development Board, has designed and constructed the world’s largest floating solar panel testbed in Singapore’s Tengeh Reservoir as early as 2016. In consequence, SERIS is today considered as the leading applied research institute for this novel deployment option.

To push the next boundaries, SERIS is now moving its research towards near-shore and off-shore floating PV installations, in collaboration with major industrial partners. Despite a more corrosive environment and stronger mechanical forces in a marine setting, there are great opportunities of combining near-shore and off-shore floating solar with other uses to “solve more than one problem” such as food supply (combining with fish farming), green hydrogen generation (combining with electrolysis), or fresh water supply (combining with desalination).

Floating solar panels on bodies of water could help save space when collecting solar energy, but what if the same solar energy could be used to clean the water? Rather than using sunlight as renewable energy to generate electricity, Professor Ho Ghim Wei and her research group from NUS Electrical and Computer Engineering are investigating ways to use sunlight directly to create clean water sources. Her solar-enabled technology can capture, distil, and desalinate water, offering a promising solution for sustainable freshwater production at a minimal energy cost.

Beyond this, her contemporary work also demonstrates new opportunities for generating simultaneous fresh water and clean electricity by coupling solar desalination with photothermal-assisted photocatalysis hydrogen production, pyroelectricity and thermoelectricity. Such innovation relentlessly tackles the inextricably linked water–energy nexus. Notably, these solar technologies could lend themselves to compact design suitable for off-grid communities.

Because of its abundance, sunlight is one of the most commonly investigated sources of renewable energy. But there is another source of energy available which is typically overlooked when it comes to research – food waste.

Food waste remains one of the biggest waste streams in Singapore and the world. As part of the overall solution to manage food waste, Associate Professor Tong Yen Wah from NUS Chemical and Biomolecular Engineering has been looking into recovering energy from it.

His method uses a self-sustaining ‘anaerobic digester’ system that converts food scraps into resources. Essentially this anaerobic digester mimics the stomach of a cow, where the first stage acts to hydrolyse food waste, the second stage converts the hydrolysed compounds into acids and acetate, and the third stage uses anaerobic microbes to produce biogas. This biogas is completely renewable and can then be used to generate electricity just like natural gas. With this anaerobic digestion system, food waste can be managed and treated on-site where it is generated, converting it into useful resources such as electricity and fertiliser in a clean, efficient and odourless manner.

Improving energy storage

Getting energy from renewable resources is just one piece of the puzzle. The energy must also be stored so that it can be used later. For example, when energy demands are greater than supply, the energy storage systems can discharge their stockpiled energy to the grid.

Several NUS research groups are looking at innovative ways to store energy and Associate Professor Praveen Linga from NUS Chemical and Biomolecular Engineering leads one of these groups. By pioneering Solidified Natural Gas (SNG) technology, he hopes to revolutionise natural gas storage systems.

Natural gas makes over 20 per cent of the world’s electricity and accounts for 95 per cent of Singapore’s electricity. But storing and transporting natural gas in its gas state can be costly and hazardous. Assoc Prof Linga and his team have pioneered a way to rapidly convert natural gas into a non-explosive solid, which can then be easily stored and transported. While many sources of natural gas are not renewable, the team’s technology could be applied to renewable sources such as the biogas generated from food waste by Assoc Prof Tong.

Meanwhile, Assistant Professor Tan Swee Ching from NUS Materials Science and Engineering has been inspired by the natural process of photosynthesis happening in plant leaves wherein the solar energy is concurrently harvested and stored. He mimics a plant leaf in this way by developing semi-artificial photosynthetic systems.

Rather than electrically charging the energy storage devices, he directly charges them with solar energy. His recent work delves into how a single system can be a solar cell and a battery put together – harvesting light, converting it into electrical energy, and storing it at the same time. Asst Prof Tan and his team recently used multiple layers of proteins, which are derived from photosynthetic bacteria, to develop a system that can harvest solar energy to generate electrical signals and store them for future use. This research is one step closer to a self-charging battery that charges when exposed to sunlight.

In nature, plants capture sunshine, carbon dioxide, and water and convert them into glucose – an energy carrier for circulation and storage. Glucose and its derivatives are food and energy sources for plants, animals, and human beings. Inspired by nature, NUS Vice President (Research and Technology) Professor Liu Bin built the NUS Flagship Green Energy Program with a focus on capturing carbon dioxide, water splitting, and converting sunshine into energy-dense liquid fuels like methanol – the simplest alcohol fuel.

In principle, creating green alcohol fuels can be done in three steps. The first is to capture carbon dioxide from powerplants or even the atmosphere. The second is to produce hydrogen from water using solar-powered electrolysis. The last step is to react hydrogen with the captured carbon dioxide to produce methanol. Prof Liu, who is also the Head of NUS Chemical and Biomolecular Engineering, drives the multidisciplinary NUS team that researches transformative energy systems needed for the mass-production of these green alcohol fuels.

Distributing green alcohol fuels can use existing infrastructures with only slight modifications. As green fuels are renewable, they could be vital to move typical industrial processes away from fossil fuels.

Increasing efficient energy use

The final piece of the puzzle is to ensure that when energy is generated and stored, it is used with as little waste as possible. In this way, energy efficiency brings many benefits: reducing greenhouse gas emissions, reducing energy demand, and lowering costs.

An area where energy efficiency is crucial is data centre operations. Data centres are the backbone of the digital economy, but they need to be constantly cooled to operate effectively. Maintaining such controlled environments consumes a lot of energy, resulting in high costs and carbon emissions – particularly for tropical countries like Singapore.

The new Sustainable Tropical Data Centre Testbed (STDCT), established by NUS, the Nanyang Technological University, Singapore, and partners in the data centre industry, will develop energy-efficient alternative cooling technologies to achieve breakthroughs in the tropical data centre environment. The S$23 million programme will pioneer green and efficient cooling solutions specifically catered to data centres in the tropics.

Other than data centres, industrial, commercial and household processes could all benefit from more efficient energy use – and these applications are the focus of the Energy Studies Institute (ESI) at NUS.

The experts at the ESI are committed to answering how economic and environmental benefits can be derived through energy efficiency and conservation. They research energy policies and their national, regional and global implications, and advance the collective understanding of issues related to energy policy development. One key research programme at ESI is the development of integrated energy system modelling and analysis frameworks. Such modelling enables integrated and focused analysis at different scales and time periods, to generate insights for policy-makers to make better decisions and trade-offs in conditions of pervasive uncertainty.

Whether it is research into renewable sources of energy, better energy storage or more efficient energy use, NUS researchers are making important contributions towards enhancing Singapore’s energy security for a brighter and sustainable future.