Decarbonisation Technology August 2022 issue

Figure 1 An estimated 31% of greenhouse gas emissions can be traced to electricity and heat generation, according to the World Resources Institute Credit: World Resources Institute

Since then, we have become accustomed to using diverse types of energy in forms such as combusting fossil fuels, wind energy, and solar energy, which are generally converted to electricity for our use. Yet, in switching from chemical to renewable energy sources such as solar, we are realising there is a shortfall in being able to provide energy whenever it is needed and wanted. To take full advantage of renewable energy as we work to displace fossil fuels in our drive to decarbonise, it is now necessary to store energy during peak production hours when it exceeds demand – which, subsequently, can be used when demand exceeds production. With that, there are additional factors to consider. As an example, how long does the energy need to be stored? Will energy stores need to be loaded and unloaded in seconds or minutes? Or are the needs more seasonal, requiring the need to store energy for months? All this dictates storage size in closing the gap between generation and utilisation – and subsequently, the required storage technology. That is not to mention that, with very few exceptions, stored energy will be used as thermal or electrical energy – the latter of which

is also the most difficult energy form to store for long periods of time. The most common method of storing electrical energy today is in batteries. However, batteries are limited in how much and how long they can store energy due to technical and economic limitations. Consequently, other technologies are needed to store large amounts of energy for long durations. Such technologies are used as intermediate storage, meaning they store energy in a form that can be used to produce ‘on-demand’ electricity. Long-duration thermal energy storage LD-TES has been identified as a critical enabler for the large-scale deployment of renewable energy – in particular, within CSP applications. Before going any further, it is important to differentiate CSP from more commonly known photovoltaic (PV) technology. PV is the direct conversion of sunlight into electricity using the photovoltaic effect in semiconducting materials to directly generate electricity. Storing the electrical energy from PVs is economically restricted to battery technology, and current battery technology is generally limited to short-


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