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Cambridge University Science Magazine
In recent years we have witnessed extreme heat driving up global temperatures; sparking record numbers of forest fires; and prompting drastic shifts in rainfall patterns, causing both droughts and floods. And it has been known for decades that the emission of greenhouse gases into the atmosphere from the wholesale burning of fossil fuels is trapping heat in the atmosphere and driving these global climate shifts. Despite this, there is a relative lack of concern about taking action to halt our reliance on fossil fuels. However, part of this inaction can be attributed to the sheer extent to which existing infrastructure must be reengineered.

One of the foremost requirements for an economically sustainable transition is the need to ensure the stability of the electrical distribution grid. As nearly all power grids run on alternating current, current must be fed into the grid and withdrawn at the right points in time: any variations in frequency or voltage will interfere with this timing with potentially disastrous implications for anyone connected to the grid. Thus, grid stability depends on a carefully choreographed flow of energy from producers to consumers, ensuring that power is supplied at exactly the rate it is consumed. In the past, this was not an issue, as responding to fluctuations in electricity demand was a simple matter of burning more or less fossil fuels.

But now, sources of energy such as solar or wind energy have upended the old axiom that power plants always produced exactly as much energy as was expected of them. This is since their energy production is by definition dependent on the weather, which if any, is inversely correlated to energy demand. It is possible to curtail production from these sources when there is surplus production, but this represents a needless waste of resources in order to build this excess capacity, which may still be unavailable when most needed. This creates a situation where the price of energy fluctuates to a greater extent throughout the day, and even across the seasons, as prices fall whenever wind and solar are abundant and vice versa when they are scarce. These fluctuations can be severe to the point where prices may turn negative or increase by several orders of magnitude, and ultimately lead to power outages if they exceed the ability of the local grid to compensate for. We see, for example, a 'duck curve' in areas with high deployment of solar energy, where energy prices peak during the early morning and late evening when solar energy is unavailable but when electricity demand has started to increase.

Of course, these patterns of local oversupply and shortage could be mitigated to some extent with grid scale energy storage. However, since these imbalances can persist across days and months, it becomes necessary to explore different types of energy storage in order to cost effectively target this issue over different time scales. Thus, for instance, grid scale batteries are ideal at blunting the impact of transient mismatches in supply or demand, but are expensive to build. Meanwhile, other techniques such as gravity or thermal storage can cost effectively store large amounts of energy, but are slower to respond and are less efficient. These, however, can scale to the sizes needed to offset seasonal deficits in supply or demand.

Instead, it is often more useful to improve the interconnectedness of power grids with the construction of more electrical transmission lines, so that excess power generation ability can be put to work to cover a deficit elsewhere. Moreover, the profitability of generating electricity from green energy sources such as solar, wind, or geothermal is determined by the immutable requirements of local geography, land availability, and so on, rather than of fossil fuel availability and the cost of delivering electricity. Thus, electrical transmission lines often have to be built to connect these new power stations to traditional sources of electricity demand.

Even then, this may not always be possible for political or practical reasons. For example, the state of Texas has historically refused to integrate with surrounding power grids to avoid regulatory oversight, while Japan has two power grids that have very limited interconnection capacity as they run at different voltages and frequencies. From a practical standpoint, the losses in long distance transmission lines also meant that it was always more economical to build power plants as close as possible to wherever the energy they produced would be required, and then design transport infrastructure around the logistics of bringing the necessary quantities of fossil fuels there.

One solution would be to operate transmission lines at ever higher voltages in order to minimise the current that flows through them, thus mitigating resistive losses without having to lower resistance (these require larger diameter cables which are more expensive and require stronger supports). However, as voltages approach the megavolt range, ever more care has to be taken to ensure adequate clearance around each wire in order to prevent arcing between wires, and components must be redesigned to handle higher voltages. A better option has been the adoption of high voltage direct current in these transmission lines. These sacrifice some simplicity in terms of the voltage conversion process in exchange for decreased resistive losses at a given voltage as well as providing the ability to transfer power between unsynchronised grids.

Yet another issue stems from the difficulty of reducing the carbon footprint of transportation. Weight and volume are at a premium, as larger and heavier vehicles are more complicated to build and power. In fact, fossil fuels are uniquely suited for this task as they are very energy dense and get consumed as they are burned up, meaning that vehicles powered with them can be small and light, with the overall weight of the a vehicle decreasing as the fuel is used up. However, this results in a significant proportion of anthropogenic carbon emissions.

Electrification of the transportation sector is one solution, as this enables the centralisation of energy production which improves efficiency and for the decarbonisation of the transportation and electricity sectors to occur in lockstep. Even then, in situations such as planes or trucks where energy density is crucial, the energy and power density of batteries still leaves much to be desired. In these cases, it might be better to fuel them with synthetic fuels with reasonable energy density. We can, for instance, convert crops into biofuel, although the entire process is highly inefficient compared to what can be achieved with solar panels, and competes with human food production. We can also directly manufacture our own fuels, although this is itself problematic as we currently lack the means to produce large quantities of synthetic fuels cost effectively without relying on fossil fuels as a feedstock. Just as the combustion of these fuels into carbon dioxide and water generates large quantities of energy, so do the methods needed to regenerate these fuels require just as much energy.

Indeed, the prospect of decarbonising an economy is a daunting task that requires the reengineering of the infrastructure that we take for granted as well as the rethinking of the assumptions behind their construction. While it can be done, the cost and complexity of doing so means that in the absence of significant government interventions, market forces will conspire to result in inaction. And yet — as the increase in extreme weather events in recent years has shown, and will continue to show — the impact of climate inaction will only continue to increase until concrete steps are taken to initiate these fundamental changes.

Clifford Sia studied medicine at St. Catharine's College. Artwork by Sumit Sen.