Is electrification the route to a net zero carbon future? Part 2

Energy generation and transitioning to renewables

As engineers, the approach we often take to fix a faulty system is to identify the source of the fault. Similarly, the path to a Net Zero Carbon energy system is the sustainable generation of energy. This is especially important when transitioning the energy carrier from a carbon intensive source to another source that is perceived to be less carbon intensive.

Certain sectors face practical challenges in readily transitioning to a net zero system. In such cases, utilising a comparatively lower carbon intensity energy carrier is an intermediate step until a long-term solution for a complete and sustainable transition can be found. For example, an immediate and large-scale transition of the transportation sector to net-zero emissions is not practical and instead a gradual transition using energy carriers such as biofuels and electrical energy is a pragmatic option. A similar approach can be applied to heating (space and water) for domestic and commercial applications using heat pumps.

It is interesting to note both these sectors aspire to transition to the use of the ‘magic’ fuel – hydrogen. However, when using transitionary fuels, it must be ensured there is a resulting whole process carbon intensity reduction – if not, the entire approach of using the transitionary fuel will be questionable.

Today’s electricity sector is already responsible for 36%* of current global CO2 emissions (more than any other sector). The largest sources of installed renewable power generation globally are hydropower, followed by wind power and solar PV power; however, the growth in the renewable sector is driven by solar PV and wind, which is strongly forecasted with a continued reduction in new build costs. In certain geographies and markets, new build solar and wind projects are significantly cheaper (lower Levelized Costs of Energy) than their non-renewable counterparts such as coal, gas and nuclear. *Source World Energy Outlook 2021, IEA

The graphs below show the projected global demand in a net zero carbon energy system, along with how much of that demand must be met via renewable sources. The difference between total demand and renewable generation is supplied via non-renewable sources and must be offset via other means. The graphs also indicates the global generation capacity required, by source.

(Source: IEA)

However, the lower build cost of renewable plants doesn’t automatically result in lower energy cost for consumers - a common dilemma, especially during this period of soaring energy costs. That is a whole other discussion for another time.

Problems with renewables

Although we just mentioned that renewable power projects are globally experiencing a period of immense growth, it doesn’t mean that we can just go on a renewable power building spree with the current design of our energy system and hope everything works well.

There are a number of challenges with integrating renewable generation into our energy system and one of the most significant hurdles is the natural intermittency of renewable sources - the sun doesn’t always shine (e.g. at night-time, or when a cloud passes by, overcast days etc), and the wind doesn’t always blow (although you often get one or the other). Due to this intermittency, renewables cannot be dispatchable, meaning they cannot be relied upon to provide electricity in any specific moment like coal, gas, or nuclear plants.

However, there are ways to unlock these challenges, such as combining renewable generation plants with energy storage systems, which charge up when there is surplus generation, and discharge when there is a shortage of generation. Another way to counter the intermittency issues is to interconnect grids, such as through international interconnectors, where of course the weather will likely vary in any given instance. This is akin to hedging bets or holding a diversified portfolio – it minimises risks and losses from a single large event.