The Complexity of a Zero Carbon Grid

I’m excited to present this Energy Insights post. I’m highlighting a few interesting insights from the The Complexity of a Zero Carbon Grid show. This is very special as The Interchange podcast has only been publicly relaunched recently.

The show considers what may be necessary to get to levels of 80-100% renewables. Stephen Lacey and Shayle Kann host the show with Jesse Jenkins as the guest.

The concept of flexibility

Jenkins observes that the concept of flexibility of electrical capacity appearing in literature. Flexibility means how quickly an asset is able to respond to change.

A combined cycle gas turbine plant is usually more flexible than a coal or nuclear generator. One reason for this is the ability to control plant electric output by modulating the supplementary burner gas consumption.

We will need flexibility on a second, minute, hourly or seasonal basis.

This concept of flexibility was also recently touched on by the excellent Energy Analyst blog. Patrick Avis notes that we need both flexibility (kW or kW/min) and capacity (kWh) for a high renewables scenario.

The post Flexibility in Europe’s power sector could easily be enough material for a few Energy Insights posts. Well worth a read.

One investment cycle away

Jenkins observes that the investment decisions we make today will affect how we decarbonise in the future. Considering the lifetime of many electricity generation assets, we find that we are only a single investment cycle away from building plants that will be operating in 2050.

Most deep decarbonisation roadmaps include essentially zero carbon electricity by 2050. We need to ensure that when the next investment cycle begins we are not installing carbon intense generation as it would still be operating in 2050.

Table 1 - typical lifetimes of electricity generation plants (years) given by Jenkins
Nuclear	40-60
Wind & solar	30 - longer
Gas & coal	30-40

For both gas and coal the implied cutoff date for plant operation to begin is between 2010 – 2020.

Increasing marginal challenge of renewables deployment

The inverse relationship between the level of deployment of renewables and the marginal value added is well known. Jenkins notes that this relationship also applies to the deployment of storage and demand side response.

As renewable deployment increases the challenges for both storage and demand side response also increase.

#### Seasonal storage technologies

1 – Power to gas

Electricity -> hydrogen -> synthetic methane.

Figure 3 – Apros Power to Gas

Intermittency of the supply of excess renewable generation means that power to gas asset wouldn’t be fully utilized.

Didn’t cover the possibility of storage of electricity to allow a constant supply of electricity to the power to gas asset.

2 – Underground thermal

Limited to demonstration scale.

Didn’t cover the feasibility of generating electricity from the stored heat.

I would expect that the temperature of the stored heat is low. Perhaps the temperature could be increased with renewable powered heat pumps.

Thanks for reading!