Why dynamic harmonisation of energy systems is the key to the next phase of decarbonisation

Electrification with renewables will be the primary mode of the energy transition, and its weaknesses are causing the transition to stall

It is clear that electrification powered by renewable energy will be the primary mode of the energy transition, but its limitations are driving up costs and causing the transition to stall. To solve these problems, we need to see electricity as just one part of an integrated energy system, in which different modes of energy, and the work they power, are optimally coupled, allowing the specific characteristics of one to be used to optimise another. Addressing the challenges of variable renewable energy requires the energy system to be modulated in both space and time, which in turn demands an integrated approach to systems design. As the potential of green hydrogen rises in the minds of developers and policymakers, it should be considered not as a separate energy system for niche cases, but rather as a fundamental element of an integrated energy system. Green Hydrogen is not only a high-value, zero-carbon fuel, it can also play a significant role in balancing the electricity system.

It’s time to discover dynamic harmonisation, the means by which we can optimally integrate multiple modes of energy and the work that it powers

Work happens whenever we are using energy and movement. When we think of work, we typically think of the off-ramps of the energy system: using electricity in an LED to produce light or using petrol in an engine to produce forward motion. But we also have plenty of work within the energy system. In fact, the work in an energy system is equally distributed between generation, distribution and consumption. Using electricity to move lithium ions from the cathode to the anode of a battery during recharging and using hydrogen in fuel cells to produce electricity are both examples of work.

We can think about harmonisation of work as taking place in two different dimensions: space and time. Throughout human history, we have adapted our work to the energy system. Our pre-modern ancestors milled wheat where there was a river or reliable wind to turn the mill, and only at times when the river ran or the wind blew. Today, we often refine oil in coastal areas, typically near oil production, and we smelt steel and produce cement near coal deposits to fire the smelters. Since the industrial revolution gave us steam power and then electricity on demand, however, work we see has rarely needed to be coupled to energy in time, and only the most energy intensive processes are still coupled in space.

The transition to renewable electricity as our primary energy source means that we no longer have reliable energy on demand. Rather, like the medieval miller, we are now subject to the vagaries of the sun and the wind. And temporal instability comes on different timescales. At one extreme, periods without sun or wind can drive tremendous, destabilising price spikes. At the other extreme, fluctuations in supply of renewables and volatile demand from electrification mean that power prices can switch from negative (the network paying users to take power) to positive price spikes in as little as fifteen minutes. On a larger timescale, the famous solar duck curves illustrate that the daily ebb and flow of renewable generation does not match the daily ebb and flow of consumer demand. Excess generation during the day (the belly of the duck) and a sharp ramp as renewable generation comes off and demand rises in the late afternoon (the duck’s steep neck) can now be seen in energy markets everywhere.

Source: CAISO

Without modulation through dynamic harmonisation, we are forced to curtail renewables

Broadly speaking, there are two options to address this: limiting renewables or dynamic sector harmonisation.

Option 1: we could limit the scale of renewable generation and complement it with some form of dispatchable thermal generation. Although most of the world’s electricity markets are taking this approach today, there are serious downsides. Renewable generation is cheap and getting cheaper, but maintaining thermal generation to balance the network means that power prices for consumers and industry will continue to rise. At the extreme, the only way for a power system to get to zero carbon with this approach is to either provide dispatchable thermal generation using fossil fuels with carbon capture and storage, expensive technology that continues to fail to deliver, or flexible small nuclear reactors, an expensive variant of an expensive technology that has consistently failed to deliver on time and budget. Given the cost implication, it is hard to imagine that a system that chose to achieve stability by limiting variable renewable energy would achieve zero carbon generation quickly enough to address climate change.

Option 2, dynamic harmonisation, is more attractive, but less well understood. The limiting approach would mean that the energy transition either fails or becomes unbearably costly as we seek to fit it within the constraints of the existing electricity system. Dynamic sector harmonisation transitions the energy system to meet the twin needs of decarbonisation and cheap reliable energy. The approach of dynamic sector harmonisation adjusts specific work to match the available energy balance, allowing cheap variable renewable energy to meet our needs for carbon-free prosperity.

Before we look at how this works in the grid, let’s look at a much simpler energy system: my house. The solar panels on my roof produce large amounts of heat during the day, when I have little need for heat. I could limit the output of the solar panels during the day and find another source of energy, like natural gas, to provide heat at night, forcing the energy supply to match the demand for work. Instead, I have a large thermal storage tank, enabling me to shift the work of heating to the daytime at the lowest cost, introducing the work of hot water storage to time shift my cheap energy, allowing me to use that energy to do the work of heating my radiators at night. In this simple case, optimal coupling the work of heating with the variable solar energy yields a cheaper and lower carbon solution.

Dynamic sector harmonisation enables renewable energy to flourish

The same basic principle applies at grid scale. However, it needs us to move from relatively simple static coupling to dynamic harmonisation of modes of energy. This is because we are economically path dependent on an AC signal. Over the last 130 years we have invested immense amounts of capital assuming an alternating current. We literally can’t afford to change: every building, appliance and industrial application globally was designed for an AC signal. Today we have a system of energy distribution and consumption designed assuming a form of generation, large central thermal generation using fossil fuels, that is being phased out.

Let’s look at how dynamic harmonisation can work across three different time horizons: second-by-second, within the day (diurnally), and across multiple days.

Time

My solar heating system is an example of diurnal modulation through coupling. At grid level, a degree of diurnal modulation can also be provided through simple coupling with work that only serves to shift the time that electricity is available, like pumped hydropower storage and grid-connected batteries. Pumped hydropower is a solution dependent on geography, and far from universally applicable. As for grid-connected batteries, the limited numbers of times batteries can cycle both limit their service life and, as we’ll see shortly, make them uneconomical for system modulation across both shorter and longer time scales.

Longer temporal modulation presents essentially the same challenge as diurnal modulation but requires larger energy stores. Both hydrogen and pumped storage can achieve this, as the size of the hydrogen tank or the size of the reservoir are a relatively small part of the capital cost, and the same water pump or electrolyser can simply fill a larger store, just as the same turbine can be powered for longer from the larger store. By contrast, in a battery the means of energy conversion (the pump or electrolyser) and the store are one and the same, making longer-term storage uneconomical.

We also need modulation across much shorter timescales within the day. Given that the frequency of the network must be maintained within plus or minus 1% at all times, generation can overshoot and undershoot very easily, with big swings in demand for additional generation or additional load.

In the many electricity markets, these swings are captured as tenders from the network operator every 15 or 30 minutes for additional supply or additional load. To address this problem through optimal harmonisation, we need to be able to rapidly adjust the energy demand of and supply from the work with which we are dynamically harmonising the grid. Batteries do this badly, as the cost of cycling makes them uneconomical as a means of absorbing short-term spikes or supplying energy back to the grid during short-term periods of under-generation.

Space

Not only did the medieval miller have to adapt to the vagaries of when the wind blew, but he also was constrained in space. Much as farmers might have liked to mill their grain in the valleys where it was farmed, the miller had to build his mill where the wind or the river was. Oil removed the need for harmonisation in space for almost all types of work. Oil is easy to transport, and cheap and easy to store. With oil, only a small number of high-temperature, energy-intensive activities, like smelting, really needed to be located near energy sources. For everything else, one could bring the energy to the work, either burning the oil directly or using it to generate electricity.

Like the miller, we are now constrained by the vagaries not only of when the energy is available, but also of where it is available. Oil is even more constrained in space than renewable energy, but the oil industry became experts at extracting oil wherever it was available—and indeed my early career in the oil industry involved some truly unusual places—and transporting it where it was needed. The difference between oil and renewable energy isn’t that where they can be produced is constrained, but rather than one (oil) can be easily transported, while the other (renewable energy) is difficult to transport. At the extreme, some experts now worry that the energy transition means that energy intensive industry will have to move to countries with ample sun, like Spain, Saudi Arabia, Chile and Namibia.

Dynamic harmonisation ensures that every mode of energy is put to its best possible use

Dynamic harmonisation can help to solve both of the challenges of modulation: time and space.

For modulation in space, dynamic harmonisation allows the energy system to take advantage of the particular characteristics of different modes of clean energy to address different transportation challenges. Electricity can be sent overland with power lines, but there are technical and cost limitations to the distances that undersea HVDC interconnectors can bridge. Hydrogen is complex to pipe across land, as it has a low volumetric energy density and causes embrittlement of standard pipelines, but it can be converted to ammonia quite efficiently and transported by sea. Operating electricity and hydrogen systems in parallel would require separate transportation systems for both modes of energy, but dynamic harmonisations ensures that energy can be shipped by sea as ammonia and transported overland as electricity, and that hydrogen can then be produced at the point of demand, not the point of renewable generation.

For modulation in time, dynamic harmonisation ensures that renewable energy is put to full use when its available and supplemented with other modes of energy when it isn’t. Rather than shifting the timing of the energy to suit the work, we shift the timing of the work to suit the energy. This can mean shifting industrial activities to times when renewable energy is likely to be plentiful, but to take full advantage of the integration of two modes of energy, we need to use peaks in renewable generation to produce another mode of energy, which can be both used directly and used to fill troughs in renewable energy production. Batteries, pumped storage, hydrogen and other forms of chemical storage are all candidates, but hydrogen stands out as the only mode of energy that can both be used directly for a number of productive purposes and can supplement electricity supplies.

Enoda’s HERA industrial green hydrogen microgrid architecture enables both types of modulation by locating hydrogen production at the point of use, eliminating the need for costly and technically complex overland transportation of hydrogen; providing balancing services to the grid by generating green hydrogen from waste and low valued electricity; and using the hydrogen to generate power for the industrial site and provide power back to the grid during periods of under-generation, load following renewables. Dynamic harmonisation enables HERA to crush the cost of delivered green hydrogen by 70%, making it the most cost-effective viable decarbonisation pathway for industrial combined heat and power.