The Paris climate agreement aims to limit global warming to 1.5 degree Celsius compared to pre-industrial levels. Leading the way, the EU has set an action plan aiming to reach net zero greenhouse gas emission in Europe by 2050. As a part of this European Green Deal, the commission has tabled the ‘Fit for 55’ package that aims at reducing greenhouse gas emissions by at least 55% by 2030 and, ultimately, climate neutrality by 2050. To achieve these ambitious targets, transport and industry sectors must be fully decarbonized. In addition, today’s power systems must be fully decarbonized and undergo major energy transition by including large share of renewable energy sources in the existing power system.

The strength and quality of the power system is maintained by keeping the correct frequency in the grid. When load is switched on, frequency falls and there is a need to increase power production to keep the power system in balance. If the frequency falls too much due to large disturbance or if there is not enough power production at the right time, then the electricity outage can occur (Texas and Queensland). That is why system inertia is important. Inertia is the ability of power system to oppose the changes in frequency due to resistance provided by kinetic energy of rotating mass connected to the system. The kinetic energy stored in the rotating mass buys the time to increase and decrease the active power, to adjust the frequency and to avoid any electricity outages.

New converter-based technologies are emerging and are being connected to the grid that lacks the inherit capability of system inertia. These converter technologies (Grid following and Grid forming) are usually equipped with important functionality of FFR (Fast Frequency Response). FFR is an important functionality that can react in 2 seconds or less to compensate for less inertia in the power system but requires detection, filtering, and measurement. FFR is not an inherent response and does not replace inertia. Nevertheless, grid forming converter can provide virtual inertia by emulating synchronous generator characteristics in grid integration. Grid forming converter is voltage source converter and has its own internal voltage phasor, like EMF of a synchronous generator, which drives its inertial response against the moving phasor of grid voltage. The internal voltage phasor of the grid forming converter is initially not affected by the perturbation, causing an almost instantaneous variation of the current phasor. This is highly attractive to system operators, however, depending upon the fault event, it might cause rapid growth of current, jeopardizing the converter hardware component. Therefore, optimal technology is needed to limit the fault current under fault condition with voltage control mode. Some of these technologies are ongoing research topics and are still to be tested on different real site conditions (Victoria Tesla battery).

The other aspect to the ongoing transformation of energy sector towards carbon free solutions is future fuel development work. The key to sustainable future fuel is hydrogen whether the fuel is synthetic methane or green ammonia. Sabatier process that produce synthetic methane through chemical reaction between carbon dioxide and hydrogen requires relatively high temperature and low pressure. Similarly, Haber-Bosch process converts atmospheric nitrogen to ammonia by reaction with hydrogen using a metal catalyst under high temperature and pressure. These processes require proper infrastructure and most importantly efficient production of hydrogen. Therefore, the foremost and essential aim towards carbon free solution is to decarbonize hydrogen production.

The feasible production of green hydrogen is only made possible by the rapid decline in the cost of renewable energy whereas the production of blue hydrogen is possible by accelerating carbon capture technology development and through innovations. Today, there are still some challenges and risks with green hydrogen. Even though the price of the electrolyser is going down, the cost of green hydrogen is not yet competitive.  The cost of fossil-based hydrogen is 1.5 euros/kg for the EU, blue hydrogen is 2 euros/kg and green hydrogen is 2.5-5.5 euros/kg (Q&A Hydrogen strategy).  Hydrogen is highly flammable gas and special care and safety standards are needed from production, transport, and storage to use. For example, hydrogen can be stored with 700 bar storage pressure but then requires huge modifications in the storage tanks.

The transport and energy industry are on a decarbonization journey. It is essential to bring down the cost of renewable electricity by including the large share of renewables but without compromising the strength and quality of today’s existing energy system. The synergy between robust and proven conventional technologies and emerging green technologies is the only key to enable sustainable and resilient energy systems of tomorrow. 

References

R. Rosso, X. Wang, M. Liserre, X. Lu and S. Engelken, “Grid-Forming Converters: Control Approaches, Grid-Synchronization, and Future Trends—A Review,” in IEEE Open Journal of Industry Applications, vol. 2, pp. 93-109, 2021, doi: 10.1109/OJIA.2021.3074028.

Eriksson, R., Modig, N. and Elkington, K. (2018), Synthetic inertia versus fast frequency response: a definition. IET Renewable Power Generation, 12: 507-514. https://doi.org/10.1049/iet-rpg.2017.0370

Rezkalla, M. M. N. (2018). Emulated Inertia and Frequency Support from Fast Acting Reserves. Technical University of Denmark, Department of Electrical Engineering.