Researchers from Electric Energy Studies Institute of State Electric Grid Company of Shandong Province and School of Electrical Engineering of Shandong University proposed a technology capable of significant improvement of the resumable energy usage efficiency. For that purpose they combined e-vehicles with a new type of engines EHED – electric-olefin-hydrogen electro-magnetic units turning redundant electric power generated by wind and solar plants into heat, hydrogen and olefins – valuable feedstock for chemical industry.
The researchers focused on resolving the problem very well known in the Northern regions of China. In the winter they have long heating season coinciding with generation of wind energy, while as the consumption during this season remains relatively low. Eventually, the significant portion of the clean energy is not used: only in 2023 the unwanted release made 12 bn KW·h, which is equivalent to the energy contained in 4 mln tons of coal. These are direct economic losses and at the same time – the lost opportunity to decrease the emissions.
EHED system developed in Shandong operates on the same principle as an electric furnace, where electromagnetic heating substitutes for traditional flame. Light hydrocarbons in such unit are converted into ethylene, propylene and hydrogen, and the released heat is stored in the tanks with molten salts. The overall energy efficiency exceeds 95%, and with account of heat recovery the unit turns out to be approximately 20% more efficient vs traditional electric boilers. Every MW-hour of redundant energy allows for receiving 3.2 GJ of heat and 0.12 kg of hydrogen.
The key addition to the proposed model are e-vehicles – not like consumers of energy, but as accumulators capable of releasing this energy back into the grid (vehicle-to-grid model).
The technology proposed by Chinese scientists may be illustrated using a simple example. In the evening the e-vehicle owner connects the car to the charging unit, and the intelligent system connected with the grid and EHED units analyzes the wind generation forecast and fixes the redundant energy at night. Then the system offers the owner to switch the charger to the night hours, when the grid load is minimal, and it gets the maximum of the wind energy. In the morning, when cumulative consumption is growing, and the wind generation goes down, the system offers the drivers to return a small portion of the accumulated charge to the grid. At the same time, the volume of such return is strictly limited to maintain sufficient drive range.
When there are many such owners connected to the grid, the e-vehicles turn into a distributed system of energy accumulation mitigating the morning peak loads and increasing the sustainability of the grid.
The simulation results proved the efficiency of such integrated approach: when only e-vehicles or only EHED units were used separately, the energy losses decreased insignificantly – down to the level of circa 3%. Joint usage of these two elements decreased the losses down to 1.37%, and aggregate OPEX of this energy system went down by 57%. Operating as mini power plants, e-vehicles allowed for the system not only to live without buying energy from external grid, but even to sell its redundant energy to the external grid. The value was created not only by electricity: EHED simultaneously generate heat for seasonal heating, hydrogen for transport and industry, and olefins for chemical industry.
Now the scientists propose to switch from simulation to pilot projects: deploy EHED in Northern regions with high level of wind generation and test simultaneous control of EHED and e-vehicles in municipal grids.
