Page 18 - Vol 33 Issue 34 2021

The Fit for Liquid Air Energy Storage (part 1)
mining Energy Storage

Asif-Hussain

The Renewable Transformation

n the quest to curb global warming, energy markets across the world are shutting down fossil fueled power
Iplants and replacing them with renewable energy sources. This significant transition in the power industry
drives sustainability of our planet and impacts all its inhabitants including us, writes Asif Hussain, SVP of Strategic
Business Development, Sumitomo SHI FW.

Nearly all forecasts are predicting that by 2050, and a dramatic increase in congestion on our inertia of their spinning rotors add up to provide a
most of the electricity produced in the world electric grids. powerful stabilizing force resisting any deviations
will be from intermittent solar and wind. Wind Lastly, wind and solar plants produce power to frequency.
and solar plants make up 18% of the world’s in the form of unidirectional direct current (DC) If there is a disruption in the power balance on
installed electric power capacity today, by 2050 that needs to be electrically synthesized into the grid, say by a short circuit, or a mechanical
this number is expected to nearly quadruple to bidirectional alternating current (AC) before failure at a power plant, this stored inertia acts
65%. This reflects the fact that most new power being connected to the grid. This synthesized instantly to slow the rate of change of grid fre-
plants built over the next 30 years will be mostly AC is called asynchronous electricity and lacks quency, giving valuable time for primary controls
wind and solar. While new fossil, hydro and important characteristics that are needed for (fast reserves) to act to rebalance the grid.
nuclear plants will be built over this same period, stability and reliability of our power grids. Today 82% of the power on the grid today is
an equal amount of this capacity is expected to be In contrast, AC electric generators produce produced by traditional spinning AC generators
retired, effectively keeping their net contribution synchronous power since the frequency of the resulting in a high level of grid stability and
to the world’s power capacity at about the same electricity (Oscillating AC sine wave) they produce reliability. However, as we look out to 2050, this
level it is today. is set by the speed at which the generator rotor number is expected to drop to 32%, less than half
This explosion of wind and solar power spins, typically spinning at 3000 rpm to produce of its current value. Grid stability will also drop
capacity on the grid is essential to change our 50 hertz synchronous power. This electro- proportionally making it much more difficult to
current path to rising global temperatures, but it mechanical coupling connects the spinning maintain grid frequency and voltage during upset
also brings along a new set of challenges to the mechanical inertia of the generator rotor to the events.
power industry. frequency of the produced electricity, giving AC
First, power from wind and solar plants generators the ability to provide mechanical The Role for Energy
depend on the weather and can’t be controlled inertia, passively, to the grid, independent of the
to reliably match load on a minute-by-minute or megawatt-hour energy they produce. This inertia Storage
hourly basis like conventional power plants do for provides valuable voltage and frequency stability
us now. needed during unexpected upsets on the grid. As wind and solar expand across the grid so
Second, in most cases wind and solar plants Before connecting to the grid, each AC will the need for energy storage (ES), both in
are located where sun and wind resources generator needs to align (synchronize) its output scale and distribution across the grid to even-
are optimum but far from major load areas frequency and phase angle (wave staring point) out power and maintain grid stability. Figure 2
(cities, manufacturing hubs, industrial parks, to that already established on the grid. As more illustrate this in a simple example for a region with
commercial centers) leading to higher T&D losses and more generators connect to the grid, the high solar capacity. A similar example could also
be illustrated for regions with high wind capacity.

18 | AFRICAN POWER Mining & Oil Review Vol33 Issue 34 2021