Page 61 - Energize August 2022

TECHNICAL

Hybrid power systems for

remote sites

Hybrid systems have become an essential part of distributed and own generation systems, both on
grid and off grid. Lower costs and increased capacity of storage components and renewable energy
systems have made this system a widely available source of energy. The projected availability of
hydrogen and hydrogen carriers, combined with fuel cell development, makes the zero-emission hybrid

energy system a distinct possibility.

by Mike Rycroft, Energize

ncreased load shedding and the removal of licensing Hybrids or microgrids?
requirements for generation plant less than 100 MW has The distinction between hybrid power systems and microgrids is
Iresulted in an increased interest in large own-generation plant. becoming blurred, especially in the area of industrial microgrids/
Originally used for remote mines, the advantages of the large hybrid systems, that are functionally the same. The main distinction
hybrid system and the need for reliable power means that hybrid is that a microgrid has several distributed energy sources, and
power systems are being considered by other sectors as well. serves multiple billable points of consumption, whereas the
Hybrid electrical energy systems (HESs) combine different hybrid system will normally only have one source of each type of
generation and storage technologies in a single system, with generation, and will serve a single customer, (usually the owner
improved benefits compared to a system that depends on a single of the system), although on-site IPP owned hybrid systems are in
source. Originally designed as a combination of conventional, existence. Functionally the two systems are essentially the same,
non-renewable generation (ICE) with battery energy storage the common factor being the control system.
systems (BESSs), their design has now expanded to include systems
that are based on a combination of renewable and non-renewable Hybrid systems range in size from small (tens of kW) to very large
energy systems, and different energy storage systems (e.g., multi-MW and include:
BESSs, fuel cells and supercapacitors . The sector also includes • Residential and small business grid connected, usually consisting
systems that that are based entirely on renewable energy and of solar and battery storage with a smart controller.
storage. HESs have also grown in capacity from small, off-grid • Grid connected industrial hybrids, usually consisting of solar
systems of a few kW capacity, typically designed for low voltage DC and bulk storage with ICE driven or fuel cell supplementary
and AC, to large multi-megawatt systems and medium voltage grid- generation and a smart controller.
connected systems. Fig.1 shows a typical hybrid system layout. • Large off-grid systems that use large solar and bulk storage,
The proportional capacity of each element will depend on the together with IC driven or fuel cell generation, together with
purpose of the hybrid. wind generation in some instances.

Because of the overlap in smaller systems this article will focus on
large off-grid hybrid systems, where the main focus at the moment
is mine power installations.

Development of hybrid power sources for mines
The only power source for remote mines was originally ICEs
running on diesel or heavy fuel oil, a situation that was affected by
the high cost of transport and uncertain supplies. The advent of
solar PV and the decreasing price made solar PV a possible option
to reduce the fuel consumption during daylight hours. PV had a
problem though with passing clouds, causing stop/start operation
of the primary power system. Increased availability and reduced
price of battery electrical energy storage (BESS) led to the addition
of battery storage to cater for short reductions in PV output.
Further reduction in the cost of both PV and BESS led to greater
Figure 1: Typical hybrid system layout use of PV, almost as a prime source of energy. ICE generation costs

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