Page 54 - Energize August 2021

TECHNICAL

Cost saving potential of solar hybrid

systems for microgrids

Information from Suntrace and Reuniwatt

Industrial applications in remote locations, such as mines, often lack connection to the national grid for
power supply. The required off-grid power generation is typically based on heavy fuel oil (HFO) or diesel
gensets in a microgrid. Utilising hybrid systems based on renewable energies like solar or wind in a fuel-
saver concept has increasingly gained interest in the industry.

olar-battery hybrid systems can offer substantial fuel savings and thus a considerable in other words, the maximum fuel savings
reduction in the cost of electricity for existing or newly built mining operations. achievable when hybridising existing HFO
SConsciously integrated, these systems can seamlessly switch between various power gensets with a solar-battery system.
generation and storage technologies, ensuring reliable and safe power supply to the mine. The study shows that a significant
The high accuracy of short-term solar forecasting, by means of sky cams, plays a vital role in share of cheap solar power replacing
identifying the required spinning reserve and planning of the genset dispatch schedule. The 30% to 40% of the annual HFO demand
benefits of hybrid systems have been recognised by mining firms and by 2020 over 1 GW of is economically viable today. The optimal
renewable energy capacity had been installed at mining sites. share and therefore solar-battery system
This article presents the cost saving potential of solar-battery hybrid systems combined size, is very sensitive to CAPEX and fuel
with solar forecasting solutions, using an exemplary case study of an off-grid mine in western price assumptions. And with expected
Africa meeting its demand through HFO based power generation. The key focus is to identify future price reductions for solar and battery
the maximum economically viable renewable share which can be reached for such a system, systems, the optimal share will further
increase, reaching more than 50% of
renewables for new future projects.

Fuel saver hybrid plant concept
The basic concept of a typical hybrid
system for an off-grid mine can be seen in
Figure 1. The HFO engines on the left-hand
side are already installed in this scenario
and constitute the primary source of
energy. To the right, the renewable energy
system comprising of the solar plant, the
battery storage system and a solar power
Figure 1: Basic schematic of an off-grid hybrid plant
forecasting system can be seen.
Figure 2 shows the principal operational
basics of a typical off-grid hybrid system.
The pink line depicts the mine’s total load
which typically remains constant throughout
the day, due to the large consumers such as
the ball mills and the sag mills used in the
mining operations.
Seven gensets (each represented in
green lines) of 5 MW each were considered,
with the blue dotted line representing the
maximum spinning reserve. When the
solar plant (represented in yellow) starts
producing in the morning, it starts to
substitute the genset’s production and
slowly the gensets are ramped down.
Similarly, as the solar power starts to
Figure 2: Operational basics for a genset-solar-battery off-grid hybrid system decrease, the gensets are slowly ramped

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