Page 36 - Energize May 2021

TECHNICAL

The business case for microgrids

by Robert Liam Dohn, Siemens

To protect themselves from power outages, many companies installed standby generators. However, these
generators emit dangerous toxic gases in their exhaust and are costly to run. Some companies have opted
for rooftop solar PV and batteries to reduce their reliance on the grid since they are cheaper to operate and

emit no exhaust gas. Microgrids offer such companies an ideal solution: Access to power from multiple
sources at the lowest possible cost. When grid power is cheap, the microgrid uses that; when the tariff
increases at peak times, the microgrid draws from the battery. A combination of solar PV and grid power
are used to keep the batteries charged and supply the business’ demand during the day. n

Although this article by Robert Liam uses an American study to demonstrate the benefits, it is applicable in South Africa too. – Ed.

he utility industry is in the midst with, or independently from, the main grid. The primary purpose is to ensure reliable,
of grid modernisation efforts that affordable energy security for commercial, industrial and federal government consumers.
Tramped up in large part following Benefits that extend to utilities and the community at large include lower greenhouse gas
the United States’ Northeast Blackout of (GHG) emissions and lower stress on the transmission and distribution system.
2003. That massive blackout was a wake- The core of a microgrid will be one or more small (under 50 MW) conventional generation
up call to utilities and consumers alike, assets (i.e. engines or turbines) fuelled by natural gas, biomass or landfill methane. When
compounding the concerns about climate connected to the main grid, microgrids will rely on a mix of power generation sources
change, the burgeoning population and depending on the metric to be optimised (cost, GHG, reliability). Specialised hardware and
scarcity of natural resources. The blackout software systems control the integration and management of the microgrid’s components and
spurred the industry to aggressively pursue the connection to the utility (see Figure 1).
a more intelligent power grid.
At the same time, energy consumers The microgrid vision
became more concerned about their A microgrid includes generation, a distribution system, consumption and storage, and
local power quality and efficiency of the manages them with advanced monitoring, control and automation systems. The critical first
system. Local brownouts are a nuisance step of pursuing a microgrid solution is a permanent reduction in consumption (electricity,
and have driven consumers to take greater water and gas). This will give the consumer near-term cost savings driven by measured and
responsibility for their electricity supply – verifiable conservation measures.
particularly industries and communities
with a critical need for reliable power.
Investments in energy efficiency, renewable
generation and power monitoring and
control systems increased, often resulting
in a diverse and disparate array of installed
technologies. This article summarises the
vision, benefits, strategy, and business
considerations of microgrid solutions.
The vision is to integrate these
technologies into automated microgrids that
connect seamlessly with the main grid and
may be grid-independent when needed. The
result is a solution that enhances reliability,
efficiency, security, quality and sustainability
for energy consumers and producers alike.

Microgrids defined
A microgrid is a discrete energy system
consisting of distributed energy sources
(e.g. renewables, conventional, storage)
and loads capable of operating in parallel Figure 1

energize | May 2021 | 34