Page 33 - Energize February 2022

VIEWS AND OPINION

Baseload revisited

by Mike Rycroft, Energize

Baseload refers to the minimum demand on a grid over an extended period. With the advent of the energy transition,
it has become the subject of heated disputes, over generation technology, reliability and sustainability. At the heart
of these debates is the fact that zero-carbon energy sources, such as solar and wind, cannot be relied upon to deliver
power whenever needed. But since baseload today mostly comes from fossil fuel generation, what will be the source of
baseload in the future?

decade or so ago, a well-respected researcher published be described as intermittently dispatchable, depending on how
an article claiming that baseload would be unnecessary in much energy is stored at the time of dispatch, and for how long the
A future, as wind resources could be combined to provide a energy is required.
continuous supply of electricity. Current experience with large scale The term “carbon free” is also a misnomer as it applies only to
wind generation in several countries has shown that, although the fossil fuels, whereas some renewable fuels such as biomass contain
wind resource may be continuous in nature, output often drops to significant amounts of carbon, and renewable synthetic carbon-
levels that are concerning. based fuels are also being produced. The correct term would be
Recent articles make similar claims based on renewable “fossil fuel free”, but I suppose the term “carbon free” rolls off the
energy sources in general. There are some experts challenging the tongue, and is easier on the ear, making a better slogan. The term
notion that a baseload supply is necessary or even a good thing. can, however, be misinterpreted to mean any fuel containing carbon,
One notion is that having a diverse range of renewable power and literal interpretation limits the possibilities for future fuels.
systems, including hydro, biomass, wind and solar, can provide a Having cleared up the confusion or created even more, let us
reliable, flexible infrastructure that more than meets the needs of return to the topic of this article, namely baseload. Baseload is a
the network. Current arguments claim that baseload generation concept that describes a characteristic of the power demand on the
will be unnecessary in the future, and that a reliable dispatchable grid side, and is not a feature of the supply side. Basically there is
source of electricity that meets the electricity demand at all demand baseload and supply or generation baseload.
times can be provided using renewable energy (RE) alone. At the
other end of the spectrum, system planners and policy makers Demand baseload (DBL)
are searching for a carbon free replacement for the current fossil Electricity demand on the grid never drops to zero, and there is
fuel fired baseload generation fleet that is not based on RE, which a minimum demand during the year, which is generally termed
implies that in this sector, baseload is considered a necessary baseload. Demand varies during the day, weekly and seasonally and
component of the future fleet. determining the absolute minimum demand to dimension baseload
Much of the debate stems from confusion: confusion between generation can be difficult (see Figure 1).
baseload demand and baseload generation, confusion as to what Demand baseload in a conventional system usually occurs
constitutes dispatchable power, intermittent power, and variable during the late night or early morning hours. Utilities with pumped
power, and lately, what constitutes clean energy. There is confusion water storage (PWS) systems take advantage of this low demand to
regarding the aim of the energy transition which seems to be recharge the PWS systems, which allows more efficient use of the
evolving into a move to a cleaner lower carbon, sustainable and baseload generation. In today’s network and that of the immediate
equitable energy mix, which is not exclusively renewable energy future there are several factors which could affect this.
based, at least in the foreseeable future. The advent of large-scale rooftop solar systems on industrial/
commercial and residential properties had a disturbing effect on
Let’s start with the basic definitions minimum demand, causing demand to drop significantly during
The term intermittent applies to a source which is not available at
all times. The term variable power, usually applied to wind and solar,
is a misnomer, as in general usage, variable applies to something
that can be varied under control (e.g., variable power supply). A
better term would be varying, which describes something which
varies under its own influence. Not all renewable energy sources
are varying. Hydro and biomass can be variable or fixed renewable
sources. Wind is a varying resource, while solar is a periodically
intermittent varying resource.
A dispatchable source is one that can deliver the required
amount of power at the required time for a required period.
Varying sources are not dispatchable. Hydro power, thermal power
sources, and fuel cells are all dispatchable. Energy storage is not
dispatchable, as it requires that sufficient energy is stored. It may Figure 1: Daily demand: Eskom grid January 2022 (Eskom)

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