IEEE Power & Energy Magazine - September/October 2021 - 78

gas-fired generation facilities (45% of installed capacity) and
a few large coal-fired generation facilities (21%) located near
coal-mining operations in the southwest of SWIS. These
facilities combined accounted for almost 90% of large-scale
energy generation supplied to the grid in 2019-2020. The
remaining generation was primarily provided by utilityscale
wind generation located in the north of SWIS.
Recent additions of large wind farms and the growing
contribution and impacts from rooftop solar are rapidly
changing the generation mix. Scenario modeling in 2020
indicates renewable generation will outstrip growth in other
generation types over a 20-year modeling horizon.
Small, distributed rooftop solar represents about 18%
of total generation capacity and is estimated to contribute
around 10% of total energy supply. This is difficult to measure
accurately as it is masked by serving behind-the-meter
and distribution level loads, reducing the total required from
large transmission-connected generators.
The contribution of energy generated by rooftop solar
photovoltaic (PVs) is leading to low customer demand from
the grid in the middle of the day and a steep ramp-up to the
daily evening peak. If current trends continue, AEMO has
forecast midday low-load conditions will pose a significant
risk to the power system as soon as 2022.
DERs in Western Australia
DERs cover a wide range of technologies and services
that can deliver value across different parts of the electricity
supply chain, including renewable generation such
as solar PVs, energy storage, electric vehicles, and technologies
that residential consumers can use to manage
their electricity demand (e.g., air conditioners, hot water
systems, pool pumps, or smart appliances). DERs can be
located within a customer's premises (i.e., behind-themeter)
or connected directly to the distribution network.
Australia is a global leader in distributed solar uptake rates
with Western Australia being among the highest Australian
jurisdictions. Unlike other countries where solar has primarily
been associated with utility or large commercial installations,
uptake in Australia has been largely driven by small
household installations. Almost one in three homes in SWIS
has solar PVs, with more than 3,000 households adding a
solar PVs system each month. AEMO estimates that 50% of
households will have solar PVs in the next 10 years.
The popularity of rooftop solar PVs in Western Australia
is driven by a favorable climate and solar resource, high levels
of homeownership and suitable housing, installer competition,
and financial incentives, including beneficial tariff
structures and government subsidy programs.
Rooftop solar PVs are ideally suited to the Western Australian
climate. SWIS experiences an annualized average of
8.8 h of sunlight a day, and Perth has the highest number of
cloud-free days of all Australian capital cities.
Over 75% of all dwellings in Western Australia are freestanding
houses, with medium- and high-density dwellings
accounting for 21% of the housing in 2016. Residential lot
sizes are also larger than the Australian average, leading to
larger roof areas ideal for rooftop solar PVs.
At the same time, uniform flat tariffs, technology cost
reductions, and subsidies have provided a strong price signal
incentivizing solar PVs. The household retail tariff, comprised
of a relatively small, fixed charge of AUD$1.05 per day and
a flat rate of AUD$0.29/kWh at all times, disproportionately
recovers fixed costs through variable charges. This structure
encourages the installation of DER generation as self-generation
allows households to avoid buying electricity from the grid
and therefore paying for fixed system costs over that period.
Synergy is also required to offer a solar feed-in tariff for
Onslow
Western
Australia
Western
Australia
residential customers. Before November 2020, the default
Renewable Energy Buyback Scheme offered AUD$0.071/
kWh for all customer solar PV exports. Federal government
financial incentives (known as the Small-Scale Renewable
Energy Scheme) and declining technology costs, combined
with competitive pricing from economies of scale within the
local industry, have also contributed
to the uptake. The combination
of these factors means the
payback period for a new rooftop
solar PV system is close to three
years on average, making it an
attractive investment proposition
for households. Indeed, Western
Australian customers are installing
rooftop solar PVs at an accelerating
rate (Figure 2).
The uptake of other DERs is
Perth
Horizon Power
Microgrids
(a)
SWIS
(b)
figure 1. (a) Western Australia and (b) the SWIS and Horizon Power microgrids.
78
ieee power & energy magazine
relatively weak but is expected
to increase as costs decline over
time, particularly for technologies
(such as household batteries and
electric vehicles) that complement
solar PV investments. Household
september/october 2021
IEEE Power & Energy Magazine - September/October 2021

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