2. Current Electricity Grid, Use & Solar

Modify this for Noosa

 

Figure 1 shows the Australian  Renewable  Energy Mapping Infrastructure  (AREMI) map of East Gippsland. It can be seen that there is a 66kV line connecting Bairnsdale Power Station to both Bairnsdale and to the Morwell Zone Substation (ZS). The Bairnsdale Power Station is a 94
MW Open Cycle Gas Turbine owned by Alinta Energy.

To the north-west are the Clover transmission ZS (at the Clover Power Station) and Mount Beauty transmission ZS, shown as the orange dots at the top left of Figure 1. The black nearby dots are the 300 MW Bogong/Mckay and 31 MW West Kiewa hydro power stations, both owned by AGL Hydro Partnership. However, there are no connecting lines to East Gippsland from these ZS or power stations. Figure 2 shows AusNet’s high voltage lines in East Gippsland as of 2012. It clearly illustrates the ‘end-of-grid’ communities that are at the very end of long lines.

Energex Noosa Zone Sub map.png

Information  on current and predicted  network capacity  constraints  is available  in AusNet’s Distribution Annual Planning Report (DAPR).1 In addition to the Bairnsdale Power Station, there are  two  ZSs  in  East  Gippsland:  Newmerella  and  Cann  River.  These  are  connected  to  the Bairnsdale Power Station by a single radial 66kV line.

For Bairnsdale, the DAPR states “The Bairnsdale zone substation (BDL) has no energy at risk during both the summer and winter periods. AusNet Services completed a station rebuild and asset replacement project at BDL in 2015/16, improving supply reliability for 22,300 customers.”

For Newmerella, the DAPR states “The Newmerella zone substation (NLA) has energy at risk during the winter period only over the five-year forward planning period. The load at risk reaches
0.8 MVA in winter 2017 and remains until 2021. This relatively low level of energy at risk is able to be covered by load transfers of 3.2 MVA away from NLA to the neighbouring  Bairnsdale zone substation.  Therefore  no  augmentation  is  expected  in  the  five-year  forward  planning  period” (p57). The DAPR also states that the energy at risk is only 5.4 MWh in 2016 then decreases
every year, declining to 1 MWh in 2021.


1 Distribution Annual Planning Report 2017 – 2021, (AusNet, Dec 2016) available from:  www.ausnetservices.com.au 

In the ‘Technical Background Study’ by FG Advisory, the Cann River ZS is said to have a
3MVA capacity shortfall, which could limit the uptake of renewable energy. However, this is not really the case. The Cann River ZS has a rating of 10MVA  and the forecast  demand  is only
3.0MVA.  In  the  DAPR  it  is  said  to  have  a  firm  capacity  of  zero  because  it  has  only  one transformer, so if this fails, there is no reserve capacity. Firm capacity is determined under the n-1 principle, which assumes that one unit fails. Newmeralla has two transformers and so conforms to the n-1 principle. Thus, this zero firm capacity for Cann River ZS is not relevant to the uptake of renewable energy as it doesn’t restrict uptake nor can it be fixed by it. It can only be fixed by the addition of another transformer, which AusNet considers unnecessary. AusNet have stated that: “There are no forecast capacity constraints in the East Gippsland area”.2


2.1.  Restrictions placed on renewable energy

The network  operator,  AusNet,  can place restrictions  on the amount  of renewable  energy connected to their network because of the potential for technical impacts. The electricity network has been designed for a one-way flow of electricity (mainly from large centralised power stations to the various customers such as households and businesses), not the connection of renewable energy  generation  systems  to the distribution  network.  When  there  is a significant  amount  of electricity exported to the grid from distributed generation, this can result in voltage rise (which can send the voltage outside allowable limits) and can even reverse the flow of electricity back up the network.  This  is already  occurring  in both  Paynesville  and  Metung,  however  AusNet  can currently  allow  for  this  remotely  or  automatically  using  voltage  regulators  and  automatic  tap changers. In addition, if a significant amount of the renewable energy systems are solar PV, their power output can fluctuate rapidly depending on cloud cover, and so the load as seen by the grid can fluctuate just as rapidly. Another problem that can occur on smaller weaker grids is when the frequency of the network fluctuates outside allowable limits. This can be caused by large loads coming online, which can in turn trip off the solar PV inverters  because  they are designed  to disconnect  when  this  occurs.  This  can  make  the  problem  worse  because  this  loss  of  PV generation drops the frequency even more. However, this is solved by broadening the frequency range through which solar PV inverters stay connected, and is not a problem in East Gippsland anyway, since it is connected to the wider Victorian grid.

To pre-emptively minimise such impacts, AusNet currently limits the total inverter capacity for a single-phase connection (ie. a normal household) to 5 kW. For a three phase connection, which generally occurs on businesses with larger loads, the limit is 15 kW. Note that this limit includes any  battery  inverter  that  is  also  connected.  In  most  cases  a  single  inverter  (called  a  hybrid inverter) will be used for both the PV and the battery system. However, some batteries (such as Tesla and the SMA Sunny Boy Storage, which are AC coupled inverters), have their own inverter, and the capacity of both this inverter and the PV inverter will be taken into consideration.
The current situation could be improved by the 5 kW limit being placed on the amount of export to the grid, not the total inverter capacity. All modern inverters can be configured in this

2 Personal communication  from Tom Langstaff (AusNet) 

household could install an 8 kW PV system, which would mostly generate a maximum of 6 to 7 kW, and if their load was 2 kW, only 4 to 5 kW would be exported. If their load was less, then the export  would  automatically  be  capped  at  5  kW.  This  would  mean  larger  systems  could  be installed while still allowing AusNet to control the power going back into the network.

At much higher levels of uptake than are likely to occur in East Gippsland in the foreseeable future, other network operators have either restricted PV systems to zero export to the grid, or have required batteries that can be used to smooth out fluctuations in power output. However, AusNet have no plans to change their current approach.


2.2.  Electricity Use

The current electricity use in East Gippsland was determined using 2016 half hourly demand data provided by AusNet Services from the Bairnsdale (BDL), Newmerella (NLA) and Cann River (CNR) ZSs that service East Gippsland.  The total annual load through these substations  was approximately  265,000  MWh,3 and the annual  demand  profile  is shown  in Figure  3. The blue corresponds to Bairnsdale ZS, the green to Cann River ZS, and the orange to Newmerella ZS. It
can be seen that the highest peaks generally occur in winter, and that most electricity use occurs in winter. It is not clear what has created the very high spikes, and they may be a data error. The periods where the load drops to zero are data errors.
 

Tewantin Zone Sub monthly 2016 2017.png

3 This is an estimate because of gaps in the data provided by AusNet. 

There  are  about  19,160  households  in  East  Gippsland  Shire,4 and  the  average  Victorian household uses 4,026 kWh of grid electricity per year.5 Thus, households make up about 29% of the electricity demand in East Gippsland, with the remainder used by business and industry.

The existing distributed generation (DG) reduces the amount of electricity drawn through the ZSs. Thus, to obtain the real underlying electricity use in East Gippsland, this DG electricity must be added back to the apparent electricity use as seen by the ZSs. This is explained in detail in the following section.


2.3.  Existing Distributed Generation

Solar PV is by far the most prevalent form of distributed generation in East Gippsland Shire. It reduces  the  amount  of  grid  electricity  used  (by  reducing  the  amount  of  electricity  that  is transmitted through the ZSs above). Therefore, to obtain the actual underlying electricity demand for  the  modelling,  each  half  hourly  period  of  electricity  use  was  increased  by  the  estimated amount of PV generation.

According to the Australian PV Institute Solar Map6 there is currently 16,041 kW PV installed in East Gippsland Shire.7 This consists of 4,573 systems (14,489 kW) that are less than 10 kW in size (generally assumed to be residential systems), and 79 (1,551 kW) in the 10 kW to 100 kW size range  (generally  assumed  to be commercial  systems,  which  would  mean  about  1.8%  of businesses have solar PV, with an average size of ~20 kW). Although there are about 24,440 dwellings in East Gippsland Shire, only about 21,310 of these are considered to have suitable roof space for PV and SWHs.8 Thus, with 4,573 PV systems in the sub 10 kW size range, about
21.4% of suitable dwellings have PV, and the average residential system size is about 3.2 kW.

Electricity   generation   by  distributed   PV  was  calculated   by  taking  the  average  hourly generation of typical rooftop PV systems within 100 km of East Gippsland Shire.9 This was then scaled according to the number and size of PV systems 10 to produce an estimate of the hourly generation  over a year. The same  approach  was used for future  installations  of PV for each Scenario,  both behind the meter (household  and businesses)  as well as in front of the meter
(ground-mounted large-scale PV).11

4 2016 Census, ABS.
5 AEMC (2016) ‘2016 Residential Electricity Price Trends’, Australian Energy Market Commission, Dec 2016.
6 http://pv-map.apvi.org.au/historical#8/-37.305/148.260
7 As at April 2017
8 Derived from the 2011 Census, and the APVI Solar Map.
9 PV data was sourced from publicly available PV performance database,  PVOutput.org. This large area was used in order to obtain a representative sample, as not all PV systems are on the  PVOutput.org database. The average system generated 1,152kWh/kWp,  which is very close to the Clean Energy Regulator zone rating of 1,185 kWh/kWp.
10 From  http://pv-map.apvi.org.au.
11 Ground-mounted  systems generally have better orientation and so higher generation, and so a subset of optimally oriented PV systems was used to calculate the ground-mount output. 

Thus, these PV systems generated an estimated 18,500 MWh of electricity in 2016 (or 7% of total demand),  and so the real underlying  electricity  used in East Gippsland  Shire was about
283,500 MWh. To illustrate the impact of PV on the daily load as seen by the substations, Figure
4 and Figure 5 show an average week in summer and winter respectively showing the load as seen by the substations (Net load, orange) and what the load would have been if it hadn’t been for the existing PV systems (Load, blue). The highest peaks in summer are most likely due to air conditioning load, and are slightly reduced by solar. The equally spaced daily spikes are when the off-peak load is activated, and in winter are even higher than the summer maximum peaks, and of
course are not reduced by solar (because they occur soon after midnight).12  Although there is
also likely to be some small-scale wind turbines and micro-hydro, they were not included in the baseline adjustment because they would have a negligible effect.

The current renewable energy percentage under the Federal Large-scale Renewable Energy Target for Australia is 14.22%. Thus, when the electricity generated by local solar PV is included, East Gippsland Shire has a higher percentage,  with just under 20% of the electricity  currently used being renewable.