3. MODELLING RENEWABLE ENERGY RESOURCES AND TECHNOLOGY OPTIONS
Together with ITP Renewables, Zero Emissions Noosa has developed two scenarios for 2026. These scenarios are firstly summarised below, then are described in more detail. Note that scenarios are not predictions: they are simply used to illustrate the impact of different levels of electricity demand and electricity generation options.
Scenario 1 Base Case:
This is intended to result in a greater amount of large-scale PV being needed to reach 100% renewable electricity – largely because it has a relatively modest uptake of ‘behind the meter’ renewable energy and energy efficiency options, which are based on the continuation of BAU levels of uptake. Household PV increases from 26.1MW to 48.1 MW, while commercial PV increases from 2.7 MW to 30.7 MW. Solar water heaters/heat pumps increase from being on 17.1% of houses to being on 26.4%. This scenario assumes no additional bioenergy, wind or hydro. The population increases by 12%, 10% of vehicles are assumed to be EVs and there is only a 5% reduction in average per capita electricity use because of energy efficiency. As a result, 105 MW of large-scale ground-mounted PV is required to achieve the 100% renewable target. A quarter of households and businesses that install PV are assumed to have batteries, but the main impact of this is to help smooth the load profile by reducing evening peaks.
Scenario 2 Stretch:
Is intended to result in a smaller amount of large-scale PV being required to reach 100% renewable electricity. It represents a realistic but ambitious level of uptake of renewable energy and energy efficiency in the general community. Total residential and commercial PV increase to 80.5 MW and 43.1 MW respectively, and SWHs/heat pumps are on 50% of houses, however only 0.1MW of bioenergy is installed. Population growth is lower (9%) and energy efficiency reduces average per capita electricity use by 17%. However, in keeping with the community’s increased interest in behind-the-meter PV and energy efficiency, there is also increased interest in EVs (20% of vehicles), which offsets the effects of lower population growth and increased energy efficiency. In this case, 59 MW of large-scale PV is required. Of households and businesses that install PV, 40% take up batteries, which smoothes the load profile more than in Scenario 1.
2.1. Modelling 2026 Electricity Use
The modelling was performed for the year 2026 using NEMO (National Electricity Market Optimiser), an open source electricity sector model (https://nemo.ozlabs.org). It was used to model the hour-by-hour dispatch of a range of electricity generation technologies according to the scenarios described below. Only technologies that are commercially available in Australia are used.
This firstly involved projecting electricity use from 2016/17 allowing for population growth, uptake of SWHs, and the uptake of energy efficiency options in general. Different levels of uptake of distributed smaller-scale PV, large-scale PV, wind, bioenergy and GreenPower purchase were then programmed into the model according to the following scenarios. It was assumed that electricity could be drawn from the National Electricity Market (NEM) when required (most likely overnight), then exported to the NEM when in excess (most likely during the day).
2.1.1. Population Growth
According to the ABS Census for 2016 the population of Noosa LGA was 52,149. To this must be added the estimated 13,425 overnight visitors,(13) giving a total of 65,574, rounded here to 65,500. We assume population growth of 12% (73,360 for Base case) and 9% (71,395 for Stretch).(14) We assume that the number of dwellings suitable for PV and SWHs increases by the same percentages, resulting in 26,050 (Base case) and 25,350 (Stretch).
2.1.2. Smaller-scale Technology Uptake
The following discusses the various options that can affect electricity use. They can be divided into those that (i) decrease electricity use (energy efficiency, including solar water heaters and air-sourced heat pumps, behaviour change), (ii) increase electricity use (electric vehicles), (iii) generate renewable electricity (PV, wind turbines, bioenergy), and (iv) GreenPower.
Decreasing Electricity Use
Decreasing electricity use through energy efficiency measures (also known as negawatts) is generally by far the cheapest way to reduce the amount of electricity drawn from the grid, and therefore greenhouse gas emissions. Load management is similar, but includes simply shifting loads from one time to another, without necessarily decreasing electricity use (some load shifting measures may in fact increase energy consumption).
They can provide value by (i) reducing the annual need for electricity, which makes meeting renewable energy targets easier, (ii) reducing demand at peak times, which reduces the amount of local renewable energy and network capacity needed at any one time, and (iii) reducing demand at times of low local renewable energy generation, which would reduce the amount of electricity that needs to be imported into Noosa LGA (for example, where large amounts of solar PV is used to meet electricity demand, overnight loads, such as off peak water heaters, should be moved to day time boosting).
- Solar water heaters and air-sourced heat pumps
Information is available on the number of SWHs and air-sourced heat pumps by postcode from the Clean Energy Regulator. Noosa LGA includes the postcodes 4562, 4563, 4565, 4566, 4567, 4568, 4569, 4571, and 4573. Of these, postcodes 4562, 4563 and 4573 include a proportion outside Noosa LGA. The Australian Bureau of Statistics provides Australian Statistical Geographic Standard Correspondences that are a mathematical method used to assign data from one geographic region to another.(15) We have used these to assign the SWH uptake from these postcodes to Noosa LGA. Thus, about 13% of suitable dwellings have SWHs, and about 4% of dwellings use air-sourced heat pumps for heating water. For Scenario 1 we assume that the uptake occurs at the same rate as the last two years (4.3% per year for SWHs and 6.8% per year for heat pumps). For Scenario 2 we assume 10% per year for SWHs and 20% per year for heat pumps.
The amount by which SWHs reduce electricity use can vary greatly (eg. from 20% to 90%) (16) depending on the orientation of the system, the amount of shading, the efficiency of the system, the design of the system (eg. flat plate or evacuated tube), the climate, the hot water demand, the boosting type and the time of day that hot water is used. Some of these issues do not affect heat pumps, for example, they are unaffected by orientation or shading and their efficiency is generally unaffected by hot water demand. SWHs and air-sourced heat pumps are often assumed to, on average, reduce the electricity used for the average hot water system by 70%(17) and a study of residential water heaters in Brisbane reported an average reduction from 7.95kWh/day to 2.74kWh/day (66%).(18) Thus, for the modelling conducted here, we have assumed that the average SWH or heat pump reduces electricity use by 5.2 kWh/day on average through the year. We apply this reduction between 10pm and 7am.(19) The SWHs and heat pumps currently installed in Noosa LGA avoid the use of about 7,550 MWh of electricity per year (meaning that, without them, electricity use would be about 2.1% higher).
SWHs and heat pumps offset the use of off-peak electricity, which costs less than standard electricity, which means they have a longer payback time than PV systems. We don’t distinguish between SWHs and heat pumps because we have no data on the likely future split in uptake and it is likely they will have similar impacts on electricity use. Table I shows the estimated uptake of residential SWHs and heat pumps taking into consideration the projected population growth.
- Other energy efficiency options
There is a wide variety of energy efficiency options available for households as well as businesses. Behaviour change (such as turning off lights, wearing warmer (or cooler) clothing, turning down thermostats etc) is also a very significant contributor to energy efficiency outcomes.(20) The uptake of these options has been modelled as a general reduction in load between 7am and 10pm.
In order to create each Scenario we assume that these other energy efficiency options reduce Noosa LGA’s electricity use in 2026 by the amounts shown in Table II. Then, when combined with the impact of population growth and residential SWHs/heat pumps, the final outcome are changes of 5.75% to -13.4% with respect to 2016/17 levels. Note that SWHs/heat pumps are assumed to decrease electricity use only between 10pm and 7am, and general energy efficiency is assumed to decrease electricity use only between 7am and 10pm.
Increasing electricity use
- Electric Vehicles
Although any new appliances and other technologies can increase electricity use, the main potential influence in Noosa LGA is electric vehicles (EVs). According to the 2016 Census, there are on average 1.8 vehicles per occupied dwelling in Noosa LGA, and with 20,142 such dwellings, there are about 36,250 cars. According to the ABS, the average passenger vehicle in Australia travels about 13,700 km/year(21). According to Ergon Energy, the average EV requires about 18kWh to travel 100km(22). Zero Emissions Noosa are interested in driving increased uptake of EVs, and assume 10% and 20% of total passenger vehicles for the Base case and Stretch scenarios respectively. Given the approximate nature and wide range of these values, we have not increased them to allow for population growth. Using these values, the assumptions and outcomes for each Scenario have been calculated and are shown in Table III.
- Distributed Solar PV
As discussed above, there is currently about 28,909 kW PV installed in Noosa LGA: consisting of 8,031 systems (26,064 kW) that are less than 10 kW in size, and 145 (2,845 kW) in the 10 kW to 100 kW size range. About 35% of suitable dwellings have PV, as do 4.7% of businesses.
The assumptions and outcomes for each Scenario are shown in Table IV. Scenario 1 results in 54% of suitable households and 50% of businesses having PV. Scenario 2 results in 75% and 71% respectively. In reality there will of course be a range in system sizes, with some installations being less or more than the assumed average.
Very little bioenergy is assumed to be installed in Noosa LGA by 2026 – only 0.5MW in Scenario 2. Its electricity generation was estimated by dispatching the full capacity of the biomass plant in each hour of the year. The assumptions and outcomes for each Scenario are shown in Table V.
GreenPower is accredited and independently audited electricity that is certified to come from renewable energy generation. It is additional to any mandated renewable energy targets, and so is bought by electricity customers so they can make their own contribution to increasing the amount of renewable electricity and so reducing greenhouse gas emissions. It generally costs about an extra 5c/kWh, and so for a household using say 11kWh/day (~4 MWh/year), would add about $50 to their quarterly electricity bill. Currently only about 0.35% of Queensland electricity sales are through GreenPower. The assumed purchases of GreenPower for each Scenario are shown in Table IV.
As discussed above, the modelling started with 2016/17 electricity use, then allowed for population growth, uptake of SWHs, energy efficiency and EVs – which all affect the final amount of electricity that needs to be supplied. Different levels of uptake of distributed PV, bioenergy and GreenPower purchase were programmed into the model, which then calculated the amount of large-scale ground-mounted PV required to meet the remaining demand over the year. The amounts of wind power and hydro were assumed to be negligible.
Their combined impact of all the above options (excluding large-scale PV) is shown in Table VII. It can be seen that by 2026, the scenarios have total electricity use ranging from an increase of 5.75% to a decrease of 13.4% compared to 2016/17 2015. The combined effect of distributed PV, wind, bioenergy and GreenPower purchase results in significant amounts of large-scale ground-mounted PV needed to meet demand over the year: 105 MW (Scenario 1) and 61 MW (Scenario 2), producing the amounts of electricity shown in Table VIII.
2.1.3. Final Renewable Energy Mix
Table IX shows the final capacity of each type of generator in 2026.
The following charts (Figure 4 to Figure 7) show the electricity generation from the mix of renewable energy technologies in each Scenario in Noosa LGA in 2026. For each Scenario, a summer peak week and a winter peak week are shown. Each of the colours represents a different technology (or category of technology such as residential or commercial PV). The slightly thicker black line shows the level of demand, and where generated electricity is exported, a paler version of the technology’s colour is used. The brown areas represent electricity imported from the Qld grid.
In all cases it can be seen that there is a significant amount of excess solar PV electricity that flows back up through the ZSs. In the Base Case Scenario, which has less behind the meter PV, the excess is generated by the ground mount PV. In the Stretch Scenario the behind the meter PV is sufficient to cause reverse power flow.
We have modelled the impact of some of the households (25% in the Base Case Scenario and 40% in the Stretch Scenario) with PV also installing batteries with a 10kWh capacity (8kWh useable)(23) . These are used to capture PV electricity that is in excess of the household’s needs, which is then discharged from 6pm. The battery generation is shown in grey, and makes a much more significant contribution in the Stretch Scenario. The use of batteries in this way reduces the reverse power flow of PV electricity. Of course, load shifting through demand management, such as moving off peak water heating to the middle of the day, would also be very effective.
(13) Provided by Zero Emissions Noosa based on Tourism Noosa data.
(14) Based of feedback from Zero Emissions Noosa.
(15) These can be obtained from http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/1270.0.55.006July%202011?OpenDocument
(16) Gill, N., Osman, P., Head, L., Voyer, M., Harada, T., Waitt, G. and Gibson, C., 2015, ‘Looking beyond installation: Why households struggle to make the most of solar hot water systems’, Energy Policy, 87, p83-94.
(18) Vieira A.S., Beal, C.D. and Stewart, R.A. (2014) ‘Residential water heaters in Brisbane, Australia: thinking beyond technology selection to enhance energy efficiency and level of service’, Energy & Buildings, 82, 222-236.
(19) SWHs and heat pumps would be much more effective in reducing electricity use during summer than in winter, and not all electric water heaters operate only between 10pm and 7am, however given the other estimates used here (such as uptake of these technologies), these assumptions are reasonable.
(20) Strictly speaking, behaviour change is an energy conservation measure, not an energy efficiency measure.
(23) Assumes 80% useable capacity.