Rooftop Solar In The Northern Territory
Not only is there plenty of sunshine in the Northern Territory, but you’ll also receive what’s called a feed-in tariff.
Feed-in Tariff
New systems installed in the NT up to 30kW capacity are eligible for a feed-in tariff of 8.3c per kilowatt-hour for surplus electricity exported to the grid.
The Northern Territory’s PowerWater Corporation
Electricity, water, and sewage disposal services in the Northern Territory are provided by the Territory Government owned corporation, PowerWater. It is run by very talented people who never confuse the two, so taking a shower in Darwin is not a shocking experience.
Solar System Size In The Northern Territory
The PowerWater Corporation states that the maximum sized solar power system that can be installed on a normal residential dwelling is a 4.5 kilowatt array for single phase power, or a 6 kilowatt array for homes with 3 phase power. Most homes in the NT have single phase power, but 3 phase power is becoming more common, particularly for large homes with heavy air conditioner use.
The maximum size of residential solar systems is limited by the total capacity of their solar panels, rather than the size of their inverters. It is possible to install larger systems, but PowerWater says that can only be done after, ‘undertaking extensive investigations’, so I am not optimistic about people’s chances of being allowed to install larger systems.
The Solar PV Fee
A solar PV fee needs to be paid when the application document for rooftop solar is submitted to PowerWater. For residential installations, as of July 1st 2015, the fee is $546.08 for single phase meters and $750.04 for three phase meters. It covers installing a new import/export electricity meter and any other costs PowerWater may incur.
Your installer should be able to assist you with the application process.
Insolation
There is plenty of sunshine in the Northern Territory. One square meter of a typical north facing roof in Darwin will receive an average of around 6.3 kilowatt hours of sunlight energy a day.
Darwin is Australia’s second second sunniest capital after Perth, as measured by average hours of sunshine, and its northerly location makes the sunshine it receives particularly intense. Despite Perth having more hours of sunshine, and a lower average temperature which improves the efficiency of solar panels, an optimally aligned panel will produce around 5% more electricity a year in Darwin.
Electricity Use In Darwin
A 3 person household in Darwin that doesn’t use gas consumes an average of 6,750 kilowatt-hours a year and uses 51% more electricity in summer than winter. . At the standard tariff of 25.54 cents a kilowatt-hour and with the 50 cent daily supply charge, that will cost a household without solar panels around $1,910.
Electricity Production and Savings From Rooftop Solar
In Darwin you will get more solar electricity in winter than summer. Here is a graph that shows how many kWh of electricity you can expect to generate per kW of solar installed through the year
A 4.5 kilowatt, north facing, rooftop solar system installed in Darwin can be expected to produce an average of around 22 kilowatt-hours a day, or around 7,800 a year. This will save the household around $2,000 a year.
A 6 kilowatt system will produce an average of around 29 kilowatt-hours a day or 10,600 a year. This will save the household around $2,700 a year
The generous feed-in tariff in the Northern Territory means that many households with systems of these sizes will either pay nothing on their electricity bills or receive a credit, particularly during winter months.
Solar Panel Orientation In The Northern Territory
Because of the Northern Territory’s high feed-in tariff, the most economically efficient location for solar panels is on a north facing roof which will maximise the amount of electricity produced over a year. There is no benefit to your wallet by positioning panels to maximise your self consumption of solar electricity.
Because Darwin has a lot of cloud cover during the rainy season in summer and because even a gently sloping north facing roof is too steep to maximise the output of solar panels at that time, north facing solar panels will produce around 41% more electricity in winter than summer.
If facing panels north is not possible then the next best option is to place them east, west, or even south. In the more temperate parts of Australia there are people who consider south facing panels almost as large a mistake as placing them upside down. But because Darwin is close to the equator, on a typical roof angle of 15 or 22.5 degrees, south facing panels will produce only about 17% less electricity than north facing ones over a year. And the portion of electricity they produce in summer compared to winter will be increased.
West or east facing panels will produce about 10% less electricity than north facing ones and north-west and north-east panels will produce about 5% less.
Here is a table that shows the effect of different panel angles and directions on the energy yield. For example: north-facing panels 20° from horizontal will give the optimum year-round energy (100%). The energy yields from all other orientations are shown relative to that ‘perfect’ 100%.
| Horizontal | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | Vertical |
|---|
| N | 96% | 99% | 100% | 99% | 94% | 88% | 79% | 69% | 58% | 48% |
| NE | 96% | 98% | 99% | 96% | 93% | 87% | 80% | 72% | 63% | 55% |
| E | 96% | 96% | 95% | 92% | 87% | 82% | 76% | 69% | 62% | 55% |
| SE | 96% | 93% | 89% | 82% | 75% | 67% | 59% | 51% | 44% | 37% |
| S | 96% | 92% | 86% | 78% | 69% | 58% | 48% | 40% | 33% | 27% |
| SW | 96% | 93% | 89% | 83% | 76% | 68% | 60% | 53% | 46% | 40% |
| W | 96% | 96% | 93% | 90% | 85% | 79% | 73% | 67% | 60% | 52% |
| NW | 96% | 98% | 98% | 96% | 92% | 86% | 78% | 70% | 61% | 52% |
Solar Panels And Damp Heat
High temperatures combined with high humidity is hard on electronics and solar panels are no exception. Any panels installed in the muggy climate found in the upper half of the Northern Territory should be a type that has performed well on a damp heat test, which is designed to determine how well solar panels handle tropical environments. While it is not necessary for panels to have an excellent result on this test, the higher the better, and it is very important to avoid panels that perform poorly, as they can rapidly degrade and even fail completely in under a decade. Or much less than a decade in some cases.
Some solar panels that performed well on a recent damp heat test were, CSUN, Jinko, Phono Solar, REC, Recom, Tenksolar, and Trina. Note that if a panel is not on this list does not mean it is not suitable, as it simply may not have included in the test.
Solar Panels And Heat
High temperatures reduce the efficiency of solar panels, and the Northern Territory definitely has high temperatures. Because installations are limited in size by their total panel capacity, it is not possible to compensate for this by adding an extra panel or two, as can be done in some other parts of Australia. So for people who want a maximum sized solar power system, and I do recommend going for the maximum size in the Northern Territory if at all possible, then it can definitely be worthwhile to get panels that handle heat well.
The relevant information to look for is, ‘Max Power Temperature Coefficient’, on a panel’s datasheet which can be found online. It may also be called, ‘Temperature Coefficient of PMAX’ or, ‘Power Temperature Coefficient’. Whatever it is called, the lower this number, the better a panel will perform in high temperatures. A typical value will be -0.4%, but compared to that a panel with a figure of -0.2% it will produce roughly 11% more electricity over a year in Darwin.
Getting The Most Out Of Your Rooftop Solar System
Because the maximum size of residential rooftop solar systems is limited by the total capacity of the solar panels, and there is a generous feed-in tariff, it can definitely pay to spend a little extra to maximise the output of the solar panels. One way to do this is to minimise any shading of the panels that might occur through the day or year. Another way is to use microinverters or solar optimisers which will insure each panel operates at its maximum output and typically increase overall output by 5-15%. They are particularly useful at reducing losses if panels suffer from shading.
Rooftop Solar And Greenhouse Gas Emissions
The Northern Territory has no coal power, so electricity produced from rooftop solar power systems will displace natural gas generation. Burning natural gas does not result in as much greenhouse gas emissions as coal power, and because the NT grid isn’t connected to anywhere that uses coal, rooftop solar power there is likely to cut less greenhouse gas emissions than anywhere else in Australia. But while coal power produces more carbon dioxide than natural gas, it is still very important to cut emissions from gas use and so rooftop solar energy in the Northern Territory is definitely environmentally worthwhile.
The Northern Territory uses mostly combined cycle natural gas generation in winter and supplements it with less efficient open cycle gas generation to meet increased demand in summer. Because south facing panels in Darwin produce more electricity in summer when the less efficient natural gas plants get the most use, they should have the same or greater environmental benefit than north facing panels, despite producing around 17% less electricity over the year.
PowerWater has trouble meeting demand during the summer big wet, and since south facing panels produce more electricity at that time, they will give them more of a hand than north facing panels.
Solar Uptake In The Northern Territory
Despite a massive amount of sunshine sloshing about the place and a generous feed-in tariff, the Northern Territory has the lowest uptake of rooftop solar power in Australia with only about 8.7% of homes having a system. However, the number is expanding rapidly. The slow start compared to the rest of Australia was no doubt largely caused by the fact the northern territory’s now highest in the nation feed-in tariff, was actually lower than what used to be available elsewhere. Also, with its large temporary population of renters, Darwin has the lowest home ownership rate in Australia at 57% and this also would have reduced the number of installations.
