Our renewable electric system was judged the best in New Zealand by SEANZ for its ability to meet all the needs of our extensive horticulture operation, support the national grid and make us an additional revenue stream.
Our system architects Craig Browne and Regan Heal (from Infinite Energy) and Mike were on hand to accept the award in Hamilton on Friday, the 2nd of July. Infinite Energy was instrumental in the success of our system, which needed to be designed to power our AGI Electric Frost Fighting Fans, our Orcard Utility Vehicle, our irrigation pump, our tools, and our future electric tractor currently being manufactured by Monarch Tractors out of California.
Because we are early adopters of electrification, we have a substantial reliance on power. How we connect, interact, support and impact the grid were all essential parts of the judging criteria.
Congestion
The national grid suffers from small but significant periods of congestion, when many people and businesses want to use power, but the lines are not big enough to transport all that power to everyone. This can lead to power shortages, low voltage or, in extreme cases, load shedding.
From this point, we have designed a system using a battery array that ensures we pull as little power as possible from the grid during times of congestion, and therefore not add to the load burden. If we have spare power in our batteries, which we are not forecast to require, we also export power back to the grid to ensure our neighbours have enough power when they need it.
Aurora, our utility company, also has congestion charge based on the amount of power used during this congestion period, and this charge is a significant part of a businesses annual line charge. By actively exporting during times of congestion, we can significantly reduce our line charge and cost to our business.
Example of log output during CPD Congestion Period
2021-07-05 08:29:36,241 !!!!!!CPD ACTIVE!!!!!!!!
2021-07-05 08:29:36,868 SPOT PRICE:$0.20037
2021-07-05 08:29:36,884 Exporting to Grid @ -1000 KwH, battery: 71 percent
The judging panel liked that we can support the national grid using our system and contribute renewable power to help NZ achieve a 2030 100% renewable grid.
Arbritrage
We also request the spot price for the Cromwell GXP every minute from the Electricity Authority's API. When the spot price is under $0.15 we know that power is likely to be renewable and abundant. Likewise, when the spot price goes above $0.4, it's likely that coal and gas are being used to supplement supply at that time, and that there is a shortage of power available.
15c and 40c is an arbitrary set of figures, but serve the purpose of defining when we should buy power from the grid and when we should sell it. We run both our export and import of an exponential function, so that we scale up our import and export if the price becomes more advantageous.
Example of log output from low price import
2021-07-05 05:17:16,283 CPD INACTIVE
2021-07-05 05:17:17,101 SPOT PRICE:$0.0848
2021-07-05 05:17:17,116 Importing from Grid @ 28677 KwH, battery: 89 percent
Example of log output from high price export
2021-07-05 11:09:33,693 CPD INACTIVE
2021-07-05 11:09:34,404 SPOT PRICE:$0.40032
2021-07-05 11:09:34,416 Exporting to Grid @ -1741 KwH, battery: 62 percent
We need to cover a 23c spread to break even on arbitrage. This takes into account battery wear and tear, power loss from inverting, and Contact Energy's cut on our export.
Revenue from arbritrage is insignificant, but it is a small offset to the capital cost of our batteries and power consumption. Arbritrage is considerably better in months when we can generate significant power for free using solar.
The judging panel liked our clever use of custom software for arbitrage, even though it would not generate significant revenue. There is the option to generate more revenue in the future as we expand our connection size, battery and solar arrays.
Use of Power
Our Solar Panels are there to bring our average power price down. Because we create our own free power, and use the power supplied by Contact Energy, we can significantly lower the cost per kilowatt of power by using power when we generate it, and then storing any surplus in the battery for consumption / export later on.
Right now, our biggest use of power in the orchard is irrigation via an 18.5 kWh pump, run using a VFD. During summer, we may be irrigating around the clock, and our system is designed to utilise our own production as much as possible. We are also designing the system for our future electric tractor, which will come with two battery packs so that we can charge using the power of the sun.
The judging panel liked how our power consumption is close to what we generate, and that our business only has a small net impact on the grid over a 12-month period.
A Big Thanks
There are numerous people who require a thank you for making this all possible. Jase Lee from Sangsters Electrical is our industrial electrician who wires all our appliances to the system. He has been working strenuously on new monitoring software, so we can report back on our internal consumption and investigate power loss. Dana and Henry from BNZ have made us part of their natural capital portfolio and helped us structure our debt financing to accommodate the upfront capital of electric technology.
Dinesh from EECA, who has submitted two of our demonstration grant applications to the EECA panel for our electric frost fighting fans and our future electric tractor.
Glenn from Aurora, who has been helpful and supportive as we explore how our resources can better support Aurora's network and national grid.
Katie from Simply Energy, who has been a brilliant contributor and supporter. Together, we are designing future retail plans for other customers who wish to become a distributed energy resource.
And finally, thank you to Brendan and his team at SEANZ for recognising what we are trying to achieve and thinking us worthy of the award.