Harnessing the power of the sun

Community irrigation scheme success in using solar power for augmentation and pumping water

Assisting stream health and electricity use through solar power has been supported by a small solar project by the Eiffelton Community Group Irrigation Scheme (ECGIS).

ECGIS is a small owner-operated irrigation scheme located near the Ashburton coast of Canterbury. It was established in the mid 1980s, has 13 members, and covers 2,200 hectares.

The scheme’s system involves pumping water from multiple groundwater bores into lowland waterways for irrigation purposes. During the irrigation season the lowland streams are supported by the water that is present. This, in turn, supports operational, fish habitat, and passage improvements. However, when the scheme is not running (e.g. winter months) there is not always excess water available. For many years ECGIS has voluntarily augmented the waterways through targeted stream augmentation (TSA), and sought to alleviate some of the energy costs involved with this.

The idea to use solar power came about in early 2020. Solar are a good source of renewable energy for irrigation and many environmental projects because of the correlation between solar radiance and evapotranspiration. With funding support from the Ministry for Primary Industries’ Sustainable Food and Fibre Futures fund, Environment Canterbury, and scheme members, the project began in spring 2020. By May 2021 the solar panels were completed, with a total of 160

panels covering 400 square metres commissioned at a total cost of $120,000. The system has been in use since then.

Frizzell Agricultural Electronics owner, Alastair Frizzell, was involved with developing this project. He said the installed capacity of the system is a 45 kilowatt (kW) solar array connected to a 50kW groundwater pump and the electricity grid.

Rick Bourke (left) and Alastair Frizzell have been heavily involved with the development of the project.

Alastair said that by comparison, most house solar installations consist of about 12 panels, typically with a maximum output of 5kW of energy. This is about one-tenth of the size of the Eiffelton system.

Over the course of the 2021–2022 season the system produced around 60,000 kilowatts of energy. The system is configured so that energy production is maximised in summer, when demand is greatest for irrigation. While the configuration means there is some loss of energy over the winter period, the electricity is only used to support TSA.

When the energy from the solar array exceeds what is needed for the pump, the excess is fed back into the grid to give the scheme a credit. Alastair said that to maximise returns it is important to configure the solar energy system so that the maximum amount of energy is used on site, and as little as possible is traded in to and out of the grid.

The theoretical economic model predicted a net electricity cost of $7,625 over the November to February period for an average year. The actual net cost of electricity over this period for the 2021–2022 year was $1,722, providing an above average year comparison.

The electricity cost less because although the solar panels produced less power than budgeted, the wet season irrigation demand and resulting irrigation pump running time were much lower than in a typical season.

The results showed that solar energy supply for irrigation has big advantages compared to solar installations to provide energy for houses. While houses need energy in the morning and at night and typically have higher demand in winter, demand and solar generation are a much better fit in irrigation systems. “When it is hot and dry the panels have a high output to cope with higher irrigation demand. Solar production drops when it is cloudy and raining, just like irrigation demand.”

Alastair said it suggests there is a positive business case for investing in solar power for all assessed scenarios. For the 2021–2022 season, return on capital was assessed to be close to 20 percent, due to the above average season (including electricity spot prices).

The panels themselves generally have a 30-year life span, and beyond that continue to be productive but at a slightly reduced rate.

Chairman of ECGIS, Rick Bourke, said developing this project was a great outcome for what was a challenge for the scheme.

“As a small scheme, electricity is a big cost. Therefore it was good to find a way to support this that is both environmentally and economically sustainable.”

“Small projects such as these are important for understanding how effective they can be – a proof of concept of the value. As a scheme we would like to look at using solar to offset electricity costs in other areas in the long term, where costs allow.”