Botanic Garden glasshouses better off without gas

Wellington’s Botanic Garden ki Paekākā is the first plant nursery in Aotearoa to ditch gas heaters and use heated pipes to keep their glasshouses warm.

Row of glasshouses at the botanic gardens.

Previously, the gas heaters in the glasshouses used to blow hot air around at floor level and were often temperamental and unreliable.

They used up to 33,000 kWh of gas per month in the winter – that’s the same amount as 30 average Kiwi homes use in a year, in just one month! As well as being costly, the unpredictable temperatures caused health issues in the plants.

Pipes at the Botanic Gardens under the glasshouse. — The heated pipes run under the work benches.

When it came time to repair the heaters, the gardens team began consulting with different organisations about how they could be more energy efficient and climate-positive. A solution soon came forward to use CO2 heat pumps.

As this type of system was a first to be used for a plant nursery, the team received funding by Energy Efficiency & Conservation Authority (EECA) to install a hot water heat pump, which uses two units to pump water heated to 90 degrees through pipes running underneath work benches and evenly distributing heat.

Pipes at the Botanic Gardens. — New system in place.

A year on from the installation, the results show how beneficial this work has been, says Wellington Gardens Manager David Sole.

“It’s amazing to see that we’ve halved our glasshouse operating costs and had a 64 percent reduction in energy use and a 100 percent reduction in gas consumption.

“We are also seeing an improvement in our plants, with our staff noticing that the leaves aren’t drying out as much now with consistent temperatures.”

Energy Advisor Jess Roberts adds that this work didn’t happen in isolation and there are plans to roll out similar gas reduction and gas removal projects like this out across other facilities in the city.

Old glasshouse at the Botanic Gardens. — Old system used to heat the glasshouses.

“What we’ve achieved at the Botanic Gardens is what we want to do everywhere else. Doing a smaller scale project like this one shows how much we can optimise systems and roll out similar these changes in our facilities.”

Wellington City Council Climate Action Strategy Lead Mike Sammons says this project shows innovation in the move to being net-zero by 2050, as part of Te Atakura – First to Zero, our climate action plan.

“This project shows how we are moving in the right direction, especially when we have low carbon energy solutions at a place that is loved by Wellingtonians for its beautiful plants, trees and flowers.”