Health New Zealand Te Whatu Ora infrastructure lead Blake Lepper confirmed it was ditching a plan to have heat pump infrastructure in a Bow Lane building and instead use Pioneer Energy’s District Energy Scheme, which heats the existing hospital using woodchips.
However, internal briefings seen by the Otago Daily Times showed concerns were raised that while using the energy scheme could lead to significant savings up front, it could be more expensive to run than the Bow Lane option.
The three-storey Bow Lane building received consents in June last year through a fast-track process.
At the time, the consent documents said it was "ancillary to the main hospital buildings" but would have a "critical" role in the operation of the hospital.
Mr Lepper said Pioneer Energy had recently transitioned from using coal-fired boilers to biomass fuel in the existing Dunedin Hospital.
"We are continuing to work through commercial negotiations with Pioneer Energy to finalise details for the new Dunedin hospital, and as such, are unable to comment further."
"We don’t carefully model buildings and so we often don’t design them in the correct way.
"This leads to all sorts of problems like requiring a lot of heating in winter, overheating in summer from too much solar gain, and then requiring cooling.
"These things arise if you’re not focused on energy efficiency. So to me that should be the place of first effort."
Dr Jack said both heating options had their advantages and disadvantages.
"They’re both kind of sustainable in their own way, but they also have elements that aren’t sustainable about them.
"Heat pumps can have refrigerants that have a high greenhouse gas emission themselves, and biomass can have its own emissions if you’re not replanting the trees."
Health and Air Pollution in New Zealand study lead author Gerda Kuschel said from a "like for like" perspective, heat pumps were more efficient.
"If you are in an urban environment and you are using a heat pump, you’re essentially producing no emissions in that urban environment.
"The bottom line is wood chips would always be producing more pollution than a heat pump in that scenario."
However, Dr Kuschel said other factors, such as sourcing energy, could come into play.
"When we had big snow storms in Canterbury, people who had heat pumps were really freezing for about a week because the electricity lines went down and they didn’t have a wood burner."
The government has said it would build the new Dunedin hospital for $1.88 billion.
