Radical new way to heat Rotorua homes

A Rotorua motellier may have come up with a sustainable geothermal heating system that could benefit the whole city.
Tapping into geothermal energy without depleting the natural resource is the aim of a heating trial at Rotorua's Alpin Motel and Spa.
If it's successful, owners Steve and Gillian Osborne say it could revolutionise heating in Rotorua and in other geothermally active areas like Taupo and Kawerau.
"It could open up other opportunities for most Rotorua residents," Mr Osborne said.
Environment Bay of Plenty agrees the system has the potential to be more widely used although it can't be sure until the results of the trial are in.
The Osbornes' 40-room Alpin Motel is in Sala St and within 1.5km of Whakarewarewa village so cannot be heated with geothermal energy from a traditional bore.
Mr Osborne recognised the potential to tap into the underground heat sources without affecting the village or the geothermal attractions using a heat exchange system.
He approached Environment Bay of Plenty leading to a two-year trial, which is at its halfway point.
The process involves pushing cold water into underground pipes where it absorbs heat.
It is then pumped back above ground level for use in radiators, spa pools and the motel's hot water.
"We do not extract the water, just the energy," Mr Osborne explained.
"It is just such a logical process and we are in a good place to see what effect it will have."
Heat exchange systems are not new in Rotorua but the materials and design being tested at the Alpin Motel should make the process more efficient.
The trial is being monitored by the National Institute of Water & Atmospheric Research to measure any impact on the area's geothermal features.
"There have been no negative effects recorded so far and results suggest a lot more of the energy could be used.
"It is about 80 per cent efficient but with a bit more science and practical advice I think we could improve on that."
But Mr Osborne said any further development of the idea would require some outside investment and the co-operation of local authorities.
"Everybody we have spoken to is interested but it needs some leadership."
The heat exchange trial is part of a wider environmental focus for the Osbornes that earned Alpin Motel a silver environmental rating from Qualmark - the first of its kind to be issued.
Environment Bay of Plenty will be keeping a close eye on the trial and any potential developments that might be worth exploring.
Senior environmental scientist Dougall Gordon told The Daily Post it was too early to predict the broader benefits of the idea but it did have potential.
"There is a possibility of using this particular design for commercial and domestic hot water and space heating but we can't be sure of this until we have all the results."
Mr Gordon said unplanned use of the geothermal field in the past meant water pressures dropped leading to a decline in the Whakarewarewa geysers and the closing of bores within a 1.5km radius.
"The challenge is to get the most efficient use of heat and energy from the field while sustaining the geysers and surface feature activity.
"It is about finding an appropriate and sustainable balance."