Solar water heating no magic bullet - study
Solar water heating is not the "magic bullet" that will save the environment and help New Zealand meet its renewable energy targets.
That is the conclusion of Parliamentary Commissioner for the Environment Jan Wright in this morning's report to Parliament on renewable energy.
Wright is also questioning the wisdom of the Christchurch City Council's energy strategy encouraging and subsidising solar water heating.
She said the desire of successive governments to generate 90 per cent of the country's electricity from renewable sources by 2025 was doomed to fail unless greater efforts were made to reduce winter demand peaks.
Solar water heating was of little use in achieving that aim as the Sun was at its weakest in winter.
While electricity demand continued to peak in winter, new power plants would have to be built to provide that extra electricity, "locking in" a new source of carbon dioxide for decades.
Instead, more widespread promotion of night-only water heating, when demand for electricity was low, would flatten peaks and deliver significant environmental benefits, she said.
Hot water heating accounts for about 40 per cent of the average power bill. Nearly 12 per cent of all electricity generated is used for heating water.
Wright cautioned against the widespread adoption of solar water heating in the Christchurch rebuild, referring to the 2200-home Highfield subdivision and developers' plans to install solar water-heating systems and photovoltaic panels on roofs.
"In Christchurch there is an intent strongly endorsed by the community to take the opportunity to build a greener city, an intent that is both sensible and laudable," Wright said.
"Councils that are subsidising solar water heaters for environmental reasons should consider whether other assistance would yield greater environmental benefits at a lesser cost. This is especially important in Christchurch."
Wright gave the Energy Efficiency and Conservation Authority a serve for its water-heating advice, which needed to be "reassessed and updated".
The authority also needed to provide better information on energy efficiency and renewable options to consumers and councils.
The report had "taken on a life of its own", starting as a critique of solar water heating and ending up considering the entire electricity sector, she said.
Using sunlight to heat water was an idea with "great appeal".
"But in this country, making electricity use more consistent over time is the key to achieving the 90 per cent renewable electricity target and reducing the impact of electricity on the environment," Wright said.
"There's no magic bullet here - solar water heating doesn't help as much as we assumed it did.
"This is very much because in New Zealand we have a winter power peak, unlike Australia or Israel or California. On the very days when the peak is at its highest, solar is at its weakest.
"I'm not slamming solar water heating - I'm saying there are better things for a low-carbon future for New Zealand."
- © Fairfax NZ News
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