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Published: 7 October 2013
Point-of-use electric may outperform gas hot water systems
An RMIT University investigation into the environmental impacts of hot water systems has revealed the need for greater flexibility in Australian building policies to support innovation in future-proof technologies.
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In some situations, gas and solar-boosted gas hot water systems may not perform as well as new point-of-use electric systems. Credit:
Gordan1/istock
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Researchers from RMIT's Centre for Design have for the first time compared the impact across the life cycle of a gas centralised hot water system with a point-of-use instant electric system in medium and high-density apartment buildings.
Alan Pears AM, Senior Lecturer in Environment and Planning at RMIT, said the results of the comprehensive life cycle assessment showed current policies favouring gas and gas-solar hot water systems were short sighted, reflecting the lack of a whole-system approach to measuring environmental impact.
‘Our findings show there are significant opportunities today, and in coming years, for point-of-use electric systems to perform better than gas and solar-boosted gas, in greenhouse gas emissions and energy demand,’ he said.
‘Context is the key to choosing environmentally-friendlier hot water systems and this research demonstrates why policymakers should consider a systems approach in regulation, rather than following product-specific rules-of-thumb.
‘Because of their strong energy efficiency, point-of-use electric hot water systems could also be the choice to ensure future-proofing of developments, as future grid emission reductions combine with efficiency for strong environmental outcomes.’
The independent research, which assessed greenhouse gas emissions, water use, solid waste and cumulative energy demand and included the use of dynamic thermal modelling software, was commissioned by Australian-owned MicroHeat Technologies, developers of the electric hot water system – which uses a ‘direct energy transfer’ method rather than heat exchange – examined in the study.
Testing the point-of-use electric product and comparing the two systems over the life cycle in a 257-apartment building and an 8-apartment block, the study found:
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in operation, point-of-use was up to 3.1 times more energy efficient than gas in the medium-density block (up to 1.6 times compared with solar-boosted gas)
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in operation, point-of-use electric was up to 2.3 times more energy efficient than gas in the high-density building
While the study found gas currently scored better on greenhouse gas emissions in coal-reliant Victoria over the life cycle, the electric system could perform better with green power now and in coming decades (with more grid renewable energy).
Translating the findings to warmer states that have more green power feeding into their grids showed that the point-of-use system already performs better for average hot water use and on greenhouse gas emissions in the smaller building.
Source: RMIT
