Recently, there has been discussion surrounding the suitability of heat pump technology as a renewable energy water-heating solution. Glenn Day clears the air on heat pump technology.
As Australia embarks on the phase-out of green house-intensive hot water systems, debate continues to rage over the relative benefits of the replacement technologies on offer — instantaneous gas units, gas storage, solar systems and heat pump tech nologies. An apparent shortfall in the understanding of these technologies, along with rampant economic and political speculation, is threatening to impact the uptake of some of these environmentally friendly water-heat ing technologies.
The introduction (and subsequent lowering) of government-funded Renewable Energy Bonus Scheme rebates and the application of the Renewable Energy Certificate (REC) program has also fuelled discussion, with some calling for their overhaul or abolition.
Additionally, misleading reports pairing the Renewable Energy Bonus Scheme with the recent ‘insulation rebate rorting’ scandal have blurred the issue even further.
While all replacement technologies promise to deliver some degree of environmental benefit, users are being urged to consider a range of factors that contribute to overall envi ronmental performance. Broadly, these include operating efficiency, sustainability, access and installation and operating and running costs.
The electric misconception
So far, much of the debate has revolved around the misconception that all electric water-heating tech nologies are inherently environmen tally unfriendly. While this is true for electric immersion water heaters, it is not so for heat pumps. In fact, heat pump technology is incredibly energy efficient, with some units displaying typical operational efficiencies of 300 per cent — for every 1 kW of electrical energy used to operate the heat pump, 3 kW of heat energy is trans ferred into the stored water.
Typically, 75 per cent of the energy used in heat pump applications is taken from the air we breathe and can be considered ‘free’ or ‘renew able’. The remaining 25 per cent can be obtained from renewable energy sources, effectively making the heat pump a ‘zero-impact’ water-heating technology.
Renewable sources of electricity generation are expanding every year, with homeowners already provided access to these ‘clean’ energies as an option from their provider. Over time, with a greater proportion of electricity being sourced from renew able means, the overall carbon impact of electricity generation has the potential to fall. Gas-fired appliances, by contrast, offer much less scope for further reducing greenhouse gas emissions into the future.
In recent times in Australia, heat pump technology has been accused of not being a renewable energy tech nology due to the electricity required to drive the unit’s internal compressor — despite this being a small amount. In fact, harvesting energy from the air as a heat pump can be likened to a solar water-heating system harvesting energy from the sun. Both technolo gies use a small amount of electricity — the heat pump to run a compressor and the solar system to run a re-circu lation pump.
Interestingly, European law recent ly recognised heat pumps as a renew able energy technology, acknowledg ing the potential of aerothermal ener gy (stored in the air), geothermal energy (stored in the ground) or hydrothermal energy (stored in stand ing water) as sources of renewable energy. It’s only a matter of time before this decision flows through to the Australian market, where climate conditions are even more conducive to heat pump operation when com pared with Europe.
Rebates and rewards
The effectiveness of the government- funded Renewable Energy Bonus Scheme rebates and the REC pro gram has been called into question by some groups. While it stands to rea son that rebate schemes must be eco nomically viable and impervious to rorters, they have been put in place to provide assistance for homeowners wishing to make the transition to ‘greener’ water-heating technologies. With hot water accounting for 40 per cent of annual household energy bills, it makes sense to develop a frame work aimed at improving efficiencies in this area.
At the time of writing, the rebates for heat pumps were $600, while solar technologies were eligible for a rebate of $1,000 — both technologies deliver similar energy efficiencies.
Gas, on the other hand, does not present a long-term, sustainable water-heating solution as it is a non- renewable fossil fuel. Furthermore, gas resources are expected to decline in the years to come, eventually resulting in higher gas tariffs.
There will be a point in the future at which the government will have no choice but to transition the popu lation from gas to more renewable energy sources. When we inevitably reach this point, we can safely pre dict that whatever government tran sition scheme is implemented will be far more costly than any existing rebate program.
At present, gas hot water units generally deliver burner heating effi ciencies of around 80 per cent to 85 per cent. However, they do so by burning a non-renewable fossil fuel. While they may be somewhat opera tionally efficient, their impact on the environment is far-reaching. Further efficiencies can only be gained with improvements to burner/combustion technology. Here, potential efficien cy improvements are in the single figures.
Conversely, heat pump technolo gies deliver operational efficiencies in the region of 300 per cent and have the potential to improve further as compressing, refrigeration and condensing technologies are enhanced into the future. Adopters of heat pump and solar technologies will be future-proofing their homes against rising energy costs. Along with optimising carbon footprint, the heat pump’s operational efficiencies will reward homeowners with dra matically reduced ongoing operation costs when compared with LPG and legacy technologies.
The Australian answer
Australia’s enormous geographical area and climatic diversity present additional challenges to providing homeowners with energy- and cost- efficient water heating solutions. A recent Regulatory Impact Statement centred on the hot water industry reported that of the 3.7 million homes currently dependant on electric hot water, more than 50 per cent are not connected to retic ulated natural gas. Here, heat pump technology, solar units and bottled gas are the only hot-water heating options.
With bottled gas an expensive — and often prohibitive — alternative, the challenge is for heat pumps and solar systems to provide domestic hot water in these areas. Given that heat pumps and solar systems deliver simi lar operational efficiencies, homeown ers will look to other factors when choosing their hot water solution.
The heat pump’s straightforward installation requirements present advantages over solar technologies. Importantly, installation can be per formed by any plumber — there is no need for refrigeration or gas fitting training. This avoids costly and time- consuming set-up and maintenance associated with the specialised roof- top installation of solar system panels and the long runs of water reticula tion pipework.
Perhaps even more important is the heat pump’s ability to operate at any time of day. Unlike solar tech nologies, heat pumps can continue to operate at night, even where tem peratures drop to -20°C. Here, heat pumps equipped with ‘active defrost’ capabilities permit households to generate hot water at colder air tem peratures.
Moving forward, the ‘replacement water-heating technology’ landscape looks set to evolve further — a real impediment to people who don’t have the time luxury to fully investi gate all technologies on offer and keep abreast of the latest regulatory and rebate developments.
Here, designers and builders are urged to consult with industry experts to ensure their water-heater of choice delivers both environmental and operating efficiencies, along with installation and maintenance flexibility — now and into the future.
Glenn Day is Stiebel Eltron Australia’s general manager — renewables. He has 12 years experience with the company and is a previous member of the Australian Standards Committee CS- 028 (Solar Water Heaters and Heat Pumps design performance standards). For the last six years has been a member of the Clean Energy Council, Solar Hot Water and Heat Pump Directorate.
