Hot water heat pumps

When it comes to heating water, there are a handful of energy sources that are used. Widely known examples include natural gas, Liquefied Petroleum Gas (LPG) and electricity. Most properties in Australia utilise one of these forms of energy, however current global and national focus on renewable energy sources has seen sustainable alternatives become more widely available and effective.

A cutaway image of a conventional compact heat pump
A cutaway image of a conventional compact heat pump

The most prevalent source of these has been within the solar industry. Various designs of hot water systems that harness the sun’s energy have become more and more popular over recent years. Justification for this comes largely from government incentives for homes and properties that install renewable hot water systems. These schemes can greatly reduce the initial outlay of installation costs to people and organisations that qualify.

Usually when people think of solar hot water systems they envision solar panels being installed on their roofs, absorbing the sun’s rays directly in order to heat water that is stored and pumped nearby. The most popular flat panel and evacuated tube systems operate on this premise; however this is another effective solar powered hot water system that is available and subsidised by the Australian government, the heat pump.

Compact Heat Pumps work by harnessing the heat from the ambient air and transferring it into water that is being circulated and stored throughout a property. The air is still being heated from the sun, so despite the fact that the energy is not being taken directly from the sunlight, these systems are still classed at solar systems. These heat pumps look very similar to upstanding hot water storage tanks, and are usually situated on the external walls of a property. Similar to other solar hot water projects, this installation can greatly reduce the running costs of an electric or gas hot water system on the average home or commercial property.

How a compact solar heat pump works
The process works much like a reverse-cycle air conditioner, displacing heat from one environment to another in order to increase or decrease relative temperatures. In the case of a hot water system, this involves moving the heat from the air outside to the internal water of a property. This temperature disparity is moved from a circulated refrigerant to the nearby water through the principle of proximity transference. This is more simply explained below.

Basically the heat pump works by pumping a unique refrigerant (a liquid composition known as R-134a) through piping around the pump. Now we all know that water has a boiling, or evaporation point, of 100°C. R-134a has an evaporation point of -26°C, meaning that it has a much colder window of temperature in which it operates. As such, air temperature that is relatively mild to water has a much greater effect on this refrigerant, causing the substance to heat at a much faster rate and more quickly and easily convert into a gaseous state. This heated gas can be moved more efficiently through the heat pump, and when combined with the use of a compressor, a considerable amount of heat is able to be generated throughout the pump’s internal piping.

As illustrated on the right, the heat pump initially utilises a fan to draw in external air, passing this air right by the R 134a in its liquid form, allowing it to absorb the heat. The cool air is then expelled from the heat pump whilst the now gaseous and heated R 134a refrigerant is compressed and sent through piping throughout the heat pump. Cold water is taken up into the tank via an inlet, and then rises up the tank as it is heated by the close proximity of the heated refrigerant. The heat is transferred until the water is suitably hot, after which it is run through the outlet near the top of the tank and sent into the water system of the house. The now cooled refrigerant converts back to its liquid form as it loses heat, and then run back up to the evaporator to begin the process once again. Insulated external walls act to minimise the loss of heat and energy efficiency as the system operates.

Benefits of a heat pump
Some of the major benefits of a compact solar heat pump are:
¢ The typical compact heat pump system will save the ordinary residential property four tonnes of Greenhouse gas emissions a year (when replacing an electrical hot water system).
¢ A heat pump system uses less energy to heat water than a typical electrical, gas, evacuated tube and flat panel hot water system.
¢ It is easy to install, especially when replacing an existing electric hot water system as it utilises the same connections.
¢ They require no roof space and operate throughout the night unlike PV hot water systems.
¢ It can also operate at full capacity when the external temperature is as low as -10°C, due to low evaporation point of the refrigerant involved.

How much a heat pump will cost
A heat pump will cost a few of thousand dollars to get installed. Depending on which installer and manufacturer the heat pump comes from, prices will vary accordingly. An approximate range of prices would see the small systems (150L) coming in around $3000, whilst the larger ones (350L) would be about double that. Federal and state government rebates, explained below, can reduce those prices considerably. Installers can also offer no or low interest repayment plans to assist in the process, but this is specific to which installer is being dealt with.

Available rebates for the installation of a heat pump
Federal
The first initiative is the Australian Federal Government Solar Hot Water Rebate provides $1,600 for the installation of Compact heat pumps, subject to several provisos. The main points are that the installation must;
¢ be installed at the applicants primary place of residence (Ruling out most commercial and industrial properties);
¢ be a new and complete hot water system that replaces an existing electric storage hot water system previously operational at the dwelling;
¢ be a hot water system that is eligible for at least 20 renewable energy certificates (RECs) under the Renewable Energy Target at the time and place of installation, as certified by the licensed installer;
¢ be installed by a suitably qualified person (for example an electrician and/or plumber).

The second federal government initiative in Australia available for solar hot water is the REC Trading Scheme. This initiative focuses on increasing the number of Renewable Energy Certificates (RECs) that the government provides to people if they install a source of renewable energy on their properties. These RECs are a market valued commodity, and can be sold back to installers and traders in order to compensate home and property owners. Both of these rebates are explained fully in the Solar Choice blog available from this website entitled œRound up of solar hot water rebates, federal and state. That article is available here;
http://www.solarchoice.net.au/blog/round-up-of-solar-hot-water-rebates-federal-and-state.html

For a full list of terms and conditions the government’s PDF application booklet can be found at the following link;
http://www.environment.gov.au/energyefficiency/solarhotwater/pubs/shw-application-booklet.pdf

More information on this rebate can also be found at;
http://www.environment.gov.au/energyefficiency/solarhotwater/

State
In addition to the two federal government initiatives, and depending on which state or territory in Australia in which the property is located, there are a number of other incentives available. The following applies only to domestic properties:
¢ In country Victoria, you can receive a $1,400 rebate for replacing most systems, so long as you are not applying for the $1,600 federal solar hot water rebate.
¢ There are no state rebates for metropolitan Victoria, but you can receive the $1,600.00 Federal rebate if eligible.
¢ In New South Wales you can receive a $600 state rebate for the 270L and the 340L system.
¢ In SA you can receive a $500 rebate if you meet the criteria.
A full round-up of the available rebates at a state level can be found on the Solar Choice blog listed below;
http://www.solarchoice.net.au/blog/round-up-of-solar-hot-water-rebates-federal-and-state.html

Well that about wraps up the most relevant points on heat pumps. As can be seen above, they prove to be a useful and valuable addition to the renewable energy market.

© 2009 Solar Choice Pty Ltd

Comments

  1. Fantastic blog! I actually love how it’s simple on my eyes as well as the data is well written. I am wondering how I may be notified whenever a new post has been made. I have subscribed to your rss feed which really should do the trick! Have a nice day!

  2. Great article… very informative…

    When it comes to heating and cooling energy, the best approach for your budget and the planet is to have a comprehensive heat pump installed.

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