New Zealanders are now familiar with heat pumps as space heaters.  These were introduced in the form of reverse cycle air conditioners, but have become known primarily as heat pumps.  These are selling in large numbers.  Not so familiar, at least as yet, is the use of heat pumps to heat domestic water (HPWH). All models of mass produced HPWH’s sold in New Zealand until 2006 came from Australia. With excess demand in Australia, supplies to New Zealand virtually stopped.  Awareness of HPWHs is consequently much lower in New Zealand than in Australia. In 2008 there were two local manufacturers and two importers.

The research concluded that:

1. HPWH’s are capable of significantly reducing the electricity required to heat water in New Zealand.  They are applicable in many situations that do not suit SWH’s.  The reduction in electricity use achieved by the HPWH’s now on sale is at least comparable to that of a SHW even in a situation that suits both;
   

2. heat pumps have not been used to provide domestic hot water until very recently.  The reason was that traditional air-conditioning technology, based on the CFC refrigerants R12 and R22, was not capable of achieving a great enough temperature lift to provide water at an acceptable temperature from winter air.  The original Quantum got around this by adding a solar panel as a heat source.  The change to HCFC refrigerants relieved this constraint and enabled the past range of Australian HPWH’s.  The introduction of chlorine-free refrigerants with substantially higher operating pressures now makes even wider temperature ranges, and enhanced low temperature operation, feasible.  The introduction of HPWH’s using CO2 refrigerant, initially in Japan, offers the prospect of even higher temperature ranges and efficiencies;
   

3. the HPWH industry in New Zealand had only a small capacity to supply HPWH units during 2006, but this situation is in the process of changing very substantially.  Some suppliers are now able to supply a large volume of HPWH units.  The numbers being installed are now limited only by the demand for this technology at the prices presently being offered;
   

4. installing HPWH’s does not require substantial additional training beyond that undertaken by normal tradesmen and installation capacity requirements are not likely to alter the ability of the industry to scale up its output;
   

5. additional suppliers are preparing to offer units for sale.  The increasing number of suppliers with varying designs of systems should, within a few months, transform the market from an oligopoly to a strongly competitive one;
   

6. the design of HPWH’s has advanced substantially in recent years, and will advance further in the near future with the introduction of revised and new models.  This will substantially improve the performance of HPWH’s in colder areas;
   

7. HPWH’s cannot be manufactured at the prices now prevailing for heat pump space heaters.  This is mainly due to the higher costs for handling water and providing assurance of maintaining potable water quality.  The greater temperature lift required is also a factor;
   

8. a rapid introduction of HPWH’s will depend on a significant effort in a campaign to improve the public’s understanding of this technology;
   

9. a degree of Government support is likely to be necessary if rapid uptake is desired;
   

10. an important barrier to the acceptance of HPWH’s is the lack of a standard means of assessing or comparing their efficiency under New Zealand climatic conditions.  Without a relevant standard comparisons and measures are inevitably somewhat subjective and arguable.  The existing standard that comes nearest to providing this, AS/NZS 4234 “Solar water heaters—Domestic and heat pump—Calculation of energy consumption”, does not cover air source HPWH’s;
    

11. public acceptance and uptake of HPWH’s could well be enhanced by an energy efficiency labelling system.  This would give assurance of quality and performance and discourage the introduction of badly performing models.  A prerequisite is a standard for performance measurement that covers the types of air source HPWH’s that are used in Australia and New Zealand; and
    

it would be premature at this stage of the development of the technology to introduce a MEPS for HPWH’s.  This is an option, should experience show that there is a need.

The study recommended the following actions needed to enhance market uptake:

1. undertake the extension of AS/NZS 4234, or develop a separate standard, to cover the estimation of the performance of HPWH’s more comprehensively, including the development of a TRNSYS model or models for the principal design variants;
   

2. develop a standard method for the performance testing of HPWH’s, preferably in line with the work currently being undertaken by CEN;
   

3. investigate establishing, as an interim measure, an acceptable minimum performance for HPWH’s for the purpose of inclusion in any programme of assistance or promotion.  This should be measured at 10˚C and 80% RH, which is reasonably representative of the conditions under which they will be used in most parts of New Zealand.  This minimum COP could be set at 2.2;
   

4. once the industry has overcome its supply constraints HPWH’s should be treated on the same basis as SWH’s in any promotional programmes for energy efficient water heating; and
   

5. the development of an energy efficiency labelling scheme for HPWH’s should proceed in parallel with the development of a standard for performance measurement for HPWH’s.
   

Links:

A Consumer Association report comparing various models is available at:

http://www.consumer.org.nz/reports/heat-pump-water-heaters

The association of HPWH suppliers is the New Zealand Hot Water Association:

http://www.nzhwa.org.nz/

The unit illustrated is made by Econergy:

http://www.econergy.co.nz/

Other companies:

http://www.quantumenergy.co.nz/products/domestic-hot-water-100.aspx

http://www.rheem.co.nz/ProductGroupList.aspx?id=8

http://www.parex.co.nz/stiebeleltron/index.asp?s2=Products#Heat%20Pumps