Part 1 – Method for solar waters heaters with a volumetric capacity up to and including 700 litres
Division A – Introduction
This Part sets out the method for determining the number of STCs that may be created for models of SWHs that are small SWHs and ASHPs.
Division B – Method
The method for determining the number of STCs that may be created for a small SWH or ASHP is based on AS/NZS 4234:2008 and AS/NZS 4234:2008 Amendments 1 and 2 with additional requirements specified in this Part.
Note: Guidance on whether an SWH that is a combined solar and heat pump water heater is to be considered an ASHP or a small SWH could in December 2016 be viewed on the Clean Energy Regulator’s website (http://www.cleanenergyregulator.gov.au/RET/Pages/Forms and resources/Forms-and-resources-for-manufacturers.aspx).
Small SWHs shall be rated for climate zones 1 to 4 specified in AS/NZS 4234:2008. ASHPs shall be rated for climate zones 1 to 5 based on the five heat pump climate zones HP1-Au to HP5-Au specified in AS/NZS 4234:2008 and AS/NZS 4234:2008 Amendments 1 and 2.
The method is as follows:
Using the TRNSYS computer modelling package, format the TRNSYS deck files as set out in the TRNSYS Modelling Guidelines in Part 3 of this Schedule.
Calculate the total annual auxiliary energy use (MWh/y) for the small SWH or ASHP using the TRNSYS computer modelling package with the following TRNSYS input parameters:
a. Solar collector slope = 20°.
b. Solar collector azimuth = 45°.
c. For the climatic zones, use the weather data published by the Clean Energy Regulator.
d. Select the appropriate hot water load for the small SWH or ASHP as detailed below. A minimum delivery temperature of 45°C must be achieved in each zone for which STCs are to be claimed.
i. Select the hot water load (small, medium or large) for a small SWH. A minimum energy savings of 60% must be achieved in zone 3 for the small SWH to be rated with medium or large load.
ii. Select the hot water load (small or medium) for an ASHP. A minimum energy saving of 60% must be achieved in zone 3 for the ASHP to be rated as medium load.
iii. The percent energy savings, for the purpose of defining load size, shall be calculated as per clause 3.14.1 of AS/NZS 4234:2008.
e. The modelling of the small SWH or ASHP shall show compliance with the legionella control requirements specified in AS 3498-2009.
f. To rate thermosiphon SWHs and thermosiphon sidearm heat exchangers, use extension package TRNAUS.
g. ASHP COP and power consumption performance shall be determined from full system tests in a temperature and humidity control test chamber to the requirements of AS/NZS 5125.1:2010 including the Low Temperature Performance Penalty for Class A Low Temperature products. The performance shall be correlated using the method described in AS/NZS 5125.1: 2010. All ASHPs that operate in heat pump mode at ambient temperatures lower than the initial frosting temperature shall include the Low Temperature Operation Penalty specified in AS/NZS 5125.1:2010 and AS/NZS 4234:2008 Amendment 1.
h. The modelled lengths of piping shall be based on the following:
i. For a pumped circulation system, the length of pipe between the storage tank and the closest corner of the solar collector array shall be the manufacturer’s specification or 10 m (each way), whichever is the larger.
ii. For a pumped circulation solar preheat tank, the length of piping between the pre-heat tank and a separate series auxiliary booster shall be the manufacturer’s specification or 5 m, whichever is the larger. If the auxiliary booster is integral with the pre-heat tank, then the actual pipe lengths shall be used.
iii. For a thermosiphon solar preheater, the length of piping between the preheat tank and a separate series auxiliary booster shall be the manufacturer’s specification or 10 m, whichever is the larger. If the auxiliary booster is integral with the preheat tank, then the actual pipe lengths shall be used.
iv. The diameter of all connecting piping shall be equal to the manufacturer’s specifications.
v. If manufacturer’s specifications for the thermal conductivity of the pipe insulation are provided for the small SWH or ASHP, then those specified values are to be used. If no such specifications are provided, then the default values of 0.06 W/(m K) shall be used for closed cell foam insulation and 0.1 W/(m K) for rubberised insulation or polytube or fibre insulation.
i. All other input parameters and control strategies must be those used in the actual small SWH or ASHP.
j. Input parameters and control strategies are subject to modification by Division C of this Part.
For:
a. Small SWHs (other than gas boosted SWHs) and ASHPs, subtract the total annual auxiliary energy use for the small SWH or ASHP, calculated in step 2, from the energy use of the reference electric water heater in AS/NZS 4234:2008 supplying the same load (Table A10 AS/NZS 4234:2008) to determine the displaced energy.
b. Gas boosted SWHs, use Appendix G of AS/NZS 4234:2008 Amendment 1 to determine the displaced energy.
Convert the displaced energy to MWh/y.
Multiply the displaced energy in MWh/y by 10 to determine the 10 year MWh savings.
Round down the 10 year MWh savings to the nearest lower whole number.
6A. If the small SWH or ASHP was installed on or after 1 January 2022:
(a) multiply the number worked out under step 6 by the factor specified in the following table for the year in which the small SWH or ASHP was installed; and
(b) if the result is not a whole number—round down the result to the nearest lower whole number.
Note: Step 6A (if applicable) is carried out by the Regulator in keeping the Register of solar water heaters under regulation 19C of the Renewable Energy (Electricity) Regulations 2001.
The number worked out under step 6 or 6A (as applicable) is the number of STCs that may be created for the small SWH or ASHP in the relevant zone.
Division C – Special Circumstances
The input parameters and control strategies used to calculate the total annual auxiliary energy for step 2 in the method in Division B of this Part are subject to modification in the following circumstances.
Tanks with bottom element or capable of having a bottom element fitted
For systems where a bottom element is, or can be, fitted in the tank (e.g. a dual element tank), the bottom element is to be used in this method. The minimum boost time for a bottom element shall be nominal off-peak times of 11 pm to 6 am.
Some tank designs may be modified by the installer to insert an element at the bottom of the tank even if this element has been blanked off. If a small SWH or ASHP uses a tank that can have the bottom element connected at the time of installation or at any later time, the bottom element is to be used for rating purposes.
One-shot boosting
One-shot boosting is a manual control that allows a default boost mode (such as off-peak boosting) to be overridden so that the user can satisfy a short term high demand for hot water.
Where the system automatically resets to the default boosting mode within 24 hours of the user changing the boost mode, the one-shot boosting can be ignored.
Where the system does not automatically reset to the default boosting mode within 24 hours of the user changing the boost mode, the boosting mode activated by the manual control must be taken to be active at all times.
SWHs with hybrid photovoltaic/thermal solar collectors
For a small SWH or ASHP that utilises one or more photovoltaic/thermal (PV/T) hybrid solar collectors, which generate both electricity and useable thermal energy from the same collector, the following testing regime must be documented.
(a) PV output
The PV output shall be assessed using a collector with the water heating part of the collector empty.
(b) Water heating output
The thermal efficiency of the collector shall be assessed in accordance with AS/NZS 2535:2007 with the PV output set to maximum power conditions. The electrical output of the collector shall not be included in the thermal efficiency assessment.
Note: A small SWH or ASHP with PV/T collectors will only be eligible for STCs as a SWH in relation to the water heating component of the system.