Solar Industries Association

Information on Solar Water Heating

What is Solar Energy and Solar Heating

Solar energy is the single most abundant form of renewable energy in the world. It is the energy that comes from the sun in the form of sunlight. This energy can reach the earth's surface with a maximum intensity of more than 1000W/m².

Solar heating is the process of taking the solar energy and converting it into usable energy for heating water.

For more information on solar energy click here.

What Forms of System are Available

There are two types of solar water heating systems available in New Zealand:

Thermosyphon systems use the theory that hot water will rise through cold water and thus rely on convection to circulate the water through the system. Therefore the solar panels need to be located below the water storage cylinder to ensure that this convective circulation can occur.
Pump circulated systems allow more freedom with regards to the positioning of the solar panels and the cylinder due to there being a small electric pump in the system. This pump is used to generate water flow within the system.

There are two ways of getting the heat from a collector panel to the storage container:

In an open loop system the cold water from the storage container is circulated through the collector and back to the storage container. This can also be called a direct heat system.
In a closed loop system a glycol type heat transfer fluid is circulated from the collector to the contaner and back to the collector in a closed loop. The heat is transferred from the loop to the water in the container via a heat exchanger in or associated with the container.

There are two types of collector both of which have a number of variations in specific design.

Flat plate.
Glass tube.

A Solar water heating system can be supplied as a packaged system or custom built.

Where a solar water heating system is supplied as a packaged system it will be supplied with all components (tank, collector, pump, controllers) which have been designed for complementary and optimal energy performance. Systems supplied and installed as complementary packaged systems can be tested for energy performance as packaged systems with nominated sized and type of containers, and any claimed performance relate to the system as a whole.

A customised system may be constructed for a special application or be where solar components from a packaged system are connected to an existing hot water cylinder. Such systems should only be put together by Approved Installers from components of packaged systems and connected to other existing components such as a hot water storage cyclinder. Where systems are custom built using components, suppliers must be able to provide evidence that the individual components meet the approapriate standard tests, and that the customised system as a whole meets any claimed performance levels by demonstrated similarity of performance to a representative product that meets the requirements of the standard.

For more information on solar water heating click here.

SIA Approved Quality Standards

As a member of the Association manufacturers and importers of overseas manufactured equipment are required to periodically demonstrate that the equipment meets the manufacturing and operating standards set by the Association from time to time and that the equipment supplied will be consistently manufactured and supplied to meet the required equipment standards.

The Association has developed a "Solar Water Heating and Manufacturing and Installation Code of Practice for New Zealand". The currently approved code is available here. Associated with the Code is a "Manual for Structural Assessment for Installation of Solar Water Heating in Domestic Dwellings" available here.

SIA administers the Code on behalf of the industry. Any comments or suggestions for improving the Code are welcomed and should be forwarded to the SIA Executive Officer.

NZ Building Code

Installation of solar water heating systems is regulated by the need for Building Consents from local Councils. To obtain a Building Consent the system installer needs to demonstrate to the Council Building Inspectors that the system installation will meet the NZ Building Code. The Code establishes the standards for installation. In particular for safe loading on roofs and safe supply of potable water.

The SIA Code of Practice sets out for Councils, the solar industry, and the public the compliance standards and good installation practices that all installations should achieve. These are set out in Clause G12 of the Code. Compliance can be achieved by installations being done to meet the Acceptable Solution G12/ASI. A specific Acceptable Solution for SWH (G12/A52) is in preparation and a draft is available here.

The government is currently undertaking a review of the Building Code. In that review the SIA position is that;

The Solar Industries Association (SIA) will assist with the review to ensure that solar water heating;

is included as an acceptable solution to meeting the sustainability requirement;
there is a form of Home Energy Rating developed as a means of measuring compliance with the Building Act 2004.
SIA will work with other industry bodies such as those interested in other energy efficiency products (insulation, double glazing, space heating etc) to ensure that the results of the review are obtained quickly and efficiently. SIA believes that by cooperative action with other industry bodies and government agencies that the energy efficiency parts of the Code will be concluded quicker. Building Code Review document available here.

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New Zealand's Solar Heating Potential

New Zealand currently provides more than 40GWh of equivalent electricity consumption per year through the use of solar water heating. It is widely thought that by 2010 this figure could be upwards of 600GWh per year. The total amount of solar energy that the New Zealand land mass collects is approximately 400 million GWh per year which gives an indication of the potential for solar energy use.

Currently the two major regions at the forefront of solar technology are Australia and Western Europe. The abundance of sunlight in New Zealand places us on an even par with the levels found in Melbourne and above that of the levels found in Europe. This shows that the future of solar heating in this country is very attractive and with greater knowledge of the technology, we can only assume steady growth.

For more information on the potential of solar heating click here.

Advantages of Solar Heating

The various advantages of solar heating include:

It produces zero net emissions of greenhouse gases, enabling both industry and government to work towards meeting New Zealand's Kyoto commitments.
solar energy is renewable, abundant and a natural energy source;
the rooftop of the average New Zealand house collects about 50 times as much energy from solar as is required for water heating;
solar water heating supplies 50 to 75% of the annual water heating energy requirement when installed correctly;
the lifetime of solar heating technologies is usually greater than 20 years;
solar heating can be easily integrated into the existing water heating systems of buildings;

The Cost

Purchase and installation costs of a commercial solar hot water system in a domestic residence are in the range of $4000 to $7000 depending on:

the size of the collector panels;
the capacity of the cylinder;
whether you are installing a new system or retrofitting an existing system;
whether you connect into the existing hot water cylinder or not; and
the degree of installation complexity, which depends on the building design.

Choosing a Solar Hot Water System

The supplier

There are a number of suppliers of different solar hot water systems. Each system will have a number of different manufacturing and performance characteristics. To choose the system that meets your situation you may find this check list useful;

Does the supplier:

belong as an accredited member to the Solar Industries Association? Only Accredited Suppliers comply with the solar Code of Practice, which ensures that their products have been tested and their service is satisfactory.
have an Approved Installer in your area who has been trained by the supplier and is experienced and familiar with their range of products. Can the Approved Installer show you documentation that shows that he/she is fully trained to install this manufacturer's systems. More than 85% of solar performance issues are related to poor installation.
provide you with satisfactory answers to your questions?
provide you with a clear specification of what equipment they will provide, who will install it, the relationship with other trades people, access requirements, layout and installation aspects?
provide you with good clear documentation of what performance you can expect from their system for your house design, location, direction, and for each of the seasons? For performance information click here.
have a quality system for supply and installation that is demonstrable? (such as ISO)
have a history of manufacturing and installing sound efficient systems?
confirm that the system has been built and will be installed to the SIA Code of Practice?
undertake to obtain the Building Consent required by your local Council. A Building Consent can be costly to obtain unless the Building Inspectors can be assured that the installer knows what they are doing and that it is actually done.
have documentation (such as owner's manual) showing on-going maintenance requirements?
have a design that will meet any frost, electricity supply interruptions, overheating safety events?
provide a written guarantee?
undertake to provide you with an owners manual after installation?
have a record of being a sound business that is likely to be around to fulfill their guarantee obligations?
provide references to other successful installations that you can follow up?
have a price that is right for you?

For additional information click here

Comparison of Energy Performance between SWH Systems

SWH system performance depends on a number of aspects in which collector performance is just one characteristic. More importantly is where and how the system is installed, how the hot water is being used on a daily basis, and how the supplementary heating controller is configured.

Most systems gives similar performance in NZ - the aspects above are more important than any differences between the systems.

Potential purchasers of systems should check if the information provided by SWH suppliers relates to total system performance or is just relating to the efficiency of the collector. Much information provided to the public by some suppliers is misleading as it only relates to the collector. Collector performance has little relevance as it is the performance of the whole system that affects the efficient use of solar energy to heat water. System performance can be significantly affected by pump flow rate, location of inlet and outlet ports on tanks, location of supplementary heating in a tank, and supplementary heating controller settings.

A standard AS/NZS 4234 is being introduced into New Zealand so that systems can be tested under standard reference conditions. This will provide a good guide on system performance in individual situations. It should be noted however that system performance calculations are based on packaged systems. Packaged systems are fully designed systems where all the components have been tested to ensure that they each meet the standard. Some suppliers are importing components and making what are called "custom built" systems. A retrofit installation where the existing hot water cylinder is used is a custom built system. The energy performance of a custom built system can not be calculated until after it is built.

The standard AS/NZS 4234 sets out a methodology for calculating the energy performance of an SWH system under reference conditions. In Australia there are four zones and in New Zealand two zones for which the energy performance is calculated.

If thermal performance of a system is to be claimed the method of calculation shall be AS/NZS 4234. This standard provides a methodology for calculating the likely energy performance of a solar system under specific reference conditions. The standard has been written so as to closely resemble actual performance but because every solar water heating application is different it is necessary to standardise variables such as hot water demand, irradiation, inclination and orientation.

The methodology is based on measurement of the performance of each system component eg collector, tank, controller and pump. The performance characteristics of each element are then combined in a computer simulation to calculate the likely energy performance of that particular arrangement of the system components and under the reference conditions.

Only packaged systems where identifiable system components are combined in specified arrangements and with specified pump flow rate, supplementary heating control settings, and differential temperature settings can have their energy performance calculated. The advantage of using computer simulation to calculate energy performance is that different arrangements or settings can be easily specified and the recalculation done.

When reference is made to a system peformance it is important that all characteristics of the system including flow rate and controller settings are specified otherwise the performance data provided is meaningless as it is not identifiable to a specific nominated packaged system.

If a supplier can not provide you with certified energy performance results defined from AS/NZS 4234 then a comparison of systems may be obtained from the Australian Office of the Renewable Energy Regulator website http://www.orer.gov.au/legislation/index.html#regulations. This site only refers to systems they have listed for the four Australian zones, but Zone 4 is similar to the New Zealand Zone 5 which covers the North Island and warmer parts of the South Island..

The list of systems is in Schedule 7 of the regulations Renewable Energy (Electricity) Regulations 2001 (incorporating Amendment Regulations 2005 (No. 2) ).

Examples of Solar Water Heating Installations

There are a wide number of typical situations where solar water heating is being installed. Examples are shown on the attached reference sheets.

Solar Water Heating Reference Installations 1.

The Future

New Zealand's ongoing commitment to the reduction of harmful greenhouse gas emissions, through internal policy as well as the ratification of the Kyoto protocol, gives potential for renewable energy options to grow. Solar heating can play a major role in this growth as it relies on our most abundant source of renewable energy, solar energy.

The recognition of this need for further growth in the use of renewable energy has provided the opportunity for solar heating to become more common in New Zealand buildings.

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General Publications on Solar Water Heating

Publications Relating to Technical Aspects of Solar Water Heating

Presentations

"Ensuring Quality Installation of Solar Water Heating Systems", presentation to Building Officers Institute of NZ Annual Conference, Auckland on 23rd April 2008 (download PDF 803KB)

Solar Water Heating and Plumbers (download PDF 281KB)

How Home Energy Rating Schemes Can Increase Energy Efficiency Initiatives (download PDF)

Useful Sites

EnergyInfoNZ
This is a portal for access to energy based information including solar energy and other energy forms.

Energy Library & Information Services (EnergyLibrary)
An independent provider of information with search capabilities for accessing publications from around the world.

Energy Efficiency & Conservation Authority
New Zealand Crown entity to encourage, promote and support energy efficiency, energy conservation and the use of renewable sources of energy.

Sustainability Victoria, Melbourne, Australia
The Australian Renewable Energy Industry Association

American Solar Energy Industries Association
The American equivalent of SIA.

IEA Solar Heating and Cooling Programme
The International Energy Agency solar heating and cooling Research Programme.

ANZSES
The Australian and New Zealand Solar Energy Society.

Consumer Solar Water Heating Buyers Guide