Confused by the home battery market? This should help

Australia has one of the highest proportions of household solar PV systems in the world. However, adoption of small-scale energy storage to support these domestic PV systems has not yet reached the same scale.

This is perhaps a little surprising as energy storage is vital in maximising the benefits of solar power. Moreover, the market conditions are improving for rapid growth in domestic-scale solar and battery storage installations: electricity prices are high and feed-in tariffs for solar PV are comparatively low.

The market for behind-the-meter battery storage applications in Australia (and around the world) is currently being held back, in part, by the difficulty end-customers face in choosing the right battery system for their needs. Different manufacturers report their product specifications in different ways, making it almost impossible for the average end user to compare them.

Helping Australian consumers decide

Two critical aspects of battery systems are safety and performance. The recently released AS/NZS 5139 standard tackles part of this issue by laying out general installation and safety requirements for new battery energy storage systems (BESS).

The other side of the question is performance. For example, if one manufacturer reports a lifetime of six thousand cycles under certain test conditions while another claims ten thousand cycles with no explanation of how that was measured, how do you know which battery energy storage system is best for you?

To address this issue, a consortium comprising DNV GL, CSIRO, Deakin University and the Smart Energy Council has undertaken a project to develop a draft Australian Battery Performance Standard.

Co-funded by ARENA and the Victorian Government, the project is defining standardised performance testing protocols and reporting to provide consistency in reported performance.  This will provide consumers with confidence in the reported performance and enable comparisons between different technologies in an easy manner.

The draft standard will be application-specific, in that it will only consider battery systems intended for domestic and small-scale commercial solar + battery storage installations (up to 100 kW power and 200 kWh energy). It will also be specific to Australian climatic conditions and use cases.

Beyond that, it aims to be as widely applicable as possible and is technology agnostic. Hence, the standard will make it easier for people to understand how reliable batteries are and how they are expected to perform over their lifetime under Australian operating conditions.

Global landscape

As part of this project, the project consortium has undertaken a standards review and gap analysis, in which the project consortium initially compiled a list of 258 documents for review. This was subsequently, through broad consultation, reduced to a list of 124 covering many regions such as IEEE, IEC, UL and Australian standards.

Based on this comprehensive review, no international or local Standard was found which could be directly utilised in the Australian market to fulfil the proposed scope of the draft Standard. They either looked at larger scale installations or applied only to specific battery chemistries. And, of course, none considered the Australian environment or typical Australian usage patterns.

So, while it was possible – and indeed essential – to align with these documents on definitions for key performance metrics, the draft standard would have to be created from scratch.

Industry buy-in

To do that, the consortium has worked closely with a group of around 40 stakeholder organizations including battery manufacturers, distributors, regulators and government agencies. From this group’s feedback on the possible battery storage use cases, it became clear that the industry needed a standard that focused on a small number of use cases.

The two most relevant use cases to Australia are: PV Energy Time shift (generate by day, use at early morning and night) and virtual power plant (VPP) mode in which the battery operation combines the PV energy time shift with energy arbitrage use cases.

The PV Energy Time shift use case is currently by far the most common for domestic solar+ battery storage systems in Australia, while the VPP model is becoming increasingly popular within the solar community. By focusing on these two use cases, the standard will meet current consumer needs and support future market evolution.

Standardised testing

Based on these use cases, the draft standard specifies key performance metrics that will make it easier for consumers to compare battery energy storage systems. These are properties such as maximum and sustained power, voltage range, response time and efficiency which are all typical metrics in battery testing, but not always reported by battery system manufacturers or indeed measured in the same manner.

A fundamental part of developing the standard is to define test protocols that would help standardise how these metrics are reported so that consumers could more easily compare like with like.

These test protocols are designed specifically to provide battery performance data relevant to Australian conditions and the two use cases selected, so that it suits the range of Australian climates from Darwin to Hobart. The profiles developed are based on analysis of Australian temperatures and how Australian houses generate electricity from PV panels and use electricity to power our homes.

These test protocols have been developed and are currently being validated by carrying out a vast number of tests on battery technologies in the present market.

Streamlining adoption

The draft standard is due to be submitted to Standards Australia in June 2020. With the large amount of work and industry liaison already put in by the consortium behind the draft, it is hoped that the adoption process will proceed relatively quickly.

As well as defining the performance metrics, testing procedures and temperature profiles mentioned above, the draft standard will include requirements on how test results should be reported. It is also expected to include guidelines to standardise the way that battery system warranties are described.

As a result, consumers should be able to compare not just the technical performance of the different battery systems but also the protection they can expect from the warranty.

To support the draft standard, the consortium will also be releasing an interim best practice guide which is intended to be used until such time as the standard is released. This best practice guide will contain the same information as the draft Standard, including a step-by-step description of how to carry out the necessary testing, as well as background information on how to apply for and claim compliance until the standard is released.

Nishad Mendis is the Australian Battery Performance Standard Project Leader, DNV GL

For more information, visit www.dnvgl.com/ABPS