Solar energy systems
The most simple form of installation is where you install a solar energy system without connecting it to a battery storage system or to the grid. Energy produced is used at the time of generation to power your home. Any energy generated but not used is ‘lost’.
You can choose to connect your solar energy system to the grid, and sell any excess energy produced (but not used) back to your electricity retailer. This is known as distributed generation, and you will need to get approval from Unison to get your solar energy system connected to the network.
Incorporating a battery storage system will further enhance your ability to use your solar energy, by allowing you to store the energy generated for use outside of sunshine hours, or to sell it back to the grid.
Export meter for selling solar energy to the grid (DG)
If you’re not using all the solar energy you’re generating, you can ‘sell’ that energy back to your energy retailer. This is calculated by an export meter installed by your electricity retailer as part of your solar system installation. This process is called distributed generation (DG).
It is a requirement of the 'Electricity Industry Participation Code' that all distributed generation connected to the network (including solar PV) must have export metering, which separately meters electricity exported to the network. You or your installer will need to arrange for your nominated electricity retailer to install this export metering – there may be costs associated with this that your retailer requires you to meet.
The excess power you generate is returned to the grid via your export meter, and your retailer credits you based on the units supplied and their applicable tariff. You will need to check that your retailer offers this option, and compare buy back rates with other retailers before committing to this option. You will also need to complete Unison’s 'Application to Connect Distributed Generation' form (DG1) before installing your solar generator.
The'Electricity Industry Participation Code' requires that any home energy installation capable of injecting electricity into the network must be approved by the local electricity network. This is to ensure the safety and integrity of the network for all consumers and network staff, as well as ensure that electricity market requirements are met.
The process is straight forward, especially if you have chosen a system with an inverter model already approved by Unison.
Solar energy battery storage systems
Another way to make the most of the energy generated by solar panels is to install a battery storage system. Unison is currently trialling residential solar systems with battery storage in a Hastings suburb, which has supplied us with live reporting on energy generation, battery storage and usage.
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The battery will store excess energy generated by your solar system, and use it to power your home outside of sunlight hours. If your battery is fully charged, and you are not using all the solar energy being produced, then the excess generation can be returned to the grid via an export meter.
Solar generation coupled with battery storage provides value by allowing surplus generation to be stored for future use, therefore reducing the amount of electricity you need to purchase from your energy retailer. In the event of a network outage, your battery also acts as a back-up power supply.
Although battery storage is complimentary with solar generation, a grid connection will still be required to supply electricity, especially during low generation periods (particularly the winter months). Multiple factors including the size of your solar installation, the storage capacity of your battery, and household electricity consumption will influence the degree to which a battery storage system enables independence from grid-supplied electricity.
Battery systems are not yet a common part of solar installations, due to their cost, and relatively short life-span. There are a range of technologies from “lead acid” which is relatively cheap, (but like a car battery requires replacing every year or so), through to high-tech lithium-ion batteries which last longer but cost significantly more. You could expect to pay as much as $30,000 for a lithium-ion battery system that may last around 10 years, but the good news is that cheaper and better battery systems are being developed with prices of lithium-ion batteries expected to be below $10,000 (or roughly $1,000 per kWh) in the near future.
If going ‘off-grid’ is motivated by environmental reasons, you will need to consider the carbon-footprint of producing these lithium-ion batteries, and their disposal, as part of your environmental impact analysis. The good news is that battery systems can be retrofitted, so you can invest at a later date once the technology is more advanced and affordable.
If you would like to learn more about battery storage systems for renewable energy systems, the Australian Renewable Energy Agency’s recent report “Energy Storage Study” gives an overview of the state of storage technology today, and how it may evolve in the future. View the report here.