The Latrobe Valley Sustainability Group with the aid of Gippsland Solar, Mirboo North Energy Hub and Latrobe City Council held a very well attended session about home battery storage options at Traralgon on the 6th of April. About 120 people heard that there are many potential options for home battery storage, but may not suit everyone yet. However, prices are expected to fall in the coming years. The average pay-back time at the moment is about 9 years.
For people in remote locations, saving tens of thousands of dollars to hook up a power line to the grid, it would be an easy decision to get solar panels and have batteries for the night-time. If you are already on the grid, it would not be a good idea to disconnect, as you would need more solar panels and more batteries.
The real potential for battery storage is for homes that already have solar panels and where the householders are at work in the day-time. It is then that solar panels are producing the most, yet most of the power produced is being exported back into the grid. Particularly if the householders were only being paid 4 cents per kWh for exported electricity, then installing batteries makes the most sense.
You can hold over some of the energy produced during the day into the evening. You can program the energy management system to charge up the batteries during the day and then when fully charged, put the excess back into the grid. In the evening, if the batteries discharge too much, then it will import back from the grid and you can even set them to charge the batteries from off-peak grid power after 10 pm. In some cases, it may make sense for the electric hot water to be heated during the day rather than using off-peak power. The variety of options is entirely up to the householder.
There are a great variety of battery technologies. Installers seem happiest with lead acid batteries, which have been used for over 100 years. They are relatively cheap and will last about 14 years if treated well. However, they can’t be discharged any less than 60% of their capacity, otherwise this will shorten their lifespan dramatically. Lithium-ion batteries, which is the type used in the Tesla Powerwall, can be regularly discharged to 20% of capacity without shortening their life. However, the presenters expressed some reticence to recommend them unconditionally as they are new on the scene and there is not a lot of data on them yet. A rare type of battery, which they did recommend was a sodium – zinc type that seems to last forever.
The most exotic of the batteries was the Australian made REDFLOW Z-Cell, which uses pumps to move solutions of zinc and bromine to charge the terminals in order to produce a galvanic cell. The makers say that this battery will happily discharge 100% and are quick to recharge, however, they can’t be considered an option for applications of less than 12kWh. Most houses would require half this.