Batteries on wheels, when cities become power plants
A key question for those who have solar panels installed is how to make the best use of the power they generate.
The typical household uses most power later in the day, when the sun is lower (or set), and less (or no), energy is being produced by the solar panels. The question is how to make use of the more abundant solar energy available earlier in the day.
The obvious answer is to install a home battery (such as the one we have at the Sustainable Macleod Community Garden), and store the energy for use when required. Choosing this option doesn’t come cheap though. Household batteries (such as the Tesla Powerwall), typically cost over $10,000, putting them beyond the budget of many households.
A possible solution for those who have an electric vehicle, is to use the car as a battery to feed power into the electricity grid. Simply put, the car charges from the solar panels during the day and feeds the stored energy back to the grid.This approach is usually termed vehicle-to-grid or V2G. Also possible are vehicle-to-load (V2L) and vehicle-to-home (V2H). The term bi-directional charging is also used, illustrating the two-way flow of power.
V2L has been used recently by a Gold Coast family during a blackout. Owning an EV with V2L capability, they were able to power fridges and their son’s dialysis machine. In this case, both appliances were plugged directly into the car’s outlet, without connecting to the house wiring. A major benefit was that the son could stay safely at home, rather than having to go to hospital for treatment.
This is the simplest form of bi-directional charging and does not require any modification to the house.
V2H allows the car’s battery (usually 4-5 times bigger than a standard home battery), to store energy during the day and power the entire house at any time. This requires a bi-directional charger, so that power can be sent to the car from the solar panels, or from the car to the home. The car is effectively a household battery on wheels.
V2G is able to feed energy from the battery to the electricity grid. This also requires a bi-directional charger. There is a great deal of interest in V2G currently, because it has the potential to ‘even out’ the supply of electricity to the national grid to make it more stable. Grid stability is fast becoming a serious issue with the increase in renewable energy, which is inherently less consistent than fossil fuel generation.
The idea is that EV batteries would be charged while the grid has low demand during the day and discharge power back into the grid when demand is high. A dramatic example of how this could work was shown when 16 EVs in Canberra were able to discharge energy into the system within 6 seconds when winds shut down Victoria’s Loy Yang power station. While this was not enough to relieve the problem on its own, it showed what might be possible if V2G was adopted on a large scale. EV owners would benefit from a feed-in tariff.
The CSIRO is engaged in trials of V2G technology specifically designed for Australian conditions, and in November this year, the federal government announced new standards for V2H and V2G charging.
There is still more work to be done to make V2H and V2G a commonplace reality, however the government’s endorsement of the development means households will be able to play a greater role in Australia’s move to a sustainable energy future.
Further reading
Batteries on wheels: Australia to allow vehicle to grid installations by end of year
V2G, V2H and V2L: How electric cars can power the grid, buildings and devices
Charging ahead with EV technology
Realising electric vehicle-to-grid services
V2G Explained – benefits of vehicle-to-grid technology
If cars become batteries on wheels, cities become power plants
Canberra trial shows EVs can provide backup power to grid in blackouts and emergencies
Australia highlights vehicle to grid household standards
Climate change will affect solar power and grid stability across Australia – here’s how
Written by Paul Gale-Baker