Macau Matters | Power Grid Level Batteries
Richard Whitfield
A fundamental characteristic of most mains power grids around the world is that at any time the amount of electricity being generated must balance the amount of electricity being consumed. Moreover, the amount of power being consumed changes from second to second and varies widely depending on time of day, day of the week and week of the year.
In a mains power grid you cannot have just one big power-station and turn it on and leave it running at full power – you need base-load and peak load generators and you need a sophisticated control center to turn them on and off as the load varies. Base-load generators are usually coal fired or nuclear and can take hours to turn on or off (and waste a lot of energy while this is done). They are used to supply the basic amount of electricity needed, and might be turned off once each year. Hydro-generators that are powered by water leaving dams or gas fired turbines are often used for peak-load power because they can be turned on and off in seconds to match short term dynamic changes in electricity demand, but they cannot run for long periods of time and might be turned on and off several times each day.
Photovoltaic panels and wind-power generators put more complexity into the mix because they can only supply electricity when the right environmental conditions are met – on sunny days or windy days and nights. And it is very wasteful to turn them off when they could be generating power.
The end result is that mains power grids are designed with enough generating capacity to meet the highest peak demand (the worst case scenario) and then most of the generating capacity is only used half of the time. This is expensive and wasteful.
Adding large scale batteries to the grid can smooth out this mismatch between electricity production and consumption. Then you just need enough capacity to meet average demand, and you run the generators all the time and they charge the batteries during periods of low demand and you discharge the batteries to supplement the generators during high demand periods. The problem is that batteries are also expensive, especially the very large batteries needed for mains power system level energy storage.
The requirements for grid level batteries are very different to the requirements for the battery in your mobile phone (or even in your car). At the grid level you need lots and lots of power to be stored. The batteries also need to last for a very long time and survive many, many recharging cycles, say 30+ years of general use. Luckily, weight is not a significant issue but the batteries do need to be very cheap.
Light-weight, expensive Lithium Ion batteries are totally the wrong solution for grid level storage, and even the Lead-Acid batteries used in conventional cars are too expensive and do not last long enough. Several research companies are looking at different low cost, high power, long life batteries (and equivalents). One I like is the liquid metal battery technology of www.ambri.com. They are developing pizza box sized cells that are packed together into refrigerator sized modules that can be in turn packed into 40ft container sized storage systems that can supply 500kW for a total capacity of 2MWh. The company is based on research carried out at the Massachusetts Institute of Technology, and should have commercial products by 2014.
This is the kind of research I would like to see done in Macau universities. It is very practical and is tackling big issues, and does not require very sophisticated or expensive laboratories.
