Batteries are the new black in the renewables world. Everyone might be talking about them but how much do you know about the basic technology?
Below are some of the standard and recognised battery systems being utilised currently including examples of their use in larger scale power supply. Later we will discuss emerging technologies and their applications in scale-able renewables.
The battery in your phone is not storing electricity - it's storing chemical energy and then converting that energy back into electricity when it's needed by the phone.
Battery use in power supply allows excess electricity to be stored for times when the sun may not be shining nor the wind blowing.
Rooftop solar technology has been mainstream for about a decade now, but grid-connected battery storage is still relatively new. This means that battery products are not at the same stage of commercialisation or mass adoption that solar panels & inverters are.
The biggest problem in considering battery storage options is capital cost. The retail price for many battery products is larger than the cost of going solar (only) with the most popular system sizes (4kW, 5kW, 6kW), and adding batteries to a solar system can easily double the price.
So conventional batteries are still often expensive and sometime unreliable to use for grid-scale storage. The new batteries coming online use materials and manufacturing processes that not only lower costs but should also allow them to last for decades.
Here are a number of the battery choices that we have today:
· Lead Acid batteries
· Lithium Ion batteries
· Flow batteries
1. Lead Acid
Invented in 1859, lead-acid batteries use a liquid electrolyte and are still in common use. They store rather small volumes of energy but are reliable and cheap. In renewable energy systems multiple deep-cycle lead-acid (DCLA) batteries, which provide a steady current over a long time period, are connected together to form a battery bank. Banks of up to 1 MW of lead-acid batteries are already being used to stabilise wind farm power generation and for backup in both off-grid and grid-tied photovoltaic (PV) systems.
2. Lithium Ion
In a dry cell battery, the electrolytes are contained in a low-moisture paste. Lithium-ion (li-ion) batteries are important as they have a high energy density, and larger-scale production due to emerging electric vehicle applications is expected to bring down their cost significantly.
A demonstration project in California will see 32 MWh of li-ion battery capacity integrated with wind turbines and Mitsubishi is beginning tests of a 12 metre container unit housing more than 2,000 li-ion rechargeable batteries. The system has a capacity of 408 kWh - enough to supply 100 households for three to eight hours and is designed to have a system efficiency of 90%.
3. Flow Batteries
Flow batteries (or redox flow batteries – after reduction-oxidation) are emerging energy storage devices that can serve many purposes in energy delivery systems. Chemical energy is provided by two chemical components dissolved in liquids contained within the system and separated by a membrane. They can respond within milliseconds and deliver significant quantities of power. They operate much like a conventional battery, storing and releasing energy through a reversible electrochemical reaction with an almost unlimited number of cycles. The great advantage is that electrical storage capacity is limited only by the capacity of the tanks.
Vanadium Redox Batteries (VRBs) are an example, with high availability and a long lifecycle. Their energy density is rather low but research indicates that a modified electrolyte solution produces a 70% improvement. Vanadium prices are volatile, though, with the increased demand for battery use likely to stress supply.
A Chinese project has a 1MWh VRB system installed, at a peak power of 750kW. Research group the Fraunhofer Institute is developing a giant 20-MWh flow battery, with a 1mW facility expected within five years.
Talk to Chameleon Energy about your energy development management needs; we are a management consultancy for the energy construction business and experts in renewable development.
Sources: MIT Technology Review, Solar Choice, Science Direct
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