Solar and wind energy may become primary components of our nation’s alternative energy sources. But how do we use this energy efficiently?

For example, wind power generated at nonpeak hours such as 3 a.m. can be wasted unless an efficient storage system is used. Conversely, solar energy is obviously not generated at night, yet some level of energy is still required to power homes and businesses. These energy sources require energy storage for efficient use.

Energy storage systems are available right now for commercial and even consumer use. In fact, stateoftheart energy storage systems were displayed at the Future House U.S.A. exhibit at the Beijing Olympics. The house uses a zinc bromide energy storage system to store solar energy generated during the day, for use when the sun does not generate power.

One such costeffective, longlife, deepdischarge energy storage system uses the zincbromide regenerative fuel cell, a type of hybrid flow battery. The fuel cell relies on a flowing electrolyte system. The predominantly aqueous and environmentally friendly electrolyte is composed of zinc bromide salt dissolved in water. During charge, metallic zinc is plated from the electrolyte solution onto the negative electrode surfaces in the cell stacks. Bromide is converted to bromine at the positive electrode surface of the cell stack, and is immediately stored as a chemically complexed organic phase in the electrolyte tank. Each recyclable highdensity polyethylene cell stack has 60 bipolar plastic electrodes between a pair of anode and cathodeend blocks.

Other energy storage systems include the traditional lead acid battery, lithium ion batteries, and other technologies in research. While these systems have their advantages in their target markets, such as small appliances and automotive, their use for larger bulk storage is not as effective. In general, the benefits of the zincbromide fuel cell include environmental and safety features, both during operation and in disposal or reuse lower lifecycle cost very deep discharge capability very short time to recharge and low installation and maintenance costs. In addition, it is compact and requires little maintenance. The regenerative fuel cell can also be switched off for maintenance, unlike batteries. This gives it the benefit of having no selfdischarge, which is common in batteries.

Zinc bromine batteries are deepdischarge and can last for 2 to 10 hours, depending on the rate at which energy is extracted. Since it maintains the full storage capacity at any discharge rate, the zinc bromine battery is unlike technologies such as lead acid, where the capacity measured in kilowatthours is dependent on the energy extraction rate.

Whichever system is used, however, it is not practical to use solar and wind energy without some sort of energy storage. The challenge, then, is how to use these alternative energy sources efficiently. Energy storage systems enable energy to be used when it is most needed, while avoiding waste during offpeak hours when it may be generated. This maximizes the use of wind and solar power and other alternative energy sources.

But energy storage has applications beyond solar and wind power. In electric utility applications, energy storage systems can reduce the load on substation transformers and on fossilfueled power stations working at capacity during peak demand. This enables the utility to defer costly capital upgrades by charging the energy storage device at night and using that stored energy during peak times, thereby reducing the workload on both the substation and generating stations.

If recent estimates are correct and some $1 trillion is needed to upgrade the U.S transmission and distribution infrastructure, then the need for energy storage is even more urgent and compelling. Our nation’s energy sector needs renewable green energy sources. But without the ability to store that energy, much of it will be wasted. We simply can’t afford that waste, particularly when there are viable solutions available today.