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‘Old’ technology batteries store power

Energy storage is the bug bear of the renewable energy world.The sun shines, the breezes flow and if you can’t use it at the time of production, this energy simply goes to waste.
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Energy storage is the bug bear of the renewable energy world.

The sun shines, the breezes flow and if you can’t use it at the time of production, this energy simply goes to waste.

This is where the battery comes in.

Conventional storage for off-grid homes or back-up systems consists of a number of lead acid batteries weighing in at upwards of 90 kg apiece.

Weight aside, acid and lead are both hazardous substances — but this old technology still provides reliable service.

The life of a battery is determined by the number of cycles it is rated for. A typical solar bank for an off-grid home, rated at 1,900 discharge cycles, will have a life of approximately 25 years if properly maintained.

Usage is also a major consideration. Lead acid battery banks have to be sized properly; too small and they are quickly drained and used up; too large and the lead plates are prone to sulfation, increasing maintenance and shortening battery life.

Another detractor to the indomitable lead acid solar storage system is its rate of charge: how fast will a battery return to full capacity?

Rate of charge is very important in systems where a generator has to run if the sun is not shining or the wind blowing. The faster a battery can regain its full charge, the less fuel will is used and the more economical the system will be in maintaining power production.

Although at present the lead acid battery is the most cost effective for deep cycle applications, alternatives are out there that are starting to compete with the old order.

Enter Alan MacDiarmid, co-winner of a Nobel Prize in chemistry for his work in discovering that plastic can behave like a metallic conductor, resulting in the development of the polyaniline or “plastic” battery.

Initially his research was with polyacetylene polymers, which proved to have superior storage capabilities to the lead acid batteries in common use.

The power density of polyacetylene is 12 times higher than lead acid and its energy density is approximately 50 watts/hour, compared to lead acid at 35 watts/hour. The power density of a battery is its capability to propel an electric car up a hill; the energy density determines how many hills you can drive over.

As with most discoveries, there always seems to be some negative dynamic somewhere and with polyacetylene it degrades in air, can’t be injection moulded and is only chemical stable in liquid form. Not great attributes for a battery.

However, polyaniline does have the properties needed for superlative energy storage, is stable in both water and air, is environmentally benign and is conducive to manufacture.

And it exceeds the basic requirements needed for energy storage. Plastic batteries went in to production in the late 1980s and are commonly found in electronic items like cellphones and laptop computers.

Now in the renewable energy storage arena, with its power capabilities, the plastic battery will likely come to dominate this sector.

Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003 and is in the planning stage for his second. His column appears every second Friday in the Advocate. Contact him at: lorne@solartechnical.ca.