The solar industry is facing a big wave of battery installations with all the talk over the past couple of years starting to turn to action; the introduction of the Powerwall, and its imminent successor, the Powerwall2 being the main marketing catalyst. There are far more options out there than the Powerwall variants though.
The topic of batteries is massive, and is something that I’ll be covering here ongoing for many years to come as technologies emerge and mature.
Batteries have been around for some time in off-grid homes, mainly in large Lead-Acid banks which have a good life span if used and managed correctly. Recently however, the introduction of nicely packaged Lithium Ion batteries has reduced the space required and improved the aesthetics of batteries.
One of the key philosophies at Greenhouse Electrical Services is to promote and provide the most environmentally friendly option. With the range and complexity of batteries available it becomes quite difficult to conclude on the best battery chemistry to recommend, and different circumstances will yield a different answer.
As far as the technologies go I will briefly discuss the environmental aspects of the main battery types:
Lithium Ion – These are the batteries that you will hear the most about as they are found in Tesla Powerwalls (both variants), LG Chem and a host of smaller name brands. These batteries are currently at the front of the cost per kilowatt-hour race, however their chemistry isn’t as clean as I would like; they contain cobalt which from my research is difficult to recycle, is toxic, and requires substantial mining operations to acquire. Lithium Ion batteries are also prone to thermal runaway if damaged sufficiently; thermal runaway results in some very high energy fires. That being said, I have read that the aforementioned products have been packaged so as to minimise the risks of damage.
Lithium Iron Phosphate – Slightly more expensive than Lithium Ion, and offering similar characteristics, this type of battery does not have a nickel component. It is also much safer in terms of fire risks. It is pleasing that this chemistry is becoming more prevalent and prices are dropping. Some examples of this type of battery are the Enphase battery, SimpliPhi, and the Ampetus Super Lithium, to name a few.
Zinc Bromine: These type of batteries actually use a flow of liquids from one tank to another to generate charge. They are a little more bulky, more expensive and also have a lower peak power output, however they make up for this by being very safe (they claim that the fluids are actually fire retardants) and having a long lifespan. They are also highly recyclable. Check out the Z-Cell for an example.
Salt-Water Batteries (Sodium-Ion): This type of battery is also very safe and environmentally friendly (as friendly as a battery can be). One example is the battery from Aquion Energy. This battery technology is static (unlike the flow battery above) like a “normal” battery. Salt-water batteries do have some draw backs however: they can be very heavy and at the time of writing were priced in the mid-range of options.
Sealed Lead-Acid: This type of battery has been used in off-grid homes for over 40 years and there is no reason that it can’t continue to be used as such. They do require regular maintenance to achieve a long lifespan which most people may prefer not to do; you can’t just bolt them to the wall and admire them like modern battery variants. They also take up a lot of room and weigh a substantial amount. Due to the fact that they have been around a long time, there are recycling facilities set up to recover a lot of the components used in the batteries, however these components do include lead and sulfuric acid, so if they aren’t disposed of correctly they can become an environmental hazard.
As far as recycling the newer battery technologies (Lithium Ion, Lithium Iron Phosphate, etc.), many companies say there is no reason that their batteries can’t be recycled. Because these types of batteries are only new and are still in service, there isn’t a call for a large scale recycling facility. Theoretically they can be recycled, but as far as I can tell it’s not yet happening (due to a lack of demand). It’s hard to say just how well they can be recycled without real-world experience.
For a good comparison of the batteries that are currently available, I recommend taking a look at the SolarQuotes Storage comparison.