Tesla Powerwall

Iceland, Lesotho, and Paraguay might seem entirely different on the surface, but they have one superpower in common: They're 100% reliant on renewable energy. However, large nations like the US have found it difficult to move beyond about 20-30% renewable energy.

The sticking point has been that the most abundant and affordable renewable energy sources, solar energy and wind energy both have one single problem...they are intermittent. This has meant that those opposed to investing money on renewables have argued, often successfully that they cannot be taken seriously as a replacement for conventional energy sources because they are not reliable

The two keys to making 100% renewable energy possible for electricity generation in America is:

  • affordable energy storage; and
  • finding ways to reduce the use of the electricity grid in peak times.

As the burning of fossil fuels is estimated to make up just under 40% of human caused carbon emissions and this is one of the largest issues that our society faces. Yet until 2015 no-one seemed to question the prevailing view that renewables could only ever be a small part of our energy mix.

The announcement of the Powerwall 1 by Tesla's Elon Musk in 2015 ignited a torrent of discussion and research about energy storage and the development of cost effective solar batteries. People began to hope and believe that maybe renewables could be made reliable and provide base load power if we could store power successfully.

Despite the fact that at the time of this announcement Tesla engineers had not really worked out the finer points of how the first DC coupled Powerwall would work, and what other electronics would be needed to use it, the announcement changed thinking and attitudes and set in train an historic chain of events. It threw down the gauntlet in terms of the pricing of battery energy storage. It set in motion a belief (previously held by only the most optimistic renewable energy enthusiasts), that battery storage could become affordable for average residential customers.

It also had another profound impact. It stamped Lithium-Ion batteries as the battery technology of choice for home solar battery energy storage. This set in motion billions of dollars of investment in research and development both into solar batteries and also the electronics that controlled them. Prior to this announcement it was thought that Lithium-Ion batteries would be too expensive to compete with Lead Acid batteries for solar energy storage

Despite the fact that the DC coupled Powerwall 1 is now discontinued this announcement received unprecedented attention and created amazing interest amongst both corporate executives and mom and pop homeowners.

It seemed as if people from all walks of life somehow knew that affordable and reliable energy storage was the key to making renewable resources capable of replacing fossil fuel burning electricity generation as a reliable source of base load power..and that this transition was the key to fighting man made climate change.

Since then things have moved along rapidly and now many companies have either brought solar batteries to market or are planning to do so in 2018. The Powerwall 2 now offers 14kw of energy storage and an inbuilt battery inverter for just $5,500 plus installation. The first version of the Powerwall offered only 6.5 kwh of usable storage and so this is an impressive jump in capability between two versions of a product.

But in all the hype the industry and analysts have forgotten to ask one simple question. Is Lithium-Ion the best battery technology for solar batteries and solar energy storage?

Will the Tesla Powerwall Take Me Off the Grid?

The Tesla Powerwall 1, announced in 2015 revolutionized solar energy storage three years ago, and it's successor, the AC coupled Powerwall 2 with an inbuilt battery inverter, remains the clear industry leader today. In the words of Tesla, it's a "rechargeable lithium ion battery with liquid thermal control."

Its 2016 upgrade is easily paired with solar panels, especially if your goal is to detach yourself from the grid completely. That said, Tesla home batteries will only offer a few hours of backup power. Cloudy winters will leave you wanting.

Which Other Lithium Ion Batteries Have Emerged?

Tesla isn't the only brand harnessing lithium ion power. Many other companies have recreated the technology using semi solid electrodes instead of thin layers of them. Layers certainly allow you to build the volume you need, but they do so expensively. A simpler process cuts back on price, and could even have up to 25% more capacity than conventional models. The design can be produced in a fifth of the time and reduces costs to $100 per kilowatt-hour. The product is expected to launch in 2018's first quarter, and it could become the safest lithium ion battery ever made.

Are all Lithium Ion technologies the same?

Lithium ions aren't all made alike. Traditional batteries are cylindrical, but prismatic ones are generally preferred for large solar systems. This adjustment affects the energy density, charging time, and cycle life of the cell. Cobalt anodes are too short-lived and costly for solar panels, but phosphate ones offer a high enough capacity with 1000 to 2000 cycles. To find out more about the different lithium ion batteries and varied costs, contact us for a quote.

How Can You Achieve Longer Lasting Energy Storage?

Carnegie Mellon University researchers have developed a new battery that's cheap, yet extremely durable. Sodium ions are used as electrolytes, carrying power through brackish fluid. Its positive electrodes are manganese based, and its negative ones are carbon. They work in conjunction with microgrids, but are expected to evolve to stabilize conventional grids, soon.

Are Lead Acid Batteries Still Relevant?

Lead acid batteries are the oldest models for off-the-grid systems. Their depth of discharge (DoD) is lower than other models, so their lifespan tends to be relatively short. Even so, they're one of the most budget-friendly offerings available today. There are two ways to go off-grid: by choosing a battery with enough solar energy storage to outlast cloudy days and nights, or by stocking up on plenty of batteries. Lead acid batteries are ideal for the latter thanks to their featherweight price. They cost up to a tenth of the most expensive batteries, making them a popular choice for middle class households.

Is There a Way to Use Lead Acid More Safely?

Absorbent glass mat storage (AGM) units have flat battery plates or spirals. They withstand extreme temperatures and have remarkably low self-discharge rates. Their valve systems are activated when overall battery capacity falls, which allows excess hydrogen to escape during charging. Effectively, this is a self-cooling system, so its stability is outstanding. Traditional lead acid batteries are also prone to leakage, a problem that AGMs overcome exceptionally well. They're sealed tightly and require no maintenance. They charge quickly and only lose about 3% a month to long periods of idling. Contact us if you need guidance.

Is There Such a Thing as 100% Depth-of-Discharge?

Flow batteries are a new entrant on the market, and they offer 100% DoD. If you expect to be using your batteries heavily, this is one way to increase their lifespan. Flow batteries can idle without degrading. They manage temperatures of 50 degrees C, and they contain their own intrinsic fire retardant, so they won't explode. Their modular design allows you to refurbish them easily, and simply discharging them will clean the electrodes. A 10 kWh battery will cost you about 20% more than a lithium ion model, but their lifespan is likely to make them a rising superstar in the industry. They won't take the home market by storm just yet, but price skimming should change that soon enough.

Which Solar Storage is Best for Cool Climates?

Sodium nickel chloride batteries can withstand temperatures of as low as -20C--far lower than lithium ion options can manage. They're also recyclable as they're made with benign, nontoxic chemicals. They don't need the internal cooling systems big lithium ion solar energy storage requires, and their depth of discharge is relatively high at 80%. They're still as expensive as Flow batteries, but they also carry no fire risk.

How Can I Choose the Right Battery for My System?

There's more to solar energy storage than DoD and stability. Your battery must store enough kWh for your needs, or its price must support the ability to stock up on multiple batteries. The rule of thumb is to allow for three to five sun-free days, but it's not enough to simply buy the biggest and best. Your battery must be small enough to function with your panels.

Its round-trip efficiency will determine how economical your storage will be. Of course, longevity is important, particularly if you're investing in one of the most recent battery types. Your warranty will give you an idea of lifespan, but if its DoD is too low for your needs, even the hardiest of units won't hold to its life expectancy.

Tomorrow's panels and batteries will be linked by software that monitors your consumption and automates savings when necessary. Your smart microgrid will handle it on your behalf. The future of solar is exciting-and not merely for its environmental effects. Become part of the revolution.