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Elon Musk – The Powerwall | Tesla Home Battery

In this month’s People article, we’re looking at Elon Musk and his new Powerwall and Powerpack battery systems. If they take off, these systems might revolutionize the home storage of electricity. Anyone who has a home solar power installation knows that battery storage is essential to keep electricity available at all hours. Powerwall and Powerpacks are updates of this basic concept.

Elon Musk has been a high-tech darling for many years now. He is known as a visionary in many areas and is not afraid to push for bleeding-edge technology. He first came into public consciousness when he was part of the formation of PayPal in 2001, but had business success prior to this. Musk is most known for his involvement in SpaceX, which he owns. He has been working to make commercial space flight an economic success and has been doing splendidly so far.

Musk is also heavily involved in the green energy market. He is involved in Tesla Motors, a company he is a cofounder of and is the CEO of. They make the Tesla brand of electric vehicles. He also holds a majority share of SolarCity, the second largest provider of solar energy systems in the US. Musk has also envisioned a new form of high speed rail called the Hyperloop that could theoretically be as fast as air travel but more economical. He plans on building a test track in Texas next year.

The Powerwall

The Powerwall and the Tesla Model S car

The Powerwall and the Tesla Model S car

Late last month, Musk announced a new product that, as he said in his keynote, pretty much forms the start of Tesla Energy. It is called the Powerwall. In a nutshell, it is a wall-mounted lithium-ion battery pack that can store 10 kWh of electricity at a time. In contrast, a single car battery will only produce 24 Wh, far less! Most current off-grid home storage systems must use a big bank of batteries combined with strict conservation tactics to be viable. Powerwall has the potential to make battery rooms and battery maintenance obsolete.

How the Powerwall integrates with your Solar PV system

How the Powerwall integrates with your Solar PV system

The reason it can store so much energy is because it uses lithium-ion batteries, which are the standard batteries in many industrial and electronic devices. Your laptop, smartphone, and tablet all run on this technology. However, lithium-ion batteries at a scale necessary for home power storage have been out of reach due to their costs. If Powerwall works and many people adopt it, the prices of batteries will plummet. Demand does seem to be there. Just a couple weeks after the announcement, 38,000 preorders for the home version were placed on the site. A retailer in Texas has pledged to sell Powerwall in their stores.

Powerwall also has a lot of built-in features. First, it is designed to be charged by either the grid or by solar panels. Musk’s vision prefers solar panels but charging the battery off the grid could cut power costs by up to 25% and pay off within 3-4 years or even faster in places with net metering or where electricity costs are very high like California and Hawaii. It also has a built-in dc-dc charge controller and a thermal safety system using liquid cooling. The units are meant to hang on a wall either inside or outside so there is no need for a battery room.

The system is also modular. Up to nine units of the home version can be connected at a time. 90 kWh is plenty for any home if you consider the following statistics:

  • Flat Screen TV: 0.1 kWh /hr
  • Lights Per Room: 1 kWh /hr
  • Laptop: 0.05 kWh /hr
  • Refrigerator: 4.8 kWh /day
  • Clothes Washer: 2.3 kWh each use
  • Clothes Dryer: 3.3 kWh each use

Multiple Powerwalls

Even with an HVAC unit running on top of it, a home is not likely to need nine of these. But a strip mall or a small grocery store might! It’s also an attractive device and comes in several colors.

What about the cost? The unit is available for preorders now for $3500 for a 10 kWh version and $3000 for a 7 kWh version. Units are expected to start shipping in a few months and then ramp up when Tesla’s Gigafactory opens up in Nevada next year. That price should drop pretty quickly if the product sells well.

The Powerpack

Musk doesn’t want to stop at just home energy generation though. He wants his battery technology to be used by big businesses and utilities as well. Enter the Powerpack, a modular system that contains several Powerwalls.
One of the big problems with lithium-ion batteries is that they get very hot as they get larger. If you make the battery too big, it will catch fire. You may be familiar with the problems that Toyota has had with some Prius batteries catching fire. This is the source of the problem.

The Powerpack

The Powerpack

The big technology shift in the Powerwall is a way of splitting the power cells into much smaller units and to use a form of passive liquid cooling to keep the cells heat in check. No one cell gets hot enough to cause a problem. The Powerwalls are stacked inside of the Powerpack much like servers are stored in a server rack, a well-tested design that can dissipate heat well.
Lots of Powerpacks

Lots of Powerpacks

According to Musk, the Powerpack is infinitely scaleable. You could create gigawatt/hour power storage stations using this technology. One utility company has already taken him up on the offer and wants to build a 250 megawatt power storage station using this technology. Businesses can buy a single Powerpack for $25,000, or lease it from Tesla at a lower price. 2,500 orders have been placed so far. Each Powerpack provides 100 kWh of electricity.

Musk’s Energy Vision

Musk’s ideal energy vision is to see the need for fossil fuels eliminated through extensive Powerwall and Powerpack installations combined with solar and wind power stations. According to his calculations, the amount of solar panels necessary to get America energy independent is about the size of a quarter of the Texas Panhandle.

The number of batteries needed is a tiny fraction of that space, if they are Powerwalls and Powerpacks. The advantage of using solar panels and wall-mounted units is that new space doesn’t have to be cleared out. Home owners just use their existing solar systems or the grid to start their own power storage stations.
How many units would it take? Here are his estimates:

  • With 16,000 GWh (160 million Powerpacks), the US can supply all its electrical needs.
  • With 90,000 GWh (900 million Powerpacks), the world can supply all its electrical needs.
  • With 200,000 GWh (2 billion Powerpacks), the world can cover all heating, transportation, and electricity needs.

Never let it be said that Musk doesn’t think small! He is also releasing large amounts of information about Powerwall and Powerpack to companies that want to take a stab at making their own versions, in essence open-sourcing the product. That way even if something were to happen and Tesla folded, the information would be available for someone else to use. He hopes that this system will boom in third world countries like cellular phones boomed over land lines to bring electricity to new region of the world.

The Gigafactory mentioned earlier is hoped to be a practical testbed for large-scale use of Powerpacks. In fact, the Gigafactory itself is seen as a product that other companies could copy for their own manufacturing facilities.

If all goes according to Musk’s dream, he sees that global CO2 emissions will only curve up slightly during the adoption process then quickly flatline.

Specs for the Powerwall

Powerwall Specs
As mentioned, there is a 10 kWh version and a 7 kWh version. The 10 kWh version is designed for power backup situations or in places where electricity is intermittent. The 7 kWh version is for daily cycle applications. The batteries have a 10 year warranty. Does this mean that the batteries will last at least 10 years? In 2013, scientists said that the average EV car battery lasts between five and twenty years, so this is not an unreasonable length of time for a warranty.

If you’re already familiar with solar systems, then you’ll be interested in the following:

Efficiency: 92% efficiency round trip from panel to Powerwall to DC device.
Power: 2.0 kW continuous power per unit, 3.3 kW at peak
Voltage: 250 – 350 volts
Amperage: 5.8 amps nominal, 8.6 amps at peak

So it does appear that one unit could power all of the modern conveniences listed above, though it also seems that more than one unit will be needed if a family wanted to keep up their modern level of energy usage. A household skilled in energy conversation may only need one though.

The battery can operate at a pretty high temperature range, up to 110 degrees, but it can only handle cold temperatures to -4. People in northern climes may need to find a space in the garage or even the home to keep the unit warm enough to operate.

The unit itself is 51.2” x 33.8” x 7.1” and weighs about 220 pounds. It does not come with an inverter and installation by a trained electrician is required. The Powerwall is compatible with both AC and DC systems, and has logic to charge itself from the grid during times of lower energy costs.

Potential limitations

There are some possible downsides that could put a dent into Musk’s dream that must be acknowledged. First, are there enough materials for these systems to deploy them at the scales he wants to? Humans can build things at that scale, just look at the number of vehicles on the road today and how fast they’re replaced, but if there is a limited resource either in the batteries or in solar panel systems we could run up against “peak resource” before the dream is realized.

Second is how to handle the old batteries. All batteries do eventually wear out. Will Tesla have recycling programs in place to handle all that lithium?

Finally, will the product work as advertised? We’ll find that out sooner rather than later considering all the buzz that is happening around it. Lithium-ion batteries do have drawbacks. They take a long time to make and they’re expensive, though prices are dropping. We talked about the heat issues before, but the cores in each Powerwall are about the size of a flash drive. No single battery cell creates a huge thermal problem and they’re compartmentalized.

There is also the chance that a new battery technology could come along to replace the problems of lithium-ion, or efficiency improvements in renewable energy generation or power conversion so less power is necessary.

If you know your electrical history, Edison’s original design was to have a DC generator in every building supplying electricity for that building. It’s shocking to think of the health hazards from a fossil fuel generator operating in every building would have caused, but in a way we could be coming full circle. Imagine if every building used something like a Powerwall and a renewable energy source. However, like any other energy improvement, people must watch their own usage. There is a sneaky principle in energy efficiency circles called Jeavons Paradox. The more efficient a resource becomes to use, the more it is used until the efficiency gains are eliminated. It’s an economics problem that all people interested in energy conservation should think about.

However, the Powerwall is a bold vision and we hope it succeeds even on a small scale. An energy-conscious community or household that wanted to go off-grid but didn’t want to deal with lead-acid batteries could find that their dream is possible with this device. And out of the many ideas that have come out to deal with the world’s fossil fuel problem, Musk has the tenacity, the talent, and the income to make a serious try at bringing his vision about.

He’s already well on his way to mastering rocket science with SpaceX. How hard could world-wide energy independence be after that?

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