Tesla Batteries Make a Bright Future for Energy

tesla batteries

The latest scoop on the much anticipated announcement about Tesla’s latest push for Tesla batteries.

The long-awaited Tesla battery pack for your home is now on the market. Late in the evening on April 30, Tesla CEO Elon Musk kept his promise for his hotly anticipated announcement about the company’s next product line. Musk admitted the week prior that the announcement would indeed be about the home battery he promised earlier in the year, the details of which have been quite secretive until, well, the announcement. Musk took the stage at 8pm PST on a Thursday evening to make the announcement, in which he wowed the crowd by directing people to the Tesla website, where the stationary battery is already available for pre-order and scheduled to ship within a few months.

The battery, says Tesla, “increases the capacity for a household’s solar consumption while also offering backup functionality during grid outages.” At the same time, the company said it will producing larger batteries for businesses and utility companies — listing projects with Texas-based Oncor and Southern California Edison.

With this announcement, Tesla has fulfilled the conclusion posted by Wired last week: they are no longer a car company. Tesla is now a battery company first, and a car company second. Tesla isn’t creating a new market, though. The Tesla Powerwall is not exactly the first home battery of its kind. Others exist. Most home batteries function approximately like this: batteries charge at night, when utility company’s rates are the lowest, and can then be switched on in the morning so homeowners can enjoy that cheap energy throughout the day. Batteries, as we all understand, can be juiced up from nearly any source – including a homeowner’s solar panels, provided the correct wiring is available. So, could the new Tesla battery be used to take your home off the grid?

Musk says so. The battery, which is supposed to look like a “beautiful sculpture,” isn’t the determining factor there. Yes, the Tesla Powerwall battery is designed to be powered by what Musk calls the “handy fusion reactor in the sky called the sun.” But a homeowner’s individual ability to harness that energy is what determines the answer to the “on or off the grid” question. For instance, does your home have enough solar panels or wind turbines to collect all of the energy you’ll need to power through another day? And not just one day, of course, because you’ll need to store enough energy to make it through the days when you can’t generate enough new power, like when the sun isn’t shining bright. How many Powerwall batteries would your home need to run day after day? You’ll have to do the math.

Here’s one way to think about battery usage. In 2013, the average annual electricity consumption for a U.S. residential utility customer was 10,908 kilowatt hours (kWh), an average of 909 kWh per month according to the US Energy Information Administration. If you’re an “average” consumer of electricity, that translates to around 30 kWh per day, meaning that you’d need at least three batteries to cover your power usage for one day without relying on the grid. Of course, one could probably manage to scale down their energy usage if they planned to use Tesla’s home battery system as an emergency backup.

The new home battery is a Tesla-branded product, but the car-turned-battery company won’t actually be in the business of producing the energy storage contraptions. That job will be carried out by a number of partners, including SolarCity, the solar installation company run by a pair of Musk’s cousins. In fact, some SolarCity customers are using the Powerwall batteries already, through a leasing program that Tesla and SolarCity launched, possibly to test the market.

The Tesla Powerwall battery system is priced at $3,000 to $3,500, depending on the model your home needs, and installation charges would be additional. Although the battery itself may seem cheap compared to similar batteries on the market, it’s pretty clear that this home battery isn’t targeted at your average homeowner, considering that this cost is for the battery alone and not the array of solar panels and a power inverter that one would also need in order to harness that “free” solar energy Musk likes to joke about. The $3,500 option provides 10kWh, and is designed to be a backup power supply for power outages and people wanting to live off-grid. The less expensive $3,000 version will have a 7kWh capacity, and is designed primarily to help a homeowner deal with fluctuations in energy pricing and supply to cut the cost of their power (by charging up at night when the rates are lower).

What’s the take-away? The new Tesla Powerwall battery, which can clearly be used for either home or business use, is one more notch in the belt for Elon Musk. It’s a wall-mounted rechargeable Lithium-ion battery that looks way more stylish than its competitors. The real purpose of this battery, though, is to get people excited about the prospect of turning away from fossil fuels. Musk doesn’t envision that every home in America will have a Tesla battery in the next X number of years. What he hopes, though, is that Tesla’s newest product will light a fire under other innovators in the industry to get busy working on accessible solutions to help every day people take control of their energy consumption, and the environmental costs associated with it, over a longer timeline. Could the new Tesla Powerwall save the world? Not by itself. Will it give the world a big push in the right direction? Definitely.

The truth, though, is Tesla isn’t the only company in the battery game, and whatever happens with Tesla, this market is expected to grow. A study by GTM Research and the Energy Storage Association earlier this year found that while storage remains relatively niche — the market was sized at just $128 million in 2014 — it also grew 40 percent last year, and three times as many installations are expected this year.

By 2019, GTM Research forecasts, the overall market will have reached a size of $ 1.5 billion.

“The trend is more and more players being interested in the storage market,” says GTM Research’s Ravi Manghani. Tesla, he says, has two unique advantages — it is building a massive battery-making “gigafactory” which should drive down prices, and it is partnered with solar installer Solar City (Musk is Solar City’s chairman), which “gives Tesla access to a bigger pool of customers, both residential and commercial, who are looking to deploy storage with or without solar.”

The major upshot of more and cheaper batteries and much more widespread energy storage could, in the long term, be a true energy revolution — as well as a much greener planet.

Here are just a few ways that storage can dramatically change — and green — the way we get power:

1. Helping to integrate more renewables onto the grid.

Almost everybody focusing the Tesla story has homed in on home batteries – but in truth, the biggest impact of storage could occur at the level of the electricity grid as a whole. Indeed, GTM Research’s survey of the storage market found that 90 percent of deployments are currently at the utility scale, rather than in homes and businesses.

Consider how this might work using the example of California, a state that currently ramps up natural gas plants when power demand increases at peak times, explains Gavin Purchas, head of the Environmental Defense Fund’s California clean energy program.

In California, “renewable energy creates a load of energy in the day, then it drops off in the evening, and that leaves you with a big gap that you need to fill,” says Purchas. “If you had a plenitude of storage devices, way down the road, then you essentially would be able to charge up those storage devices during the day, and then dispatch them during the night, when the sun goes down. Essentially it allows you to defer when the solar power is used.”

2. Greening suburban homes and, maybe, their electric cars, too.

Currently, rooftop solar users are able to draw power during the day and, under net metering arrangements, return some of it to the grid and thus lower their bills. This has led to a great boom in individual solar installations, but there’s the same problem here as there is with the grid as a whole: Solar tapers off with the sun, but you still need a lot of power throughout the evening and overnight.

But storing excess solar power with batteries, and then switching them on once the solar panels stop drawing from the sun, makes a dramatic difference. Homes could shift even further away from reliance on the grid, while also using much more green power.

3. Helping adjust to smart energy pricing

For a long time, economists have said that we need “smart” or “dynamic” electricity pricing — that people should be charged more for power at times of high energy demand, such as in the afternoon and early evening, when the actual electricity itself costs more on wholesale markets. This would lead to lower prices overall, but higher prices during peak periods. And slowly, such smart pricing schemes are being introduced to the grid (largely on a voluntary basis).

So in sum — cheaper, more easily available energy storage helps at the scale of the power grid, and also at the level of our homes, to further advantage cleaner, renewable energy. So if the economics of storage are finally starting to line up — and its business side to ramp up — that can only be good news for the planet.

So if I get this batter can I simply power my home?

Nope! Your house runs on AC current but the battery gives you DC current. This means that you need to take the DC current and convert it to AC current. You might have a device that does this in your car so that you can plug in household items like a computer or a coffee pot. The converter takes the DC current from the car battery and turns it into an AC current so that your laptop can then take this AC current and convert it back to DC. Yes, that seems silly but it’s true. The Powerwall does not include a DC to AC converter (or AC to DC if you want to charge from the power grid).

How long will the batter power an average home?

Tesla makes a 7 and 10 kilowatt-hour battery. Let’s look at the 10 kWh one—but Tesla says that you can stack these such that you could make a 20 kWh battery if that made you happy. But really, this comes down to the definition of power as the rate that you do work (or change energy).

We know the energy stored in the battery and we can estimate the average power the house uses. From that, I can solve for the time to use this energy stored in the battery.

What is the energy stored in a battery? The bigger Powerwall has 10 kWh. Yes, this is a unit of energy and not power. It says that you could get a power of 10 kilowatts for 1 hour. You can convert this energy to Joules if you like – it would be 3.6 x 107 Joules (1 watt is a Joule/second).

The next thing we need to calculate the run time is the power. How much power does your house use? I think 2 kilowatts is a good estimate. With that, we can calculate the time:

Five hours doesn’t seem like a long time, but I bet this would get you through the night if you are using solar power (you don’t use as much energy when you are asleep). Ok, actually you would get less than 5 hours. This calculation assumes everything is 100% efficient. In fact, the battery is only 92 percent efficient and the DC to AC converter would have some energy loss as well. If you aimed for 3 hours at 2 kW, I think you would be ok.



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