Will Tesla's big battery launch create market opportunities for newstorageproviders? At least one U.K. company thinks so.

In the wake of Elon Musk's release of the Powerwall, Ecotricity announced that it will be starting a 100-household trial of its domestic energy storage device named "Black Box" sometime this year. 

It's a bold move for a wind developer with no track record in energy storage. It does have a great track record for excellent PR, however.

Founded by Dale Vince in 1995, who built a turbine to power the army truck he was living in at the time, the company has installed 70 megawatts of wind. With an estimated worth of $160 million, Vince has become one of the richest cleantech entrepreneurs in the U.K.

Over the years, he's used his image as an idealist, visionary hippie to good effect -- publishing green-energy manifestos, challenging Richard Branson to get serious on climate change, and being photographed in his trademark leather jacket for interviews with both the trade and national press.

In a recent interview on the Black Box energy storage system, Vince was vocal about his vision, but tight-lipped on details and practicalities of the technology.

There's no confirmed date for the pilot scheme, no mention of its chemistry and no ballpark figures for price. When we approached the company to ask about these details, we were given a polite "No comment at this stage" reply from Ecotricity's head of PR.

How realistic is the company's vision of providing domestic battery storage to every U.K. household?

According to Jonathan Radcliffe, a senior research fellow in energy storage at the University of Birmingham, if the Black Box is anything like Tesla's offering, the answer is no.

Radcliffe cites price as the major barrier. Most domestic storage systems, including Tesla's, rely on lithium-ion batteries, which, he says don't hold enough electricity to be worth the capital investment for many homeowners.

In a recent blog post, he writes: "Considering Tesla's main proposition first -- it is for a household device which is charged up and used on a daily basis, selling for $3,000. Given that we pay about 24¢/kilowatt-hour, the 7-kilowatt-hour unit holds $1.60 worth of electricity. That's an expensive wallet to carry loose change in."

In the post, he goes on to systematically demolish the economic case for buying a Powerwall unit for the U.K. home.

In an interview with GTM, Radcliffe reiterated his opinion that the economic case for Powerwall "isn't really there," and noted that anyone wishing to try out similar technology in the U.K. should take heed. His words are worth listening to. As well as being a storage policy expert, Radcliffe is helping the U.K. government’s Department of Energy and Climate Change write its energy storage roadmap.

Exactly how that storage roadmap will look is still unclear. There was a change of government in the U.K. this month -- the right-wing Conservative party now has a majority and no longer needs the support of the slightly more centrist Liberal Democrats to rule, as it had for the previous five years. Many worry that this shift will be bad for clean energy policy.

Dale Vince was worried enough to donate nearly $400,000 to the rival Labor party, stating that the Conservatives were an "existential threat" to a renewable economy.

At a recent energy storage conference, Radcliffe asked Minister Amber Rudd what her government would be doing to incentivize energy storage. Her reply was that the topic is "under review."

During our interview, Radcliffe stated that he remains optimistic about U.K. energy storage, however. And because the government has not dropped its commitment to reducing carbon emissions by 30 percent by 2020, he sees continued growth for renewables in the U.K. 

Radcliffe also said that the U.K.'s self-contained national grid makes exporting excess electricity from renewables impossible. So it's a question of store it or lose it.

But how to store it is the big question.

One model for domestic storage that currently makes no sense in the U.K. is saving up cheap electricity to sell when prices rise. That's because there are only two prices for electricity in the UK, depending on the time of day, and the differential is just too small to make economic sense. "If you have solar, you're better off just feeding anything extra into the grid straight away, and profiting from the renewable energy feed-in tariff," said Radcliffe.

But it's the cost of the storage units themselves that Radcliffe cites as the biggest barrier. He thinks the U.K. government should be following Japan's lead by developing a subsidized domestic energy storage market, which could help improve technology and expertise for profitable export abroad. Certainly the country has plenty of R&D expertise already in the field, with both Radcliffe's Birmingham University and the University of Warwick having excellent facilities and talent, he said.

Radcliffe pointed to an ongoing demonstration project that avoids the costlier elements of most domestic energy storage. The SoLa Bristol Project is backed by Western Power Distribution and Bristol City Council, using Siemens' technology and expertise from the local University of Bath. It also has government financing.

One of its innovations is to keep solar-plus-storage offerings cheap by using inexpensive lead-acid batteries, and utilizing DC directly for the growing number of devices that now fill our homes -- without the need for inverters.

Although the electricity can't be fed into the grid, it does mean that that the energy losses associated with converting DC into AC -- and then back again for computers, mobiles phones and LED lighting -- are avoided. Excess PV electricity is stored in cheap batteries until needed. So far, 30 or so homes and 10 schools are participating in the pilot.

Another company to watch, said Radcliffe, is Moixa Technology, which now has the financing for a 300-home solar-plus-storage demonstration scheme utilizing its Maslow units with lithium-iron-phosphate batteries, which store between 2 and 5 kilowatts of power. The firm plans to use the services of a satellite and pay-per-view television installer to deploy up to 10,000 units a month, should demand take off.

The Powerwall and any similar products aren't going to bring a battery revolution to the U.K. any time soon. But British experimentation continues, setting the foundation for a real domestic residential storage market.