I covered Isentropic back in 2009, and back then the company was looking for a $5 million Series B round. The five-year-old company, previously raised a Series A round from Credit Suisse Securities Europe and won a £250,000 ($380,112) research grant from The Carbon Trust.

The innovation behind Isentropic’s idea is an advanced heat pump connected to a super simple, low cost energy storage design. Heat pumps are basically engines that can work in reverse and Isentropic’s device can store and release energy when needed. Founders and engineers Jon Howes and James Macnaghten developed the design of the heat pump a decade ago, and then brought on Mark Wagner as chairman to help with business direction.

An isentropic process (hence the name) is a thermodynamic process that can be reversed. Chairman Mark Wagner told me back in 2009 that the key to the company’s heat pump is that it can be reversed extremely efficiently, and has an isentropic efficiency (reversible efficiency) of 99 percent.

Energy storage comes into play because the Isentropic team decided to connect their heat pump to an energy storage system using two silos full of plain old gravel (or any cheap mineral or particle that can hold heat and cold well). Using the heat pump, the system compresses argon gas to produce a temperature differential and deposits heat and cold into the two separate large silos of gravel. Energy is stored in the gravel and when the process is reversed, it can be released.

The benefit of such a system are that it could be very low cost, quick and easy to set up, and could be built in a variety of locations. Utilities are looking to add more forms of energy storage to the power grid, to store energy when it’s not being used immediately, but many energy storage options are expensive and can only be built in certain locations (in elevations or underground reservoirs). Batteries are among the most expensive options, and the most location-specific choices are technologies like pumped hydro (push water up a hill and let it fall back down) and compressed air (stuff air into a container or underground hole and then release it).

Isentropic isn’t the only startup looking to develop a super low cost utility energy storage system using gravel. Energy Cache is a startup backed by Bill Gates, Claremont Creek Ventures, and Idealab that is building a system that carries buckets of gravel up and down a hill and stores energy in much the same way that pumped hydro does. Energy Cache is currently building a pilot system in Irwindale, Calif.

Isentropic will use part of the funds to build a demonstration project — sized at 1.5 MW — of its energy storage system at a primary substation owned by U.K. power company Western Power Distribution. This idea and technology is still in the very early stages, and it will take significant funds to scale it up to see if it works on a large scale.

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Ski lift storage has been one of those topics discussed in the hallways of energy storage conferences for years. Someone was out there, the conversation went, that wanted to use a solar- or wind-powered ski lift apparatus as a pump. It would pump gravel or water up a hill during sunny periods. At night or during peak power emergencies, the gravel or water could be released. The system essentially artificially supplies the elevation that nature left out.

Such a system could even harvest regenerative power on the way down. It’s part of a segment I call macro or terrestrial storage, i.e. large mechanical devices that store power through the power of geography and gravity. Bright Energy Storage Technologies, for instance, wants to put giant plastic bags shaped like sea cucumbers connected to air hoses in the ocean. Seawater will contain and pressurize the water for free. It sounds strange, but the device could deliver power for 2.5 to 6 cents a kilowatt-hour, say the backers of the technology.

Research and project management company Escovale Consultancy Services talks about using a 100 million ton stone in a cavern to pressurize water,  similar to an idea being pursued by Gravity Power.  Think Stonehenge for the grid.

Then there are the micro-macro storage ideas: SustainX (compressing air in large tanks with water vapor), Isentropic (big tanks of hot gravel) and LightSail Energy (founded by an entrepreneur who entered college at age twelve.)

I scribbled down the name of the ski lift guys once at the Energy Storage Association conference in 2011, but I subsequently needed a paper towel and lost it forever.

Energy Cache

So who is that company? I am going to guess it is Energy Cache. Energy Cache wants to create a solar-powered pump for delivering materials to the top of mountains that can be released to produce energy. Here is one of their patents — note that one of the inventors is Bill Gross, the energetic dervish behind Idealab.

Claremont Creek Ventures is an investor and Idealab lists the company on its site. Gates himself wrote about the company in 2011 on his own blog.

Here’s a video of how the system works:

It’s an interesting idea, but one with many caveats. Terrestrial storage isn’t cheap. Compressed air energy storage, pumping megawatts of air into underground caves, has been around since the 1970s, but only a few trial systems have been built. Big projects take a lot of cash, and almost anything — geological surprises, changing world economics — can go wrong in the ten to fifteen years it can take to complete a project.

Environmental review can bottle up projects for years. Gridflex Energy has talked about building multi-megawatt hydro storage systems in Hawaii — the ocean would act as a free reservoir — and large systems in Montana. But good luck getting through the review process.

Some of the energy ideas from Idealab have stalled on the way to commercialization. Energy Innovations, a startup building concentrated solar photovoltaic technology, has reportedly put itself up for sale after struggling. Idealab also invested in Aptera, the three-wheeled electric car. The lightweight material Aptera used to build its car was fantastic — the car didn’t do so well.

Image courtesy of Andrew Miesem, Flickr creative commons and Energy Cache.

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The Utah company’s solar thermal technology uses a parabolic dish of mirrors to concentrate sunlight to heat and expand helium inside a heat exchanger to cause a piston in an engine to run back and forth. That motion then drives an alternator to produce electricity. This type of technology is generally called a Stirling engine.

Stirling engines have long been thought of as a promising technology to build solar farms, but the matchup has yet to become as popular as other types of solar thermal technologies, and at least one company has struggled to get its stirling engines built into a commercial solar project.

California regulators approved two Stirling solar projects using technology from Stirling Energy Systems totaling 1372.5 MW last year, but their developer, Tessera Solar (sister company to Stirling Energy Systems), subsequently sold them to different buyers when it couldn’t line up the financing to build them (Southern California Edison canceled its contract with one of the projects). Since then, one of the new buyers, K Road Power, has planned to use Stirling engines only for a small portion of its project while the second buyer, AES Solar Power, has said it will use solar panels instead. San Diego Gas & Electric told us it canceled the contract to buy power from the AES’s project in spring this year.

Like other solar thermal technology developers, Infinia is marketing its technology as suitable for not just solar electricity generation but also for combined heat-and-power generation. The system harvests the waste heat from electricity generation, and that heat can have a variety of uses, from heating a building to running industrial operations. Solar thermal technology developers such as Abengoa Solar and BrightSource Energy have carried out projects where the steam generated by the sun’s heat is used for cooking, showers and laundry at a federal prison and for extracting oil from wells.

Infinia raised $32 million in debt and options last year, according to another SEC filing, and another $50 million in equity before that. Investors include Equus Total Return, GLG Partners, Khosla Ventures, Bill Gross’s Idealab and Paul Allen’s Vulcan Capital.

But like Stirling Energy Systems, Infinia has seemed to also hit a few bumps in the road. Infinia began laying off employees at its previous headquarters in Washington state a few months back in order to move to Utah. The company’s CEO, Mike Ward, who came on board earlier this year, told a local newspaper, the Tri-CityHerald, that the move was to “accelerate from our R&D roots into a world-class solar generator company with geographically consolidated operations.”

However, Infinia has several installations and new customers in India. Infinia completed the first commercial installation of its technology earlier this year, reported the Tri-City Herald. The city and Infinia broke ground on a 45Kw project last year, but Infinia declined to say whether the project has been completed as planned.  Infinia also has installed a 9 KW system that was built on the rooftop of Belen’s City Hall in New Mexico.

In addition, Infinia recently sold 10 MW of its engines to solar developers in India. The deal in India involves a $30 million loan from the federal Ex-Im Bank to Dalmia Solar Power. Dalmia plans to develop the project and sell the electricity to NTPC Vidyut Vyapar Nigam, a subsidiary of the National Thermal Power Corp.

Image courtesy of Inifina 

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This type of industry already uses standard boilers, traditionally powered by natural gas. Thermata CEO Brad Hines said recently at the Cleantech Forum that the market for industrial heat via boilers is already a $26 billion business in the U.S. Thermata’s plan is to install heliostats (big mirrors) on the roof of a factory. The heliostats concentrate sunlight onto a receiver on top of an adjacent tower, which in turn powers the boiler to produce steam.

Hines said he thinks Thermata can produce steam in this way at a cost of $4.60 per MBTU compared to average prices for natural gas-powered steam, which can cost between $6 and $10 per MBTU. Beyond being lower cost, the process has far fewer carbon emissions.

However, you can probably already guess that it’s a complicated and expensive proposition to convince an industrial plant owner to commission the construction of one of these solar-power steam systems. It’s a separate tower, and then they have to connect the tower to the existing boiler and also install the solar tech on the roof. But Hines says even with the upfront cost, the pay-back period is two years for potential customers.

So far Thermata has a partnership with boiler and receiver maker Aalborg CSP, and has the benefit of the experience developed in the solar thermal incubation lab of Idealab. Hines was the founding CEO of concentrating solar photovoltaic startup Soliant Energy, and was VP of engineering for Idealab’s CPV startup Energy Innovations. Before that, he worked in NASA’s Jet Propulsion Lab for 14 years.

Hines said that the company has been backed by $500,000 in funds from Idealab and is looking for another $600,000 from investors to build its first pilot system by 2012. Competitors include Sopogy, Chromasun, Heliodynamics and Cogenra.

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First Solar already is already testing RayTracker’s technology in the field, said Alan Bernheimer, a First Solar spokesman. The acquisition doesn’t mean First Solar will use trackers for all or most of its projects. But it does expand First Solar’s menu of project engineering services, Bernheimer said.

“Tracker technology is one of a number of initiatives under development in our Systems group as part of our broader effort to enable lower LCOE (levelized cost of electricity) pricing capability and further differentiate our solution in the market,” Bernheimer wrote in an email.

“We are not announcing any new products at this time. First Solar is still evaluating the effectiveness of tracking and other advanced systems technologies and will announce product offerings through a customer release process when appropriate to do so,” he added.

Tempe, Ariz.-based First Solar is a long-time manufacturer of thin-film solar panels, and it jumped into the energy project development business in recent years. The move creates outlets for its solar panels, and the strategy has made it one of the largest project developers in North America.

First Solar has bought several project developers, including paying $297 million for NextLight Renewable Power last year and $400 million for OptiSolar in 2009. These purchases gave First Solar more than 2 GW of projects under development in North America. The company also is heading to China, and said earlier this week that it has teamed up with a Chinese energy company to develop the first 30 MW of what promises to be a 2 GW project in Inner Mongolia.

The benefits of using trackers to point solar panels to the sun have been a source of debate. Proponents say trackers squeeze more power and therefore more money from each installation. Critics say trackers add costs without providing enough returns on investments.

First Solar rival SunPower has been a big proponent of using trackers and has been developing its own offerings in that area for years.

Here’s what RayTracker says are the advantages of using its trackers: The single-axis trackers can boost energy production of solar panels by up to 38 percent. The trackers, primarily for ground-mounted installations, tilt the solar panels in the opposite direction of the sun in early morning and late in the day in order to avoid shading.

Each tracking unit, at about 80 feet long, comes with a low-voltage actuator that controls its movement. That’s a setup different from competing trackers, which are linked together row after row in each installation. The company says this distributed system simplifies installation and allows more accurate tracking. Each controller, which contains a custom processor and software, oversees the workings of 12 tracker units.

RayTracker has seen its trackers used in megawatts of projects, including a 5 MW installation in Italy and a 1.1 MW system at The North Face’s distribution center in California.

RayTracker has hired outside manufacturers to produce the equipment, Bernheimer said. Before the acquisition, RayTracker was operating out of Idealab, a technology incubator in the southern California city of Pasadena that was founded by Bill Gross. Idealab, Quercus Trust and Phoenix Fire backed the tracking company.

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Photo courtesy of RayTracker

Internet Brands, a leading operator of vertical service-oriented websites that was spun off from Bill Gross’s Idealab incubator in a public offering three years ago, has agreed to be acquired by private equity firm for $640 million. The deal will see Hellman and Friedman Capital Partners take control of Internet Brands — which runs websites such as CarsDirect.com, Loan.com and UltimateCoupons.com — for $13.35 a share, which amounts to a 46-percent premium to the stock’s recent closing price.

In a blog post about the deal, President and CEO Bob Brisco commented on the fact that the company was going private again just three years after having gone public, saying Internet Brands had managed to prosper during its period as a public company “despite the most difficult economic, financial, and advertising market backdrop in about 85 years.” The CEO also said that despite going public “just as the global financial markets began to falter,” the stock has performed better than the rest of the market, noting that the acquisition price is almost 70 percent higher than the company’s IPO price, while the NASDAQ index has fallen by 10 percent over the same period.

Internet Brands had $99 million in revenue in 2009 — a drop from the $104 million it pulled in the previous year, but up from $90 million in 2007 — and made $12 million in net income last year. The company’s share price hit a low of $4.77 early last year before rebounding to around the $10 level earlier this year. The company was founded as CarsDirect.com in 1998, and until 2007, was a unit of Idealab, the Bill Gross-founded incubator that has been responsible for startups such as Overture, which pioneered the concept of keyword-related advertising and was acquired by Yahoo for $1.6 billion in 2003.

The acquisition offer by Hellman and Friedman Capital is likely to go ahead, since Idealab still controls 64 percent of the voting shares in Internet Brands through a special class of restricted stock.

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Logitech’s box will be available in the fall. The company hasn’t made any information about pricing available yet, but a spokesperson told me today at a Logitech press event that DISH subscribers will be able to get a subsidized box through the satellite TV provider. Logitech gave members of the press a really short demo of the device, mostly showing off how it plays well with other devices while putting lesser emphasis on the actual Google platform. It also showed off two remote control apps for Android and iPhone OS that will be available at launch time.

The Logitech box prototype shown at the event featured two HDMI ports, as well as two USB ports, an IR blaster and an Ethernet port. It will initially be sold with a compact-sized keyboard, and there will be a camera for video chats available as an add-on.

Logitech’s CEO Jerry Quindlen told me that part of the reason the company embraces Google TV is the option to extend the TV experience, which in turn gives Logitech a chance to sell more peripherals. “People want to access the full web”, he said, and that adds the desire for new devices that people are used from a PC or web experience.

Quindlen also said that it’s not about adding another box to your living room, but about enabling a complete Internet experience, and said he believes people are willing to pay for that. Watch the complete interview below.

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TweetUp aims to identify relevant tweets and tweeters based on popularity, engagement, interest and also paid bidding on keywords. Though Gross has created many companies over the years through his incubator Idealab, and most recently has been focused on solar energy, TweetUp most closely resembles his great insight of the late ’90s: GoTo.com — which became Overture, aka search advertising, aka Google’s core business. TweetUp is similarly a contextual advertising system for the new web-technology-seeking-a-business model on the block, Twitter. The difference is, Gross wants to monetize the content itself, by getting publishers to pay to reach a relevant audience.

The best thing about Gross’ idea is it comes with built-in distribution and monetization. I’ve seen a bunch of really cool innovations on real-time search lately, but these startups tend to focus on the algorithm rather than the way they will matter to users. Sure, nobody’s using the TweetUp marketplace yet, but at least it has a business model.

In order to identify top tweets, TweetUp uses signals such as a Twitter user’s ratio of retweets to followers and how much they’ve previously tweeted about similar topics, but it also adds in the ability to promote your tweet or your profile by paying something like 5 cents to $1 to bid on a term. Then it builds tweets into an ad unit that other publishers can run, giving them real-time, relevant content in a widget in their sidebar, as well as 50 percent of the revenue. Publishers can also opt-in to a keyword rollover feature similar to Kontera’s that pops up a window with a few relevant Tweets when you mouse over a link in the text of an article.

Gross sees it as a way to give relevant tweets more staying power, and to help interesting Twitter users find more followers who are interested in their areas of expertise. He built the company after being frustrated that his own personal tweets from events like Davos and the TED Conference were drowned out. Gross, for all his stature and access to elite events, has fewer than 1,500 followers.

The hard part for Tweetup will be building an ecosystem of participation. And Gross knows this — GoTo was a tough sell, too. “This is not going to be an overnight business,” he told us. “It’s going to be an evangelism sell.” To kick it off, he’s offering the equivalent of $100 in TweetUp money to the first 1,000 users. Once the system is populated, TweetUp ad units will go live sometime in the next month. Participating clients and publishers include Seesmic, Twidroid, TwitterFeed, Klout, Business Insider, Answers.com and PopURLS.

I do think Gross has a point: your content doesn’t matter unless people read it, and in the modern media age, where everyone’s a publisher, audiences are harder to come by. You’ve got to work. But as a writer, it feels awfully weird to fork over money to get people to read my tweets and hopefully click through to my stories. Gross’ reply: “If you can pay a lower CPM than you can get [on your web page] yourself to drive traffic, then you will pay.”

TweetUp is not without competition; for instance, OneRiot just began offering a self-service system that publishers can use to promote their recent content on its real-time search engine and on Twitter clients. And of course, Twitter has a few ideas up its own sleeve as well.

Gross is serving as TweetUp’s CEO, and the Pasadena, Calif.-based company already has 10 employees. It has raised funding from Index Ventures, Betaworks, Steve Case’s Revolution, First Round Capital, Jason Calacanis and Jeff Jarvis.

Gross, by the way, will be speaking about his other passion, alternative energy, at GigaOM’s Green:Net conference later this month, put on by our sister site Earth2Tech. Gross was until recently the CEO of eSolar, which is using software to lower the cost of solar and produce it at a utility scale. You can buy tickets to Green:Net here.

The price point might seem ridiculously low for a device that can fundamentally change the way a family uses electricity, replace dangerous and dirty kerosene lamps, save customers money on electricity costs, and help small business entrepreneurs. But it’s high enough to create a solid business out of. And Duron has attracted an undisclosed amount of funding from investors that know how to make a profit: Bill Gross’ Idealab, David Gelbaum’s Quercus Trust, and Solgenix.

The price is also not all that cheap considering that the targeted customer makes on average between $400 and $4,000 per year in income. That’s one reason why Duron is in the process of adding in a microfinance component, where customers can take out a small loan to purchase the system.

The idea to build such a device — a plug-and-play package that includes a 5-watt solar panel, three wide-angle LEDs, a cell phone charger connection, and AC grid charger — came about in mid-2008. Howard, a Caltech grad (Gross also hailed from Caltech), and his early team began conducting research on a business idea for clean power in the developing world, and by the fall of 2008 had set their sights on an inexpensive solar home system.

When fully charged, the Duron offers three hours of bright lighting or 10 hours of dim lighting, and requires about a day of sunlight to charge the system. Eventually the company is looking to develop other energy-related products, but it’s currently focused solely on the Duron. (It also recently changed its name from Distributed World Power to Duron.)

Like startup D-Light’s solar lighting products, Duron’s device could do a lot of good by replacing the use of kerosene lanterns at night. Amit Shah, Duron’s VP of Operations, explained in a company blog post that one family who tested a Duron for a week quickly realized the benefits, and the children could more easily study at night, the mother could cook at night, and the neighbors could socialize at the house, without the smoky kerosene lamp.

Teachers, organizations and small businesses are common customers, given they can use the tool for their work. For example, schools can offer night classes with better lighting. Howard also tells us that more than half of Duron’s customers have some form of access to the grid, but that access is oftentimes unreliable and sporadic, so the Duron can make their power much more consistent.

Currently Duron is focused on selling into two of the bigger states in India — Uttar Pradesh in the north and Karnataka in the south — with plans to scale up the company throughout 2010. Howard tells us that the company is currently selling on the scale of “a few thousand devices per month” and has partnered with NGOs like World Vision.

The biggest hurdle for the 13-member team is the simplest: just doing business in rural India. Howard, who moved to India less than a year ago, has been heads down figuring out the landscape and how Duron can ramp up sales and expand throughout India and beyond. 2010 is a big year for the young firm and we’ll check back with the team later on in the year.

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T-Mobile service disappears in U.S. (Twitter)– I think my facetious tweet sums it up best: “I felt a great disturbance in T-Mobile, as if millions of voices suddenly cried out in terror and were suddenly silenced.” You don’t need Force awareness to hear about T-Mobile’s network going down. It’s all over Twitter and reports are coming in from all over the country. Hopefully, this gets resolved quickly.

iCan do Exchange at no extra charge (Gearlog) — The other day we heard that Verizon would be charging $15 a month extra for Exchange support on the Droid. That’s only for business accounts, so good news for consumers — there’s no Exchange tax.

Large population doesn’t guarantee big iPhone sales (All Things D) — The first numbers are in for the iPhone in China — the world’s most populous nation. Would you guess only 5,000 iPhone subscribers signed up with China Unicom during the first weekend of official sales? I say “official” because there are estimates of nearly two million gray-market iPhones in the country already. It’s tough be successful when you’re competing with yourself, no?

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