Xtreme Power, which is commercializing a battery concept developed around the same time Nirvana broke into the Top 40, has raised a third round of cash.

The company plans on announcing its Series C funding tomorrow. In a SEC filing in June, it stated that it has raised $18 million of a $29 million round. More might have been landed since then.

The company's dry-cell battery was initially developed in the early '90s by Corning, British Aerospace and Ford Aerospace. Like a lot of green technologies -- jet fuel from coal, thermal mass air conditioners, opposed piston/cylinder engines -- the battery was both ahead of its time and too expensive back at its birth. It then died after the energy crisis of its day passed. Xtreme obtained the intellectual property and is now making another go at it.

Whether Xtreme provides a product or a service is an intriguing question. In many instances, it will be both. It depends on the structure of the contract. (Flywheel manufacturer Beacon Power has already moved toward astorage-as-a-service model.) In Hawaii, Xtreme's equipment will be deployed for voltage regulation at a wind farm. Department of Energy loans will provide the cash for both the turbines and the dry battery pack.

Xtreme also wants to integrate its batteries into the solar parks erected and operated by Clairvoyant Energy. Clairvoyant developed a 12-megawatt rooftop solar project in Zaragoza, Spain with General Electric and Veolia Environnement. Last year, Xtreme and Clairvoyant formed a joint venture to resuscitate a Ford manufacturing facility in Michigan.

"The new approach would be integrating our approach with large-scale solar," CEO Carlos Coe told us last November.

Analysts have varied views of the company. Some believe it could provide battery packs that undercut the cost of lithium ion for grid storage. The $500 per kilowatt-hour level, which lithium has yet to reach, is well within the capabilities of Xtreme, some have said. Others sniff that the company's product is nothing more than an advanced lead acid battery.

In the end, what will matter is what the utilities and power providers have to say about it.