A new twist on thermal storage – pv magazine USA – pv magazine USA

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New technology from an emerging company is adding hot water to the energy storage equation.

The surge in interest for storage alternatives beyond electro-chemical batteries—for reasons including efficiencies, longevity and recyclability– is raising the temperature on thermal technology as a means to store energy from PV and other sources.

Solar system designers and installers have long used hot water heating in tanks as a “diversionary load” to store excess PV-generated electricity. But such schemes required the installation of complex and costly plumbing infrastructure, between dedicated tanks and circulation systems. Newer thermal storage methods being discussed include so-called “T-Bat” thermal batteries using molten aluminum or alloys, hot silicon and thermo-chemical decomposition.  But these either remain mainly in the concept or early adoption stages, or face challenges in implementation based on the state of present technology.

PowerPanel is taking a different approach: that of combining simple, safe, and easy to manage hot water with advanced thermoplastic technology and architecture—eliminating both the issues with old-fashioned steel tanks and the inherent risks of the newer exotic, inorganic thermal storage schemes.

PowerPanel, based in Oxford, Michigan, was founded in 2007 by Garth Schultz and Rob Kornahrens, to commercialize their PV/thermal technology. Prior to Power Panel, Schultz worked in clean vehicle development on projects involving GM, Chrysler and Ford, as well as clean agriculture initiatives in Canada.  He heads up the manufacturing and engineering in the Michigan facility where all the products are made. Rob Kornahrens, CEO, was previously with thin-film solar panel maker Advanced Green Technologies.

PowerPanel’s Gen 20 thermal storage tank scraps the concept of the traditional steel tank, replacing it with durable, safe, stable and recyclable thermoplastics.  The result is a lightweight, secure, and rapidly-deployable thermal storage solution that can be set up in minutes and lasts for decades.

The company bundled the PV module and thermal together in one panel with the idea of combining two renewable energy streams, photovoltaic and thermal heating (PVT). PVT has been tried in the past, but it usually involved a PV module with a thermal “catcher” fixed on the back.  What Power Panel did was  “encapsulate” the PV with a flat-plate glazed solar thermal production unit.  It uses special materials developed for Power Panel, which gets molded into an enclosure; basically a PV ‘insert” is embedded into the thermal collector/circulatory architecture.

Along with collecting heat, it also cools the PV module and makes it even more efficient regarding electrical generation. The energy production output ratio of a PVT panel is roughly 1:4 PV and thermal, and about 2X decarbonization, compared to PV or thermal alone.  Because it harvests solar energy from two energy streams, the hybrid PVT panel is over 80% efficient at capturing the sun’s energy with combined electricity and hot water generation, much more so than PV panels on their own (about 23% depending on the type).

According to PowerPanel, the large PVT array at peak can produce 2.7kW of PV electricity and 12.7kW of thermal (hot water or another fluid) at the same time.  Both the foam storage tank and the hybrid PVT solar collector are covered by various patents.

The PowerPanel approach is based on replacing steel, glass and other materials with expanded polypropylene foam (EPP).  A molded material, EPP has a fraction of the weight of traditional materials , yet has up to twice the insulation capability at as little as 1/5th the energy storage cost of conventional tank materials and up to twice the insulation capability—in fact, a Gen 20 Tank loses just a little over 2°C of heat over a 24 hour period.  It also has superior impact and chemical resistance compared to other designs. 

inside Power Panel’s Gen 20 Tank system. All the pieces fit onto a standard pallet easily handled by two people

The patented PowerPanel Gen 20 tank is modular for ease of transportation and rapid on-site assembly. A standard shipping container can accommodate over 50 of the tanks for rapid deployment anywhere where needed.  Since both the exterior and interior liner are made from non-degrading engineered foam and plastics, the tank can be installed indoors or outdoors, or even buried at grade.

A uniquely innovative feature is the tank’s configuration for assembly.  It comes self-palletized and consists of an outer “hoop” and cover, into which the EPP foam sections are inserted along with a thermo-plastic liner.  All the pieces needed fit on the footprint of a standard pallet, making it easy to move the tank into a building or up onto a rooftop— in fact individual pieces can fit through a very small entrance, and the heaviest of them is just 10 pounds.

The entire tank assembly’s total weight just a little over 100 pounds, meaning that two people can easily unload and manage one under any field conditions.  And, the company reports that they can set one up in a matter of minutes.

The tank’s inventor Garth Schultz notes that “people in marketing always claim that something takes just ‘minutes’ without actually disclosing just how many minutes that is. But in the case of our Gen 20 Tank we’re being transparent: it takes two people all of 5 to 10 minutes—tops– to set one up.  To say our design saves valuable installation time is the understatement of the decade.”

Schultz also points out other advantages to PowerPanel’s unique storage topology.  “You can ‘cascade’ multiple tanks together using our connecting hardware to expand a system.  Since the tanks aren’t pressurized no pressure vessel certification is required.  Our system can take full advantage of the various tax and other credits out there.  We also have a range of upgrades available, including heat exchangers and water-purification systems for medical and other field uses.”

The adaptable materials that form the PowerPanel tank structure cover the range of thermal applications, enabling either hot or cold storage from 200 F to as low as -25 F.  Flexible options include customizing liners for different fluid use, depending on the need, the Applications for PowerPanel’s thermal storage and complete PV/thermal systems range from disaster relief operations to institutional and hospitality facilities—anywhere hot or cold pure water is essential to human health and well-being.  For more information contact

Real world use

The large integrated system can supply enough solar thermal water to supply an average sized hotel, along with generate supplemental electricity, and systems can be daisy-chained.  That configuration would be ideal for hospitals, campuses, and other facilities.

A Power Panel Gen 20 Tank and integrated PV/Thermal array (also from Power Panel and a patented design), on a hotel rooftop in St. Thomas, U.S. Virgin Islands.

Some commercial users of the larger integrated system (multi PV panels and tanks) include Winward Passage, a resort hotel in Saint Thomas and BVQ Lofts in Cleveland,  an apartment complex in Ohio.

The small system has seen placement in relief operations by NGOs, notably in Puerto Rico following a hurricane as well as in Ukraine, serving communities with electricity to stay connected as well as hot water for everyday living.


Mark Cerasuolo has spent nearly 30 years in the electrical manufacturing and renewable energy industries, most recently at Morningstar Corporation, a leading brand in off-grid solar components. His prior roles include marketing, training and product development with OutBack Power and Leviton Manufacturing.

The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.

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