Hitachi Brings Back Heat Trough for Solar A/C

As solar energy technologies go, a heat trough is as basic as it gets. 

It’s just a parabolic mirror, which aims incoming sunlight toward a small pipe of liquid at its center. The liquid gets warmer, you circulate it, and heat energy is extracted. A very basic heat exchanger. You can build a very basic unit for cooking all by yourself.  Big ones have been used for collecting energy in the Mojave for over 20 years.

Other companies, like Hawaii’s Sopogy, are deploying “micro-CSP” units around the world for process heat, air conditioning and electricity generation.

Hitachi has updated this very basic technology for what it calls a solar air conditioning system. In this case the mirror creates electricity used to drive a refrigerator, which in turn creates chilled water. Perfect for small restaurants and bars in the Mediterranean, new resorts in Africa, or the Caribbean, where the grid is low-power, expensive, or intermittent.

The innovation is simply solar tracking. Track the Sun hands-free and you optimize your energy yield. Simple, basic, easy.

In its press release Hitachi is quick to note that air conditioning is not the only application for the new trough.

We often obsess over issues of the grid, of improving it so it will be able to buy our power, of using the solar power we generate to drive a home grid, a business grid, whatever. But solar energy is just as important off-the-grid as it is on it. Maybe more so.

As I noted recently, off-grid solar can transform Africa and the rest of the developing world, powering complex electronic devices.

Driving down the cost of efficient heat troughs will produce a second revolution. In a decade you may find it difficult to tell whether you’re off the grid or on it – you will be cooled, enjoy hot water, recharge your iPhone, and enjoy a well-cooked meal anywhere.

As will be the people who live there. And I think it’s their efficient use of this power that will drive global change.


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Dana Blankenhorn has covered business and technology since 1978. He covered the Houston oil boom of the 1970s, began making his living online in 1985, and launched the Interactive Age Daily, the first daily coverage of e-commerce, in 1994. He has written for a host of off-line and online publications including The Chicago Tribune, Advertising Age, and ZDNet. He has covered PCs, networks, telecommunications, cable technology, Internet commerce, the Internet of Things, Open Source and Health IT, He began covering alternative energy at his personal blog,, in 2007.

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