The Future of Evacuated Tube Technology

In the North American marketplace, solar thermal – and particularly evacuated tube technology – is currently facing an uphill battle for adoption and recognition.  Consumers in the market have embraced photovoltaic technologies, what many would refer to as the ‘sexier’ of the common solar technologies, but have largely overlooked the many factors that make evacuated tube systems a prime choice for the moderate climates of North America and the many innovative emerging applications of solar thermal energy.

When looking to the future of solar thermal applications - hydronic space heating, hot tubs, saunas, and of course domestic hot water are only the applications that have seen widespread adoption so far.  Wit  h solar thermal dehumidification and absorption cooling on the horizon among a number of other potential functions, the increased operating temperatures created by evacuated tubes will be the technology of choice for these new applications.  Evacuated tube collectors are uniquely designed to satisfy the additional demand for heat these loads require.

With all this in mind, it is even more perplexing that consumers and businesses have generally shied away from investing in evacuated tube technology.  Evacuated tubes take up only about one tenth of the space of a comparable PV system and run about a quarter of the price in the majority of cases.  Finally, an evacuated tube system can reach efficiency levels of up to 75% because their tube design creates superior passive tracking whereas PV systems, even at peak performance, often fall short of 20%.

So what has been holding evacuated tubes back?  How can a cost- and environmentally-conscious consumer ignore the quicker rate of return and increased efficiency in absorption and usage of solar energy still opt for a photovoltaic system? 

The answers are prominence and production.

Prominence we have addressed in part above.  Popular media has been quick to embrace photovoltaic technology and its vast potential, and there is little argument against the fact that PV technology will be an integral part of the future of the world’s renewable energy mix.

But the media, policymakers and even those in the industry have let evacuated tubes languish as a mere cousin to solar electric.  It is an effective technology without a champion and even internationally we see the same thing; best demonstrated by the omission of solar thermal from the International Energy Agency (IEA) report to the G8 group of countries published about renewable energy in June 2008.

This is in part because electricity is easy for people to understand and easy to measure.  What is strange though is that electricity consumption, depending on who you ask, only accounts for 20%-30% of our energy requirements, and heating and cooling make up almost double that.  It is clear that more emphasis needs to be placed on the thermal requirements of the market.

But perhaps the simpler explanation is that consumers have a child-like fascination with novelty.  Consumers queue up for hours to have a new iPhone, but would never do the same thing for a proven and reliable standard issue device.  Solar thermal is tried and tested – a hurdle in a market of consumers entranced by the newest shiny things

There are attainable solutions to these dilemmas though, and the burden fortunately or unfortunately falls on those who manufacture and install these systems.  As the marketplace evolves as solar technology as a whole sees a spike in adoption, evacuated tube professionals have to shift the messages that are being delivered to the public.

The days of marketing on marvel – wowing the consumer with the novelty of it all – are behind us.  The next frontier in promoting evacuated systems will turn away from system photographs and statistics about the total square footage installed nationwide to the innovative applications and the benefits it provides the consumer – guilt-free showers and baths, radiant floor and wall heating, and the immense savings and quick payback period.

But as new applications emerge and the prominence of thermal rises, the last hurdle for evacuated tubes becomes apparent, and that is monitoring production.

Solar thermal, unlike PV, is not easy to quantify, and this has traditionally made it harder to meter. Where photovoltaic production is measured simply in kilowatt hours, heat is measured in British Thermal Units (BTUs), and sometimes less desirably in the even more uncertain meters squared of installation. 

The result of this is that these systems are often regarded – at least at the policy and regulation level – as energy saving or energy efficiency systems rather than actual power production.  This lack of metering has been a major hurdle to the inclusion of solar thermal as a source of RECS and has limited its inclusion in other legislation.  And most concerning of all is that when thermal is lumped in with efficiency measures, its price comparison is off the charts and seems unapproachably expensive when compared to double pane windows and spray-on insulation.

The first utility to adopt metering for solar heating in the US marketplace was Lakeland Electric in Florida.  They have established a unique program where Lakeland purchased and installed the thermal systems so that the power provider could generate and collect the RECs produced to sell on the open market while the consumer benefited from reduced heating bills and the ability to purchase the system over time.  The operation was small at first, but has continued to grow over time.

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