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Solar Thermal Generates Air Conditioning?


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We're cool (in more ways than one), but here's why...

Remember the heat wave?  Outside our office the temperature was 96 degrees!  But here at Sundog Solar, our office was nice and cool (a balmy 70 degrees), and rather than using old fashioned air conditioning to cool us down, we use the sun.  That same heat that is coming down outside is being collected through our solar thermal system and used to run the first solar powered adsorption chiller in NY State! 

A few years ago, after installing a solar thermal demonstration station on our roof, Jody Rael, President of Sundog Solar, observed that we had a lot of extra hot water in the summertime and thought, "wouldn't it be great to take all this extra hot water and convert it into cooling".  Soon the Sundog team had the task of finding the right equipment to make this idea become a reality.  Collecting the sunshine was the easy part, finding a machine to turn it into cool air was a lot more challenging.

Two Technologies = One Cool Customer

Ever heard of a chiller?  Chillers and chiller technology have existed since the early 1900's.  Chillers today are most commonly used to cool very large buildings, usually 200,000 square feet or larger, like hospitals, supermarkets and large factories.  Unlike an air-conditioner which uses electrically driven condensing coils to create cooled air, chillers take heat (usually from a fossil fuel source or waste heat from some industrial process) and use that heat to run an evaporative condensing cycle to create chilled water.  The chilled water is then run through a HVAC system, providing cool air to the customer. 

The idea of running a chiller on solar power is relatively new.  Finding a chiller to provide cooling to a small (4,000 sq ft) office was difficult, scratch that, make that impossible - they simply did not exist!  After an exhaustive search talking to manufacturer's in Japan, Israel and China, we found Power Partners, Inc. in Athens, Georgia, who were willing to build us a custom made chiller.  We chose Power Partners not only because they were an American company but also because they could offer us an adsorption chiller rather than an absorption chiller.  What's the difference between the two?  The adsorption models are easier to run and maintain and operate using only water as the refrigerant and silica gel as the adsorbing media and they use less electricity as there are no compressors.  Power Partners had never made a 3 ton chiller before but they were willing to take on the challenge  Now that we settled on a chiller, it was time to collect the heat. 

Our new "baby" - the Solar Thermal Chiller

Catching Rays

Solar thermal technology (collecting heat from the sun) has been practiced since the Roman times.  Anyone who's ever picked up a garden hose that's been out in the sun can tell you the water gets REALLY hot in just a few minutes.  Solar thermal collectors have evolved from passive systems to flat plate collectors, evacuated tubes, solar concentrating dishes and parabolic collectors. We use all of these technologies in our solar hot water systems that we sell and install to residential and commercial customers, providing free hot water for dishwashing, showering, etc. 

 

View of Solar Concentrating Dish

Tying it All Together

The solar chiller is part of a complicated thermal collection, storage, research and distribution system that heats and cools the 4,000 square foot office space.  It also produces the hot water used by the staff.  This system obtains the heat from 320 solar thermal evacuated tube collectors, 5 flat plate collectors, a 2 axis tracking parabolic dish and a waste vegetable oil boiler. On the heating side, if there is not enough sun, the vegetable oil boiler turns on to heat the space.

Heat from the sun and the vegetable oil boiler are blended in a large manifold where many pipes converge (think of the train tubes at Grand Central Station!). Pumps and valves direct the heat to tanks, unit heaters and the chiller, where it is used or stored.  The custom made chiller makes cold water to chill the air circulating in the building, thanks to a large tank of silica gel under deep vacuum.  In this adsorption process, the silica gel takes on and gives off moisture
which cools the circulating water which is
pumped to a coil in the air handling ducts.

It Takes a Village (or a Small but Dedicated Team!)

The chiller and heating system is the culmination of 5 years of development and optimization at Sundog.  The concept is the brainchild of Sundog owner Jody Rael facilitated by Sundog's consulting engineer, Pete Skinner, engineer/owner of E2G Solar of Chatham.  Other professionals at Sundog, Steve Mammoser, Brian Bean and Walter Nabial collaborated with E2G Solar on the design and installation of the piping and controls for the complicated system.  Performance data from the solar system has been collected for years thanks to a sophisticated data acquisition system by Solarwave from Cambridge, Massachusetts.    

Engineer, Peter Skinner (left) and Owner, Jody Rael (right)

   

 

 

Walter Nabial, Mechanic (left) and Steve Mammoser, Solar Thermal Installer (right)












 






Cooling in the Nick of Time

We ordered the Chiller in December of 2011 it wasn't delivered to us until late Spring of this year.  The manufacture had to rebuild it three times to make it work to our specifications (since it was custom built, all the engineering had to be re-calculated, tested and re-tested).  No sooner did we hook it up then the weather start to get hot!  Here we are in the (sun)dog days of summer and we are happy to report that our new chiller is working great.  We are creating chilled 56 degree water from 180 degree solar heated water.

 

Chilled 57 Degree Water Feeds the Cooling Loop

Does this show up?

155 Degree Water at 10:30AM!

The First but not the Last

One of the reasons we wanted to go ahead with this project, despite the difficulties in finding the equipment, is that there is an enormous potential for this technology in the US.  Traditional compressor-based summertime air conditioning is the leading cause of brownouts and blackouts that costs the US millions of dollars every year.  There are LOTS of buildings that have flat roofs or open land that can be used to collect the summer sun.  Solar thermal systems partnered with chillers can create cooling in the summer and the solar thermal system can keep working to provide heating in the winter, reducing fossil fuel costs and carbon dioxide emissions.  Paired with a photovoltaic system, the system becomes totally powered by the sun! 

The missing piece of the puzzle has always been the availability of a small chiller.  Hopefully that will change.  Wes Livingston, the designing engineer at Power Partners told us, "The data we obtained from your machine has proven invaluable. In all, the design you received represents a reduction in price to the consumer of over 50% compared to previous small chiller designs."

We hope that our project will inspire other companies to change to renewable powered cooling systems.  Was it worth all the time and effort?  Come on down to our office the next time the temperature's high and feel the amazing power of solar cooling!

Cool Dude (owner Jody Rael) with HVAC System

 



 


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