Science Special: Solar Energy

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SRP engineer Joel Dickinson explains how a solar project is helping to cool the Arizona Department of Emergency and Military Affairs office.

Ted Simons:
Next, we tell you about an innovative new way Salt River Project is using the sun to beat the heat. Producer Larry Lemmons tells us about this unique solar project.

Larry Lemmons:
Cold from hot. That's the basic principle behind solar thermal cooling. At the Arizona Department of Emergency and Military Affairs, SRP installed a demonstration solar absorption cooling system.

Joel Dickinson:
Right now, conventional air conditioning is a major load for SRP, and if we can explore these solar cooling technologies and avoid the peak demand with the solar, we would be in a really nice position.

Larry Lemmons:
It might look complicated, but it's a fairly straightforward process. It starts with a heat pipe.

Joel Dickinson:
Each of these vacuum pipes is an individual process and what they do is take the working fluid inside of this vacuum pipe, is in a puddle at the bottom. The sun beats down on the fins and transfers the energy to the pipe and boils that water inside of that vacuum tube. The vapor travels up the tube and transfers the heat energy when it condenses on this manifold of hot water and this is the hot water we use to drive our solar chilling process. All of the hot water we harvest with the solar array gets stored in this 1200 gallon tank. And the cooler water from the bottom of the tank is piped out to the array through this pump. And then it goes through the array, the water is heated. And then comes back and it's dumped into the top of the tank. So the water is cooler at the bottom and hotter at the top and the hot water gets stored in this 1200-gallon insulated tank. So now we have a tank full of hot water that's been created by the solar array and the hot water drives the absorption chiller and comes into this pipe and then the hot water is converted to cold water by the chiller in a vacuum. And the cold water is piped over to the building. The chilled water is pumped up through these pipes that enter this air handling unit. It's a conventional air handling unti that utilizes the cold water and the hot air from the building. The hot air gets blown over the cold coil, and we get cooled air in the building.

Larry Lemmons:
This is a pilot program. SRP and the National Guard have teamed up to see how the system works. It's producing air conditioning for the guard's eco-building.

Major Paul Aguirre:
The eco-building is a project that the Arizona National Guard did several years ago. It's made out of recyclable materials. It's solar powered; you see the panels on the roof which are separate and to add the solar chiller unit to that really underscores the eco-building's whole intent, which is to be environmentally friendly and use renewable power sources.

Joel Dickinson:
SRP has spent quite a bit of money putting a data acquisition system on this solar air conditioner so that we can harvest information and from that, we're going to hire a third party that's going to take that information and do an energy study and take a look at what are the true economics of the system. How much electricity is that chiller using? How much are we saving by using the solar hot water to drive the cooling process? And then over time, I think we would like to get that information out to the public so that they understand what are the paybacks and return on investment for this type of technology.

Larry Lemmons:
SRP hopes the technology will eventually become smaller so that the system will be much more practical for home use.

Joel Dickinson:
Right now we're dealing with a 10-ton chiller. They recently came out with a 5-ton version. So that would be a nice evolution, I think, to see it move into the home.

Larry Lemmons:
Progress has been made certainly here in the valley of the sun to employ solar technology. A challenge has always been the cost.

Joel Dickinson:
We have all of this free energy we can harvest with the sun. The trick is to figure out how to make it cost effective and we've been evolving over the last number of years towards that goal and I think we're really getting close.

Joel Dickinson:SRP engineer;

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