County looks at AC units
The Warren County Building and Grounds Committee recently heard recommendations from TVA representative Amer Moghrabi on the most cost efficient method of replacing the air conditioning system in the county courthouse. The June 4 meeting gave committee members a look at a report prepared by Moghrabi that offered 3 different systems for their consideration. A closed loop geothermal system, water source heat pumps, similar to the existing system, and air source heat pumps.
The report indicated that the system currently in place is 25 years old and is at the end of its useful operating life. The report also noted that the maintenance costs are rising for the old system and the cooling tower, in particular, has major problems and needs to be replaced.
Moghrabi told the committee that the courthouse building itself appears to be in good shape judging by the size of the building and the utility costs.
“The courthouse is running at under $1.00 per square foot,” he said, “Compared to other courthouses, most of them go over $1.10 per square foot, so the building itself is very efficient.”
Of the three systems proposed in the report, the geothermal method had the lowest annual operating cost, but the highest installation cost. The system consists of hydronic heat pumps that are connected to clusters of bore-holes, and does not require a boiler, cooling tower, chiller or any other auxiliary heating/cooling components external to the hydronic loop.
A geothermal system would cost $180,000 to install and would have an annual operating cost of $8,441. The drawback to this system would be finding the space to drill the holes. Moghrabi noted that some parking space around the courthouse would have to be given up to make room for the bore-holes. Also, even with the lower annual operating cost, the extra expense of installing the system would require 26 years for the system to pay for itself.
The least expensive system to install, according to the report, is the air source heat pump system. But again, space around the courthouse became a limitation, since several units would have to be placed outdoors, not only taking up already limited space, but presenting somewhat of an eyesore to the public.
A comparison of the air source heat pump and water source heat pump systems showed that even though the air source heat pump installation would be cheaper, due to a higher annual operating cost, the water source system would recover the difference in cost in a little over 6 years.
The air source heat pump system would cost the county $124,392 to install and $12,178 per year to operate, while the water source heat pump would cost $137,540 to install, and $10,069 per year to operate.
The committee ultimately decided to stay with the water source heat pump system due to the fact that it would require the least amount of disruption to install since it would be very similar to the current system, and over the estimated 25 year life of the system would prove more economical to operate.