My previous post ended after a heat recovery system was added to an ice arena, reducing the facility's energy costs by 50%.
I had followed the traditional process of doing an energy audit to identify ECMs (capital projects) and a detailed study to estimate costs and savings. With the estimated ROI acceptable to the owner, construction documents were prepared; bids were taken; and a contractor was selected to make the modifications and start up the new systems. The modified systems worked exactly the way I had designed them to. The utility costs were cut by 50%, as I had estimated. I was thrilled. In theory, the arena’s future was secure.
Fast-forward 10 years. I had started my own business and was serving as energy manager for a number of facilities. I got a call from Chuck, the director of the parks and recreation department for the town in which the ice arena was located. He told me that all of the savings were gone; the 50% energy savings from the new cooling tower and heat recovery system were gone. The rink was down to a six-month operation. The annual utility costs had risen to the point that the arena's continued existence was again in doubt.
The humidity was out of control. The beautiful wood ceiling was wet, stained, and turning green. Drips from the ceiling were making stalagmites on the ice. The contractor with whom they had been working couldn’t fix it. Could I help?
I put together a proposal to install a monitoring system at my expense to help diagnose the causes of the problems. If I could solve the problems and lower the operating costs through no-cost or low-cost changes in operation alone, I would do so for a percentage of the actual documented savings each month. When I presented it to the park board, the president asked, “If we don’t save anything, we don’t owe you anything? Right?” “That’s right,” I said. He responded, “I’d like to have a deal like that every day.”
Starting the next day, I began to spend as much time as I could in the facility looking at all of the energy systems. There were four rooftop units: one for dehumidification and three for air conditioning for periods when the ice was gone and the facility used for other functions in the summer. All four were running 24 hours a day. When I opened the access doors, I could see that the air-conditioning coils were completely encased in ice. In one unit, the 100 kW electric resistance heater that had been disabled when the heat recovery system was installed had been reconnected and was running continuously.
As soon as the monitoring system was operational, we could watch the operation and energy consumption of each piece of equipment in real time, 24/7. It allowed us to diagnose the causes of the problems and begin to change the operation to optimize the entire system.
With all of the cooling coils encased in ice, no humidity was being removed. And with running all four units 24/7, more was being added from the bypass air that the units were pulling in from the typical hot, humid Indiana summer.
The key to solving the rink’s problem was to continuously pass the humid air over cold coils that were above freezing but below the air’s dew point temperature. We shut off the three air conditioning units and modified the controls of the dehumidifying unit to run the first stage at part load, about 5 tons. The 100 kW electric heater was shut off and the controls for the heat recovery system set to dump the waste heat into the rink to keep the air temperature at 55. The ice surface more than kept the arena cool.
A stream of water started to run out of the drain of the dehumidification unit. It was starting to pull moisture from the rink air. By morning, the humidity had dropped from the mid-60s to 48%. The dripping had stopped and the boards were already starting to dry out. In a couple of days it was back to almost where it had been 10 years before. No electric heat was running and the compressor load of the rooftop units had fallen from 200 horsepower to less than 10.
The project reduced the energy costs by 67% and received recognition from the Indiana governor as well as a U.S. Energy Department Award for Energy Innovation.
Operation is the key
To put it in simple terms, what I learned in the Air Force about planes also applies to buildings. To fly a plane, a pilot must have actual real-time data presented in a clear and easy-to-understand format – cockpit gauges. These same truths apply to buildings. No matter how sophisticated the facility and energy systems, the operators – not the energy audits, benchmarking, capital improvements, and computer models – are the difference between success and failure.