Another Take At Zero-Energy Buildings: Optimum Energy’s Nathan Rothman (Part 3)

SM: What exactly was the technology that you licensed?

NR: Large buildings that are 100,000 square feet or greater have boilers in their basements that produce hot water, which is circulated around the building. There are radiators and fans that use the hot water to heat the air. That is how those buildings are heated. There are 110,000 buildings in the United States that are that size or larger.

On the cooling side, they have chillers which make cold water. That cold water is circulated throughout the building and absorbs the heat. The heat is discharged through what is called a cooling tower on the roof of a building. That is what those big boxes are on the roof of the building. After the heat is discharged, the water is sent back down to the chillers in the basement where it passes through tubs in a big vessel. A cold gas chills the water before it is pumped throughout the building again.

In a 30-story building there will be two chillers. They will each be 500 horsepower. The pumps that circulate the cold water and cooling tower fans add more load. All in all it, approaches 1,500 horsepower of electric motors operating the cooling system.

The heating system is very simple. It is 90% efficient. The cooling system is very inefficient. There are several cycles, and water must pass through the evaporating side and condensing side. That is why it takes 1,500 horsepower to run that system; this is almost the equivalent of a locomotive. In its simplest form, it is going on and off as the temperatures in the building cycle. That is a very inefficient way of running these systems.

Approximately 20 years ago, a device called either a variable frequency drive or a variable speed drive was developed. It allows adjustment of the speed of an electric motor. Before that speed was controlled by gears and pulleys. The device pulses the electric motor with current and controls the speed appropriately. There is a law in physics that says if you slow down an electric motor that is driving a fan or pump, you reduce the electric usage by a factor of three.

If I run an electric motor at 100% speed, then I use 100 units of electricity. If I run that same motor at 70% speed I will only use 36 units of electricity. There is a dramatic reduction in the use of electricity. Variable frequency drives have been around in the HVAC industry for eight years or so. The problem was buildings had two large 500 horsepower motors and then a bunch of 50 to 100 horsepower motors at cooling towers. The question is, how can they all operate together with maximum efficiency?

The people who make the chillers do not make the pumps. The people who make the cooling towers do not make the chillers. It is a very fragmented industry. Nobody took a comprehensive view of the cooling plant. As long as the building was getting cooled they were satisfied. Power was so cheap that it was irrelevant.

Now that energy has become more expensive, everybody is concerned. Our timing was very good. We started in 2005, when energy was just starting to creep up. We took a comprehensive view. Tom Hartman’s patents and algorithms come into play by taking that comprehensive view. Our technology is the band leader of cooling systems.

This segment is part 3 in the series : Another Take At Zero-Energy Buildings: Optimum Energy’s Nathan Rothman
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