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Using Water for Heating and Cooling
by Steve Clark   

The head of the Department of Energy, Steven Chu, said the energy challenge facing us can be won by playing smarter. He used Wayne Gretzky, who didn't waste time chasing the puck but moved to where the puck was headed, as an analogy. In the building HVAC industry, it would be wise to do the same.

Learning from Others' Mistakes

A world of information is out there. For instance, the high energy costs in Europe for the past several decades have forced the building industry there to be energy efficient. They know from experience which systems and heating and cooling sources shine. Fancoils, heat pumps, high efficiency boilers and chillers, district heating and cooling, co-generation, active solar, radiant heating and cooling are all forms of hydronic systems. Virtually no packaged equipment or large central fan systems exist.


A vast majority of new commercial projects in Germany use hydronics. In the United States, the number is close to 6 percent. In Germany, more than 60 percent of cooled commercial buildings use radiant cooling. Here, it is less than 1 percent.

Like the flight of a puck leaving a hockey stick, it's possible to predict the energy consumption of a building before it is built. Sophisticated building energy modeling programs can help building owners make wiser decisions and save many times the investment in energy costs.

Using What We're Given Wisely

Human energy needs are small compared to what the earth has and is blessed with, but this in no way justifies wasteful use of energy. When resources are used, economic benefit needs to be maximized. For example, co-generation using fossil fuels gives electrical power and thermal energy.

The more flexible a building can be at changing sources of heat, the more efficient it can be. Similarly, if thermal energy can be stored until it is needed, additional savings result. This need for flexibility drives the design to a central heating plant versus distributed heating using natural gas or electricity.

Centralized heating and cooling plants offer the opportunity to use the cooling energy as the source for heating energy. This can be done using a heat pump and can be extremely efficient if the heating distribution temperature is kept low.

So the engineer needs to devise an engineered system “ a central plant that allows fuel flexibility, energy recovery and possibly thermal storage. This will likely result in a hybrid design, potentially including solar, some geothermal and even fossil fuel co-generation during peak conditions. It's also essential to consider part-load performance. The number of full-load operating hours can be as little as 1 percent of the annual hours. An hourly, full-year energy model is the only reliable method of optimizing all these options and trade-offs.

As German engineers figured out decades ago, hydronics is the clear winner for energy distribution. Hence the saying, "The new green is blue."

Steve Clark, president for Aquatherm North America, is a professional engineer who has worked as a development and applications engineer for the Trane Company and as an HVAC and energy engineer for consulting engineering companies, including his own firms, with an emphasis on building energy efficiency.


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