February’s topic on Combined Heat and Power
(CHP) strategies generated a lot of energy (excuse the obvious pun) in the form of e-mails, for which I thank those of you who took the time. One e-mail, from Ben Kincaid of Indianapolis, reminded me that in our rush to embrace new ideas we sometimes forget that many “new” ideas aren’t really new, they’ve just been dormant, or perhaps not well publicized, waiting for the right time to be in vogue. Mr. Kincaid is one of the visionaries whose ideas and experience in co-generation were in need of a tipping point. With a little editing on my end, and Mr. Kincaid’s blessing, he writes:
“When I was a young designer in 1970, ‘Total Energy’ seemed to offer great improvements in the consumption of energy relative to the services produced. We all should know that central power generation hasn't really changed since the early 1900s. And, at its best, it can't be better than 33 percent efficient, not counting distribution losses. The obvious place to start improving efficiency, reducing emissions, and providing a stage for petrochemical fuels to have an extended life would begin here. It hasn't and with our economically driven logic, might not for quite some time.
The ‘Total Energy’ project I was involved with was without question a success. All goals in efficiency, capacity, and dependability were achieved and exceeded. The system was designed to grow to twice its original capacity. The project was a large apartment complex where the ‘Total Energy’ plant provided power, heat (HVAC & plumbing), and air conditioning for all the apartments. Then the energy crisis of 1973-74 came and went with it went ‘Total Energy.’
There is one concept that can help us in the future and it does not require the capital layout of a central CHP plant. Actually, I envision a company that specializes in installing CHPs among all the office building and strip office buildings you see around the bypasses of all major cities. If you do the math and are allowed to compete with the present suppliers of power, you can't miss.
In 1974, I attended a two-week seminar where several energy efficiency methods were presented, but the one that really caught my eye was ‘Heat Recovery.’ The manual, which I still have, had an introduction that indicated it was our patriotic duty as an ‘American’ HVAC engineer to do our part to reduce America's dependency on foreign oil.
When you stop and realize that 95 percent of all HVAC designs incorporate ‘free-cooling’ you begin to see the potential for properly applied heat recovery. After all, air-side ‘free-cooling’ is far from ‘free’ and drawing in cold air to absorb the internal heat of a building, only to exhaust it out the relief vent, should be called ‘Throwing Away Heat Cheaply’, not ‘free-cooling.’ Think about an infrared photo of these buildings on a cold day – that would surely get the owner’s attention!
Since 90 percent of water-side ‘free-cooling’ is already installed via the chilled water distribution system, it's a wonder why more engineers don't apply it. If 50 degree F water is distributed to the building for internal heating in winter and picks up sufficient heat to rise to 60 degrees F, then the engineer's job would be to reduce the water to 50 F and return it to absorb more internal building heat.
The first step to return the water to 50 F would be to circulate it through an outside air, pre-conditioning air handling unit. If you had a 0 F day, you could heat the outside air to 45 F and reduce the water temperature to 50 F or less. This would actually be ‘free-cooling’ relative to the water, and ‘free-heating’ relative to the air. We would already be ahead of the game and eliminating many large outside air intakes, relief vents, relief fans, large ducts and plenums, dampers and controls could reduce the cost of the system.
The next step would be to recover any remaining heat and use it to heat areas requiring heat, additional outside air preheat, domestic water heating, pool dehumidification, or even snow melting if excess heat is available. In summer, there are also certain needs for heat and there is abundant building heat available.
Finally, after all the heat that is needed is removed, a small plate and frame heat exchanger could be used to provide the remaining cooling required. This is referred to as water-side ‘free-cooling.’
Nine years ago, we developed a new chilled water distribution method at the University of Evansville. When we turned it on, it produced 40 percent more distributed capacity than in its previous 17 years. The increased capacity would be worth $300,000 in new chiller capacity. The pumps and controls cost $150,000. Therefore, the pay back was -2 years. This application has been accepted by the industry to a fairly high degree. They call it Variable Primary Flow (VPF). We call it Mod-Flow. The conversion is applicable to 90 percent of all installed systems around the world in the last 30 years.
But that’s not all. We've developed a new concept. It's called a Dedicated Heat Recovery Chiller (DHRC). This has extreme potential and should, I believe, be required by law in all hospitals and motels.”
So, the more things change, the more they stay the same and the more people like Mr. Kincaid can help us achieve clean, efficient indoor comfort goals. What do you think?