Almost like free BTUs

Heat pumps can enhance your energy conservation efforts

By Russell L. Kratowicz, P.E., Executive Editor

Plant Services Magazine

Heat pumps move thermal energy from one place to another. If an industrial process needs warming, heat pumps can capture and concentrate low-grade heat present in some thermal sink (a process stream, ambient air, the ground or a body of water). Examples include space heating, process water heating, steam production, drying, evaporation and distillation.

They also can be configured for removing heat from a process and rejecting it to the sink. An example is chilling process water. The household refrigerator is a heat pump that removes energy from the air in an enclosed volume (the process) and rejects it to the air in the kitchen (the sink).

Heat pump operating cost is a function of temperatures, flows, utility cost and a few other variables, all of which are the purview of the plant professional. If the cost to operate the heat pump is less than the value of the thermal energy the unit moves, you could have a gold mine on your hands. Purchase the hardware, get beyond the payback and you’ll feel like the modern equivalent of old Midas himself. Perhaps you’ll even be rewarded with some of those Midas-like jingles for your own pocket.

That’s why I ask you to join me for a dive into the morass we call the Web in search of not gold, but practical, zero-cost, non-commercial, registration-free resources about heat pumps. Remember, we search the Web so you don't have to.

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Basics

Our esteemed National Renewable Energy Laboratory in Golden, Colo., offers “Introduction to geothermal heat pumps,” part of its online primer about clean energy basics. This is where to go if you want a good grasp of the main operating principles behind the technology. The material is written in language that anyone can understand and there are links to explanatory material. Point little Miss Mousie in the general direction of www.nrel.gov/clean_energy/geoheatpumps.html to begin exploring the topic for the month.

The Department of Energy's Federal Energy Management Program publishes “How to Buy an Energy-Efficient Commercial Heat Pump” in the form of an online document you can find at www.eere.energy.gov/femp/technologies/eep_comm_heatpumps.cfm. It provides an explanation of the various performance metrics, efficiency recommendations, a cost-effectiveness example and an online cost calculator.

Cozy houses

Everyone wants to be as snug as a bug in the proverbial rug when they’re inside the family castle. Our nearly universal access to central heat suggests that in one respect, even some of the poorest people in this country enjoy a standard of living exceeding that of any of the monarchs chronicled in the world’s history. Heat pumps represent one way to make it all possible. For basic info on residential heating, I direct you to “Heat Pumps,” a tutorial on electrical energy efficiency for homeowners, brought to you by the good folks at Energy Outlet, a group of three utility companies headquartered in Eugene, Ore. This bit of content can be found at http://energyoutlet.com/res/heatpump/.

The metrics

As you would expect, heat pumps have performance ratings, and the ratings for residential heat pumps are available online. In the cooling mode, a key metric is the seasonal energy efficiency rating, the same as for air conditioners. In the heating mode, the metric is the heating season performance factor. If you visit www.aceee.org/consumerguide/topcashp.htm, you’ll be rewarded with access to “Top-rated energy-efficient conventional (air-source) heat pumps,” which provides those numbers as well as links to other rating sources.

Techy info

The International Energy Agency, based in BorÃ¥s, Sweden, offers an international information service for heat pumping technologies, applications and markets. The site bills itself as “The world's leading information centre on heat pumps.” A boast like that deserves your scrutiny. Although it covers a lot of territory, the plant professional would probably be served best by exploring “About heat pumps,” found on the left side of the screen. This is where the organization posts its more technical information.

For example, you’ll learn about heat pump energy savings and carbon dioxide emissions reduction, the two main heat pump types, suitable heat sources, the main working fluids, using heat pumps in industry, case studies and heat pump performance. The latter category explains some of the commercially available performance metrics and how they compare to the ideal heat pump. Each case study lists contact information at the end so you can obtain further information from the project’s stakeholders.

It’s a good site, but the main shortcoming at www.heatpumpcentre.org/ [no hyphens] is that its pages are wider than normal and require you to scroll left and right as well as the expected up and down.

Geothermal units

The simplest heat pump exchanges thermal energy with ambient air, the temperature of which varies greatly during the year. It may be the simplest approach, but these temperature excursions affect the unit’s efficiency. On the other hand, ground-source and water-source heat pumps exchange energy with the soil or a nearby body of water. The advantage that a geothermal unit offers is more stable efficiency, which is related to the relatively constant temperature found below both the frost line and thermocline. Sending your mouse to www.eere.energy.gov/RE/geo_heat_pumps.html will return a page that can link you to material about water-source units as well as the two types of ground-sourced units. Also, there are links to documents that address the costs and offer comparisons with traditional electric and combustion heat sources.