Apr 112014

Thirty years ago I started selling Geothermal Heat Pumps, when I worked at Baker Wholesale in Fargo. We had one customer who was a well driller and he expanded his business into Geothermal. My father helped him design bigger and bigger systems. The bigger the facility the better Geothermal looks. In addition to the greater efficiency, there is also greater flexibility in a multi-zone facility.

In the April 2014 issue of Energy Systems Magazine, Daniel Cohen writes about the Ping Tom Memorial Park Fieldhouse. The field house runs its geothermal heat pumps off of 16) 650-ft-deep vertical wells. This is five times deeper than the well fields we would normally design, but I’m sure they had land use issues so going deep was easier than the drilling more wells.

Ping Tom Memorial Fieldhouse

Chicago’s Ping Tom Memorial Fieldhouse
photo by James Steinkamp/Steinkamp Photography

Environmental Systems Design (ESD) selected Geothermal units for their high energy efficiency ratio (EER) and coefficient of performance (COP). They are estimating a COP of 4 making this heating system 400% more efficient than straight resistant electric heat. In addition they connected modular heat pumps in each zone throughout the field house.

“The heat pumps are independently controlled which allows for energy to be shared and distributed from zone to zone.”

Downsides to Geothermal: it is slightly more expensive to install, but the long term energy profile and operation cost savings makes it the perfect energy source for buildings large and small. Geothermal systems need land to drill the well field, but once it’s in you can use the land for anything you want.

I also like how ESD used CO2 sensors to modulate ventilation airflow based on occupancy. By using VAVs and controlling the ventilation load, the building can retain much of the heat that other buildings vent outside. Add in the Economizer and Energy Recovery system, this building should be inexpensive to operate.

Mar 052014
Spring Point Ledge Light is a sparkplug lighthouse in South Portland, Maine that marks a dangerous obstruction on the west side of the main shipping channel into Portland Harbor. It is now adjacent to the campus of Southern Maine Community College.  The lighthouse was constructed in 1897 by the government after seven steamship companies stated that many of their vessels ran aground on Spring Point Ledge.

Spring Point Ledge Light is a sparkplug lighthouse constructed in 1897, adjacent to the campus of Southern Maine Community College.
photo by Paul VanDerWerf (Flickr)

I’m not sure it’s possible to be further from seawater than in Fargo, North Dakota. That said I found this article by Rob Klinedinst and David Reinheimer, using a Geothermal heat pump with seawater, fascinating. The authors explain why the Southern Maine Community College (SMCC) in South Portland, Maine decided to go with geothermal, and the issues using seawater rather than a closed loop with a glycol solution. I was reminded of my early HVAC years: the first geothermal jobs we work on at Baker Wholesale were open loop systems. We were using Friedrich heat pumps on some large residences, where they had access to active aquifers. This was somewhat rare, so it didn’t take long until we were only designing close loop systems using Command Aire and Econar heat pumps.

The issues using sea water are corrosion and the temperature range of Casco Bay:

Initial roadblocks to using seawater were to find equipment that could efficiently handle the wide temperature ranges in Casco Bay and the corrosiveness of salt water. Only one heat pump model was found with a heating water temperature range of 14°F to 113 ° F, and this was coupled with a system used in the maritime industry — a cupronickel underwater ‘ship-keel cooler’ heat exchanger — that is highly resistant to saltwater corrosion. On ships, the heat exchanger is used to reject heat, but here, it is used to both extract and reject heat from/to the sea.

Rob and David (Harriman’s Higher Education Design Studio) searched the world looking for solutions that would let them take advantage of the sea. They found seawater pumps in Japan, filters and strainers across the country in California, titanium plate-and-frame heat exchanger, and insulated piping systems. All while working with the EPA to get approval. I would have given up before working with the EPA- that could not have been a good experience. The SMCC had a deadline to renovate the Lighthouse Building. The EPA was talking about studies and field testing. HHEDS decide to use a heat exchanger and keep the sea water in the bay.

The cupronickel heat exchangers are located under a nearby dock and positioned three feet below low tide. An uninsulated pipe loops between the heat exchanger and the building. Running the pipes under the ground (an added geothermal source) eliminated the cost of insulated piping. The pipe is filled with 50% food-grade propylene/glycol, with inline pumps moving the liquid at 75 gpm.

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