Editor's note: This is the second installment of a multiple part article chronicling the true geothermal district heating system at the Breitenbush Hot Springs Resort, Detroit, Ore.
The goal of Breitenbush is to live in harmony with Mother Earth, utilizing as many of her natural resources as possible while offering a semi-wilderness hot spring experience that has been enjoyed by Native North Americans for decades. The place has a serious soothing effect on your mind and body. There is something about soaking in an artesian fed hot spring, under a clear dark night sky, that puts things into perspective.
The resort is frequented by thousands of people each year who seek out these wonders of nature. It is the job of the staff of Breitenbush to make sure that their visitors get every opportunity to relax and enjoy these bounties of Mother Earth. The hard work of the full-time and part-time staff runs 24 hours per day, with very little visual impact to the attending guests. It kind of reminded me of visiting Disney Land. You know that there has to be all kinds of activities running in the background that can’t be seen or heard for the most part.
The resort has numerous "closed" periods for performing tasks that would otherwise interrupt the serenity of the setting. I was fortunate enough to be able to be on the land during one such closed period. This was by intent, so that my investigative activities would not disturb their paying guests and allowed me to go into the guest cabins and other buildings.
What I found surprised me. The distribution system consisted of a grid of underground piping that ran between two active geothermal wells and all of the buildings serviced by these wells. They have the north side of the river, which is the primarily residences of the employees of the resort, and the south side, which is primarily guest cabins, the main lodge and other convention buildings and health wellness buildings.
The underground district heating system piping comes from the two geothermal wells with an emergency interconnect capability that allows their maintenance operations people the ability to shut down one heat source for occasional servicing. One thing of real interest to me was the fact that they didn't have any known expansion tanks within the closed-loop portion of the heating systems. This was evident because the three horse power circulators that served the system could not establish a point of no pressure change, and were continually confused and unable to produce all positive pressures, which we all know is ideal.
When asked about this, I was told that they had never had any expansion tanks in the system because the system is essentially on all year, and distribution piping within the system is kept hot through the use of manual bypass valves on the far ends of the distribution system. Essentially, unless the system is shut down and drained for emergency or planned repairs, or modifications, it never really goes through any kind of big temperature fluctuations. And if they did have to go through a drain and refill, the pressure relief valves on the numerous domestic hot water storage tank/heat exchanger combinations relieved the excess build up of fluid due to expansion.
That opened my eyes to the fact, that this was not the normal heating system that I was familiar with, in that if I needed to work on the system, with a flip of the switch I could shut the heat source off. Such is not the case with an active geothermal system. Oh sure, you can shut off pumps and close valves, but you can’t turn off the heat. Plus, you've got to be prepared to deal with the heat that the source is going to generate, to the tune of 220ºF. Standing next to a heat source with this potential is quite humbling, and the thought of having an out of control heat source with this magnitude makes your sphincter do the mambo.
Early on, during our discussions of their systems' operation, and their goals as it pertained to efficiency, the thought had crossed my mind that I could possibly do an outdoor reset on the main distribution loops serving the buildings. That, it turns out, is a bad idea. In order to keep their artesian augmented, naturally occurring hot springs at a reasonable temperature, much of the excess heat from the well has to be dissipated, hence the main reason the distribution loops are maintained in a hot ready steady state, even during the non-heating seasons of the year. The mains are also kept hot because of the need for DHW production throughout and around the expansive facilities.
So, as you can see, working with a dynamic heat source as large and powerful as Mother Earth requires a completely different mind set as it pertains to operation of not only the heat source, but also the distribution systems.
Tune in next month as we continue to study this marvelous resource. Until then, happy hot tub hydronicing!
Mark Eatherton is a Denver-based hydronics contractor. He can be reached via e-mail at [email protected] or by phone at 303-936-7606.
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