In the world of sustainable design, electrical systems have gained celebrity status.
In fact, many of us use some form of renewable electric technology in our daily lives – a rooftop solar array, electric or semi-electric vehicle, or even something as simple as solar outdoor patio lighting. Show of hands??? (Yeah...us too.)
But the use of sustainability in mechanical design is also worth considering. In particular, geothermal systems offer a number of both short and long-term benefits for both the environment - and the bottom line. Not a new technology by any means (we’ve been designing them for decades), geothermal is becoming part of the standard conversation among HVAC options in building design.
In this edition of Plains Talk, we’ll dive into exactly how these systems work, including the pros and cons of the investment, operation, and maintenance. We’ll also share a few examples of how they’ve been successfully used by our clients to reduce their carbon footprint (and monthly utility bills).
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The hybrid geothermal system at the new SDARNG AASF Readiness Center uses a well field system to meet all cooling needs, and the heating needs 95 percent of the time. |
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Military Mechanical Sustainability |
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South Dakota Army National Guard
Geothermal Projects
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The South Dakota Army National Guard has always sought to create buildings that are easy to operate, efficient, and environmentally friendly.
In 2008, West Plains Engineering had the opportunity to respond to an early effort to incorporate an energy- efficient geothermal system for the SDARNG during the design of the new Readiness Center in Mobridge, SD. A life cycle cost analysis determined that, while a ground-source heat pump meant higher upfront capital costs, the long-term costs for heating and cooling would be reduced enough to create a strong return on the investment
The experience made believers out of the SDARNG, and WPE has since utilized geothermal systems in several other Guard projects.
The mechanical design for the new $14.4 million Barracks & Classroom Building at Camp Rapid involved a hybrid geothermal system with multiple heat pumps and air-to-air heat exchangers. Hybrid means it uses a geothermal well field system to meet all cooling needs, as well as the heating needs 95 percent of the time. A small boiler system is used to supplement the heating side of the well field system, which allows reduced installation costs by reducing the number of wells, while maintaining the efficiency of a predominantly geothermal system. This project was certified LEED Gold and continues to operate smoothly more than a decade after being installed.
Most recently, we completed design and construction on the new 58,700 square foot Army Aviation Support Facility Readiness Center at Rapid City Regional Airport. The mechanical system for this building is again hybrid geothermal and is gaining notice from SDARNG facilities personnel for its performance. The Owner did a comparison of energy efficiency and cost per square foot to an existing readiness center on the eastern side of the State and discovered the AASF building had a 24 percent better energy efficient rating (EUI), and cost 20 percent less per square foot. In short, AASF is notably more efficient than the other building.
Our work to deliver high performance geothermal systems to the Guard continues today, as we use our knowledge to evaluate and design improvements to existing ground-source heat pump systems, as well as involve them in new building design.
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Dave Riemenschneider is a Mechanical Designer in our Rapid City office who has spent more than 20 years supporting the SDARNG. He has designed geothermal systems at multiple Guard sites across the State.
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Getting In At Ground Level |
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Geothermal/Water Source Heat Pump Systems |
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Geothermal heat pumps have many advantages because of their lower cooling and heating costs, lower exterior noise, and sustainable technology. They can be used in all types of projects in the public and private sectors, and work in the same manner as a basic heat pump (absorbing heat from an exterior source and rejecting it indoors at a higher temperature, or the reverse for cooling).
The difference is that, where a basic heat pump absorbs heat from the air, geothermal heat pumps absorb it from water that is heated in the ground. Ground temperatures tend to be relatively constant at 50-55 degrees F, as compared to air temperatures which can vary widely. This makes a geothermal system more consistent, and in some cases, a better option than air source heat pumps.
The advantages for a geothermal system are many. They yield lower costs in terms of both heating and cooling, and in general, a geothermal heat pump will have a lower heating cost than many other systems available. However, the initial investment in geothermal is typically higher, so a cost savings analysis must be completed to assure the functional savings offset the upfront cost.
Geothermal systems also typically use smaller heat pump sizes for each area, which allows temperature control zones to match the building design closely, and maintenance to be carried out zone-by-zone. It also means smaller mechanical rooms in the overall building footprint, as heat pumps can be installed in a ceiling space above the corridor, or in small adjacent closets to the areas being served. What’s more, there is no above-ground outdoor equipment to create a visual or noise distraction.
Of course, there are also some disadvantages to geothermal systems. As was mentioned, the initial investment for the well field is higher than other heat pump systems. Additionally, each zone has a heat pump with a refrigerant system, which must be distributed throughout a building. Facilities and maintenance personnel must be trained on the system and equipment locations to perform routine maintenance work above the ceiling as opposed to at ground-level as with other systems.
The four types of geothermal applications to be considered also all have their advantages and disadvantages and should ultimately be selected based on the project site conditions.
Vertical wells are generally used on commercial projects where large ground coupled heat exchangers are required. In this scenario, tubing is inserted into a series of wells, which are traditionally located under parking, athletic fields, landscaping, or a slab on grade building. With this option, a test well or thermal conductivity test is recommended to assure the well field will be adequately sized.
Horizontal loops can be either a long tube or what is known as a slinky coil. These options take up more square footage than vertical wells, but may offer a lower upfront cost, and are typically considered for projects that involve a lot of site work or fill.
The pond loop system utilizes coils of tubing submerged in pond water as the heat exchangers. This option can be very low cost if the landscaping plan includes ponds which are a minimum of 12 feet deep to prevent freezing.
Finally, an open (or pump and dump) system can be a cost-effective heat exchanger, but usually requires approval from the Department of Energy and Natural Resources for both the pump and dump sides. Additionally, a secondary heat exchanger is recommended to protect the heat pumps from poor ground water quality, and the environment from contamination through the building equipment.
One additional option to consider is the use of a hybrid geothermal system. In this design, the ground coupled heat exchanger can be sized either for the heating load or the cooling load only to keep costs down, while utilizing an alternate heating or cooling system to adequately condition the space in both modes. However, these systems must be designed carefully. When misapplied, they can use more energy than even a conventional system.
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Authored collaboratively by WPE Mechanical Engineering team.
Illustration courtesy EPA.gov.
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Sutton Bay Golf Course & Resort |
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Sutton Bay Golf Course and Resort was created as an upscale outdoor recreational complex on Lake Oahe in central South Dakota. With a rustic main lodge, 18-hole golf course, and access to some of the best hunting and fishing in the region – it caters to outdoor sports enthusiasts. Individual sleeping accommodations are spread out across the ridge overlooking the Missouri River – creating even more space and privacy for guests to enjoy the countryside.
While ideal for those looking to get-away, this rural setting presented several design challenges, one of which involved the HVAC system. Remote areas like this don’t have access to natural gas, or require impractical LP gas storage requirements, and offer only single-phase power. These limitations make many traditional HVAC systems ill-advised at best, or impossible, leaving the owner in search of a better option. For Sutton Bay, that option was a geothermal heat pump system.
Individual well fields were developed for each building, connected to heat pump systems. Each is small enough to use the available single-phase electrical power, while also providing the necessary heating and cooling for the units, as well as the main lodge, without needing additional fuel sources.
While requiring a higher upfront cost during construction, the use of the geothermal wells yielded several benefits, not the least of which was the ability to use a resource readily available on site as a fuel source. Other benefits include a lower operating cost, zone-by-zone maintenance, better efficiency during the cold South Dakota winters, and no above-ground outdoor equipment to tarnish the beauty of the resort.
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Marty Christensen, P.E. is a Principal Mechanical Engineer and Building Services Division Manager for West Plains Engineering who has designed geothermal systems for clients across South Dakota and Iowa during his 28 year career.
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Geothermal Systems for Schools |
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School budgets are lean, and growing leaner all the time. While the initial investment in a building or system upgrade might be approved in any given budget cycle, the ongoing cost to operate and maintain those improvements is certainly on the minds of administrators and facilities personnel.
Particularly in rural areas, relying purely on electric or Liquid Propane (Lp) gas as a utility resource is expensive and can create uncertainty as markets react to inflation. Without the availability of natural gas or possibly 3-phase power, many rural facilities are forced to rely on Lp, fuel oil, and single-phase power to serve their HVAC system needs. To combat this, and respect those lean O&M budgets, some districts have opted to instead incorporate sustainable geothermal systems to limit dependence on alternate, non-renewable resources.
To date, WPE has worked with nine different school districts across the region to add ground source heat pump systems to both new and existing facilities.
Of these, about half of been on new construction, with Owners making the decision to incorporate geothermal and other sustainable features into new, modern spaces. One such project was the design of the new 58,000 square foot Enemy Swim Day School in Waubay, SD. The district committed to a fully geothermal system for complete heating and air conditioning throughout the facility. Geothermal heat pumps for each temperature control zone are served by a closed loop ground coupled heat exchanger to supply heating and cooling to all locations.
Other districts we’ve supported wanted to convert existing HVAC systems to geothermal to increase efficiency and decrease their operating costs. In 2015, Flandreau High School in Flandreau, SD moved forward with a $3 million upgrade of the building’s aging HVAC system. Our team designed the replacement of the school’s central heating and cooling plant with a hybrid geothermal system. This system included a 121 geothermal well field adjacent to the building, as well as gas-fired hot water boilers and pumping equipment. Notably, this project was phased over two summers to limit the disruption to student activities and building accessibility.
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Our K-12 School Geothermal Systems |
Bonesteel-Fairfax School Addition – Bonesteel, SD
Central Community Schools – Leon, IA
Custer High School – Custer, SD
Elkton School Geothermal Conversion – Elkton, SD
Enemy Swim Day School – Waubay, SD
Flandreau High School HVAC Upgrade – Flandreau, SD
Montrose School Addition – Montrose, SD
Sundance Elementary – Sundance, WY
Terra Sancta Elementary Upgrade – Rapid City, SD
Wall K-12 School – Wall, SD
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West Plains Engineering News |
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As much as we love talking about our projects, we also really enjoying hearing about them! Check out some of our work that's been featured by news and social sites recently. |
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SDSU Aviation Program Hangar
Brookings, SD
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Block 5 Mixed-Use Development
Rapid City, SD
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Glenrock Town Square
Glenrock, WY
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An Office That Plays Together... |
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Our Sioux Falls team got together with their families to ring in Spring properly with some fun at Thunder Road Family Park this month! Who knew ax-wielding could be a team-building activity!? Probably depends on what target you're picturing...🤔
Thanks for the hospitality Thunder Road - the place still looks great and we had a blast!
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Kevin Groves celebrated 15 years with WPE in March!
Kevin is an Electrical Engineer in our Power Division with more than 25 years of experience in the utility engineering field. Since joining WPE, he has worked with rural utility service-funded cooperatives, public power districts, and investor-owned utilities on more than 250 projects in 9 states.
(Good thing he has his pilot's license!)
Congratulations Kevin!
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Join us in welcoming Dylan Vaughan to the West Plains Engineering team!
Dylan is a graduate of Southeast Technical Institute, and is the newest CAD Technician in our Sioux Falls office.
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Last Fall, our marketing director Kelli spent a weekend at a training course to get her motorcycle license. During introductions, the nice fellow behind her mentioned he was an electrical engineering student at SD Mines.
Fast forward a few months...and meet the newest intern in our Rapid City office - Chris Mentele! Chris is finishing up his studies at Mines while supporting our electrical team and we're thrilled to have him. (PS - they both passed the course. 🏍)
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Rapid City, SD | Sioux Falls, SD | Casper, WY | Cedar Rapids, IA |
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