Geothermal

Ground Source Heat Pumps | Well Field Design | Geothermal MEP Design

MEP Design for Geothermal Systems

RWB Consulting Engineers designs geothermal systems that work. Geothermal ground-source heat pump (GSHP) systems require extra care in design. After all, you only have one shot to get this right. Luckily, we’ve done this before… many times. We have several geothermal system designs under our belt, so you can trust that we’ll get it right the first (and only) time. Geothermal is just one of our many areas of MEP expertise.

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Why Geothermal?

Geothermal systems can be a viable option for buildings with plenty of space on the property. Geothermal well fields can be installed underneath parking lots, athletic fields, or any other open area. A ‘geo system’ is best suited for mild climates that will require a comparable amount of cooling or heating. While Texas is not the optimal climate for these type systems, we have designed many successful geothermal projects in the Dallas/Fort Worth area.

However, geothermal isn’t the right choice for every building. The success of a geothermal design relies on the operation of the building (i.e. buildings that are occupied 24/7 may not be a good candidate), the soil conditions of the site, the water movement on the site, and the spacing and depth of the wells. The earth doesn’t have a uniform soil temperature and every building is not operated the same, so a geothermal test well will need to be completed. From there, our mechanical team at RWB can evaluate the best approach for your building and site.

If you are looking for a MEP consultant to help with your geothermal design, turn to the experienced geothermal designers at RWB. With more than ten years of experience in geothermal design, we are knowledgeable in designing this type of system.

Energy Efficiency

Various studies have shown that geothermal systems can sigificantly cut energy bills. Here’s why: on the hottest days of the year, most systems have to work their hardest to use that hot air for cooling purposes. On the other hand, the ground temperature deep below the surface is relatively stable no matter the season. So, properly designed geothermal systems can use less energy during the same time that other systems are consuming the most energy.

Safe and Clean

Geothermal systems use water-based fluids in the ground loops, and standard refrigerant like R-410A in the indoor loops. If you will utilize the geothermal system as your sole-source system for heating, you can avoid using natural gas, propane, or oil in your system. Some owners prefer the peace of mind of no combustion, flames or fumes. And, it eliminates the risk of carbon monoxide poisoning from a furnace.

Electricity-Based

In areas where utility pricing for electricity is favorable, a fully-electric HVAC system can be advantageous. However, utility rates are often complex with varying costs depending on demand. A review of your specific utility rates, coupled with the operation of your facility and historical energy usage indices we have on various building types will give you what you need to make an informed decision. RWB is well-versed in evaluating utility cost information and comparing geothermal system energy and maintenance costs to similar system types.

Incentives

Because of the high efficiency of geothermal systems, building owners can often qualify for incentives from utility companies or from the government. For example, a geothermal heat pump system qualifies for 10% tax credit under the Business Energy Investment Tax Credit (ITC).

Certified in Geothermal Design

Need real geothermal experience? RWB has Certified GeoExchange Designers (CGD) on our team.

Distributed vs. Centralized Geothermal Systems

What is the difference between a distributed and centralized geothermal system?

The main difference lies in the number, size and location of pumps used to push water through the piping system. Both systems circulate water through the well field.

Distributed Systems

In a distributed system, each thermal zone is served by a ground source heat pump that conditions the respective space or spaces served. These pumps circulate fluid through the heat pump and out to the well field and back. Depending on the length and size of piping used these smaller pumps may need to have two (2) pumps placed in series to be able to overcome the pressure drop in the system. These are generally smaller fractional horsepower water sealed pumps. This generally results in a significant number of small inefficient pumps. In this system the heat pumps and pumps are cycled in response to load. Multiple smaller pumps circulate water through a well field and it is much more difficult to balance these systems precisely.

Centralized Systems

In a centralized system, larger, and a significantly smaller number, of more traditional pumps are located in a central mechanical room which then circulate fluid throughout the building, through heat pumps and through the well fields. These pumps are generally arranged in pairs for redundancy and served with variable frequency drive. These larger pumps are much more efficient and are further improved in efficiency via being variable speed. Heat pumps in this arrangement have two position solenoid valves to facilitate variable system flow. In this system the heat pumps are cycled in response to space load. These systems are much easier to balance.

Why does pump location matter in a geothermal system?

Geothermal systems are naturally highly-efficient. However, pumping power can significantly impact the overall efficiency of a geothermal, or ground source heat pump, system.

Comparison of Distributed and Central Geothermal Design
	Distributed Geothermal System	Centralized Geothermal System
Pump Locations	Small pumps in each space.	Large variable-speed pumps in a central mechanical room.
Pump Operation	Operates only when zone heat pump compressor is energized.	Operates anytime the building requires conditioning, typically 24/7.
Well Field Pipe Routing	PIping from the well field travels from well field directly to zone units.	Piping from the well field travels from well field, through a central mechanical room, and then is pumped to zones.

Which is better: distributed or centralized geothermal?

Both design types have their pros and cons.

The main considerations for distributed vs. geothermal systems include:

Efficiency. A centralized geothermal system can utilize larger pumps with much higher efficiency than the small pumps located at individual heat pumps.
Control Preference. Centralized systems offer greater system-level operational control. On the other hand, a decentralized system utilizes more straightforward controls.
Maintenance. Maintenance is different for the two systems. In distributed systems, maintenance personnel can replace the smaller pumps, and service equipment in indivual space without turning off the entire system. Centralized systems require more highly-trained technicians to service and maintain.
Construction cost. A centralized pumping system will typically have a higher first cost. Centralized systems also require building floor space for a mechanical pumping room.

The design approach depends on the goals of the project.

At RWB, we carefully consider the needs and desires of the owner from budget to maintenance. If you need a team with expertise in geothermal design, contact us today.

Having problems with your geothermal system? We can help.

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Common Geothermal Problems

If a geothermal system isn’t operating correctly, it’s crucial to resolve the problem sooner rather than later.

Since the earth below is being used as a heat exchange medium, a geothermal system operation problem could cause irreversible damage. If a well field becomes saturated such that the water temperature coming out of the well field elevates significantly each day beyond the initial design temperatures then the efficiency of the system becomes no better than air cooled systems. To return to normal requires not using the well field for extended periods of time which is not practical or reasonable. Thus, well field sizing is critical to maintaining long term system efficiencies.

With many years experience in geothermal design, RWB Consulting Engineers has been called in to help troubleshoot and fix poorly operating geothermal systems. When we consult on a geothermal project, we always begin by reviewing original calculations and design drawings. This way, we can understand the design intent of the original designer. Next, we gather operational data and seek out the anomalies of the system. Our team then compares what we see on a project with the successful geothermal designs we have completed elsewhere. Applying our many years of geothermal experience, we identify and help correct the problems found in faulty geothermal systems.

The most common geothermal problems include:

The bore field is the wrong size.
The system water flow is lower than expected.
The system’s water pressure is too low.
The temperature of the water is too low or high.
Valves or pumps were not appropriately sequenced.
The number of wells is unusually low relative to the size and type of building served.

Of course, ongoing maintenance is key to a geothermal system that operates smoothly and efficiently. But many times, the problem with a geothermal system isn’t a result of improper care.

RWB Consulting Engineers are adept at finding and solving problems with geothermal systems. If your system is operating correctly, give us a call today.

Graphic image of a four-story building with geothermal well field system

Image Source: ACHR News

Clients

Geothermal Systems

Aledo Independent School District
Denton Independent School District
Eagle Mountain Saginaw Independent School District
Keller Independent School District
Mesquite Independent School District
Midlothian Independent School District

Geothermal projects require the right engineering team. At RWB, we have mastered the art of a proper geo design. In fact, we’ve even been brought in to help correct the geothermal designs of others. Have a need for an MEP team with geothermal experience? Contact us.