index.php

 An inquisitive, perceptive, and innovative engineering approach by Falcon Engineering helped Royal Roads University avoid unnecessary construction costs, as well as disruptive work, in the design for a geoexchange ground coupling system for the Dogwood Auditorium.


The Project

A “geoexchange system” may sound complex, but it is really as simple as its name implies: exchanging “heat” from earth materials or groundwater below the earth’s surface with the building’s HVAC systems, so as to provide heating and cooling energy, all without consuming fossil fuels or adding to the building’s Carbon Emissions. Our blog, An Introduction To Geoexchange, gives an overview of geoexchange engineering systems.

Falcon’s Energy Engineering team has completed just such a project at the Dogwood Auditorium at Royal Roads University, near Victoria BC.

The Royal Roads Campus is situated at the base of a prominent escarpment slope. Areas on campus along the base of the slope have high water tables and, in some areas of the Royal Roads campus, footing interceptor drains are required to control shallow groundwater to protect buildings and infrastructure. Water intercepted by these drains throughout the year is collected and conveyed by pipeline as stormwater discharge. Several years ago, the campus irrigation system was outfitted to use water from the interceptor drains as the main source of water for grounds irrigation to make beneficial use of the intercepted water.

When a project arose to convert the swimming pool (originally built in the late 1950s for the former military college) to a new purpose, the Royal Roads planners wanted to ensure that reducing carbon emissions was an important component of the project plan and budget.

Royal Roads University selected Falcon’s Energy Engineering team, under a competitive RFP process, to examine the natural setting and propose a solution for an alternate energy system to be applied at the legacy building, repurposed as the Dogwood Auditorium.

The project to regenerate the building for learning and events space was opened in its new format in Spring 2021, including the geoexchange heating and cooling system. The system resulted in significantly reduced Greenhouse Gas (GHG) emissions for the Dogwood Auditorium, while providing the energy for comfort conditions throughout the year, with little reliance (peak heating) on fossil fuel energy.

From a Site Visit to Design of the Innovative Geoexchange System

Falcon was selected to design the new geoexchange ground heat exchange (GHX) system (HVAC design was already awarded to another firm), and in the summer and fall of 2019, conducted a thorough site-specific Geoexchange Suitability Assessment (GSA) to investigate the most suitable geoexchange options for the project site. The initial concept envisioned by Royal Roads University (RRU) included an open-loop water well geoexchange system, whereby groundwater would be pumped from one or more extraction wells from which the groundwater would be passed through a heat exchanger, and subsequently re-injected to the ground by one or more injection wells.

However, through the process of conducting the GSA, Falcon became aware of the presence of the significant drain water discharge. Exploratory investigations by Falcon of rushing water in manholes near the prospective Dogwood Auditorium led to the reveal of an existing, readily available energy source, already “plumbed” near the surface.

Falcon conducted further investigations and analysis to establish that the drainage water would be of sufficient flow quantity, and at a satisfactory temperature throughout a given year, before committing to the client that the drainage water would serve as a suitable and reliable ground source coupling for the geoexchange system.

Data from Environment Canada of seasonal climate norms over a period of approximately 30 years was critical to the analysis. Flow rates of the drainage water were measured over the spring and summer of 2019 and added to anecdotal information from the RRU Operators of the irrigation system. Together, these data sets were applied to a calculated “stress test” to ascertain the values of the drain water system as a source of energy to moderate indoor temperatures of the Dogwood Auditorium, as well as to ascertain the likely impacts of the “heat rejection” back into the drain water system during each of the four seasons. The combined analysis demonstrated that this drain water system could be relied upon as an appropriate energy source for heating and cooling the Dogwood Auditorium, and that heat rejection from the Dogwood Auditorium would not deleteriously affect the adjacent ocean water temperatures, to which the drain water from RRU flows.

Thus, Falcon was able to demonstrate the values of the proposed ground source coupling to the geoexchange system and was also able to demonstrate that the environmental impacts of using the ground source coupling (the drain water system) would not impose undesirable impacts (such as excessively warm temperatures) on the drain water or the ocean water.

With any type of retrofit or repurposing project, unexpected findings and conditions are prone to be discovered and this project was no exception. Although the intercepted groundwater-derived drain water had been used for many years by the irrigation system without any history of debris or sedimentation problems, new flows were recently added to the drain water system that included contributions from rooftop drainage. In many geographic locations, rooftop drainage would not pose significant problems; however, on the heavily treed RRU campus, rooftop drainage can be laden with organic debris. In this case, organic debris in the form of evergreen needles and other organics, entered the drain water system from the new sources and contributed to maintenance concerns for both the existing irrigation system and the new geoexchange system. A simple screen and diversion modification was implemented by the Project Civil Engineer in Fall 2021 and seems to be working effectively. Ongoing monitoring is warranted and perhaps additional modifications may be required.

An Energy Efficient Building System

The portion of the heating load served by ground source heat pumps for the Geoexchange System, employing energy derived from the flows of the drain water system existing on campus, results in a 98% reduction in emitted CO2e as compared to the “base case” of standard naturally aspirated boiler and standard air handling systems (commonly found in buildings of that age and utility).

Combined with the relatively low costs of drawing energy from the existing groundwater drainage system, when compared to employing a drilled well system and open or closed loop geoexchange system piping, the resultant system provided the client with:

  • a lower capital cost
  • very low energy consumption characteristics in operation
  • very low GHG emissions,
  • and comfortable conditions throughout the year.
construction of Dogwood Auditorium

A win for the client, a credit to the design engineers and installation contractors, and a credit to the institution (Royal Roads University) who commissioned the project.

Aligning with the Royal Roads University Climate Action Plan

The project to repurpose the former swimming pool at RRU into what is now known as the Dogwood Auditorium reflects the best in contemporary construction and facilities planning. As the Royal Roads University Climate Action Plan calls for significant GHG reductions by 2035, it was seen by University planners as an important aspect of the new use of this existing building that it would not add to the University’s GHG emissions, while simultaneously providing a much-needed events and learning space for the campus.

Consequently, as the geoexchange system delivers on the heating and cooling needs of the Dogwood Auditorium, it does not add CO2e liabilities for RRU, and provides modern ventilation and comfort conditions even when fully occupied by Convocation Ceremonies, University staff meetings, student study areas, and community events. 

From an Aged Facility to a State-of-the-Art Auditorium

Royal Roads University and Durwest Construction set out with a vision to repurpose an aged facility and transform it into a state-of-the art auditorium. The level of innovation and commitment to sustainable transformation is a remarkable and defining feature of the redevelopment project. Re-purposing of the drain water, that would otherwise have been wasted, into an energy source seemed to mesh well within the vision of this type of transformation. 

As a standard of practice at Falcon Engineering, we emphasize the importance for careful consideration of both the setting- and the building-specific features of a project, to thoroughly examine opportunities for development of a low carbon energy system. In the case of the geoexchange ground coupling at RRU Dogwood Auditorium, this standard of practice ensured that the opportunities inherent in the existing drain water system were recognized early in the investigation process, and subsequently led to an affordable and successful geoexchange system to serve the Dogwood Auditorium. Falcon Engineering feels honoured to have played a role on this team.

You can find out more about our Energy Engineering services here and more about our team.

If you have questions about our experience or the geoexchange work we do, get in contact by using our contact page.

Want to learn more about energy engineering? Check out some of our other blogs!

The adoption of newer and more efficient technologies is constantly changing. In the 20th century we saw this happen with oil and gas furnaces replacing coal, as they provided a cleaner and more efficient alternative for heating. Today, the transition to even cleaner heating system solutions is occurring. The demand for heat pumps, electric heaters, geoexchange and more, have increased substantially, with the aim to efficiently heat buildings while producing less carbon emissions. It’s important to understand how these new heating technologies work, and how they can benefit the right space.

Whether you are looking for heating systems in a home, public building, or industrial facility, in this blog we go through different heating system alternatives – and help build the understanding for future heating and cooling needs.

Integrated technology applications

Integrated technology applications combine energy applications in a way that leverages the benefits of different technologies (for example solar and geoexchange). It is important to consider how various energy technologies, such as HVAC systems, lighting, and envelope systems, will be integrated into the overall project. The key link in integrated technology is building design focused on energy use. This results in cost savings with strong energy optimization.

Solar PV on a roof

Air source heat pump systems

Heat pumps are the future of heating and cooling. Air pumps don’t burn fuel to heat a building but rather extract heat from the air and concentrate it for use within the building. Air source heat pumps are roughly 2 to 3 times more efficient than burning fossil fuels, such as oil or natural gas, to generate heat. 

Geoexchange heat pump systems

Geothermal heat pump systems

We broke down the concepts of geothermal heating before in a previous blog. However, to briefly explain the concept, geoexchange efficiently heats and cools buildings using energy extracted from the ground using heat pumps. What makes this heating system ideal are the results. In many applications, well-designed geoexchange systems can nearly or fully eliminate carbon emissions associated with building heating and cooling.

Geoexchange systems run on electricity and can replace your conventional heating system, avoiding the emissions that come from burning fuel.

Ground source heat pumps extract heat from the ground and are one of the most efficient ways to heat your home.

“In fact, they can reduce utility bills by 70 percent over conventional systems, and they’re extremely reliable, with in-ground components that can last 50 years” (Sense, 2020). While they do have a high installation cost, they are also incredibly reliable systems.

The team at Falcon Engineering was able to assist with mechanical design for Crawford Bay Elementary-Secondary School back in 2009.

This project included a ground source heat pump which provided extensive heat recovery opportunities. Our engineering team worked with this client to provide a long-term heating solution.

mechanical engineering project

Conclusion

At Falcon Engineering, we have the experience to give our clients low carbon energy strategies to help guide their decision-making today, for achieving compatibility with tomorrow’s expectations. Our engineering services allow us to evolve with changing technologies to give our clients the best heating system solutions.

Learn more about our previous heating system projects here.

Want to learn more about energy engineering? Check out some of our other blogs!

References:

https://blog.sense.com/how-to-choose-your-next-heating-system

https://www.thisoldhouse.com/heating-cooling/21014980/geothermal-heat-pump-how-it-works

What is Geoexchange?

To introduce this topic, let’s start off with an interesting fact: Anything with a temperature above absolute zero (-273°C) has heat energy in it. As well, anything warmer than absolute zero has stored energy. Geoexchange technology captures and uses stored heat from the ground for providing energy-efficient heating and cooling for buildings ranging from single family residential homes to the largest institutional and commercial buildings. What makes geothermal energy even more interesting, is that this isn’t new technology. The technology has existed for decades and has been improved, and adapted upon. With wise and thoughtful design adapted to specific site conditions, geoexchange systems can be cost-effective, and can be adapted for homes, commercial and institutional buildings, and industrial process applications.

Why is there a growing interest in Geoexchange? 

Geoexchange heating and cooling (also sometimes referred to as ground source heat pump technology, or geothermal heat pump technology) is a technology option often considered as a part of electrification strategies for decarbonizing heating loads. In many applications, well-designed geoexchange systems can eliminate, or nearly eliminate, carbon emissions associated with building heating and cooling. 

How does it work?

The geoexchange principle relies on a specific application of the refrigeration cycle for transferring heat from one place to another. By moving heat instead of converting chemical energy into heat (e.g. fossil fuel combustion), geoexchange systems can often provide space and/or process heating (and cooling) in a much more energy-efficient manner than conventional heating or cooling systems. Geoexchange heat pumps can extract energy from low-grade heat sources (at temperatures below 5°C) and “concentrate” the heat to a higher temperature for delivery to a heated environment. Hence, heat pumps can be coupled to a ground heat exchanger (often consisting of buried piping within the earth) so that the ground becomes the heat source for the system.

The energy-efficiency of a heat pump is dependent on the temperature of the source/sink that it is coupled with. In heating mode, the energy-efficiency increases as the source temperature increases. In cooling mode, the energy-efficiency increases as the rejection temperature decreases. Because the undisturbed earth temperature is warmer than the average winter air temperatures and cooler than average summer air temperatures, the ground makes for an attractive heat source for winter heating and heat sink for summer cooling.

Vernon Secondary School installing energy engineering

Geoexchange Harnesses Renewable Energy 

The ground energy harnessed by geoexchange systems is renewable energy. Most of the energy captured by geoexchange is solar energy absorbed by the earth’s crust while a smaller portion is core geothermal energy. In the geologically diverse western cordillera of BC, the core geothermal component varies from site to site and in some cases anomalously high geothermal gradients may cause the core geothermal component to be significant. Although electrical energy is required to drive the heat pumps, carefully designed geoexchange systems are capable of achieving coefficients of performance (COP) exceeding 3.5 in heating mode (COP is the ratio of the total heat delivered by the heat pumps relative to the electrical energy required to drive the heat pumps). At a COP of 3.5, 71% of the total heat delivered is renewable energy transferred from the ground and the remaining 29% is derived from grid electricity. Types of 

Ground Heat Exchangers (GHX) 

Ground heat exchangers (GHXs) can take many forms, but all forms belong to one of two broad categories:

  • Closed-loop GHX systems which rely on conductive heat transfer between the earth and a network of piping through which a heat transfer fluid is circulated in a closed-cycle. Examples of closed-loop GHX include vertical closed-loop borehole systems and horizontal trenched piping systems.
  • Open-loop GHX systems which rely on the actual transfer of groundwater or surface water through the geoexchange cycle.

The four most common types of GHX are:

  • Vertical borehole GHX – Closed-loop (V-GHX). This method involves drilling a network of boreholes that are each typically 50 to 250 m deep (depth often depending on site-specific constructability factors). Two pipes are placed in each borehole with a u-bend connection at the bottom and heat transfer fluid is circulated through the borehole network. This is the most versatile method and can be adapted to the widest range of settings. However, the vertical borehole GHX method is typically the most expensive option when other options are available.
  • Horizontal trenched GHX – Closed-loop (HT-GHX). This method involves installing heat exchange pipes in trenches that are typically 1.5 to 3.0 m deep (depending on climate and soil conditions). Without the depth dimension, the horizontal closed-loop method requires a much larger footprint area to generate the same heat exchange capacity as a drilled vertical borehole system. Consequently, horizontal systems are limited to applications where large open areas are available (such as for schools with large play fields or agricultural operations with large areas of surrounding cultivated land).
  • Horizontal directional-drilled GHX – Closed loop (HDD GHX). The horizontal directional-drilled (HDD) method involves installing heat exchange pipes in drilled horizontal boreholes that are typically 5 to 10 m below the ground surface. Because the boreholes are drilled below the surface, this method results in much less ground disturbance than the trenched method. As with the trenched horizontal systems, the horizontal closed-loop method requires a much larger footprint area to generate the same heat exchange capacity as a drilled vertical borehole system. The HDD method can be well- suited where upper soils consist of laterally continuous fine-grained (easily-drilled) soils (particularly when deeper soils are unsuitable for cost-effective vertical drilling), or where extensive surface disturbance would disfavour trenched methods.
  • Groundwater Production/Injection Well Pair – Open loop (GW-GHX). Groundwater open-loop systems typically move groundwater from a producing well (or wells) through a heat exchanger and then return the groundwater (at a lower temperature in heating mode or a higher temperature in cooling mode) to the aquifer by injection well(s). In certain settings, these systems can be very cost-effective where high rates of high-quality groundwater can be produced sustainably. However, appropriate site conditions for medium scale open-loop groundwater systems are relatively rare, and conditions suitable for large-scale open-loop groundwater systems are rarer still. Furthermore, these systems typically require more diligent attention to maintenance, incur higher maintenance costs than closed- loop systems (particularly if the groundwater is highly mineralized or is otherwise not of high quality), require careful highly site-specific design, and require a licensing process that involves consideration of affects to existing groundwater users in the area. Large GW-GHX systems may also require navigating an environmental assessment process often including groundwater flow and thermal simulation modelling if the rate of groundwater production is large (in British Columbia an environmental assessment is typically triggered for projects involving groundwater production exceeding 75 L/s).

Systems comprised of a network of vertical boreholes are the most common type of geoexchange system – but sometimes other types of systems are suited depending on site-specific setting. (Source: Natural Resources Canada)

Common Misconceptions

There is a common misconception that the temperature of the soil/rock surrounding a closed-loop GHX remains constant despite the transfer of heat in and out of the ground through the GHX. As a result, there is a widely-accepted perception that geoexchange systems always operate at a consistent performance level because they supposedly tap an “unlimited availability of heat at a constant ground temperature”. Unfortunately, this perception is false and misleading and often leads to inappropriate applications of geoexchange. In fact, the ongoing thermal interaction between the heat pump system and the closed-loop GHX causes the temperature of the soils that are thermally coupled with the GHX to fluctuate. The GHX temperature varies in response to the “rate” (power) and the cumulative “quantity” (energy) of heat extracted from (or rejected into) the earth and can be quite sensitive to the relative balance of the annual heating and cooling loads. Temperature fluctuations are damped as a function of site-specific soil thermal properties and the size and configuration of the GHX. As a general rule, the better the soil thermal properties, the bigger the GHX, and the more balanced the annual heating and cooling loads, then the more stable the GHX operating temperatures. 

Proper accounting for these relationships is important for selecting appropriate GHX option(s) and it is crucial for supporting effective and sustainable design of the selected option. 

Relative Balance of Heating and Cooling Loads 

Closed-loop type of geoexchange systems operate most effectively when they serve both heating and cooling loads. In cooling mode, the heat is transferred into the ground causing the soils in proximity to the GHX to warm and store heat. Then in the winter cooling mode the stored heat can often be re-captured from the ground for heating purposes. In this manner the heat is essentially “recycled” from season to season, resulting in considerably less strain on the GHX, and allows the GHX to behave more as a store and less as a source of heat.

installing a geoexchange system

With careful design, geoexchange systems can be designed to sustainably serve one-way heavily dominant heating loads. For closed-loop type of systems, bigger GHX systems are typically required to serve one-way loads (e.g., more boreholes or deeper boreholes), and the spacing between the boreholes needs to be significantly increased so that the GHX is in thermal connection with a much greater mass of soil from which to transfer heat. For open-loop type systems serving one-way loads, greater attention to the separation between extraction and return points is required.

Importance of the Options Analysis Step

The cost for constructing the GHX portion of geoexchange systems varies by a factor of nearly ten-fold per unit capacity. 

The large range is attributed to many factors including:

  • GHX type (different installation methods with widely varying cost).
  • Relative balance of heating loads (unbalanced loads require bigger GHX that are more expensive).
  • Site-specific soil and rock conditions (localized ground conditions can be challenging for drilling or trenching which can significantly escalate cost, and because geological and hydrogeological conditions vary more widely in BC than in other regions, this factor has a more prominent effect in BC than elsewhere).
  • Procurement processes (amount and type of information provided to bidders and the type of process used can significantly affect cost).

An objective evaluation of site-specific conditions and available site-specific options at an early stage in the planning process can help identify unique geoexchange opportunities (improving technical performance, reducing cost, or managing risk), and can help identify constraints or limitations that may impede suitability for geoexchange adoption.

What are geoexchange solutions best suited for?

Along with air-source heat pump systems, geoexchange heat pump systems will play a crucial and growing role in efforts to decarbonize building heating and cooling. Geoexchange is particularly suited in the following scenarios:

  • Colder climate locations where air-source heat pumps are unsuitable or less effective. Geoexchange can decarbonize heating in northern BC, such as Prince George and Dawson Creek.
  • Settings where the ground can be used to store rejected summer heat, or sources of waste heat, for uptake for winter heating.
  • Settings where unique cost effective opportunities for ground heat exchange are available.
  • Settings where silent outdoor operation is desired (in contrast with air-source heat pump systems that often generate considerable noise).

The Importance of a Thorough Design

While geoexchange heat pump systems aren’t particularly complex, they do require thoughtful and thorough design, and particular care in optimizing the integration of the geoexchange subsystems including:

1) Ground Heat Exchanger

2) Heat Pump Plant

3) Distribution System.

Heat pumps deliver heat differently than combustion systems and the design of the systems needs to take this into account. Falcon Engineering has developed a core expertise in optimizing heat pump performance based on careful monitoring of the performance of several dozen large institutional geoexchange heat pump systems we’ve designed. We’ve aggregated a lot of lessons learned expertise.

Case Study

In particular cases, such as the Canyon Falls Middle School in Kelowna, our team implemented geoexchange technology to heat and cool the school. The system consists of a network of 24 boreholes drilled deep into the underlying bedrock to a depth of 600 feet. Along with geoexchange, the school was equipped with solar PV panels, LED lighting, occupancy based controls, and a network automation system to reduce the energy use intensity of the school.

Canyon Falls Middle School in Kelowna

The net result is a near elimination of carbon emissions relating to the operation of this school. In this case, Falcon Engineering Ltd. provided mechanical, electrical, and energy system engineering services including energy modelling and geoexchange system design.

Conclusion

As a leader in green, energy efficient building systems, Falcon Engineering is well-suited to identify and implement low carbon energy solutions, including geoexchange where it is suitable, or identify other suitable low carbon alternatives for specific buildings in specific settings. At Falcon Engineering, our clients demand low carbon energy strategies to help guide their decision-making today, for achieving compatibility with tomorrow’s expectations. Reach out to us to speak with our highly qualified team of engineers, scientists and technical analysts about your geoexchange needs.

Find more information about our services here.

Want to learn more about energy engineering? Check out some of our other blogs!