Photo courtesy Associated Engineering.
Geoexchange and heat pump technology is long established, with the first systems developed and implemented in the 1950s. With increasing awareness, improved equipment and industry expertise, and the rising cost of energy in recent years, the technology has experienced a resurgence. It is estimated that there are now over 100,000 geoexchange systems installed in Canada, and in the past 10 years the industry has experienced double-digit growth in most markets across the country.
Geoexchange systems use a readily available source of renewable energy to heat and cool a building. This energy is essentially solar radiation stored within the upper crust of the earth, and it can be tapped wherever you have access to the earth, ground water, a lake, or the ocean.
Although some electricity is required to drive the heat pump and circulation pumps, well designed geoexchange systems can deliver 75% of the total heating energy from renewable energy stored in the ground. The systems are a proven and reliable solution to boost energy efficiency and reduce carbon emissions, and they have attracted significant attention.
Seems simple: needs design rigour
Although geoexchange technology appears simple, this is deceiving. It relies on the integration of mechanical components and has to adapt to complex site-specific earth and building thermodynamic processes.
The systems’ long-term viability and performance require a rigorous and thorough design approach based on science and judgment, quality construction by experienced trades, and a complete and detailed system commissioning.
Those working on a geoexchange project for the first time may be unaware of the complexities of geoexchange design and construction. A province like British Columbia has an extremely variable geography, climate and building demographics, which require that each project design is unique and site-specific. Thorough and expert information tailored to each region is needed to ensure that systems meet the needs and expectations of owners and proponents in terms of their specific environmental, social and financial benefit targets.
What can go wrong
A challenge in the current market is a lack of thorough and verifiable data on the performance of operating systems. While plenty of geo-exchange systems have operated without trouble for years, an unacceptable number of systems that we know of, or have heard of anecdotally, are underperforming. There are also systems that have had difficulties in the implementation.
The following examples illustrate situations that can arise:
• A care home developer receives a development permit that requires geoexchange technology to be included. The developer juggles complex competing design schedules, but the geoexchange system’s scope for design and construction is procured late in the building design when site preparation is already underway. The result is hurried design and construction, with little ability to optimize cost-effective design and performance criteria.
• A municipal hall is designed to incorporate a geoexchange system, and design concepts and budgets are developed without consulting a geoexchange engineer or completing an adequate site intrusive investigation. A drilling contract is awarded, and the contractor encounters challenging conditions for their equipment and submits a claim for extra fees. A dispute arises and building design and construction schedules are put at risk.
• A prime contractor for an institutional project acts as a design coordinator and separately subcontracts the geoexchange system’s engineering, drilling, heat pump installation, building mechanical, and controls components in an effort to control costs and use preferred service providers. The process results in a patchwork design with no whole-system design approach and the maintenance contractor is left struggling to operate the costly and complex system.
Guidelines to help
Given the variability and complexity of applying geoexchange technology in B.C., and recognizing the reported gap between expectations and performance for some geoexchange projects, there has been a call for more detailed B.C.-specific technical materials that will help ensure these situations are avoided.
Geoexchange BC has therefore recently published a series of guidelines to educate key players (developers, owners, coordinating professionals, construction managers, engineers, installers and commissioning teams) on the requirements of a successful geoexchange project. For more information, visit www.geoexchangebc.com
These guidelines also help establish a strong standard of practice for the industry going forward. Each guideline covers a separate topic and is focused on commercial-scale applications within B.C., although many of the concepts are applicable to smaller projects and other regions.
There are four guidelines in the current series:
• Part 1: Assessing Site Suitability and
• Ground Coupling Options
• Part 2: Design
• Part 3: Commissioning
• Part 4: Procurement
A User Guide is also included that summarizes the key content of each guideline, provides a flowchart and checklist format for guidance and record-keeping, and identifies topics within the guideline relevant to each key player on the project team.
The package comprises over 250 pages of detailed, purpose-written literature and documentation. It has collectively been written by 20+ active industry experts, with review and editing by over 40 industry review panelists. It has been directly funded and approved by government agencies at the municipal, provincial and national level, as well as by major provincial utilities. It is a unique resource in Canada, and likely in North America.
Quantifying systems’ performance
In the next two years GeoExchange BC will be completing a detailed performance evaluation study of geoexchange systems in place in a cross-section of building types across the province. The study will measure and quantify the systems’ performance, and document the implementation processes that contributed to the performance.
Studies and feedback so far have demonstrated that where a thorough and thoughtful process is taken towards geoexchange systems’ selection, design, construction, commissioning and operation, they deliver energy and cost savings that can exceed expectations. It is the hope of Geoexchange BC that by sharing the knowledge assembled within their guidelines and setting a standard for best practice, all future projects can be similarly successful.
Let GeoExchange BC’s message be clear — failure to adequately design, install, commission, and control a geoexchange system will result in significantly reduced performance and undo the business case for making the investment in geoexchange.cce
Geoexchange System Basics
A geoexchange system includes three primary components – a ground heat exchanger (GHX), a heat pump, and a building distribution system. A typical commercial-scale GHX installation involves drilling vertical boreholes to a depth that ranges from 50 m to 150 m, depending on ground conditions. Long lasting high-density polyethylene (HDPE) piping is inserted into these boreholes, which are then sealed with a clay-based grout to provide protection to sub-surface groundwater and ensure good heat transfer with the earth.
Once these pipes are connected together in closed-loop header arrangements, a freeze-protected solution is pumped throughout the piping network. By using a heat pump, the fluid can either extract energy from the earth for use in building heating, or reject excess heat from the building to the earth in order to provide building cooling.
Where site conditions and construction costs warrant, there are alternatives to the vertical drilled GHX: primarily horizontal or surface-water closed-loop ex
change, or groundwater “open-loop” exchange.
Ruben Arellano, P.Eng. is past chair and currently a director with GeoExchange BC, a not-for-profit organization dedicated to the education, promotion and responsible design and installation of geoexchange systems. He is also a district energy specialist with Associated Engineering in Burnaby, B.C.