Alderney 5 experimental seawater project cools municipal buildings in Halifax

summary

Halifax Regional Municipality needed to replace their obsolete and CFC polluting cooling system. The were approached by ENvironment Canada to test innovative low-carbon technology, aligning with their need to cut carbon emissions. The Alderney 5 district cooling project utilizes a seawater-based cooling system for a municipal building complex. The technology stores the winter-time cold water from the Halifax harbour with an innovative borehole field that stores “cold energy” for summertime use. The project provides enough cool air in the summer to meet demand.

Roles

The Halifax Regional Municipality (HRM) owns the Alderney 5 project.
The projected was funded through a variety of government channels and funding programs such as the Federation of Canadian Municipalities’ Green Municipal Fund; Sustainable Community Reserve; Environment Canada; Nova Scotia Department of Energy; NRCAN – Energy Innovators Program.
SNC-Lavalin (later known as HPES – High Performance Energy Systems) provided the mechanical and electrical engineering work for the first phase and was then taken over by the HRM’s in-house technical team.

Location

The ‘Alderney 5 Energy Project’ is comprised of five municipal buildings – Alderney Gate, Alderney Library, Old Dartmouth City Hall, Alderney Landing and the Dartmouth Ferry terminal, covering a total area of approximately 31,000 m2 on the Dartmouth waterfront in Nova Scotia.

The Challenge

As a result of the Montreal Protocol, ratified in 1989, many refrigerants and cooling technologies became obsolete, including the CFC-11 and HCFC-22 that was previously in use at the Alderney site. With growing need to adapt to changing regulations and impending costs, a district cooling system was considered to be the most practical and efficient solution.

The riskiest stage of the project was the inclusion of the geothermal borehole field which was proposed in order to ‘store’ cold energy during the winter months. This was a previously untested technology at this scale and if it succeeded, it would become the first commercial project using this technology.

As well, while the project progressed, the Halifax Regional Municipality took on the role of general contractor after the contract was cancelled.

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THE SOLUTION

New technology lines up with government planning

Halifax’s regional government had developed a corporate plan to reduce carbon emissions by 20% below 2002 levels by 2012 and their community Energy Plan called for using renewable energy sources of energy. When Environment Canada approached the region about participating in a pilot project to test new geothermal cooling technology, the approached lined up with their planning documents and need to change their cooling system

Keeping the public engaged and updated

To keep stakeholder and the public up to date on the project, the region disseminated information about the project through a regularly updated website. They also maintained a “Geo-Vault”, housing the pump, filters, and valves for the public to familiarize themselves with project and underlying low-carbon technology.

A strong team managed through adversity

A council sub-committee acted as a steering committee throughout the project’s development. To manage the project after a change in lead contractor, a well rounded team of highly qualified personnel, spanning across departments (technical, financial, and legal), effectively collaborated with federal departments with a greater depth of technical resources.

First commercial scale deployment of underground thermal energy storage

The Alderney 5 Energy Project used natural gas, efficiency strategies and geothermal technology. The project’s cooling technology provides cooling for the municipal building complex around the Dartmouth City Hall in Halifax, eliminating the use of refrigerant-based cooling technologies in the summer months. The project’s Underground Thermal Energy Storage (UTES) system is the first in the world to store cold energy. During the winter, titanium heat exchangers extract cold energy from the Halifax Harbour. This cold energy is then stored for seven months in a geothermal borehole field underneath the adjacent parking lot to be used to cool buildings in the summer months.

The borehole technology uses a new design wherein 100-120 borehole at 600 feet deep are found to be nearly 300% more efficient than traditional U-tube boreholes. This borehole design enables cold energy to be stored in the rock mass and used directly for air conditioning without the use of heat pumps.

In ‘charging mode’, cold seawater pumped through a heat exchanger chills a freshwater and glycol mixture. This is then pumped through the underground borehole field which captures the heat energy of the bedrock, lowering the temperature of the borehole field.

In the ‘discharging mode’, freshwater is pumped through the chilled bedrock where it is cooled. This chilled water is then used to provide for air cooling in the Alderney 5 buildings. Warmed freshwater is returned to the borehole field where heat energy is removed and water is again chilled for the next cycle.

Retrofits to increase energy efficiency

The project also involved the integration of three traditional retrofit technologies – installation of low flow aerators and automatic shut-off valves, installation of efficient lighting fixtures and switching the fuel for the heating system from conventional fuel oil to natural gas. These measures resulted in substantial cost savings as well as reduction in GHG emissions.

Natural Gas

Geothermal

The Results

Ten years on, the Alderney 5 project has experienced its share of bumps along the road. The new technology is servicing fewer buildings than originally planned, requires the use of backup chillers, and requires repairs than expected of the pumps located offshore.

The Stats

The stats were projected and are outdated. They may not reflect the current experience.

Eliminating the use of furnace oil (410,000 litres of furnace oil annually)
Eliminating the use of CFC based refrigerants (900 kg)
Reduction of GHG emissions (estimated – 900 tonnes of CO2 emissions annually)
Over the twenty year period, the Alderney 5 Energy Project, would save over $6,900,000.