Deep Water Cooling

Levi Waldron
Published September 19, 2006

Case Summary

Deep water cooling involves using naturally cold water as a heat sink in a heat exchange system, thereby eliminating the need for conventional air conditioning. We compare deep water cooling systems in Halifax, Nova Scotia and Toronto, Ontario, and find that this technology has significant ecological benefits and long-term economic benefits. This technology requires that a client with a large cooling need is situated near a deep, cold body of water, and payback times vary depending on the site. Diffusion is hindered by the low cost of energy. The City of Toronto's approach, in which many buildings are serviced at once while piggybacking onto existing water piping and pumping capacity, can deliver cost savings on a shorter time span. Other locations in which heavy air conditioning users are located next to deep, cold water bodies could use this technology to encourage sustainable building.

Sustainable Development Characteristics

In many areas of the world including North America, air conditioning imposes a significant load on local electrical systems. Air conditioning is required even in temperate areas, as technologies such as lighting and electronic equipment produce significant indoor waste heat that must be vented to the outdoors. Cooling can be particularly troublesome as it is thermodynamically more difficult than heating and demand is intermittent; air conditioning demand can trigger summer brownouts and voltage drops on hot summer afternoons. Air conditioning currently consumes 18 percent of US electrical output (Cox, 2006); any technologies that can considerably lower the energy demand of air conditioning will create a significant drop in electrical use and mitigate the associated environmental concerns of greenhouse gas emissions and local air pollution. 

Conventional air conditioning functions by transferring heat from the air to a chilled medium, and then uses a compressor, motor, and refrigerant to transfer the heat from the chiller medium to the outdoors. If it is warmer outside than inside, heat must be pushed “uphill”, a very energy intensive operation. Significant energy savings can be realized if heat can instead be transferred to a mass of cooler material with a high capacity for absorbing heat, such as water, eliminating the need for a compressor-based cooling cycle. Water is not only a good heat sink, it also has an unusual relation between its density and its temperature. Like most substances, water becomes denser as it cools, but unlike most substances it reaches a maximum density at 3.9 degrees Celsius. As a result, in winter, cold water on the surfaces of oceans and lakes cools and sinks through the warmer water below. In summer, the warm surface layers float on top of the cooler water below, as it is less dense. A layer of perpetually cold water is created below a certain depth, known as the hypolimnion.

Over the years, there have been many suggestions on how to utilize this cold water; for an exploration of some of these suggestions, see (Lennard, 1995). One of the simplest applications, however, involves pumping hypolimnion water to the surface and using it as a heat sink. Hypolimnion water would be pumped from the water body and into a heat exchange unit where it comes into contact with a closed cooling loop. The heat exchanger takes the place of the traditional “chiller” or air conditioner.

Energy savings of up to 90% over conventional air conditioning can be achieved, depending on how the system operates. The system requires only the energy to run the pumps and the fans that blow air over the cooling loops. As conventional air conditioning units are no longer needed, the need for ozone harming chemicals such as CFCs would be eliminated.

Though the impact of deep water cooling is generally positive, some concerns have been raised that, if overused, the cold water source could experience “heat pollution”, which would negatively affect habitat and species composition. In the oceans, such effects might occur at the local level, but the amount of heat involved is too small to have a large scale effect. Lakes are another matter. A study of Lake Ontario estimated that up to 20,000m3/s of water could be withdrawn from the lake and used for cooling without changing its physical properties (Boyce et al, 1993). For the Great Lakes, the maximum draw amount is very large. The maximum amount will be lower for smaller lakes, however, and must be taken into account in discussions on the sustainability of deep water cooling using lake water. The projects discussed followed established procedure for construction in coastal area, but long-term effects might not yet be known.

The opportunities in Canada for expanding deep water cooling are quite large. Both Halifax and Toronto could greatly increase their use of this technology without creating a serious environmental hazard. Other cities that could take advantage of this technology include Victoria, Vancouver, Prince Rupert, Hamilton, Yellowknife, Kingston, and St. Johns. As well, there are hundreds of smaller centres located next to deep bodies of cold water that could utilize this form of cooling. One of the theoretical barriers to future expansion is what Gregory Unruh calls “carbon lock-in” (2000), as energy technologies have co-evolved to require carbon-based fuel and their return-on-investment increasingly favours large scale technologies and discourages the diffusion of non-carbon options, even if economically sound.

Critical Success Factors

Success in both of the study cases hinged upon the private-public partnership model. This model provided the means to overcome the high up-front costs associated with this technology.

In the City of Toronto case study, what really pushed the project forward was the pairing of deep water cooling and deeper water intakes for the drinking water supply. In effect, two major projects were combined into one, a good use of holistic planning processes that differed quite a bit from more traditional planning processes where different infrastructure needs are considered separately. Enwave’s Kevin Loughborough reported that this is the first such combination of uses with this technology. Toronto’s success was also supported by the establishment of Enwave as a “middleman”. Individual developers didn’t have to install the infrastructure, they just had to make the choice to hook into the cooling network. The Toronto project succeeded as it had support from individuals in government and in business. The Purdy’s Wharf project went forward because the developer was willing to take a risk on fairly new technology. The projects' “champions” worked together to move their projects over various hurdles.

Community Contact Information

Enwave can be contacted through their press office at; the corporation is interested in developing other deep water cooling projects. Purdy’s Wharf is a private development.

What Worked?

Each project achieved its goal to significantly lower energy use. Economies of scale seem to be applicable here as well; larger projects might be more practical as a bigger cooling load can be displaced with a similar initial infrastructure layout. Each building that hooks onto the Enwave system lowers the cost per displaced kWh. The larger and newer project in Toronto, which continues to expand, has attracted more attention partly due to its location in a city experiencing significant smog problems and electricity shortages. The Purdy’s Wharf project, however, demonstrates that, in certain situations, deep water cooling technology can also work successfully on a smaller scale.

What Didn’t Work?

The Purdy’s Wharf project did not create a widespread adoption of the technology even though it is considered a successful project. This probably was due to the low cost of energy at the time of the project, a lack of comparable projects, and as it was one of the first in the world. Also, a developer wanting to mimic the Purdy’s Wharf project would have to start from scratch as the infrastructure has capacity for only the one development. One could say that deep water cooling has now hit a “critical mass” of sorts with several large projects in the planning phase, including projects in Hawaii and the Persian Gulf. Kevin Loughborough says the main factor in a successful deep water cooling project is geography. Key ingredients for successful projects are a high density cooling cluster located near a renewable cooling resource.” (Loughborough, per. comm.)

Financial Costs and Funding Sources

Purdy’s Wharf

The Purdy’s Wharf project was funded jointly as a demonstration project by the development company, JW Lindsay Enterprises Limited, and the federal government. Reports of the costs vary, but there is a general agreement that the cooling system paid for itself in a little over two years. Currently, the cooling system saves the complex over $100,000 in energy costs and maintenance costs. The largest expense is the pumping cost, plus the minor expense of copper anodes.

Toronto Deep Lake Water Cooling

The Toronto deep lake water cooling project was a major project with initial expenditures near the $200 million range (Canadian Press, 2003). Capital costs continue as the urban pipeline network expands. The project was a public-private partnership:  $33 million was funded by the City of Toronto’s pipe repair fund (Moloney, 2004), the federal government provided low-interest loans, and Toronto Hydro provided incentives to companies to hook their buildings up to the system in order to overcome the high initial capital cost. Kevin Loughburough of Enwave commented on the up-front costs:

“The pay back on the project requires a patient investor. It can be compared to a hydroelectric dam project in that it is capital intensive at the front end, but costs very little to operate over the long-term. The return on the project is competitive with other investments.” (Loughborough, per. comm.)

Research Analysis

This case study involved interviews and a literature search. It reveals that deep water cooling projects deliver impressive energy savings, but that initial investment is high and serves as a barrier to development. The case studies suggest that large-scale installations of this technology are better positioned to overcome the inertia of the high start-up cost and high payback time. An intermediate agency that bears the infrastructure costs and the initial risk can be useful in encouraging developers to use the technology. Sites with year-round access to deep water cooling might be preferable, and support for start-up costs is a major factor in the success of these projects. 

Detailed Background Case Description

This case study involved a background literature search and the investigation of two deep water cooling projects in Canada. The first project is the Purdy’s Wharf project on the waterfront of Halifax, Nova Scotia, which was constructed in 1986 and expanded in 1989. The second project is the Enwave Corporation’s Toronto Deep Lake Water Cooling Project, which began to provide cooling to buildings in 2004 and continues to expand.

The two projects are both public-private partnerships, but represent vastly different scales of application of the technology. The cooling media is also different. Purdy’s Wharf draws upon seawater and Toronto’s project uses fresh water.

Purdy’s Wharf

The Purdy’s Wharf office complex sits on the waterfront of Halifax, and buildings extend out over the harbour on pilings. Cold seawater is drawn from the bottom of the harbour through a pipe to a titanium heat exchanger in the basement of the complex where the closed loop of water, cooled by the sea water, is then pumped to each floor of the building where fans blow air over the cooling pipes to cool the air. The seawater is returned to the harbour floor. The project was jointly funded by the Government of Canada and the building’s developer, and was intended to serve as a demonstration of the technology. The project was constructed from 1983 to 1989 and consists of an 18-story tower, a 22-story tower, and a four-story retail centre. The total area cooled by the system is 65,000 sq. meters.



Purdy's Wharf Deep Water Chiller

The Purdy's Wharf Deep Water Chiller

Purdy’s Wharf required innovative technologies in order to mitigate the corrosive power of seawater. Piping is corrosion-resistant polyvinyl and polystyrene. The pumps are made of stainless steel.  One of the challenges to this project was to control marine growth. Initially, chlorine was used to prevent marine growth in the system, but this was both costly and potentially environmentally damaging. The chlorine system was replaced by cathodic protection provided by copper plates.

To provide proper cooling, the water temperature must be below ten degrees Celsius. The intake for the pumping system is located less than two hundred meters offshore at a depth of 18 meters where conditions are appropriate for cooling for ten and a half months a year. Purdy’s Wharf operates conventional chillers in the late summer when harbour temperatures are too high. Mapping of the harbour water temperature column was provided by the Bedford Institute of Oceanography and the Fisheries and Oceans Research Lab.

Toronto Deep Lake Water Cooling

The Enwave Corporation’s deep lake water cooling project is a much larger project than the Purdy’s Wharf initiative. Pipes extend five kilometers into Lake Ontario and draw water from a depth of 83 meters to the John Street pumping station where heat exchangers cool Enwave’s closed cooling loop that snakes through downtown Toronto. Lake water, slightly warmed, then goes on to supply Toronto with drinking water. This sharing of drinking and cooling water saves pumping water out of the lake twice, and the new deeper water intake solved the problem of algae blooms tainting Toronto’s water in the summer. The idea of providing cooling to Toronto using lake water had been considered at various times, but the project began in earnest in 2002 (Deverell, 2002). As of June 2006, 46 buildings were signed onto the system of which 27 were already connected (City of Toronto, 2006). As the system nears capacity, energy savings will be 85 million kWh, for a CO2 reduction of 79,000 tonnes annually, or the equivalent of 15,800 cars. The total cooling load will be 3,200,000 square meters, or fifty times the area of the Purdy’s Wharf complex. 61% of this capacity has been sold. (City of Toronto, 2006). There is some discussion to expand the system once capacity is reached. Energy savings are about 90%, and as the required cold water is available year-round, the need for supplementary chilling is eliminated. The Toronto project is jointly-owned:  57% by the municipal pension fund and 43% by the City of Toronto, and is thus an example of a public-private partnership.

Strategic Questions

  1. Does the outfall of warm water cause ecological damage in a Halifax-style project?

  2. What mechanisms could best encourage this sort of project? An end to energy subsidies, a carbon tax, grants, or further public-private partnerships?

  3. Would more demonstrations projects help to speed the diffusion of innovative infrastructure choices?

Other Resources

Deep Water Source Cooling: An Untapped Resource

Resources and References

Boyce, F, Hamblin, P, Harvey, L, Scherzer, W, & R. McCrimmon. 1993. 'Response of the Thermal Structure of Lake Ontario to Deep Cooling Water Withdrawals and to Global Warming.' Journal of Great Lakes Research 19(3) 603-616. 

Candian Press, 2003. “Lake Water to Cool Downtown” Toronto Star. Feb 28, E11.

City of Toronto “Deep Lake Water Cooling and the City

Cox, Stan 2006. Air Conditioning: Our Cross to Bear. AlterNet.

Deverell, J. 2002. “Enwave Launches Deep-Lake Cooling Project” Toronto Star. June 20, B02.

Lennard, D. 1995. 'The Viability and Best Locations for Ocean Thermal Energy Conversion Systems Around the World.' Renewable Energy 6(3) 359-365.

Molony, P. 2004. “Pipe Funds Diverted” Toronto Star, May 24, B02.

Unruh, G. 2000. 'Understanding Carbon Lock-in.' Energy Policy 28, 817-830.



Other than this wonderful website of course, would you know where to get information about such innovative technologies and their success if you were a community member, councilor or municipal officer wanting to get such projects looked at in your own communities?

One of the barriers is, after all, a lack of knowledge and lack of experience in what can be done.

Knowledge - Where to go for more information

For municipalities and government interested in renewable energy options, and specifically deep water cooling, a good place to look would be Enwave's website. Enwave is the private partner in both the Toronto and Halifax deep water cooling systems. Enwave can be found at

For individuals wanting to learn about deep water cooling in general, both National Geographic and the Scientific American have online articles featuring this topic - and

Natural Resources Canada also has some very interesting information on deep water cooling available at

If a community is specifically interested in the use of ocean water, Natural Resources Canada discusses this in detail at This information is entitled "Seawater Cooling System for Buildings".

All of this information is only a "click away" for many Canadians. For a number of communities in northern British Columbia, however, high speed internet is not yet a reality.

For those without internet access, government publications can be obtained by phoning toll-free to Ottawa. Similarily, Enwave can be contacted by contacting its main office in Toronto.

For magazine publications, I believe that interested parties might have to head to a library. Fortunately, most libraries provide computers for internet access - and I think that librarians would be happy to assist anyone new to computer technology.

Knowledge - Where to go for more Information

I found the Economist article on Deep Water cooling to be very interesting and informative. If focuses on the specifics of Toronto's experience and highlights how many buildings are serviced and other fringe benefits. A number of buildings on the system are putting the cooling units on the roof. This in turn free's up space for other things.

This particular article might be useful for someone wanting to get more technical specifics on deep water cooling in an applied setting. A Cool Concept. June 7, 2007. Retrieved from

Alternatively, I found it interesting to learn that there are currently seawater cooling systems in Tahiti, Curacao, Korea, Malta, the Cape Verde Islands, Haiti and Mauritius. I didn't realize how long this technology has been in use in other regions of the world. In 1986, the Natural Energy Laboratory of Hawaii Authority in Hawaii began to successfully use seawater air-conditioning. Their program has since expanded to other neighbouring buildings. This and other useful information can be found in;

Cummins, Joe. The Blue Revolution: Air Condition and Energy from Deep Waters of Lakes and Oceans. Retrieved from

Stakeholder Engagement

Tanji and Lise, all those websites are very insightful. However, if I were a community member, councilor or municipal officer, I would be confused about the information because I would have no technical background to understand what it really means. I think the project manager should educate his stakeholders and engage them to ensure that they understand the language and the scale of the proposed project. Transparency and clear language is important to ensure everyone understands what the scope of the project and how it will effect him or her personally. After reading these websites regarding deep-water technology, I am a little confused myself with the technical terminology used in some of the articles.
To help remove some of the barriers (i.e. lack of knowledge), I would suggest that the project manager and/or lead individual should organize a stakeholder meeting right from the start and continue throughout the proposed project to educate and inform them using the following techniques:

1. Use the language of the stakeholder group.
2. Select the appropriate engagement approach. This may be focus groups, individual or small group interviews, surveys, formal referrals, key-person meetings, advisory councils or some other. The approach chosen should reflect the engagement objectives, stakeholder capacity, cost and time constraints, and whether qualitative or quantitative information is required (Industry Canada website, 2008).
3. Consider getting outside help. A professional facilitator or consultant can help with the details of the engagement plan.
4. Find shared values amongst the members of the stakeholder group
5. Ensure there is transparency and trust
There are other ways to ensure common understanding and knowledge, for example, the company can hold informal 'open houses' and multi-stakeholder workshops during the planning phases of major new projects.

More on Stakeholder Engagement.........

I thought of a little more regarding stakeholder engagement. It would be important to map and prioritize stakeholders according to likely influence, impact on the project, and credibility to engage. Engage directly with key stakeholders to understand their interest in the project, any ground rules and expectations. This enables to formulate and facilitate an appropriate engagement – in individual meetings and/or roundtables. This helps with strategy development or options needed towards the project and ensures the loop is closed with the involved stakeholders in a way that builds their trust and confidence.

To answer question # 3 of the case study. ‘Would more demonstrations projects help to speed the diffusion of innovative infrastructure choices?’ I would agree that more demonstrations of these types of projects would help the speed of innovative infrastructure choices. However, in respect to the deep-well project, Tanji brought up the fact this type of technology goes back to 1986. So in other words, there were a lot of demonstrations of the success of this type of technology. As well as there was no real evidence that this type of infrastructure has caused adverse effects on the environment. It has been in use for a long time.


Tanji states: I guess my point here is that I am wondering how deep water cooling projects really get off the ground in the absence of strong, progressive Municipal leadership?

How crucial do you think individual and group leadership is in sustainable development? If sustainable community development is to become the norm then surely it has to become normal and not reliant on such leadership? How do you think this could be encouraged?

Leadership & Community Engagement

As Tanji and Leah have pointed out, leadership is important to get a project such as the deep water cooling project off the ground. It would be especially challenging if the governing body who should be responsible for supporting such an initiative does not want to lead the process. I have learned that leadership does not have to come from the top, as David Bell stated that leadership can come from the side. A good leader can influence decisions through social capital. Another good point made was that the community has to be engaged. This can be instilled by achieving creativity and discovering concrete solutions. Leah’s right when she says that you need leadership to drive the process forward. And it is becoming more clear to me that once people realize a common goal and are engaged by enhancing their capacity to contribute then a movement can gain its own inertia.

I see where you are going

I see where you are going with this Jody - lateral leadership and the importance of it. (Unrelated, but I noticed during our World Cafe the other night with the MALT team that the woman who 'led' the session and was the primary speaker and appeared to be directing things was really not the 'leader' of the group. Based on my conversations with the team members and seeing how they interacted with each other and got each table talking and into a dialogue, you could easily see that Beverly was leading - laterally).
By building bridging and vertical capital, the idea of a deep water cooling project could become a reality. I think that to get a project of this size off the ground, there would need to be a great deal of energy and planning put into the development of nodes and networking in the early stages so as to gain momentum and support for the project.

Leadership for sustainable development

I think this a very good question and goes back to the idea of how we embed sustainability concepts through knowledge - and I don't mean that in the tradional sense where we aquire knowledge through forums (although that is possible)or by taking courses. The goal of municipal governments, especially if they are seeking re-election is to give the voters what they want, and particularly if there are public/private partnerships which would lessen the blow to taxpayers. Where there is a value added component (sustainable development)to an infrastructure improvement, the ability of govenment to achieve buy in from community members is enhanced. Additionally, because of their standing in the governance structure, both federally and provincially, municipal governments are in very good strategic positions to capitalize on various subsidizes and grants to address this very issue.

At this point, I am not convinced that a "sustainability mantra" is maintsream thinking. The ususal suspects appear at council meetings and support sustainability initiatives. An even larger group want to understand what it all means and what it will cost them as takpayers.

I think that a number of sucessful sustainability initiaves within communities will allay some of the suspicions related to s.d, change the culture, and sustainability will become an expection rather than a value-added component.

Leadership in Sustainable Development

I think group leadership is crucial in sustainable development to drive a vision, direction and specific action, which should be mainly coming from the public sector. There needs to be facilitator to build upon the strengths and credibility with the stakeholders to engage partners involved with the opportunities sustainable development presents. I believe even when sustainable community development is normal you still need group leadership and a facilitator to drive the process forward. People need accountability and responsibility to put things into action. However, there will be less time spent on educating stakeholders on the concept of sustainable community and more time spent on the actual process itself. This can be encouraged by educating people on the successful experiences to achieve sustainable communities and how the actual process of getting to an agreement on the specific action. There is a lot of useful information about leadership and networking in the book below.

Gilchrist, A. (2004) The Well-Connected Community: A Networking Approach to Community Development. Bristol, Polity Press.

Community Engagement - Part 2

Jody - I agree with you, the success of these projects (well, Toronto anyways) was likely due large in part to the collaboration between government and private industry.

I am trying to consider these projects in more of a local context, for example, my hometown of Nelson. Nelson is situated on the shores of the deep Kootenay Lake and has the characteristics required for a deep water cooling project. Nelson recently revealed its Master Water Management Plan. The plan calls for a 7$ million dollar expansion to develop a new water source and reservoir to meet 'growing water demands.' Regrettably, the plan does not consider any demand-side water management practices. I guess my point here is that I am wondering how deep water cooling projects really get off the ground in the absence of strong, progressive Municipal leadership? In Nelson, visionary and environmentally conscious leadership (in government) is lacking, as evidenced by the lack of discussion regarding water metering or any form of demand-side management (among other things). On the ladder of engagement, Nelson sits at about the Therapy or Informing level regarding water and energy resources.

This case study thoroughly explored the mechanics of deep water cooling projects, but I am missing the link between how these types of projects go through the process of being great ideas to actual projects. For a project of this to occur in smaller communities, who would have to be the 'champion' to get it going in the absence of environmentally conscious political leadership? What key players and stakeholders would have to be at the table? Governance is an important aspect that should be considered. As Jody highlighted, connecting deep water cooling to the provision of drinking water supplies would be an integral part of getting support. For deep water cooling projects to succeed in smaller cities, community involvement would have to move from consultation up the chain through placation and partnership and on to some form of delegated or citizen control.

Buy-in & Economic Viability

Hello All:
Great comments. In regards to the buy in for Toronto deep-lake-water cooling project was an easy project to pass. The city council approved the investment into the project and footed some of the bill. This helped a great deal to get it to go through. However, the actual customers who use the system benefited from the savings of having the project. Jody and Tanji are right that most of the collaboration was mainly with the government and private industries. I found the meeting minutes from City of Toronto Council and Committees regarding the feasibility of the project. Here is the link: They stated that a pre-design study and environmental assessment was done to allow for public input and confirm project viability while maintaining the security and integrity of the water supply system. I am not sure to what degree the public input was. For large business, the project was economic benefit. Customer savings through Deep Lake Water Cooling were demonstrated after May 2006 when Hudson's Bay Company [HBC], Canada's oldest diversified general merchandise retailer, switched to Enwave's system for its Toronto office tower. HBC energy savings are projected at 3,571,200-kW per year, the equivalent of powering more than 350 homes (Toronto Hydro-Electric System Ltd, 2006). That certainty makes the project appealing for industries just with the savings from switching to this system. For industry buy-in, they have to be large enough to have the economic benefits. If the businesses were too small, the initial investment would not pay off for a long time. The capital costs for deep-well water cooling (fresh or sea water) are between $2 to $5 million, which includes the pipeline, heat exchangers, and chilled water distribution system. The payback period for these systems ranged between 5 and 6 years for a large business and 9 to 17 years for the businesses with the smallest air conditioning loading (Van Ryzin & Leraand, 1992). The main factors that influence the economic viability of a deep-water cooling system are (Van Ryzin & Leraand, 1992):
 The distance to the water source
 The size of the air continuing system
 The environmental conditions such as temperature of the water, climate, and wave or currents etc. For a place like Halifax – the local seafloor bathymetry needs to be assessed.
The mechanisms to encourage this type of project would be mainly economic benefits for the initial buy-in from industries and businesses because it directly benefits them.

Van Ryzin, J. & Leraand, T. (1992). Air conditioning with deep seawater: a cost-effective alternative. Ocean Resources 2000. Retrieved on February 18, 2008 from:

Toronto Hydro-Electric System Ltd. (2006). Toronto Hydro-Electric System Limited Conservation and Demand Management 2005 Annual Report. Ontario Energy Board File No. RP-2004-0203/EB-2004-0485.

Save your work

I STRONGLY encourage you to copy whatever you type into these comment boxes before you hit 'post comment.' I just spent a long period of time putting my thoughs down, went to hit 'post', and lost it all - no idea where it went. Subject was 'Community Engagment' in case it pops up elsewhere.
This is frustrating to say the least.

Sustainable Limits

At first glance this new infrastructure can be regarded as sustainable, since the impact to the environment seems very minor initially. Temperature is really the only element that may initially be affected. Maybe compared to other cooling technologies this is a better option, but everyone or everything might not agree; especially the one fish that needs the temperature to remain consistent to spawn.

Over time another issue that might arise and cause this type of technology to be unsustainable is the overuse of the water resources (eg. lake). A lake can only handle so many water withdrawls before the lake ecosystem will be affected.

This idea brings up another issue of what are the limits in sustainability. Do we worry about the one fish that might be affected or do we focus on protecting 80% of the population? (This question was inspired by a second year student who had a question about threshold limits for development. At what point is a new development project not approved?) Very good question (tough thesis topic though) Often decision makers base their decision on just one issue at a time. It’s just recently that they are starting to consider the cumulative impacts of developments. Who sets the limit to development? We all equally have the right to use the land.


Lise and team,

Interesting comment Lise, you have stumped me. This idea didn't cross my mind at all while reading the case study. I will check out the link you provided.

Having only read this case study once, the first thing that jumped out at me was the issue of buy-in. How does a community get buy-in for an energy savings project whose intial investment is very high while other low cost energy is available? How do you create that sense of urgency for change?


Great comments from all, and a good question about "buy-in". It takes me back to economics where we looked at bio-thermal energy and did cost projections to determine how long it would take before we recovered our initial investment and realized savings.

I fully agree that having public/private partnerships is a good idea.

I think that in terms of deep water cooling, and in keeping with our discussions on sustainable community deelopment, large projects like this would be good candidates for deliberative community forums (this topic is covered in one of our pre-readings - but my link didn't work.) Try this link

I think that the science is important in anticipating and addressing community concerns related to ecosystem impacts, but I also think that there will likely be a large segment of the population interested in energy savings - as the cost of energy is soaring.

Sorry - but I'm not fully conversant with this web interaction - and did want to go back to re-read Leah's comments. I'll wait to hear back from you all.


Tanji, you brought up another good point about getting buy-in for a project with such a high initial investment. It was interesting to see that the Toronto case really “pushed the project forward” by tying the project to an essential need, drinking water. By linking the project to something that is a human need, it seemed like it was easier to get support for the project.

It also sounded like champions within government and business supported the project and were able to move through barriers. If you can get collaboration from a number of organizations that can potentially benefit from the project then it is more likely that it will succeed.

Halifax project - ecological damage from warm water outfall?

More info regarding this question can be found at "Oceans in Distress" which discusses commercial exploitation of our oceans, and cautions us regarding potential impacts on fragile deep-sea communities.

When looking at ocean exploitation and Halifax, I would think that discharge might be timed to coincide with high tides - and this might lessen environmental impacts - as the volume of ocean water would significantly increase, and this might minimize temperature fluctuations created by warm water outfalls. Do you know about this?

Ecological Damage....cont...

Hello Team:
That is a very good point about using the high tide for discharge times and the fact the temperature fluctuations would be minimize. They would have to discharge the water closer to the shore and to the surface to provide that environment where the wave action can effectively mix the warmer discharged water. The discharge times would only take place at certain times; therefore, there would have to be a holding tank until the scheduled release time. This would increase the actual volume of water released at any one time. According to Van Ryrin & Leraand (1992), the temperature of the discharged water is 12.6 °C which is approximately ~6 to 8 °C cooler than the sea. That is a high temperature difference compared to the ocean water. Most regulatory guidelines state that the surface water temperature should be within 3°C of the ambient air temperature. Even with wave action and volume, the temperature around the discharge point would still be slightly evaluated until release is completed. But this would be better than releasing regularly causing the species composition around the discharge area to change. In a freshwater environment, evaluated temperatures are more of an issue to the environment. The main environmental issue is that benthic invertebrates are highly sensitive to temperature fluctuations. Different species has different preferences to temperatures; therefore, the species composition near the discharge point will be different than 100 meters away. A solution to this issue would be to use a cooling pond to bring the water to ambient temperature prior to release. Another consideration for the adverse effects of this technology might be releasing metals, bacteria, and fungi to the natural environment. Over time, this may effect the marine ecosystem. For example, the point made by Kevin during the World Café was that copper can be very damaging to marine life. Copper fragments may be released into the ocean over a period of time from pressure of the water flowing through the copper plate in the piping system. The copper would then settle to the bottom where it may taken up by bottom-dwelling benthic invertebrates and adversely effecting them. The solution would be to regularly monitor the released water to determine metal levels, bacteria counts, and fungi etc over time period and determine a baseline.

Van Ryzin, J. & Leraand, T. (1992). Air conditioning with deep seawater: a cost-effective alternative. Ocean Resources 2000. Retrieved on February 18, 2008 from:

Ecological damage cont.....

Good discussion about the environmental impacts to water quality Leah. Lise’s idea is a valid one regarding the discharge into high tide to reduce the impact. “The solution to pollution is dilution.” Although this seems facetious, it is a potential disposal solution for some effluent, for example sewage effluent. I think if the only change in water quality is temperature, it is appropriate since most of the impacts would be localized. However, it is important to realize that it only takes small changes in temperature to have an effect on aquatic life.

If we are talking about other substances, such as metals that can become bioaccumulative, then other options would have to be considered, such as Leah’s holding pond suggestion (or remediation ponds).

Here is our B.C. Aquatic Life guideline for protecting freshwater and marine aquatic life.

Freshwater Aquatic Life
- lakes and impoundments + or - 1 degree Celsius change from natural ambient background
Marine and Estuarine Aquatic Life + or - 1 degree Celsius change from natural ambient background
the hourly rate of change up to 0.5 degrees Celsius
see narrative in footnote
2. The natural temperature cycle characteristic of the site should not be altered in amplitude or frequency by human activities.

This is another link that can explain some of the effects of temperature on aquatic biota, including benthic invertebrates as Leah suggested as well as fish: