The use of deep water cooling systems: Two Canadian examples

The use of deep water cooling systems: Two Canadian examples

Renewable Energy 34 (2009) 727–730 Contents lists available at ScienceDirect Renewable Energy journal homepage: The ...

113KB Sizes 0 Downloads 86 Views

Renewable Energy 34 (2009) 727–730

Contents lists available at ScienceDirect

Renewable Energy journal homepage:

The use of deep water cooling systems: Two Canadian examples Lenore Newman a, *, Yuill Herbert b a b

School of Environment and Sustainability, Royal Roads University, Victoria, Canada Sustainability Solutions Group, 11 Alex Cox Road, Tatamagouche NS B0K1V0, Canada

a r t i c l e i n f o

a b s t r a c t

Article history: Received 23 April 2007 Accepted 25 April 2008 Available online 7 July 2008

Deep water cooling involves using naturally cold water as a heat sink in a heat exchange system, eliminating the need for conventional air conditioning. The cold water is drawn from near the bottom or below the thermocline of a nearby water body. In this study Canadian deep water cooling systems in Halifax, Nova Scotia and Toronto, Ontario were documented. The expected economic and environmental benefits were realized, but barriers to large-scale adoption of the technology were apparent. This technology requires that a client with a large cooling need is near a deep, cold body of water, and payback times vary depending on the site. The public–private partnership approach proved to be beneficial in these two examples, and the Toronto approach in which many buildings are serviced at once by combining municipal pumping capacity can deliver cost savings on a shorter time span. Deep water cooling represents a successful example of a niche accumulation process and an example of electricity demand displacement. Many other locations in which heavy air conditioning users are located next to deep, cold water bodies could use this technology; several such sites exist in Canadian urban areas. Ó 2008 Elsevier Ltd. All rights reserved.

Keywords: Deep water cooling Demand displacement Niche accumulation Sustainable development

1. Introduction In many areas of the world, 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 compensated by cooling systems. Cooling can create a particularly troublesome electricity load 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, for example, as the highest demand for cooling often occurs at the same time of day as other demands peak as well. This intermittent load is of particular concern for those advocating a shift to an energy grid supplied by renewable energy, as cooling demand tends to be highest at times when there is little wind energy available and when conflicting water needs might limit hydroelectric output. The availability of solar power, of course, peaks at the times when cooling demand is highest, but in Northern climates solar is not yet a widely used option due to poor payback potential [1]. Air conditioning currently consumes as much as 18% of electrical output in some US markets [2]; any technologies that can considerably lower the energy demand of air conditioning will create a significant drop in electrical

* Corresponding author. Present address: Apartment 5, 234 Frank Street, Ottawa, Ontario K2P 0X6, Canada. Tel.: þ1 613 230 5475. E-mail address: [email protected] (L. Newman). 0960-1481/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.renene.2008.04.022

use, help to dampen fluctuations in electricity demand, and reduce 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 transferred from a cooler to a warmer medium, a very energy intensive operation. Highly significant energy savings can be achieved if the heat can instead be transferred to a mass of cooler material with a high capacity for absorbing heat such as water. The need for a compressor-based cooling cycle is eliminated. Water is not only a good heat sink due to its very high specific heat capacity; as water’s density rises as it cools many bodies of water have large cool masses of water at their lower depths. A permanent reservoir of cold water is created below a certain depth, known as the hypolimnion. One of the simplest ways to utilize this large heat sink involves pumping a flow of hypolimnion water to the surface and using it as a heat sink. Water is 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. The technology is simple and certainly not new; however, the availability of cheap electricity has presented a significant barrier to implementation.


L. Newman, Y. Herbert / Renewable Energy 34 (2009) 727–730

However, increasing interest in reducing environmental impact, particularly in terms of greenhouse gas emissions, paired with the threat of unpredictable and rising energy prices, is making deep water cooling more attractive as an option. This case study of deep water cooling was conducted as part of a larger study, Sustainable Infrastructure: Implications for Canada’s Future, which was jointly funded by Infrastructure Canada and the Social Science and Humanities Research Council of Canada. Over the course of this project we investigated innovative community-level sustainable development projects in areas such as energy, transportation, and waste disposal. In general we found that successful projects thrived due to ‘‘niche exploitation’’; local conditions were such that barriers to adoption could be overcome. As explained below, the deep water cooling cases relied on local geography, support from various levels of government, and developers will to take on risk to showcase an innovative technology.

Purdy’s wharf did require 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 obstacles to this project was control of marine growth. Initially chlorine was used to prevent marine growth in the system, but this was both costly and potentially environmentally damaging. That system was replaced by cathodic protection provided by copper plates. To provide the required cooling performance, the water temperature must be below 10  C. The intake for the pumping system is located less than 200 m offshore at a depth of 18 m where conditions are appropriate for cooling for 10.5 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.

2. The case studies

2.2. Case study two: Enwave, Toronto

In the following sections two case studies are examined. The first, a medium scale saltwater cooling system in Halifax, Canada, was constructed in 1986, and is one of the oldest deep water cooling systems in operation. The second, a large-scale network in Toronto, Canada, began operation in 2004 and continues to expand. These projects provide an interesting set of complimentary and contrasting features. They differ in scale, one uses saltwater and the other lake water, and one was constructed by a developer to serve one building complex and the other was constructed by a company that provides cooling as a service to multiple sites. However, both projects involve public–private partnerships, and both were and are successful economically and in terms of electrical demand displacement.

Enwave’s Deep Lake Water Cooling project is a much larger project than the Purdy’s wharf initiative. Pipes extend 5 km into Lake Ontario and draw water from a depth of 83 m to the John Street pumping station where heat exchangers cool Enwave’s closed cooling loop that snakes through downtown Toronto. The lake water, slightly warmed, then goes on to supply Toronto with drinking water. This sharing of drinking water and cooling 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 [3]. As of June 2006, 46 buildings were signed to the system and 27 were already connected [4]. 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 m2, or 50 times the area of the Purdy’s wharf development. Sixty-one percent of this capacity has been sold [4]. There is some discussion of expanding the system once capacity is reached. Energy savings are about 90%, and as the required cold water is available all year round the need for supplementary chilling is eliminated. The project is owned jointly; 57% by the municipal pension fund and 43% by the city of Toronto, and is thus an example of a public–private partnership. The total cost of the Enwave project in Toronto was over $235 million, including $175 million in capital costs and $55 million for a new city water intake (the system extracts the cold from incoming city water). The project was funded through a mix of share capital and debt financing and is a long term, but profitable investment. In 2005, the deep lake cooling system was operating at 51% of planned capacity but was still generating sufficient cash flow to cover its operating and financial costs and a lender therefore predicted that continued growth in the company’s profitability is highly predictable and from the customer’s perspective connecting to the deep water cooling system is advantageous, as illustrated by the case of Toronto City Hall. The air conditioning capital costs required to tap into Enwave’s system were estimated at $2.5 million as compared to $3.1 million for a conventional system, with additional operating cost savings of $100,000 per year [4]. Enwave’s system uses one-tenth of the electricity of a standard air conditioning system, freeing up 61 MW of electricity from Ontario’s electricity grid during peak period. This savings avoids emissions totaling 79,000 tonnes of carbon dioxide and reduces the need for water for cooling towers by 714 million litres of water [5]. Capital costs continue as the urban pipeline network expands. The project was a public–private partnership; 33 million dollars came from the City of Toronto’s pipe repair fund [6], a move that was not without controversy. The Federal government provided low

2.1. Case study one: Purdy’s wharf, Halifax The Purdy’s wharf office complex sits on the waterfront of Halifax, and the 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. There the buildings closed loop of cooling water is cooled by the seawater, and it 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 4-story retail centre. The total area cooled by the system is 65,000 m2. The Purdy’s wharf project was funded jointly as a demonstration project by the development company, JW Lindsay Enterprises Limited, and the federal government. The seawater cooling system was a $400,000 (all costs in Canadian $ as paid at time of construction) upgrade over a conventional cooling system, primarily due to expensive titanium heat exchangers. While the cold ocean water is freely available, pumping costs to bring the water into the building cost $30,000 per year. Other operational costs include cathodic protection of the saltwater intake at $3500 per year for copper bars. Estimated annual savings, however, total $177,350 in reduced electricity load, building maintenance and operation load with respect to a conventional air conditioning system. The simple payback was estimated to be 2.3 years. The system cannot function year round due to fluctuating harbour temperatures; this was understood at the time of construction. Since construction, Purdy’s wharf has demonstrated that deep water cooling systems can provide financial benefits even when they cannot operate year round.

L. Newman, Y. Herbert / Renewable Energy 34 (2009) 727–730

interest loans, and Toronto Hydro also provided incentives for companies to hook their buildings up to the system in order to overcome the high initial capital cost. Kevin Loughborough of Enwave commented on the up-front costs: ‘‘The payback 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.’’ (Loughborough, personal communication) 3. Project successes and barriers Success in both case hinged upon the private–public partnership model. This model provided a way to overcome the high up-front costs associated with this technology. As noted by Vermeulen and Hovens [7], subsidies can greatly speed the adoption of young innovations. As explored by Dormois et al. [8], public–private partnerships use a ‘‘lever-effect’’ to kick-start private innovation using public money. The involvement of government also eases the fear that zoning and bylaw issues will make adoption of an innovation impossible. In this way public–private partnerships spread risk [9], opening up niches that might not have been viable environments of an innovation otherwise. In the 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 giant 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. Kevin Loughborough of Enwave 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 Purdy’s wharf project went forward because the developer in question was willing to take a risk on fairly new technology. The Toronto project was much larger, and succeeded as it had support from individuals in government and in business. These ‘‘champions’’ worked together to maneuver the project through various hurdles. This agrees with the findings of Vermeulen and Hovens [7], who note that the opinion of decision makers greatly influences whether or not an innovation is adopted. Both of these projects achieved their goal of drastically lowering 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 has attracted more attention partly due to its location in a city experiencing significant smog problems and electricity shortages, and it continues to expand. Purdy’s wharf, however, does demonstrate that the technology can work on a smaller scale in certain situations. Purdy’s wharf did not cause widespread adoption of the technology even though it was a successful project. Contributing factors could include the low cost of energy at the time and a lack of comparable projects, as it was one of the first in the world. Also, a developer wanting to mimic Purdy’s wharf would have to start from scratch as the infrastructure has capacity for one development only. To a degree, the technology was at least temporary stuck within its narrow niche, a pitfall identified by Raven [10]. Others agree this is as not unusal; Dieperink et al. [11] found that energy technologies take 5–10 years to spread. It has been rightly remarked that the transition to sustainable development is alarmingly slow [12], partly due to the magnitude of the changes required. 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 that the main factor in a successful deep water cooling project is ‘‘geography’’. ‘‘The key ingredients for the project are a high density cooling cluster located near a renewable cooling resource.’’ (Loughborough, personal communication). 4. Discussion Deep water cooling is an interesting example of niche exploitation and ‘‘niche accumulation’’ which refers to the adoption of new technologies within specific sets of environments or circumstances in which they enjoy an advantage due to local conditions, allowing them to spread to other similar niches. Technical niches protect new technologies from early rejection [10]. In this case the Halifax deep water cooling project was constructed in a location with an unusually cold body of water immediately adjacent to the site. Such early adoption gives an opportunity for proper government policy and bylaw design to occur, and as Raven [10] points out, this can lead to niche branching in which the technology spreads to a larger, less specialized niche. In this case, the Toronto example is a large-scale project that also relies on specific local conditions to be successful; the Toronto example was partially inspired by the success of the Halifax example. Using deep water cooling and heating to offset electrical demand is significant for two key reasons; firstly it offsets expensive, fossil fuel dependent, peak demand generation and secondly, the use of electricity for heating and cooling is inefficient and costly. Electricity as a commodity has the unusual characteristic of being extremely difficult and expensive to store. The supply of electricity must be flexible to meet highly variable real time demand. Grids maintain this flexibility at a range of timescales; in the short term increasing the generation rate of online base load capacity and in the longer term by starting up reserve generating capacity. The decisions regarding which generating capacity to use at which point is highly complex, influenced by other factors, operating costs and start-up and shut-down time requirements. Energy managers typically use the lowest cost generating capacity for the base load and draw on more expensive capacity for peaks, either running plants above the optimal rate or dispatching plants using higher cost fuels, depending on the timescale of the peak. Typically, utilities maintain peak generation capacity equal to base load capacity. Peak generation capacity is, with current technologies, fossil fuel dependent, the one exception being utilities that can draw on significant hydroelectric capacity. Renewable energy technologies such as tidal, wind and solar generation are intermittent as output varies with environmental conditions over which the operator has no control, and therefore can be used only to offset base load generation. For this reason, offsetting peak demand using deep water heating or cooling is significant for reducing greenhouse gas emissions. Jaccard [13] notes the variability of electricity demand as one of the central obstacles to wider use of renewable sources. Any technology that reduces peak demand helps to reduce this problem. A niche exists for technologies such as deep water cooling due to the relatively high cost of cooling with electricity. Though electricity costs in North America are still low, cooling is significantly more expensive than heating, which can be accomplished with the direct burning of fossil fuels. Builders and property managers are thus open to possible methods of reducing cooling costs. The overall impact on electrical use is also greater due to transmission line losses and inefficiencies resulting from the conversion of fuel into electricity. A diversity of localized energy sources provides security and avoids transmission losses [14]. The slow adoption of technologies such as deep water cooling is partly a historical


L. Newman, Y. Herbert / Renewable Energy 34 (2009) 727–730

aversion to the risks posed by new technologies. As Verbruggan [15] notes, the history of energy use in industrialized nations has been one of neglecting or rejecting free energy from the sun or the environment. One of the theoretical barriers to future expansion is what Gregory Unruh calls ‘‘carbon lock-in’’ [16], as energy technologies have co-evolved to require carbon based fuel, there is an increasing return on investment that favours large-scale technologies and discourages the diffusion of non-carbon options even if they are economically sound. Though the impact of deep water cooling is overwhelmingly positive, there has been some worry that the cold water source could experience ‘‘heat pollution’’ if overused. Such pollution could have a negative effect on habitat and species composition. In the ocean, such effects might occur on 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 20,000 m3/s of water could be withdrawn from the lake and used for cooling without changing the lake’s physical properties [17]. For the Great Lakes the maximum draw amount is very large, but this number will be lower for smaller lakes, and must be taken into account when discussing the sustainability of deep water cooling using lake water. In the case of the Toronto example, the water withdrawn is then used for municipal use, and re-enters the lake in a diffuse manner as treated sewage or as run-off. In the case of Halifax harbour, the environment in question is already greatly altered from its original condition. The projects discussed had to follow established procedure for construction in coastal area, but long-term effects might differ greatly from place to place and it is likely that some locations should be rejected due to potential damage due to heat pollution. 5. Conclusions The successful demonstration of deep water cooling technology in Halifax and Toronto could encourage the spread of this technology to other viable ‘‘niches’’. The potential for expanded use of deep water cooling in Canada and the world is quite large. Both Halifax and Toronto could greatly increase their use of this technology without creating a serious environmental hazard. Several other major Canadian cities are located near deep, cold water, and there are hundreds of smaller centres located next to deep bodies of cold water that could also utilize this form of cooling. The Toronto project found a way to greatly reduce costs by combining their

needs with that of the municipal water supply; this technique could be repeated in other areas near a major freshwater body. The technology needs of saltwater installations will remain more complex due to the more difficult environment seawater poses, but the number of potential near-ocean locations is much larger than that of freshwater sites. These cases also demonstrated the potential of public–private partnerships to encourage adoption of new sustainable development innovations. Acknowledgements The research described in this paper was funded by Infrastructure Canada and the Social Sciences and Humanities Research Council of Canada (SSHRC). References [1] Monbiot G. Heat: how to stop the planet from burning. Doubleday Canada; 2006. [2] Cox S. Air conditioning: our cross to bear. AlterNet. Available from: http://; 2006. [3] Deverell J. Enwave launches deep-lake cooling project. Toronto Star 2002 June 20:B02. [4] City of Toronto. Deep lake water cooling and the city. Available from: http://; 2006. [5] Candian Press. Lake water to cool downtown. Toronto Star 2003 February 28: E11. [6] Molony P. Pipe funds diverted. Toronto Star 2004 May 24:B02. [7] Vermeulen W, Hovens J. Competing explanation for adopting energy innovations for new office buildings. Energy Pol 2006;34:2719–35. [8] Dormois R, Pinson G, Reighnier H. Path dependency in public private partnerships in french urban renewal. J Hous Built Environ 2005;20:243–56. [9] Linder S. Coming to terms with the public private partnership: a grammar of multiple meanings. Am Behav Sci 1999;43(1):35–51. [10] Raven R. Niche accumulation and hybridization strategies in transition processes towards a sustainable energy system: an assessment of differences and pitfalls. Energy Pol 2007;35:2390–400. [11] Dieperink C, Brand I, Vermeulen W. Diffusion of energy saving innovations in industry and the built environment. Energy Pol 2004;32:773–84. [12] Rammel C, Kastenhofer K. Obstacles to and potentials of the societal implementation of sustainable development. Sustain Sci Pract Pol 2006;1(2). [13] Jaccard M. Sustainable fossil fuels: the unusual suspect in the quest for clean energy. Cambridge Press; 2005. [14] Li X. Diversification and localization of energy systems for sustainable development and energy security. Energy Pol 2005;33:2237–43. [15] Verbruggan A. Stalemate in energy markets: supply extension versus demand reduction. Energy Pol 2003;31:1431–40. [16] Unruh G. Understanding carbon lock-in. Energy Pol 2000;28:817–30. [17] Boyce F, Hamblin P, Harvey L, Scherzer W, McCrimmon R. Response of the thermal structure of lake ontario to deep cooling water withdrawals and to global warming. J Great Lake Res 1993;19(3):603–16.