|
||||||||||||
The Great Lakes are a source of hydroelectricity, a marine navigation system, a thermal reservoir for thermal power stations and a source both of potable water for human populations and of industrial water. It is also a septic tank for effluent from municipal and industrial sewer systems. Efforts are underway to ensure that cleaner and less polluted water will in the future flow into the Great Lakes from municipal and industrial waste water systems.
Dropping Water Levels in the Great Lakes
Water levels measured over the past few years at the Port of Montreal indicate that the water depth has dropped by more than six feet (or two meters) over the past century. Until the summer of 2009 concerns were raised about dropping water levels in and receding shores along Lake Superior and Lake Huron. While recent rainfall has replenished some of the water, there seems to be growing interest in using lake water more efficiently.
The energy and marine transport sectors can certainly contribute to that objective and would require new capital investment over the long-term future. Part of that investment may include additional navigation locks along certain channels of the St. Lawrence Seaway so as to maintain sufficient depth in the navigation channels. Those locks may be used to reduce water flow rate through several channels during the winter months when ship traffic is absent.
There may be scope in the future to build a set of navigation locks on the St. Lawrence River near Quebec City so as to maintain navigation depth for "Panamax" sized ships to access the Port of Montreal throughout the year. The presence of such locks would maintain greater water depth at and to the west of Montreal and would allow water to be pumped uphill over the power dams at Beauharnois into Lake St. Francis and at the Moses-Saunders power dam into Lake St. Lawrence. The energy from wind installations would be used to pump the water uphill.
Wind Power and Storage
There are plans to install wind turbines along the shores of the Great Lakes on both the Canadian and American sides. The prime beneficiaries of this wind power would be the states of Michigan, Ohio and New York and the province of Ontario. Wind power is unpredictable and will generate high output during off-peak demand periods. Powerful winds blow over some 1,500 islands on the eastern side of Hudson Bay as well as along the western coast of Quebec along Hudson Bay and James Bay. Many of these islands and part of that extensive coastline are within close proximity to Hydro-Quebec's James Bay hydroelectric generation installations.
Several companies worldwide are developing airborne and high-altitude wind power technology. A single installation of the Laddermill concept from Delft University in the Netherlands is estimated of being capable of some 100 MW output. There may be potential to install up to 1,000 such installations on the islands of Hudson Bay and along the west coast of Quebec and generate up to 100,000 MW during the winter months when powerful winds blow in this region. A large percentage of that wintertime power can be stored in the future by pumping water uphill from Lake Ontario to Lake Erie.
Ocean Power Generation
There is a potential for several thousand megawatts of energy in the ocean waves off the American east coast. New technology is under development to convert a portion of that energy to electrical power. Excess off-peak ocean wave energy could be stored at any of several existing and proposed installations along the Great Lakes.
There is ongoing research as to how to convert a large proportion of the ocean tidal energy at the Bay of Fundy into electrical power. Tidal dams and kinetic turbines have already been installed around that bay. There may be potential to build tidal straits to carry a portion of the peak-tidal seawater from the Bay of Fundy to lower tidal water levels that occur across the isthmus in St. Margaret's Bay and in Northumberland Strait. Excess off-peak power may be transferred into storage along the Great Lakes.
A study undertaken by Triton Consultants of Vancouver indicated that there might be in excess of 17,000 MW of energy in the westbound tidal current that flows through Hudson Strait in the channels between Salisbury Island and the Foxe Peninsula of Baffin Island. The channel is also a navigation channel. It may be possible to install low-height (transverse-axis), free-flow turbines across the deeper sections of that channel and generate up to 3,000 MW of electrical power, a portion of which would serve native communities in the region. A minimum of 2,000 MW may justify the cost of installing a transmission line to Hydro-Quebec's James Bay installation from where excess off-peak power may be transferred into storage along the Great Lakes.
Flood Waters
Seasonal flooding occurs along most rivers across the northern U.S. and Canada during the early spring. Mayan engineers built rock dams at regular intervals at the higher elevations along tributaries and headwaters to reduce rivers from flooding agricultural land at the lower elevations. The Mayan technique could be applied to the headwaters of many rivers across the northern U.S. and Canada.
Governments may need to allow private people the freedom to build rock dams and even small, kilowatt-size power dams along the headwaters of many rivers to reduce flooding at lower elevations. Electric power generated by small power stations at the higher elevations may be fed into the grid and into storage during the off-peak periods. There have been occasions where the Hydro-Quebec dams at James Bay have operated at peak capacity.
The absence of available pumped storage resulted in hydrogen having been produced from excess the electric power, at an overall efficiency of less than 35 percent. By comparison, pumped hydraulic storage can return 65 percent to 80 percent of the off-peak energy supplied to such installations. Improved flood control along rivers that flow into the Great Lakes and Seaway system can reduce local flooding along those systems and help maintain water levels over the long term.
Seasonal Hydraulic Storage using the Great Lakes
Seasonal non-pumped hydraulic storage would operate along the Great Lakes and St. Lawrence Seaway during winter months and would complement pumped hydraulic storage operations. During the overnight off-peak periods hydroelectric power generation would cease operation at installations along the Great Lakes and along its tributaries and headwaters. The lower water levels in Lake Superior, Lake Michigan, Lake Huron and Georgian Bay provide storage capacity for non-pumped seasonal hydraulic storage.
The overnight market demand would receive electric power from a combination of thermal power stations that would operate at constant steady output as well as from wind energy and ocean energy sources. Such operation could gradually increase water levels along the Great Lakes and St. Lawrence Seaway system during the winter overnight off-peak hours. A portion of that stored energy could be utilized during the peak demand summer months.
Pumped Hydraulic Storage
New York State and Ontario have recognized the need to increase pumped hydraulic storage capacity so as to more efficiently serve a growing future market demand. There is also growing environmental opposition to "destroying" valleys that may be used for pumped storage such as the Ludington installation in Michigan. There is far less opposition to pumping water uphill between existing lakes or uphill across existing hydroelectric dams.
One possibly new approach to pumped storage is to use either existing cavities in the earth to store water or to excavate new ones. Several large salt domes of up to one mile in diameter and six miles in vertical height are used to store compressed natural gas in the region near Niagara Falls. Similar domes that are too close to the ground's surface are generally unsuitable to store high-pressure natural gas for risk of "blowing its top."
That propensity also eliminates their potential use for high-pressure pneumatic storage. Such domes that are located near a lake or river may be flushed of rock salt and used for pumped hydraulic storage of up to 1,000-MW capacity. Alternatively, special cavities may be excavated in the earth at depths of some 2,000 feet for the same purpose. The Riverbank Power group had planned to install such technology along the St Lawrence River some 40 miles upstream of the Moses-Saunders power dam.
Underground pumped storage would require an air vent to the surface to accommodate the rise and fall of water within the hydraulic storage chamber. A combination of pumped hydraulic and low-pressure pneumatic is possible, and air can be preheated prior to expansion to increase output from the turbines. Such underground storage technology may best be built at various locations around the Great Lakes downstream of the power dams and well away from the navigation channels.
Niagara Pumped Hydraulic Storage
The attractive location for pumped hydraulic storage operation is an attractive tourist destination. A certain volume of water has to flow over Niagara Falls during the daytime to maintain the lucrative tourist trade. A percentage of the water volume that flows from Lake St. Clair into Lake Erie can still flow over Niagara Falls to maintain the tourist attraction during the early evening hours. The presence of a dam located upstream of Niagara Falls allows water flow to cease for several hours overnight while water is being pumped more than 325 feet uphill from Lake Ontario.
There is scope over the decades that lie ahead to drill additional tunnels and gradually increase the combination of generation and pumped hydraulic capacity to an excess of 10,000 MW over a 10-hour duration. The immense surface areas of Lake Erie and Lake Ontario would limit the overnight change in water elevation to the season height fluctuations for both lakes. Over the long-term future the multi-tunnel approach would fulfill the daily requirements for pumped storage of a very large geographic area that would lie within 600 miles of Niagara Falls. There is also scope to develop deep-level (2,000 feet) underground pumped hydraulic storage capacity downriver of Niagara Falls and within the same geographic region.
The Ocean-based Precedent
The oceanic precedent occurs at coastal cities such as Vancouver where the water level may fluctuate by 16 feet (or five meters) twice daily. The dropping water levels that have steadily occurred in the Great Lakes for over a century could provide the needed storage volume in Lake Erie to allow for such a fluctuation in water height. It is based on the assumption that water levels would remain at their low levels over the long-term future. A minimal volume of water would flow over Niagara Falls during winter days to sustain the winter tourist trade.
A seasonal height fluctuation of five meters in Lake Erie is theoretically possible and the shoreline could be prepared for such future operation. The vast potential for wintertime airborne wind energy from Hudson Bay would replace wintertime hydroelectric power generation along the Great Lakes and St. Lawrence River to allow water levels to build up in Lake Erie during winter. Such an operation would complement daily off-peak pumped hydraulic operation and use electric power from thermal and nuclear power stations that would be set to operate at relatively constant output.
Small-Scale vs. Large-Scale Pumped Storage
There is scope for small-scale (100 kW to 50 MW) pumped storage to coexist with large-scale pumped storage along the Great Lakes and St. Lawrence Seaway. Advances in low-height hydraulic turbine technology has increased conversion efficiency to more than 80 percent for height differences of more than four feet and at 70 percent for 2.3 feet. Such technology can be installed in additional locks and/or control dams that may be built along the Seaway system to increase water volumes in the Great Lakes.
Low-power installations of under 50 MW would serve mainly highly localized markets at the proposed locks near Quebec City, at the Beauharnois power near Montreal and at the Moses-Saunders power dam. It would be beneficial to allow private entrepreneurs to build mini and micro pumped hydraulic and hydroelectric installations along the many rivers and streams that ultimately feed into the Great Lakes and St. Lawrence River and serve mainly local markets or feed into the grid.
Water levels in Hydro-Quebec's James Bay hydroelectric dams have on occasion reached peak capacity during the early spring and with no capacity for pumped storage. The additional volume and surface area of Lake Ontario and Lake Erie as well as the other Great Lakes would be able to provide storage capacity at such times. The large-scale storage systems would serve large markets in major cities such at Chicago, Detroit, Toronto, Cleveland and New York City.
Conclusions
There are economic benefits to be realized from the operation of pumped hydraulic storage along the Great Lakes. It has the capacity to serve the energy needs of a very large segment of the population of both the United States and Canada. That vast energy storage capacity will require investment in fewer nuclear and thermal power stations that will operate at more constant output and achieve at greater cost-effectiveness due to the reduction of failure due to the build-up of cyclical thermal stresses. Over the long term, the cost of introducing massive hydraulic storage capacity on the Great Lakes may be justified on the basis of the efficiency by which other power generations technologies are used.
