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XYLENE POWER LTD.

SEASONAL PUMPED HYDRAULIC ENERGY STORAGE BETWEEN LAKE ERIE AND LAKE ONTARIO

By Charles Rhodes, P. Eng., Ph.D.

INTRODUCTION:
A major problem with large scale use of renewable energy for electricity generation in Ontario is the seasonality of availability of that energy. In Ontario on a monthly average basis both wind and run-of-river hydro are two times more plentiful in mid-winter than in mid-summer. However, in Ontario the peak electricity load occurs in mid-summer. In order to fully utilize renewable energy Ontario needs a practical means of efficiently and reliably storing electrical energy for about six months.

At this time the only technology that is economic for large scale seasonal electricity energy storage is pumped hydraulic energy storage between the great lakes. This document assesses the amount of pumped hydraulic energy storage that can reasonably be obtained using Lake Erie as the upper reservoir and Lake Ontario as the lower reservoir. This document then addresses practical realization of that energy storage with 10 GW of additional load following electricity generation.
 

FRINGE BENEFIT:
A fringe benefit of this project is that it would allow better level control of Lake Erie. At the present water runs out of Lake Erie at a rate set by the level of Lake Erie and the contour of the Niagara River bottom. Under the plan set out herein the Niagara River bottom would be dredged and the outflow from Lake Erie set by the position of control gates located close to the point where Lake Erie discharges into the Niagara River.
 

SAFETY:
Lake Erie and Lake Ontario are presently separated by a 30 km wide natural land barrier. There is about a 99 m difference in lake surface elevations. The amount of gravitational potential energy that could be released by uncontrolled water flow from Lake Erie to Lake Ontario is enormous. Hence this project must be designed to tolerate major earthquakes. This project must have multiple redundant safety systems.
 

FINANCING:
As with any large electricity project, to minimize the cost of construction financing it is necessary to minimize the time between expenditure of capital funds and ratepayers receiving a tangible benefit. Hence the project must be designed to proceed in stages such that there is an immediate tangible benefit to the ratepayers as each stage is completed. This staging requirement significantly affects the detailed design of the energy storage system.
 

ASSUMPTIONS:
It is assumed herein that Niagara Falls must be kept substantially unchanged as an international tourist attraction. It is assumed herein that over a period of about 50 years a multiplicity of new canals will be built in the proximity of the existing Welland Canal for the exclusive purpose of guiding water that is pumped uphill from Lake Ontario into Lake Erie. It is further assumed that additional load following electricity generation will be built in the proximity of Niagara Falls and that over a period of years the Niagara River valley and the downstream Niagara gorge will be enlarged to allow a substantial increase in the peak Niagara River flow.
 

TECHNOLOGY:
This document indicates how the contemplated energy storage system could be realized using construction technology similar to that which was used in British Columbia in the mid 1960s for construction of a major gravity dam on the Peace River and similar to the Red River Floodway in Manitoba. The control gates at the Lake Erie end of the Niagara River would be similar to those used on the Thames Barrier in the UK.
 

INTERNATIONAL CONSIDERATIONS:
It is envisaged that the costs and benefits of this energy storage system would be shared with the USA, so that this energy storage system would ultimately provide about 5 GW of seasonal peaking generation for Ontario and about 5 GW of seasonal peaking generation for the USA. The use of dedicated US pumps and dedicated US generators would allow storage of surplus electrical energy from the USA and recovery of that energy without having to integrate the corresponding electricity flows into the Ontario electricity system. Similarly, subject to international treaty constraints, Canada could proceed with its portion of the project with minimal US participation.
 

PROJECT SIZE:
The size of this energy storage project project is less than half the size of the existing hydroelectric development on the Columbia River in British Columbia and Washington State.
 

GEOGRAPHICAL CONSTRAINTS:
The nominal elevation difference between the surface of Lake Ontario and the Surface of Lake Erie is 99 m. However, 5 m of water head is lost in moving water horizonatally between Lake Erie and Lake Ontario or vice versa. Thus the net charging pump head Hdc required to move water from Lake Ontario to Lake Erie is:
Hdc = 99m + 5 m = 104 m
and the net discharge generator head Hdd available for electricity generation is:
Hdd = 99 m - 5 m = 94 m.
Hence even if the motors, pumps, turbines and generators are all 100% efficient the energy storage system has a theoretical maximum efficiency cap of:
(94 m / 104 m) = .9038

In order to control the flow through the Niagara River it is necessary to build a set of very robust control gates at the inlet to the Niagara River from Lake Erie. These control gates should be earthquake resistant. It is envisaged that these control gates would be similar in design to the control gates used on the existing Thames Barrier in the UK. The exact location of these control gates will be dictated by local topographic features and local depth to bedrock. These control gates should be engineered to allow an ultimate depth swing in Lake Erie of about 4 m.
 

PUMPED HYDRAULIC ENERGY STORAGE SYSTEM POTENTIAL:
1. A reasonable estimate of the costs of realizing pumped hydraulic energy storage between Lake Erie and Lake Ontario indicates a total cost of the order of:
10 GW X $4000/ kW X 10^6 kW / GW = $40 X 10^9
= $40 billion
It is envisaged that the project would proceed in four stages, at about 10 year intervals. Each stage would cost about $10 billion. Each stage would involve the construction of a 30 km canal, complete with bridges, pumps and transmission lines. Each canal would be comparable in size to the Red River Floodway. Completion of each stage would potentially increase the annual level swing in Lake Ontario by 1.25 m. The actual increase in level swing would be implemented at 0.1 m / year.

2. In order to justify the project cost it is essential that the amount of seasonal energy storage be maximized.

3. The gravitational potential energy recoverable from storage is:
M X G X Hdd
where:
M = mass of water raised
G = gravitational acceleration = 9.8 m / s^2

4.The surface area of Lake Ontario = 19,525 km^2

5.The surface area of Lake Erie = 25,700 km^2

6. M = (area of the smaller lake) X (maximum acceptable change in lake level) X (density of water)

7. The (maximum acceptable change in lake level) is ultimately governed by the change in water level that can be accommodated by future marine installations. At major ocean seaports throughout the world this change in water level due to ocean tides is typically 5 m. Hence, given sufficient time to implement changes in lake marine facilities (50 years), an annual 5 m water level swing could be accommodated in Lake Ontario. The corresponding water level swing in Lake Erie would be only 3.8 m due to Lake Erie's larger surface area. However, other issues controlled by the USA and by natural events might further affect the level of Lake Erie.

8. Thus a reasonable estimate of M is:
M = (19,525 km^2) X (10^6 m^2 / km^2) X (1000 kg / m^3) X 5 m
= 97.625 X 10^12 kg

9. Thus the contemplated available gravitational potential energy is:
M X G X Hdd
= 97.625 X 10^12 kg X (9.8 m / s^2) X 94 m
= 89.932 X 10^15 joules

10. Assume that the electrical turbine-generator efficiency is 0.80. Then the recoverable energy from storage is:
0.8 X 89.932 X 10^15 J = 71.946 X 10^15 J
= 71.946 X 10^15 watt-s X (1kw / 1000 w) X 1 h / 3600 s
= 19.984 X 10^9 kwh
= 19,984 Gwh

11. Thus in changing from the fully charged state to the fully discharged state the pumped storage system could supply an additional 10 GW of electricity for 1998.4 hours. This storage time is sufficient to permit excess wind energy generated during the winter to be stored and later used during the summer. Canada's 5 GW share of the storage output could, in combination with sufficient wind and run-of-river electricity generation, be used to displace much of the existing fossil fueled electricity generation in Ontario. It would also absorb over half of the presently constrained non-fossil generation within the Ontario electricity system. Sale of that presently constrained energy during peak demand periods would increase electricity system gross revenue by about $4 billion per annum.

12. The additional water mass flow required to supply this 10 GW is:
97.625 X 10^12 kg / 1998.4 h
= 48.851 X 10^9 kg / h

13. Converting this mass flow into a volume flow gives:
48.851 X 10^9 kg / h X 1 m^3 / 1000 kg X 1 h / 3600 s
= 13.57 X 10^3 m^3 / s

14. This volume flow compares to the present average Niagara River volume flow of about 5.7 X 10^3 m^3 / s

15. Thus the new peak volume flow would be:
(13.57 + 5.7) / 5.7
= 3.38
times the present average Niagara River volume flow. Attaining this increase in peak river flow upstream of the generation tunnel intakes likely entails extensive dredging of the river bottom.
 

PROJECT REALIZATION:
1. In order to realize this energy storage system while taking maximum advantage of the existing installed generation it is necessary that a multiplicity of new canals be built in the proximity of the existing Welland canal. The size of each of these new canals would be comparable to the existing Red River Floodway in Manitoba.

2. The volumetric flow through the new Niagara Tunnel is 500 M^3 / s.
The inside diameter of the Niagara Tunnel is 12.7 m.
The cross sectional area of the Niagara Tunnel is given by:
Pi X (12.7 m / 2)^2 = 126.67 m^2
Hence the axial flow velocity is given by:
(500 m^3 / s) / (126.67 m^2) = 3.947 m / s

2. Since these new canals would have intermittent mono-directional flow, the flow velocity could be relatively high. At an average flow velocity of 10 m / s and at a volumetric flow rate comparable to the Niagara River, each canal's cross sectional area would have to be:
(5700 m^3 / s) / (10 m / s) = 570 m^2.
A suitable cross section shape might be 80 m wide on top, 10 m deep and 60 m wide on the bottom. The sides would slope at 45 degrees. This shape would result in a cross sectional area of 700 m^2, providing some allowance for higher than planned flows.

3. Each canal would consist of several slightly sloping sections. Each section would commence with pumps at the bottom of 20 m deep pond. The primary functions of these ponds are to provide the required pump suction head and to enable changes in canal axis direction.

4. The canal routes would in part be determined by the availability of natural topographic features consistent with the required canal shape, slope and pond requirements.

5. In some areas the canals would have walls extending above local grade level. These walls would be fabricated in a manner similar to a rock fill gravity dam. Rock with which to build these walls would be obtained from the higher elevation sections of the canal. This rock can be easily conveyed downhill several km using very long conveyor belts, similar the the conveyor used during the construction of the Bennett (Peace River) Dam.

6. Several new 10 km long tunnels, each comparable to the new Niagara tunnel, would be required to convey water from the tunnel intake upstream of Niagara Falls to the head water pond of the generation station which is downstream of Niagara Falls. These tunnels, if built sequentially, would likely each cost about $1.2 billion to provide a 500 MW generation increment.
 

STORAGE EFFICIENCY:
1. The amount of electrical energy required to take the storage from its fully discharged state to its fully charged state is:
(M X G X Hdc) / Ep
Where:
Ep = pump efficiency = .75

2. The storage system efficiency is given by:
(recovered energy) / (charging energy)
= (M X G X Hdd X Eg) / [(M X G X Hdc) / Ep]
= (Hdd X Eg X Ep) / Hdc
= (94 m X .80 X .75)/ 104 m
= .5423
 

COST OF SEASONAL PEAKING ENERGY:
Assuming that available financing requires a simple payback period of 7.34 years the cost of capital financing included in the cost of electrical energy recovered from seasonal storage is:
($40 X 10^9) / (19.984 X 10^9 kWh/year X 7.34 years)
= $.2045 / kWh
The cost of the corresponding presently constrained non-fossil energy that went into seasonal storage at $.02 / kWh is:
($.02 / kWh) / 0.5423 = $.0369 / kWh
Hence the total cost of summer peaking energy recovered from seasonal energy storage is:
$.2045 / kWh + $.0369 / kWh = $.2414 / kWh
This cost is much less than the cost of obtaining peaking generation from a new nuclear power plant and is likely less than the cost of purchasing peaking electricity from Quebec and transmitting that electricity from Quebec to southern Ontario.
 

PROJECT LIMITATION:
From a power system perspective this project does have one important limitation as compared to a conventional hydroelectric dam. The response time of the electricity generation to a change in upstream control gate position is limited by the length of the Niagara River and the velocity of the water flow. Even if the water flow velocity is increased to 10 m / s the response time will still be:
30 km / (10 m / s) = 3000 s ~ 1 hour

Hence to make efficient use of the control gates for load following the Independent Electrical System Operator (IESO) must anticipate a load change one to three hours before it actually occurs. If the future load is underestimated the generation will fail to track the load. If the future load in both Canada and the USA is over estimated some of the stored water may be wasted via diversion over Niagara Falls. In view of the IESO expertise at near term future load and generation projection this limitation is not believed to be a serious problem.
 

SUMMARY:
Physical realization of a pumped hydraulic seasonal energy storage system using Lake Erie, Lake Ontario and the existing Niagara River generation entails the construction canals for guiding water that is pumped uphill from Lake Ontario to Lake Erie. This project also entails construction of upstream control gates on the Niagara River and additional generation and related tunnels in the proximity of Niagara Falls.

This document outlines a large project that can be built in stages spread over many years. However, even when complete this project is less than half the size of the combined Canadian and US hydroelectric power development on the Columbia River. There are 14 dams on the main stem of the Columbia River. The Grand Coulee Dam alone has 6.8 GW of electricity generation capacity.

A major benefit of the contemplated Lake Erie-Lake Ontario pumped storage project is that it offers a large amount of seasonal energy storage located close to major electricity markets with no land flooding due to formation of new lakes.
 

POLITICAL AND SEAWAY CONSIDERATIONS:
1. During the depression of the 1930s, the Grand Coulee Dam on the Columbia River was a major public works project in the USA. Today this dam provides 6.8 GW of load following electricity generation. The seasonal energy storage system contemplated herein offers comparable public benefits.

2. The seasonal energy storage system would cause the levels of Lake Ontario and Lake Erie to oscillate on an annual basis. It is envisaged that this water level swing would be increased 10 cm per year for Lake Ontario (8 cm / year for Lake Erie) and would be capped at 5 m for Lake Ontario and 3.8 m for Lake Erie after 50 years. That implementation time should be sufficient to allow owners of docks, marinas and seaway facilities to adapt to the lake level changes. During the implementation period the energy storage system would be operated as a blended daily energy and seasonal energy storage system to make best use of the facility subject to the agreed constraints on the change in lake levels.

3. The governments that would have to consent to the changes in lake levels and the related water recycling from Lake Ontario to Lake Erie are:
Canada, USA, Ontario, New YorK, Pennsylvania, Ohio and Michigan. The municipalities adjacent to the upper Niagara River and the Welland Canal would also be significantly affected.

4. It is anticipated that there might have to be minor changes to the Boundary Waters Treaty. It is further anticipated that there would have to be a long term agreement between Ontario and New York to allow the construction and operation of a canal pumping facility within Ontario that is directly connected to the electricity transmission system in New York.

5. During the late winter the level of Lake Ontario would be relatively low. During the late summer the level of Lake Erie would be relatively low. Some shipping channels, especially in Lake Erie, may require dredging to provide adequate keel clearance when the lake levels are low.
 

FEASIBILITY STUDIES:
It is contemplated that this project should proceed by way of three feasibility studies.
1. Overview Engineering study;
2. Detailed engineering study;
3. Detailed legal study.

The overview engineering study would be done by a small group of senior engineers each of whom has hands-on relevant experience with similar work. These engineers should list and realistically quantify and cost the major physical implementation elements to determine if the cost of any of these elements is so large as to prevent the project succeeding. It is contemplated that this study team would include at least one expert in each of the following areas:
Canal construction (Red River Floodway)
Control Gate construction (Thames Barrier)
Rock Fill Hydro-Electric Dam construction (BC Hydro, Quebec Hydro)
Great Lakes Dredging
Niagara escarpment geology (Rethink Technology, OPG)
Niagara escarpment power generation (Ontario Power Generation)
Major Pumping Systems (US Army Corps of Engineers)
Transmission Integration (OPA, Hydro One, New York Edison, Detroit Edison)
St. Lawrence Seaway operations

The detailed engineering study would proceed only if the overview engineering study indicates that there are no insurmountable technical or cost problems. The first phase of the detailed engineering study would identify the real estate requirements with sufficient detail to allow the detailed legal study to proceed.

The detailed legal study would address enabling modifications to the Boundary Water Treaty and all other legislative changes, expropriations and international agreements that are necessary to implement the project.

It is contemplated that all three feasibility studies would require 100% government funding.
 

This web page last updated March 14, 2014.

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