XYLENE POWER LTD.

SEASONAL PUMPED HYDRAULIC ENERGY STORAGE BETWEEN LAKE ERIE AND LAKE ONTARIO

By C. 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.

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 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 canals and at the pump inlets 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 equally 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 without US participation.

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

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 $3000/ kW X 10^6 kW / GW = $30 X 10^9
= $30 billion
It is envisaged that the project would proceed in four stages, at 10 year intervals. Each stage would cost about $7.5 billion. Each stage would involve the construction of a 30 km canal complete with associated control gates, 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. The seasonal energy storage would be shared equally between the USA and Canada.

3. The gravitational potential energy storage is:
M X G X Hd
where:
M = mass of water raised
G = gravitational acceleration = 9.8 m / s^2
Hd = difference in lake surface altitudes

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.

8. Thus a reasonable estimate of M is:
(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. The altitude of the surface of Lake Ontario is: 74 m

10. The altitude of the surface of Lake Erie is: 173 m

11. Hence Hd = 173 m – 74 m = 99 m

12. Thus the contemplated stored gravitational potential energy is:
M X G X Hd
= 97.625 X 10^12 kg X 9.8 m / s^2 X 99 m
= 94,716 X 10^12 joules
= 94.716 X 10^15 joules

13. The recoverable portion of this energy is:
M X G X Hd X (Hg/Hd) X Eg
where:
Hg = water head across the generator
and
Eg = generator efficiency.
Thus the recoverable energy is:
M X G X Hg X Eg
At Niagara Falls:
Hg = 89 m
and
Eg = .80
giving the recoverable energy per annum as:
M X G X Hg X Eg
= 97.625 X 10^12 kg/annum X 9.8 m / s^2 X 89 m X .80
= 68,119 X 10^12 joules/annum
= 68.119 X 10^15 joules/annum
= 68.119 X 10^15 watt-s/annum X (1kw / 1000 w) X 1 h / 3600 s
= 18.922X 10^9 kwh/annum
= 18922 Gwh/annum

14. 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 1892.2 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.

15. The additional water mass flow required to supply this 10 GW is:
97.625 X 10^12 kg / 1892.2 h
= 51.59 X 10^9 kg / h

16. Converting this mass flow into a volume flow gives:
51.59 X 10^9 kg / h X 1 m^3 / 1000 kg X 1 h / 3600 s
= 14.33 X 10^3 m^3 / s

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

18. Thus the new peak volume flow would be:
(14.33 + 5.7) / 5.7
= 3.51
times the present average Niagara River volume flow. Attaining this increase in peak river flow likely entails modification of the river bottom profile.

PROJECT REALIZATION:
1. In order to realize this energy storage system while taking maximum advantage of the existing Niagara River gorge and its 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. 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. The canals would require a robust control gates at both the Lake Erie and Lake Ontario ends. Building these control gates would require cofferdams. 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.

6. The exact locations of the control gates will be dictated by local topographic features and local depth to bedrock.

7. 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.

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 Hd) / Ep
Where:
Ep = pump efficiency = .75

2. The storage system efficiency is given by:
(recovered energy) / (charging energy)
= (M X G X Hg X Eg) / [(M X G X Hd) / Ep]
= (Hg X Eg X Ep) / Hd
= (89 m X .80 X .75)/ 99 m
= .539

3. A significant issue at Niagara Falls is keeping the generator head Hg as large as possible. Maximizing Hg is not easy due to practical difficulties of tunneling under the City of Niagara Falls. There might be merit in deepening the Niagara gorge downstream from Niagara Falls to reduce the required penstock tunnel lengths.

COST OF SEASONAL PEAKING ENERGY:
Assuming a simple payback period requirement of 7.34 years the cost of capital financing included in the cost of electrical energy recovered from seasonal storage is:
($30 X 10^9) / (18.922 X 10^9 kWh/year X 7.34 years)
= $.216 / kWh
The cost of the corresponding wind energy that went into seasonal storage at $.28 / kWh is:
($.28 / kWh) / 0.539 = $.519 / kWh
Hence the total cost of summer peaking energy recovered from seasonal energy storage is:
$.216 / kWh + $.519 / kWh = $.735 / kWh
and the annual average cost of electrical energy is:
[((2/3) X $.28) + ((1 /6) X $.735)] / (5/6) kWh
= $.371 / kWh

Another way of viewing this project is that if there is no seasonal energy storage the market value of surplus energy going into storage is zero. Then the cost of the seasonal peaking energy is only $.216 / kWh. However, in this case the cost of non-peaking energy is:
$.4179 / kWh
and the annual average cost of electrical energy is:
[((2/3) X $.4179) + ((1 / 6) X $.216)] / (5 /6) kWh
= $.377 / kWh

In either case $.37 / kWh is comparable to the cost of new nuclear electricity complete with load following energy storage. However, nucler requires less transmission and hence may ultimately be less expensive.

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 additional generation and related penstock tunnels in the proximity of Niagara Falls.

This document outlines a large project that can be built in several 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 proposed Lake Erie-Lake Ontario pumped storage project is that it offers a large amount of seasonal energy storage located close to major electricity markets. There is very little flooding due to formation of new lakes.

POLITICAL AND SEAWAY CONSIDERATIONS:
1. At this time in early 2010 North America is still in a severe economic recession. 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. On January 20, 2009 Mr. Barack Obama became president of the USA. In his inaugural address he stated “we will harness the sun and the winds to fuel our cars and run our factories” and further stated “we will work tirelessly to lessen the nuclear threat and to roll back the specter of a warming planet.” Large scale seasonal pumped hydraulic energy storage is one of the key technologies for achieving these objectives. Within our lifetimes there may never be a better time to seek political and financial approval for this pumped storage project.

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 4 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 would 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 US 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 low. During the late summer the level of Lake Erie would be 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 any of these elements could 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 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 January 15, 2010