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HomeMy WebLinkAboutHarnessing Cook Inlet's Tidal Activity 1975ROY W. JOHNSON Consulting Engineer 2716 Fairview Avenue East Seattle, Washington 98102 (206) 323-3150 "HARNESSING COOK INLET'S TIDAL ACTIVITY" (A Tidal Power Possibility) As presented to REGIONAL CONVENTION THE CONSTRUCTION SPECIFICATIONS INSTITUTE Anchorage, Alaska August 22 and 23, 1975 Roy W. Johnson Consulting Engineer Seattle, Washington ALASKA POWER AUTHORITY LIBRARY COPIES PLEASE DO NOT REMOVE! ! ° wees wre Sb > wt ROY W. JOHNSON Consulting Engineer 2716 Fairview Avenue East Seattle, Washington 98102 (206) 323-3150 "HARNESSING COOK INLET'S TIDAL ACTIVITY" (A Tidal Power Possibility) As presented to REGIONAL CONVENTION THE CONSTRUCTION SPECIFICATIONS INSTITUTE Anchorage, Alaska August 22 and 23, 1975 Roy W. Johnson Consulting Engineer Seattle, Washington ALASKA POWER AUTHORITY LIBRARY COPIES PLEASE DO NOT REMOVE! ! ROY W. JOHNSON Consulting Engineer 2716 Fairview Avenue East Seattle, Washington 98102 (206) 323-3150 HARNESSING COOK INLET'S TIDAL ACTIVITY It is estimated, using basic data from United States government navigation charts, geodetic survey maps, and tide tables, that approximately one million kilowatts of continous power can be obtained from tidal activity in Cook Inlet if harnassed at Fire Island. Another million kilowatts can be obtained half of the time. In the opinion of this writer, the development possibilities should be explored in depth to establish the competitive position of this inexhaustible source of non-polluting energy to help satisfy an apparent insatiable market. Incidental benefits to accrue from the development include direct vehicular access from Anchorage across Turnagain Arm to the Kenai Peninsula, and acress Knik Arm to the Susitna River delta and beyond. Both of these regions contain vast treasures of natural resources. Other benefits will be discussed, but not the least are the possibilities of having established in the greater Anchorage area at tidewater, a complex of electro-metallurgical and electro-chemical industries to process at least some of Alaska's mineral wealth. These, in turn, make it possible to engage in secondary manufacturing. . Realizing that all of the elements of an industrial complex do not necessarily fall into place simultaneously it is suggested that the surplus energy be applied to the production of hydrogen for which there is a good market. Page 2 BASIC PRINCIPLE The principle upon which the harnassing of tidal activity is based is very simple. If an estuary such as Knik Arm is dammed off with a barrier, the difference in water surface elevation on either side of the dike will enable power to be produced. In Northern France a single-basin tidal power project recently was completed on the Rance Estuary in Brittany, to produce up to 20,000 kilowatts whether the flow is upstream or downstream. Of course, there are periods when the water surface elevations are equal, or nearly so, and power pro- duction is interrupted. Contimous power, on the other hand, can be obtained where it is physically possible to have two basins side by side. The water surface of one would be maintained at a maximum elevation by the opening of control gates at high tide. The surface of the other would be maintained at minimum elevation by the opening of control gates at low tide. Power would be produced as the water flows through turbines from the high basin to the low one. COOK INLET PROJECT If barriers are constructed none Point Campbell and Fire Island, and from Fire Island across Knik Arm to the Susitna River flats, and from Fire Island across Turnagain Arm to the Kenai Peninsula, two shallow-depth basins are possible. Knik Arm would become the high basin and Turnagain Arm the low one. The generating units would be installed in the barrier between Point Campbell and Fire Island as indicated on the attached maps. Page 3 Since this project first was proposed twenty years ago, the French developed and produced a submersible bulb-type turbine-generator which is generally more efficient and less costly for low-head installations. It is used at the Rance Estuary installation and in run-of-the-river low head projects. The metal encased generator on a horizontal shaft is directly connected to a variable-pitch propellor. The pitch of the blades is adjusted to maintain a constant speed as the water head varies. Previously nearly all low-head hydroelectric installations involved vertical shafts so that the generators could be operated in the dry, above any flood possibility. Surface observation indicates that Fire Island and the lands upon which this project is proposed consist, for the most part, and probably all, of ‘glacially-deposited till and water-deposited silts. Test borings are needed to ascertain the depths at which various strata appear and where rock, if any, will be encountered. The flats between Point Campbell and Fire Island (three miles in length) are fully exposed at low tide so the power plant portion may be constructed in the dry. Whether any portion of this section needs to be supported on piling is yet to be determined. A cut-off wall of sheet piling, perhaps, probably will be needed to protect the foundations from tail race scour. : The maximum depth across Knik Arm (six miles in length) is 70 feet below mean lower low water for a short distance, and more than half the distance is exposed at low tide. At the Turnagain Arm crossing (seven Page 4 miles in length) there is a pocket 75 feet deep south of Fire Island. North of Point Possession, for a short distance, the maximum depth is 110 feet. Because of the nature of the soils it is believed that the tidal gate structures can be built in a graving dock and be floated into Place atop sheet-pile cells driven and cut-off to elevation in the wet. This possible construction procedure is graphically illustrated on one of the attachment sheets. It is assured that miter gates as used in a ship lock will be provided. Future investigation will determine whether tainter or roller gates will prove to be equally, or more suitable. OTHER FUTURE INVESTIGATIONS To authoritatively determine the feasibility of developing power from the tides of Cook Inlet, a rather extensive program of investigation should be pursued. Some additional mapping and soundings will be required. It will be necessary to drive test piles and analyze samples of soils taken at.various depths. ‘It undoubtedly will be necessary to construct a@ working hydraulic model to obtain certain basic factors that can be utilized in a computer analysis of the many variable conditions as will obtain. The results should establish the number of gates required to control the large flows of water and what effect, if any, the barriers will have on the height of the tides. These studies also will enable one better to pre- dict problems of erosion and siltation and the effect of the project on ice flows. TIDAL VARIATIONS The tides at Anchorage vary from a high of plus 36.0 feet to a low of minus six, and the mean range of the tides is 26.7 feet. At Fire Island the highest tide goes to plus 33.0 feet and the mean range of every tide is 24.6 feet, a little less. The.extremes occur at the new and full moons, and the minimum tides occur at the quarter moons. Page 5 The higher tidal range at the City Dock in Anchorage is believed to be the result of tidal surges in and out of Cook Inlet. The surge effect is illustrated by the fact that the highest tides, while reaching a maximum of elevation of 36.0 feet at Anchorage, go considerably higher near Palmer at the north end of Knik Arm. In the southerly direction from Anchorage the highest tide is 33.0 feet at Fire Island, and gradually reduces to 24.0 feet at Homer near the entrance to Cook Inlet. It is possible that the dikes, after construction, will interfere somewhat with the surge of the tides, and reduce the tidal range. The mean range of tide for the Rance Estuary project in France is reported to be 28 feet. POWER PRODUCTION Attached hereto are duration curves showing the amount of power as can be produced at various constant rates of flow, assuming an overall plant efficiency of 85 percent. They are based on tide tables as were available at the time for Anchorage. The month of June, 1945, was arbitrarily selected. The maximum continuous output at variable flow computes to be 1,200,000 kilowatts, and two million half of the time. The continuous power rating of the project is reduced to one million kilowatts on the deduction that the tidal range at Fire Island is less than at Anchorage. ADVANTAGES OF COOK INLET TIDAL POWER As compared to run-of-the-stream-river developments, there are no seasonal flood peaks or low periods of drought with which to contend. The availability of firm power is as dependable as the moon. Page 6 The shallow depths of water preclude the construction of high parriers, and the apparent absence of bedrock aids the construction of sheet pile cofferdams and foundation structures. No long distance high-voltage transmission system will be needed as the energy, for the most part, will be consumed at tide water near the source of supply. The troublesome movement of floe ice in Knik Arm will be reduced. It is reasoned that ice will tend to congeal toward the head of the arm. Silt in the water can be expected to be reduced by reason of decreased water velocity. The project is expected to have a minimal adverse impact, if any, on the environment. Direct highway and, possibly, rail access across the two arms can be achieved. Anchorage shipping is improved by reason of reduced tidal range and drifting ice. ECONOMICS When it was learned some years ago that Cook Inlet rests on top of important gas and oil fields, it was deducted that tidal energy would not be feasible for the limited power market as presently exists in the Anchorage area. This is due to the relatively greater cost per kilowatt of installed hydroelectric capacity as compared to the unit cost of gas turbo-generators and fueled by low cost gas. A further advantage of fuel- fired generation was that capacity could be installed incrementally as needed, thus limiting the outlay of capital. Page 7 All of that has changed drastically during the past year. The price of natural gas and oil is being multiplied and restrictions are being placed on its use. The dwindling supply is expected eventually to be limited to home heating, transportation fuels and as feed stocks for petro chemicals and fertilizers. The hydrogen and oxygen as would be produced from electrolysis of water in this energy thirsty era, have an existing and potential market in the gasification and liquifaction of coal. For example, when hydrogen is combined with the hot gasses from heated coal, methane (CH) is formed, ready for the pipeline. A few miles to the south of us at Kenai ammonia for fertilizer is produced in large quantities utilizing local natural gas for its source of hydrogen. It would be interesting to ascertain the competitive position of electrically produced hydrogen for such an operation after price controls are lifted. When the costs of Cook Inlet power are known there is reason to be- lieve that aluminum producers, for example, could become interested. Bauxite ore could be shipped to Cook Inlet, perhaps from Australia, for reduction to alumina using Alaskan coals and then electrolytically to aluminum. And prospectors may well find such ores in Alaska if they haven't already done so. Alcoa at one time was prepared to place an aluminum smelter at Taiya near Skagway had Canada been willing to allow diversion of some of the headwaters of the Yukon River for hydro power generation at sea level. RANCE ESTUARY PROJECT The Rance is a coastal river flowing into the English Channel be- tween St. Malo and Dinard in northern France. This single basin project Page 8 was completed in 1967 and cost 122 million dollars. The maximum tidal variation is 44 feet and 28 is the yearly average, about the same as Cook Inlet. The power plant houses 24 generating units of 10,000 kilowatts each. They are totally submerged bulb-type units on horizontal shafts with variable pitch turbine blades as can operate in either direction of flow. 537 million kilowatt hours are produced annually as the water flows to the sea, and 71.5 million kilowatt hours when flowing from the sea to the basin. Being connected to the French power grid the turbines also operate as pumps to increase the amount of water stored in the basin at times of tidal change. This consumes 64.5 million kwh so the annual net production is 544 million kilowatt hours. This reduces to an average production of 62,100 kilowatts, making the plant factor .26, which is rather low. With a reported cost of 122 million dollars, 240,000 kw installed, and a plant factor of .26, the equivalent cost per continuous kilowatt is $2,000 at 1967 prices. PASSAMAQUODDY This project located between Maine and New Brunswick on the Bay of Fundy was first investigated in depth in 1935 when Franklin Roosevelt was President. It was reviewed again in 1963 under the encouragement of President Kennedy but was found to be not feasible under conditions as then prevailed. It is a two-basin project with the high pool being Pass amaquoddy Bay in Canada and the low pool Cobscook Bay in Maine. Its ultimate capacity is reported after the 1963 investigation to be 1.75 million kilowatts and was estimated then to cost 1 billion dollars. There are a series of dams to be built on rocky bottom aggregating 7.5 miles ae Page 9 of concrete. The water depths were not reported in the technical journals readily available. The tidal range varies from a maximum of 26 feet to a minimum of 12.7 feet. The average range is 18.1 feet. The cost was reported to be in the order of 1.5 billion dollars in 1973 and probably more like two billion today. Assuming a plant factor of .9 for Passamaquoddy, the cost per installed kilowatt of equivalent continuous power is in the order of $1,270. ROCK ISLAND POWERHOUSE EXPANSION The Chelan County Public Utility District in Washington received bids on August 8, 1975, two weeks ago, for construction of a 410,000 kilowatt expansion to its power plant on the Columbia River. Previously it awarded a contract for 8 bulb-type turbine-generators of 51,250 kilowatt capacity each to Neyrpic, Inc. of Grenoble, France for 46.7 million dollars. This is the firm which developed the turbines in service at the Rance Estuary. Rock Island is the first application of bulb-type units in North America. The head is reported to be 36-38 feet, and the increase in unit capacity from 10 Mw to 51.25 Mw at Rock Island is rather significant, although in the latter case there is a greater head. The cost of the delivered generating units is $144 per kilowatt. The project engineer advises that the estimated cost of the completed power house is $150 million, or $366 per kilowatt. The load factor is not known. This capital cost figure is a measure of what the power house portion of the Cook Inlet project might cost. For present purposes, let us call it $500, a round figure. Page 10 PROBABLE COST OF COOK INLET POWER In the opinion of this writer the construction of tidal barriers and gates at Cook Inlet is less onerous than at Passamaquoddy. At the latter site everything will need to be constructed in the dry with ex- tensive use of cofferdams. At Cook Inlet, if the soils, as believed, are somewhat impervious and will permit the driving of piles, a substantial savings in cost can be anticipated. Let us assume that the cost of tidal barriers and gates will aggre- gate 500 million dollars. We then have the following: Installed capacity 1000 Mw 2000 Mw Cost of power plant at $500 per kw $ 500,000,000 $1 ,000 ,000 ,000 Cost of barriers 200,000 ,000 200 ,000 ,000 Total cost of project $1,000 ,000 ,000 $1,500 ,000 ,000 Cost per kilowatt $1,000 $ 750 Plant factor 1.0 0.9 Equivalent cost per continuous kw $1,000 $ 833 Let us next assume that the project can be financed with federal funds with a payout period of 40 years at 8 percent interest. In this case principal and depreciation are assumed to be synonymous: Amortization per kw ($1,000) $ 83.86 Supervision and engineering 1.20 Supplies and expense 1.00 Maintenance 4.00 Station labor 4.00 Total cost per kilowatt year $ 94.06 Cost per kilowatt hour 94. 06/8760 1.075¢ Contingencies, 10% -108 west aera Page 11 CONCLUSION The above is believed to be a reasonably conservative "ball-park" estimate of the cost of Cook Inlet tidal power. In the writer's opinion it is reasonable and competitive with other sources of large quantities of power, realizing , too, that very little hydro power at low cost remains undeveloped. Cook Inlet power is non-polluting and is ecologi- cally sound. The cost-to-benefit ratio is believed to be high, and not the least of the benefits are the direct highway routes on the barriers to the Kenai Peninsula and the Susitna River delta areas; also improve- ments to shipping. It is recommended that funds be made available for exploration. Our country needs the energy. as Proposep by Roy W. Johnson CONSULTING ENGINEER ARCTIC BLOG. SEATTLE, WN. i PROVIDES YEAR ROUND PORT FACILITIES 1054 DIKE & TIDAL GATES Z i 6 MILES LONG \\ as . | 3 ; ANCHORAGE aig INTERNATIONAL INDUSTRIAL SITES | htc | AIRPORT i “AY et oe Tie A PES k Ir ano yee LFS co, ft / < | oan Age Bronce & DIKE 3 MILES Witt ALA 1,000,000 KW CONTINUOUS POWER “f° 2,000,000 KW HALF TIME POWER me AR « PENINSULA PNEUMATIC CONCRETE CELLS TIDAL GATE Vicinity Map CONSTRUCTION TIP 0079 Cook Inlet TIDAL as PROPOSED by 7 Roy W. Johnson CONSULTING ENGINEER 3 ARCTIC BLDG. 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