Agei-ilvEs FISHERIES RESEARCH BOARD OF CANADA. Translation Series No. 2836

Transcription

1 Agei-ilvEs FISHERIES RESEARCH BOARD OF CANADA Translation Series No Waste heat from thermal power stations can give possibilfties for economically feasible aquaculture by Ole Devik Original title: Spillvarme fra varmekraftverk kan leinnsom akvakultur i muligheter for From: Teknisk Ukeblad, 120 (33) : 5,7,9-10, 1973 Translated by the Translation Bureau(pmj) Multilingual Services Division Department of the Secretary of State of Canada Department of the Environment Fisheries Research Board of Canada Biological Station St. Andrews, N.B pages typescript

2 'DEPARTMENT OF THE SECRETARY. OF STATE ' TRANSLATED FROM - TRADUCTION DE Norwegian AUTHOR - AUTEUR Ole Devik, Ph.D. TRANSLATION BUREAU MULTILINGUAL SERVICES DIVISION CANADA INTO - EN English SECRÉTARIAT D'ÉTAT BUREAU DES TRADUCTIONS DIVISION DES SERVICES MULTILINGUES F A TITLE IN ENGLISH - TITRE ANGLAIS Waste heat from thermal power stations can give possibilities for economically feasible aquaculture TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGÉRE (TRANSCRIRE EN ÇARACTkRES ROMAINS) Spillvarme fra Varmekraftverk kan gi Muligheter for lo si nnsom akvakultur REFERENCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE FOREIGN CHARACTERS. RÉFÉRENCE EN LANGUE ÉTRANGÉRE (NOM DU LIVRE OU PUBLICATION), AU COMPLET, TRANSCRIRE EN CARACTbZES ROMAINS. Tekn. Ukebl (33):5,7,9,10. (August 9th) REFERENCE IN ENGLISH - RÉFÉRENCE EN ANGLAIS Tekn. Ukebl (33):5,7,9,10. (August 9th) PUBLISHER - ÉDITEUR Chr. Michelsens Institutt, Nygârdsgt. 114, 5000 Bergen PLACE OF PUBLICATION LIEU DE PUBLICATION YEAR ANNÉE DATE OF PUBLICATION DATE DE PUBLICATION VOLUME ISSUE NO. NUMÉRO PAGE NUMBERS IN ORIGINAL NUMÉROS DES PAGES DANS L'ORIGINAL 5,7;9 ; 10 Bergen (33) 16 NUMBER OF TYPED PAGES NOMBRE DE PAGES DACTYLOGRAPHIÉES REQUESTING DEPARTMENT Environment TRANSLATION BUREAU NO MINISTÈRE-CLIENT NOTRE DOSSIER NC) BRANCH OR DIVISION DIRECTION OU DIVISION Fisheries Services TRANSLATOR (INITIA LS) TRADUCTEUR (INITIALES) PMJ PERSON REQUESTING DEMANDÉ PAR Mr. A.T. Reid DEC YOUR NUMBER VOTRE DOSSIER NC) DATE OF REQUEST 23^ DATE DE LA DEMANDE SOS (REV. 2/88)

3 DEPARTMENT OF THE SECRETARY OF STATE TRANSLATION BUREAU SECRÉTARIAT D'ÉTAT BUREAU DES TRADUCTIONS MULTILINGUAL SERVICES DIVISION CANADA DIVISION DES SERVICES MULTILINGUES CLIENT'S NO. DEPARTMENT DIVISION/BRANCH CITY NO DU CLIENT MINISTERE DIVISION/DIRECTION VILLE Environment Fisheries Services Ottawq, Ont. BUREAU NO. LANGUAGE TRANSLATOR(INITIALS) NO DU BUREAU LANGUE TRADUCTEUR ( INITIALES) Norwegian PMJ ;` ';;,à Spillvarme fra Varmekraftverk kan gi Muligheter for lônnsom akvakultur Waste heat from thermal power stations can give possibilities for economically feasible aquaculture by 01e Devik,'Ph.D. Chr. Michelsens Institutt, Nygârdsgt. 114, 5000 Bergen. Tekn. Ukeb (33):5,7,9,10. (August,9th) (This article is based on a talk given at the Chemical Engineers' Group, Oslo Section in April 1973). Waste heat from atomic and thermal power stations is, to many people, equal:. to pollution. But used properly, possibly together with,waste water P-5 from populated areas, it can creaté possibilities for economically feasible rearing of both plants and delicacies such as salmon, lobster and oysters. SOS

4 2 Cooling water frôm'pôwèr'stàtiôris èxèrt â côrisidéràblé lôàd"ôri rivérs such as the Rhine. Large quantities of heat must be removed if a sizeable thermal or atomic power station is to be built. In Fig. 1 it can be seen how the energy balance for a 1000 MW power station is calculated, and Fig. 2 shows the consequences of building many such large power stations on a recipient of a relatively limited size. The conditions are much better, however, Fig. 3,if ocean water is used as a coolant. How will the conditions be in Norway? Using the known average water temperature along the coast in Southern Norway, it appears that the cooling water temperature can be expected to vary between 11 and 27 C if the cooling water intake is located near the surface. By utilizing deeper water layers p. 7 with more even temperature conditions, the expected temperature variation would be in the range of C with a maximum relatively late in the year. Considering all conditions that must be considered, it is very difficult to find general statements regarding the changes and possible damaging effects that can be expected as a result of such a release of heat. In the available literature several examples are given where it is shown that a moderate increase of the temperature (1-3 C) can at times result in considerable changes in species conposition and occurrence, but that no so-called catastrophies have occurred due solely to a temperature increase of this magnitude. It is also not an unknown phenomenon that relatively small temperature changes result in large changes in species distribution in the natural environment, but that these changes often disappear if the temperature returns to the original value.

5 3 Fig. 1 ENERGY BALANCE Electrical Waste Power Heat Energy Coal: 6100 tons/day ) Or Oil: 4900 tons/day ) 1000 MW 1500 MJ/s 0.5 M Nm/s U235: 24 grams/day 1000 MW 2000 MJ/s 0.7 M Nm/s Fig. 1 When the energy balance is evaluated, it is natural to base it on the second law of thermodynamics which says that when converting latent chemical energy by a combustion process to electrical energy, thermal energy (heat) is formed which cannot be changed, but must be removed by transferring it to neighboring systems. The proportion of waste heat will here depend on the operating temperature, but will always form a considerable part of the total energy budget for a thermal power station. This figure shows how the conditions will be at a 1000 MW power station. (The nomenclature MJ/s is used to indicate that this is thermal energy).

6 4 Fig. 2 The Rhine, water flow 1500 M 3 /s Calculated.water temperature in July 1985 Installed effect MW without cooling tower. (From J. Tinker 1972) Basel 40 - V OC Strasbourg Mannheim Koblenz Kôln V V V V C Natural Temperature., km Distance from Outlet Fig. 2 The consequences in a limited water course can be vety large. This diagram shows the expected temperature increase in the Rhine in 1985 when MW has been installed. It can be seen that the temperature will increase far above 28 C, which is considered responsible based on the tolerance of the organisms living in the Rhine. It should also be noted that international conventions have been drafted limiting the temperature increase from individual power stations to 3 C and to an outlet temperature not exceeding 28 C. Another consequence is that the oxygen content will drop drastically since the solubility of oxygen decreases ca. 1.6% for each degree rise in the temperature. Together with increased consumption of oxygen due to higher rate of decomposition of organic materials, it is expected that a sharp decrease in the oxygen content will result, and probably also oxygen depletion in large areas.

7 5 Increâsed tempéràtùré 'résùlts iri iricréâsèd grôwth. The most important effects on the various organisms are due to the fact that these are dependent on the temperature of the environment (except for mammals). This means that an increase in temperature results in an increase in various metabolic processes and also in reactions to stress. The following consequences can therefore be observed: - The metabolic processes of the primary production of phytoplankton are increased and larger quantities of organic carbon are therefore taken up per unit time. - A higher rate of combustion of the organic material increases the oxygen consumption and where there is a slow exchange of water, this can result in a complete elimination of oxygen. - A more rapid fixation of heavy metals in phytoplankton can be envisioned and this can result in increased enrichment in higher levels of the food chain. - The increase in temperature stimulates activity and growth also in later links of the food chain and higher yields in the forms of fish and shellfish. - If plant nutrients are not added, a greater self-purifying effect can be expected. - An increased temperature in closed water courses can improve the possibilities for recreation (swimming). - Aquaculture utilizing organisms preferring higher temperatures can become an actuality, and the metabolic processes will also increase for locally acclimatized organisms. (This means a definite improvement in the economic situation).

8 6 - In addition, there could also be other local effects as for instance a greater tendency to fog formation due to increased evaporation. - Good possibilities for rearing of fish, shellfish and plants. From the points mentioned above, the evaluation of damaging effects will depend on the definition of these effects. If the final criteria of these evaluations are based on the resultant effects being irreversible and extensive in area, the conclusions are: Damaging effects in Norwegian waters will be small since the possibilities for an effective mixing of the cooling water in the currents of the coastal waters are good and because it can be relatively easily arranged to utilize large volumes of water. The temperature increase of ca. 10 C will drop rapidly after suitable dilution, and damaging effects would not be expected even in the area fairly close to the plant, although there could be large changes in the species composition and animal life. Changes in an area further away will depend on the local wind and current conditions, but by utilizing the natural mixing conditions, the temperature increase in this area can be kept below 1 C, and thereby cause effects that are measurable, but can hardly be called damaging. A much more positive attitude is, however, that if the thermal effect is to be utilized, considerable beneficial effects can be obtained in aquaculture.

9 7 Fig. 3 Temperature increase following various types of dispersion of cooling water Morro Bay. 850 MW, 30 kbm/s (Edinger and Polk, 1971) AT AT0 1.0 al da Fig. 3 An installation in Morro Bay, California, releases its cooling water in the Pacific. The power rating is 850 MW, quantity of cooling water is ca. 30 M 3 /s with 10 o C temperature increase in the condensers. At this cooling water temperature it is found that the temperature increase in the release area has fallen to 50% of the original value within an area of 3000 M 2 and to 10% within an area of 100,000 M 2 (Fig. 3 from Edinger and Polk, 1971). An increase in the amount of cooling water to 200 M 3 /s can lead to an increase of the heated area of from 20 to 300 times according to how deep the surface mixing penetrates. Areas with a 1 o C temperature increase relative to the surroundings can then vary from 2 to 30 km 2. The criteria for these beneficial effects will be to see if the input in the form of capital and energy (feed, fertilizer,

10 8 light are all counted as energy) will be in relation to the yield that can be obtained from increased productivity. Yield is defined from the point of view of people, while the term p. 9 productivity refers to the total a-mount of biomass produced, and this will always be considerable greater than the quantity people can utilize for their own benefit (Fig. 4). From a technological evaluation, the three first alternatives (possibly also the fourth) can be carried out. The first two cases will be based on net enclosures preventing the fish from escaping, and stopping other fish from entering to eat the feed and the reared fish. Enclosures of this type with feeding equipment are already available. For the third alternative it must be assumed that the natural concentration of growth nutrients is too low to secure maximum growth of shellfish and/or fish so that fertilizer must be added over a large part of the year. It is then required of the enclosure that it is so constructed that the nutrients are kept back at least for four to six days until they. are assimilated in plankton or plants. This presumes the use of special "hothouse" construction. The fourth alternative, growing higher plants, is practically possible only if new methods are developed. From biological and resource considerations the last two alternatives are the best since they will give the highest yield in the water volumes occupied, especially when considering the extra production areas (volumes) required for feed production to secure intensive rearing. Our economic knowledge is too incomplete to draw definite conclusions, even if the results of the Norwegian pondfish operations show that there is reason for optimi.sm for the future of fish rearing.

11 9 Salmon, lobster and oyster - important prodùcts. The sale of shellfish is at the present time so limited that an estimate of the future is only valid if increased sales can be obtained. Regarding the economic estimates, the important question will be to find out if it is possible to improve the yield enough by increasing the temperature in order to compensate for the increased capital investments. As seen in the tables in Fig. 5 and Fig. 6, rearing of both salmon and oysters justify their capital costs. In the production of fish, it is seen that utilization of heated water will be limited to the rearing of the high-priced species (salmon, flounders and eel in addition to lobster). Lobsters are of special interest, since experiments in the U.S.A. have shown that they can be reared to commercial size(450^ in a period of ca. 20 months. In the long haul it is not certain if salmon is the best fish species to concentrate on since there are so many areas along our coast with good rearing conditions without using heated water. P. 10 The other fish species will represent relatively small quantities in the beginning and it is therefore assumed that most of the heated water will remain un-utilized if fish rearing is the only form of utilization. For that reason, aquaculture of both shellfish and plants is of primary interest. The production of shellfish will be limited to oysters and possibly also scallops. There is not much information available on scallops, but our local varieties have a long growth period to commercial size of from five to seven years. Scallops with considerable

12 10 faster growth can be found in the warmer zones, and it is therefore not unrealistic to assume that these shellfish coldd be reared in Norway, although on the relatively long haul. The possibilities are still worth discussing, especially since the same factors will be limiting for the shellfish production as for the production of higher plants. Integrated production gives best results. With operations of this type the whole food chain is involved, starting with the supply of light, minerals and sufficient heat. From these a usual food chain will develop where plankton grow on the basis of available mineral nutrients and light and the shellfish (as one of the many grazing organisms) utilize the phytoplankton production. In an ideal situation the waste materials from the shellfish will be mineralized and the minerals returned for renewed utilization. In a production of this type, light will be the limiting factor in four of the months of the year and the rest of the year the mineral supply will be limiting. The cooling water will contain sufficient nutrients only for a limited time of the year and mineral nutrients must therefore be supplied either as fertilizer or in the form of treated sewage. This latter possibility is especially interesting since preliminary estimates indicate that the composition of such effluent water is favorable. It is, however, important ot make sure that the shellfish harvested are free of infections and contaminants that could come from the sewage. An aquaculture utilizing these possibilities is shown in Figure 7.

13 11 Fig. 4 Input Energy Capital Yield Type of Production Volume of Enclosure Fat & Protein Feed purchase Salmon Intensive Enclosure Juveniles for Stocking Flounder (plaice) Eel Rearing Small Lobster Commercial Feed Purchase of Feed Carp Intensive Small Enclosure Tilapia Rearing (Fry) Mullet and Others Light Enclosure Shellfish Extensive Large Minerals (Fry) Carp Rearing Tilapia Mullet and Others Light Enclosure Harves table Large Minerals (Seeds) Plants Fig. 4 The production of fish, shellfish and plants can be increased to a considerable extent if the water temperature is increased. But capital is also required, energy in addition to heat must be added and care and maintenance included. And as in all forms of economic utilization, the productive areas must be enclosed to obtain control of both productivity and yield.

14 12 Fig. 5 NORMAL TEMPERATURE INCREASE 2-4 C Feed Stocking fish Wages Maintenance Norw. kr. 8, - 8, - 2,40 1,20 3, - 2,50 2, -- 1, - 15,40 12,70 Price fob 20, - 20, -, Dekningsbidrag (?) = Subsidy (?) Grant? 4,60 7,30 Investment 20, - 20, - Years for recovering investment 10 5,6 Yearly production per 100 M3/s Enclosed volume 2400 tons 360,000 M3 (Corresponds to ca. 20 da) Fig. 5 Salmon. Estimated production costs in Norw. kroner per kg with and without heated water.

15 13 Fig. 6 NORMAL TEMPERATURE INCREASE 2-4 C Fry (spat) 1, - 0,80 Wages 2,30 1,70 Packaging 2,90 2,90 Maintenance 2, - 1,50 8,20 6,90 Price fob 15, - 15, - Dekningsbidrag=Grant, Subsidy(?) 6,84 8,14 Investment 15, - 11,40 Years to recover investment 7 5 Fig. 6 Shellfish (oysters). Estimated production costs in Norw. kroner per kg. with and without heated water. So far there are few examples of the utilization of higher aquatic plants. We know from the Spanish conquest of Mexico that there were floating islands on the large saltwater lake Tenochtitlan where the natives grew various crops. These floating islands were formed by placing earth on top of branches etc; they were anchored near the shore, but gradually sank and became fastened to the bottom.

16 14 It is, however, not as simple in Norway. For us it will be especially important to have enough heat in the growth areas. The heat transfer conditions must be such that the heat gets to the layers where the plants grow. This can probably be done partly by keeping a relatively thin plant layer where the temperature drop is concentrated over the upper layers and partly by using a thin layer of plastic on the top in order to obtain a fairly reasonable surface temperature. It must be admitted that these aspects still require a long time to come to fruition until a system satisfying both the requirements for plant yield and mechanical handling can be found. It is, however, a line of development that should be followed with great interest. Aquaculture alternatives must be included in the planning. As we have seen, waste heat has pqssibilities for giving a positive contribution to the production of both fish, shellfish and plants. If this resource is to be utilized, those who plan the future power stations must take the following conditions into account: - The cooling water effluent to be utilized for rearing must be controlled both in quantity and temperature. This can be done by using alternate outlets so.that a certain mixture can be obtained. - The cooling water outlets must be located so that there is a reasonable protection against wind and rough weather, for instance, by not having a'yetch'(stretch?) of more than 4-5 km in the most exposed wind direction.

17 15 - That the current conditions at the outlet are such that the effluent is led out to deep water with good mlixing. - That there is a certain supply of fresh water. The necessary freshwater layers for floating "hothouses" can thereby be built up and a controlled addition of fertilizer or of biologically treated sewage can be practiced. If these principles are taken into consideration, the possibilities that axist for utilizing the quantities of waste heat available are recognized without going outside the narrow margins required when operating the power station at optimum heat utilization. Fish rearing seems to present the immediate best possibilities while possibly shellfish and plant production will be of greater importance in the longer haul. In these production forms the natural production of nutrients in the area are utilized and the production potential can be improved by adding plant nutrients in the form of for instance, domestic sewage effluent. Through suitable "hothouse" constructions this is technically possible even if the solution is not yet available. With a reasonable effort these can, however, be available in time to be utilized in connection with the building of the first Norwegian thermal power stations.

18 16 quvyt;^^ Fig. 7 i Cooling water ^^ i t =`--- 7 * Fresh water m /s m 3/ d ay s - _^. '" Plastic Rearing of Skirt ^ Shellfish ' (400m ^ in ds.ameter Rearing of fish Fig. 7 Installation for the rearing of shellfish and fish. The cooling water is here utilized indirectly in that it is led around a large basin in which the aquaculture is carried out. The water in this basin is kept inside a_shallow plastic skirt by layering over freshwater. The horizontal exchange is thereby eliminated. When regulating the freshwater installation properly, it has been shown in models (6-8 M in diameter) that the water added has a retention time of from four to thirty days in the upper layer. This also means that added plant nutrients will remain for a sufficiently long time within the enclosure to be utilized. The shellfish culture itself is carried out on baskets hanging from rafts. This technology is relatively well known..