Air-Cooling Towers To Combat Greenhouse Effect
Ecological Effectiveness of Thermal Power Plants To Be Enhanced Through Innovative Technologies
Anthropogenic burning of air oxygen results not only in atmospheric discharges of greenhouse carbon dioxide, but also to the creation of greenhouse water vapors. This occurs through the oxidization of hydrocarbon fuel and through wide-spread systems used for evaporation cooling of industrial water to flush excess heat from power plants operating on organic fuel. In this sense, even nuclear power plants are not devoid of this drawback, although they are deemed to be fairly ecologically clean from the point of view of spewing greenhouse gases.
Nowadays, the greenhouse effect is attributable to water vapors by approximately 78 percent and only by 22 percent is it determined by carbon dioxide gas. This means that in the near-earth atmospheric stratum, where the greenhouse effect actually builds up, 10 weight parts of water vapor, creating 78 percent of the greenhouse effect, bear one weight part of carbon dioxide gas, which creates, however, 22 percent of the greenhouse effect. Nevertheless, one weight part of carbon dioxide is 2.82 times more prodigious in creating the greenhouse effect than one weight part of water vapor. From the above-stated it would be easy to determine the aggregate input of water vapor and carbon dioxide into the greenhouse effect for various power plants (See table).
Instead of using water to divert the “spillover” heat at electric power stations, air cooling will be used (“dry” cooler towers), then for coal-based thermal power plants (TPP) the aggregate “greenhouse effect” (minus efficiency changes), in CO2 equivalent will amount to 505 (77.5%)+146.5 (22.5%) = 651.5 (100%) g per kW-hour; for nuclear power plants (NPP) the aggregate “greenhouse effect” in CO2 equivalent will amount to 0 (100%) g per kW-hour.
Water Vapor as Factor of “Greenhouse Effect”
Thus, ignoring the input of water vapor in the production of electricity at thermal power plants and nuclear power stations leads to the negation of 22.5 % to 100% of man-induced input of those power productions into the “greenhouse effect”. Therefore, it might be argued that the methods, used in monitoring anthropogenic gas discharges into the atmosphere, causing direct “greenhouse” impact on the Earth’s atmosphere, based on the accounting of fuel and energy source consumption at enterprises and organizations of varying forms of ownership, but ignoring the anthropogenic discharges of water vapor, these methods do not appear sufficiently effective in view of regional and global changes in climate.
Presently, payments or natural water consumption constitute a negligible part in the prime cost of power production, as they don’t take into account the impact of vaporization-induced cooling on a region’s climate.
Last summer, due to overwhelming heat, Europe, one of the world’s most thriving continents, became a region suffering from water shortages. An unprecedented shallowing of its numerous rivers last year led to more than 20-fold price hikes on electricity at the European Union’s energy exchanges.
Nowadays, the merits of “dry” cooling towers have been sufficiently appraised, at which industrial water is air-cooled by means of natural draft (the first “dry” cooling towers were installed in 1970 at the Razdan hyrdropower station in Armenia). Equally well known are ventilating “dry” cooling towers, in which the air used for cooling water in water radiators (delta) is forcibly pumped by ventilators (such units were installed in 1973-1976 at the Bilibino nuclear thermal power plant in Chukotka). The start for using “dry” cooling towers in modern Russia is linked with a combined steam-gas thermal heating plant in Sochi and a similar one in Moscow built to supply power to the business center - Moscow-City.
As indicated earlier, the primary consumers of cooled industrial water at thermal and nuclear power plants are steam turbine condensers. At “dry” cooling towers, the accumulation of spent steam in condensers can be ensured both on tubular surfaces without contact with industrial water, cooled by the “dry” tower, and through mixing with chemical salt-free water, circulating through water radiators in the perforated water spray condenser of the “dry” tower.
At complete (100%) condensate cleansing (large delta surfaces enhance proliferation of corrosion products in condensates), the scheme of intermixing condensers is more effective, as in direct contact with cooled water, the condenser’s temperature buildup does not exceed 1 degree Centigrade, while in spent steam condensation on the water radiator surfaces, a temperature buildup of 3-5 degrees Centigrade is required, which predetermines worsening of pressurization and lowering of NPP (nuclear power plant) steam turbine’s capacity. However, even in the intermixing condensation systems, the condensers have 2-3 % lower pressurization than in cooling industrial water in evaporation cooling towers. The use of spent steam at surface condensers, such as at the power block NPP-2006, could lead to an average annual drop in electrical power capacity by 25-30 MW.
Compensation Problems
Compensation for specific expenditure growth concerning a diminishing turbine capacity (e.g. LMZ turbine of 1,000 MW and 3,000 r/min.) may be found in:
- Simplification in the choice of location and cost reduction at NPP construction due to lack of linkage to a cooling water supply and exclusion of expenditures incurred by the construction of water intake installations and water ducts, including the cost of expropriated land tracts;
- Exclusion of any problems involved in the treatment of scavenging (chaser) water from a reservoir at an evaporation cooling tower and soil salinization (mineralization);
- Improvement in the intake chemical regimen in the closed cooler-condenser circuit (loop) and exclusion of condenser tube waste clogging;
- Exclusion of additional needs in makeup water supply with its volume for NPP-2006 amounting to at least 1.2-1.5 cubic meters per second or 30-38 million cubic meters per year;
- Reduction in capital expenditures on turbine installation: at “dry” cooling towers a single turbine requires three low-pressure cylinders instead of four as at evaporation cooling towers;
- Turbine shortening will ensure an abridgement of machine-housing premises by one flight (12 meters);
- An intermixing condenser comes out much cheaper than a condenser based on stainless tubing currently in use;
Technical maintenance of shortened turbines (ZVD+3ZND) is simpler than that of full-sized turbines (ZVD+4ZND – Russian initials for high-pressure cylinder and low-pressure cylinder).
The use of “dry” cooling towers at the NPP-2006 with intermixing condensers will lead to a specific cost rise of the circulating water cooling system by two-fold (approximately 1.5 billion rubles), accompanied by the reduction of capital expenditures on machine-housing premises by 0.9-1.0 billion rubles, i.e. the net increase of capital expenditures on the whole power block will amount to 0.5 billion rubles. The use of “dry” cooling towers, however, lifts all pretences about an NPP impact on the environment, as an air-cooling system for circulatory water is the most compatible one with the environment.
The manufacture of separate elements for “dry” cooling towers, such as deltas, which present heat radiators made of stainless steel tubes, encased in corrugated sheet aluminum or in sheet zinc-plated steel, may be ordered at power machine-building factories such as ZiO, Atommash and others or purchased abroad.
The introduction of “dry” cooling towers at NPPs will necessarily draw the attention of project designers of hydropower stations and combined thermal and power facilities, where ecological problems, as indicated above, are far more acute at the present time.
In view of unavoidable and considerable hikes in payment for irretrievable utilization of natural water in evaporation cooling systems in industry, a joint venture is likely to have a high work load on the manufacture of separate elements of “dry” cooling.
Moreover, the long service life at NPPs and exacerbation of ecological problems in short-term perspective, will necessitate drawing down on the use of industrial water evaporation cooling systems at NPPs, just as they once halted the use of cooling water flowing in straight from nearby rivers and lakes to cool condensers. To switch over to “dry” cooling of industrial water, a relevant power-industry program concerning NPPs should be worked out based on the following measures that include:
- Structural elaboration of thermal scheme and turbine unit design in various conditions utilizing air-cooled industrial water;
- Creation within Rosatom of a joint venture with GEA-EGI company, analogous to a similar venture with ALSTOM company on the manufacture of low-speed turbines;
- Installation of an experimental demonstrative “dry” cooling tower, e.g. at the functioning power block equipped with VVER-440 NVAES (Russian initials for Vodo-Vodyanoi Energetichesky Reactor, Novo–Voronezhsky Atomny Elektrostantzi – water-cooled, water-moderated energy reactor at the Novo-Voronezh Nuclear Power Plant), which operates with evaporation cooling towers;
- Elaboration of design and project documentation on the utilization of “dry” cooling towers at LAES-2 (Leningrad Nuclear Power Plant-2);
Installation of the primary “dry” cooling tower for one of the energy blocks at LAES-2.
The implementation of this industry program should ensure by 2020 the transfer to air cooling at all nuclear power plants under construction. Air cooling of industrial water should be considered at the construction of nuclear-powered heating units which are always to be located near industrial and residential agglomerates.
Moreover, “dry” condensers which utilize spent turbine steam condensing on aerial heat exchangers without the use of an intermediate heat carrier, may be installed at the construction of low-capacity nuclear-powered heating units (6,12, 30 MW). Presently, such layouts have been carried out by Kaluzhski Turbiny Zavod JSC (Turbine Factory in Kaluga) for turbines to be manufactured for small water heating plants running on organic fuel.
The aggregate emission input of water vapor and carbon dioxide into the “greenhouse effect” for different power plants
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Designed for coal-based combined heating-electricity plant (CHEP); fuel consumption at |
Designed for gas-based CHEP at |
Designed for NPP: | |
| Atmospheric oxygen expenditure (gram per kW-hour) | 1,117 | 733 | 0 |
| CO2 discharge (gram per kW-hour) | 1,340 | 505 | 0 |
| H2O discharge (gram per kW-hour) | 0 (conventional) | 413 | 0 |
| H2O evaporation in cooling tower (gram per kW-hour) |
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3,612 |
| Aggregate “greenhouse effect” in CO2- equivalent (gram per kW-hour) |
1,340 (52.4%) +1,217 (47.6%)=2,557 (100%) |
505 (38.07%)+146.5 |
1,281 (100%)= |