Introduction
The beginning of the XX century as brought about fast developments of technics
and industry. Decades ago, no one knew the results it would bring. Paradoxically,
devices that should have provided a better quality of life became at the same
time the sources of the world’s biggest problem, which is the pollution of the
atmosphere, ground and water. These pollutions are the proximate cause of ill
people and animals, lowering crops, necrosis forests, growing barren ground,
and also the growing warm climate. Because of the different kinds of
pollutions, in some countries it is the deficit of water.
The development
of industry has caused an increase for mineral fuels - pit
and brown coal, petroleum and earth gas, which supplies have slowly worn out. The intensive exploitation of these fuels, as well as pollution, have utilized a new wider range of sources of energy, such as:
• sun radiation (solar energy),
• energy of splitting the radioactive
elements,
• energy of wind,
• energy of fall of waters (the water
energy),
• biomass (the energy of burning the
plants),
• geothermal energy (energy of highly
active depth waters),
• energy of waters and oceans.
These
sources are characterized by the lack of releasing greenhouse gases and dirt to
the natural environment. Special attention needs to be given to the utilization
of geothermal sources for heat engineering and the production of electric
energy [12].
Utilization
of geothermal energy in the world
Taking into consideration the current technical possibilities and
economic conditioning, over 70 countries
possess the resources of geothermal water and steam, which are useful for
practical utilization [3]. In 2000, geothermal energy for the production of
electric energy was used in 23 countries. Installed
power in geothermal power stations carried out about 8000 MW, where the
year-old consumption of energy carried out about 50 000 GWh. The most spectacular example of the utilization of geothermal sources
is in Iceland, where geothermal energy satisfies 86% of the country’s needs in
the range of heat engineering. In developed countries, where a large amount of electric energy is
used, power produced from
geothermal power stations is marginal by comparison.
Geothermal
power stations only fulfill part of the local supplementary sources. Different situations are occurring in
developing countries in South and Central America, Asia and Africa, where 70% of the world’s population lives, and where only 25% of
electric energy is produced in the world, in this on communal existence 14%,
although only a majority of
these countries have the
resources of high-temperature water and geothermal steams which would enable
the obtainment of inexpensive energy. In some of these countries, geothermal
energy is already a very important factor in the balance of the prime carrier
of energy, and the part of the electric energy obtained from geothermal energy
has a strong position.
Direct
utilization energy from geothermal water, where the temperature is low with averages from 20 to over 1000C,
encloses a very wide range of practical application. The principal influence
on the possibility of the utilization of energy from geothermal water is the
temperature and stage of their mineralisation. Geothermal waters contain
dissolved mineral substances, which quantitative type - matter depends on the
depth of the covering, temperature, as
well as the geological conditions of the geothermal reservoir [10]. The quantity of the produced electric energy and the direct uses of
geothermal energy in the world is introduced in table 1. A growing interest has wakened regarding the generation
of electricity in binary systems,
which has already been introduced and practiced
in Iceland and Austria.
Direct uses of geothermal energy is well-known in over
60 countries, such as China, Japan, USA, Iceland, Turkey, New Zealand, Georgia,
Russia, France and Hungary.
Table
1. Production of electric energy and the direct uses of geothermal energy
according to [3]
|
Continent |
Production of electric
energy |
Direct uses |
||||
|
Installed power |
Total production |
Installed power |
Total production |
|||
|
MW |
GWh/year |
% |
MW |
GWh/year |
% |
|
|
Afryka |
54 |
397 |
1 |
121 |
492 |
1 |
|
Ameryka |
3 390 |
23 342 |
47 |
5 954 |
7 266 |
14 |
|
Azja |
3 095 |
17 509 |
35 |
5 151 |
22 532 |
44 |
|
Europa |
998 |
5 745 |
12 |
5 630 |
19 090 |
37 |
|
Oceania |
437 |
2 269 |
5 |
318 |
2 049 |
4 |
|
Razem |
7 974 |
49 262 |
100 |
14 174 |
51 429 |
100 |
Large quantities of heat are also
stored in rocks which do not contain waters or steams, and, they possess high
temperatures; they are so called Hot Dry Rock. In several
countries, such as France, Germany, Switzerland and Japan, research has been
conducted over the ways of regaining the rocks’ warmth. It is also allowed to
regain the warmth from the rocks and ground near the surface, from land water and
even from river waters, ponds and lakes. However, they posses comparatively low temperatures from several to a
dozen or so Celsius stages, and contain warmth that is suitable for utilization with help of pumps of warmth.
In Poland, as well as other countries,
there is a growing interest in these devices for the heating of houses,
glasshouses, pools, and water for home use. In Switzerland, for instance, there
are already tens of thousands of such installations that deliver warmth to
central heating and for the preparation of warm usable water in habitable
buildings, and hotels and office buildings.
The
opinion of geothermal potential in the world shows that the accessible datum
features of useful supplies for the production of electric energy carry out about
12000 TWh/year [1]. Presently, a small
percent of this potential is used, though
there is a real chance for the enlargement of the production and consumption of
electric energy obtained from geothermal steam. Another larger is range of direct utilization of geothermal
energy. The available base of useful
resources is estimated for 600 thousand EJ. According to prognoses, by
the present level of utilization, these resources will be suffice for about 5
million years.
By existing resources and advanced technology, the further development
of the utilization of geothermal energy
in individual countries depends on the analyses of profitability and the
competitiveness of the market in comparison from different carriers of energy
[3]. Electric energy
from geothermal steam is produced in 21 countries. Among the countries which
produce 10 - 20% of the electric energy from geothermal steams are USA,
Philippines, Costa Rica, Salvador and Iceland. Between 1995 and 2000, the growth of the installed electric power from
geothermal sources was carried out by 43%. The cost of the production of
electric energy is diverse and is most often carried out at 4 cents USD/1 kWh
[3].
Table 2. Direct utilization of geothermal energy in the world according
to [5]
|
Use |
Installed power MWt |
% |
Heat production TJ/rok |
% |
|
Heat pump |
6 849 |
42,25 |
23 214 |
14,33 |
|
Heating |
4 954 |
30,56 |
59 696 |
36,85 |
|
Glasshouses |
1 371 |
8,46 |
19 035 |
11,75 |
|
Fish farming |
525 |
3,24 |
10 757 |
6,64 |
|
Dryling agricultural product |
69 |
0,43 |
954 |
0,59 |
|
Industrial use |
494 |
3,05 |
10 536 |
6,50 |
|
Recreation and hot water therapy |
1 796 |
11,08 |
35 892 |
22,15 |
|
Air-conditioning and melting snow |
108 |
0,67 |
968 |
0,60 |
|
Different |
43 |
0,27 |
957 |
0,59 |
|
TOGETHER |
16 209 |
100 |
162 009 |
100 |
The range of direct uses of
geothermal energy is very wide and contains the heating/cooling,
air-conditioning, industry, greenhouse gardening, fish farming, and health
resorts (table 2). This kind of logging of energy is characterized with a great
reliability and has the important advantages of the technological, economical and
ecological. Among the ranges of utilization, heat engineering (37%)
predominates; also popular are balneology
and recreation (22%), heat pumps (14%), glasshouses (12%), fish farming
(7%) and industry (7%). The directions of farm implements geothermal
energy are far-reaching and fully possible in realization, including In
Poland.
The
growth of the installed geothermal power in the field of direct utilization in
between1995 - 2000 carried out 44%. Recently geothermal energy was the object
of interest only when the supplies of
waters or steams achieved high temperatures, which was related with the deep
covering of these supplies (3 - 4 km). In the last period, interest in geothermal sources underwent change with
the development of applying heat pumps – devices which using ground as bottom
source of warmth or place where can accompany excess of warmth in cooling
process ( according to time of the year). Heat pumps can be used fundamentally
in every country. For instance, in the USA, 400 thousand heat pumps, giving
about 4800 MW of thermal energy, a production of energy of 3300 GWh/yahr. The year - old growth of warmth production using heat pumps carries
out 10%. Leaders in this trade are Switzerland, Sweden, Germany, Austria and
Canada [4]. Geothermal energy, by different renewable sources of energy, such
as: the energy of waterfalls, wind and biomass, is competitive in comparison
from traditional fuels.
Geothermal energy in Poland
Poland belongs to the countries possessing large supplies of geothermal
energy which in the majority has ow
enthalpy . In the opinion of experts, geothermal energy should be treated as
one of main renewable sources of energy in Poland. Presently, the waters in
deposits have temperatures at about 20 to 130 °C, stepping out at depths of 3 -
4 km, and can be used for practical waste management. We can distinguish three geothermal
provinces:
• Province Depression Polish,
• Province Przedkarpcia,
• Carpathian Province;
All
of which have extensive geological pools, including numerous reservoirs of
geothermal waters geotermalnych (picture 1), with a total surface of about 250
tys. km2 (about 80% of the country’s surface) [6].
Picture
1. Heat engineering geothermal institutions - functioning (1), constructed (2),
as well as health resorts applying geothermal waters (3) [6].
Interesting conditions also possess
waters from Sudety Mountains which are laid in crystalline parties of rocks and
in paleozoic [2]. From documentary evidence, supplies of geothermal waters from
bore-holes carry out about 50-550 m3/h.
Taking under consideration the current prices of traditional carriers of
energy, remunerative under the economic point of view is building of geothermal
plants and installations for 40% of the surface of the country [7].
Geothermal water was already used in medical care in the XIII and XIV
century in Ladek Zdrój and Cieplice. Warm underground waters for
treatment and healing cuts were used in Dusznik Zdroj, Ciechocinek, Konstancin, Ustroń, Iwonicz Zdrój and
Zakopanem where there is a large geothermal recreational centre.
In Poland, geothermal energy possesses a large chance of development in
the heat engineering and recreation - healing sectors. Particularly important
is heat engineering: the central heating, preparation of warm water for home
use, as well as agriculture: glasshouses, tunnels, fish farming, drying room,
and also – recreation and healing: pools, water parks, rest centres and healing
applying geothermal waters. It will
permit considerable limitation of the quantity of burnt carbon, coke, petroleum
and gas, as well as connected with the decrease of the dirt of the natural
environment.
The
wider interest of researching and practical utilization of geothermal energy to
heat engineering started in the 1980s. The First Experimental Geothermal
Institution Polish Academy of Science started in 1992 on Podhale [9], which
opened the way for further work. In 1996, s work started on the second heating
geothermal plant in Pyrzyce; , a heating
plant in Mszczonów in 1999, in Uniejów in 2001, and in Słomniki in 2002. In Podhale, from
few years lasting building of the biggest in Poland and one of the largest In
Europe, a heat engineering net which provides for Zakopane. On track for
realization is the heat engineering institution in Stargard Szczeciński,
also lasting studies of profitability and projects of utilization of geothermal
energy. The prognosis and strategies found the local part of geothermal energy
in the energetistic market in Poland. Far-reaching field for applying
geothermal energy inthe heat engineering, which will contribute to a
significant reduction of the quantity of burnt traditional fuels and the
release of dirts. In many regions of the country, the geotermice has a real
chance for being an essential part in the local heat engineering market. The
main advantages resulting from applying the geotermice will be connected with
the protection of the natural environment, because it will have a limited
quantity of dirt produced by traditional heat engineering systems based on
carbon.
Geotermal energy should be promoted in Poland because of the requirements placed on the European
Union, related to the production of electric energy from renewable sources
(until 2010, 7,5% of the
renewable energy in the energetic balance of the country).
The basic arrangements of geothermal
systems in heat engineering
The systems of geothermal installation, which are applied in municipal
heat engineering, depend on the parameters of the used geothermal water, as
well as the demand for warmth by the recipient. The parameters of geothermal
waters on certain areas can be accepted as steady, but the demand of the
recipients for warmth is variable and depends on external temperature.
Organized graphs of demand for warmth are the basis to projecting geothermal arrangements. They are helpful for closely
establishing the conception and especially near choice of projecting the
sources of warmth, especially of the
aggregate of devices to receive the energy from geothermal waters. In dependence from part of geothermal
energy in satisfying the heating the recipient's needs, we can distinguish
three the basic arrangements of geothermal systems:
Monowalent arrangement –
recipient's heating needs are
fully satisfied through the geothermal heating plant (picture 2), and the power
installed in the source is adapted to the maximum demand on the thermal power
defined for the computational external temperature.
Picture 2. The block pattern and the well
ordered graph of the monowalental
arrangement , Q - the demand for warmth, the Qmax - the maximum demand for
warmth, the Qgeo - quantity of warmth from geothermics , N - the length of the
heat season (days).
This arrangement possesses essential defects connected with the low
utilization of the flexible power of the geothermal source, which leads to the
rise of the costs of warmth. The advisability of applying such arrangement
is recommended in the case of high temperatures of water (about 100°C) or
cascade utilization of the store of warmth to different technological processes.
Biwalent arrangement – geothermal
heating plant fulfills the function of the basic source, which works together
with the peak boiler; for instance, gas
boiler or oil boiler, when there is a large demand for heat. This arrangement
makes for the better utilization of flexible power of the geothermal source for
the entire heating period possible.
Picture 3. The block pattern and the well
ordered graph of the biwalent
arrangement , Q - the demand for warmth, the Qmax - the maximum demand for warmth,
the Qgeo - quantity of warmth from geothermics , N - the length of the heat
season (days)
For
most part of the year, the thermal needs for heat satisfies geothermal plant and in the peak of
the demand for heating starts to work in arrangement with the peak boiler; most
often it is an old boiler room (rys. 3).Biwalentny arrangement is, however more
expensive.
Picture 4. The block pattern and the well
ordered graph of the complex arrangement GO – recipients group, Q –the demand
for warmth, Qmax – the maximum demand for warmth, Qgeo –
quantity of warmth from geothermics, N – the length of the heat season (days)
Complex
arrangement – part of the recipients is
reinforced through heating plants (low temperature heating) and remaining from
conventional boiler rooms (traditional heating). The connection of both systems
is made possible at a considerably larger stage of the utilization of the power
of the geothermal source and decreasing the cost of warmth production (picture
4). The work of both systems steps out only in colder periods of the heat
season, apart from this period, the conventional boilers become extinguished
and the geothermal heating plant takes over the production of warmth to heating
and the preparation of warm usable water.
The choice of one of the introduced
solutions of the heating plant is made in regards to the techno-economic
aspects and the local geothermal conditions, and also the possibility of
rational farm implements of geothermal warmth, especially apart from the heat
season [8].
Summary
The chance for the development of
renewable sources of energy: wind, solar radiation, energy of ocean and
geothermics, is in the integration of local sources of energy with regional energetistic structures.
Followers of renewable sources of energy should actively co-operate with the
very conservative world market of energy. According to investigations over the
supplies of energy published by the World
Energy Council, geothermal energy plays
a key part (52% of installed power and 80% of electric energy produced from all
four renewable sources of energy). Comparatively, a large part of the
production of electric energy testifies
for the reliability of a power station, for which the coefficient of the duty
and accessibility is between 80 to 90% .
From an energetistic safety point of view, it is the geothermal energy.
In contrast to the sun’s energy, wind and water is independent from weather and
external conditions. It possesses its own possibilities of supplies and it can
be used in power stations working on covering basic and peak demand heating.
Geothermal energy is:
- ecological - the application of
which does not cause the release of harmful substances (dusts and gasses) to
the surroundings,
-
abundant - warmth of the ground
accumulated in the deposits of geothermal waters tops many times the
quantity of warmth possible from obtainment from mineral fuels and even from
different renewable sources of energy,
-
renewable - the supplies of ground warmth are so large, that
using it at a considerably larger scale than the
present will not cause exhaustion,
-
local – it is used in the vicinity of place occurrence,
because the highly active waters and steams are not suitable for long
transportation for help of pipelines, its deliveries are not dependent on the
international political situation which can influence the price of energetistic
materials,
- cheaper - in comparison
with costs and the prices of electric energy or warmth from traditional mineral
fuels, and even from some different renewable sources,
-
unfailing - the geothermal energy from the underground deposit of
water and steam can be used all year in necessary quantities [11].
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[10] http://kmiue.imir.agh.edu.pl/oze/geo/dgeo2.htm
[11] www.pga.org.pl/ENERGIA_GEOTERMALNA
[12]
www.energia-odnawialna.net/
Authors: mgr inż. Paweł Podolski, dr hab. inż. Bogumiła
Wnukowska, Politechnika Wrocławska, Instytut Energoelektryki, ul.
Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, E-mail: pawel.podolski@pwr.wroc.pl,
bogumila.wnukowska@pwr.wroc.pl