Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRICITY GENERATION SYSTEM BASED ON NITROGEN
FIELD OF THE INVENTION
The innovation herein proposed describes an electricity generation system
based on
nitrogen and its use.
PREVIOUS TECHNIQUES
The increasing concern about environmental issues, especially relative CO2
emission reduction associated to the expansion of the Brazilian electricity
sector starts to
stimulate the development and the use of alternative forms of electric energy
generation in
Brazil.
In particular the clean and renewable generation systems are being seen as
priority,
nowadays. The market of wind sources, solar energy and small hydro-electric
power
plants is increasing fastly.
Therefore, in this context, new clean and reneweable technologies for energy
generation started to be investigated in order to substitute the traditional
sources.
The electrical energy generation from hydrogen is one of the alternatives that
is
under research.
Another important trend that is gaining strong support in the current scenario
is the
distributed generation, that is the power generation from small units (small
scale
generation) close to the consumer.
The distributed energy becomes even more important due to the following
factors:
= The necessity to supply consumers isolated from the electrical system. In
rural
areas, the development of local independent systems can eliminate the need for
increasing the distribution grid;
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= The occurrence of several black-outs of great extension that has been
verified in
many countries, causing great damages and inconveniences to the consumers. The
generated energy locally demands less of the transmission electrical systems,
and
provides high reliability and low vulnerability for the centered electrical
systems
that occur, for example, due to serious climatic conditions;
= The increasing demand for 'green energy'. The related commitments to the
climatic
changes and efforts by environment conservation;
= Other factors - Reduced dependence in oil importation, lower atmospheric
pollution, risks reduction of nuclear security, difficulties of localization
of new
power plants and the transmission and distribution capacity, technological
advances, new exportation markets.
The development of new technologies that can guarantee this increasing market
of
distributed energy is more relevant and with priority.
In a limited case, the ideal would be that each residence could have its local
(private) generation, that is, small generators of electric energy.
These small domestic generators can best represent a change in the philosophy
of
the 'the bigger, the better' of the electricity generation that has prevailed
in the energy
sector - with the construction of huge hydro electrical plants, the coal and
nuclear that,
nowadays, supply great parts of the world-wide electricity.
In summary, several technological, environmental and political forces
stimulate the
use of the decentralized energy concept, in small scale, clean and renewable.
This invention presents an alternative form of clean, renewable and
distributed
electric energy generation, based on nitrogen.
The nitrogen is the main element in air (about 78%), therefore a renewable
source
of electric energy generation. Moreover, the equipment herein described
represents a
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clean and distributed form of electricity generation.
The nitrogen can be stored in liquid form facilitating the transport and
positioning,
where the energy is necessary and, therefore its use as fuel for distributed,
clean and
renewable generation of electric energy.
Brazil Patent P1 0202191-9 (03/06/2002) describes a generator using the
nitrogen
where the potential difference is generated from the super conduction of the
magnetic
forces generated by a big magnet.
U.S. Patent 2964917 (20/12/1960) discloses a regasification process for a
liquified
gas such as methane, oxygen or nitrogen, to obtain the gas at a specific
pressure for
generation of mechanical energy, and during which electrical energy can be
obtained as a
side effect."
There are other patents using nitrogen to supply mainly mechanical loads and
electrical energy could also be obtained by side effect. However those
configurations
cannot supply electricity consumers because they do not respond electrical
loads change in
real time.
The present invention is an electricity generation system based on nitrogen
that is
arranged in such a way as to meet electrical load requirements of electricity
consumers.
SUMMARY OF THE INVENTION
The considered system is an electricity generator that uses the ambient
temperature
to heat up and vaporize liquid nitrogen, which is stored at low temperature,
and is pumped
at high pressure through a heat exchanger. The high pressure vaporized
nitrogen gas is
expanded in an expander, which generates mechanical power that drives an
electricity
generator. A controller is arranged between the heat exchanger and expander in
order to
supply nitrogen gas to the expander according to actual electrical load
requirements.
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In its broad embodiment, the electricity generation system of the invention,
based
on liquefied nitrogen, comprises a storage vessel of liquefied nitrogen, a
pump , a heat
exchanger, an expander and an electric energy converter, char a c t er i zedby
arranging a control device between said heat exchanger, and said expander to
control the
inlet of nitrogen to said expander, providing an off-grid electricity
generation system.
In another embodiment, the electricity generation system of the invention
comprises a storage vessel for containing liquified nitrogen, a heat
exchanger, a pump for
transferring liquified nitrogen to the heat exchanger in which the liquified
nitrogen is
heated, an expander for generating mechanical power, a controller interposed
between the
heat exchanger and the expander for controlling flow of nitrogen to the
expander according
to load requirements, and an electricity generator such as an expansion
turbine operatively
connected to the expander for generating electricity. A plurality of storage
vessels for
containing liquified nitrogen, a heat exchanger connected in series with each
storage vessel
and a pump for transferring liquified nitrogen to each heat exchanger can be
arranged in
parallel for supplying heated nitrogen to the expander.
The system can additionally comprise a flow line connecting the expander to
the
heat exchanger for recycling exhaust nitrogen for preheating the liquid
nitrogen.
In its broad embodiment, the method of generating electricity of the invention
comprises pumping liquified nitrogen under pressure from a storage vessel
containing
liquified nitrogen to a heat exchanger, heating and vaporizing the liquified
nitrogen in the
heat exchanger, and controlling flow of vaporized nitrogen gas by a flow
controller to an
expander for generating mechanical power for driving a generator operatively
connected to
the expander for generating electricity.
The method can additionally comprise arranging a plurality of storage tanks
for
containing liquified nitrogen, each in series with a heat exchanger and a pump
for
transferring liquified nitrogen to each heat exchanger, in parallel for
supplying nitrogen to
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the expander, and adding a flow line connecting the expander to the heat
exchanger for
recycling exhaust nitrogen for preheating the liquid nitrogen.
The present invention will be described with reference to the accompanying
drawings, in which:
5 Figure 1 is a
schematic view of the electricity generation system of the
invention; and
Figure 2
is a schematic view of a modular embodiment of the invention in
which a plurality of storage vessels and/or heat exchangers are
arranged to provide a variable electric energy generation capacity
according to load requirements.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is comprised of an electric energy generation system, as
shown in Figure 1, using liquid nitrogen, wherein V represents a storage
vessel of liquid
nitrogen, B is a pump, TC is a heat exchanger, D a control device, EXP an
expander and
CEE an electric energy converter. There is, also, a set of valves that
controls the nitrogen
flow in the system. The valves are also used for the protection and the re-
start of the
system.
The diagram from Figure 1 illustrates the basic principle of operation.
The liquid nitrogen, initially stored in a pressure vessel V, is pumped to the
operating pressure of the system by pump B into the heat exchanger TC. The
heat
exchanger works in a similar form to a car radiator, however, instead of using
air to cool,
it uses the flow of air AR passing through the heat exchanger TC to heat the
nitrogen.
The liquid nitrogen passes through pipes that comprise the heat exchanger,
wherein
it is heated and vaporized by a stream of the air AR at ambient temperature.
After heating
the nitrogen, it is expanded in the expander EXP such as an expansion turbine
for rotation
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depicted by the rotational arrow R, generating mechanical power, which is
converted into
electricity by an electrical generator (CEE). The controller device D is
arranged between
the heat exchanger and expander in order to control nitrogen gas flow to the
expander
according to actual electrical load needs. The exhaust nitrogen can be set
free to the
atmosphere.
With reference to Figure 2, a modular embodiment of the invention is shown in
which several heat exchangers TC are arranged in parallel to increase the
capacity of
electric energy generation (power and energy), through the combination of
nitrogen
storage vessels V1 ¨ V4 in parallel to the respective heat exchanger TC1 ¨ TC4
and then to
the expander EXP.
It is possible to add other components into the system in order to increase
its
efficiency. For example:
= The adoption of fans to blow the air with higher efficiency, i.e., the
surrounding heat at the heat exchanger.
a The physical and geometric constitution of the heat exchanger could be
enhanced aiming a better efficiency. It can be optimized using other pipe
configurations by better exposition of the heat exchanger surface to the
surrounding air and light, aiming at improving the surrounding heat
transference to the liquid nitrogen.
= The exhaust nitrogen gas at the exit of the expander can be re-used for
pre-
heating of the liquid nitrogen in the heat exchanger, as depicted by flow line
FL in Figure 1.
a The nitrogen gas from the expander can still be used as
working fluid in a
second stage of heat transfer and expander, generating more mechanical
work. The number of stages used depend on the desired efficiency and
required power by the system.
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The system has a low cost to generate a clean, renewable and distributed
energy:
= For supplying consumers located in isolated regions of the electrical
system
(off grid consumers).
= For supplying a consumer or group of consumers located in regions of high
commercial losses and high insolvency.
= That allows the selling of energy, before its use, implementing the
concept
of pre paid energy in a consumer or a group of consumers located in high
commercial losses regions and high insolvency.
s To use in residences, in specific applications such as
efficient illumination
and water cooling, amongst others.
= To replace local diesel generators reducing their emissions.
