The present invention concerns a method for controlling the amount of ionised gases and/or particles suspended in the air above roads, streets, open spaces or the like.
The term surface refers to surfaces used for roads, streets, open spaces, including airports, as well as surfaces in the vicinity of roads, streets, open spaces and marking on roads, streets and open spaces. Surfaces of roads, streets and open spaces usually consist of a binding agent mixed with an additive material such as sand, gravel and stones with a certain grain size. The binding agent usually completely surrounds the additive material. The binding material is usually bitumen, which may also be mixed with asphalt, gas tar, bituminous polymers and plastic materials. In the present description the word bitumen is employed, even though the bitumen may be mixed with one or more of the above-mentioned materials. Surfaces in the vicinity of roads, streets and open spaces together with marking on roads, streets and open spaces consist of known per se commercial products.
Bitumen is a very good electrical insulator and is used among other things for encapsulating electrical components. A road surface with a binding agent of bitumen will be an electrical insulator and thus it will not conduct electrical current. It is known that insulating materials such as ebonite, glass and the like can be electrically charged, for example by rubbing against other materials. In the same way the insulating surface on roads, streets and open spaces will be electrically charged by friction due to moving traffic, it will be charged by solar radiation and heating of air molecules which are ionised and which will flow from the surface, and it will be charged by thermal expansion and contraction of the surface. The binding agent in the surface will lose electrons, thus giving the surface a positive charge. In consequence the surface will receive a positive charge relative to the ground which is negatively charged.
It is previously known, e.g. from U.S. Pat. No. 5,707,171 to make a road surface electrically conductive. This, however, has previously only been employed for heating the road surface by passing electric current through it in order to prevent ice formation.
Exhaust gas flows from an internal combustion engine and the gas is normally ionised and has a positive charge. Particles in exhaust gas are similarly positively charged. Dust particles in the air above a roadway are also normally positively charged. The dust particles may come from, amongst other things, the top layer of the roadway, industrial and/or private emission.
An electrically charged surface will act as a pole in an electrostatic system. The surface charge in a road surface which is positive will have the same polarity as the charge of gas ions and/or particles in exhaust gas above roads, streets, open spaces, etc. The surface will therefore repel the said gases and/or particles. The result is that the ionised gases and/or particles above the surface will remain in suspension over roads, streets and open spaces. An electrical Coloumb force has been created which acts on the ionised gases and/or particles. The direction of the force is away from the top layer, thus counteracting gravity. An electrical suspension force has been created.
Ionised gases and/or particles above roads, streets and open spaces, etc. have been shown to represent an ever-increasing health risk. The object of the invention is to control the ionised gases and/or particles. This is achieved by means of an electrical field which is established between the surface as mentioned above and the ionised gases and/or particles which are to be controlled, as indicated in claim 1. The other claims indicate further advantageous features and embodiments of the invention.
According to the invention at least the top layer of the surface and the ionised gases and/or particles will form two electrodes in a capacitor.
The surprising discovery has been made that by using a surface for roads, streets, open spaces, etc. wherein at least the top layer is electrically charged and in electrical contact with earth or a negative voltage source, positively charged gases and positively charged dust particles will be attracted to the surface. This means that harmful and polluting materials will be bound to the surface. The positively charged gases and/or particles will moreover be neutralised by contact with the electrically charged surface. In addition an earthed surface will not be charged by friction due to moving traffic or by solar radiation and heating and ionising of air molecules flowing from the surface or by expansion and contraction of the surface. In addition reduced electrical friction between a vehicle and the surface will be capable of reducing the vehicle""s fuel consumption and thereby the discharge of exhaust gases.
By means of the invention the result has been achieved that, instead of being suspended above a surface, exhaust gases and particles from internal combustion engines together with dust particles are attracted to the surface with the result that the air over the surface remains clean. This is of great importance for the task of reducing pollution which is due among other things to exhaust gases from internal combustion engines and the invention therefore is of vital importance for the environment. Large areas of the earth""s surface are at present covered by an insulating surface such as bitumen. The extent of this surface is so great that in addition to being important for the environment it may be of importance for the climate and life on earth.
Due to combustion in industry and private households and car traffic, large amounts of ionised gases and/or particles will be formed over roads, streets, open spaces, etc. In such places an electrically charged surface will establish an electrical field, thereby controlling the amount of noxious ionised gases and/or particles. The surface is charged by adding to the currently used binding agent, at least in a top layer of the surface, a conductive material such as, e.g. carbon powder. The surface is then placed in contact with earth or a negative voltage source. This makes the surface a cathode in a capacitor where the positively charged ionised gases and/or particles represent the anode. The electrical field which is created between the anode and the cathode will draw the ionised gases and/or particles towards the top layer, thereby ionising them as well as preventing them from being suspended.
In order to make the surface electrically charged, a network of conductive metal or a piezoelectric material may also be employed under the top layer which is placed in contact with earth or a negative voltage source. The electrically charged top layer may also be composed or a coating which is laid on top of the entire or parts of the surface, for example in the form of road marking or the like.
An electrically charged surface which is in electrical contact with earth will be electrically neutral. It will be capable of emitting or absorbing electrons and by means of friction caused by car wheels a vehicle will remain electrically neutral. The result of this is that neither the vehicle nor the people in the vehicle will be charged, and obtain an electrical voltage relative to the environment. This will prevent unpleasant electric shocks when entering and leaving a vehicle due to potential differences which are common when a vehicle travels on standard insulating surfaces. In the same way an electrically conductive surface will reduce the risk of sparking due to potential differences between a vehicle and the surface. Accidents which can occur due to ignition of inflammable and explosive chemicals and gases which are transported on roads with an electrically conductive surface will thereby be reduced.
Research has shown that car sickness and a feeling of tiredness while driving are due to the build-up of static electrical fields in the vehicle. This will be reduced by the use of an electrically charged surface which is in electrical contact with earth and is thereby electrically neutral. The invention will therefore also be important for traffic safety.