Patent Application
20140147295
The invention relates to a process to compress a gas driven by an external power source in the form of a variable rotation. The invention is also related to a configuration to compress gas and to a heat-pump system comprising the configuration.
Such a process to compress gas is described in WO2010/023142. In this publication a process is described wherein a series of piston compressors is used to compress a refrigerant and wherein the compressors are driven by a wind turbine. At increasing wind speeds more pistons are engaged.
A disadvantage of the process and configuration of WO2010/023142 is that the process of engaging and disengaging the pistons as a function of wind speed is complex. No commercial applications are known to applicant. It is believed that this is because of its complexity and technical challenges still to overcome.
The object of the present invention is to provide a simpler process and configuration. This is achieved by the following configuration and process.
Configuration for compressing a gas comprising
(i) a reciprocating compressor, wherein the compressor comprises a mechanical drive to transfer energy from a variable rotational power source to the compressor and a control valve and an adjustable swash plate, wherein adjusting the control valve results in adjusting the swash plate;
(ii) a speed sensor to measure the rotational speed of the power source;
(iii) a first control means which control means is capable of adjusting the control valve as a function of the rotational speed measured by the speed sensor.
The invention is also directed to a heat-pump system, comprising a refrigerant, an evaporator, a condenser and a configuration for compressing gas according to the invention.
The invention is also directed to a process to compress a gas using a reciprocating compressor provided with an adjustable swash plate and driven by an external power source in the form of a variable rotation and wherein the adjustable swash plate of the compressor is adjusted as a function of the speed of rotation.
Applicants found that by using a reciprocating compressor provided with an adjustable swash plate a much simpler process of compressing and configuration is obtained which can gradually increase the displacement of the compressor. With the present process there is no need to engage and disengage the various pistons of the prior art process and configuration. Thus there is no need for pistons which are sometimes idle, or for complex mechanical solutions to engage and disengage the different pistons of the prior art process. The present process can be used in combination with commercially available wind turbines and does not require the specially adapted wind turbine as shown in WO2010/023142. Other advantages will be described below.
The configuration according to the invention comprises a reciprocating compressor provided with at least a control valve and a swash plate. Preferably the control valve is a mechanically and/or electromagnetic control valve. The swash plate is angle adjustable with respect to a drive shaft of the pistons of the compressor. The angle of the swash plate determines the displacement of the compressor. An increase in the angle results in a larger piston stroke and thus in a larger displacement. The angle is adjustable by adjusting the control valve. The control valve influences the pressure level within the housing of the compressor. The control valve controls the pressure difference between the compressor housing and the discharge pressure of the compressor. When the control valve allows a high pressure difference a relatively low pressure in the housing will result. This in turn will result in a high swash plate angle and thus in a large piston stroke. The large piston stroke will result in turn in a high displacement of the compressor. When the control valve allows a low pressure difference between the discharge pressure and the pressure in the housing a relatively high pressure in the housing results. This in turn will result in a small swash plate angle and thus in a small displacement of the compressor. Thus at low rotational speed the control valve will only allow a high pressure in the compressor housing resulting in a small displacement of the compressor. At increasing rotational speeds the displacement will as a result continuously and infinitely increase. The displacement of the compressor may be varied from 0 to 100% of its capacity and more preferably at a constant discharge pressure of the compressor. The latter is especially advantageous when the discharge pressure should remain constant at the variable rotational speeds of the power source, such as in a heat-pump application as will be discussed below.
This compressor enables to simply vary the displacement of the pistons of the compressor as a function of the rotational speed of the power sources varies. This is achieved by adjusting the control valve as a function of the rotational speed measured by the speed sensor. Preferably the adjustment is non-linear, in that the adjustment increases at lower rotational speeds. The described reciprocating compressors may be commercially obtained. Thus no specially designed compressors are required like in the state of the art processes or designs. Nor is it necessary to combine multiple compressors and pistons to the variable rotational power source as in the prior art wherein part of the pistons are idle at the lower rotational speeds. With the present configuration the capacity and thus the load of the compressor is continuously and infinitely adjustable on the speed of the wind-turbine. This in contrast to the process of the prior art described in WO2010/023142 wherein one or more cylinders are activated one by one, a stepwise load on the wind-turbine. This step-wise process makes the operation of the wind-turbine very difficult and also leads to reduced output of compressed gas which is a disadvantage.
In summary of the above the configuration suitably comprises control means for control continuously and infinitely the load of the reciprocating compressor by a speed sensor and an adjustable swash plate, and
control means for control an adjustment of the pistons setting stroke adjustment by mechanically and/or electromagnetic control valve in the reciprocating compressor to a set-point.
The variable rotational power source is suitably a wind turbine, a water driven turbine or a steam turbine and more preferably a wind turbine. An example of a water-driven turbine is a tidal force driven turbine, wherein the power will vary as a function of the tidal cycle. An example of a steam turbine is suitably a steam turbine powered by concentrated solar power. The steam produced in such a process may vary as a function of solar intensity. The power and torque produced by the wind-turbine may change continuously due to the continuous variable wind-speed and its effects on the wind-turbines rotor.
The mechanical drive is suitably a mechanical drive and gear train. The speed sensor is suitably positioned on the drive train for measuring the rotation speed the power source.
The configuration can be used to compress a gas and store said compressed gas for use at another time. In this manner wind power can be stored at times wherein wind speeds are high and wherein the power is used when the wind power is not sufficient to provide the required power. The required power, for example in the form of electricity, can be directly generated using the compressed gas. This avoids the need of using batteries for storing electricity generated directly from for example wind power.
The invention is also directed to a heat-pump system, comprising a refrigerant, an evaporator, a condenser, an expansion valve and a configuration for compressing gas according to the present invention. Such a heat-pump may be advantageously used for air-conditioning, refrigerating or other cooling applications. Applicants found that such a heat-pump system can easily adapt itself to varying rotational speeds of the power source and to varying starting temperatures of the medium, typically air, to which the heat-pump provides cooling. The varying starting temperature of air may result from climate, day and night cycles and day to day weather changes.
Preferably a primary air fan is present in the heat-pump system to direct air to the evaporator; a secondary air fan is present to direct air to the condenser, a first pressure sensor to measure a first pressure of the refrigerant at the suction side of the compressor or a first temperature sensor to measure a first temperature of the refrigerant at the suction side of the compressor, a control means to control the primary air fan as a function of the first pressure measured by the first pressure sensor or as a function of the first temperature measured by the first temperature sensor. More preferably a second pressure sensor is present to measure a second pressure of the refrigerant at the discharge side of the compressor or a second temperature sensor to measure a second temperature of the refrigerant at the discharge side of the compressor and a control means is present for control the secondary air fan as a function of the second pressure measured by the second pressure sensor or as a function of the second temperature measured by the second temperature sensor. A set-point for suction pressure and discharge pressure or suction temperature and discharge temperature will be chosen. The chosen set-point may for example depend on the desired temperature of the air flows as they have passed either the evaporator and/or the condenser. Combinations of pressure sensor and control and temperature sensor and control are possible. Preferably the heat-pump system uses pressure measurements to control the primary and secondary air fans as described above.
Preferably the air as supplied by the primary air fan and cooled in the evaporator is added to the secondary air to obtain a mixed flow of cooled air flow and secondary air. This mixed flow is suitably directed to the condenser. Thus the heat-pump system preferably has a passage connecting the air outlet of the evaporator with the air inlet of the condenser. This results in a lower condenser pressure and thus a higher compressor efficiency.
The heat-pump system having the above pressure and/or temperature sensors and control is advantageous in that the temperature reduction of the air as it passes the evaporator can be controlled in an optimal manner even when the rotational speed of the external power sources varies. This is especially advantageous when the heat-pump is used to condense water from the air. A certain temperature range of the air as it has passed the evaporator will then be required to achieve the desired condensation of water. With the present heat-pump this can be achieved in a simple manner, wherein the wind-turbine is leading and the heat-pump follows, in a master-slave relation.
Preferably the control means to control the primary and secondary air fans operate independent of the first control means. The control means to control the primary and secondary air fans keep the heat-pump system in balance.
A preferred heat-pump system therefore suitably comprises means to collect condensed water, for example comprising a collecting drip-pan, a water reservoir and an outlet for the collected water.
The refrigerant may be any compound which condenses and evaporates within reasonable pressure conditions. Examples are Ammonia, CO2, hydrofluorocarbon (HFC) and hydrofluoro-olefin (HFO) refrigerant. Typically refrigerants may be used which are also used as automotive air-conditioning refrigerants. An example of a suited hydrofluorocarbon is HFC-134a. Preferably a HFO-type refrigerants is used, and even more preferably CF3CF=CH2 (2,3,3,3-tetrafluoropropene) is used which is commercially available as HFO 1234YF as Opteon™ from DuPont.
The invention is also directed to a device for extracting humid from air, comprising a heat-pump system according to the invention and a wind-turbine as the variable rotational power source. The wind-turbine may be any turbine which can be coupled to the mechanical drive of the compressor, optionally via a appropriate drive train. This is one of the advantages of the present invention, namely that no specially designed or adapted wind-turbines are required.
The invention is also directed to a process to compress a gas using a reciprocating compressor provided with an adjustable swash plate and driven by an external power source in the form of a variable rotation and wherein the adjustable swash plate of the compressor is adjusted as a function of the speed of rotation. Preferably the adjustment is non-linear. The non-linear adjustment results in that the incremental increase of the compression power as a result of an increase in rotation speed is larger at higher rotational speeds. Suitably the variable rotation of the external power source is measured using a speed sensor resulting in a measured speed of rotation. The measured speed of rotation is suitably used as input to adjust the swash plate by mechanically and/or electromagnetic adjustment of a control valve as comprised in the reciprocating compressor. The compressor may be a compressor as described above.
Preferably the gas is a refrigerant for use in a heat pump cycle comprising an evaporator, a condenser, an expansion valve, a flow of gaseous refrigerant and a flow of condensed refrigerant. Such a process may find application in air conditioning, refrigeration and other thermal processes. Preferably the process is used to cool or heat air. More preferably the flow of air comprising humid is suitably cooled by indirect heat exchange against a flow of gaseous refrigerant in the evaporator resulting in a mixture of condensed water and a cooled air flow. The condensed water is suitably separated as a product of the process from the cooled air flow. In this manner a process is obtained wherein the humid from the air is obtained as liquid water by using a variable rotational power source such as wind.
The temperature of the cooled air flow is preferably between 0 and 10° C. and more preferably between 3 and 5° C. The desired temperature of the cooled air is achieved by choosing a corresponding suction and discharge pressure set-point or a temperature set point of the refrigerant. This set-point will be dependent on the evaporation and condensing properties of the refrigerant.
Preferably the flow of air in this process is adjusted as a function of the pressure of the gaseous refrigerant as present between evaporator and compressor in the heat-pump cycle. Or said otherwise at the suction side of the compressor. At a decrease in this pressure the flow of air is increased.
In this process a flow of compressed gaseous refrigerant is condensed in the condenser by indirect heat exchange against mixed flow of secondary air and cooled air flow and wherein the flow of secondary air is adjusted as a function of the pressure of the gaseous refrigerant as present between the compressor and the condenser in the heat-pump cycle. At a decrease in this pressure the flow of air is decreased.
The flow of primary and secondary air are suitably generated by using one or more fans. The fans are suitably electrically driven fans and the required electricity is preferably generated by an alternator which is drive by the same external power source in the form of a variable rotation as described above. Thus preferably the external power source in the form of a variable rotation also drives a generator to generate electricity and more preferably the generated electricity is used to operate the heat-pump cycle, such as these air fans.
The invention is also directed to a device for extracting humid from air, comprising a wind-turbine for energy supply, a mechanical drive and gear train to transfer the energy and increasing the speed to both a generator and at least one heat-pump system comprising a compressor with pistons, characterized by:
The device shown in
The displacement of the reciprocating compressor (8) is a function of the wind-turbine (1) speed and an internal (mechanically or electrically) pressure control device.
The capacity of the primary air fan (10) is a function of the suction pressure measured by the pressure sensor (16). The output of the primary air fan (10) can be adjusted continuously, infinitely, 0% up to 100%, using a control loop.
The capacity of the secondary air fan (11) is a function of the discharge pressure measured by the pressure sensor (17). Also the output of the secondary air fan (11) can be adjusted continuously, infinitely, 0% up to 100%, using a control loop
The variable displacement reciprocating compressor (8) is an axial compressor shown in
The pistons (25) are driven by a swash plate (30). In such a swash plate compressor (8), the plate itself rotates with the driveshaft (26). A bearing (31) in the bottom of each piston (25) “clamps” around the edge and rides on either face of the swash plate (30).
The swash plate (30) is set at a variable angle Φ to the driveshaft (26), so as it rotates, the pistons (25) are forced back and forth in their bores. The angle Φ of the swash plate (30) determines the length of the piston stroke.
When housing pressure is increased, the pressure exerted on the back side of the pistons (25) keeps them “higher” in their bores and closer to the cylinder head (29). This shortens the stroke, reducing displacement. When housing pressure is reduced, a spring (33) pushes the adjusting linkage away from the cylinder head (29), keeps them “lower” in their bores and lengthening the piston stroke to increase displacement.
Housing pressure is adjusted using a control valve (34,35) with ports and passages that connect it to the suction (low-side) (34) and discharge (high-side) (35) chambers of the cylinder head (29) and thus controls the refrigerant mass flow in accordance with the amplitude of wind-turbine power and torque.
In accordance with the invention the adjustable swash plate (30) and the speed sensor (7) are first control means for control continuously and infinitely the load of the reciprocating compressor (8). Preferably the speed sensor (7) of the first control means is a sensor positioned on the drive train (2,3) for measuring the rotation speed of the wind turbine (1) and coupled by electrical wiring to the reciprocating compressor (8).
Second control means are controlling the pistons setting stroke adjustment by mechanically and/or electromagnetic control valves (34, 35) in the compressor to a set-point,
Third control means are controlling the primary air fan (10) by the pressure sensor (16) in the suction line to a set-point obtained by changing continuously and infinitely the airflow over the cooler (14),
Fourth control means are controlling the secondary air fan (11) by the pressure sensor (17) in the discharge line to a set-point obtained by changing continuously and infinitely the airflow over the condenser (9).
In a preferred alternative embodiment the air fans are equipped with integrated electronically commutated technology.
Primarily this allows the device to operate brushless and without any control system. The electronically commutated technology provides the motor its own intelligence.
Speed flexibility is required for control the airflow (10,11) over the condenser (9) and cooler (14). Perfect controllability and wide operation range allows the use of simple sensors/transmitters. Integrated proportional—integral—derivative control makes an external control unit unnecessary. Integrated ‘master slave’ option makes it possible to use just one of the fans when installed in pairs. Starting current is equal or smaller than the rated current, gives the opportunity to minimize the wiring/cable sizes. Integrated security engine protects the device against malfunction and defects. Electronically commutated technology constructed on the engine makes any assembly unnecessary. High efficiency allows the device to use the maximum wind turbine energy for the thermal circuit. Proper sound makes any sound insulation unnecessary. Compact construction makes small devices possible and demands lower requirements for the structural device. Maintenance free and long life allows a minimal maintenance schedule and thus cost-effective operation.
It is noted that the device illustrated in
The invention shall be illustrated by means of the following example based on calculations and models.
The influence of a varying air temperature and relative humidity on the operation of a set-up as in
The influence of fluctuating wind speed at constant air conditions on the operation of a set-up as in
The description of the embodiments is intended to be illustrative and not to limit the scope of the claims. As such, the present teachings can readily applied to other type of devices and many alternatives, modifications and variations will be apparent for those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1038701 | Mar 2011 | NL | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NL2012/050145 | 3/9/2012 | WO | 00 | 2/13/2014 |
