Patent Publication Number: US-2016238263-A1

Title: Low noise micro environmental workspace comfort unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. provisional patent application Ser. No. 62/117,231, LOW NOISE MICRO ENVIRONMENTAL WORKSPACE COMFORT UNIT, filed Feb. 17, 2015, which application is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE APPLICATION 
     The application relates to workstation environmental units and particularly to fan control and air distribution from a workstation environmental unit. 
     BACKGROUND 
     There has been an increasing trend away from personal offices towards workstations in open spaces. With energy conservation and cost concerns, there is less heating or cooling of opens spaces. In some industrial settings, such as on a factory floor, or in a warehouse, it may not be possible to provide a comfortable office like working environment. Workers at desks in such open spaces may be uncomfortable for hours at a time leading to lower morale and lower worker productivity. 
     SUMMARY 
     According to one aspect, a low noise micro environmental workspace comfort unit for a workspace includes a comfort unit enclosure having a mounting flange to mount the comfort unit enclosure to a surface of a workspace. At least one louver is mechanically coupled to the comfort unit enclosure to provide an ambient air flow to a person working at the workspace. A controller accepts a set point from a person working at the workspace, the set point representing a desired rate of ambient air flow. At least one ambient air fan is mounted to a wall of the comfort unit enclosure and electrically coupled to a fan speed control module. The fan speed control module is operatively coupled to the controller. At least one heated air fan is mounted to the wall or another wall of the comfort unit enclosure at a different place than the at least one ambient air fan. The at least one heated air fan includes a heating element which is mechanically coupled to the heated air fan. Operation of the heating element can be controlled by the controller. At least one heated air outlet directs air heated by said heated air fan to a person working at said workspace. A heat reflector having a curved surface is disposed with a center of the curved surface at about a midpoint between the at least one heated air fan and the at least one air outlet such that the heat reflector reflects heat radiation away from a rear portion of the low noise micro environmental workspace comfort unit and directs an air flow from the at least one heated air fan to the at least one air outlet. 
     In one embodiment, the curved surface comprises about a circular shaped curve. 
     In another embodiment, the controller includes a moveable human machine interface (HMI) controller having a serrated cable clamp. 
     In yet another embodiment, the serrated cable clamp includes at least one or more rounded peaks on one side of a cable receiving slot corresponding to at least one or more rounded troughs on another side of the cable receiving slot and a cable receiving slot rounded end. 
     In yet another embodiment, the low noise micro environmental workspace comfort unit further comprises further comprises at least one air cooling coil disposed behind the heated air fan. The at least one air cooling coil flows a cooling fluid or a refrigerant there through the at least one air cooling coil so that as controlled by the controller, the heated air fan provides a cooled air flow and/or a heated airflow to a person working at the workspace. 
     According to another aspect, a low noise micro environmental workspace comfort unit for a workspace includes a comfort unit enclosure having a mounting flange to mount the comfort unit enclosure to a surface of a workspace. At least one louver mechanically coupled to the comfort unit enclosure provides an ambient air flow to a person working at the workspace. A controller accepts a set point from a person working at the workspace, the set point representing a desired rate of ambient air flow. At least one ambient air fan is mounted to a wall of the comfort unit enclosure and electrically coupled to a fan speed control module. The fan speed control module is operatively coupled to the controller. At least one heated air fan mounted to the wall or another wall of the comfort unit enclosure at a different place than the at least one ambient air fan, each of the at least one heated air fan includes a heating element mechanically coupled to the heated air fan. At least one heated air outlet flows air heated by the heated air fan to provide a heated air flow to a person working at the workspace. 
     In one embodiment, the fan speed control module includes a solid state relay (SSR), the SSR operatively coupled to an output terminal of the controller. 
     In another embodiment, the SSR is controlled by a pulse width modulation (PWM) provided by the controller. 
     In yet another embodiment, the ambient air fan is controlled by a phase angle controlled SSR. 
     In yet another embodiment, the controller is programmed to operate the SSR at a plurality of pre-determined set points that have an optimized combination of low fan noise and high air flow. 
     In yet another embodiment, the controller is programmed to prevent a user from selecting an ambient air fan speed below a predetermined lowest fan speed associated with fan stall. 
     In yet another embodiment, the controller provides a person working at the workspace a plurality of ambient air fan speed settings predetermined to have a low fan noise and high air flow. 
     In yet another embodiment, the low noise micro environmental workspace comfort unit further includes a desk surface electric lift mechanism to set a height of a desk surface. 
     In yet another embodiment, the ambient air fan includes a static pressure of about 0.1 inches or greater. 
     In yet another embodiment, the at least one louver is coupled to the comfort unit enclosure by an air duct mechanically coupled to at least one hose flange disposed on the comfort unit enclosure. 
     In yet another embodiment, the low noise micro environmental workspace comfort unit further includes a proximity sensor communicatively coupled to the controller and wherein the controller places the low noise micro environmental workspace comfort unit in a low power mode when the proximity sensor does not sense a person at the workspace. 
     In yet another embodiment, the heating element includes a heated coil. 
     In yet another embodiment, a power level of the heated coil is controlled by a controller PWM control terminal which is electrically coupled to a SSR that powers the heated coil wherein the power level is set by a slider control displayed on a touch screen of the controller. 
     In yet another embodiment, the low noise micro environmental workspace comfort unit further includes at least one accessory outlet protected by a circuit breaker. 
     In yet another embodiment, the low noise micro environmental workspace comfort unit further includes at least one AC powered task light dimmable by a PWM controlled SSR or a phase controlled SSR. 
     In yet another embodiment, the SSR includes a DC voltage control input terminal. 
     According to yet another aspect, a method for minimizing fan noise of a low noise micro environmental workspace comfort unit includes: providing a low noise micro environmental workspace comfort unit including a solid state relay (SSR) fan speed circuit operatively coupled to a comfort unit controller having a comfort unit controller PWM output terminal, the comfort unit controller to set a PWM waveform at a comfort unit controller output terminal; generating a PWM frequency between about 12 Hz and 250 Hz at the comfort unit controller PWM output terminal; measuring a fan noise sound level and a fan air speed at the PWM frequency; repeating the step of generating to the step of measuring between a fan speed above about a fan stall speed and about a maximum fan air flow; determining a set of PWM frequencies having a minimal fan noise and maximum fan air flow for each of a predetermined number of discrete fan speed settings; and configuring a firmware or software stored on a non-volatile memory and that runs on the comfort unit controller, so that the comfort unit controller provides a person working at the low noise micro environmental workspace comfort unit, a selection of a fan speed from a set of discrete fan speed settings. 
     The foregoing and other aspects, features, and advantages of the application will become more apparent from the following description and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the application can be better understood with reference to the drawings described below, and the claims. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles described herein. In the drawings, like numerals are used to indicate like parts throughout the various views. 
         FIG. 1  shows an isometric view of an exemplary embodiment of a low noise micro environmental workspace comfort unit; 
         FIG. 2A  shows a front view of the low noise micro environmental workspace comfort unit of  FIG. 1 ; 
         FIG. 2B  shows a top view of the low noise micro environmental workspace comfort unit of  FIG. 1 ; 
         FIG. 2C  shows a side view of the low noise micro environmental workspace comfort unit of  FIG. 1 ; 
         FIG. 2D  shows a view of another side of the low noise micro environmental workspace comfort unit of  FIG. 1 ; 
         FIG. 3  shows an isometric of the low noise micro environmental workspace comfort unit of  FIG. 1  mounted in workstation surface. 
         FIG. 4  shows exemplary mounting dimensions for workstation surface; 
         FIG. 5  shows an isometric view of another exemplary embodiment of a low noise micro environmental workspace comfort unit; 
         FIG. 6A  shows a front view of the low noise micro environmental workspace comfort unit of  FIG. 5 ; 
         FIG. 6B  shows a top view of the low noise micro environmental workspace comfort unit of  FIG. 5 ; 
         FIG. 6C  shows a side view of the low noise micro environmental workspace comfort unit of  FIG. 5 ; 
         FIG. 6D  shows a view of another side of the low noise micro environmental workspace comfort unit of  FIG. 5 ; 
         FIG. 7  shows an exemplary installation of a low noise micro environmental workspace comfort unit of  FIG. 5  to the underside of a workstation surface; 
         FIG. 8  shows the relatively small foot print of the low noise micro environmental workspace comfort unit of  FIG. 5  on the workstation surface. 
         FIG. 9A  shows an internal front view of one exemplary embodiment of the low noise micro environmental workspace comfort unit of  FIG. 1 ; 
         FIG. 9B  shows a more detailed view of the environmental workspace comfort unit of  FIG. 9A  showing more detail of the section below bulkhead; 
         FIG. 10  shows an exemplary graph of PWM frequency and CFM for various identified fan set points; 
         FIG. 11A  shows a block diagram of one exemplary embodiment of a fan speed controller based on a phase angle controlled solid state relay (SSR); 
         FIG. 11B  shows a task lighting block diagram element; 
         FIG. 12  shows a graph of fan RPM versus DC voltage applied at the input control terminal of phase angle controlled SSR; 
         FIG. 13  shows a side cut away view of an exemplary embodiment of a micro environmental workspace comfort unit with air conditioning coils and a heat reflector; 
         FIG. 14  shows a dimetric view cutaway drawing of the exemplary micro environmental workspace comfort unit of  FIG. 13 ; 
         FIG. 15A  shows an isometric view of the rear side of an exemplary heat reflector; 
         FIG. 15B  shows a top view of the heat reflector of  FIG. 16A ; 
         FIG. 15C  shows a front view of the heat reflector of  FIG. 16A ; 
         FIG. 15D  shows a side view of the heat reflector of  FIG. 16A ; 
         FIG. 16A  is a drawing showing an isometric view of an exemplary HMI controller; 
         FIG. 16B  shows a top view of the controller of  FIG. 17A ; 
         FIG. 16C  shows a front view of the controller of  FIG. 17A ; 
         FIG. 16D  shows a front view of the controller frame of  FIG. 17A ; 
         FIG. 16E  shows a side view of the controller of  FIG. 17A ; and 
         FIG. 16F  shows a rear view of exemplary HMI controller with a serrated cable clamp. 
     
    
    
     DETAILED DESCRIPTION 
     As described hereinabove, there has been an increasing trend away from personal offices towards workstations in open spaces. Unfortunately, such workstations in open spaces are often less comfortable because of an overall need for heating ventilation and air conditioning (HVAC) energy conservation and cost savings. Or, in other open space work areas, because of an industrial setting, such as a factory floor or a warehouse, it is not possible to provide a comfortable office like working environment. Workers at desks in such open spaces may be uncomfortable for hours at a time leading to lower morale and lower worker productivity. 
     Noise, more particularly fan noise, has been a problem with prior art comfort systems. Most of the noise is from the fans in or near the personal environmental unit, which is physically close to the worker. For example, as described by Demeter, et. al. in U.S. Pat. No. 4,872,397, the fan noise can be so distracting or annoying that a white noise generator can be used to help mask noise from the personal environmental module as well as from nearby workstations. 
     Another problem with prior art personal environmental modules, such as the unit described by Demeter is the need for external duct work to convey comfort air from the unit to the workstation. In densely enclosed workstations, such as, for example,  911  emergency services operator stations, where there can be densely packed communications equipment, telecommunications equipment, and associated interconnecting cables. Retrofitting such a workstation where external ductwork is needed within the workstation can be costly, time consuming, and potentially damaging to the equipment and cables. Therefore, there is a need for a low noise micro environmental workspace comfort unit without external ductwork. 
     A solution to the problem of fan noise is a new fan power control system which significantly reduces fan noise while optimizing air flow. In some embodiments, with various low noise solutions, the fans can be mounted closer to the worker and exhaust ports eliminating the need for external duct work. Also, with the new low noise fan approaches described hereinbelow, the white noise generator is no longer needed to mask fan noise. 
     Another problem with prior art environmental modules is the need for dampers for active mixing of air streams. For example, in some prior art solutions, a pre-conditioned source of heated air is actively mixed with another source recirculated room air to achieve a desired temperature. Active mixing by controlled dampers adds extra complexity and cost. 
     It was realized that the active mixing system, including components such as controlled baffles can be eliminated. In a more cost effective, more efficient, and less complex solution, the new system solution described hereinbelow uses at least one fan dedicated to heating and temperature control, and at least one fan dedicated to ambient air (room air) recirculation. The resultant new structure has fewer components (e.g. no need for active air flow mixing as by controllable baffles), while performing the same functions of temperature control and air recirculation. For example, in some embodiments, air from one main inlet is split into two paths, one path for cooling air above the desk and one path for heating air below the desk. In the new system described in detail hereinbelow, there is no need for temperature control through active mixing of air streams because there is a dedicated fan for air circulation and a dedicated fan for heated air. With separate dedicated fans for air recirculation and for heated air, circulation air flow can be direct air above the desk separate from heated air directed below the desk, there is no need for damper controlled active air mixing. In other words, the same comfort air flow functions can be achieved with fewer components. 
     Another problem is that workspace comfort systems are inefficient because of waste heat or waste cooling of the enclosure cause wasteful heating and/or cooling of the enclosure and lost energy through the back of the unit. It was realized that a curved heat reflector installed in a micro environmental workspace comfort unit can both reflect otherwise lost heat energy to or from a person working at the micro environmental workspace comfort unit as well as to more efficiently direct the heating and/or cooling airflow to the person. 
     Yet another problem is the lack of air conditioning in prior art workstation comfort units. It is contemplated that an air cooling feature could be added to a micro environmental workspace comfort unit such as, for example, by chilled water flowing through one or more coiling coils, or by more traditional air conditioning means, such as an evaporator direct expansion (DX) coil in the environmental workspace comfort unit operatively coupled to an external condenser unit by HVAC techniques know in the art. One possible problem with plumbing pipe runs to an external condenser is that the colder liquid return pipe might introduce condensation problems along the run, such as through sensitive electrical, electronic, and/or mechanical equipment near the micro environmental workspace comfort unit. Therefore, a chilled water type solution is believed to be preferable over a conventional refrigerant solution because there is no need for long pipe runs to the external condenser, typically placed outside of the building. A chilled water solution has plumbed to one or more water cooling coils any suitable source of water of a low enough temperature to effect cooling by flowing air over one or more cooling coils optionally including metal thermal fins. It is contemplated that such cooling coils could be mounted, for example, behind the heated air fan with or without additional metal heat transfer fins. In some installations, an existing cold water source or cold water tap may be of sufficiently low temperature to provide the needed cooling. In other installations, a local water chiller of any suitable type can be used. Such a local water chiller could be installed within the housing of the micro environmental workspace comfort unit. A remote water chiller could also be used, however would have associated possible problems of condensation along a supply pipe as discussed hereinabove. A chilled water solution could be open loop with water returning to a water drain or closed loop where the water continuously circulates, or a combination of the two techniques. Another additional element could be a local water condensation drain pipe which may or may not be difficult to add depending on the proximity of the workstation to a local drain or exterior wall. Where air cooling is used, usually either the air conditioning or heating mode is used to cool or heat, however it is also contemplated that both the heated coil and the cooling coil of the air conditioner could also be operated simultaneously to effect changes in humidity. A local water drain would be added to remove condensation from the local cooling pipes with optional thermal fins. 
       FIG. 1  shows an isometric view of one embodiment of the low noise micro environmental workspace comfort unit  100 . Comfort air is available at top adjustable louvers  103  of panel  110 . Warmed comfort air is available at lower warm air vents  102 . Main power switch  107  switches low noise micro environmental workspace comfort unit  100  on or off. Touch screen controller, such as, for example, a color touch screen controller  105  is programmed to run firmware and/or software to control the low noise micro environmental workspace comfort unit  100 . Motion sensor  106 , is operatively coupled to touch screen controller  105  so that that the low noise micro environmental workspace comfort unit  100  can be automatically powered down by turning off some or all systems of the low noise micro environmental workspace comfort unit for energy savings when a person is not in the immediate vicinity of the workstation. On one side of the low noise micro environmental workspace comfort unit  100 , workstation lighting outlets  133 ,  134  provide AC electrical power for workstation lights. The lighting outlets  133 ,  134  are protected by a lighting circuit breaker  135 . Internal fans and wiring are contained within and protected by front panel  130 , side panels  135 , and lower panel  140 . 
       FIG. 2A  shows a front view of the low noise micro environmental workspace comfort unit  100  of  FIG. 1 . 
       FIG. 2B  shows a top view of the low noise micro environmental workspace comfort unit  100  of  FIG. 1 . Trim bezel  120  can be used to mount the low noise micro environmental workspace comfort unit  100  to a workstation surface as well as to provide an aesthetically pleasing transition between a surface of the workstation and the low noise micro environmental workspace comfort unit  100 . 
       FIG. 2C  shows a side view of the low noise micro environmental workspace comfort unit  100  of the opposite side which is not visible in  FIG. 1 . Additional AC power outlets include an IEC power cord receptacle  142  (typically used to power computer equipment, such as computer monitors), and auxiliary AC power outlet  143 . Auxiliary AC power outlet  143  is protected by an auxiliary circuit breaker  144 . The low noise micro environmental workspace comfort unit  100  is protected by main circuit breaker  145 . For embodiments with a leg lift, there is also a leg lift interface connector  146 . A motorized lift mechanism, such as, for example, a Linak™ lift control available from LINAK U.S. Inc. of Louisville K., provides remote electrically controlled desk height adjustment. The operation of the electric lift mechanism is typically controlled by the controller  105 . 
       FIG. 2D  shows a view of the other side of the low noise micro environmental workspace comfort unit  100  including the lighting outlets  133 ,  134  which are protected by a lighting circuit breaker  135 . 
       FIG. 3  shows an isometric of the exemplary low noise micro environmental workspace comfort unit  100  of  FIG. 1  mounted in workstation surface  300 . 
       FIG. 4  shows an example of mounting dimensions for workstation surface  300 . 
       FIG. 5  shows an isometric view of another exemplary embodiment of a low noise micro environmental workspace comfort unit  500 . In the embodiment of  FIG. 5 , there can be air ducts to route the ambient air circulation to louvers elsewhere in a workstation. Any suitable air flow connection system, such as, for example, exhaust ducts, air ducts, and/or air hoses of any suitable diameter can be used. Such hoses can be coupled to flanges  513 . Front cover  530  and side covers  531  cover the internal wiring and components of the low noise micro environmental workspace comfort unit  500 . Another difference is that mounting flange  561  can be used to mount a low noise micro environmental workspace comfort unit  500  to a lower surface of a workstation table for an under the top surface mount, with only upper bezel  520  and the controls visible above the top surface of the workstation for a lower profile installation. 
       FIG. 6A  shows a front view of the low noise micro environmental workspace comfort unit  500 .  FIG. 6C  shows a side view of the low noise micro environmental workspace comfort unit  500 , and  FIG. 6D , a view of another side of the low noise micro environmental workspace comfort unit  500 . The features on the sides are the same as were described hereinabove with respect to  FIG. 2A ,  FIG. 2B ,  FIG. 2C , and  FIG. 2D , except for the under surface mounting structure (mounting flange  561 , and bezel  520 ) and the flanges  513  for ambient air distribution. 
       FIG. 6B  shows a top view of the low noise micro environmental workspace comfort unit  500 . Mounting slots  637  can be used to bolt the low noise micro environmental workspace comfort unit  500  to the underside of a workstation surface (e.g. under a desktop surface) using any suitable fasteners, such as, for example, wood screws or sheet metal screws. 
       FIG. 7  shows an exemplary installation of a low noise micro environmental workspace comfort unit  500  to the underside of a workstation surface  701 . Air ducts  717  connect ambient air flanges  513  to louvers  703 . In the exemplary embodiment of  FIG. 7 , louvers  703  are spaced further apart on the workstation surface  701  than the width of workspace comfort unit  500 .  FIG. 8  shows the relatively small foot print of a low noise micro environmental workspace comfort unit  500  on the workstation surface  701 . 
       FIG. 9A  shows an internal front view of one embodiment of the low noise micro environmental workspace comfort unit  100  of  FIG. 1 . In the embodiment of  FIG. 9A , there are two separate comfort fans, ambient air fan  971  and heated air fan  951 . 
       FIG. 9B  shows a more detailed view of one exemplary embodiment of the environmental workspace comfort unit  100  of  FIG. 9A  showing the section below bulkhead  921 . Heating coil  901  can be seen mounted to heated air fan  951  by heating element brackets  902 . Heating element brackets  902  can use any suitable high temperature material, such as, for example a ceramic material to support the heating coil  901 . Terminal strips  931  and  932  allow for environmental workspace comfort unit  100  wiring, such as, for example, by use of industry standard push on electrical crimp lugs. The heating coil  901 , heated air fan  951  assembly can be seen mounted to an assembly mounting bracket  961  (e.g. a sheet metal strap), such as, for example, by bolts  957 , nuts  955 , and heating assembly bracket  959 . The assembly mounting bracket  961  can be mounted to a wall of the low noise micro environmental workspace comfort unit  100  by any suitable fasteners, such as, for example, by rivets  953 . 
     In the exemplary embodiments of  FIG. 9A  and  FIG. 9B , the lower heated air fan  951  is for comfort heating of the desk user&#39;s feet and legs. The top ambient air fan  971  is for sending ambient air at the desk user&#39;s face or torso. Both fans operate independently of each other. The lower heated air fan  951  can operate at constant speed while control of its heating element heating coil  901  can be variable. There are two bottom mounted rotatable louvers (e.g.  102 ,  FIG. 1 ) that can direct the warm air as needed. In the exemplary embodiment of  FIG. 9B , the lower heated air fan  951  is controlled by an on/off control via a solid state relay (SSR). Generally, no noise reduction circuit is used for heated air fan  951  because only one relatively low noise fan speed is used. However, the upper larger air circulation fan is typically operated at variable pre-determined fixed speeds and does use the new noise reduction circuitry and techniques. The upper fan discharges through louvers  103 ,  FIG. 1 , or louvers  513 ,  FIG. 6A . 
     Fan noise: At least one fan in a micro environmental workspace comfort unit should have a variable fan speed. One problem is that prior art methods of micro environmental workspace comfort unit fan speed control make sounds ranging from an oscillatory sound to a rumble. Such sounds can be distracting or even annoying to the worker at the desk or workstation. Also, such as in the case of a  911  operator or an remotely controlled aircraft or drone in contact with air traffic controllers, any additional sounds in the workspace can interfere with efficient error free communications. 
     As described hereinabove, one solution to the fan noise problem taught by the &#39;397 patent added a white noise generator to mask fan noise. While helping to mask the unpleasant aspects of prior art fan control, the white noise generator also increases the power level of total sounds and noise that the worker must contend with in trying to most efficiently carry out their assigned task. While the combination of white noise and fan noise might be less disruptive than fan noise alone, a better solution is to reduce the fan noise. 
     In some embodiments, one fan speed control technique uses a pulse width modulation (PWM) output of a controller to control a zero crossing solid state relay (SSR). Fans of with a suitable thickness (e g thin fans) with sufficient cubic feet per minute (CFM) are typically single phase AC fans (typically, not the common smaller DC (e.g. 12V DC) muffin fans found computers and other electronic equipment cabinets. Suitable AC fans include air flows of about 150 CFM or greater and static pressures of about 0.1 inches or greater. This approach effectively chops the AC power to the single phase AC fan, such as, for example, an AC powered shaded pole motor muffin fan. The result, depending on the selected fan speed, is a variety of varying types of fan noise. As one approach to fan noise suppression, we realized that there are a number of near optimal PWM settings across a range of fan speeds, for example, in a range of about 12 Hz to 15 Hz PWM and about 100 Hz to 250 Hz chopping frequency. It was realized that specific PWM frequencies with certain frequency ranges yield best fan air flow with minimal emitted fan audio sound power at each of the pre-determined fan settings to keep fan noise and fan rumble to a minimum. We also realized that most users do not desire or need a continuous range of fan speeds and that for some defined number of fan speeds, e.g. 40%, 60%, etc., low noise, high airflow (e.g. highest cubic feet per minute (CFM)) lowest noise set points could be found and defined. Such PWM frequencies can be found for a given fan type, for example, by manually sweeping the frequency PWM out of a controller or PLC while monitoring air flow and fan noise output. Never-the-less, there can still be some audible “grumble” because of the chopping of the AC sine waveform means the fans are no longer operating on the more pure 60 Hz waveform for which the electromagnet structure was originally designed.  FIG. 10  shows one exemplary graph of PWM frequency and CFM for various identified fan set points of 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 100% fan operation with minimal fan noise audio power emitted and best air flows for those set points for one exemplary type of single phase AC powered fan. 
     Another problem is fan stall. It was found that below some fan speed settings, it was possible to have a fan stop in a particular point of its rotation, where it was difficult to restart it (i.e. the fan blade stopped turning). In the embodiment described hereinabove, by locking out fan speeds below a certain lower threshold (e.g. 20%), we were able to substantially solve the fan stall problem. 
     In another embodiment, it was realized that single phase analog switching can be used to control fan speed instead of a PWM controlled SSR to chop the 60 Hz mains power waveform. One exemplary implemented control scheme uses phase angle SSRs available from Carlo Gavazzi, Incorporated of Buffalo Grove, Illinois. In one exemplary implementation, a type RM1E 1 phase analog switching SSR (part no. RM1E23V25) was used to control both the cooling fan and task lights. 
     Heater Coil Control: The heated fan, heat element can be controlled by a PWM control system. In some embodiments, heating power of the heated element (e.g. heated coil  901 ) is controlled by a pulse width modulation (PWM) control terminal of a controller which controls a zero crossing solid state relay (SSR) that powers the heating coil. In some embodiments, the PWM controlled heated coil power is set to a desired heating power by a user control, such as, for example, a slider control displayed on the LCD touch screen of the workstation controller (e.g. controller  105 ). It was realized that rather than setting a desired temperature, the person at the workstation can more simply slide the heating coil power side control set a heated air flow that is most comfortable to them at that moment. 
     example:  FIG. 11A  shows a block diagram of one exemplary embodiment of a fan speed controller based on 1 phase analog switching. A controller  1010 , here a Unitronics controller, makes a variable PWM output control waveform in the usual way as known to those skilled in the art. The PWM output control waveform is converted to a DC voltage in a range of 0 to 10 VDC by low pass filter  1012 . The phase angle controlled solid state relay  1014 , in this exemplary embodiment, a Carlo Gavazzi part number RM1E23V25 phase angle controlled solid state relay which is powered by a +24 power supply and controls by phase angle control a 115 VAC power source to provide a phase angle controlled (partial sinusoidal waveform) via wire  1021  to AC fan  1016  which also has connected thereto an appropriate AC neutral return wire path for the phase angle controlled AC waveform. 
       FIG. 11B  shows a task lighting block diagram element. The same circuit of controller  1010 , low pass filter  1012 , and phase angle controlled solid state relay  1014  can be used power a dimmable an AC light bulb  1026  by applying a phase angle controlled (partial sinusoidal waveform) via wire  1022  to AC light bulb  1026 . It is understood that the controller can have two or more PWM output terminals and that the circuit from controller  1010 , low pass filter  1012 , and phase angle controlled solid state relay  1014  can be replicated two or more times to control the fan speed of one or more fans and/or one or more dimmable AC powered lamps. 
       FIG. 12  shows a graph of fan RPM versus DC voltage applied at the input control terminal of phase angle controlled solid state relay  1014  by low pass filter  1012 . Testing of the exemplary circuit shows less fan noise and no low perceptible fan rumble or growl compared with the technique of directly using the PWM signal from the controller to fire a conventional SSR. 
     It is also contemplated that another suitable phase angle controlled solid state relay, for example, is the NuWave Technologies part number SSRMAN-1P-HR-xSS-1% available from NuWave Technologies, Inc. of Norristown, Pa. The SSRMAN series mount on top of standard Panel Mount Solid State Relays and provide phase angle and burst firing based on the selected command input (e.g. a 0-10 VDC input control voltage range). 
     In the example described hereinabove, 0-10 VDC was used to control the phase angle of the phase angle controlled solid state relay. However any suitable control signal can be developed using known techniques from a PWM output of a controller, directly via a low pass filter such as an RC filter to develop a 0 to 10 VDC control signal, or by other such known techniques directly or with or more intervening active stages (e.g. amplifier gain, offset, and/or voltage to current conversion or current to voltage conversion, to develop a current control signal (e.g. the standard 4-20 mA control range), any suitable voltage control range (e.g. 0-5 VDC), an equivalent resistance control range, etc. It is also contemplated that instead of the PWM controller output, the controller could also provide an analog voltage or analog current control signal directly to an input terminal of a phase angle controlled solid state relay. As with one or more PWM output controls, there could be two or more of any suitable type of analog output control terminal (e.g. output voltage, and/or output current) programmatically controlled (e.g. by firmware and/or software) by the controller. 
     Applications: Typical applications for a low noise micro environmental workspace comfort unit include multi-tiered desks, such as are used in  911  call centers and control stations used in industrial and military settings. However, a low noise micro environmental workspace comfort unit can also be used at any desk, such as in a traditional, cubical, or open area workspace. 
     example: One exemplary low noise micro environmental workspace comfort unit provides a cooling ambient air stream above desk of about 0-40 CFM delivered through directional louvers. Heating air stream below the desk with an air flow of about 40 CFM heat the air by a about a 0-350 watts heating element, where the heated air can be delivered through directional louvers. One exemplary unit includes: an integral Linak™ lift control, integral variable task lighting, integral ON/OFF power outlet to be used for any miscellaneous device (Andon status light, phone charger, radio, etc), controller memory for storing unique user settings, and an integral motion sensor to shut the unit off when desk is not occupied. Some embodiments with integral top air louvers serve as a complete one-piece drop-in unit. Other embodiments having air duct flanges allow for placement of the cooling ambient air supply louvers or grills farther away from the controller control panel. 
     Air Conditioning:  FIG. 13  shows a side view cutaway drawing of one exemplary micro environmental workspace comfort unit  1300  having heating coils  1303  mounted behind fan  1351  by any suitable mechanical and thermal mounting means. Fan  1351 , similar to fan  951  of  FIG. 9A  and  FIG. 9B  typically includes one or more heating elements as well for full range temperature control. Micro environmental workspace comfort unit  1300  is shown mounted below a table or desk surface  1360 . 
       FIG. 14  shows a dimetric view cutaway drawing of the exemplary micro environmental workspace comfort unit  1300 . 
     Heat Reflector: It was realized that a micro environmental workspace comfort unit can more efficiently transfer heat to and from a worker sitting or standing near the unit by installing a curved reflector.  FIG. 13  shows an exemplary curved reflector  1301 . The curved reflector  1301  is mounted adjacent to a back wall  1315  between the back wall  1315  and fan  1351 . In the heating mode, the curved reflector  1301  reflects heat, including infrared (IR) radiation from a heating element (e.g. heating coil  901 , not shown in  FIG. 13 ) from the heating coil to the heated air stream flowing out of the micro environmental workspace comfort unit  1300  towards the user, as well as towards the front of the unit and air vents  102 . In contemplated embodiments of a micro environmental workspace comfort unit having an air conditioning feature such as exemplary micro environmental workspace comfort unit  1300 , the reflector helps to direct heat energy and IR radiation from the user side of micro environmental workspace comfort unit  1300  to the cooling coils. A curved reflector  1301  can also help to more efficiently direct airflow from fan  1351  to air vents  102  by, for example, directing air flow along the curved path defined by the curved surface of reflector  1301 . The air flow so directed, avoids some of the turbulence associated with the otherwise squared corner surfaces of the micro environmental workspace comfort unit enclosure. 
     A heat reflector  1301  can be formed from any suitable material, such as, for example, any suitable sheet metal by any suitable metal forming means. 
       FIG. 15A  to  FIG. 15D  show several views of an exemplary micro environmental workspace comfort unit reflector  1301 .  FIG. 15A  shows an isometric view of the rear side of an exemplary reflector  1301 . Two sides of the reflector  1301 , here the top and bottom sides, are bent at more than 90 degree angles form mounting flanges  1511 . In the exemplary embodiment of  FIG. 15A , each mounting flange has two mounting holes  1513  for fasteners. Any suitable fastener or fastening system can be used, such as for example, PEM™ nuts, which can be press fit into the mounting holes.  FIG. 15B  shows a top view,  FIG. 15C  a front view, and  FIG. 15D  a side view of the reflector  1301  of  FIG. 15A . 
     Example: In one exemplary embodiment, the heat reflector was about 11 inches wide by about 8 inches high. The flanges were about 1.4″ wide with the two mounting holes spaced about 4.5″ apart on each mounting flange. The curve approximated a section of a circle with a radius of about 6″. As shown in  FIG. 13  and  FIG. 14 , the midpoint of the curve was located about half way between the back of fan  1351  and the back of air vents  102 . The top of the curve was placed at about the height of the top of the fan  1351 , and the bottom of the curve was placed about at the bottom of the air vents  102 . In addition to efficiently reflecting heat towards the user which would otherwise have been lost by radiation to other parts of the micro environmental workspace comfort unit  1300 , the curve of the heat reflector  1301  also more efficient directed air flow from fan  1351  to air vents  102 . 
     Exemplary Desk human machine interface (HMI) controller:  FIG. 16A  shows an isometric view of an exemplary HMI controller  1600 . One difference between the HMI controller  1600  of  FIG. 16A  and the color touch screen controller  105  of  FIG. 1  which is fix mounted into panel  110 , is that the moveable HMI controller  1600  of  FIG. 16A  can slide freely over a desk surface to any available desired position on the desk. The HMI controller  1600  can have an acrylic front sheet with button labels for the touch sensitive buttons (e.g. capacitive touch buttons which are well known in the art) and other labeling such as pertaining to a numeric display, along with arrows to select functions.  FIG. 16B  shows a top view,  FIG. 16C  a front view,  FIG. 16D  a front view of a frame to hold the controller front panel, and  FIG. 16E  shows a side view.  FIG. 16F  shows rear view of HMI controller  1600  with a more detailed view of serrated cable clamp  1601 . In this exemplary embodiment, serrated cable clamp  1601  is a tabbed element on the back of HMI controller  1600  which secures and holds an attached HMI controller communication cable (not shown in  FIG. 16F ). Serrated cable clamp  1601  prevents the communication cable from being tugged out of a socket  1602  on the back of the front panel of HMI controller  1600  when someone moves the HMI controller  1600  around the desk. In the exemplary embodiment of serrated cable clamp  1601 , a slot  1611  receives the communication cable includes rounded peaks  1613  on one side of the slot  1611  corresponding to troughs  1615  on the other side of slot  1611 . Then end of slot  1611  is finished with a rounded end  1617 . The features of serrated cable clamp  1601  including rounded peaks  1613 , corresponding to troughs  1615 , and rounded end  1617  serve both to positively capture the communication cable as a cable strain relief, as well as to prevent chaffing or other damage to the communications table as the HMI controller  1600  is moved around the desk. 
     The firmware and/or software which controls a low noise micro environmental workspace comfort unit is typically provided on, or stored on, a computer readable non-transitory storage medium. A computer readable non-transitory storage medium as non-transitory data storage includes any data stored on any suitable media in a non-fleeting manner Such data storage includes any suitable computer readable non-transitory storage medium, including, but not limited to hard drives, non-volatile RAM, SSD devices, CDs, DVDs, etc. 
     It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.