Abstract: A wave energy converter (100) is provided which comprises a heaving buoy point absorber (122) having a surface piercing float (120) operably coupled to an adjustable reference mass (125) defining a volume for accommodating sea water therein. The surface piercing float and the adjustable reference mass are configured to move together in response to passing waves. A chamber (105) provided within the surface piercing float is in fluid communication with the sea for trapping a volume of air above an enclosed column of water. The height of the enclosed column of water varies as the point absorber reacts against its surface via an adjustable air-spring. A power take off (140) is configured for being driven by a stream of vented air in communication with the chamber as the heaving buoy point absorber reacts against a trapped volume of air. A control mechanism is configured for tuning one or more operating characteristics of the heaving buoy point absorber.

Abstract: An engine for converting thermal energy to kinetic energy is provided. The engine includes a first zone and a second zone and a movable loop, which extends between the first zone and the second zone. Containers are attached to the loop such that the loop and the containers are movable conjointly between the first zone and the second zone. Each of the containers is adapted to receive a varying amount of a working fluid therein and is adapted to be in a plurality of states, including a first state, in which it contains a first amount of the working fluid, and a second state, in which it contains a second amount of the working fluid, the first amount being smaller than the second amount. Each of the containers is caused to be in its first state as it moves through the first zone and in its second state as it moves through the second zone so as to impart motion to the loop.

Abstract: A method for installing a surface feature on a wind turbine rotor blade includes disposing the surface feature on a surface of the rotor blade with an adhesive material disposed there between, disposing a seal between at least a portion of the surface feature and the rotor blade to form a chamber there between, and, pulling a vacuum from the chamber to produce a substantially uniform force pulling the surface feature against the surface of the rotor blade.

Abstract: The assembly includes a tool with a stem having a first end having a projecting portion such as a ring, and a second end adapted to be engaged by lifting equipment. The assembly also includes a stem receiving portion formed in a wind turbine part to be lifted. The stem of the tool is adapted to be freely passed through the stem receiving portion until the first end of the stem is locked to the stem receiving portion, thereby preventing the stem from separating from the stem receiving portion when lifting the wind turbine part.

Abstract: The present invention relates to a wind turbine with a concrete tower wherein the tower comprises a plurality of sections formed by segments a platform system comprising a plurality of platforms, wherein the platform system is configured to allow access to junction areas between sections wherefrom optionally, the execution of joints between adjacent sections may be carried out, the platforms situated inside the tower once erected being detachable, stackable and transportable.

Abstract: Exemplary compact wind power generation systems are configured to be suitable for residential and other locations where concealed moving parts are desirable. The wind power generation systems utilize a propeller disposed behind a contracting inlet. The propeller blades may be oriented “into the wind” to develop consistent torque across a variety of wind speeds. The propeller may rim-drive power generation components, further reducing vibration, or may share a common rotational axis with the power generation components.

Abstract: The present disclosure is directed to spar caps for wind turbine rotor blades and methods of manufacturing same. The spar cap includes a plurality of plies having varying lengths that are arranged in a tapered configuration. Further, the tapered configuration includes at least an upper portion and a lower portion. The upper portion is configured for attachment to at least one of a pressure side or a suction side of the rotor blade. Further, one or more plies of the upper and lower portions tapers towards an intermediate ply configured between the upper and lower portions of the spar cap. In addition, the intermediate ply has a length that is shorter than the plies in the upper and lower portions.

Abstract: A rotor blade of a wind turbine having a pultruded spar cap is disclosed. The rotor blade includes a blade root and a blade tip. The blade root includes at least one root insert. The rotor blade also includes at least one spar cap constructed of a plurality of pultruded members grouped together to form one or more layers from the blade tip towards the blade root. Further, the pultruded members separate into one or more pultruded member bundles as the spar cap approaches the blade root. The pultruded member bundles fit within the root insert, along with the blade bolts, such that compression and tension loads of the rotor blade are transferred through the pultruded members.

Abstract: A vertical axis wind turbine comprising a rotor having a substantially vertical rotation axis z, said rotor comprising a plurality of blades arranged to rotate about its rotation axis z in consequence of the aerodynamic drag opposed to an air flow investing said blades. The wind turbine also comprises a casing structure in which the rotor houses. The casing structure comprises a lower plate substantially orthogonal to the rotation axis z, said lower plate defined by a first plurality of vertices V1, . . . , Vr, an upper plate substantially orthogonal to the rotation axis z, said upper plate defined by a second plurality of vertices V1?, . . . , Vn?, each vertex V1?, . . . , Vn? of the second plurality corresponding to a vertex V1, . . . , Vn of the first plurality.

Abstract: A turbine having a first set of at least three aerofoil shaped blades, a second set of at least three aerofoil shaped blades, and a substantially flat plate having an upper and a lower surface, the first set of at least three aerofoil shaped blades attached to the upper surface of the substantially flat plate and the second set of at least three aerofoil shaped blades attached to the lower surface of the substantially flat plate. The first set of at least three aerofoil shaped blades are vertically spaced and offset from the second set of at least three aerofoil shaped blades. The solidity of the turbine is from 0.5 to 5.

Abstract: The lengths and/or chords and/or pitches of wind turbine or propeller blades are individually established, so that a first blade can have a length/chord/pitch that is different at a given time to the length/chord/pitch of a second blade to optimize performance and/or to equalize stresses on the system.

Abstract: A method of operating a wind power installation is disclosed. In the method, a network frequency of an electrical network is measured and an amount of power delivered to the electrical network is controlled by at least maintaining the amount of power delivered without changing the power when the network frequency is between a rated frequency for the electrical network and a deadband frequency. Further, the amount of power is increased by a first amount when the network frequency is between the deadband frequency and a control-band frequency, whereby the first amount is proportional to a difference between the network frequency and the deadband frequency. In addition, the amount of power delivered is increased by a second amount when the network frequency is less than the control-band frequency. The second amount is a preset amount of power that is determined based on a difference between the control-band and deadband frequencies.

Abstract: A method of controlling a wind turbine having a rotor and a generator for producing power, the wind turbine being designed for a nominal load, the method comprising the steps of: determining a current load acting on at least a part of the wind turbine; calculating a load error, the load error representing the difference between the nominal load and the current load; controlling the wind turbine based on the load error; wherein the step of controlling the wind turbine comprises altering a parameter of the wind turbine so that the power or torque produced by the generator is altered.

Abstract: A wind power generator device includes: a windmill which rotates by receiving wind power; a power generator including a rotor; and a rotation transmission device which transmits rotation of the windmill to the rotor without a speed increase. The rotation transmission device includes a one-way clutch which makes a connection integrally and rotatably between the windmill and the rotor in a state in which a rotation speed of the windmill is higher than a rotation speed of the rotor, and which releases the connection in a state in which the rotation speed of the windmill is lower than the rotation speed of the rotor.

Abstract: The present invention discloses a short-term operation optimization method for a power system including large-scale wind power, comprising modeling the randomness of wind power output, modeling the randomness of the load of electric power system and modeling net load of electric power system. Net load refers that for probability distribution of net load that is too discretized, probability distribution curve of net load is divided into N intervals, the probabilities for each interval are obtained and probability distribution curve of net load is obtained through calculating and weighing each interval.

Abstract: A wind turbine is provided, with a tower with a longitudinal axis, a nacelle on the tower, multiple power cables which extend from the nacelle into the tower and a transport unit. The transport unit is fastened inside the nacelle and serves to transport loads inside the tower to the nacelle. The transport unit has a cable guide unit with multiple rings, wherein the power cables are fastened to the circumference of the rings so that a region inside the rings is kept free for transporting the load. A top ring is fastened to the nacelle and a bottom ring is fastened non-rotatably in or on the tower. The bottom ring has a non-rotatable guide along the longitudinal axis of the tower.

Abstract: A static testing and calibrating method for PID link of control system of wind turbine includes following steps. A PID control link of the PID link of the control system of wind turbine is tested. A PID regulator response characteristics is tested. The PID link of control system is calibrated by applying test results of the PID control link and the PID regulation response characteristics.

Abstract: A method of constructing wind power connection system model based on measured data includes following steps. Operating data is selected in a preset time of each wind turbine in a wind farm. A wind speed matrix and a active power matrix of sampling points are constructed based the operating data. A wind speed model of the wind farm is obtained based on the wind speed matrix and the active power matrix.

Abstract: The invention relates to a rotor of a wind turbine, comprising a rotor hub (8), which has at least one rotor blade (9, 10) protruding perpendicularly to the rotor axis (7), which at least one rotor blade can be adjusted in an angular range about the blade axis (11, 12) of the rotor blade with respect to the the blade bearing point (32) of the blade in the hub (8), and at least one sensor (18), which is connected to at least one evaluating unit (19) arranged in the hub (8) by means of a rotatable cable connection (20) suitable for energy transmission and/or communication. The cable connection (20) has at least one or more guiding elements (23). The guiding element (23) has one fastening point (24, 25) each in the rotor hub and in the rotor blade and comprises at least one element (26, 29) that is elastic in tension.

Abstract: The present invention relates to a rope-driven transmission for a wind turbine. The transmission comprises an input rotary member for being operatively connected to a rotor of a wind turbine and in rotational connection with at least one secondary shaft which is arranged in parallel with the rotational axis of said input rotary member, wherein said secondary shaft is adapted for operative connection with an output member of at least one electrical generator, wherein said rotational connection between said input rotary member and said at least one secondary shaft is provided by a rope, the course of said rope defining a rope path, and wherein said rope path includes a plurality of turns around said input rotary member and said secondary shaft. The transmission facilitates an easy monitoring and maintenance of the transmission. The invention further relates to a method of maintaining the transmission by replacing the rope. The invention further relates to a wind turbine generator comprising the transmission.

Abstract: In an air-cushioned small hydraulic power generating device, when a stator in a generator linked by means of an upper rotational shaft to a first vertical-shaft windmill rotates in a first direction, a rotor in the generator linked by means of a lower rotational shaft to a second vertical-shaft windmill and an air-cushioned water wheel rotate in a second direction opposite to the first direction, thereby increasing the rotational force and thus enhancing the power generation efficiency. The generator can be easily installed in valleys, watercourses, rivers, irrigation water channels, or seawater channels without having geographic limitation. Furthermore, since an air-cushioned water wheel is used to support the weight of the generator and rotational shafts, the generator can be easily installed to float on the surface of water. Therefore, breakdown and maintenance cost of the generator can be minimized.

Abstract: A wind energy plant is provided with a foundation base and a tower which is placed on the foundation base. The foundation base has a foundation plate below ground level and a foundation plinth on the foundation plate above ground level. On the foundation plinth a tension cord connector is provided with a plurality of bores for receiving tension cords. The tension cords are tensioned on an underneath side of the connector by means of a tension cord head. The foundation plate and the foundation plinth are cast in one piece from site-mixed concrete.

Abstract: The object is to simplify systems in a solar thermal power generation plant and thereby provide a solar thermal power generation system achieving reduction in the construction cost and the power generation cost.

Abstract: The boiling-water geothermal heat exchanger 1 is provided with a water injection pipe 2 which is installed underground and to which water is supplied from the ground and a steam extraction pipe 3 which is installed underground so as to be in contact with the water injection pipe 2 and has a plurality of ejection ports 5, in which a pressure inside the steam extraction pipe 3 is reduced to the vicinity of a pressure required by a turbine 6, high-pressure hot water which is produced by supplying heat from a geothermal region 4 to water inside the water injection pipe 2 is changed to a single-phase flow of steam inside the steam extraction pipe 3 present underground via the ejection ports 5, and the single-phase flow of steam is extracted on the ground.

Abstract: A hybrid geothermal power system is discussed. The system includes a geothermal system including power plant (101) and pumping station (102) and a nuclear plant (103). Pumping station (102) is used to inject fluid from reservoir (104) through an injection well (105) into the bedrock (106) (also referred to as the hot dry rock HDR zone) and extracted via a secondary bore (extraction well) usually coupled to the power plant (101). In the present example however the injection well is linked to the extraction well (107). As fluid is injected into the bedrock a drop in temperature occurs due to heat transfer to the fluid. Nuclear plant (103) is utilized to combat this drop, the plant (103) has the fissionable components (1091, 1092, 1093) of the reactor positioned within bores (1081, 1082, 1083) within the HDR zone.

Abstract: A scalable multi-element shape memory alloy (SMA) rotary motor employs a plurality of SMA tubes. A ratcheting gear transmission couples the plurality of SMA tubes in parallel to a common output. A controller provides power to a plurality of heaters associated with each of the plurality of SMA tubes, sequentially heating selected heaters to provide continuous rotational motion of the common output.

Abstract: A plasma propulsion nozzle incorporates a cylinder having an inlet and an outlet. A plurality of substantially cylindrical planarly disbanded electrodes with sandwiched dielectric spacers is cascaded in an array to be concentrically expanding from the inlet through an interior chamber to the outlet for a nozzle. A voltage source applies aperiodic signal with rapidly reversing polarity to the electrodes with differential phase applied to adjacent electrodes in the array creating and expelling plasma clusters at each dielectric spacer inducing flow from the nozzle outlet to produce thrust.

Abstract: A well pump includes a plunger reciprocally carried within a barrel between up stroke and down stroke positions. A tubular linear actuator housing located below the barrel has a rotatable rotor. An array of rotor magnets is mounted to the rotor, directing rotor magnetic fields in an outward direction. A cage is fixed against rotation relative to the housing and carried within the housing for axial movement relative to the rotor and the housing. The cage has a cylindrical inner sidewall surrounding the outer sidewall of the rotor. An array of cage magnets is mounted to the inner sidewall of the cage. The cage magnets direct cage magnetic fields in an inward direction relative to the axis. The cage and rotor magnetic fields interact such rotation of the rotor causes axial movement of the cage. A motor rotates the rotor.

Abstract: A compressor of the present invention comprises a crankshaft, a first compression part, and a second compression part for further compressing a gas discharged from the first compression part. The first compression part comprises a first reciprocating motion conversion part, a first pressing part, and a first cylinder body comprising a plurality of cylinder components, while the second compression part comprises a second reciprocating motion conversion part, a second pressing part, and a second cylinder body comprising a plurality of cylinder components. The number of the cylinder components of the second cylinder body is smaller than that of the cylinder components of the first cylinder body.

Abstract: A starting valve (100) for a fluid operating machine (200) for a vacuum system (1000). The starting valve (100) comprises: a valve body (10) with an opening (17) to let a gas in; and an actuating piston (13) splined on a stem (16) free to slide in a guide (18A). The actuating piston (13), with a portion of the valve body (10), defines a chamber (30). The actuating piston (13) is subject to the action of a deformable diaphragm (15). A calibrated throttling hole (16B) is provided in series with a through hole (16A) in line with the stem (16) to establish a fluid communication between the chamber (30) and a fluid-dynamic line (500) of the vacuum system (1000). A shutter (20) is furthermore provided also splined on the stem (16). The shutter (20) closes a gas passage opening (10B) as a function of the pressure difference between the chamber (30) and the fluid-dynamic line (500).

Abstract: A diaphragm pump including a pump head having at least one body plate with a pumped fluid face and at least one body plate with a drive fluid face, a diaphragm assembly positioned between the pumped fluid face and the drive fluid face, and the pumped fluid face having a positive profile biasing the diaphragm assembly in a direction toward the drive fluid face.

Abstract: The present disclosure relates to a system and method for pumping a feedstock slurry through a device. The system includes a pressure pump, a first sensor, a second sensor, a controller, and a control valve. The pressure pump includes a plunger configured to pressurize the slurry to a first pressure prior to the slurry entering the device. The first sensor is configured to sense a second pressure of the slurry entering the device. The second sensor is configured to sense the position of the plunger. The controller is configured to determine a change of position of the plunger based on the sensed position of the plunger and to control the movement of the plunger by setting a plunger mode based on the second pressure of the slurry and the change of position of the plunger. The control valve is configured to control the flow rate of the slurry through the device.

Abstract: A method for determining a through-flow quantity in a fluid delivery system, in which a fluid is delivered by a pump, the pump including an electromotor and the electromotor being operated at a first speed when the electromotor is in operation and the through-flow quantity being determined from a measured motor power and the speed. The method includes (i) increasing the first speed to a second speed which is greater than the first speed; (ii) determining a second through-flow quantity at the second speed from the motor power and the second speed; (iii) determining a third through-flow quantity from the second through-flow quantity by extrapolation of the second speed to the first speed, wherein the third through-flow quantity is the target variable; and, (iv) reducing the speed back to the first speed once the second through-flow quantity has been determined.

Abstract: Disclosed are systems and methods utilizing multiple parallel pumps to deliver a mixture of the proppant and clean fluid via a manifold trailer. One method of providing a step-change in proppant concentration includes selecting a first flow rate for a first pump connected between a first input node and first output node, calculating a first transit time for a flow of a fluid at the first flow rate through a first flow path extending from the first inlet node, through the first pump, and to the first outlet node, and calculating a second flow rate for a second pump connected between the first input node and the first output node such that a second transit time for a flow of the fluid through a second flow path extending from the first inlet node, through the second pump, and to the first outlet node is equal to the first transit time.

Abstract: A fluid-working machine has a plurality of working chambers, e.g., cylinders, of cyclically changing volume, a high-pressure fluid manifold and a low-pressure fluid manifold, at least one valve linking each working chamber to each manifold, and electronic sequencing means for operating said valves in timed relationship with the changing volume of each chamber, wherein the electronic sequencing means is arranged to operate the valves of each chamber in one of an idling mode, a partial mode in which only part of the usable volume of the chamber is used, and a full mode in which all of the usable volume of the chamber is used, and the electronic sequencing means is arranged to select the mode of each chamber on successive cycles so as to infinitely vary the time averaged effective flow rate of fluid through the machine.

Abstract: In a linear displacement pump, liquid is discharged by driving a piston along at least part of a stroke length. While discharging the liquid, a linear position of the piston is sensed at a plurality of positions along the stroke length, and a plurality of output signals is produced. Based on one or more of the output signals, an operational state of the pump is determined.

Abstract: The subject matter of this specification can be embodied in, among other things, a method that includes a gear pump includes gears having a gear root diameter and teeth having an addendum and pressure angle. A housing includes a fluid inlet and discharge, bearings configured to position the gear teeth in intermeshing contact across a fluid dam. The fluid dam includes a first face arranged at an angle to a split line, spaced apart from a center line at the split line a first distance towards the inlet, and extending from the first gear root diameter away from the center line to the first gear root diameter, and a second face arranged approximately perpendicular to the split line, spaced apart from the center line at the split line a second distance towards the outlet, and extending between the first gear root diameter and the second gear root diameter.

Abstract: A hydraulic device at least has a pair of helical gears 20, 23, a body 3 containing the gears, bearing members 40, 44 supporting rotating shafts 21, 24 of the gears 20, 23, and cover plates 7, 8, 11 liquid-tightly fixed to both end surfaces of the body. The cover plate 8 has a cylinder hole 8a formed at a portion opposite to an end surface of the rotating shaft 21 of the gear 20 which receives two thrust forces Fma, Fpa in the same direction, and a piston 9 is inserted through the cylinder hole 8a. A working liquid in a high-pressure side is caused to act on a back surface of the piston 9 and thereby the piston 9 is pressed onto the end surface of the rotating shaft 21, thereby causing a drag almost balancing a resultant force of the two thrust forces Fma, Fpa to act on the rotating shaft 21. The thrust forces Fma, Fpa acting on the gear 20 are cancelled by this drag.

Abstract: A liquid ring fluid flow machine is presented. The machine includes a stationary annular housing having an outer surface and an inner surface. The inner surface defines a chamber that is arranged to receive a liquid. A rotor having a core and a plurality of radially extending vanes is eccentrically rotatably mounted within the chamber for directing the liquid into a recirculating liquid ring in proximity to the inner surface of the housing within the chamber. The inner surface of the housing that is in contact with the recirculating liquid ring is covered by a hydrophobic coating. The machine further includes a first supply pipe and a second supply pipe, each in fluid communication with the chamber.

Abstract: A variable capacity scroll compressor includes a fixed scroll. The fixed scroll of the compressor includes a bypass flow path configured to connect a suction unit to a compression unit, a cylinder space provided on the bypass flow path, and an on/off valve disposed to be movable back and forth in the cylinder space to open/close the bypass flow path according to a difference between a discharge pressure of the discharge unit and a suction pressure of the suction unit. Thus a capacity of the compressor may be reduced by connecting the suction unit to the compression unit under a low load condition in which a difference between a discharge pressure and a suction pressure is relatively less.

Abstract: A scroll compressor is provided that may include a casing, an orbiting scroll and a non-orbiting scroll that suctions in a refrigerant from a suction space of the casing, compress the sectioned refrigerant in a plurally of compression chambers, and discharge the compressed refrigerant into a discharge space of the casing, and a capacity varying device having a first valve and at least one second valve coupled with each other inside of the casing to selectively bypass a portion of the refrigerant in the plurality of compression chambers. With this structure, it is possible to prevent, in advance, refrigerant from being leaked outside of the scroll compressor, reduce pressure loss as a bypass flow path is shortened, reduce a size, weight, and manufacturing costs of the scroll compressor, and vary a capacity of the scroll compressor with a small operating force, and small power consumption.

Abstract: A heat exchanger includes: a heat exchange section through which a compressed gas flows; an upstream header section that is provided on an upstream side of the heat exchange section and communicates with the heat exchange section; a downstream header section that is provided on an downstream side of the heat exchange section and communicates with the heat exchange section; a gas inlet pipe that is connected to a wall surface of the upstream header section; and a gas outlet pipe that is connected to a wall surface of the downstream header section. A filter-cum-sound absorbing material of a porous material is mounted on an inner wall surface of at least one of the upstream header section and the downstream header section. The inner wall surface faces the heat exchange section.

Abstract: A pump for delivering fluid has a pump housing and a pump chamber having a pump chamber cover and a pump chamber base in said pump housing, an inlet and an outlet. In the pump chamber, an impeller rotates on a rotor shaft which is connected to a drive motor. The inlet is arranged in the pump chamber cover and the outlet is arranged below the impeller in the axial direction of the pump at that end region of the pump chamber which is remote from the inlet close to the outlet. The distance from the inlet to the outlet with the impeller therebetween can correspond approximately to the diameter of the pump chamber.

Abstract: An electric pump powered by an electric motor having a stator disposed within a hollow rotor is provided. Impellers on the rotor outer surface extend into a fluid flow path defined by the pump. One or more torque-producing rotor sections are driven by a plurality of independently controllable stator sections disposed within the rotor cavity. The relative positions of the rotor and stator are maintained by a plurality of bearings configured to allow rotation of the rotor and defining a bearing span. The pump is configured such that the stator and rotor share the same bearing span. Such an arrangement reduces motor windage losses relative to conventional motors in which the rotor is disposed within the stator, owing to a reduction in the diameter of the air gap between the stator and the rotor. In addition, the peripheral speed of the pump is increased owing to an increase in the rotor diameter.

Abstract: A pump and a cleaning apparatus are provided. The pump includes a pump housing having a pump chamber, an inlet and an outlet in communication with the pump chamber, a motor, and an impeller. The motor includes a stator and a rotor. The impeller is fixedly connected to the shaft so as to always synchronously rotate along with the rotary shaft. The stator windings drag the rotor to rotate only in a fixed starting direction during a starting phase of the motor.

Abstract: The invention relates to a centrifugal compressor or supercharger with an internal drive mechanism (30), which operates with great efficiency, higher speed and low noise. The compressor needs no lubrication and has a concentric input-and impeller shaft (13) for compactness. The compressor has two sets of belt drives (36) connected to a large sprocket (33).

Abstract: An assembly can include a turbine wheel; a turbine housing that includes a lower turbine housing surface that extends from an exhaust volute to a cylindrical surface that defines an upper portion of a turbine wheel space; a shroud component that includes a contoured surface disposed between an inner end of an upper shroud component surface and an inner end of a lower shroud component surface where the contoured surface defines a lower portion of a turbine wheel space; and a seal mechanism where the turbine housing and the shroud component form an axial gap between a lower axial position of the cylindrical surface and an upper axial position of the contoured surface where the axial gap is axially positioned between an axial position of an inducer portion of the turbine wheel and an axial position of an exducer portion of the turbine wheel.

Abstract: A viscous fan drive which includes a moveable component in the scavenge or fill passageway that moves relative to pressure that is proportional to slip speed. The force which moves the component into and out of the passageway is directly proportional to the slip speed of the fan drive. This balances the fill and scavenge flow.

Abstract: A turbo compressor includes: a compressor casing which accommodates impellers compressing gas by rotation; and a motor casing which accommodates a motor rotating the impellers, wherein the motor casing has a cylindrical main body part having a larger diameter than a mounting flange provided in the compressor casing, and the compressor casing and the motor casing are connected through an adapter member.

Abstract: Apparatuses and methods are provided for protectively covering an air inlet or outlet of an air-moving assembly. The apparatus includes a protective cover assembly, which includes a retractable cover and a spring-biasing mechanism. The retractable cover transitions between a retracted state, when the air-moving assembly is operatively positioned within the chassis, and in extended state, when the air-moving assembly is withdrawn from the chassis. In retracted state, the retractable cover is retracted away from the air inlet or outlet, and in extended state, the retractable cover covers, at least partially, the air inlet or outlet. The spring-biasing mechanism is coupled to the retractable cover and biases the retractable cover in the extended state when the air-moving assembly is withdrawn from the chassis, and compresses to allow transition of the retractable cover to the retracted state as the air-moving assembly is inserted into operative position within the chassis.