Rotating shadowband pyranometer
AssigneeRWE Schott Solar, Inc.
InventorRuel D. Little
Life of this patent
Estimating the term…
Abstract
A pyranometer for measuring solar irradiance at a selected site comprises a light detector adapted to produce an output signal in response to incident solar radiation, a reversible motor having a curved shadowband attached to its output shaft, means for mounting the light detector and motor so that the shadowband is at a fixed distance from the light detector; and a motor controller that is adapted to periodically cause the motor to rotate the shadowband from one to the other of two limit positions, with the shadowband acting to momentarily shadow the light detector during its movement between its two limit positions. A datalogger stores and processes the light detector's signal output to provide a measure of total horizontal, direct normal and horizontal diffuse solar irradiance.
Claims18
A pyranometer comprising:
- a reversible electric motor having an output shaft;
- a curved flat opaque band of selected width, said band having one end coupled to output shaft so that said band can rotate in time with said output shaft and so that the axis of rotation of said band is normal to said one end thereof;
- a mount adapted to for attachment to a supporting structure so as to provide adjustment of said mount in a first degree;
- motor-support means pivotally attached to said mount so as to provide adjustment in a second degree;
- a light sensor having a light-receiving surface;
- sensor support means for supporting said sensor so that the center of said light-receiving surface is substantially coaxial with the axis of rotation of said band, said sensor support means being adapted to permit adjustment of said light sensor in a third degree;
- and
- motor control means for controlling operation of said motor so that periodically said band rotates through a selected angle from one stowed position to a second stowed position, with said stowed positions being such that said band casts a shadow on said light-receiving surface only while it is rotating.
A pyranometer comprising:
- a motor support member mounted for rotational movement on a first vertical axis;
- a motor unit attached to said motor support member for rotational movement on a second horizontal axis, said motor unit comprising a reversible electric motor having an output shaft;
- a shadow band having a selected width and first and second opposite ends, said first opposite end being attached to said output shaft so that said shadow band will rotate with said output shaft, said band being curved between said first and second opposite ends with its curvature extending through an angle of about 133 degrees;
- a sunlight sensor having a light-receiving surface;
- sunlight sensor support means spaced from said output shaft but supporting said sunlight sensor so that it is located in line with the axis of rotation of said output shaft, with the distance between said sunlight sensor and said band being substantially the same along the full length of said band;
- motor control means for controlling operation of said motor so that periodically said band rotates through a selected angle of approximately 300 degrees from one stowed position to a second stowed position, with said stowed positions being such that said band casts a shadow that fully occludes said light-receiving surface only once as it rotates between stowed positions.
A pyranometer according to claim 19 further including means responsive to said output signal for determining the direct normal irradiance Dirn according to the equation Th=Difh.+Dirn cos(Z), where Z is the sun's zenith angle.
Dependencies are inferred from the claim text.