# pvl_iam_martinruiz

Determine the incidence angle modifier using the Martin and Ruiz model.

## Contents

- Syntax
- Description:
- Inputs
- Output
- Example
- References
- See also

## Syntax

- `IAM = pvl_iam_martinruiz(ar, theta)`

## Description:

`pvl_iam_martinruiz` calculates the incidence angle modifier (IAM) as described in [1] and clarified in [2]. The incidence angle modifier quantifies the fraction of direct irradiance incidence on a module's surface that is not reflected away. The incidence angle modifier is computed as

,

Thus at , and at .

## Inputs

- `ar` - The angular losses coefficient described in equation 3 of [1]. `ar` is an empirical dimensionless parameter with values generally on the order of 0.08 to 0.25 for flat-plate PV modules. `ar` must be a numeric scalar or vector with all values > 0. If `ar` is a vector, it must be the same size as all other input vectors.
- `theta` - The angle of incidence between the module normal vector and the sun vector in degrees. `theta` must be a numeric scalar or vector. For any values of `theta` where `abs(theta)>90`, `IAM` is set to 0. For any values of `theta` where -90 < `theta` < 0, `theta` is set to `abs(theta)` and evaluated. A warning will be generated if `any(theta<0 or theta>90)`.

## Output

- `IAM` - The incident angle modifier. `IAM` is a column vector with the same number of elements as the largest input vector.

## Example

This example plots the IAM for glass over a range of incident angles.

    ar = 0.15;       % empirical losses coefficient of 0.15
    theta = 0:90;    %incident angle in degrees
    IAM = pvl_iam_martinruiz(ar, theta);
    figure
    plot(theta,IAM)
    xlabel('Incident Angle (deg)')
    ylabel('IAM')
    title('Martin and Ruiz IAM Model Example')

## References

[1] N. Martin and J. M. Ruiz, 2001. Calculation of the PV modules angular losses under field conditions by means of an analytical model, Solar Energy Materials & Solar Cells, vol. 70, pp. 25-38.

[2] N. Martin and J. M. Ruiz, 2013. Corrigendum to 'Calculation of the PV modules angular losses under field conditions by means of an analytical model', Solar Energy Materials & Solar Cells, vol. 110, pp. 154.

## See also

`pvl_getaoi` , `pvl_ephemeris` , `pvl_spa` , `pvl_iam_ashrae` , `pvl_iam_physical`

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