Photocatalyst air purification system with ultraviolet light emitting diodes operated with a duty cycle

A method for converting volatile organic compounds (VOC) in an airflow, comprising:

• directing air through an airflow channel;
• determining a target conversion rate of VOC in the air;
• determining a non-zero target concentration of organic by-products of said conversion in the air;
• generating with a controller, a power control signal indicative of a power duty cycle of an ultraviolet light emitting diode, the duty cycle determined, at least in part, as a function of the target VOC conversion rate and the target organic by-product concentration;
• powering a ultraviolet light emitting diode at the duty cycle;
• directing the air into contact with a photocatalyst, the photocatalyst disposed in the airflow channel;
• irradiating the photocatalyst with ultraviolet light from the ultraviolet light emitting diode;
• and
• adjusting the power control signal to reduce the duty cycle if air emerging from the airflow channel has a concentration of the organic by-products lower than the non-zero target concentration, so that the power applied to the ultraviolet light emitting diodes is minimized.

A system for converting volatile organic compounds (VOC) in an aircraft, comprising:

• an aircraft cabin,
• an airflow channel including an inlet and an outlet, both the inlet and the outlet fluidly connected to the cabin;
• a support disposed in the airflow channel;
• a photocatalyst on the support disposed to contact airflow through the airflow channel passing across or through the support;
• an ultraviolet light emitting diode disposed to emit ultraviolet light onto the photocatalyst;
• a power source selectively electrically connected to the ultraviolet light emitting diode to provide current to the ultraviolet light emitting diode at a duty cycle at a frequency low enough to permit the ultraviolet light emitting diode to fully complete high to low cycles;
• and
• a controller configured to generate the duty cycle control signal at least in part as a function of a target VOC conversion rate in air flowing through the airflow channel and a target concentration of organic by-products of conversion of VOC in air flowing through the outlet of the airflow channel.