To ensure continuous ventilation in a solar plant battery room with an AC unit and a persistent smell, you should implement a dedicated ventilation system separate from the building's HVAC

 To ensure continuous ventilation in a solar plant battery room with an AC unit and a persistent smell, you should implement a dedicated ventilation system separate from the building's HVAC. This system should focus on exhausting potentially harmful gases and odors, while also providing fresh air intake. Consider using a combination of passive and forced ventilation, potentially incorporating an energy recovery ventilator (ERV) to improve energy efficiency. 

Here's a more detailed approach:

1. Separate Ventilation System:

Code Requirements:

The National Electrical Code (NEC) and NFPA 70 require battery rooms to have ventilation systems to prevent gas accumulation. These systems should be independent of the building's HVAC to avoid cross-contamination. 

Exhaust:

Install exhaust fans or vents at high points in the room to remove lighter-than-air gases like hydrogen, which can accumulate near the ceiling. 

Intake:

Provide a fresh air intake source, preferably at a lower level, to replace the exhausted air and create a flow pattern. 

2. Ventilation Types:

Passive Ventilation:

If feasible, utilize natural airflow by ensuring proper placement of vents and openings. 

Forced Ventilation:

Use fans or blowers to actively circulate air, particularly important for larger battery banks or enclosed spaces. 

Energy Recovery Ventilation (ERV):

Consider an ERV, which can recapture energy from the exhaust air to pre-cool or pre-heat incoming fresh air, improving energy efficiency. 

3. Addressing the Smell:

Identify the Source:

Determine the origin of the smell. It could be from battery off-gassing, a malfunctioning AC unit, or even a dead animal in the ductwork.

Professional Diagnosis:

If you can't pinpoint the source, consult with an HVAC professional or battery specialist to diagnose the problem and recommend solutions.

Air Purification:

Consider air purifiers or deodorizing sprays as a temporary measure, but address the underlying ventilation and potential equipment issues for a long-term solution. 

4. Additional Considerations:

Battery Type:

Ventilation requirements vary based on battery chemistry (e.g., lead-acid, lithium-ion). 

Safety:

Ensure proper grounding, protection from sparks, and availability of safety equipment like eyewash stations. 

Monitoring:

Consider temperature sensors and alarms to monitor ventilation effectiveness and potential issues. 

Maintenance:

Regularly inspect and clean ventilation components, including filters, fans, and ducts, to ensure optimal performance.