H2Vent™ Hydrogen Venting

How to Vent Your Solar Batteries

The process of charging lead acid batteries involves passing electric current through water, contained in the electrolyte inside the battery. A natural by-product of this process is the splitting of the water into its basic components, hydrogen and oxygen, which can build up to explosive levels if hydrogen gas venting is not done properly.


Explosive mixtures can be prevented if the battery enclosure is designed to take advantage of the principles of natural convection and ventilation for hydrogen venting. The patented H2Vent™ systems from Zomeworks have been developed to vent batteries.


Principles of Natural Convection

 

The most reliable and Fail-Safe way to ventilate hydrogen from a  battery shelter is by using the principles of natural convection, taking  advantage of:


  1. The natural property of light-density gas to rise upward, and
     
  2. The heavier-density gas to sink downward

Hydrogen is less dense than air  and tends to rise upward when in contact with air. Warmer air is less  dense than cooler air, and so warm air tends to push upwards when in  contact with cooler air.


Just as a bowl will hold water when right side up, but  will not when upside down, a hydrogen ventilation system will trap  hydrogen unexpectedly if the geometry is arranged upside down or  backwards.


These natural principles can be put to good use by the proper use of  vents, ducts, heat exchangers and other components. But only the right  combination of components will provide effective and fail-safe hydrogen  ventilation.

The Presence of Hydrogen

The ideal hydrogen ventilation system should work only when hydrogen is present and not otherwise. It should not provide constant ventilation, this avoids the extra heating and cooling problems. It should not require a fan or electrical components that are prone to failures. It should not react to air temperature, only the presence of hydrogen.


The following are five different configurations intended to ventilate hydrogen from a battery box, but only one is not fatally flawed:

Example 1:

Shows how a Fan can be used, but in the inevitable  event of mechanical and electrical failure, ventilation would cease and  the box would become a hydrogen trap

Example 2:

 Shows how High and Low vents can be used, but this is  not very well regulated, allowing too much outside air into the battery  shelter, creating extreme temperatures and creating a hydrogen trap at times when the inside is cooler than the outside. 

Example 3:

Shows how a small chimney (called a riser tube) can be  used with a low vent to trap warm air in the battery box. Unfortunately  this system acts as a very effective and dangerous hydrogen trap as well. 

Example 4:

Shows how a riser tube and a high vent can be used, but  this will only ventilate effectively when the inside is warmer than the  outside. At other times it, too, will become a dangerous hydrogen trap 

Example 5:

Shows that when the chimney is reversed (now called a dip tube), and high vents and a heat exchanger are properly arranged, that hydrogen is ventilated without any of the drawbacks or failures of the other 4 examples.