You can get better thermal efficiency when you harvest high-grade waste heat from power plant than harvesting electric power from mechanical vibration. The latter technology would need large capacitors to store the harvested power to charge backup batteries.

Backup power for critical control systems in power plants require reliable sources of power and, thus, harvesting mechanical vibration would not a proper source of power for this purpose.

Hope this helps answer your question.

Professor Yehia Khalil

Yale University

USA

Dear Prof. Khalil,

Thanks for your valuable suggestion.

Yes. Harvesting waste heat is a better solution than harvesting mechanical vibration in case of power plants. I would like to get your advice in application of hybrid energy harvesting system which can harvest from multiple sources like heat and vibrations, for powering critical control systems.

Mostly in power plants, critical control systems is powered by either battery banks or UPS from a remote location. What can be the possible safety hazards, if I provide a local energy harvesting power supply (with a high reliable battery backup) for each control system cabinets?

Thank you.

Praveen K

Hello.

This is not a trivial problem. In adding energy harvesting systems to a Power plant you will have to verify, that you do not cause too much additional costs or difficulties in the following areas, at least:

• maintenance: don't add too much to the cost and difficulty of preventive maintenance, cleaning etc.
• repairs: don't cause obstructions
• safety barriers: you must not breach isolation, mechanical or electrical, of any isolated parts 
• operator ergonomics and safety: nothing may interfere with safe operation, cause noise or pollution and preferably no additional operations should be required
• operator handling: instructions and procedures must not become more complicated

Batteries are energy storage and intrinsically potentially dangerous. Special hazards include possible gas production, overheating, fire, explosion, and they also add to maintenance costs. Their placement requires careful consideration.

If the system requires monitoring or control, it adds to the over all system complexity, causing renewed education, training and perhaps certification efforts to be necessary.

If any of these are a problem, connecting the batteries to a charger from the grid will instantly be cheaper, quicker and less dangerous.

Thanks for your detailed explanation Mr. Dahlberg.

I understand that, application of energy harvesting for powering critical systems is trade off between safety and availability. Local energy harvesting power supplies near to control system can avoid the risk of cable cut which may happen in case of remote power supply/batter banks. But the safety issues related to battery need to be considered.

I would like to know any such systems are being used in industries.

Thank you.

Article Energy Harvesting for Self-Powered Wearable Devices