What is Re-Gen on 2MW generators?

[mikeames]

I am familiar with the concept of re-gen since I have built electric vehicles with used fork lift motors. I understand taking mechanical energy and recovering it instead of wasting it. How does the term apply to back up power and generators used in a healthcare facility such as a hospital? A healthcare facility installing 2 - 2 MW generators all part of a regen system?

 

[kwired]

To me regen means capturing energy that was otherwise going to be wasted. Not sure what might be in hospital other than heat given up from HVAC during cooling mode that might be very significant regen source of any kind, such energy in that situation more typically used for water heating than for electrical energy generation.

 

[mikeames]

To me regen means capturing energy that was otherwise going to be wasted. Not sure what might be in hospital other than heat given up from HVAC during cooling mode that might be very significant regen source of any kind, such energy in that situation more typically used for water heating than for electrical energy generation.

That may be part of it, because the person who I was talking to didn't fully understand but mentioned heat. So I was confused because the conversation was about 2MW back generators and then regen cam into the conversation.

 

[zbang]

They may be thinking of co-gen (using otherwise wasted energy), not re-gen (capturing energy back from a process and reusing it).
Co-gen is more of what kwired described or capturing exhaust heat from a process to do something else.
Re-gen is usually along the lines of taking energy from a motor to slow it down and stuffing that back into the power grid.

The line between is kind of blurry.

 

[kwired]

They may be thinking of co-gen (using otherwise wasted energy), not re-gen (capturing energy back from a process and reusing it).
Co-gen is more of what kwired described or capturing exhaust heat from a process to do something else.
Re-gen is usually along the lines of taking energy from a motor to slow it down and stuffing that back into the power grid.

The line between is kind of blurry.

both are taking energy that was otherwise going to be wasted energy.

Re-gen is more commonly use term with the motor situation like you described though, and is more of a direct using of using something moving to create electrical energy where other items are simply collecting heat and finding some use for it. If the motor isn't "regenerating" the energy in question still gets lost as heat eventually.

 

[mikeames]

He may have meant co-gen and said to me re-gen which is why I thought I better educate myself. Thanks for the confirm.

 

[kwired]

Co-gen can simply be on site generation that feeds energy not used by the site into the utility. May not use that term a lot with solar or wind but essentially that is how those often are set up.

 

[K8MHZ]

From my humble experience by example:

Co-gen = using heat which would be otherwise wasted from a land based jet turbine to spin a steam turbine generator. https://en.wikipedia.org/wiki/Heat_recovery_steam_generator

Re-gen = using a load to slow down an electric motor in order to save on brakes. Such is used in diesel locomotives. The heat generated is just wasted, but it's still cheaper than brakes.

 

[kwired]

From my humble experience by example:

Co-gen = using heat which would be otherwise wasted from a land based jet turbine to spin a steam turbine generator. https://en.wikipedia.org/wiki/Heat_recovery_steam_generator

Re-gen = using a load to slow down an electric motor in order to save on brakes. Such is used in diesel locomotives. The heat generated is just wasted, but it's still cheaper than brakes.

With VFD's most the time regen braking is dumping that energy into heat via the braking resistor, but some can either put it back into grid or tie to a common DC bus so that energy can be used by other motors on other drives, AFAIK, never seen or done this myself other than the braking resistor.

 

[zbang]

Dumping heat into a braking resistor is usually called dynamic braking, not regenerative breaking. At least IME.

Restating with possibly better words-
co-generation - capture otherwise wasted energy (usually heat) from one system as input to a separate system (e.g. turbine exhaust steam then used as process or building heat)

re-generation - extract real energy from one system as input to a separate consuming system or into storage (e.g. slowing a train and pushing the energy back into the overhead wire for other trains)

(dynamic braking) - extract real energy from one system and waste it (e.g. motor becomes a generator, energy goes into resistors and is dumped)

Of course, it'll vary in different areas and industries.

 

[mbrooke]

A generator generates a heck of a lot more heat than power. It makes sense to re-claim that heat on anything other than low run time applications ie standby.

 

[kwired]

A generator generates a heck of a lot more heat than power. It makes sense to re-claim that heat on anything other than low run time applications ie standby.

Prime mover of a small portable unit probably does. You will have a hard time making me believe a 1MW generator gives off more than 1 MW of heat just because it is running. Might produce more heat than some think it might though.

 

[Todd0x1]

Probably not applicable to your situation, but in the context of modern diesel engines the term regen is used to describe diesel particulate filter regeneration.

 

[mbrooke]

Prime mover of a small portable unit probably does. You will have a hard time making me believe a 1MW generator gives off more than 1 MW of heat just because it is running. Might produce more heat than some think it might though.

Count the exhaust heat and you're exceeding the output kw.

 

[kwired]

Count the exhaust heat and you're exceeding the output kw.

That would be exhaust from prime mover.

A wind or hydro driven unit won't have that kind of inefficiency in prime mover.

Guessing a steam boiler driving a turbine loses a lot of heat but not like an internal combustion engine does.

 

[mbrooke]

That would be exhaust from prime mover.

A wind or hydro driven unit won't have that kind of inefficiency in prime mover.

Guessing a steam boiler driving a turbine loses a lot of heat but not like an internal combustion engine does.

I'm think nat gas diesel units.

 

[Dzboyce]

The old rule of thumb for diesel generators was 1/3 of the fuel’s BTU’s got converted to mechanical energy, 1/3 was wasted as heat cooling the engine. And 1/3 was wasted in the exhaust heat. Now if the coolant heat and part of the exhaust heat can be reclaimed and used, the efficiency goes way up.