Removing a vast amount of energy
- Thread starter RustyH
- Start date
Energy cannot be destroyed, only transferred into a different form. To get rid of the electrical power, you would have to use it to power something, such as the very high power resistors.
I've done test equipment which had 'load banks' that were rated at 4kW, but that was a 'calibrated' load.
That needed a pile of quality resistors and cables like sausages... and, as you say, a massive heat exchanger and onwards....
You could use bar heaters etc. as long as you don't need a 'calibrated' load on to the source AND choose the overall resistance to suit the volts.
Don't just slap a domestic bar heater on and assume that (.e.g) 1kW is going up.
If you want to lose a real precise 50kW definite then a bit more thought has to go in to this.
If you want to get rid of roughly (or up to) 50kW somehow then you can be more rough & ready.
Your design will depend on voltages etc.
And as you will know that and Ohm's Law then you can calculate surely?
But it will definitely make a few cups of tea.
That needed a pile of quality resistors and cables like sausages... and, as you say, a massive heat exchanger and onwards....
You could use bar heaters etc. as long as you don't need a 'calibrated' load on to the source AND choose the overall resistance to suit the volts.
Don't just slap a domestic bar heater on and assume that (.e.g) 1kW is going up.
If you want to lose a real precise 50kW definite then a bit more thought has to go in to this.
If you want to get rid of roughly (or up to) 50kW somehow then you can be more rough & ready.
Your design will depend on voltages etc.
And as you will know that and Ohm's Law then you can calculate surely?
But it will definitely make a few cups of tea.
Jeremy Harris
Senior Member
We used to have to do this regularly when testing engines after rebuild. The engine dyno, when running flat out testing a CV12 engine (around 1000hp, or 746 kW) dumped the electrical energy from the brake generators into a cooling tower, where water was poured down over big heating elements and turned to steam. No big deal, the cooling tower was maybe 10ft square and the same height. Engine tests used to take maybe a few hours or so, IIRC, but I'm pretty sure the system could have run for a few days if need be.
stevesmythe
Senior Member
Offer free charging points for electric cars.
RustyH: Terminology- Energy/Work (Joules) = Power (Watts) x time (seconds or hours). 1kW.h = 3.6MJ of course - a car fuel tank holds ~1GJ of energy. Perhaps hence 50kW.h was meant? Although this may seem a lot it's modest for commercial applications. I'd guess a standby UPS system is "tested" every weekend?
If that's the case then heating elements in a large tank of water are classic.Air heating best suits smaller dumps. Back in the old power hungry computer days I recall a large commercial system here in Wellington that'd regularly dump their UPS into a huge concrete water tank, with couds of steam arising on cold days. You'd see birds warming themselves in winter!
Thermal Physics (with energy in Joules,water mass in kg,specific heat c=4185 & Celsius temp rise) allows Q = m.c.T to readily show water volumes & likely temperature rises. Naturally electrical safety may well be an issue with higher voltages however.
If that's the case then heating elements in a large tank of water are classic.Air heating best suits smaller dumps. Back in the old power hungry computer days I recall a large commercial system here in Wellington that'd regularly dump their UPS into a huge concrete water tank, with couds of steam arising on cold days. You'd see birds warming themselves in winter!
Thermal Physics (with energy in Joules,water mass in kg,specific heat c=4185 & Celsius temp rise) allows Q = m.c.T to readily show water volumes & likely temperature rises. Naturally electrical safety may well be an issue with higher voltages however.
westaust55
Moderator
@Rusty,
Can you advise the source of the 50 kW spare capacity, the voltage involved, whether single or three phase a.c. or if D.C. and the reason for wanting to dissipate that much energy rather than putting it to good use.
Can you advise the source of the 50 kW spare capacity, the voltage involved, whether single or three phase a.c. or if D.C. and the reason for wanting to dissipate that much energy rather than putting it to good use.
BeanieBots
Moderator
It does seem a shame to waste it. 50kWh is very close to my houshold power requirement for a whole week!
I do a lot of battery cycle tests and use the discharge current to charge up previously tested units.
A hybrid-bus company I did some work for had a neat solution. It was a set of domestic power showers (8kW each) set up to spray into a bath. The shower pumps then re-circulated the 'bath' water and the shower spray helped to disperse the energy. 5 units was enough to discharge a complete battery pack without overheating. Very neat simple and cheap with all the safety features already built in.
I do a lot of battery cycle tests and use the discharge current to charge up previously tested units.
A hybrid-bus company I did some work for had a neat solution. It was a set of domestic power showers (8kW each) set up to spray into a bath. The shower pumps then re-circulated the 'bath' water and the shower spray helped to disperse the energy. 5 units was enough to discharge a complete battery pack without overheating. Very neat simple and cheap with all the safety features already built in.
Those I know who have had a similar problem, have found that buying up used portable electric heaters and using them to heat a warehouse building in winter works very well, and cheaply. In summertime, they had to put them under an outdoor overhang with an industrial size fan blowing the heat away from the building.
noelnelson
New Member
A bunch of mains power electric heaters is no use to discharge a lot of power if the source voltage is low (12V, 24V 50V...)
If thats what you have, get a DC/AC inverter (or 2) of suitable power rating, to drive the heater(s). Cheap modified sinewave ones would be ideal, and by their lower conversion efficiency, inherently consume more power
One drawback of large loads at low voltage, is high currents and corresponding large cable size needed. Beware of burning out cables and causing a fire.
Another suggestion is to get some second hand hot water cylinders, heat lots of water and set up a free shower booth for the neighborhood! Or maybe a heated pool.
If thats what you have, get a DC/AC inverter (or 2) of suitable power rating, to drive the heater(s). Cheap modified sinewave ones would be ideal, and by their lower conversion efficiency, inherently consume more power
One drawback of large loads at low voltage, is high currents and corresponding large cable size needed. Beware of burning out cables and causing a fire.
Another suggestion is to get some second hand hot water cylinders, heat lots of water and set up a free shower booth for the neighborhood! Or maybe a heated pool.