subaruplatt Posted February 4, 2008 Share Posted February 4, 2008 Long rant... For years I drove around truck based portable electrical generators. The largest was one wicked detroit based 2000 amp super cooled unit. I also worked a synchronized multi unit that could do more. I still remember the lovely run up the immensely high quality volvo marine diesels required when they started. But alas... I always wondered why it was that a bigger diesel in the front of the rig always drove the rear electrical generator around? Why not have one generator to do both? So in my mind I kind of pictured a large pickup type thing with generator and motive propulsion from the same unit. Mid engined so to speak. Considered electrical drive. Wet Sump. etc I always pictured a boxer engine to keep the center of gravity lower. Believe me things like this sink like a stone and are no good off-road, which is what I was constantly asked and refused to do that in the dodge based pickup/base geny. It looked like it could do much more than it could. The new 2.0 liter puts out it's maximum torque at 1800 rpm. This would make it almost custom tailored for electrical power generation in north america. So a light bulb went on for me! Who Knows what this thing might be like when mated to an alternator? Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 4, 2008 Share Posted February 4, 2008 Hi. Yes not sure. It must have to do with economics. Like truck + generator as two separate efficient items means a profitable product. The custom truck you mention with a hydrid drive would cost wayyyy more than the two separately mated together. Plus it would not be as efficient, i.e. diesel -> drivetrain diesel -> generator -> electric motor -> drivetrain is not as efficient. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 4, 2008 Share Posted February 4, 2008 What kind of power output were you looking for? It takes a LOT of power to generate large amounts of electricity. I wouldn't see that tiny little Subaru engine being able to power more than about 150 Kw. Although that's a decent sized generator. Some of the smaller trailer mounted gens I work on use Isuzu 4 cylinder diesel's. But anything over 200 Kw is going to need more power - 6 cylinder or larger. We have a 1,000 Kw at work that's running a 650 HP Mitsubishi Twin Turbo V10 for example.... Also - the tendancy is toward trailer mounted generators now. Truck mounted units are not at all popular. Trailers can have a lower center of gravity, and a larger set tank. And you can run cable quite a long distance with the load bank/cable reel trailers we use. Of course smaller units can be truck mounted, but those are generally the 25 Kw and smaller portable units. GD Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 4, 2008 Share Posted February 4, 2008 Harbor freight sells small generators powered by SUBARU engines Yes also typically engine must be a bit overside for the generator. Otherwise it cannot react very quickly to a sudden change in load. A good generator maybe has ~97% efficiency? But that would be on a larger scale, like the big ones you guys are talking about? Larger units will also possibly be synchronous generator setups, which can also help match power factor of the load. However such generator rental is becoming more popular in areas with rolling outages during peak demand times since co's consuming lots 'o power can get a much better rate on interruptible power. Also now in many areas power co's are not allowed to interrupt residential power until all power contracts using interruptible power have been excercised. i.e. maybe your contact with power co is for 30 minute interruptible power, which means power co can call you at any time and say in 30 minutes you have to drop all your load, except maybe some negligible office/lighting power. Then you have agreement with a generator rental co who comes out and ties in their generator to your switchgear/motor control and you are back online! Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 4, 2008 Share Posted February 4, 2008 Yes also typically engine must be a bit overside for the generator. Otherwise it cannot react very quickly to a sudden change in load. A good generator maybe has ~97% efficiency? But that would be on a larger scale, like the big ones you guys are talking about? Most gens have a peak, and a continuous rating. For example, a 10 Kw generator may have a peak of 25 Kw for motor starts, etc. It's common on the smaller generators to see stuff like that. On the larger generators they don't rate them quite the same - you generally want to load them up around 80% or higher load to keep the engine's from running too cold (diesel's do not like that), but on larger unit's this is done with compensating load banks that burn off the extra power as heat when the unit is not being loaded sufficiently. This has the added benefit that you can heat a small warehouse with the load bank - which is essentially a big resistance heater coil. Also on larger units, the tendency is headed toward more sophisticated equipment loads. Most of our larger compressors are running VFD (variable frequency drive) motors that don't require huge loads to start and stop. They can idle up slowly, and idle back when not in use. Thus they also have an unlimited start cycle. Power companies are bracketing folks by using "peak load" conditions so that if you start a non-VFD compressor just once each day your rates will skyrocket because of the Amp spike caused by the start - even though you haven't used any more electricity. You jump into the next "service bracket" because of the peak demand, so your Kw/H price increases compared to lower bracketed customers. Larger units will also possibly be synchronous generator setups, which can also help match power factor of the load. However such generator rental is becoming more popular in areas with rolling outages during peak demand times since co's consuming lots 'o power can get a much better rate on interruptible power. Also now in many areas power co's are not allowed to interrupt residential power until all power contracts using interruptible power have been excercised. i.e. maybe your contact with power co is for 30 minute interruptible power, which means power co can call you at any time and say in 30 minutes you have to drop all your load, except maybe some negligible office/lighting power. Then you have agreement with a generator rental co who comes out and ties in their generator to your switchgear/motor control and you are back online! We rent a LOT of generators - lots of cell tower backup is done with rentals as the locations are often remote and it would be cost-prohibitive for them to buy generators for every tower. Also difficult to secure them at some of the more remote site's. GD Quote Link to comment Share on other sites More sharing options...
subaruplatt Posted February 4, 2008 Author Share Posted February 4, 2008 Hi. Yes not sure. It must have to do with economics. Like truck + generator as two separate efficient items means a profitable product. The custom truck you mention with a hydrid drive would cost wayyyy more than the two separately mated together. Plus it would not be as efficient, i.e. diesel -> drivetrain diesel -> generator -> electric motor -> drivetrain is not as efficient. Yes to economics, but still one more piece in the puzzle, and l dreamt off long before I ever thought of subaru. Quote Link to comment Share on other sites More sharing options...
subaruplatt Posted February 4, 2008 Author Share Posted February 4, 2008 What kind of power output were you looking for? It takes a LOT of power to generate large amounts of electricity. I wouldn't see that tiny little Subaru engine being able to power more than about 150 Kw. Although that's a decent sized generator. Some of the smaller trailer mounted gens I work on use Isuzu 4 cylinder diesel's. But anything over 200 Kw is going to need more power - 6 cylinder or larger. We have a 1,000 Kw at work that's running a 650 HP Mitsubishi Twin Turbo V10 for example.... Also - the tendancy is toward trailer mounted generators now. Truck mounted units are not at all popular. Trailers can have a lower center of gravity, and a larger set tank. And you can run cable quite a long distance with the load bank/cable reel trailers we use. Of course smaller units can be truck mounted, but those are generally the 25 Kw and smaller portable units. GD 150kw - loss from 150kw. Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 4, 2008 Share Posted February 4, 2008 hehe yah I 'd say we move on and build a prototype of the proposed unit! wohoo. Maybe we can parallel ten of the new soob 3.6L's to get us started. Yes for the peak power loading I remember ten years ago on co-op standing next to a 39000 hp air compressor firing up, they had to call the power co for permission to start it first, and said it was ~$1000 just to start it. Quote Link to comment Share on other sites More sharing options...
subaruplatt Posted February 4, 2008 Author Share Posted February 4, 2008 Most gens have a peak, and a continuous rating. For example, a 10 Kw generator may have a peak of 25 Kw for motor starts, etc. It's common on the smaller generators to see stuff like that. On the larger generators they don't rate them quite the same - you generally want to load them up around 80% or higher load to keep the engine's from running too cold (diesel's do not like that), but on larger unit's this is done with compensating load banks that burn off the extra power as heat when the unit is not being loaded sufficiently. This has the added benefit that you can heat a small warehouse with the load bank - which is essentially a big resistance heater coil. Also on larger units, the tendency is headed toward more sophisticated equipment loads. Most of our larger compressors are running VFD (variable frequency drive) motors that don't require huge loads to start and stop. They can idle up slowly, and idle back when not in use. Thus they also have an unlimited start cycle. Power companies are bracketing folks by using "peak load" conditions so that if you start a non-VFD compressor just once each day your rates will skyrocket because of the Amp spike caused by the start - even though you haven't used any more electricity. You jump into the next "service bracket" because of the peak demand, so your Kw/H price increases compared to lower bracketed customers. We rent a LOT of generators - lots of cell tower backup is done with rentals as the locations are often remote and it would be cost-prohibitive for them to buy generators for every tower. Also difficult to secure them at some of the more remote site's. GD VFD drives don't work in lighting Frame flicker rate must be constant , or sound revving engines make higher and more intense variable noises that by nature cannot easily be blocked . The one I'm talking about is creating 2000 amps constant across al three phases @ 1800 rpm. Rain or Shine Believe me it's allot to see. Redundant runs of 4ø might get allow you 375 X 2 (per leg). So you need 10 4ø cables to legally get that much power to the ground That is allot of juice for a 5 ton geny to lay down. 150 kWh subaru engine could lay down 1250/3 amps continuous @ 120 volts. More a than five single 4ø run could legally feed. In lighting terms that would be 15 ten-Ks, 12.5 12-Ks, 8.3 18Ks, 7.5 20Ks etc. So even if in reality it is only 12, 10, 6, 5, in number it would be still good. Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted February 4, 2008 Share Posted February 4, 2008 Wow that's a lot of juice! what are you running like 2/750 kcmil/phase...hm can you get flexible cable that big Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 4, 2008 Share Posted February 4, 2008 2000 amps at what voltage? 110 for lighting/sound? That's only about a 250 Kw generator. While this isn't real small, it's not terribly large either. But you couldn't run it with a Subaru motor. GD Quote Link to comment Share on other sites More sharing options...
subaruplatt Posted February 4, 2008 Author Share Posted February 4, 2008 2000 amps at what voltage? 110 for lighting/sound? That's only about a 250 Kw generator. While this isn't real small, it's not terribly large either. But you couldn't run it with a Subaru motor. GD typical portable generator 600 amps 900 amps or 1200 amps. Not 2000 amps. Quote Link to comment Share on other sites More sharing options...
subaruplatt Posted February 4, 2008 Author Share Posted February 4, 2008 Wow that's a lot of juice! what are you running like 2/750 kcmil/phase...hm can you get flexible cable that big The old awg standard halves it's resistance every 3 awg See chart http://www.interfacebus.com/Copper_Wire_AWG_SIze.html Quote Link to comment Share on other sites More sharing options...
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