NG, Propane, gas or diesel generator??
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ampsucker
Platinum Member
if you're still looking at large generators, consider this info which might effectively rule out propane as a long term source of fuel for continuous runs.
a 50kW generator is going to be in the 100 hp range. a 100 hp engine running at 50% load is consuming 500,000 btu per hour. at 20 degrees F, a 500 gallon tank 25% full can barely vaporize 500,000 btu per hour. that means, you will need a minimum of 2 each 500 gallon tanks to run at full capacity, and you'll still start to get freeze up when the tanks are near full and near empty (max vaporization occurs when the liquid and vapor volumes of the tank are roughly equal or the tanks are half full).
sooooo..... you'll most likely need at least two 1000 gallon LP tanks to get the surface area to vaporize the gas you need to run a 50kw generator at near max load and still run the tanks from all the way full to all the way empty. closer to zero degrees and you'll need to almost double the size again.
at about 9 million btus per 100 gallons, that will give you a run time of 18 hours or so per 100 gallons. that means about 15 days of continuous running with 2000 gallons. that's actually not too bad if you can use all the gas out of the tanks without freezing it up.
just something to consider while you're looking around. also, don't rule out freezing up your NG meter if you try to draw that much low pressure gas off it while running all your other gas furnaces and heaters. you'll want to consult your gas utility about the meter capacity rating in cold weather.
man, i would hate to have your utility bills!
amp
a 50kW generator is going to be in the 100 hp range. a 100 hp engine running at 50% load is consuming 500,000 btu per hour. at 20 degrees F, a 500 gallon tank 25% full can barely vaporize 500,000 btu per hour. that means, you will need a minimum of 2 each 500 gallon tanks to run at full capacity, and you'll still start to get freeze up when the tanks are near full and near empty (max vaporization occurs when the liquid and vapor volumes of the tank are roughly equal or the tanks are half full).
sooooo..... you'll most likely need at least two 1000 gallon LP tanks to get the surface area to vaporize the gas you need to run a 50kw generator at near max load and still run the tanks from all the way full to all the way empty. closer to zero degrees and you'll need to almost double the size again.
at about 9 million btus per 100 gallons, that will give you a run time of 18 hours or so per 100 gallons. that means about 15 days of continuous running with 2000 gallons. that's actually not too bad if you can use all the gas out of the tanks without freezing it up.
just something to consider while you're looking around. also, don't rule out freezing up your NG meter if you try to draw that much low pressure gas off it while running all your other gas furnaces and heaters. you'll want to consult your gas utility about the meter capacity rating in cold weather.
man, i would hate to have your utility bills!
amp
Read this whole thread, lots of good info. I have a few thoughts to add.
If the generators run best a half load why not use 2 generators
Maybe get diesel for the a/c since they only run in warm weather and ng and or propane for the rest. Size them so either would run everything critical.
I believe the load has to be balanced as I read elsewhere small generators with 240 volt output need to have both winding loaded or they will not operate correctly.
Also if money is not a concern why not go for a solar,wind,generator system cost is high but it will pay for itself.
If the generators run best a half load why not use 2 generators
Maybe get diesel for the a/c since they only run in warm weather and ng and or propane for the rest. Size them so either would run everything critical.
I believe the load has to be balanced as I read elsewhere small generators with 240 volt output need to have both winding loaded or they will not operate correctly.
Also if money is not a concern why not go for a solar,wind,generator system cost is high but it will pay for itself.
SpringHollow
Elite Member
Two small generators of the same quality are more expensive than one large one. Also, some large loads will not be able to start off of the small generator (large air conditioner, for example). For almost every generator we sell, the starting load of the largest items dictates the necessary size. Two generators does give you some redundancy though if one fails.
Ken
Ken
groundcover
Veteran Member
Lots of good info here,lots of ways to go. I have run big PTO gennys,35 & 100KW Not automatic but not a bad answer if you keep some fuel handy and your tractors in good shape. Just went through a ten day outage after an ice storm and saw a few things. Even the 'homeowner'standby gennys were getting tired,they do like to have their oil checked! We ran a 35KW Cat-Perkins Diesel,built in skid tank(good for a week) purred just like a Cat should. Also ran a 60KW LP ,V10 Ford motor,also hummed right along,used a quart of oil every couple of days but it runs pretty hard and uses 5W30 oil. She went through 600Gal of LP in ten days. I burried 2 1000gal tanks ,one for heat and one for generator but tied them together so I could switch over in an extended outage if needed. Still had 20% in generator tank at end and didn't need to switch over. Underground will help with the cold weather problems as well.
Many people didn't size LP tanks for an extended outage and were getting a little panicky. We had a LP truck on call to help them out but with road issues from trees and wires down and the ice and snow it was a real problem.Those with portable gas jobs also had issues as in gas lines at the only station that had backup power had lines like in the 70s. The big gen sets are not only pricey up front but the upkeep can be high as well. Mine run a block heater year round so they are ready to go to full power right from start up,The Cat man says they will use more power than they ever make!
Redundancy is a real good idea as well. I watch over a couple that has a nice 35KW liquid cooled Generac. Had an issue with it before the storm and thought the repair guy fixed it. Ice storm came and no power! I found it doing the same thing as before,start then tried to start again even though it was running then shut down. I pulled the power lead off the starter but the ohm meter would peg and the unit would shut down anyway. I was able to get my small 6KW diesel up there the second day and at least get them some heat and light. On Sunday after calling all the local guys to no avil found a company in Vermont and paged the help number. Guy called back and said I needed a voltage regulator,not the control board like I though. He left one on the back door and I had a woman go pick it up,Four hours later I had the part and was soon back together,Not bad for a Sunday in an ice storm!
Many people didn't size LP tanks for an extended outage and were getting a little panicky. We had a LP truck on call to help them out but with road issues from trees and wires down and the ice and snow it was a real problem.Those with portable gas jobs also had issues as in gas lines at the only station that had backup power had lines like in the 70s. The big gen sets are not only pricey up front but the upkeep can be high as well. Mine run a block heater year round so they are ready to go to full power right from start up,The Cat man says they will use more power than they ever make!
Redundancy is a real good idea as well. I watch over a couple that has a nice 35KW liquid cooled Generac. Had an issue with it before the storm and thought the repair guy fixed it. Ice storm came and no power! I found it doing the same thing as before,start then tried to start again even though it was running then shut down. I pulled the power lead off the starter but the ohm meter would peg and the unit would shut down anyway. I was able to get my small 6KW diesel up there the second day and at least get them some heat and light. On Sunday after calling all the local guys to no avil found a company in Vermont and paged the help number. Guy called back and said I needed a voltage regulator,not the control board like I though. He left one on the back door and I had a woman go pick it up,Four hours later I had the part and was soon back together,Not bad for a Sunday in an ice storm!
Good advice! I never considered that NG could freeze, since I just assumed with was a gas in the supply line from the street and therefore, not subject to cooling, since no going from liquid to gas.
Where would you expect NG line to freeze????? At the meter?
Bob
LBrown59
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Diesel since I'm already set up to handle the feul supply.
ampsucker
Platinum Member
bob, i'm not 100% sure that "freeze up" can occur under normal operating conditions. the term "freeze" is actually a misnomer in both propane and natural gas situations. what we are actually interested in is the boiling point or point at which the gas can achieve a state change from liquid to vapor.
for natural gas (primarily methane) this is -260 degrees F as opposed to propane which is -44 degrees F. in either case, it doesn't actually freeze at that temperature, it condenses into a liquid. in a propane tank, this occurs gradually as the gas loses energy to the phase change until it is so cool it can no longer create pressure and the flow of gas stops. this is cold enough to freeze any water vapor collected on the outside of the tank so people call the tank "frozen up" but the liquid propane inside the tank really just stopped boiling to produce vapor. in other words, it couldn't absorb enough heat from it's surroundings (the air outside the tank) to continue boiling so it just stopped like a tea kettle taken off the burner.
obviously, the freezing point for NG is much, much lower, so there really isn't any chance it can liquify at the pressures we are talking about. but, any contamination of water vapor inside the gas line could freeze up the diaphragm in the expansion valve and cause problems.
around here, street pressure upstream of the NG meter is about 35 psi. after the meter it is between 1/4 and 1/2 psi - definitely a sudden pressure drop or volume expansion. i would imagine the design of the meter and purity of the gas supply in your area would determine if any kind of moisture could actually solidify in the valve or orifice.
the design of the meter may take this in account? i mean it may simply not allow enough gas to pass that it could cause a severe drop in temperature at the orifice. i'm far from an expert in this area. i do know the meter should have a number on it that identifies the max amount of btus/hour it can handle. it usually starts with an A like A225 can handle 225K btus. around here, that is a common residential size. doesn't take much to max out a small meter like that if you have many gas appliances (heater, dryer, several smaller heaters in garage/barn, range, hot water, etc....).
a generator engine can get pretty thirsty, so you definitely need a good design on the supply piping and a properly sized meter to keep it fed.
amp
for natural gas (primarily methane) this is -260 degrees F as opposed to propane which is -44 degrees F. in either case, it doesn't actually freeze at that temperature, it condenses into a liquid. in a propane tank, this occurs gradually as the gas loses energy to the phase change until it is so cool it can no longer create pressure and the flow of gas stops. this is cold enough to freeze any water vapor collected on the outside of the tank so people call the tank "frozen up" but the liquid propane inside the tank really just stopped boiling to produce vapor. in other words, it couldn't absorb enough heat from it's surroundings (the air outside the tank) to continue boiling so it just stopped like a tea kettle taken off the burner.
obviously, the freezing point for NG is much, much lower, so there really isn't any chance it can liquify at the pressures we are talking about. but, any contamination of water vapor inside the gas line could freeze up the diaphragm in the expansion valve and cause problems.
around here, street pressure upstream of the NG meter is about 35 psi. after the meter it is between 1/4 and 1/2 psi - definitely a sudden pressure drop or volume expansion. i would imagine the design of the meter and purity of the gas supply in your area would determine if any kind of moisture could actually solidify in the valve or orifice.
the design of the meter may take this in account? i mean it may simply not allow enough gas to pass that it could cause a severe drop in temperature at the orifice. i'm far from an expert in this area. i do know the meter should have a number on it that identifies the max amount of btus/hour it can handle. it usually starts with an A like A225 can handle 225K btus. around here, that is a common residential size. doesn't take much to max out a small meter like that if you have many gas appliances (heater, dryer, several smaller heaters in garage/barn, range, hot water, etc....).
a generator engine can get pretty thirsty, so you definitely need a good design on the supply piping and a properly sized meter to keep it fed.
amp
SnowRidge
Elite Member
I haven't read the entire thread, so this may have already been mentioned. In the event of a really bad natural disaster or political instability, natural gas may not be available. NG pipelines may be shut down for safety reasons, or because there is no power for the pumping stations. If you have to depend upon an off site fuel source, you have lost your independence.
I vote diesel. It stores well. It can be transported without special equipment. It isn't particularly hazardous, and in a pinch most diesels can run on home made or scrounged fuels. You can't say the same for any of the other candidates.
I vote diesel. It stores well. It can be transported without special equipment. It isn't particularly hazardous, and in a pinch most diesels can run on home made or scrounged fuels. You can't say the same for any of the other candidates.
srjones
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Oh, I have a huge NG supply here with all the tankless water heaters, furnaces and 400,000 btu pool heater. My gas meter is the size of a small lawn mower.
Still, I'm obviously confused. My "little" Honda generator has something like a 20 or 22 hp gas engine and is rated at 10,000 continuous output. But, it doesn't have enough to run any A/C units. Since I don't plan on living on generator power, I am getting more interested in looking into some low hour used units. Maybe there would be something like that in a PTO configuration somewhere?
I thought of you and this thread when I heard that NG service was out in parts of KY. I also noticed that you haven't posted anything in about a week, so I can only assume that you're power went out
Were you affected? Did you get a generator solution in time? Even if you're writing in from a Red Cross warming station, let us know.