Residential gas unit question

[Lazerdog]

Hello.

I have a customer that wants to install a natural gas or diesel generator set in his home and run it as his prime source of electricity. He thinks this would be cheaper then buying electricity from his utility. I'm pretty sure this idea is ludicrous, but I wanted to know if anyone had any differing ideas. (p.s. he lives in Ontario Canada which has pretty high electricity prices.)

Thanks

 

[dpc]

Does he still expect the utility to serve him when he blows a head gasket?

The utility will have a minimum monthly charge even if he isn't using any energy unless he's planning on going off the grid completely. That cost could be more than he expects.

I really doubt it would pencil out when O&M costs for the engine-generator, installation cost, permits, etc are figured in. Plus he has no control over price of natural gas or diesel (which is more expensive than gasoline in the US right now).

I'm sure his neighbors will love listening to the drone of that diesel engine at night....

 

[wareagle]

Check here. It may have information you can use to compare costs.

http://www.eatonelectrical.com/NASA...c=Apubarticles&cid=1016116480106&Sec=products

 

[resqcapt19]

Is he going to use the waste heat for water and building heating? What is he going to do when there is little load...running the generator won't be very efficient at low loads. Maybe he could combine it with batteries and an inverter system for the low loads and then use the generator at peak times to power the house and charge the batteries. I would expect that the payback would be long for an installation like this.
Don

 

[BJC]

Several years ago I read of an in-home generator made by Fiat. The unit was to be marketed in place of a heater. It ran on natural gas. It was designed to be installed in a basement and supposedly quite. The exhaust stack was PVC. All the heat went into the building. The generator was small 25 or 30 KW. I don't remember if it was intended to sell power back to the utility.
I though they would be a good deal in someplace like ND where you could reclaim the jacket heat and run electric heaters.
Most natural gas heaters send a lot of heat up the stack.
I don't have time to google up everything Fiat makes now but I'l bet someone is makeing something similar.

 

[waross]

A good rule of thumb is 13 KWH per us gallon of fuel.
That would be 15.6 KWH per gallon in Canada.
That is fuel costs, add oil changes, filters, rebuilds and repairs.
He will gain a considerable advantage if he heats the house with waste heat.
Now if he has an office building and is going to use redundant generators and either heat or cool the building with waste heat, the numbers may look better, particularly if the commercial energy rate is higher than the residential rate.
It would be interesting, Lazerdog, if you can post the current residential rates.
yours

 

[itsmoked]

If he is under a tier system it can often be cheaper to "home-make" electricity than buy it at the third tier.

In that case a system that looks ahead to the end of the month and sez we are going to land with 100kwhrs in the third tier so we better transfer switch off the utility and make electricity for 2.7 hrs a day could make sense.

This is back to my water heater that produces waste electricity. He could possibly make all hot water via a generator that is put online running the house whenever heated water is required. (The heated water can also be used to heat the house).

Here is another alternative. It is a fuel cell system that is a box you sit next to your house like an air conditioning condenser unit. The system cracks Nat Gas then runs it thru a 5kW fuel cell which is used to charge a small bank of batteries. They then invert from the batteries to produce 5kW continuous power up to 10kW occasionally. The thing is nearly silent. Needs minor maintenance once a year (clean a filter?) and I think you can scavenge a bunch of heat for water heating.

It really seems like a great idea without the stink and noise a generator comes with.

http://www.fuelcellmarkets.com/article_default_view.fcm?articleid=1359&subsite=656

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[Lazerdog]

Wow thanks for the great feedback guys. I really appreciate it.

 

[stanlsimon]

Most internal combustion engines simply can't run for 8000 hours per year. Think of how little your car operates and they still wear out in ten years or less.

One scenario to overcome this would be to oversize the generator, use the excess power to charge batteries when running, and then using inverters to operate the load. This would reduce your engine running time.

In order to get economy the Engine jacket "waste" heat needs to be recovered and utilized. This can be accomplished by using a thermal storage water tank. Unfortunately, a fairly large tank is required. This can be overcome by using the building flooring slab as part of your storage system. Without phase change you only get one btu per pound of water degree F. This mean that for the average house with a heat loss of 60000 btu/hr, assuming a water delta T of 180-100=80, say 4 hour coast time between engine runs, 60000x4=240000. Set that equal
to m x c x delta T, solve for m , you need 3000 pound of water plus the weight of the tank.

For the ultimate COP use a geothermal heat pump driven directly from the engine along with cogenation. For further information see the book "Thermal Environmental Engineering" by James Threlkeld.

 

[waross]

There's no free lunch. Oversizing the set will give you more time until a more expensive rebuild.
I put a prime power set in a remote location and used batteries. There was an event once or twice a month that required about 18 Kw. The set was sized for this load. the normal load was about 2.5 Kw. Batteries and invertors were used. Bad bad bad. The lead acid battery replacement ran over a thousand dollars a year. It would have been much cheaper to add a second 5 Kw set and ditch the batteries.
After the budget was blown, and with the anual cost of battery replacement, the battery bank became smaller and smaller. I understand that the bateries are not much used anymore. There are not enough left to be effective. A 5 Kw generator will be much cheaper than replacing the batteries, but there is no money available for either option.
The rule of thumb for continous running sets is a minor overhaul at 15,000 hours. A major rebuild at 30,000 hours.
The newer, computer controlled sets use a computer algorith to indicate rebuils intervals. That is 15,000 hours for a fully loaded set. For a partly loaded set, the computer calculates and reports an extended time between rebuilds.
Consider a silica gel adsorbtion unit to supply 39 deg. F water for air conditioning. This runs on the waste heat from the engine cooling system. The cost is about $2000 per ton for the skid. Installation and room cooling units extra.
In cool/cold weather use tyhe waste heat for heating. The first choice for waste heat is the water jacket. If you need more BTUs you can add a heat exchanger on the exhaust.
yours