Generator with air conditioning compressor

[Delmar]

Living in the deep south the majority our electric bill is air conditioning (HVAC). Buying solar panels, battery storage and AC inverter large enough to run the HVAC is not cost effective. Natural gas is cheap here, however running an engine generator large enough to power the HVAC has both generating and motor losses so is not cost effective to operate.

My latest grand scheme is to create an engine-driven small generator also belt driving a compressor for the HVAC. The house thermostat cycles the engine when cooling is needed, and the generator will power the HVAC fan plus charge the inverter batteries. The remainder of the house is powered from the inverter, and low battery voltage will likewise start the generator for charging. An automotive compressor has an integral clutch to prevent operation if not required for cooling. Solar panels will minimize generator charging.

Could even expand the system into a co-gen by connecting a conventional gas water heater to the engine exhaust. The water heater will function as a large muffler.

Perfect for off-grid living. Any comments if my scheme is crazy or workable?

 

[John Frum]

I really doubt you can generate electrical energy from internal combustion cheaper than you can get it from the grid.
What do you pay for a kwh all in?

Update: Oh... you are going to have some kind of slip clutch to get over the inertia of the compressor, right?

 

[John Frum]

I found this triathlon system

 

[Delmar]

I really doubt you can generate electrical energy from internal combustion cheaper than you can get it from the grid.
What do you pay for a kwh all in?

After fees and taxes my December bill worked out to 11.6/kwh. Edit: generators are expensive to operate because they have to run full speed even with minimal loading. The inverter with solar panels would power the house when the generator is not charging.

Update: Oh... you are going to have some kind of slip clutch to get over the inertia of the compressor, right?

Automotive compressors already have a clutch.

 

[Delmar]

I found this triathlon system

Just add the generator and would be perfect.

 

[Picasso]

Truck APU units are great for tiny homes as an all in one backup. Anti idling laws have brought the price of them way down.

 

[SolarRat]

After fees and taxes my December bill worked out to 11.6/kwh.

I think you'll have a hard time saving money with that low a cost for grid. I'm in the same boat in Florida with high AC use and low 10-11 cent/kwh costs. Grid-tie would be the most cost effective way to go.

 

[Delmar]

I think you'll have a hard time saving money with that low a cost for grid. I'm in the same boat in Florida with high AC use and low 10-11 cent/kwh costs. Grid-tie would be the most cost effective way to go.

December bill was $105. My highest 2019 bill was $218 including surcharges. However I don't have the bill to confirm KWH used.

The engine would only operate when AC is needed, around 30% of the time. As stated above: generators are expensive to operate because they have to run full speed even with minimal loading. The inverter with solar panels would power the house 70% of the time when the AC is off and and generator is not charging.

And with the generator charging 30% of the time, plus handling the heavy loads, you can downsize the solar panels, battery capacity and inverter. During grid-down my 170ah golf cart with 2800kva UPSverter powers the house just fine (without HVAC).

 

[SCClockDr]

generators are expensive to operate because they have to run full speed even with minimal loading.

True for contractor direct AC output.
A substantial inverter generator or (2, 3 in parallel) would also git'r done & quietly as well. They run at an efficient low RPM till loaded.

 

[joterrence]

Living in the deep south the majority our electric bill is air conditioning (HVAC). Buying solar panels, battery storage and AC inverter large enough to run the HVAC is not cost effective. Natural gas is cheap here, however running an engine generator large enough to power the HVAC has both generating and motor losses so is not cost effective to operate.

My latest grand scheme is to create an engine-driven small generator also belt driving a compressor for the HVAC. The house thermostat cycles the engine when cooling is needed, and the generator will power the HVAC fan plus charge the inverter batteries. The remainder of the house is powered from the inverter, and low battery voltage will likewise start the generator for charging. An automotive compressor has an integral clutch to prevent operation if not require

Living in the deep south the majority our electric bill is air conditioning (HVAC). Buying solar panels, battery storage and AC inverter large enough to run the HVAC is not cost effective. Natural gas is cheap here, however running an engine generator large enough to power the HVAC has both generating and motor losses so is not cost effective to operate.

My latest grand scheme is to create an engine-driven small generator also belt driving a compressor for the HVAC. The house thermostat cycles the engine when cooling is needed, and the generator will power the HVAC fan plus charge the inverter batteries. The remainder of the house is powered from the inverter, and low battery voltage will likewise start the generator for charging. An automotive compressor has an integral clutch to prevent operation if not required for cooling. Solar panels will minimize generator charging.

Could even expand the system into a co-gen by connecting a conventional gas water heater to the engine exhaust. The water heater will function as a large muffler.

Perfect for off-grid living. Any comments if my scheme is crazy or workable?

d for cooling. Solar panels will minimize generator charging.

Could even expand the system into a co-gen by connecting a conventional gas water heater to the engine exhaust. The water heater will function as a large muffler.

Perfect for off-grid living. Any comments if my scheme is crazy or workable?

We can include this in our R&D

Living in the deep south the majority our electric bill is air conditioning (HVAC). Buying solar panels, battery storage and AC inverter large enough to run the HVAC is not cost effective. Natural gas is cheap here, however running an engine generator large enough to power the HVAC has both generating and motor losses so is not cost effective to operate.

My latest grand scheme is to create an engine-driven small generator also belt driving a compressor for the HVAC. The house thermostat cycles the engine when cooling is needed, and the generator will power the HVAC fan plus charge the inverter batteries. The remainder of the house is powered from the inverter, and low battery voltage will likewise start the generator for charging. An automotive compressor has an integral clutch to prevent operation if not required for cooling. Solar panels will minimize generator charging.

Could even expand the system into a co-gen by connecting a conventional gas water heater to the engine exhaust. The water heater will function as a large muffler.

Perfect for off-grid living. Any comments if my scheme is crazy or workable?
[/QUOTE

 

[JanLewisfD]

Living in the deep south the majority our electric bill is air conditioning (HVAC). Buying solar panels, battery storage and AC inverter large enough to run the HVAC is not cost effective. Natural gas is cheap here, however running an engine generator large enough to power the HVAC has both generating and motor losses so is not cost effective to operate.

My latest grand scheme is to create an engine-driven small generator also belt driving a compressor for the HVAC. The house thermostat cycles the engine when cooling is needed, and the generator will power the HVAC fan plus charge the inverter batteries. The remainder of the house is powered from the inverter, and low battery voltage will likewise start the generator for charging. An automotive compressor has an integral clutch to prevent operation if not required for cooling. Solar panels will minimize generator charging.

Could even expand the system into a co-gen by connecting a conventional gas water heater to the engine exhaust. The water heater will function as a large muffler.

Perfect for off-grid living. Any comments if my scheme is crazy or workable?

My aunt had something similar. When her parents gave her an air conditioner, she started getting such fabulous bills that it's just awful. But after five months, my aunt decided that something had to be done about it, because she only paid her entire salary for electricity. And she turned to my dad for help, and they decided to look for some service together, soon they came across these guys www.socool.sg. They just established economic control, that's all. So far, she has this air conditioner works flawlessly, and most importantly does not eat a lot of electricity.

 

[theoldwizard1]

Living in the deep south the majority our electric bill is air conditioning (HVAC). Buying solar panels, battery storage and AC inverter large enough to run the HVAC is not cost effective. Natural gas is cheap here, however running an engine generator large enough to power the HVAC has both generating and motor losses so is not cost effective to operate.
.
.
.
Perfect for off-grid living. Any comments if my scheme is crazy or workable?

Not quite full blown "crazy" !

About 40 years ago I worked with a small engineering company that was trying to design a natural gas powered internal combustion engine that would drive an A/C unit for a small commercial buildings in the South (think fast food restaurant). Clearly, this thing would run 24/7/365 (or at least when ever the store was open). Using available technology (and internal combustion engine have not changed that much in 40 years) the maintenance and longevity of the engine were the really killers. Oil and filter changes were about every 1 - 2 week (pre-synthetic oil) and durability of the pistons, rings and bearings was "questionable".

 

[Delmar]

About 40 years ago I worked with a small engineering company that was trying to design a natural gas powered internal combustion engine that would drive an A/C unit for a small commercial buildings in the South (think fast food restaurant)...

About 40 years ago I worked for Waukesha Engine, specifically their Power Systems division, designing generator bases and system controls. For prime power the engines were massive and could run continually for several years. With the optional dual reservoirs they could change the oil & filters while running.

My father was a lifer there and I planned to follow his footsteps until the Jimmy Carter recession killed the market, and long later they disappeared. And now I am debating returning to the backup power industry to finish my career...

 

[Trukinbear]

I had an APU on my truck that ran an AC compressor - unless your house is 8'x10' with very low ceilings an automotive AC compressor isn't going to have enough capacity to keep you cool. Going to be like trying to cool a 2000sqft house with a 5200BTU window unit. My inverter/charger easily runs two RV roof air units, and cranks up the generator when the battery gets low - I think you'd have a better outcome with a more conventional system. In your model, the engine will run so much, much more than a generator would run to charge an appropriately sized battery. Penny wise but pound foolish.

 

[Trukinbear]

You might want to look at mini-split heat pump units - my 12,000 BTU 'Mr. Cool DIY' unit uses 400-500 watts.

 

[Delmar]

...unless your house is 8'x10' with very low ceilings an automotive AC compressor isn't going to have enough capacity to keep you cool.

I read it on the internet so it has to be true: "Most sedans have air conditioning systems that can approach 40,000 BTU (3.3 Tons) in capacity." Source
I don't doubt the value because a typical car has tremendous heat load from the glass and engine. I was planning to take the system from a large van with dual AC.

 

[gnubie]

Take a look at the size of the condenser and consider that it often has 40+ km/h of air being rammed at it when the vehicle is in motion, and when it doesn't have that sort of air flow blasting at it there is a rather hefty set of fans to pull a lot of air through it.

 

[Delmar]

Take a look at the size of the condenser and consider that it often has 40+ km/h of air being rammed at it when the vehicle is in motion, and when it doesn't have that sort of air flow blasting at it there is a rather hefty set of fans to pull a lot of air through it.

Automotive compressor, residential condenser and evaporator coils. Or potentially a water cooled automotive condenser sunk in a pond with fountain.

 

[Trukinbear]

Well do what you will. I lived with a professionally designed APU like you are trying to cobble together every day for nearly 10 years. My APU was powered by a 3 cylinder kubota diesel and was also capable of making 6kw in power. In 1990's dollars fuel, and maintenance costs were just over $3/hr, and sitting still the AC was marginal on a hot day in my 8x6 truck sleeper.

My 'Mr. Cool Diy' heat pump can run off a small Inverter and modest batteries at 400-500 watts. Run a generator for an hour to charge a battery and run your heat pump for a day.

Your automotive compressor will eat 3-4hp minimum, and maybe another 2 hp to run fans, and will likely run constantly unless your house is insulated like a walk in freezer.

I think it is an expensive way to do it, but what do I know?

 

[doppler]

Well do what you will. I lived with a professionally designed APU like you are trying to cobble together every day for nearly 10 years. My APU was powered by a 3 cylinder kubota diesel and was also capable of making 6kw in power. In 1990's dollars fuel, and maintenance costs were just over $3/hr, and sitting still the AC was marginal on a hot day in my 8x6 truck sleeper.

My 'Mr. Cool Diy' heat pump can run off a small Inverter and modest batteries at 400-500 watts. Run a generator for an hour to charge a battery and run your heat pump for a day.

Your automotive compressor will eat 3-4hp minimum, and maybe another 2 hp to run fans, and will likely run constantly unless your house is insulated like a walk in freezer.

I think it is an expensive way to do it, but what do I know?

I am running a 12,000 mini split off solar on my RV with the inverter they use they really are a game changer. People are so conditioned to saying you cant run AC off solar it will take a little while to catch up.