The Ergosphere
Thursday, March 17, 2005


(UPDATED 2005-03-29:  See below.)
(note:  this topic was handled briefly in the appendix of "Where to go from here?")
There is one universal truth about heat engines:  none can convert 100% of its input energy into work (in the physics sense).  Some fraction of the input energy is always going to be converted to low-temperature heat which must be exhausted to the "heat sink", which is typically the environment (see Entropy Blues).  This exhaust heat is often called "waste heat".
One feature of waste heat is that it isn't always necessary to waste it.  If there is a need for heat at or below the exhaust temperature of the engine, the engine's heat exhaust may be usable as a heat source instead of burning fuel directly.  This system of generating power is called cogeneration.
Cogeneration effectively uses fuel energy two or more times:  the first time as high-grade (high-temperature, low entropy) heat as input to the engine, and the waste heat is used a second time as lower-grade (lower temperature, higher entropy) heat for other purposes.  These other purposes include industrial process heat, distillation of water or alcohol, input to absorption chillers, or space heat.
If both heat and electricity are required at the same time, cogeneration can achieve much higher overall efficiences than the separate generation of heat and electricity.  For instance, a cogenerator which takes 100 kWh of fuel to produce 30 kWh of electricity and 70 kWh of heat can eliminate 70 kWh of fuel that would otherwise be burned in a furnace to provide heat.

Very high effective efficiency

If the efficiency of cogeneration is rated in terms of additional fuel burned versus additional energy produced, it can be extremely high.  A modern home furnace may burn natural gas and capture 95% of the energy as space heat.  A gas-fired cogenerator with an electric efficiency of 30% and an overall efficiency of 90% will lose 10% of the total energy of the gas, but for each unit of electricity it uses only 1.33 additional units of gas; its effective efficiency is a whopping 75%.  If the heat losses can be reduced to the same 5% as the furnace, this figure increases to 86%!  This contrasts very favorably with centralized powerplants which may burn gas with perhaps 50% efficiency, or coal at efficiencies as low as 33%.  If fuel is being burned to produce low-temperature heat, cogeneration is a good way of getting electricity with very little extra fuel and fuel cost.
Domestic cogeneration (also called combined heat and power) is one form of distributed electric generation.  Like standard furnaces and water heaters, domestic cogenerators burn fuel and produce low-grade heat; unlike furnaces and water heaters, they turn part of their fuel into electricity.
Some attractive technologies have impediments to their adoption.  Gas turbines are inefficient in very small sizes and fuel cells remain too expensive for common use.  A building which needs ~390,000 BTU/hr of heat and can use or sell 60 kW of electricity can use a Capstone ICHP system, but this is about ten times too big for most homes.  For this and other reasons small cogenerators use internal combustion engines, either Otto (spark ignition) or Diesel cycle.

Broad applicability, no availability

Just about every home which needs winter heat and is not all-electric is a possible site for cogeneration.  Heating fuel is delivered to most homes either by pipeline or by truck.  Home-heating oil is almost identical to number 2 diesel fuel, and engines can be run quite well on either propane or natural gas.  Homes appear to be natural sites for cogeneration.
Yet for all the availability of fuel, small cogenerators are very scarce.  Perhaps this is due to a lack of true markets in electricity, where homeowners with an excess could sell as easily as they buy.  Regardless of the reason, devices which look like they ought to be common household appliances are not for sale.
In the absence of a market in small cogenerators, it is difficult to determine what they would cost in volume production.  Superficially similar systems have per-kW prices all over the map.  Examples:
These systems are not directly comparable.  Here is a table of costs and properties: 

System Size (kW) Engine cyl. Engine speed,
Fuel Emission controls 2005 $ 2005 $/kW Notes
Generac 7.55 1 3600 Gasoline None 1150 158 No cooling jacket or exhaust heat recovery.
Inadequate quieting.
Engine speed too high for long life.
Vehicle 62.8 4? 2000-3000 Gasoline Catalyst 2940 47 Presumably includes radiator and exhaust.
Vehicle 68.5 4? 2000-3000 Diesel (not stated) 5100 77 Presumably includes radiator and exhaust.
Vehicle 59.6 4? 2000-3000 CNG Catalyst 3430 58 Presumably includes radiator and exhaust.
550 (not stated) (not stated) NG Catalyst w.
ammonia NOx
639,000 1150 Presumably includes full heat recovery.
The comparisons are interesting.  The 550 kW cogenerator's price is off the chart; clearly it is a low-volume product with few economies of scale, and is not comparable to the other examples.  The one-lung engine in the Generac and vehicle powertrains are high-volume products.  Curiously, the cost of the vehicle powertrains all run roughly 3-5 times the retail price of the Generac, despite their outputs being nearly ten times as great; their cost appears to scale with cylinders rather than power.  The complexity of a 4-cylinder engine is roughly 4 times as much as a 1-cylinder engine.  Complexity and expensive components would appear to account for the extra cost of CNG over gasoline (costly tanks, high-pressure plumbing), and diesel over CNG (high-precision injectors and injector pumps).  It seems fairly safe to posit that cost is roughly proportional to cylinder (parts) count.

What do we need?

What are the properties required of a domestic cogenerator?
There are some difficulties unique to cogenerators which must be solved:

The product

What's the 2010-model, million-selling home cogenerator likely to look like?
  1. It'll come in one or more boxes, totalling about the size of a conventional furnace.
  2. It will have a one- or two-cylinder, long-stroke engine operating at a speed well under 2000 RPM, perhaps as low as 1000 RPM.  This engine will operate on something like the Atkinson cycle, for improved efficiency and lower exhaust noise.
  3. Maintenance will ordinarily be limited to annual changes of the engine air filter and an oil reservoir/filter cartridge.
  4. The engine module will have a heavy, sound-absorbing housing.  This may be a light shell filled with sand or water on-site.  There may also be active noise cancellation for the intake and exhaust.
  5. Gas- and propane-fired generators will use catalytic converters for emissions control.  Diesel generators (retrofitted for oil furnaces or where propane delivery is not available) will use catalysts to reduce gaseous emissions and filters to trap particulates.
  6. The treated exhaust will feed into a condensing heat exchanger.  The cooled exhaust will be cool enough to exit through PVC pipes, like today's condensing furnaces and high-efficiency water heaters.
  7. Engine thermal efficiency will be on the order of 35%.  Alternator and electronic losses will reduce this somewhat.  Good design will recover this energy as space heat, e.g. by using the house air to cool the electronic heat sinks.
  8. Units will probably have some stand-alone capability, so that they can provide heat and essential electricity during winter grid outages.  This would require a small starting battery, some additional sophistication in the starting and power conditioning electronics, and a resistor bank (dump load) capable of handling excess power.
This cogenerator will have perhaps two cylinders.  Its cooling system will be roughly comparable to a vehicle's radiator.  The alternator will have fewer parts, less bulk and lower operating loads than an automotive transmission.  It will not need a separate starter.  It will have electronic controls on the order of a vehicle.  The exhaust system will be more sophisticated, including not merely muffling, catalytic aftertreatment and possible filtration but heat exchange and handling of condensate.  The fuel supply is either piped in or assumed to be in place, so there are no additional expenses there.  Its cooling fan will be the house air circulation blower.
It appears that the entire cogenerator system will have roughly the same complexity as half a 4-cylinder car engine, and ought to be able to sell for roughly half the price:  $1500 for natural gas or propane, $2500 for oil-fired diesel.  This purchases a system capable of producing 5 to 10 kW continuous, plus 30,000 to 60,000 BTU/hr of heat (roughly 6000 BTU/hr/kW).

What does it get the owner?

Apparently, one hell of a lot.  The average gas-heated home in the USA uses 50 million BTU of gas per heating season; at current retail prices of $.60/therm, it costs about $300 a year.  If an owner replaces an older, 80%-efficient furnace with a cogenerator with 60% thermal efficiency and 35% electric efficiency, gas consumption rises by 1/3 to 66.7 million BTU and annual fuel cost rises by about $100.  However, the cogenerator also produces 23.4 million BTU (6840 kilowatt-hours) of electricity; at a retail price of 8 cents/kWh, this electricity is worth about $550.
The typical household uses about 1 kilowatt average; over a 180-day heating season, one would expect the house to use only about 4300 kWh of electricity.  The cogenerator would produce considerably more electricity than the household could consume, and it seems unlikely that the utility's other customers (who might have their own cogenerators) could be expected to consume it.  What else could the cogenerator's output help to displace?
Why not gasoline?  If the household has an electric or plug-in hybrid vehicle, the cogenerator could feed it during the heating season.  If the electricity was fed to a vehicle using 250 Wh/mile, the excess 2520 kWh could drive the car for 10,080 miles.  If the car would otherwise have gotten 35 miles per gallon of gasoline, that is a savings of 288 gallons worth nearly $590 at today's pump price.
The final question:  Where do you get the increased 1/3 in natural gas consumption?  Everything comes at a price, and in areas where electricity is generated by burning coal the likelihood is that some of it would come from petroleum, as fuel oil instead of gasoline.  If about 1/4 of the cogenerators switched to fuel oil, the average household would burn 16.7 million BTU of oil and 50 million BTU of gas.  At 19,110 BTU/lb this would be 847 pounds of fuel, or 114 gallons.  This displacement would not occur in areas where electricity is generated with natural gas.

Final accounting

One unresolved issue is how much fuel is displaced at the electric powerplant.  If the house draws power from a coal-fired powerplant with a heat-rate of 10200 BTU/kWh, the saved 4320 kWh would displace 44 million BTU of coal, or about 2 tons.   The savings in CO2 emissions would be 7.3 tons.  A gas-fired powerplant with a heat rate of 6800 BTU/kWh would reduce its emissions by a mere 1.69 tons.  Last, I'm going to assume that heating oil costs, and is taxed, the same as motor fuel so that there is no tax subsidy of electric vehicles via oil-burning cogenerators.  Last, for simplicity's sake, I'm going to assume that the chemical formula of both gasoline and fuel oil is CnH2n.


Δ consumption  Cost/unit Δ cost
CO2 emission
 per unit
Old emission New emission Δ emission
4320 kWh 0 -4320 kWh $0.08/kWh -$345.60 3.4 lb/kWh 7.34 tons 0 -7.34 tons
4320 kWh
-4320 kWh
0.78 lb/kWh
1.69 tons
-1.69 tons
Natural gas
500 therms 500 therms 0 $0.60/therm 0 11.52 lb/therm 2.88 tons 2.88 tons 0
Natural gas
500 therms
667 therms
+167 therms
$0.60/therm +$100
11.52 lb/therm 2.88 tons 3.84 tons
+0.96 tons
Gasoline 288 gallons 0 -288 gallons $2.00/gallon -$576.00 19.4 lb/gallon 2.79 tons 0 -2.79 tons
Fuel oil
electric only)

+114 gallons $2.00/gallon +$228.00 19.4 lb/gallon 0 1.10 tons +1.10 tons


13.01 tons
3.98 tons
-9.03 tons


7.36 tons
3.84 tons
-3.52 tons

This analysis does not include other improvements which could easily be levered in.  For instance, any building with central air already has most of the hardware required to heat with a heat pump; using a heat pump, external electricity can displace fossil fuel.  Wind power is widely available in the winter across much of the nation and could displace fuel for lighting, heating and transportation at the same time.  The potential savings in gas consumption is immense, and cogenerators could easily compensate for variations in wind intensity on a minute-by-minute basis.

Other issues and savings

The widespread use of cogeneration would improve many other things as well.
Some people have been asking if we can afford to adopt measures like cogeneration.  Unless I'm terribly wrong, it looks like we can't afford not to.
(As always, corrections cheerfully accepted.  I'll credit them to the originator.)
UPDATE 2005-03-29:  Tom DC/VA thinks that my estimate for cogenerator cost is low, by a factor of two to four.  I can't see how a mass-produced piston cogenerator in the 5-10 kW range could cost more than a 60 kW automotive powerplant; the engine itself would have about half the parts count, and the cooling system is roughly the same complexity but can be made more rugged (cheaper materials, lower warranty costs) because it does not have vehicular weight constraints.  The only things that might do that are emissions regulations much more stringent than vehicles (already noted), or difficulty in muffling.
Randall Parker writes that wind's lack of schedulability is a problem.  I agree, but I don't think that this is a reason to write it off; its value should be measured by what it can save.  More on this later. 
Another fine post. One quibble is that the system would probably need to include an exterior thermal load dump (an exterior radiator) if the system is to be used as backup power year-round. I don't see that feature as a necessity but most consumers would probably want it. I also think your hoped-for price points are low. Gas furnaces currently cost about $1k and oil furnances about $1.5k, but those are much simpler devices. My guestimate would be for unit costs to be in the $3-4k range, plus installation costs. Stretching out the payback period won't help uptake rates, but installing a cogen device would still be worthwhile.
I've given thought to outdoor radiators, but the extra complexity (esp. of the heat exchange from the engine exhaust) looks like it would drive cost up and efficiency down. The difference between summer and winter outages is crucial, too; there is no risk of severe house damage from burst pipes in the summer, so the extra hardware has no commensurate payback in reduced risk.

At $3k and 7% interest, depreciation and interest would cost about $240/year at the beginning of a 10 year period. If you can get back $700/year in savings you'd be almost $40/month to the good.  That is a significant chunk of change in most people's budgets.
Have you considered that a Stirling engine could be a better fit for cogeneration in homes. Maybe even as a retro-fit to existing furnaces.
I have never actually used one, but
1)They are reputed to be very quiet. 2)They would not change the furnace exhaust at all
3)If they begin to produce excess electricity, it could just shut off that function
4)If designed correctly, the generator part could be moved outside during summer outages and run on any heat source available. For example, hooked up to barbeque propane, an inexpensive kerosene/oil/gasoline burner, or even concentrated solar.

Do Stirling engines have a tragic flaw that I am unaware of?
I have seen a number of Stirling products, such as Whisper Tech out of New Zealand. There are also examples of concentrating solar collectors running Stirling engines; Energy Innovations started on that concept.

Despite their obvious desirability, I note that Stirlings seem to have difficulties coming to market in decent forms: Whisper Tech's machine is only about 11% efficient, and Energy Innovations has dropped the Stirling engine for concentrating photovoltaic.

On top of this, I can get neither price nor durability nor warranty info on anything Stirling. Internal combustion engines are ancient and crude, but they have the virtue of being known quantities.

I didn't mention this in the main post, but one reason I'm betting on a 10-year design lifespan for ICE cogenerators is that I expect that some other technology will be ready to replace them about the time they wear out. That tech may be Stirling, Ericcson, or fuel cell - it doesn't matter as long as the system is designed for modularity and easy service.
Another thought-provoking piece, EP. Keep it up.
First, let me say that I think the idea has great potential. I'm not trying to knock it down at all. I just believe in being a bit conservative on cost projections, with the hope of being pleasantly suprised when finished.

Second, the number I posted over at Futurepundit was just a WAG for comparison against the costs of a certain war. I purposely posted what I thought were high numbers for all the generating systems because I wanted to give a realistic picture of the opportunity cost. Solar, wind, and your device (I forgot to include it over there) would certainly be significantly cheaper if produced in the quantities I listed. (Cost reduction for nuclear is anyone's guess.)

Third, I don't think the Generac is a good comparison. It is a backup power unit with a 1000 hour warranty. While it depends on where the unit is located geographically, how well the residence is insulated, etc., a 10 year lifetime with a 25% duty cycle for 5 months a year yields 9000 hours of operatation. So I think a warranty along the lines of 3000 hours would be in order, especially since it would be the main heating system for homes in cold areas. As a consequence the unit would probably have to be built heavier - better bearings, stiffer crank, bigger oil pump, etc. Perhaps I am wrong, but I think your unit would be a constant-load unit while on, so that would entail strengthing over a load-following unit like the Generac as well. All that means cost.

Fourth, I poked around and found some actual prices on backup units. This Onan NG backup generator with a 1000 hour warranty is $3800 at Costco. This Multiquip diesel generator is going for $4900. I can't find warranty info for it. I found more prices here. Looking elsewhere, prices all seem to be over $3.5k for 10kW units of unspecified warranty length.

Now, of course, I (and you) can reasonably expect your device would be manufactured in much, much larger quantities than these devices, so costs would be lower. OTOH, your device would have some added complexity over those units, such as better soundproofing, better vibration mitigation, heat recovery for the exhaust, and full encapsulation of the unit within the larger furnace unit (exhaust, crankcase gases, oil leaks, etc.). OTOOH, since the unit doesn't need to be fully optimized for crankcase power because the heat is also well utilized, the engine probably doesn't need to be as complex as a dedicated generator unit, which should yield some cost savings.

Fifth, I don't agree that a 4-cylinder engine is 2x the complexity of a 2-cylinder engine. There are serveral one-off parts - water pump, oil pump, starter motor, cam belt, fuel pump, etc. Several parts go on basically as an assembly on all inline engines - cams, cam cover, oil pan, manifolds, etc. Some things do scale linearly - cylinder heads, piston assemblies, fuel injections piping, etc. After all that, I would guestimate that manufacturing and testing a 2-cylinder is about 70% the cost of a 4-cylinder, but less in a location with low labor costs.

So, all that is a long way of saying I'll stick to my $3-4K guesstimate. But I'm not a product engineer for a manufacturing company, so there is no way I can do anything but guess, and thus I could very well be wrong. Still, I don't think $3-4K for the unit kills the idea. Since there are 5 inputs to consider - unit cost, installation cost, fuel cost, purchased electricity cost, and resale electricity cost - the feasability is subject to lots of factors.

Additionally, the price would certainly curve down like most products do - early units would probably run $8k, and 10 years later an improved model of the same BTU output would run $3K. (I'm typing this on a 27" 1280x720 LCD monitor I bought for $900 - certainly a much better value than could be had even 2 years ago.) Installation costs would probably slope down as well. Anyone productizing this would have to incorporate higher initial prices into their business plan.

Well, that turned out long. Hope it makes sense.
I think the cost would be driven down by ruthless optimization:

1.) Low-speed engines can use vacuum to operate the intake valves; this eliminates one cam lobe, cam follower, and pushrod per cylinder (plus rocker arm for an OHV engine).

2.) Exhaust valves can be driven by solenoids.  Bye-bye, valve train.

3.) No separate starter motor is necessary when you have a multi-KW alternator and can force the exhaust valves open to spin the engine for starting.

4.) The NG-fired unit has no fuel pump.

5.) The fixed orientation, low power and immobility may allow liquid cooling by thermosiphon, but for a dollar or so one could add a shaded-pole-motor driven coolant pump fed directly off the alternator output.  Another possibility is a reluctance motor using the impeller blades as the salient poles.

After getting rid of the valve train, most of the fuel system (for gas-fired units) and the coolant pump, the remaining system is barely more complex than a piston-ported 2-cycle engine.  With so much less to go wrong, it should be much easier for it to go 10 years without unscheduled maintenance.

BTW, a 5 kWe unit would need to run about 1500 hours/year to supply a 45 mmBTU/yr heat demand, so 10 years would mean about 15000 hours.  In terms of actual cycles, this is equivalent to 5000 hours on a 3600 RPM unit.

The MultiQuip unit runs at 3600 RPM; Costco has no data sheet for the Cummins Onan, though they do list the engine as a 670 cc Honda (about 20 HP per liter) so it may be running at 1800 RPM.  Both of them have their own weather enclosures.
a few years back, there was the intelligen domestic cogen unit....5kw induction generator hooked to a lister-petter diesel engine, using ordinary fuel oil. Sadly, the company didn't survive. Biggest problem is payback period. Most homeowners don't anticipate staying in their homes long enough to purchase new, presumably more efficient and less expensive to operate systems that cost more than the familiar gas and oil heating appliances. Ground source heat pumps could save lots of electricity, as could heat pump water heaters. Unfortunately, the payback period is just too long for most people. Domestic cogeneration also has the uphill struggle with interconnecting with the existing electric grid for both safety and competitive reasons. The electric utilities are rightly concerned about safety but large numbers of home cogen units will alter their ability to make money selling power to individual homes. Fuel cells might change the landscape in the future, particularly if the fuel cell industry can figure out a way to use natural gas effectively and co-opt the gas industry to help clear some/all of the regulatory hurdles. There's plenty of waste heat from fuel cells too!
Hmmm.  Right you are; the most recent data I could find for the Intelligen A-550 was a PDF file dated 1994.

On the other hand, a lot has changed since 1994:

1.)  Natural gas is much more expensive.
2.)  Natural gas is being widely used for electric generation.
3.)  Oil is over $50/barrel and unlikely to get cheaper soon.
4.)  People are taking global warming seriously.
5.)  Electricity deregulation is being pursued, slowly and carefully.

Ownership of the cogenerator by the building owner isn't the only economic model.  Nothing stops the electric utilities from leasing cogenerators to customers and taking the lion's share of the cost savings; they might even work deals with HVAC contractors to help sell the deals whenever somebody's old furnace breaks down.  If the utility can profit from efficiency, they might well jump on the bandwagon with gusto.
Not designing in a heat-dumping mechanism such as an external radiator, to allow use in warm weather as a generator, is a mistake.

With all-weather electric generation as an option such a unit would become very attractive not just for "usual" domestic users, but also for rural users who want either a back-up generator capability or "off the grid" capabilities. Keeping a house warm enough to prevent pipes from freezing is a relatively trivial matter, as far as "emergency" uses go; a $40 off-the-shelf propane heater from the hardware store can handle that, so it's not going to be much of a selling point. Being able to provide a few kW to run lights and keep the contents of the fridge/freezer from going bad after a summer storm will appeal to a lot more people.

Another option to consider is the use of waste heat for heating domestic water. Possibly as a "pre-heat" tank upstream of the primary water heater if not sufficient to serve as a stand-alone water heater.
If people are willing to pay for the extra complexity (and parasitic losses) to achieve summer backup power capabilities, I see no reason why the option shouldn't be offered. But where I live, summer outages are infrequent and relatively short (even 8/11/03 only took my power out for a bit over 24 hours); the biggest hazard is winter ice storms.

All of this is moot if the user has a plug-in hybrid car with vehicle-to-grid capability; the car provides full backup power as a freebie, so you power the essential appliances of the house from the car until the grid comes back up.  This provides the simplest (and probably cheapest) overall system.

You're right about DHW.  I'm sure you could do something with the engine coolant, so long as it was liquid cooled.  The one difficulty I can see is that the engine exhaust heat exchanger would still have to be cooled, so you'd either have to add complexity to the heat-transfer system to allow the full cogenerator heat output to be directed to DHW or (if you stuck with an air-cooled exhaust heat exchanger) you'd have to confine cogenerative water heating to periods of space-heat demand.  Whether this would yield enough generated electricity to be worth the hardware cost is a good question; perhaps you can take a stab at it.
Well Honda seems to be on the case.
They are and they aren't; an entry on that is literally the next thing in the pipeline.  I just hope I can get it done tonight, because it's already been delayed enough.

(I try to analyze and document in depth, and sacrifice speed for that.  I hope I'm not losing the worth of these pieces by failing to be timely.)
I think your idea about a residential sized cogenerator is such a good one, I ran out and built one myself last year. At the time, I was blissfully unaware of your blog. As it turns out, my system looks a lot like your proposed system.

I used a six horsepower Listeroid diesel engine imported from India. Top speed is 650 rpm. It weighs approx 650 pounds and has a reported mean time between major overhauls of 100,000 hrs.

It is coupled to a 5kw brushed 4 pole generator. (Both products through George at It has two heat exchangers built from converted gas water heaters, one for the engine coolant, a second for the exhaust stream.

In the winter the exiting exhaust gas is less than 100F.

Both heat exchangers run in series prior to my conventional natural gas water heater to serve as pre-heat. If it gets "preheated" enough of course, the gas water heater never comes on.

I have a generator transfer switch so I can switch between utility power or gen power. Because of the difficulties and expense of intertie and the utility non-cooperation, I do not sell excess to the utility.

I think they should be able to sell a nice integrated package for $4,000. I scratch built mine for less than $3,000 and prototypes don't get any mass production benefits really.

I built a couple Stirlings, but was overwhelmed by technical difficulties before I ever got started on higher output models.

If I were king of the world, I'd pass a law that you couldn't build any new generating capacity unless it consisted of residential to neighborhood sized cogenerators. Benefits:

1.Better redundancy with greatly reduced risk of city wide or state wide power outages.

2. Less use of fossil fuel due to inherent cogenerator overall efficiencies.

3. More security. A terrorist won't be interested in knocking out the electricity on my block or my house. Especially since the adjoining blocks could rapidly help out.

4. Reduced stress on the electricity distribution system (aka, the grid). This would have prevented the east coast outage of a couple of years ago, since they wouldn't have been shipping all kinds of electricity across the country. A local problems stays very local.

5. Easy to integrate/change/update. It's pretty cheap to do a few hundred households or neighborhoods as needed. As needs change, you're not locked into the supernuke on the lake as your only solution. There's a lot more flexibility and adapability in this sytem of distributed generation.

6. Scaleable. This works from residential to hospital to industrial to as big as you want to go, all at good efficiencies. You just have to have both needs close together, heat and electricity.

Finest regards,

I believe you mean; gives me a "not found".

The Listeroid engine looks great.  Unfortunately, George hasn't put his Listeroid efficiency curve into standard units like gm/kWh so it's hard to interpret.

I have been looking for something like the Listeroid, but Google's pagerank scheme pushes them down into invisibility and only shows things like Yanmars.  I'll have to see where this can go.
Yes, thanks for correcting my typo. It is indeed George has a number of interesting products and it's a good read as well.

If you are seriously interested in a one cylinder Lister, there are some peculiarities you should be aware of...

Since they only rotate at 650 RPM, and have only 325 power impulses per minute, they unfortunately cause lights to flicker and motors to do analogous things. The flicker is less noticable with our compact fluorescent lights than with our incandescents. I rarely notice it now, but it was distracting at first. Visitors often comment the first time.

Quality control from India is, ummmm, relaxed. If you really want one, you should think of it as a fairly complete kit that needs to be tweaked and massaged and have a few parts replaced. George is very forthright about this issue and supplied the few bits and baubles I needed to get things humming at a reasonable cost. Fit and finish may be shocking to you if you are accustomed to Hondas.

Most Listers vibrate like a banshee. I learned a lot about balancing one cylinder engines. I have mine in the basement on an isolated slab that's 2' x 4' x 10" and you still feel it everywhere in the house. Prior to the isolated slab and the balancing, the neighbors felt it too.

I regret not getting the two cylinder 12 horsepower model. On paper, mine should drive the central AC (smallest compressor commonly available) but it won't. The two banger sounds nicer anyway.

If you're off grid, you can bang a 3.5kw cogenerator together for about $1,500 plus some shipping. The generator transfer switch by itself raised the price by more than $500. By comparison, the Whispergen costs many times more to produce a fraction of the output. It is of course sexy and quiet and all sorted out, so that's worth something. I prefer my Lister because I can work on it myself.

Finest regards,

Troy, have you considered harmonic dampers to quell some of the vibration?  A mass on a spring resonant at 10.8 Hz should absorb most of the up/down vibration from the piston, and a rotary damper at 5.4 Hz mounted to one of the flywheels might smooth out the variations from power pulses.
For the record, I'm unimpressed with the Whispergen's specs; the data I found were incomplete, but the specified electric and heat output indicated a thermal efficiency of around 11%.  Honda's engine gets twice that, and the Listeroid may hit 30%; I will have to re-check the numbers on George's site.

What is the price range for Listeroids?
Prices: I think the six horse one cylinder runs a shade over or under $1,000 depending on exchange rates, suppliers, etc etc etc. Shipping will add 20-40% depending on how far away you are.

On the twin, I'd guess $1,500 but that's just a guess.

Finest regards,

Your input is pertinent and much appreciated.
personally i am in love with the cogen topic. i have been studying this concept for many years now.

a few points i would like to make.

i suspect a more true cost, will be inline with about 5-6,000 dollars.

the successful engine will likely be a water cooled dual fuel diesel. A diesel has a much higher efficiency, and running in dual fuel mode most of the emission concerns can be mitigated.

thermal mass storage should be incorporated to pick up the overall efficiency, and reduce run time.

currently a friend and myself are building two cogenerators, both are going to be used for offgrid homes, so no power will be sold to power companies.

they are based on the changfa 12hp water cooled single cylinder diesel engine, r195 series

they use approx 251 grams fuel per kwatt hour, so they are fairly efficient to start with.

they are governed to 2000 rpm, his will be set at 1800 to direct drive an 1800 rpm 4pole head 7.5 kwatt,
mine will be belt drive governed to 1500 rpm and drive the same 1800 rpm head,

added features on mine will be two (2)delco 150 amp alternators, and one a/c compressor.

the alternators will be controlled with a marine 4 step charge controller to take over the charging regime of a 1500 amp hour bank.

the a/c compressor will provide 50kbtu of cooling for thermal storage/summer air conditioning loads and refrigeration.

water jacket heat will be recovered for space heating, and the exhaust heat will be recovered for domestic hot water and thermal storage.

the same thermal storage that provides cold storage in summer will be reversed for heat storage in winter.

these two units are going to be the prototypes of units we hope to manufacture for resale.

my worry is there will be those that enter the market with poorly designed cheaply manufactured units that ruin the public image of the concept. ie. such as using small high speed (3600 rpm) consumer grade engines as the prime mover, cheap drives, pathetic windings with unrealistic load ratings, and cheap and inefficient heat exchangers to name a few.

i think residential cogeneration/trigeneration is an emerging market with great potential.

bob g
Dual fuel?  Do you mean diesel/natural gas or diesel/LPG, or something else?  (Have you considered a wood gasifier as your gas source?)

It's excellent that you've got your target price down to $6000 or less.  How well do you expect your noise abatement to work?
The biggest problem with this system is that it's (as designed) only applicable to areas that want excess heat -- i.e., places with harsh winters. For decades now the trend in the United States has been towards depopulation of the northern climes in favor of the Sun Belt. The proposed system would therefore benefit a shrinking percentage of the population.

Now if you can build an efficient cogeneration plant that air conditions, you'll have a market 2-3 times larger. Is this possible to do and still get the increase in efficiency?
Engine life is critical to the economics of the scheme. A home engine swap in mid winter after throwing a rod or swallowing a valve could be costly. A new engine for a Dodge Intrepid set me back $5K some years ago. A new engine for my home cogen plant might be just as expensive.
Car engines run 200K miles, or maybe 4000 hours before they need a total rebuild meaning bore the cylinders, mill the heads, new rings and bearings, essentially remanufacture the entire engine.
A year is 8760 hours. So a small car engine ticking over in your basement will be lucky to make it thru one heating season (half a year). For a 10 year life, we are looking for an engine with 10 to 20 times the life of a current day car engine. Are such engines available? Now? sometime in the future?
'Tis true that cogeneration for home heat only yields benefits where homes need heating.  Both warmer climes and better architecture can slash or even eliminate that.  But unless you are going to either depopulate the northern and mountainous areas or replace their building stock, that category is still going to include a lot.

Absorption-cycle chillers can make cold from heat, but their efficiency is rather low (CoP around 0.5 to 0.8).  If you have to use natural gas or fuel oil, you are probably better off burning it in a combined-cycle gas turbine plant at 55-60% and running an electric A/C rather than trying to cogenerate with lots of little engines getting maybe 30%.  You'll certainly have an easier time controlling emissions.

If you live in an area where you need A/C all the time, why not drive an absorption system with solar heat?  They're expensive now but I suspect this is due to low production volume.

taxpayer:  The prices I'm seeing for Lister clones (one-cylinder, 4.4 kWe) are under $2k, and I've been quoted under $1k FOB Washington state.  A proper design, with standard interfaces for all fluid and wiring connections, would allow a whole engine to be swapped out in a few hours and repaired or rebuilt at leisure in a nice, warm shop.  If the heat is sold as a utility rather than selling furnace-replacements, this is no longer the homeowner's problem.

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