Earlier this month Michael Schooley wrote:

ARILD  REPLIES:
I finally got around to  investigating the Stirling cycle engine genset in
detail.
Mike mentioned the  price as being steep and so did  several other poeple
on the Lv-ab list.
They  compared the $12K  price with a Panda genset at $8K.
However,  that is  comparing apples and oranges.

The  Whispergen is only  one part of a system.  The AC  power is provided
by an inverter.
Two  appliances uses  very  large amounts of  AC power and  produce  high
surges which necessitates a very big expensive  inverter.

A  washing machine  ( Splendide brand)  is rated as a 15 amps  appliance
but  people have measured  40 amp surges when the  spindle( hub)  reverses
direction every minute.  A couple of  Trace  inverters fried as a result
and I got to handle the complaint call.
The other  big energy peak  user is  a water maker ( reverse osmosis type)
Typically you have a 3 - 5 HP  elecrtic motor driving the pump which  has
to produce a pressure of 2200 PSI or thereabouts.

Air conditioning  is yet another but this is one  area which may not be
economically feasible. ( bear with me)

The  Whispergen produces  about  6 Kw or 20,000 BTU of heat  which can be
used to heat cabins and  drive an evaporation  distillation  water maker.
So now you should add the cost of a heating sustem to the  package cost  as
well as the  water maker.
Today at the yacht club I  met someone  who sells such  water makes.  He
indicated gthey were not popular for  pleasuer yachts because  of the
amount of heat required.  However this is a perfect match for a Stirling
engine.
Most boats  in the PNW area as well as Maine and  some of the Great Lakes
also  require cabin heat even during the summer months ( certainly during
spring and fall)  so the cost of the  heating system appliance should also
be included  for comparison.

So now we have  a Genset for $8K  or more,  I believe a Fischer Panda  8Kw
gensert installed,  cost about  $13,000 at Wards Electric in Florida.  The
cost of a  decent sized  water make will run anywhere from $4000 -  $ 8,000
plus installation and the Espar or WEbasto furnace system cost around $3K
plus installation  which could double the  final cost depending on
complexicity.

The conventional system  cost  look like this.
Adding $8K + $4K + $3K =  $15,000 plus installation which might run
anywhere from $5K to  $10K. for a total of $20K - $25K

The Whispergen system  would cost about the same or less.
Base cost of Whisper gen is $12K  The  evaporative water maker cost about
$3K  and the  installation of  hot water radiators  would be the same
whether or not you  use an ESPAR  hydronics unit or Webasto hot water system.
I suppose it would be feasible to  use a large water to air  heat exchanger
and have a forced hot air system if you prefer.
I can't comment  on cost  since I have not installed  such a system.  Lets
assume $3 - $5K  for  that installation.

That now  brings the total cost of the  alternative to  $12K + $3K = $3 or
$5K  for a total  of  $18K - $20K  for  comparable  functionality.

I should  mention that the  evaporative water maker can produce about 50
gallons  per hour and the purity of  water is about 2 ppm salt compared to
a much higher  50 ppm  for reverse osmosis.
The electrical load of the  evaporative unit is  very much less than the
reverse osmosis unit so  there is a correspondingly lower  demand on the
batteries.

The inverter is likely to be the same for both  installations since the
washing machine  is still includerd in the  load list.
However,  you do not have to  use electrical  power for  the hot water heater.

I'm also making an assumption that the cost of  plumbing in  both genset
and propulsion engine  into the water system for using  engine heat  when
available or to preheat the block  during cold weather starts.  Therefore
such an option does not  differ in the comparison.

Now for the intangibles.
Service and maintenance cost  of the Whispergen  versus a diesel genset.

Count on  an oil change every 50 hours of run time for the  internal
combustion engine.  By compariosn the  burner in the whispergen  requires
servicing about once a year.  Having once worked as a furnace service man
helper I estimate the  cost of a service call would be the same.  The
question now becomes how many  hours would you run per year.
If you have to service the internal combustion  driven genset more than
once a year then  the cost  comparison favors the Whispergen.
If  you  run the  genset  lightly loaded, chances are you end up with
glazed cylinder walls.  No such problem with  Whispergen.

The  noise and vibration  from a conventional diesel genset annoys  many
people forcing them to install a charging system which can  recharge the
battery bank in a couple of hours  run time.
Some places have restrictions on  generator run times.  Some places (
parks ) even  have total bans due to noise.
No such restrictions on heaters or Stirling  engines.
Since the  electrical system is designed  for self sufficiency  it is
possible that a boat may not even need to  connect to shore power.
That  increases  the number of suitable  docks  for overnight stays if you
do not wnat to anchor out.

The downside of the Whispergen is the limited amount of power it can
generate.  Unless  the  owner practices  extreme  energy conservation, it
is my guess that  this system is limited to boat  under the 65 foot range.

Over that size, power  demands are quite often  such that  these boats
become what I call AC boats with full time  diesel gensets running 24/7
when away from a dock and shorepower.

I haven't yet made any calcculations  to see if  a Whispergen  system
would require a smaller batery bank but the early indications are that this
is feasible given a continual  supply of  charging current round the  clock.

For long  distance passagemaker boats  the propulsion  engine can be
plumbed into the  loop and  the  water maker plus cabin heat would still be
functional.  The Stirling engine would be shut off.
A minor benefit would be that you no longer would need such a big  honking
alternator  on the  propulsion engine.  A regular  100 amp continuous duty
unit would do instead of a huge  amp output unit which cost a lot more.

The supplier  of the evaporative water maker told me the  unit is much less
sensitive to contaminations from things like diesel fuel spills in harbor
waters  etc.  And  regular maintenance  is less costly than with a membrane
for reverse osmosis.

SUMMARY
The Whispergen is not suitable as a replacement  to a normal genset if you
only look at  swapping out  one component of the whole boat system.
However, if you are looking at  a newbuild  or a complete refurbishment or
upgrade, then the economics  look good.
The final  decvision may well be  how you view the intangibles like no
noise and  less maintenance headaches plus  a lot less psace  needed for
the  equipment.

Cheers

Arild

----- Original Message -----
From: "Arild Jensen" elnav@uniserve.com

this

clock.

Hello again Arild,

A quick and dirty calculation of 750watts X 24hours = 18kwhr/day. I'm sure
that misses some subtleties but what can you expect? I've only recently come
to the conclusion that electricity isn't a passing fad after all.

Assuming that 18kwhr/day figure is close enough for jazz it would seem to be
right in line with today's common practices. A 3 hour daily runtime for a
traditional genset sounds fairly reasonable. In that time a 6kw running flat
out or an 8kw running at about 70% would produce the same total power.

OTOH: At 750 watts output the Whispergen isn't going to run much of anything
by itself. It strikes me that the Whispergen is a viable alternative for a
new build or major refit as you said. It also seems that the designer and
owner will have to rethink their strategies for what types of loads are
installed (12v vs. 110v vs. "You can't have that.") as well as how the power
for those loads is managed.

Another issue worth raising is that a Sterling engine, as I understand it,
is an external combustion engine. To run a Whispergen or similar 24/7
implies that there will be a fire on the boat 24/7. In my head I'm pretty
sure that this is very safe. In my gut I think that might make me nervous if
I wanted to spend a day ashore while cruising. I know that there are folks
who leave their diesel furnaces active when they're away from the boat and I
have left electric space heaters untended on my boat so maybe this isn't a
valid concern. Sometimes, though, the invalid concerns are the toughest ones
to deal with.

Legitimately yours,

Alex

Earlier this month Michael Schooley wrote:

ARILD  REPLIES:
<<I finally got around to investigating the Stirling cycle engine genset in
detail. Mike mentioned the price as being steep and so did several other
poeple on the Lv-ab list. They compared the $12K  price with a Panda genset
at $8K. However, that is comparing apples and oranges.>>

I think there are really two trade-offs here. The first is the AC generator
versus to DC generator trade. The second is the internal combustion engine
versus the Stirling cycle engine.

Many of your arguments for and against the WisperGen also apply to DC
generators. The key to using any DC generator efficiently is eliminating
large AC motors and/or getting a very good inverter to run the remaining AC
loads.

Washer/dryer - If there is a super compact single unit DC washer/dryer combo
I would sure like to know about it. Running any AC washer/dryer off an
inverter is challenging. As you point out you need to be very careful of the
motor "start-up" loads and make sure your inverter can handle them. If the
inverter is marginal you will need to be very careful not to run any other
AC loads while you wash clothes. If price is no object, I would recommend a
dedicated inverter for the washer. Otherwise only run the washer off shore
power.

Water maker - If you go with a DC generator you should use a DC water maker.
The high efficiency units with waste pressure recovery can produce about 1
gallon per amp hour. The DC water makers tend to be much smaller than AC
systems since they can run for a longer period to meet your requirements.
The evaporative water maker is an interesting alternative. I wonder if it
could be run of the exhaust heat of an internal combustion engine?

Air conditioning - I would recommend a DC air conditioning system such as
the Glacier Bay "Artic Air" system http://www.glacierbay.com/Arctic.htm .

Space heat - Both AC and DC generators could be used to heat the boat using
waste heat recovered from the water jacket and/or exhaust. Polar Power sells
an exhaust heat exchanger
http://www.polarpowerinc.com/products/heat_exchanger/heat_exchanger.htm
designed to fit 5 to 20 KW generators for $879.00. It provides up to 50,000
BTU/hr of heating capacity. This is defined as a "co-generation" system or
the combined generation of power and heat. I think this is a much more cost
effective solution than a diesel heater but maybe I am missing something?
Although I do understand that is much easier to incorporate into a new
design than a retrofit. So what do you do when you need heat but you don't
have any electrical load for the generator? Use electric space heaters. Not
only does it provide a generator load but it provides the ability to heat
the boat from shore power.

At low loads, DC generators tend to be much quieter than AC generators
because the required engine is smaller (the batteries provide peak loads so
the DC generator is sized to the steady state loads) and they can vary their
speed to match the load whereas the AC generator must run at an integer
multiple of the AC power frequency (i.e. 60 Hz = 3600 rpm. Therefore a 2
pole generator operates at 3600 rpm for 60 Hz or 3000 rpm for 50 Hz.
Likewise a 4 pole generator runs at 1800 or 1500 and a 6 pole runs at 1200
or 1000 rpm). This makes the DC generator a better choice for co-generation
systems.

On the Stirling versus Internal Combustion engine trade-off. The Stirling
engine is much quieter and lower maintenance but it is less efficient (16%
versus typically 23% to 26% for small gas and diesel generators) and also
more expensive primarily due to the lack of technical maturity and
production volume.

Regarding the engine alternator. Since the WisperGen efficiency is lower
than the main engine. I would retain the large alternator on the main engine
and only run the WisperGen when the main engine is off and the battery bank
gets low or I need heat. With exhaust heat recovery I could get enough heat
from the main engine (when it is running) to heat water and to heat the boat
and possible run an evaporative water maker. This way the low efficiency of
the WisperGen doesn't impact range and having two separate power generation
capabilities provides electrical redundancy.

Evaporative water maker - I am intrigued by this concept. I have looked into
some of these systems but I am still trying to find one that meets my space
requirements.

Since space will be limited in my trailerable trawler, I am considering
putting a hydraulic pump on the main engine and a hydraulic driving 3.4 KW
DC alternator. The 180 HP main engine will provide enough power to run the
hydraulic generator at 600 to 800 rpm. With a good muffler and sound
proofing I think the noise level at this speed should be tolerable, but I
could be wrong. (Now if somebody would just build an extremely compact
washer/dryer combo that used hydraulic motors!;-) I would mount a second
(identical) belt drive alternator on the main engine for a back-up for
hydraulic system or alternator failure. I will probably leave the belts
disconnected.

I would appreciate ANY feedback that anyone is willing to provide regarding
this concept.

Energetically yours;
Mike Schooley
Trailerable Trawler wannabe