microcogen gen 1, 2, 3...

[mobile_bob]

doing a bit of theorizing this morning and thought i would kick this out for debate

microcogen generation #1: 

we use a prime mover make power and harvest heat for domestic hot water and/or heating loads, the engine runs long hours because we
need continously available power, so the prime mover runs typically at part or low load and is not very efficient.

microcogen generation #2:

we marry the genset to an inverter/charger and batteries, so that the prime mover does not have to run continously, and when it does run
it can do so at near full rated load, efficiency of the prime mover increases, but we must offset some of the increase in efficiency of the genset
with the losses of the charger/batteries/inverter. even so the there is still a gain in efficiency over running continuously at part load.

now the next step

microcogen generation #3:

we apply to the generation #2 system above a control system that does the following, it monitors specific loads and is programmed to
start the genset to provide power to specific loads that are large enough and run long enough to be more efficiently supported directly from
the genset rather from the battery/inverter system if we factor in the charging of the batteries from the genset later.

i haven't run all the numbers yet, but my thinking is Generation #3 will prove to be significantly more efficient than the Generation #2 system above and dramatically more efficient than Generation #1

also without crunching the numbers it would appear that the battery bank could be sized significantly smaller, and the use of agm batteries
with their ability to deliver higher output on a short term basis, along with their inherent ability to charge faster and more efficiently, might offset
the premium in first cost over the flooded lead acid battery.

it might also work out to be true that power sharing between battery/inverter and genset might be more efficient
with this scheme (using a washing machine as the load to be serviced) the load might need a half hour of power,
it might be more efficient have the controller recognize the load, know what its needs are, and deliver the first half via the battery/inverter
and the second half via genset while also recharging what was taken from the batteries in the first half of the load cycle. this would reduce
run time and increase the load presented to the genset so that it remains near full load where it runs most efficiently.

i mention full load as being the point of peak efficiency based on the s195 idi changfa, as that is where peak efficiency is for that engine
other engines might prove to be at peak efficiency at 75% or some other load so one would design and program to suit the prime mover used.

i already have generation #2 capability and will be starting on the controller end of things which would allow for moving up to Generation #3
so added costs will be trivial monetarily, although complexity of thought/design/implementation will take some time.

what do i hope to gain from this endevour

1. lower overall system cost, fewer batteries will save a rather significant amount of money

2. increased overall system efficiency, reduction in fuel expense should be significant

3. reduction in pollution, both air and noise

4. increased system longevity as measured in years

5. lower maintenance requirements, in both cost and time

6. closer matching of thermal capacity to thermal load, more frequent availability
of recovered heat

7. higher quality of heat recovered, the prime mover operating at full load
produces recovered heat that is much higher temp than that which is produced
at low or part load.

i think the savings in battery costs will be very significant, likely a reduction in amp/hr capacity
required would be from 50-60%, perhaps even more. with the cost of high quality batteries at an all time
high, this reduction in amp/hr capacity required equates to several thousands of dollars.

any thoughts fella's

anyone working on a similar scheme? i wanna hear about it

bob g

[Crumpite]

Bob,

I'm planning on a system like your #3.
I'm hampered by the fact that most of my high electrical loads are fairly short in duration.
I'm pretty happy that I chose a 6/1 for my system, anything larger would have been a waste, so to speak.
I really need to get my system up and running and take some measurements to see if an intelligent load share/shed is worth the trouble.
I've considered that it might actually pay to sell the power back to the company just to load the engine efficiently.

Too many questions, not enough answers yet...
Crumpite

[Lloyd]

Bob,

Mechron did a portion of this same concept long ago...they just didn't use the co-gen heat http://www.mechron.com/pdf/Final%20Sample%20Project%20-%20ATT%20Cycle%20Charge.pdf

The pdf has a very good economic lesson on the pros and cons AC prime v. DC bat charger.


It' speaks to the change from a prime mover 120 volt to a DC bus system, using a dual purpose alternator, that can switch between AC or DC output, the interesting thing, is the savings from the new configuration to dc based gen, and AC standby. It is quite a good economic study.

WOW.

Also Victron makes an inverter that is designed to use bat power as a supplement to Prime Power AC... thus allowing you to size the prime mover smaller.

Lloyd

[mobile_bob]

thanks Lloyd:

the mechron pdf does two things

1. it supports the theory conceptually, and

2. it proves there is nothing new under the sun



both of which are very encouraging in my opinion.

Crumpite:

i started with the s195 because i have use for a larger amount of heat that is recoverable, but
certainly will also develop a smaller version based on the r175 changfa or similar for those times
of the year that my thermal needs are quite low.

thanks for the input guys, nice to have somebody to bounce idea's around with.

bob g