Lister WVO Generator - Sept/Oct Results.

[KenB]

Ivan, List,

You know I always like to "tell it how it is"  - so here are the good, bad and ugly facts about running the Lister WVO generator since September 21st.

Fuel Used                                       95 litres of WVO
Energy Content of WVO                 (95 x 9.4kWh) =  893kWh
Nat Gas Equiv. cost                         893kWh @ 3p/kWh  = £26.79

Number of days of trial                    37
Number of days engine started         25
Accumulated Run time                    4300 minutes   (71 hours 40 minutes)
Average run /day                           2 hours 52 mins
Average over 37 day trial                1 hour 56 mins

Electricity metered from inverter       103.04kWh
Plus battery storage                        7kWh
Value of electricity (@10p/kwh)        £10.30

Average Electricity usage                 (103.04/37) = 2.785kWh

Average daily grid use before trial      8.20kWh / day
Average daily grid use during trial      6.19kWh /day

Average reduction in grid usage       2.01kWh
Percentage  Reduction                   24.5%

Overall electrical efficiency              (103.04/893) =11.54%

Summary

The WVO powered Lister generator has put a 25% dent in my grid electricity usage over the period of the trial,  running the engine on 25 out of the 37 days of the trial.

The battery bank and inverter is a major source of inefficiency especially on low load, effectively halving the electricity produced per litre of fuel.  It is essential that a good quality alternator is used, so that appliances can be run directly off the generated power.

The engine should not be run for periods less than 2 hours per day, this is the minumum recommended time for system warm up and improved fuel consumption.

A high pressure fuel line heater should be used in order to get good fuel  efficiency from burning cold waste vegetable oil.

Running the engine for on average 2 hours per day produced a 25% reduction in my grid power consumption.  Running for 8 hours per day, would allow complete freedom from grid.

The engine was running at a peak  power of  4.4kWduring the early stage of battery charging with 3500W of electrical power produced.

One litre of WVO lasts on average 45 minutes, under the conditions of the trial.

Insufficient data is available for the hot water output of the engine, however after 2 hours of running water was reaching the house at 55 C  (Wilo circulation pump set on setting 3).  The 120l thermal store was up to 90C.

Conclusion.

Running a Lister on WVO can make an appreciable dent in your grid power consumption and provide a considerable amount of hot water.

The engine should be run at about 3/4 load, for as long as possible each day, even if this means running resistance heaters (storage and immersion heaters) in order to keep the load on the engine high.

The inverter and battery was a major source of losses in my system.  If you choose to run an inverter and battery system, check the efficiency of the inverter at low loads <500W.

Allow for 1.33 litres of fuel consumption per hour.

The raw output of a typical ST alternator will vary in frequency and voltage as the load on the engine changes.  The output waveshape of the ST alternator is not true sinusoid and has a couple of discontinuities in the waveform which may upset the controller in some appliances such as washing machines.

In my enthusiasm to run the Lister on all sorts of loads, I have been using it at every opportunity. As a result, the total energy consumption of the household INCREASED for the period of the trial, as a result of extra dishwasher and washing machine usage, and running the storage heater in my office.





Ken

[Flamethrower_]

Ken,

Great set of results

I've being toying with the idea of a lister/ or clone for a long while and have followed your results with interest, a question I would like to pose is if you ran your lister for longer periods, would the output be sufficient to supply a large thermal store via its waste heat and dump immersion loads and would this improve your efficency and load performance ?

Rob

[KenB]

Rob, List

The Lister currently has a 120 litre copper cylinder for it to thermosyphon into. Within 2 hours of running, this water is up in the 90s.

I took this approach to ensure that the Lister always has an adequate reserve of cooling water, is not reliant on a pump and is unlikely to boil dry.

I also have an exhaust gas heat exchanger, which will add 30 degrees of heat to the incoming water (the return from the house).  This heated water then flows through the coil of the 120 litre store.  In the early stages of a run, it starts to warm the water in the tank, and then as the tank heats up it extracts heat from the tank and circulates it to the house.

The store acts as a moderator, and ensures that the exhaust gas heat exchanger won't suddenly start producing steam, and keeps the hot water flow from the system down to about 80 C - even after a long run.

It is my intention to fit a larger thermal store. I have a suitable 300 litre steel cylinder.  I am going to build a big super insulated "cupboard" around this store with 75 or 100 mm of kingspan insulation. The Lister would take approximately 6 hours of running to heat this up sensibly, under the current running regime.

If a 3kW immersion heater is used as a dump load, the Lister will take 7 or 8 hours to heat the 300 litre store electrically.  However for this time it will be running at full output, and there will also be a constant 5kW or 6kW of heated water available from the coolant and exhaust gas heat exchanger.

I can quite easily fit a 3kW dump load immersion heater, and I am already using a 1.7kW electric storage heater in my office to help keep a sensible amount of load on the engine.  Diesel engines only return their best efficiency when run at full temperature for long periods of time. I consider with my existing set up that 2 hours is the minimum desired run time.

I am not sure whether I would like to wait 6 hours for hot water to start to flow into the house - it represents a considerable thermal lag.  What I might do is divert some of the heated water to the store, whilst sending the bulk to  the house - depending on the heat demand in the house.  I have yet to finalise the plumbing configuration, but  a 300 litre store at 95 C represents about 22.5kWh of storage, enough to heat the house for about 5 to 7 hours depending on the outside temperature.

Whilst the battery and inverter route seemed a sensible strategy at first, with hindsight I will probably change the configuration to use more power directly generated by the ST alternator.  The dishwasher seemed happy on ST power, as did my washing machine.

I will make use of a more efficient 1500W UPS to maintain the "computer grade" ac power required by my office. Everything else can run off the raw power from the ST alternator.

Hopefully these changes will bring back the efficiency of the fuel to power conversion.  Tests done with the ST showed that about 2kWh of ac power should be available per litre of WVO.

The engine shed has grown an extension this weekend, a further 8' x 10' insulated area, intended for the thermal store cupboard and the bulk WVO tank.  Sorry no pictures at this stage - digital camera died on Saturday 



Ken

[KenB]

Ivan, List,

Further to my earlier post I should like to illustrate some fundamental points about a WVO generator set up. Some of these will be obvious,  but some points have only recently been ascertained as a result of the recent trial.

1.  WVO is a hydrocarbon fuel and has an energy content approximately 90% that of diesel.  1 litre contains 9.4kWh of energy, and if burned directly in a Babington or Turk burner, 1 litre would replace about £0.25 of natural gas at current prices.

2. The diesel engine can burn WVO efficiently, provided that the WVO is heated up to >75C at the point where it enters the fuel injector.

3. A standard 6hp Lister can convert waste vegetable oil to electricity with a maximum efficiency of 24%. This could possibly be improved slightly by ensuring the oil is hot, the engine lagged and running on a constant load.  This figure arose from tests done in 2006 with a 6hp Lister and a 3kW ST alternator.

4. Speed regulation on the standard Lister is quite poor. Expect the voltage and frequency to drop by about 10% when the engine is fully loaded.

5. The ST alternator is cheap and cheerful, but the quality of the output waveform has something to be desired.  As the ST consists of two separate stator coils wired in series, any manufacturing difference between these coils will result in an output waveform that has discontinuities in the sinusoid. These discontinuities might upset modern electronics, as experienced by a friend who found his washing machine would not run well on ST power.

6. Producing dc and charging a battery bank will result in fairly high losses in the electrical efficiency of the system. The combination of batteries and inverter might lead to as much as a 45% reduction in the efficiency, especially if the inverter has low efficiency at low load.  The fuel to electricity conversion efficiency dropped to an average of 11.5% when using the battery and inverter. This results in more heat generated, but sadly none that can be effectively captured - mostly good for warming the shed.

7. The "equal thirds" rule can be applied to a WVO diesel generator set.  1/3rd of the fuel energy appears as mechanical work,  1/3rd is dissipated in the cooling system and 1/3rd comes out of the exhaust.  The exhaust temperatures can reach 400C and an efficient exhaust heat exchanger can capture and convert this heat to hot water.
 
8. Thermosyphoning the coolant into a 120 litre cylinder will cool the Lister, and produce a fully heated cylinder in about 3 hours.  Using the indirect coil in the cylinder is a practical method of extracting this heat from the store.  At night the Lister will reverse thermosyphon from the store and this helps keep its block warm and prevent freezing.

9.  If the WVO is not pre-heated before the injector, the exhaust will be sooty and the cylinder head and valves will need to be decoked at regular intervals depending on usage.l

10.  Using a Lister for power generation is an engaging pastime, and unless you are normally at home to keep an eye on it, the existing system is far from an automatic arrangement.



Ken

[Twenty4Seven]

  Sorry no pictures at this stage - digital camera died on Saturday 

Ken

Drop another 4 by 2 on it ?

 

[Ivan]

Ken,

1.) I'm sure I've already asked and you've answered, but can you remind me - are you using a thermostat in your convection hot water cylinder heated from the engine's coolant. Efficiency would be low for extended periods if you are not using one. I never found a satisfactory answer as to whether the lister convects sufficiently well with a water thermostat to avoid overheating - one of my concerns which steered me away from this when designing my system.

2.) One possible application of the lister might be to run a heatpump. A 2kW electrical output could run 8+kW of heatpump - giving a total of 8kW plus 8kW of waste heat from the lister itself.


Ivan

[KenB]

Ivan, List,

I'm not yet using a wax thermostat in the coolant. However there's a nasty kink in the pipe that reduces the flow to a dribble and the engine still hasn't overheated, but still thermosyphons well.

I will be fitting a thermostat when I next put on my plumbing hat. Been busy extending the engine shed by another 8 feet and getting it felted and battonned before it precipitates down again.

The idea of using a heatpump is an interesting one.  An airsource heat pump could suck all the waste heat from the
engine room, concentrate it into hot water and deliver it back to the house.


Ken

[KenB]

24/7 & List,

Digital camera is resurrected   

I thought "what the heck"  and gave it a good couple of knocks against my knee before turning it on.  Mechanical problem that was preventing the shutter and zoom lens from opening out has now gone away.

Pictures of extended engine shed tomorrow hopefully.

In the meantime, here's a picture of out cat Monty, doing what he does best - warming the bottom of the bed.

Now I don't want to hear any jokes about Mrs. Slowcum's Pussy....





Ken

[Ivan]

Ken,

Fitting a thermostat might in theory improve efficiency - but then again, your kinked pipework might be restricting flow sufficiently to allow the engine to heat up to operating temperature even when cylinder is at low temperature. My gut feeling is that circulation by thermosyphon alone might be too slow to cool the engine if it has to go though a thermostat, especially at high power outputs, but I have certainly been told by CS thermostat suppliers that they think it would be ok.

I have seen plenty of air-air heatpumps, but air source-water delivery heatpumps are not so common - although they are used for swimming pools.

[KenB]

Ivan, List,

Decided tonight that it was time to get "low down and dirty"  and decouple the failed permanent magnet dc generator from the Lister.

I then spent half an hour trying to start the engine by hand - oh for an electric start!  and it was only with the blowtorch on the hp line glowing red and the hot air gun buried in the air intake that the dear old chap decided to co-operate. 

Admittedly the temperature in the shed was down at about 2 degrees C when I started - nothing like a cold block and thick oil to make life extremely difficult.  Then when I warmed up the air inlet -the inlet valve started to leak a little compression - SOB.
 
Well to cut a long story short, finally got it going at 9pm and ran it for 90 minutes on the ST alternator.  I connected up the newly acquired 1200 degree furnace and got that up to 650 C and glowing nicely when I shut it down at 10:30pm.

It its unmodified form, the 3kW ST is a bit of a wimp - making only about 2200W at 1500rpm, about 12.5A at 209V was typical throughout this evening's run.

Another Lister friend called in yesterday and said that he had improved the field excitation circuit on the ST alternator by using a bridge rectifier from Farnell and smoothing the voltage with some nice big electrolytic capacitors.  This seems a sensible and cost effective approach.

He  also  recommended the PTC heating elements from Farnell for heating the hp line.  I bought a couple for about £12 each that will heat up to about 130 degrees C and self regulate.  It might be a 100W drain on the alternator, but it will improve combustion efficiency  considerably.   75mm long - a  simple aluminium extrusion that can be clamped to the hp line and well insulated. Runs off any ac voltage from 110 to 240 V.

I really miss my PMDC genny, it used to be able to dump 120V at 32A into the batteries for a couple of hours continuously, which meant that you could run a big load off the inverter at the same time and not flatten the batteries. Even with 3600W electrical load, and the Lister would not complain.

The ST alternator does not like the transformer/rectifier battery charger that came with the inverter.  The power factor is down at around 0.65 and it wimps out at about 1100W into the batteries.  This is very typical of simple transformer rectifier chargers, its just that the mains supply is usually stiff enough not to care

What I would really like (cash permitting) is a big old dc genny from the 1930s.  These were used on gas engines and directly coupled to the slow speed engines- often turning around 600rpm.

Preston services (googlit)  near Canterbury is the best place to find one of these - but as with everything to do with vintage machinery  - it'll cost you an arm and a leg.

I remember the line of showman's engines at the Great Dorset Steam Fair,  with their dc gennys whirring and all lit up like a Christmas trees.  A good showmans engine could produce 20kW,  200 amps at 110V dc, coupled to the roundabout or dodgem cars with welding cable just laid across the field. 

Keep it simple

(For some scary evening entertainment - enter "Darwin Award" into the YouTube search facility)

I'm going out now, I may be some time.....




Ken

[Billy]

Hi Ken.

Been following tail and would love one of the old thumpers but no space in the engine room.  I work on boats and we have all sorts of problems with 10kva gennies being run to power the telly.  What I do is run a 7hp water cooled yanmar with a 24v 70amp alternator to charge the batteries thru a smart charger, then run the inverters to power the ac load.  To mittigate the efficiency problem I run the music, tv etc off a small inverter, the one I got with the wind genny, and use the 3kw Victron for the appliances and cooker (not all at the same time off course).  The water from the engine and water cooled manifold go to heat the hot water and a dump rad in the wheelhouse.  If you have to have batteries and inverters, I thinks it must be better to run it this way than to make 240v or whatever, then change it back to 24v and then back to 240v again.  There are a couple of companies making charging plants like this but not too high on take up as it's "different".  I quess the mid point would be to have a small genny running at a good load and then if needed, the power assist from the inverter could balance extra load when needed.  Which is exactly what you have sort of done I!

Look forward to your next installment,

Billy

[KenB]

Billy, List,

Thanks for your comments.

The Lister is running now - for about the last 3 hours, and the water is coming into the house at 60C.

I've got a temperature data logger on it today to watch its progress.

I think I've got enough waste heat for 2 rads, the UFH loop and my hot water cylinder - yet to be Listerised.

I ran it for 8hrs 15 mins yesterday using about 10 litres of fuel and produced 17.1kWh - mostly to recharge my battery bank and power a storage heater in my office.

The living room got up to a staggering 23 C -  we normally don't heat it above 20C.

There's lots of minor jobs still to do to improve the system, but I've now got it to the point where I can put some hours on it.

I'm almost in a position where I will consider buying used veg oil in a bulk 1000 litre container.



Ken

[Antman]

Ken and all

Have you seen the neat little Lascar USB data loggers that Rapid Electronics are sellling?  See 85-3410  at  http://www.rapidonline.com

There are also Temp+Humidity, voltage and 4-20mA versions in the range. The disadvantage is that they are only single channel but you can't have everything...

Further to this a colleague pointed me in the direction of the following project in the November Elektor magazine:
http://www.elektor.com/magazines/2007/november/usb-data-acquisition-card.271706.lynkx

8 x analogue and 8 x digital inputs
2 x analogue and 8 x digital outputs

Shame it won't work with in parallel with the Resol....

Antman

[bqjohn]

Hi, sounds like a good chp installation. Probably been mentioned before, but a simple method of keeping your heat source hot (e.g. Engine, Solid Fuel boiler) for efficiency is to put a blending valve on the return to limit the return temp. if your heating a large store directly without a coil.

[stephen]

Ken and others,
I too have a lister CS just waiting to produce power. I have been all over the place with how to put power into our house. I have gone from batteries with grid tie to squirrel cage motors.
Ken from you experience would you say its easier and more efficient to generate a straight 240v and feed it into my supply isolating it from the grid with an auto switch over relay so it switches automatically when the gen set is off or out of fuel. Or use a grid tie inverter with a ST type alternator.
We are now paying approx £100 per month on electric.  This is for a large farm house stables security lights etc so we are not the norm.
Our daytime usage is very low 100-200 watts but our night time units are approx 800- 900watts and this is when I would look at running it.

The other bit I am contemplating is what size to make the alternator do I go for on that produces just enough or one that’s good enough for about 2-3kw and only use about ½ the capacity.

I work at home so looking after it is not a problem.

Comments welcome.