Postings to the Navitron Forum

The following updates we posted to the
Navitron Renewable Energy Forum during the Winter of
2006/2007.  I have reproduced them here as they contain snippets of day to day measurements and
facts recorded during the experimental phase, which would otherwise be forgotten if not retained

November 28th 2006


It's been a good few days progress with the Lister Gen.

I now have managed to get the 5kW pure sine wave inverter to make pure sinusoidal, 50.00Hz,
237Vac power.

This is a major milestone in the project, and one more tentative step to my going off-grid, with
waste veg oil powered combined heat and power.

The inverter is a 2nd hand 5kW emergency lighting unit - dating from about 1991.  It's about the
size of a single wardrobe, and has 2 shelves to take the storage batteries.  I saw it on Ebay a year
ago, it didn't sell and the vendor contacted me to say that it was still available, so I trawled over to
South Wales to pick it up.  My heart sank slightly when I saw the size of it, but it seemed such a
bargain,  so I said to myself that if it fits in my Peugeot 406 estate - I'll take it!

It fitted just, with the driver's seat right far forwards, and with no rear vision, it was an
uncomfortable drive back to London along the M4.

The problem with the inverter was silly really - I should of persevered in September when I first
tried to fire it up.  It has an undervoltage lockout, and so the battery voltage needs to exceed a
certain threshold point, before it shows any signs of life at all.   I just wasn't reaching that voltage.

So freshly inspired, I connected it across my 96V battery pack  (Its really designed for 108V) and
increased the speed of the Lister until at about 118V, the inverter sprang into life.

I flipped the breakers and soon was boiling a kettle on one of pair of  2.5kW inverter modules.

I scoped the waveform with my portable scope, and it was a lovely 237V ac 50.00Hz sinewave, even
whilst boiling the kettle.  - see attached.

This project has been a labour of love, and great fun when things work out well.

I am now going to invest in some plywood to extend and patch up the old shed, and dig the trench
to take the heating pipes back to the house.

Whilst the Lister engine was £250, and the inverter and batteries £385,  it's the little things from
the plumber's and builders merchants that seem to add up.

The new exhaust heat exchanger is performing well, and today I measured 3.6kW of heat from the
exhaust exchanger alone ( 58 litres of water per hour with a 53.5 C temperature rise).  I now need
to make some plumbing modifications so that I can also use the coolant heat.

More of this on the Lister CS Owners group on Yahoo

December 2nd 2006


A couple more hours of running today at 325rpm, produced some favourable fuel consumption

Electric power output  880W    14A at 62.5V  dc

Fuel consumption  450ml per hour

Electrical Efficiency   = 0.88/( 0.45 x 9.4)  = 20.8%    (1 litre of rapeseed oil is 9.4kWh)

Heat output = 24 litres per hour at 40C rise  = 1.117 kWh

Thus a gallon of veg oil, (costing £2.43 at a supermarket),   will provide 10 hours running and
8.8kWh of electricity  and 11kWh of heat.

January 19th 2007

I will also be using 22mm "polyplumb"  barrier pipe, but fitted with 19mm wall thickness
insulation - bought from Wickes at around £1.22 per metre. This all helps to keep the cost down
for the 12 metre run to the engine shed.

I have settled on the 19mm wall thickness, because it allows the insulated pipe to be run inside a
standard 68mm plastic black pvc drainpipe - a really neat fit.    The resulting flow and return pipe
assemblies will be buried in a trench with 110mm waste pipe - to be used a general purpose
conduit for other services, electric cables, engine/inverter control cable, telephone,  15mm gas
pipe etc.

The trench will be further insulated with polystyrene or celotex sheets and a wrapping of
bubblewrap should keep the cold wet soil from contacting the heat pipes.

The polypipe will be in a continuous straight run with no buried joints.   I have seen temperatures
of 85 C from the outlet of the exhaust heat exchanger - but this is working with a relatively low
flow rate of 1 litre per second.  At higher flow rates, it should be easy to maintain the temperature
within the safe limits of the polypipe.

January 24th 2007

As many, I awoke to a snowy morning today.

Temperatures last night got down to minus 2C and I had to wait until lunchtime before I could go
out and start the Lister engine.

It's been running a couple of hours now in what I call "Stealth Mode", which is basically 325 rpm
or half normal speed.

Right now its developing about 750 watts of dc which is recharging my inverter battery, and a
useful 1.2kW of waste heat  circulating from the exhaust heat exchanger.

It's running at around quarter of its rated output, which means a lot less noise and a lot less fuel
consumption.  A gallon of veg oil lasts about 10 hours when run like this.

To me this seems the ideal set up to complement a small wind turbine, or to replace a wind
turbine in wind-less areas.   

The coolant water from the exhaust heat exchanger is at the ideal temperature for underfloor
heating, and it is my intention to make use of this when I build the conservatory in the Spring.

I discovered that concrete makes a good thermal store, with 1.94MJ/m3/K of useful heat storage.
The 4m3 of floor slab under the conservatory will become a 15kWh store if kept around 30 C.

January 25th 2007


Further to yesterday's post:

Many of you will know that I an enthusiastically exploring the lower rev range of my old 1951
Lister CS 6/1 with the intention of setting it up as a "Suburban Acceptable" combined heat and
power system.

The main reasons for slow speed running are:

1. Less noise and vibration
2. Reduced engine wear
3. Heat and power output are closer matched to my domestic requirements.
4. Veg oil burns more efficiently if given twice the burn-time in the cylinder.

I recently found a new oil supplier:-  my local pub has changed hands, and the new landlady is very
supportive of my cause.  I came away yesterday with about 30 litres of good quality, used vegetable
oil.  Catering veg-oil is intended to be changed once a week, otherwise it oxidises and taints the

Temperatures yesterday hovered around freezing, so the waste oil was thick and cloudy.  I poured
most of the oil into the filter barrel, which my friend Tim  produced for me last summer.

I have managed to filter off about 7 litres of good oil, but the near freezing temperatures are
making the filtering process very slow.  To help warm the oil, I have submerged a 100W bulb into
the oil, and running it off a 60V supply, so it's running at a very much reduced wattage.

I brought a 3 litre container of oil indoors yesterday evening, and after 12 hours at room
temperature the oil had cleared to a golden amber colour, with no trace of cloudiness.

The engine is running at a near constant 325 rpm, and charging my inverter battery through the
PMDC generator - that I also use as a starter motor.   So good it is at starting - that I can readily
start the engine first thing in the morning - even at freezing point.

Once again today, the  engine is producing about 750W of dc from the generator, and from the
measurements on the exhaust heat exchanger, about 1.1KW is available.   There is about a 28 C
temperature increase across the heat exchanger with a 36 litre per hour flow rate.

The hot water from the exhaust heat exchanger is currently being circulated through my domestic
hot water cylinder - about 120 litres.

I have not yet tapped into the coolant water, but hope to use a coil of  copper tubing, set into a local
small cylinder, into which the Lister thermosyphons its coolant.  This means that the Lister
always has about 30 litres of local coolant - and can run for several hours before you need be
concerned about removing the heat from this tank.

After 3 hours of running, the engine had consumed  1145 grammes of veg oil - about 1.275 litres.

At half rpm "Stealth Mode"  I allow 400 to 500ml per hour fuel consumption.  At 650 rpm, allow
1200 to 1500 ml per hour.  Veg oil has about 90% of the calorific value of diesel fuel, and also fuel
efficiency can be increased if the oil can be heated - in particular before the injector. This
improves the spray form the injector, so the fuel burns better on the power stroke.

From my experimentation so far, veg oil can be converted to electricity with an efficiency of
slightly better than 20%.  At slow speed I have observed that 33% of the fuel energy can be
recovered from the exhaust gas heat exchanger.

I am continuing to run the engine on this newly filtered oil, in the hope of getting some  accurate
fuel consumption figures over many hours of running.

My "engine shed" has now become cluttered with all sorts of Lister paraphanalia, and I am
waiting for better weather to cast a better engine mount in concrete, and additionally, extend the
shed to give me a little more clearance around the engine so that I can fit the acoustic enclosure,
heated fuel tank and coolant heat recovery systems.

These initial trials have convinced me that the engine can be run for extended periods of time at
slow speed and still achieve a fuel to electricity conversion of better than 20%.

The acoustic enclosure will allow me to run the engine at full output when required, and further
increase the usefulness of the system.

For anyone who has a modest electricity consumption, and the space to locate an engine shed
within 12m of the house, I recommend the Lister route.  These engines are bombproof and if
anything breaks, it's easy to fix. This is 1930's technology, updated for use int e 21st Century and to
make better use of waste vegetable oil as a renewable fuel.

For an investment of under £2000, you can set up an engine, generator, inverter and battery bank.  
If you sweet-talk your local Landlord/landlady you can probably secure a free fuel supply.

A brief breakdown of costs:

Lister Engine £250
Emergency Lighting unit plus batteries (5KW sinewave inverter)   £375
3KW alternator  £250
Exhaust heat exchanger £350
Pulleys and belts £125
Common sense and enthusiasm - priceless

Details of my project are on my website


Reply From Sutty - Jan 25th


I have read with interest the thread thus far, particularly because I'm looking at what heating
system to install in our garage conversion (hopefully in the next six months...maybe - planning,
building regs, etc, moon and planets aligning, etc - here's hoping!) which will only be occupied
initially for ~6 months/year.

Firstly, I'm thinking of insulating it to death - I'd rather spend more money up front on one off
costs (which I'd be more than loathe to look at again) preventing losses than figure out the most
efficient way of heating a leaking sieve. The next step I see at the minute is to use a
water/saline/glycol underfloor heating as this is the most flexible option to integrate other
systems with. But then the options come flowing in, solar thermal, ... combined with GSHP or
CHP or ... etc. This is where my current questions lie... [and at times where my wallet groans...]

With veg oil based CHP, the worry I have over using veg oil is twofold. First it's great to use an
energy source which is 1. free, and 2. renewable, but I worry over the big picture of where the veg
oil is grown... is this displacing set-aside land (which from what I can gather fixes more CO2 than
bringing the land into "productive use" and generating a useable crop [veg oil]) or even worse is
the generation of biofuel (as a total pool - which I would be contributing to) be coming from
felling virgin rainforest in other parts of the world (Thailand, Malaysia, Borneo etc.) and then
importing the oils from there into this country... ?

As someone whose main goal in the conversion is in trying to "do the right thing" (whilst making
sure it doesn't kill the wallet) it's difficult to try and figure out the "best" way to go...?? ...
particularly with such conflicting information available.

In addition to the above, I'd be interested to hear your thoughts of bio-"diesel" (in this instance
veg oil)  and the levels of NOx they produce relative to mineral diesel.  Also, whether you have
seen any difference in maintenance (from what I read the lubricating oil needs changing more
regularly than normal mineral diesel or you end up with corrosive wear, [seen on bearings etc.]
oil viscosity increase [and therefore fuel efficiency penalty], and also deposits on the injectors and
pistons/rings [poor combustion, oil consumption, poor exhaust emissions])

Looking at your website, (thanks for the link, - it's great to see someone experimenting and
showing what can be done) there is loads of info available for me to digest on options to try for and
ponder for my conversion. But as ever, being a novice at this I'm sitting here with more questions
than answers, wondering if you combined your Lister engine with a GSHP whether you would be
able to see greater thermodynamic efficiency, and wonder what kind of controllers are needed to
ensure optimum output... (if it could be achieved) your experience (or others) would be welcomed.

Thanks for the info in your posting - it all helps to add more info into the decision of which way to

Reply from Ivan  - Jan 25th

Another wealth of information! It's like experimentation without having to leave my computer!
Have you measured the temperature increase in the water tank over the experiment? If you have
20% of the energy in the electricity, 30% in the exhaust, if you worked out the transfer to water,
you would have a good estimate of the total efficiency of the unit. I assume around 30% - which
would make the overall CHP efficiency 80% - not bad at all for a DIY setup using old 1930s engine
technology. Ken has definitely been my inspiration to get on and complete a project that I have
never got round to starting!

I am keen on the stealth mode - for slightly different reasons. As the majority of the energy
produced by the engine is heat (80%), by running the engine slower, it allows more time to extract
heat from the exhaust gases, as they are moving slower. I can't remember the figures, but you did
tell us the exhaust temperature at 1kW load and 2kW load, and the later was significantly higher ie
water jacket had less time to absorb heat.  

Incidentally, for my engine, I ordered a 72 and a 44 tooth engine pulley and a 56tooth generator
pulley. The generator is designed to run at 400rpm, so this allows me to use 325rpm and 500rpm
(more or less). As the wind turbine alternator has a tapered shaft, I will have to find someone that
can centre and fix the 56tooth pulley onto the taper-shaft alternator hub. It's a bit messy, but at the
moment, it seems the easiest option. I hope this is technically simple for someone with a metal
lathe, but I am not holding my breath!

I did not realise the significance of the oil temperature on engine efficiency. Any idea of the kind of
loss you would expect with cold veg oil? I was thinking about current weather conditions and the
cloudiness of the fuel - it might be prudent to heat the Lister fuel tank - this would give it a boost
(maybe make up a fuel tank inside the water tank?! Or a loop of copper pipe from the exhaust heat
exchanger into the tank?). Any idea of the optimum temperature for the veg oil?

Is the new supplier able to provide 30litres per week?! That means you can run your setup for
10hours per day, 6days of the week (With a day off on Sundays!)

Sutty, I would not worry too hard about the ethics. The use of a free waste product in no way
enhances the industry that generates it. If you pay for your veg oil, then it is a fair point to consider
what you are supporting, but if it is scrounged, the only thing you are doing is preventing the fuel
being wasted or disposed of in a method that pollutes the environment. Recovering energy from
waste is one of the most productive things you could do.


Jan 25th

Ivan, Sutty,

Thanks for you points and observations.  Here's a few quick answers:

1. Insulate to death - sounds like a good plan.  Insulation will give you the best bang per buck.

Its made in the UK, because its not cost effective to bring in form China, and with more than
adequate insulation in your home, you might just be approaching the levels of insulation our
norther European chums have enjoyed for 30 years.   

If you can plug your leaking sieve - you won't need to chuck as many BTUs at it to keep warm.

2.  I burn rapeseed oil in my Lister engine which is grown in Northern Europe (UK, Belgium,
I also do not advocate displacing persons nor populations in the move to grow energy crops (palm
oil)  in the Tropics.

3. British farmers and landowners should be encouraged to move towards growing energy crops
and should be incentivised for doing so.  Apart  from leaving ample field borders, woodlands and
hedgerows to encourage wildlife, the scandalous "set aside" land should be ploughed over and put
to task with growing "carbon (dioxide) reduction crops".

4.  Rather than  bringing in back door legislation that discourages the use of vegetable oil as a
renewable fuel, the UK Government should  find a way of incentivising biofuels and forming a new
world class biofuel industry.  From farm to fuel pump, the government should encourage
innovation and the potential for a growth industry.

If they really want to reduce emissions by 50% by 2050, the should stop talking hot-air and start
acting now.  Personally I think that if they cannot meet the 20% by 2020 - they don't stand a chance
of meeting the 2050 figures.

IMHO, only the Germans with their 100,000 solar roof scheme and widescale wind projects stand
a chance of 20% reductions of CO2 ( and no further need to invest in nuclear) by 2020.  
"Deutschland, Deutschland Ober Alles....."

5.  Three years ago I stumbled across a charcoal production method that would allow the UK to
produce all its own charcoal, without having to import 60,000 tonnes from Indonesia.  By
reducing the average burn time from 24 hours to just 4 hours  it increased the yield significantly
and would allow charcoal burners to make an honest living from woodland management in the UK.

6. Forget the NOx, it's the reduction in sulphur dioxide, and the lowering of the carbon footprint
that is the main reason for moving to veg oil based fuels.

7. Ivan, my 20.5% efficiency is with cold veg oil.  This will increase to around 24% if the veg oil is
pre-heated before injection.

If in doubt, get an engine and start experimenting.....


Jan 25th

Hi Guys,

"Every Therm is Sacred...."   (With apologies to Eric Idle).

Whilst running the Lister CHP system, it has become very apparent, especially in this cold
weather, the importance of getting every drop of heat out of the system, and secondly, making sure
that you have heat and power available when needed.

Having spent my first 18 months of Listering, swinging a hand crank, (often with self-harming
mishaps), I quickly realised the requirement for an effective starter motor, with the accompanying
starter battery.  With a storage battery at hand, everything becomes a lot simpler.

The 6KW permanent magnet dc motor seemed the ideal choice, especially because it would
cold-crank the engine over with as little as 24V. Having the 96V inverter battery at hand, much
simplified the starting process, and in cold weather I use the 48V tap off the battery to crank the
engine until it starts.

This process is aided by the propane blowtorch, which is permanently fixed sothat it plays over the
last few inches of high pressure line, just before the injector.  Starting is simple, light the
blowtorch, wait 30 seconds and then turn on the 48V to the starter motor -ensuring that the
exhaust valve lifter is in the decompress position. After cold cranking a few dozen turns, drop the
lifter and wait until the engine starts. This might take an additional 30 seconds - bit it will fire
eventually  - even with ambient temperatures on freezing.

As soon as it fires, the voltage on the output terminals of the starter motor will start to rise above
the nominal 48 V battery voltage. Once it reaches 60V, lock off the rack control lever, and turn off
the propane torch.

The engine will now run at 325 rpm until doomsday (and beyond).

With the engine producing 60V, the inverter can now be fooled into starting-up, and within
minutes of commencing, we now have a source of 50Hz, 237V rms sinusoidal power, and a source
of hot water.

Heat storage and electricity storage are paramount with a system like this.  Hand cranking a
Lister on cold veg oil, with snow lying around the engine shed, would finish most people off.   I am
still to evaluate fitting an automotive glowplug in place of the compression change over valve, to
improve cold starting on veg oil.

There is no dispute that heating up the veg oil is going to make things more efficient. I have got
away until now with a very simple system, without preheating the oil.  However, even a few turns
of fuel line around the hot exhaust is going to improve the fuel economy and give the fuel pump an
easier life.

Once you have got the engine running, there is no shortage of useful heat available in the coolant
and the exhaust, to do the chores of oil preheating,  fuel tank warming etc. Veg-Oil flows so much
better when its warmed up a little, and if you can get it up to 100or 120 degrees C, it will go
through the injector like the best diesel fuel.

With the weather so cold, I have chosen to place a 100W light bulb in the filter barrel, to warm the
oil up and aid the filtration process.  Running on the 96V inverter battery, this bulb will only
produce about 20W of heat, and early tests show that it can keep the contents of the filter barrel
about 14 C above freezing.

Like the old joke.. If it gets really cold, I will turn the bulb on  ;-)

Local storage of heat next to the Lister is generally a good thing. If you can afford an insulated
tank of 100 litres or so, it will keep the block warm overnight, and make starting much easier on
frosty mornings.

The next phase of the project is to build a better enclosure around the engine.  This will be an 8
foot cube, basically a packing case, double skinned and insulated, so that little of the waste engine
heat is lost.  This temporary building will be exempt UK planning regulations, and give me a lot
more room for my CHP system.

It will also allow me to fit my plywood acoustic enclosure around the engine and generator. This
will attenuate the clickety-clack noise of the valve gear, and allow me to run the Lister at full
output, without getting an ASBO.

The heat output from the engine is best suited to provide heat for my underfloor heating system.  
This can work on water temperatures of 50C, and the current kitchen and bathroom system will
happily absorb 1500W of heat - ideally suited to the Lister running in stealth mode.  In the spring,
the new conservatory, will provide another underfloor loop, which will handle the rest of the
waste heat available. Any additional heat can be stored as hot water in a more conventional
thermal store.

As you can see, this is a continually evolving project, worked on as and when, time allows.  With
most of the system components bought 2nd hand from Ebay, it's quite a challenge getting it all to
work together.

As with any renewable energy engineering project, there is plenty of scope for experimentation.

Running an engine on filtered waste vegetable oil is one thing,  turning it into a reliable system that
provides domestic heat and good quality 50Hz sinusoidal power is another matter.

This page looks at some of the key aspects of putting a reliable system together and some of the
experimental work conducted along the way. It also provides a record of some of the musings and
thought processes that occur along the way.

Without resorting to running the Lister engine 24 hours per day, the available heat output will not be
sufficient to fully meet the heat demands of a typical household.

It is therefore strongly advised that the Lister CHP system is used in conjunction with an additional
source of domestic heating, with wood fired heating being the preferred option for low environmental

In my proposed set-up, the Lister contributes to the heating in conjunction with a wood fired boiler
and a solar water heating panel. A large heatstore in the workshop allows these systems to contribute
to the overall heating.  A conventional, high efficiency condensing gas boiler provides a normal
domestic heating system when the renewable system is offline.

All of the renewable systems are contained in a large insulated workshop, located about 9m from the
house.  The renewable CHPsystem is connected to the house by an insulated "heat main" and an
electrical power cable.   This allows easy isolation when maintenance is required and minimum
intervention into "normal" existing household systems.
The Practicalities of Slow Speed Diesels Running on WVO.

With any renewable power system, including solar pV, solar water heating and wind power, the key to
success is being able to store energy when it is available and use it when you need it.

The second design challenge is being able to match the size of the system to suit the varying
requirements of the household, both in terms of heat and power.

The advantage of the renewable veg oil fuelled generator is that you can run it when you chose, rather
than be at the mercy of the weather, as is the case of solar or wind systems.  You can also vary the
length of run, and to some extent the power output, to suit the household  energy requirements.

The 6hp Lister can produce a maximum of approximately 3kW of electricity when coupled to a ST 3
alternator. In addition to the power, there is approximately 5kW of waste heat available for recovery
from the coolant and the exhaust using the exhaust gas heat exchanger.

Recent experiments at running the Lister at slower speeds in what I call "Stealth Mode" have shown
that it can be run at much reduced output when full power is not needed, with the accompanying
reduction in fuel consumption.

At full output the Lister engine will consume a maximum of 1.5 litres of veg oil per hour, dropping to
about 0.5 litres when run at one third output.

Fortunately, the typical household does not often need 3kW, only when appliances such as washing
machine, dishwasher and kettle are used. Consequently,  the daytime load is often below 400W, and
the evening load being below 600W (TV and extra lighting). During the sleeping hours the household
load drops to below 100W.

To cater for the widely varying electrical load, the Lister generator system makes use of storage
batteries and an inverter, allowing the engine to be run at varying times and power outputs during the
day, and run the household from the batteries at night.

Electricity has been stored in lead acid batteries for over 150 years and storage batteries are now a  
mature technology.  Modern power electronics allow cost effective high power inverters and battery
chargers, and the boom in large computer and telecom installations in the late 1990's has meant that
many second hand UPS and battery systems are now available cheaply on the secondhand or salvage

Storing heat for later use can be done with nothing more elaborate than a large insulated tank of
water, and the intention is to have a 250 litre store to accompany the Lister.  If this can be heated up
to around 95C, it will contain about 22kWh of heat, compared to the same mass of water at room

If we think in terms of the Lister as an energy conversion device, and not just a generator, there then
exists the possibility of using it purely to convert the waste vegetable oil into usable heat.  Although it
might sound counter-intuitive, the full electrical output of the engine could be directed into an
immersion heater within the heat store tank, or to an electric storage heater located in the house, to
provide localised heating where required and at the time of day it is needed .

This would allow almost all of the energy in the vegetable oil to be converted to heat, at times when
the electrical output of the generator was otherwise not needed.
Typical Domestic Demands.

The heat requirement of a typical home varies from day to day,  month to month and year to year.

The Winter heating season of 2006/2007 has been particularly mild,  with only 9875 kWh of heat being
used between 1st November and 31st March.  The previous winter for the same 150 day period, the
heating requirement was 13432kWh - an increase of nearly 24kWh per day

Daily variations range from  30.5kWh on November 15th, to 136kWh on December 21st.

This creates a problem in deciding how best to run the Lister CHP system. Clearly it has to have a
flexible operating regime that allows it to best contribute to the variations in demand.

During the months of September, October and April, there is a small contribution to hot water from
the solar water heating system. The Lister CHP, whilst generally not needed for heating during these
months, can be utilised to provide a top-up to the hot water.

On very cold days, the heat requirement of this property can double from an average of 65kWh to about
130kWh, dropping to as low as 30 to 45kWh on warm days.

The table below shows the measured heat demand for winter 2006/07.

Month                        Heat Consumption kWh                Average Daily Demand kWh        Fuel Needed / l

Sept 06                        87                                                          2.9                                                    0.31
Oct 06                         601                                                        19.4                                                  2.1
Nov 06                        1486                                                      49.5                                                  5.26
Dec 06                        2713                                                      87.5                                                  9.31     
Jan 07                        2173                                                      70.0                                                  7.44     
Feb 07                        2027                                                      72.4                                                  7.70      
Mar 07                       1963                                                      63.3                                                  6.73

WVO fuel consumptions are based on an average calorific value of 9.4kWh/litre

For the 6 months, Oct to March,  approximately 1200 litres of WVO would be needed for full
replacement of natural gas heating system. With bulk WVO available at 30p/litre, the heating bill
would be around £360.

Running the engine in this manner, as a heat source, would require quite long hours at full output,
particularly during December.  For this reason it is likely to be better to reduce the heat contribution
from the engine, and use a wood burning boiler to provide much of the evening heat.
It is clear from the above figures that the running regime of the CHP, varies widely from month to
month.  With 5kW of recoverable heat available from the system, it might run for just an hour per day
in September, up to 18 hours per day on an average December day. On the coldest of days when
130kWh are needed, the heat output alone would not satisfy the demand.

Fortunately, with the use of heat storage, it is possible to smooth out some of the peaks.

3 storage methods are being considered.

1. 250 litre thermal store holding about 22kWh in the form of hot water.
2. Kitchen, bathroom and conservatory underfloor heating slab, storing 37.5kWh
3. Electric storage heaters - storing 12kWh and 24kWh respectively

In total,  about 83.5kWh of thermal storage available.

The thermal store would require 5 hours running to fully heat it.
The underfloor heating slab would need 8 hours to fully heat it
The storage heater would need 8 hours of electrical output to charge it.

It would seem sensible therefore,  to connect the thermal store in series with the underfloor heating
loop, such that the return water is at its coolest, about 30C when leaving the underfloor heating loop.

The engine could be run for 8 hours per day at full output (5kW heat + 3kW electricity) to recharge the
heat storage systems, and then at a reduced power output for the remainder of the day for inverter
battery charging.  Fuel consumption under this regime would be about 12 litres per day.
How the White Knight came in from the cold, to fight the Evil Bosch for the attention of Lady Amberlec - and
lost, causing her to trip out.

A cautionary tale about the perils of overloading and inverter and dragging old appliances in from the garden.

It sounds the stuff of legends, but far from it, it's just another normal day in the Renewable Energy Workshop.

Let me embellish the tale somewhat....

Some two years ago, when there was much building work in progress in the kitchen department here at Monson Road,  I
swore that as part of my reign of terror on inefficient domestic appliances, I would not have high wattage devices in the
house - so the White Knight tumble dryer, rated at 2200W was banished to the garden where he lived in the gap between
the shed and the neighbour's fence, with only a Yew tree for shelter. No longer would grid supplied kilowatt hours be
wasted on such a frivolous appliance. From thenceforth, it was decreed that clothes be dried naturally during fair weather.

And so it came to pass, that a mighty new workshop was built, and in the corner sat Lady Amberlec, the 5kW sinewave
inverter, in her high tower, with all her army of 36 foot soldiers at her feet - each and every one of them a Hawker, Fakir
or some other such derogatory term for the lowest of low, base metal batteries. However between them they had
formidable strength and capacity, which they could summon upon in a flash, and give Lady Amberlec her legendary but
pure sinusoidal power.

Lurking in the shed next door, was the Extraordinary Mister Lister, a venerable old geezer of immense and reliable
energy, which he derived from his daily diet of nothing more than waste vegetable oil.  Why he would soon whip up
enough gruel to keep those Hawkers in fighting condition and remain loyal to the stately Lady Amberlec.

And so for three long weeks, Mister Lister, the Hawkers and Lady Amberlec supplied their combined efforts to the
household of King Ken, and he went about his business, and did not tax his subjects too dearly.  A few hundred watts here
and there - not much more.

Then in an act of rash boldness, he entered into a deal with the Evil Bosch, a power crazed Tutonic appliance that lurked in
a cupboard in the kitchen.  

He would divert some of his energy revenue to the Evil Bosch, in exchange for mundane dishwashing duties.

And so for several days, everyone had to work much harder, to keep the Evil Bosch in his position of chief bottlewasher -
a kind of Orwellian Kitchen Plongeur.

Then after many fair days, the rains came, and it was time for the laundry to be done - for King Ken was running short of
robes.  And so Aquarius,  the clothes washer was summoned, and given a full load.  And so for two happy hours Aquarius
and the Evil Bosch shared their duties in the kitchen and shared the favours of Lady Amberlec.  Aquarius was the first to
finish his chores, and so King Ken came down to put the clothes out for natural drying - but alas the weather was not fair,
it was pecking fissing down.

So Ken hatched a plan, to forgive the White Knight and bring him back from his exile in the garden for now there was an
excess of vegetable power courtesy of Mister Lister, and set him to work to dry the clothes, for they were quite damp.
And so the White Knight was carried back into the workshop , and sat upon the bench, where he was given a good wipe
down and a general cleaning. And so the clothes were stuffed in, for him to provide his drying services.

All went well, and Ken returned to his office to continue with his daily business, and upon glancing on the Electrisave, to
his horror it was reading 4.92kW. But alas, he had only wired up half of Lady Amberlec, just 2.5kW, and so she was
struggling with a 100% overload - it was at that point that the lights went out, and the laptop beeped to say that it had lost
its mains supply.

So Ken rushed out to the shed to save Lady Amberlec, and on his way he realised that the Evil Bosch had probably not
completed his dishwashing duties in the allotted time.

The White Knight had been dueling with the Evil Bosch for the favours of Lady Amberlec, and it had all been a bit too
much for her, she had overheated and tripped out.

So fortunately when Ken rushed to see if Lady Amberlec was all right in her tower, it was just a mild swoon, and with a
flick of the reset switch - she was back and running again, and as for the White Knight, he too was not his old self, for his
heater element had tripped out and he was refusing to dry the clothes, but just churn them around in cold air.

So the temperamental White Knight will probably get banished again, to his position under the Yew tree, Lady Amberlec
will have her second 2.5kW inverter stage properly installed, and Ken won't be so daft as to try and get all his subjects to
work so hard at the same time.

As I said just a normal day at the Renewable Energy Workshop.

                                                     Principal Players

Lady Amberlec                 1991 Menvier Amberlec 110V dc 5kW Emergency lighting unit.
The White Knight             1996 White Knight tumble dryer - somewhat internally traumatised
The Evil Bosch                 2005 Bosch Dishwasher
Aquarius                            2000 Hotpoint Aquarius washing machine
Mister Lister                    1951 Lister CS 6/1 single cylinder diesel engine generator
Electrisave                        A 433 MHz whole house energy meter
The Hawkers                     36 Hawker SBS 40 gel storage batteries arranged as 4 parallel strings of 9 batteries

To be continued.....