How to do an energy audit.......

[Martin CC O'Beirne]

Hello folks - I'm 'noodling out 'what I need for a change from living as a ccer on my own to a ccer with a boat that will have up to 4 people (1 baby) and one 10 year old part time. - I'm getting my 45ft boat extended to 58ft.

 

My 3 way fridge has come to the end of its life

 

A washing machine would be good

 

I'm not familiar with the maths I need to do to work out what my system can cope with and accordingly what else I need

 

What I have

 

3 80 watt solar panels

3 105ah leisure batteries

A small alternator (I cant remember its output, its for a 3 pot sole diesel, I just remember someone who saw the boat commenting that it didn't have a great output)

A small inverter (too small)

 

I have LED lights, a pump for the radiator, gas cooker, obvs water pump for shower, occasionally watch a film on an LED TV, and a laptop.

 

My MPPT controller can have 1 more solar panel at 80watts

I think I can make room for 1 more leisure battery.

 

 

A generator and compressor fridge is too expensive.

 

So what Id like to be possible - is a conventional in house sized fridge & washing machine, new energy efficient. A new Inverter (2kw big enough?) - If required a 4th leisure battery and solar panel.

 

Is there an idiots guide to working this stuff out, so I can really sus what I need/what's possible?

 

Thanks

 

Martin

 

 

[nb Innisfree]

Hello folks - I'm 'noodling out 'what I need for a change from living as a ccer on my own to a ccer with a boat that will have up to 4 people (1 baby) and one 10 year old part time. - I'm getting my 45ft boat extended to 58ft.

 

My 3 way fridge has come to the end of its life

 

A washing machine would be good

 

I'm not familiar with the maths I need to do to work out what my system can cope with and accordingly what else I need

 

What I have

 

3 80 watt solar panels

3 105ah leisure batteries

A small alternator (I cant remember its output, its for a 3 pot sole diesel, I just remember someone who saw the boat commenting that it didn't have a great output)

A small inverter (too small)

 

I have LED lights, a pump for the radiator, gas cooker, obvs water pump for shower, occasionally watch a film on an LED TV, and a laptop.

 

My MPPT controller can have 1 more solar panel at 80watts

I think I can make room for 1 more leisure battery.

 

 

A generator and compressor fridge is too expensive.

 

So what Id like to be possible - is a conventional in house sized fridge & washing machine, new energy efficient. A new Inverter (2kw big enough?) - If required a 4th leisure battery and solar panel.

 

Is there an idiots guide to working this stuff out, so I can really sus what I need/what's possible?

 

Thanks

 

Martin

 

 

FWIW I designed and fitted out our boat to cope with full time liveaboard ccing and finished up with 8 leisure batts, a large alternator, 3kva Victron Multiplus and a Kipor inverter Gennys for weekly extended absorption charges. 5 years off grid and it all worked out fine. I wouldn't like to go below 4 leisure batts if financially pushed, 8 batts gives a good power margin. Victron and alternator has proved to be very handy for coping with auto washing machine and various 240v appliances. Edited May 2, 2015 by nb Innisfree

[Jambo]

That's quite a change in energy demand! When you're doing your calculations you need to bear in mind that usage of everything is going to go up substantially so any calculations you might have done of your own consumption won't be valid any more.

 

I expect you'll need to size your inverter to the washing machine's max power draw (plus some reserve) if that's going to be your peak load. The washing machine's specs might possibly tell you that but otherwise you'll need to check out the plate to see what it could potentially draw. I think the washing machine which we have (but don't use now) draws about 2kW peak.

 

Bear in mind that washing machines are quite water hungry so you should also consider how it'll affect your water supply. You're going from one person's usage to 4 persons plus a washing machine. How long will your tank last? You might want 2 weeks worth of water so you can stay the maximum time in one place without having to move for water.

 

Have you looked at twin tub machines? I believe they're much more efficient for water and energy use and they have much lower peak loads than conventional washers.

 

Fridge-wise can you go for one without any freezer compartment or would absence of ice cream be a deal breaker? If you can go without then it'll make a big difference to your demand. I would suggest looking for an A++ fridge. A+++ fridges are available but are considerably more expensive. A larder fridge (without ice box) will use about half what a fridge with an ice box will use.

 

To find the most efficient 230V appliances check out http://www.sust-it.net .

 

I would suggest upping your solar installation as far as you can would be a good idea, even going beyond your current maximum of 320Wp if you can although that would mean replacing your controller. It won't help you in the winter obviously but from April to October it will make a heck of a difference and pays for itself pretty quickly.

[OldGoat]

You've got a big challenge -

Your three pot engine is probably a bit small to fit a large alternator - and that's what's needed (unless of course you don't mind it being a bit gutless when cruising and charging at the same time). Your boat will be will be underpowered because of the lengthening. I assume the engine is vetus / beta / ? type and not a big old Lister type.

 

translating 'normal' house lifestyle to a boating environment doesn't work well unless you either scale down your expectations or upgrade your power generation capabilities - and that's what folks on here don't do, especially as you infer you don't want to spend much money.

The fridge is a killer - but you do need a reasonable sized unit for a family.

[Arthur Brown]

http://www.victronenergy.com/upload/documents/Book-EN-EnergyUnlimited.pdf

 

is a great book and will tell all you need to know about power or energy audits.

 

IMO you are asking the impossible unless you do a LOT of cruising or live on a shore supply. Electrical economy is one of the first things people work out on a boat, and fridges are one of the big users.

[Martin CC O'Beirne]

 

Nbinnisfree - that is a beefy system, ive noticed more generators on the market recently, prices coming down significantly. Maybe the door isn't completely closed for one, id just be concerned that a bad gen would be a frustrating experience - Hyundais might be ok, but how well do they compare to the ever reliable Hondas (that are too expensive)

 

Thanks Jambo - great advice re larder fridge and website - the very top efficiency rated larder fridge is just affordable

full domestic size, 240v rated at A+++

 

http://www.liebherr.com/HG/en-GB/region-UK/products_hg.wfw/id-1555088-0_46573-0

 

Energy consumption in 24 h* [kWh / 24h] = 0.169

 

Thanks old goat, its not a big old torquey lister I'm afraid - its a marinised Mitsubishi, sole diesel, about 25hp, I hope it will still push the boat reasonably well on the canals. not planning any river work.

 

Arthur Brown thanks! will work my way through that book

 

I don't know what 0.169 means in context!

[Paul C]

You need to decide whether do get a genny, or get a suitably-large inverter to run the washing machine as a first decision. Whilst the washing machine won't be massively expensive, I fear the inverter to run it off batteries might be.

 

Once you've decided if you're going down "expensive inverter" route, that will sway whether to get a 12V fridge or 230V fridge.

 

Then once you've specified and nominally chosen those three components, you have an idea of the lion's share of the additional power consuming items over & above what you currently have.

 

Then you can think about how you'll charge the batteries, and how often, which will give you the size of alternator, or solar panel(s), and/or battery charger (if generator route chosen). Once you know how often you'll charge, then this will point towards the size of battery bank required to reliably supply the power in between charging sessions. For example you might choose to run the engine or generator every day; or every other day; or twice a week etc.

Travelpower is also an option if you don't want to have the hassle of a separate genny and storing/buying petrol etc.

[Jambo]

I've got that Liebherr (or at least a near identical model with the same consumption). It's very good.

 

Its electricity consumption is 0.169kWh (kilowatt hours) per day. If that comes from a 12V battery system it means around 14Ah (amp hours):

 

0.169kWh = 169Wh

 

169Wh / 12V = 14Ah

 

But on top of that 14Ah there'll be some energy used by the inverter so it would probably end up being more like 16Ah or thereabouts.

[Arthur Brown]

Everything depends on your cruising pattern. If you cruise daily for five hours, you will have all the electricity you want while cruising and full batteries. If you cruise once a month to the water tap/pump out then you will need a generator and another 500w of solar.

 

Do please review how you can maximise the electricity from your main engine. You could use the biggest alternator that will fit, or you could find one that uses the small surplus of available power after propulsion and fit an alternator boosting device for times when you are moored but want peak available charge rate.

 

SOME auto washing machines are NOT suitable for inverter use or small generators, some are, -get some specific suggestions from here.

 

A mooring with a shoreline solves that possible problem

[blackrose]

 

A generator and compressor fridge is too expensive.

 

 

Dude, if you think a generator and a fridge are expensive, the cost of bringing up kids might give you a shock!

[Richard10002]

I think you will be looking at 4 x Trojan T105 at £420, A Kipor 2kw genny at about £500,and a 3kw inverter charger, (Victor?), for about £1500-£2k. Then get the biggest alternator sensible for the engine. 12v fridge has to be favourite,. Armed with that lot, you'll always be able to charge up fairly quickly, and run the washer and hoover, preferably with the engine running.

[Arthur Brown]

Don't even plan on the kids leaving home! Gone are the days of kids wanting to move out and having their first flat before they are 17!

[Martin CC O'Beirne]

Thanks Paul C, I've not come across travelpower before - goes and googles

 

Jambo do you know how our fridge at 16Ah compares to a 12v compressor fridge? I cant find figures for comparison.

 

If it draws similar ah then there is no longer an argument for that technology really? unless perhaps cost of inverter was included in the calculation

 

ta

 

Martin

[Martin CC O'Beirne]

lol - its because of kids I live in a boat - an inverter that is also a charger - that's baked my melon - goes googles

[Martin CC O'Beirne]

OK so this wont be news to almost everybody here - but i didn't know, so perhaps it will be useful for somebody else

 

 

 

The inverter - doing what it does to 12v to make 240v takes 20x the current (as 20* the v from 12v to make 240)

 

So a 3kw kettle that takes 13ah - takes 260 at 12v going through an inverter

 

So presumably with that handicap - no 240v appliance could ever compete with a 12v appliance

 

but i guess with microgeneration where its at now and the efficiency of 240v appliances (and things becoming more affordable) - things are more possible than ever before

[Arthur Brown]

Remember that a 25bhp engine will have to work to drive the boat, and taking much power off the pulley end will affect propulsion performance

Remember that a fridge's economy rating doesn't account for the door being left open by passing children! Allow a lot for children inadvertently leaving doors open, taps on lights on etc. Be very sure that you have charging points for everything that makes their electric life complete (4 phones each, pods, pads, and games by the dozen. The average child could live in a RSPB reserve and not see a bird!

Edited May 2, 2015 by Arthur Brown

[Arthur Brown]

A 1 KW load at 240v uses cable that's convenient and flexible. A 1KW load at 12v uses cable that needs a machine to bend it. Start now to give up electrical life, big current consumers just don't go with boating.

 

3Kw for a kettle for five minutes, uses 3000/12 watt hours = 250

divide this by 12 (for volts) indicates that you will use 250/12 Amp Hours = 20 and a bit amp hours, which is a LOT from a battery bank for five minutes.

 

Remember also that home generated electricity costs about ten times the cost of mains (excluding solar).

[Martin CC O'Beirne]

Ha! - true true

 

So I'm starting to cop out of these big plans

 

I'm thinking keep my existing set up - buy a 12v fridge and a twin tub. nothing else required. existing inverter is 600psw.

 

An Engel fridge is 0.5-2.5amps costs £845 (ouch). Reading Amazon reviews every twin tub in existence is crap - so not sure where to go with that just yet

[Alan de Enfield]

So a 3kw kettle that takes 13ah - takes 260 at 12v going through an inverter

 

 

 

Just a slight correction (that relates to all appliances - not just a 3kw kettle) you also have to take into account the inefficiencies of the inverter (about 10% on a quality one, maybe 15% on a 'cheap' one) so your 3kw kettle is actually drawing nearer 300 amps from he batteries thru the inverter.

 

It doesn't matter if you use 12v or 240 volt a 3kw kettle will (roughly) use the same amount of amps.

 

This is why most boaters do not have 'large electrical appliances' such as electric cookers, washing machines, dishwashers, hair straighteners, curling tongues, electric kettles, etc etc.

 

I have a 900 watt toaster, a 900 watt electric oven, a 900 watt 'Hoover', a 600 watt George Forman and a 900 watt deep fat fryer. I can run any ONE of these at a time via my 1000 watt inverter. I must however run the engine for 2x as long as the appliance is in use to 'replace' the amps used.

 

Eg - it takes 9 minutes for the deep fat fryer to come to temperature, then 9 minutes to cook a basket of chips. I MUST run the engine for about 40 minutes to re-stock the battery.

[Jambo]

Jambo do you know how our fridge at 16Ah compares to a 12v compressor fridge? I cant find figures for comparison.

 

 

I would suggest less (even taking into account the inverter losses) but it's difficult to say how much less and you'll see no end of threads on this very website arguing politely discussing the merits of the two.

 

If you google shoreline fridge ah or shoreline fridge amps (or any other 12V fridge manufacturer) then you get some estimates of consumption, no two the same as far as I can make out. The quoted figures for 12V fridges should be taken with a large pinch of salt though. The quoted figures for a 230V fridge are much more believable because they all have to undertake a standardised test under controlled conditions.

[OldGoat]

For comparison purposes it's reasonably true to say that a Shoreline (or any other 12v refrigeration device) consumes about the same power as a quality mains unit. The differences start here:-

An inverter will have conversion losses somewhere between 5-15% depending on the manufacturer = design quality

In addition the inverter will consume power when it's not delivering power to the device, say 10-15 amp hours per day (depending on how long the fridge is on).

It's not a disaster, or a NoNo, but there is a penalty for running a mains unit and you have to factor that into your battery size and charging regime

OTOH using a mains fridge, you have a wide choice of size and quality of units to choose form - some of which will be better than the Shoreline on both counts. They take a fairly industry standard case either rip out the 24V compressor and fit a Danfoss unit in it's place.

 

They are NOT a rip off outfit, their price reflects the:-

• cost of purchasing cases in very small quantities
• plus the cost of modifying the case
• plus office costs
• plus profits,
• plus not selling very many units
• plus - whatever

In economists terms that's the value of the product

From the customers' point of view - it's not a magic, high quality device that justifies it's apparently huge price. It's a modified 240V fridge; and that's what it costs to produce.

 

The dichotomy is which way to go; charge your batteries a bit more often or stump up a lot for the convenience of not running the genny / engine for what? 10% longer?

 

I have an Aged 24v LEC unit which I love to bits.

Does the job admirably - freezes ice for Mensahb's G&T and my Whisky Mac, plus avoids us having to shop frequently.

Sadly the case interior is falling to pieces.

I can't find a suitably sized fridge freezer anywhere, from any source. So it's bodged with gaffer tape and the shelves are rusting

My choice.

Live with it.

[Martin CC O'Beirne]

Thanks all - we would as a family benefit from a proper sized ladar fridge - and I think my set up can cope - we may consider a marina next winter anyhoo with a little one onboard.

 

The liebherr it is

 

I now have to find a twintub

 

and seeing as I have saved a few thousand pounds today - time for a comfy new chair

 

Anyone in love with a particular twin tub, please let me know

 

my inverter is 600w but it wouldn't be end of the world if it needed upgrading a little for a decent twin tub.

 

Thanks

 

Mart

[smileypete]

It's the ~2kW heaters on full size machines that hammer the batts.

 

Some have a cold wash button that may let them run on a lower power pure sine inverter, some on here use the cold wash but add a kettle of hot water through the detergent drawer to boost the temp.

 

There are some slimline machines with less depth, or the studio machines like the Candy AQ1000F, if the twin tub is too trying in the longer term maybe consider one with a cold wash option. (the Candy has it)

 

If the engine running becomes impractical one of these may be worth considering:

 

http://thepowersite.co.uk/generators/petrol-generators/?manufacturer=39

 

Would need safe and secure storage, in a locker similar to a gas cylinder locker.

 

Ideally find other boaters in a similar situation to where you will be, and see how they approach things.... do come back and ask away if you need to...

 

cheers, Pete.

~smpt~

Edited May 3, 2015 by smileypete

[Martin CC O'Beirne]

 

Some have a cold wash button that may let them run on a lower power pure sine inverter, some on here use the cold wash but add a kettle of hot water through the detergent drawer to boost the temp.

 

Thanks Pete - Genius! That may swing it back - I wonder what it draws from the batts on a cold wash?