THE USE OF ENERGY IN THE MOTORHOME

The following article was first published in the MMM (Motorhome Motorcaravan Monthly), the UK's premier motorhome magazine. It discusses the use of energy in the motorhome, its many forms and ideas for optimum use.

Following early retirement, Margaret and I bought Rosie, a 27 ft Four Winds motorcaravan and got her ready to be our home for full-time travel in Europe.

'Practical Self-Sufficiency' was the title of a magazine I read during the 1970's when I had a smallholding in Wales. Electricity could come from a generator, driven by wind or water; heating and cooking was possible by burning wood drawn frugally from 4 acres of coppiced trees; water was led to a holding tank from a spring high above the house; chickens, a goat, fruit trees and an allotment contributed to food supplies.

Little of this is possible in a motorhome, but we aimed to be as self-supporting as possible: to have large and varied reserves of energy and food to meet the different situations we would find on the road; cheap ways of topping-up those reserves; thrift in using them and ways of reducing losses. Food is a separate subject, but here is how we became self-supporting in energy.

The Trouble with Energy is . . .

Often you don't know how much energy you are using or paying for since different kinds of energy are measured in different ways: electricity in watts and kilowatt-hours; batteries in ampère-hours and the engine's output in bhp (brake horse power). You buy bottled gas by the kilogram and diesel, petrol or LPG by the litre (or gallon), with no idea how much energy you are getting.

Life would be much easier if energy were always measured in the same way, so I shall express the rate at which energy is used in watts (or kilowatts if there are thousands of them) and the total amount of energy that might be generated, stored or used in kilowatt-hours (kwh).

The 12 Volt Batteries

It's worth remembering that a 12-volt battery is an essential but puny energy reserve. A typical leisure battery, fully charged, will give less than a kilowatt-hour before it's flat. At home, connected to the National Grid, you would pay just a few pence for a kilowatt-hour and use several of them every day.

I tripled the size of our 12-volt energy reserve by adding 2 extra leisure batteries, bringing the total up to 2.5 kwh. Each battery was given its own switch so that they could be used or charged singly, doubly or all together.

A voltmeter/ammeter was wired into both the charging and the load circuits so that we could monitor the state of the batteries and the rate at which they were being charged or used. Rosie came with 2 more batteries in the engine compartment (to start the big diesel) and these can be switched into the circuit to be charged or used in the motorhome, if needed.

All the batteries can be charged from the alternator in the engine (when it's running), from a battery charger (when there's a mains hook-up) or from the generator. I added 2 roof-top 22-watt solar panels (arrays of photo-voltaic cells) which, on a sunny day in southern Europe, put up to a third of a kilowatt-hour into the batteries: more than enough for a day's use in the motorhome, including an evening of Italian TV.

10 of Rosie's 12-volt lights were fitted with a pair of 21-watt bulbs, a total of 420 watts! We replaced one of each pair with a 5-watt bulb, more than adequate for most purposes: the second position of the switch gives us 26 watts for reading, cooking, eating - occasions when we need to see what we are doing! We also enjoy mellow, warming and cost-effective candle-light.

The Inverter

The 35-watt 9" Grundig TV and the Electrolux Campy vacuum cleaner can run directly from the 12-volt system but we use that excellent invention, the inverter (ours is 250 watts), to run a number of other mains devices from the batteries: soldering iron, electric drill, food-mixer, rechargeable electric screwdriver and toothbrush (but see Acknowledgements below), electric blanket, video, word-processor and printer.

The inverter also powers a small battery charger which keeps us supplied with 1.5 and 9-volt batteries for smoke alarms, torches, bike lights, the clock and a personal alarm. Another way we save buying expensive 1.5-volt batteries is by running the short-wave radio from a regulated DC-DC converter which plugs into a 12-volt socket and gives a 3, 6 or 9-volt output.

The Generator

A 4-kilowatt LPG-driven Onan generator came with the motorhome, but it has only clocked up 34 hours in 30 months! In the absence of a mains hook-up, it can run the microwave or air conditioner if we really need them and it defrosted us, one winter morning in Scotland, by running the electric fan heater when the gas heating failed. But it uses around 3 litres of LPG per hour on half-load, about 75p per kwh at UK prices (an efficiency of less than 10%). It's occasionally convenient but we would have saved energy by not carrying its weight around with us!

The Mains Hook-Up

In winter, there is more demand for 12-volt energy for lights and TV, whilst much less free energy trickles in from the sun. Then we often use an electric mains hook-up when we are on a site, particularly when it's at a fixed price with a reasonable current rating and an accessible, re-settable cut-out! These conditions are sometimes met in southern Europe and almost always in Greece. Then we run all the mains appliances directly off the mains!

Gas Supplies

Heating and cooking are the major users of energy and need large reserves in the form of butane or propane gas, held as liquids under pressure. Butane (C4H10) and propane (C3H8) contain nearly equal amounts of energy, have about the same density and burn at around the same temperature, but propane can be used when it's freezing outside (it has a much lower boiling point). LPG (liquid petroleum gas) is a mixture of propane and butane; it is freely and cheaply available in some European countries (the proportion of butane to propane varying from country to country) and it is pumped directly into a large holding tank fixed to Rosie's chassis.

1 kg of propane contains 13.9 kwh of energy - a 10 kg gas bottle contains more energy than 170 fully-charged 12-volt batteries! Gas is also good value at from 4p per kwh (LPG in Belgium) to 14p per kwh (small Calor gas bottle in the UK). So we chose LPG, but not Belgium!

The 60 litres of LPG stored in Rosie's tank weigh over 30 kg and contain 430 kwh of energy. Since re-fills are hard to find in some countries (like the UK and Greece), we added a connector for a 5 kg (70 kwh) German propane bottle, which is the easiest to carry and refill throughout Europe.

Fearful that we might not wake, we couldn't sleep without the propane and carbon monoxide detectors fitted in the rear bedroom. They take about 4 watts from the 12-volt system, and we switch them on when we go to bed. Not least, the glow from their indicators provides us with a ghostly green night-light.

Cooking

We cook using the gas hob, grill and oven. The hob-top Camp-a-Toaster produces excellent energy-efficient toast, whilst a large pressure cooker conserves both energy and flavour. However, with an amenable mains hook-up, the 800-watt microwave is the most energy-efficient of them all.

Heating

Space and water heating are the big users of energy. Rosie came fitted with a 6-gallon Atwood gas water boiler, rated at 1.5 kilowatts. I added a 400-watt, 2-gallon electrical water heater to take full advantage of non-metered hook-ups, plumbing it to heat the 6 gallons in the Atwood gas boiler as well, if needed. Hot water for smaller jobs comes from a gas-fired whistling kettle or a 750-watt, 0.8 litre Kenwood electric kettle.

The best way of keeping warm is to go south for the winter. Even there, we sometimes use the energy-guzzling 10-kilowatt gas-fired blown air heating to take the chill off Rosie (and us) first thing in the morning, although we usually find the small catalytic gas heater quite adequate (well-ventilated with the carbon monoxide detector switched ON!) With a user-friendly mains supply, we enjoy the 1-kilowatt electric fan heater.

Our parents, brought up in simpler days, recommended warming the body rather than the home. This we do with Helly Hansen thermal clothing and a hot water bottle, as well as the higher-tech 90-watt electric blanket. Exercise also produces warmth!

Leaks and losses of heat energy have been reduced by fitting thermal-lined curtains over the original blinds, velcro-held thermal covers for the roof vents, an extra layer of carpet bought from a Greek market, an insulated external Taylor-made screen for the cab and by dividing the living space into 3 areas with heavy full-length curtains.

Keeping Cool

This can be equally energy-greedy. The large fridge/freezer uses gas (adequate on its lowest setting) or mains electricity when that is available. Rosie also has 2 air conditioners, one in the roof running at 2 kilowatts (from mains or the generator) and one in the cab, drawing its energy from the engine. We have used and enjoyed the latter but, overall, it may be cheaper to drive north for the summer!

Energy Costs

We monitor our use of energy with an ammeter and voltmeter and by looking at the charges on our bank account. In 22 months covering 20,000 miles, we have spent an average of £18.50 per day (£9.25 each) on food, diesel, gas, camping, tolls, ferries, postage, films, magazines, telephone calls, entry to historic sites, etc (this does not include 'capital' items such as insurance, equipment and servicing). Energy costs have been less than a third of this daily average: £0.30 for gas, £4.55 for diesel and an estimated £0.40 for electricity. All of these figures could be reduced further by driving and eating less and camping wild more often!

What's our most energy-efficient device? There's no problem in answering that - it's the bicycle, which uses less energy per kg per km than any other machine, animal, bird or fish. One small piece of chocolate is energy enough for 25 km!

More Facts

Acknowledgements

Alan Bee of Sporti Leisure supplied the inverter (PROwatt 250i) which just plugs into a 12-volt socket, the solar panels (22-watt Uni Solar), a regulator to prevent over-charging of the battery, a meter (Fox D1, 8 to 30 volts and 0 to 20 amps) and much good advice. The Owner's Manual for the inverter warns that it may damage a small minority of rechargeable appliances, although ours were OK.

Jonathan Frost of CAK sold us the 400-watt, 2-gallon water heater (Mini Boiler 8) and gave us the advice we needed to connect it to our American pipes and wires.

Calor Gas in Slough and Peter Frankland of Huddersfield University helpfully supplied information on the densities and energy content of butane and propane.

Thanks also to the hardware shops in several countries who let us ferret through their stock looking for connectors, wires, clips, screws, pipes, etc. We now know why the Spanish call them ferreteria.