CURRENT AND FORTHCOMING TRENDS

In view of the seemingly inexorable changes in various technologies it is timely to have a brief look at developments that may affect current and near-future plans – particularly for those seeking to build or modify.

36/42 Volts There is certain to be a change from existing 12/24- volt electrical systems to 36-volt battery systems (charging at 42-volts). This change is driven by the ever-increasing current draw of the multiple computer and other electrical systems in passenger cars and cannot any longer be met by increasing alternator current output (increasing the voltage enables the same power {watts} to be generated at a correspondingly lower current). It is also driven by the realisation that such a change enables many current hydraulic and mechanical systems to be electrically operated. Such systems include power steering, shock absorbers, valve actuation etc. The existing separate starter motor, alternator and flywheel are likely to be combined: as indeed they were on a few cars (such as the Lanchester and bull-nosed Morris Oxford) built in the early 1900s.

It is likely that the first RV's to be affected will be European-based campervans. Trucks and coaches etc will certainly follow – but possibly not for some years. In the long run this will be a welcome innovation as it will greatly reduce the voltage-drop problems virtually endemic to the RV industry. It will of course necessitate all new 36-volt lights and appliances etc – unless a 36-12-volt converter is used.

There will be no problem supporting existing 12/24- volt systems.

Fuel Cells

I covered this topic in depth a few issues ago. Since then little has changed: we shall eventually see 650- 1000 watt 12-volt fuel cells that cost less than $1000. When this happens they will wipe small generators off the face of the planet. I am however increasingly cautious about forecasting when (but not if) they will be commercially available. Almost all promotional claims, and magazine articles suggesting ‘real soon now’ are of such romanticism they would be better written in iambic pentameter.

Right now it is better to assume they will happen but to make no plans accordingly.

Solar Modules

Ongoing developments are resulting in greater output per unit area. Recent 120-watt and 165-watt modules are much the same size as 64- and 80-watt modules of only two/three years ago. Cost per watt is dropping slightly. Weight per watt is falling – most 120-165 watt modules weigh 11-12 kg.

Uni-Solar modules still offer far better shadow resistance and heat tolerance, but it is increasingly hard to justify their use except in very hot places where there’s ample room to locate them – they are about twice the area per watt of competitive offerings.

There are few reliable (non-promotional) reports regarding the Russian-designed double-faced modules – and their manufacturer is seemingly not prepared to release much useful technical data. To be effective they need to be mounted some distance above a light reflecting surface. This may inhibit their use with RV's.

New developments are ultra-thin ‘bendy’ modules (developed by Eindhoven University of Technology and made by Akzo-Nobel). The modules are so thin that they can readily be sown onto material such as clothing, awnings etc. The upside is that they are likely to cost only A$2 or so per watt (about a fifth of conventional modules). The downside is they are only 7% or so efficient – about half that of conventional modules. (For further information see ‘New Scientist’ 18 Dec 2004, p23).

The increasing efficiency of conventional solar modules now enables campervan and motorhome ‘house’ systems to be optionally designed such that they are independent of the vehicle’s electrical system. This results in a much simpler and cheaper system and has the major advantage that the solar regulator can be set up to provide the optimum charge regime for whatever batteries are chosen.

This approach is recommended in my book ‘Solar That Really Works – Motorhome Edition’ (obtainable through the CMCA). It has also been used very successfully in my OKA since 2001.

Right now there is a world-wide shortage of solar modules following a huge multi-billion order placed by Germany.

Multiple Power Point Trackers

Because of an inherent voltage/current mismatch, all conventional solar modules and regulators inherently supply only 70% or so of the rated module output when used with a 12-volt electrical system: they only produce their rated output when used with a 17-volt load.

A relatively recent innovation, called ‘Multiple Power Point Tracking’ partially overcomes this loss. The technology is in effect an ‘electronic torque converter’ that juggles volts and amps resulting in a typical gain of 15- 20% in current output (vendors tend to claim 25%). This technology is now inbuilt into some solar regulators, notably built by Outback Power Systems (see www.outbackpower.com). It is also inbuilt into a solar powered 48-volt brushless dc pump motor that I’ve recently installed in our new swimming pool.

Right now, including MMPT in a solar regulator doubles or triples the price. In many cases it is cheaper and simpler to add about 15% more solar capacity. The cost of including MPPT is however bound to fall.

Batteries

Excepting that their cases rarely leak, conventional lead-acid battery development has remained all-but stagnant for the past 75 or so years! There however is an increasing interest in gel cell and particularly AGM batteries – and the price of the latter continues to fall. If considering AGM batteries, bear in mind that they can readily and speedily be charged close to 100% from conventional vehicle alternators as well as via generators and solar modules. They can also be quite deeply discharged (to at least 20% remaining charge) with little harm. Thus some 75%-80% of the nominal capacity is available for use – compared with the 35%-40% or so with conventional deep cycle batteries. This goes a fair way toward offsetting the higher cost.

LED Lighting

Now widely available (albeit costly) alternative for side and tail lights, torches etc, white LED lights (and particularly warm white) are still not efficient enough for general lighting – but are ideal for reading lights etc.

This situation is changing rapidly and it is probable that efficient and affordable 10-20 watt white LEDs will be available by 2007. When this happens they are likely to replace all other forms of interior lighting. But right now, big white LEDs are extremely costly and little more efficient than incandescent globes.

Build Quality

I would like to report that this is improving – but I cannot. Many manufacturers and vendors provide good, well backed-up products, but there are a distressing number of new-buyer horror stories. Seriously consider having a legally binding contract drawn up prior to purchase, that particularly stipulates the product’s ex dealer (i.e. not ex-factory) weight. If in the slightest doubt about the above, your insurer before signing a contract.