The total solar energy available on Earth at any time is about 7000 times more than is currently being used.

No – what we do with the solar irradiation makes no difference at all to the amount generated.

Depends on how you define ‘realistic’. It is most effective all year-round where there is sun for nine or more hours a day, but is nevertheless used in areas where there is less.

So-called amorphous modules lose power in very cold places, but for most the colder it is (for any given amount of sun) the higher their output. In practice most lose about 5% output for every 10 degrees C rise in temperature. They are rated at 25 degrees C, but that rating is of the temperature of the cells themselves. In practice at an ambient of 25 degrees C those cells are at 47-49 degrees C – and the module has thus already lost some 10% output. And to save disputes - the above is quoted from the industry’s own data.   

The highest percentage of users is in Germany, primarily due to very favourable government organised rebate schemes. California too is becoming a major user.

It can be anywhere from about three years to fifteen!  A great deal depends on the extent of government and other financial backing, plus inevitable and probably substantial increases in charges for grid-supplied power as fuel costs continue to rise.

The effective life of solar modules is not yet fully known. There are many well over 25 years old and still producing well. Most are guaranteed to produce at least 90% of their new output for 20-25 years.

If that question is changed to ‘as some suppliers claim’, then it’s totally true. It is common practice to base a system’s output on the solar module maker’s claimed output – based on the industry’s Standard Operating Conditions’. These conditions can hardly ever even be approached outside a testing laboratory. In practice a typical grid-connect system produces about 80% of that claimed; that of a stand-alone system about 70%. Almost all suppliers admit this if questioned, but invariably say it is ‘standard industry practice’. Which it is.

I don’t need to – the solar industry has done it already. There is a second but rarely mentioned ‘Standard’ – called NOCT (Nominal Cell Operating Temperature) that sets out the most likely output under more realistic conditions. Most solar modules have this latter data noted on a small panel on the rear of the module. Further, it is usually revealed in the maker’s technical literature. Under NOCT a typical 120 watt solar module actually produces about 87 watts. (I have included a photograph of one such data panel in my book.)

I think the major concern is that complete systems tend (in Australia at least) to be rated using the Standard Operating Conditions method. For example a system promoted and sold as a 1.0 kW system is unlikely to generate more than 800 watts. But I’m an engineer/writer/publisher – not a lawyer. This book may help not least since the issue is likely to be highlighted in reviews. 

No. There are various ways of assessing this, but averaging a large number of assessments shows a probably more than two but less than three and a half years.

The growing trend is for solar to be used to supplement grid power. In such cases the electricity grid acts as the ‘battery’ anyway. Where batteries are needed (as in remote area systems, the expected life is 10-14 years.

Since 2000 or so, the output of the inverters used to convert the solar input to 240 volts produce electrical energy that is far cleaner than that from the grid. Concerning reliability, well engineered and installed systems are very much more reliable than grid power. It is rare indeed to have a failure.

This site is about solar not politics, but it is possible that the emphasis may change from initial equipment rebates to payment to the owner for power produced. This way is far more common in other parts of the world.

In vehicles since 1995, and on our Kimberley property since mid-2000.

Our system has a larger safety margin than most and this enables us to be generator free virtually all year round. We typically need it for about three or four hours during five or six days a year (i.e. about twenty hours a year).

It depends substantially on the location. In places where there is much less sun in winter it makes sense to scale the system for typical Spring through Autumn usage and use a back-up diesel generator to supplement power during the mid-winter months.

They must not face away from the sun, but as sunlight tends to be diffuse, errors in azimuth of 10-15 degrees typically reduce daily input by less than 4%.

Yes. Ideally they need to face into the sun, but mounting then at fixed angle that is close to the latitude angle loses surprisingly little energy in all but the higher latitudes.

Only at high latitude angles – such as Hobart. There is an increasing acceptance that it is simpler and cheaper to accept some minor loss and add a few per cent more capacity to cope.

The skills required are basic and the knowledge needed is set out in my books. There are however restrictions in some countries relating to rebates that can precludes doing the whole job. A fair part of the cost however is in constructing and erecting solar mountings, digging trenches, laying cable etc. It is often possible to negotiate this with the contractor. In Australia you may legally do any work on dc equipment that operates below 120 volts dc, and 50 volts ac. You must use a licensed electrician for all work at voltages above that. In New Zealand you can legally do far more of the work – and in many other countries you can do all of it.

Seemingly so. Australia has one of the tightest electrically regulated regimes in the world – and has the second highest fatality rate from electrocution!  It is far higher than in New Zealand.

It’s not clear. One possibility is that where people are allowed to do more they are legally obliged to have the work inspected on completion by a certified electrician. It is possible that Australians do it anyway, but as it’s illegal to do so they cannot have it inspected for safety afterwards. But that’s just conjecture - I have no evidence to support it.

Worldwide the demand for modules exceeds supply so there is little incentive for manufacturers to lower prices. I suspect however that least part of the recent Australian move to means-test rebates is to force suppliers to reduce their charges.