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Solar Insolation – Understanding & Measuring

Solar Insolation Map of the US

If you do anything at all with solar energy, you keep running across this term solar insolation. Note the spelling “insolation”, and not “insulation”, which is the stuff you put into walls to keep your house warmer. So what is solar insolation, how is it measured, how can I find out the solar insolation for my location, and how can I used this information in my solar application?

What is Solar Insolation?

If ever there was a confusing term, this one is it. Of course you can always consult the invariably comprehensive Wikipedia, but you may end up even more confused. According to this site, the strange term comes from the phrase: “INcidnet SOLar radiATION“. It is the amount of energy from the sun over a given time period. In contrast, solar radiance is the instantaneous power coming from the sun. While both are typically measured in kW/m2 , radiance is an instantaneous measure, while insolation is a measurement over time. Therefore, it is only correct to state insolation as kW-hrs/m2 .in order to show the cumulative time measurement.

There is another complication – … Read the rest

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Refuelable Battery


Batteries are the weak link in both off-grid energy applications as well as electric vehicles. Until this obstacle is overcome, these much needed uses will remain niche areas. Since I believe almost all of our problems can be overcome if we set our hearts and minds on solving them, I think effective electric storage technologies will be eventually developed.

There are some new developments hold promise. One of these is a refuelable zinc-air battery. This battery uses zinc pellets in an alkaline electrolyte. It has the advantage that zinc is abundant, cheap and safe. It is also easily recycled. You can read a short PDF file describing the technology – here. The other new development is for what is called a “flow cell” being developed by MIT. This battery uses a liquid lithium-based electrolyte. It also is refuelable.

I remember when I was a boy, carbon-zinc cells were the only batteries around for household use. Alkaline cells were new, exotic and expensive. Now we have cheap rechargeables that dwarf those batteries. What the future holds is anyones guess right now, but it looks bright.

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