If solar energy is so free why it is not widely used??

Solar energy is widely used by nature and has long been used by man for drying and heating. However, I suspect you're speaking of electricity from solar energy. The short answer is that the equipment is rather expensive from a capital cost point of view.

Most photovoltaic (PV) systems cost on the order $7 to $12 per Watt of capacity. By the time you divide that installation cost over the actual electricity produced by the system in the 20 to 30 years of its life, you end up paying $.35 to $1.00 per kWh vs the $.10 to $.30 your electric company charges you.

These systems are getting cheaper though, and there are other technologies, such as concentrating solar power, that in the long term will be as cheap as coal or natural gas plants. In the meantime, there are a variety of federal and state programs that will help individuals and corporations pay for solar energy equipment.

Several reasons:

1) Unreliable. ( like windpower, it's sometimes not available)

2) It has a low intensity/density. (it is spread over a wide area)

3) Converting it to a useable form is expensive

It is in use in the southwest U.S. deserts in private and public buildings. There are vast amounts of unpopulated areas there where large sun collectors are placed.

It's expensive to buy the solar setup initially.

Where I live, it's cloudy 1/2 the year. Add the up front costs and it becomes economically unuseable.

too expensive to initiate. Over the long run it will pay off but you gotta bring a phat checkbook upfront to get it started.

The price of the equipment to change it to electricity.