What can be done to diversify our clean energy technology options?  In recent years we have seen a number of seemingly  “old” technologies undergo a reassessment, and a reinvention.  Geothermal power, once assessed as “an excellent source of baseload energy, but likely limited in commercially exploitable capacity” has undergone a renaissance.

Here’s the new view in the latest IPCC Special Report on Renewable Energy Sources:

In 2008, global geothermal energy use represented only about 0.1 percent of the global primary energy supply. However, by 2050, geothermal could meet roughly 3 percent of the global electricity demand and 5 percent of the global demand for heating and cooling.

That dramatic expansion of scope – a factor of 15 on a global scale – is a function of new technology options and forecasts for higher fossil fuel prices. But it is only one example.

Another technology undergoing a dramatic expansion of options is that of hydropower.  Conventional dams, large and small, use either a natural, or more commonly, an artificial “head” or drop to harness energy.