Wind – Currently lowest cost form of large scale renewable energy but restricted to windy sites which adds to transmission costs. Highly variable and excess production must be shed. Average production around 20% of capacity. Can produce at night to help offset solar shortfalls.
Solar Photovoltaic –
Rapidly expanding renewable source with costs continuing to fall.. Despite improvements in battery storage Solar PV is likely to remain an important but minor component of grid power especially in levelling peak summer demand spikes for air conditioning.
Silicon – Doped with Germanium or Gallium. Converts close to 20% of incident sunlight energy if correctly angled for latitude and tracks the sun. Tracking systems use power and suffer from breakdowns. Fixed panels perform poorer in mornings and afternoons to produce an average daily total of 5hours at rated output. Cloudiness further reduces output.
Thin Film – Use organic molecules or photosensitive compounds containing Rhodium, an exceedingly rare element. Theoretical efficiencies of up to 60% and can be printed on glass or roofing surfaces but suffer from breakdown in sunlight. http://www.dyesol.com/
Solar Thermal – Towers surrounded by fields of tracking mirrors can achieve high enough temperatures to store heat energy as molten salts. Requires flat land and relatively low cloud cover limiting installation to inland sites and consequently higher transmission costs. Relatively high capital cost but low running cost. https://bze.org.au/zero-carbon-australia-2020 BZE report suggests the use of pelletised biomass to heat boilers in extended periods of overcast.
-Parabolic troughs develop lower temperatures suitable for oils or super heated water. Energy can be stored overnight as super heated water in insulated pressure vessels similar to propane tanks. Uniflow steam engines can be used to meet variable electricity loads at medium scale (100 -500kW) http://www.terrajoulecorp.com/ Competitive to current wholesale power rates.
Wave Energy – Most attempts at surface generators have failed in storm damage. New sub-surface designs have now achieved substantial continuous service generating sufficient pressures for desalination or power generation.
http://carnegiewave.com/ Now producing 1MW units with self contained generation.