What is Solar Energy?

The typical description might be: Solar power from photovoltaics and thermal solar power plants. But that's too simple.

Solar energy is the whole bunch of

• solar power,
• collecting solar light for heat,
• wind power(winds are sun-driven),
• hydro power (sun drives evaporation which lifts the water upwards/rain fills the lakes of hydro power plants)
• near surface geothermal energy use,
• biomass.

Only two of these paths from solar light provide storable energy for electricity production: Hydro power plants and biomass production. Both need large areas to provide meaningful amounts of energy and hence alter land use in a sometimes dramatic way.

Photovoltaics and wind power produce electricity dpending on solar irradiation and the abundance of feasible wind speeds. For these pathways we need storage capabilities for electricity - to omit the reliance of weather factors.

Direct Storage of Electricity

Batteries? The natural answer. But: Batteries are expensive - and just need a lot of energy for their production. Lifetime in terms of recharge cycles is limited to several hundred, perhaps 1000 charges. The majordrawback of lithium batteries - today's state-of-the-art battery technology - is the limited availability of lithium itself.

Hydropower facilities can store electricity by pumping water into the higher reservoir during periods of low electricity demand and release the stored energy if the demand rises. But the existing facilites are limited in capacity and their need for large areas and height differences limits the possibility to built up new facilities.

The development of new battery technologies is crucial: Batteries which consist of materials which are availablein aboundant quantities. Cheep - in terms of energy and cost - manufacturing processes. Longevity and environmental safety. This should be one of the two priorities of energy research: Electricity is the most versatile energy which is applicable in all energy sectors like household or transportation.

INdirect Storage of Electricity

In the meantime we need other measures to survice the interregnum without optimal batteries. Heat can be stored with simple devices: A well insulated tank filled with water or a similar device. Why not equipping our homes with a 5000 litre heat storage tank? It stores (between 40 and 90 degree centigrade) round about 300 kilowatt*hours or - in another "unit" 30 litres of oil/30 cubic meters of natural gas. In a well insulated house that amount of energy is enough for one week during deepest winter time.

Wind power and solar power which are above demand might be stored as heat energy instead of storing electrical power in very expensive batteries. Or think about food storage facilites which freeze foods for conservation. This facilites are well insulated and cooling them down a little bit more than necessary can be done during high power gains by wind and photovoltaics. If wind and solar power are below demand, the cooling can be interrupted for days. Until the temperature rises above a limit in the storage facility.

From Electrical to Chemical Energy

Another path to store electricity is to convert it's energy into chemical energy. A very interesting chemical compound is methane, the main component of typical natural gas:

Electricity + Carbon dioxide + Water --->  Methane + Oxygen

Current processes use electrolysis to gain hydrogen. The hydrogen reacts with carbon dioxide to methane by using the right physical conditions.

But let's think about a process which uses carbon dioxide from the atmosphere. And a device that produces methane directly from atmospheric carbon dioxide and water by solar power.

Why methane? Methane is not as versatile as electricity but: Low and high temperature heat is provided by burning methane. Cars can be converted to digest methane. The power plants with the highes efficiencies are combined cycle gas turbine power plants, fired with methane hence producing electricity with a conversion efficiency of round about 60 per cent!

And last but not least: Most countries in the world have regional and/or national pipeline networks to distribute natural gas which can be substituted methane.

The Bottom Line

We have to do some basic research to

• develop the "perfect" battery and
• to develop processes which convert electricity into a storable energy like methane, methanole or octane.

Come on countries of the world, do the necessary research in a fair competition and come together to find the optimum devices to give us back independance and a livable system earth!