enewable energy is generally defined as energy that is collected from resources which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Based on REN21‘s 2016 report, renewables contributed 19.2% to humans’ global energy consumption and 23.7% to their generation of electricity in 2014 and 2015.
Efficient energy storage is very important with many renewable power sources, because the energy generated by them changes a lot depending on day time and weather (especially wind and solar power). Electrical energy is stored during times when production (especially from intermittent power plants such as renewable electricity sources such as wind power, tidal power, solar power) exceeds consumption, and returned to the grid when production falls below consumption.
Efficient energy storage is challenge. Battery powered energy storage systems have been designed and built (for example Tesla Energy), but they have challenges especially on the cost, making it hard to justify the costs of them in wide scale use (there are special applications where they are excellent already).
A new and interesting way to store energy is Power to gas. Power to gas (often abbreviated P2G) is a technology that converts electrical power to a gas fuel. There are currently three methods in use; all use electricity to split water into hydrogen and oxygen by means of electrolysis. It is possible to combine the hydrogen with carbon dioxide and convert the two gases to methane that may then be fed into the natural gas grid.
Methane can be used for heating, for running cars and can be quite easily stored. Burning this way methane will release CO2 the same amount that was used when generating that synthetic methane – it is carbon neutral over the usage cycle.
In 2013 a power-to-gas research project has been launched in Germany. A research network of institutes and companies will evaluate the capability of long-term storage technologies in a 100% renewable energy electricity scenario. Eleven European companies have established the North Sea Power to Gas Platform, a joint body to explore the viability of power-to-gas in the countries surrounding the North Sea area. The combined generating capacity of offshore wind farms on the North Sea could reach about 100 GW by 2030, while the PV capacity installed in the countries surrounding the North Sea is expected to increase from 35 GW in 2012 to almost 60 GW in 2020. P2G is expected to play an increasingly vital role in the way energy systems develop as the issue with renewable energy sources like solar and wind power is intermittency. With the P2G concept, temporal surpluses can be reduced by converting renewable energy into gas.
The development of P2G is continuing. Audi opens 6 MW power-to-gas facility article tells that Audi has opened in 2013 a 6 MW power-to-gas facility in Germany, making it the first automaker to develop a chain of sustainable energy carriers. The plant, located in the Lower Saxony city of Wertle, uses green electricity, water and carbon dioxide to create hydrogen and a synthetic methane known as Audi e-gas that is distributed to compressed natural gas (CNG) filling stations. The project shows that large amounts of green electricity can be stored efficiently and independently of location by transforming it into methane gas and storing it in the natural gas network, the largest public energy storage system in Germany.
P2G will also be tested in Finland. Lappeenranta University of Technology and VTT Technical Research Centre of cooperation will be built a demo plant, which will be piloted in the production of gas with solar power systems. The raw material used in the sun, water and carbon dioxide separated from the air. The study is the first of its kind for this type of integration of processes in Finland. Research will seek to build know-how, which allow the implementation of industrial-scale solutions. second main purpose of the project is to create new business opportunities for Finnish industry.
This power to gas looks link a very interesting technology to solve energy storage challenges that you get with wide use of intermittent clean renewable energy.