Power to gas – the new kid on the block?

Recent advances in materials & technology have made power to gas an interesting and perhaps the most exciting contender for long-term energy storage.
Published: Tue 10 Sep 2013

“Power to gas requires non siloed thinking” says Dr Graham Cooley CEO of ITM Power one of the pioneering companies in this space. The idea is remarkably simple in that excess zero carbon renewable energy is used to produce hydrogen through electrolysis. This is an improvement on the current scenario where renewable sources, such as wind, are switched off during low demand or, as recently reported in Germany, sold to the grid at a loss.

The hydrogen generated from the process can then be stored for later use to generate electricity through fuels cells or gas fired power on demand. More interestingly though - as will be the case when the pilot power to gas plant being constructed by the Thüga Group goes live - the hydrogen will be injected into the existing gas network.

The second approach has some obvious additional benefits as it decarbonizes heat, one of the hardest things to achieve by adding hydrogen into the existing gas network. The use of the existing gas network to utilize / store the produced hydrogen also removes the need to construct additional (and costly) high pressure storage capacity.

Technology developments

Some key technology developments have removed issues which have been barriers to date. ITM power's self-pressurising rapid response electrolyser, for example, has a response time of less than the required 2 seconds as demanded by the UK grid and additionally, as the electrolyser runs at a pressure of 80bar equivalent to the Gas grid, no extra nergy is needed to compress or store the resulting hydrogen.

System efficiency & generation

Much like a car, efficiencies for dynamic systems fluctuate. However, companies such as ITM power and hydrogenics are looking at efficiencies of over 60% and when combined with heat recovery systems, this figure can rise to 71% in optimal operating conditions, argues Dr Simon Bourne CTO at ITM.

A recent E.ON test run successfully injected 160 cubic meters in one hour with the aim of hitting 360 cubic meters an hour in operational mode giving a potential energy of 1,077 kWhr.

Barriers to adoption

The adoption of power to gas faces a number of obstacles. For instance, legislation in the UK prevents the gas grid from containing any more than 0-1% of hydrogen. This is despite a historical precedent of up to 60% hydrogen in the UK grid during the early days of North Sea exploration. A recent US Department of Energy-funded report suggests acceptable blending levels between 5% - 20% hydrogen before appliance modifications may be required. However, even at such low blends, this is a significant hydrogen store.

There is also evidence of metal pipe degradation at high hydrogen levels but solutions do exist. Additionally, hydrogen, being a smaller molecule than methane, is more mobile in many polymers and elastomeric seals which are used in natural gas distribution. Again, concerns are low and require monitoring.

Transmission and economic benefits

A key challenge to renewables lies in the fact that the optimal point of generation is not next to the point of consumption. As an example to complete the design and framework for Germany’s Energiewende, almost 4,000km of new transmission lines, of which less than 300km have been built, will be needed by 2022. Additionally, the transmission of electricity follows the I2 law- the inevitable loss of power for most developed countries. This runs at 6% of output based on latest Worldbank figures.

Another economic benefit is that renewable power generators now have the potential to sell zero carbon hydrogen at a profit rather than electricity at a loss, as can be the case today.

Engerati Analysis

Power to gas offers one of the most promising energy storage systems to help underpin the need for renewable energy generation. Unlike other systems, it delivers long-term storage and it can be located in the same environment or close to the point of generation. Judging by the number of known power to gas pilots, the technology is clearly being taken seriously. This is definitely one to watch.