Hydrogen produced from surplus renewable power, or gasification of coal/biomass with Carbon Capture and Storage (CCS), can be injected into the gas grid and used as a major energy store to support the decarbonisation and distribution of energy supplies. The approach could be the biggest single step in enabling the low carbon energy transformation. The concept is already being tested in Germany, but in many countries the approach is barely recognised.
Energy System Challenges
As more and more renewable capacity is connected to the grid, balancing short and medium term fluctuating energy supply with demand requirements is becoming increasingly difficult. Additional energy storage is part of the solution. At the same time, gas supplies in some European countries are either in decline or at risk of price escalation due to supply and security issues and so additional domestic gas supplies would be welcomed. The use of fossil fuels to generate electrical power and for transportation, contributes significantly to our global carbon emissions. The application of CCS to major plant is challenging, especially if the plant is to fill short term energy gaps rather than deliver base load, which used to be the case. Additional generation flexibility would be useful. Existing electricity grids are showing signs of age and with new demands from renewables they are having to operate in ways they were not designed. Alternative energy distribution networks would ease the short term situation. To address these major energy system challenges requires a new perspective and some big picture thinking.
Connecting the Grids
Hydrogen is the solution. Hydrogen from gasified coal or biomass and surplus renewable electricity can be injected into the existing gas grid. Putting hydrogen into the gas grid would form the backbone of a clean energy revolution in which the electricity and gas grids are ‘linked’.
Somewhat paradoxically, we need to look back in time to find the technology to make hydrogen from solid fuel. Before North Sea gas we happily made our town gas from coal. Today, potential exists to use coal, petroleum coke, biomass or waste to generate syngas. This is then split into streams of high quality clean gas (Hydrogen), and CO2. The hydrogen can then be injected into the gas grid.
Surplus renewable electricity can be used to electrolyse water to create even more hydrogen. This could also be introduced into the gas grid.
The approach does not require any new technology and it has the potential to address some of the biggest challenges we face to deliver a cost effective low carbon energy transition. The most significant benefits of such an approach are that it;
- Acts as an energy store by converting surplus renewable electricity to hydrogen which can be converted back to green electricity at any CCGT site, managing the intermittency of renewables. At the same time it enables the gas grid to provide ‘renewable’ heat, with hydrogen as the medium, with no change to infrastructure or end use appliances.
- Reduces dependency on gas imports to address security of supply and cost issues. The approach supports the development of Biofuel Energy with CCS (BECCS), converting biofuel to hydrogen and capturing CO2, to reduce atmospheric CO2 and it also enables use of low cost coal, whilst mitigating the emissions using CCS technology. By reducing gas import needs, CO2 emissions associated with gas imports such as LNG can also be reduced.
- Makes best use of the gas grid as a means to transport energy, whilst having the potential to mitigate regional gas shortfalls and gas flow reversals from declining natural gas production or import volumes. Separating CO2 capture from power generation enables CO2 capture at a location to suit CO2 storage and fuel supply, whilst providing generation flexibility for low carbon power from hydrogen at a location to suit electricity demand. This separation also allows gasification plant to run on a stable and continuous basis, feeding hydrogen into the gas grid.
Possibly the biggest obstacle is that the power to grid concept requires a new paradigm. This requires a big picture view of the energy system which includes electrical power, gas and energy storage along with new and old technologies. Such innovative and creative thinking is not the natural domain of governments, who have a leadership role in creating the correct market environment for the low carbon transition.
The hydrogen specification of the gas grid needs to be sufficient. In the UK the hydrogen specification in the gas grid is less than 0.1%. This doesn’t provide much space for mixing hydrogen with natural gas. Other countries have a more relaxed specification, Germany is 5%, which according to E.ON could be increased in the medium term up to 15%.
Commercial incentives or structures need to be in place to encourage solutions in line with this concept. At the moment many energy market reforms are often focused on electricity rather than energy. There is little focus on applying existing technology to addressing energy storage issues. For private investors to progress major projects, a clear economic basis needs to be established.
There is currently little linkage between CCS and hydrogen generation. CCS is seen as a potential route to decarbonize electrical power generation from fossil fuels, but its broader role in enabling hydrogen production with no CO2 emissions and the benefits of that hydrogen, are being overlooked.
There is some ongoing activity, mainly related to hydrogen production from surplus renewables and its injection into the gas grid:
The UK Technology Strategy Board has a Hydrogen Gas Inject feasibility study ongoing, led by ITM Power, investigating the technical, financial and operational feasibility of injecting hydrogen gas, generated from electrolysis from excess renewables, into the UK gas networks.
In December 2013, ITM Power, Mainova, and NRM Netzdienste Rhein-Main GmbH began injecting hydrogen into the German gas distribution network using ITM Power HGas, which is a rapid response proton exchange membrane electrolyser plant.
In August 2013, E.ON Hanse, Solvicore, and Swissgas inaugurated a commercial power-to-gas unit in Falkenhagen, Germany. The unit, which has a capacity of two megawatts (the output of a typical onshore wind turbine), can produce 360 cubic meters of hydrogen per hour (just over 0.3mmscf/d). The plant uses wind power and Hydrogenics electrolysis equipment to transform water into hydrogen, which is then injected into the existing regional natural gas transmission system. A second power-to-gas project has been started in Hamburg/Reitbrook district and is expected to open in 2014. E.ON has stated that “it is committed to intensively testing the technology which has huge potential”.
Once we can see the potential for introducing hydrogen into the gas grid, it opens the way to address some of the most significant energy challenges we face: providing energy storage, opening up new gas sources, offering generation flexibility and enhancing energy distribution systems. Hydrogen production systems could be distributed across the gas grid and also centralized in key hubs where efficient CO2 disposal was required. Hydrogen is also potentially the key to unlocking the rapid decarbonisation of the transportation fleet through fuel cell powered electric vehicles or modified combustion engine technology.
This article was written by Sam Gomersall.