Hydrogen, the first element of the periodic table, was discovered back in 1766. While it is commonly used in the chemical sector, its application in the power generation today is still relatively limited. However, change is just around the corner.
Hydrogen’s potential for the energy sector has to do with its unique properties and wide scope of potential uses. First of all, it’s important to stress that the only emission resulting from hydrogen combustion is water vapour.
Therefore, there is an array of solutions available for energy generation from hydrogen (H2 in its molecular form). Combustion engines and gas turbines can use it to obtain thermal energy to be subsequently converted into electricity.
Alternatively, it can be used in fuel cells where electricity and heat are produced directly. Furthermore, it can be blended with natural gas in the gas grid to improve the environmental profile of Combined Cycle Gas Turbine (CCGT) plants and gas-fired Combined Heat and Power (CHP) plants, as well as any other gas-based equipment.
Grey, blue and green hydrogen
Unlike natural gas, H2 in its pure form is rare on Earth and needs thus be produced. As of today, three main techniques exist.
1) The first, known as Steam Methane Reforming, or SMR, entails the reaction of steam at high temperature and pressure with methane. This is currently the most widespread form of hydrogen-production. Because the methane used in this process is often of full fossil origin, it is commonly referred to as grey hydrogen.
2) However, hydrogen produced from natural gas in combination with Carbon Capture and Storage is referred as blue hydrogen and climate neutral since the CO2 emissions from the natural gas are captured and safely stored.
3) A less common but more promising way to produce hydrogen is via water electrolysis. Here, electricity is used to split H2O into H2 and O, with the latter also being a valuable by-product for a number of applications. Using electricity to produce e-fuels is a process referred as Power-to-X, or PtX. When the resulting e-fuel is hydrogen, the process can be referred as Power-to-Hydrogen, or PtH. The energy mix used to power the electrolysis process greatly influences the greenhouse gas intensity - and therefore the climate-friendliness - of the resulting hydrogen e-fuel. For this reason, besides the aforementioned grey and blue hydrogen, we also distinguish green hydrogen which is produced only from renewable energy sources.
Hydrogen: a versatile energy carrier
The production of hydrogen through electrolysis can play a key role in stabilising the electric grid. By using excess of electricity from intermittent renewable energy sources, like wind and solar to produce hydrogen, congestion in the electricity grids can be prevented.
In 2016 alone, congestion at bottlenecks in the German grid resulted in a cost of €505 million in charges in re-dispatch and €373 million in compensation from feed-in management (i.e. compensation for disconnected plants, mostly wind turbines). These charges were ultimately born by the German consumers.
Through its concept of Clean Energy Hubs, Energy Technologies Europe (ETE) fully supports the integration of electrolysers into the grid as a tool to promote grid stability.
ETE also supports blue hydrogen as an important bridge-solution because for the coming decade(s) it produces fewer emissions than hydrogen production with electricity from the average European grid, as shown in the figure below.
Finally, ETE actively supports both green and blue hydrogen and advocates for an adequate policy framework that accelerates their commercial uptake.
Figure 1: Comparison of the CO2 intensities of hydrogen production using electrolysers and grid electricity (blue bars) and natural gas with carbon capture (pink bars). The pie charts illustrate the desired electricity mix according to the REmap case for 2030 and the decarbonised scenarios from "A Clean Planet for all" for 2050.
Source: Hydrogen for Europe - Final report of the pre-study by IFPEN and SINTEF: http://bit.ly/2JDI3oD