Renewable Gases

REN, in its various gas transmission, storage, and distribution concessions, ensures the passage of any gas as long as it is compatible with its assets and within the legal framework in force. Currently, and as a result of developments in European and national policy, there is a clear need to include renewable gases in the energy mix, such as hydrogen, biomethane, and synthetic methane.

The proper mixing of hydrogen with natural gas is ensured by a Mixing and Injection Station. The volume of hydrogen to be mixed with natural gas is limited to a certain percentage, given existing technical constraints, both at infrastructure and legal capacity level. In Portugal, legislation provides for a maximum limit of 5% for the transmission network until 2025 and 10% until 2030, while for the distribution network it is 20%. REN is carrying out studies and developing the necessary projects to accommodate these limits. 

Mixing green hydrogen with natural gas makes it possible to take advantage of current infrastructure and existing gas consumption, creating scale and providing a vehicle for decarbonisation, as well as boosting the development of the hydrogen market.

For each end consumer it will be necessary to validate the relevant gas quality and safety characteristics, in order to be able to account for the volume of gas consumed and the gross calorific value. Only then will it be possible to bill energy consumption fairly and ensure that it is delivered with quality and safety. 

Currently, the monitoring of new gas mixtures is done by: 

• Assigning gas quality parameters to all outlets.  
• Creating local quality areas.  
• Installing devices to determine the calorific value at critical points in the network.  
• Computational simulation of gas quality.  
• Combining the calorific value of different types of gas by conditioning.   

The characteristics of the installation will determine the technical and economic feasibility of each solution.  

For questions regarding connections to the Gas Transmission Network, please contact REN at gas.ligacao@ren.pt

There are different processes and technologies for producing hydrogen: 

Grey Hydrogen: grey hydrogen uses fossil fuels as an energy source, with CO₂ emissions into the atmosphere. It can be produced by steam reforming coal or natural gas. 

Blue Hydrogen: blue hydrogen uses natural gas as its energy source. The CO₂ released is captured, stored, and used in various industrial processes or buried in the ground. It is produced through the steam reforming of natural gas. 

Green Hydrogen: green hydrogen uses renewable energy sources. It is produced through the electrolysis of water, photo-electrochemical processes, the gasification of organic matter at high temperatures, and the anaerobic digestion of biomass. 

The Portuguese National Strategy for Hydrogen sets out to produce green hydrogen in Portugal in two ways:  

• Centralised for large-scale production. 
• Decentralised for small-scale production close to consumption sites, such as near domestic and industrial wastewater collection and treatment sites, in order to take advantage of this resource. 

Portugal needs to reduce greenhouse gas emissions by 85–90% by 2050, using land and forest to offset the remaining emissions. In other words, it is necessary to reduce emissions between 45% and 55% by 2030, and between 65% and 75% by 2040, compared with 2005.  

Decree-Law 62/2020 created the conditions for the incorporation of gas of renewable origin and low-carbon gases in the assets of the Portuguese National Gas System. This injection of new gases will significantly reduce CO₂ emissions and increase the consumption of energy from renewable sources, thus enabling the defined climate goals to be met.

In accordance with the Legal Separation articles of Decree-Law 62/2020 of 28 August, REN cannot hold any shareholding in a production or marketing company.

The advantages of introducing gases of renewable origin into the Portuguese National Gas Sector include: 

• As a complement to the electrification strategy, reducing decarbonisation costs.  
• Strengthening the security of supply, as hydrogen can store energy from renewable electricity for long periods of time.  
• Reducing the national energy dependence by using endogenous sources in production.  
• Producing clean fuels.  
• Promoting efficiency in energy generation and consumption.   
• Stimulating economic growth and job creation through the development of new industries and related services. 
• Greater sustainability of investments in the gas network, allowing revitalisation of the rural economy, with lower population density but greater predominance of primary sectors. 
• Compressed gas storage at high pressures (200–700 bar) is the preferred method in places where the hydrogen demand is variable and not too high, notably in fuel cell stack units, in buses, cars, homes, and commercial and industrial establishments. 
• The transition from hydrogen to the liquid state occurs at temperatures below -235ºC, so it can be stored in cryogenic tanks. 
• Metal hydrides, carbon nanotubes and nanofibres, glass microspheres, and polymers enable the storage of hydrogen at low pressures (< 10 bar).

Underground salt caverns are suitable for storing hydrogen and are already in use in England and in the United States. These infrastructures are also feasible for storing hydrogen mixtures of up to 10%, and tests and tests revealing no safety problems have already been carried out. However, for injection and mixing in storage infrastructures, an assessment of the facility’s integrity is required, which REN is currently carrying out at Carriço.

An hydrogen valley is the bringing together of different production, consumption, transmission, as well as storage and compression projects, with the goal of creating a local hydrogen market. A valley can be developed in a closed logic, in which the production is dimensioned to satisfy self-consumption, or in a free access logic enabling the connection of different producers and local consumers. This is the case of Agenda H2 Green Valley, led by REN Gás and a candidate for funding from the RRP for the establishment of the first hydrogen valley in Portugal, in the Industrial and Logistics Zone of Sines.