University College Dublin
11:15 - 11:45
Wednesday, 18 September 2019
T3.4 Using the Natural Gas Network for Renewable Energy Storage
In reality no energy system stands alone and to fully understand a systems operation and limitations it is necessary to examine integrated systems to gain a fuller picture. This approach is especially important when investigating the natural gas network. While the natural gas network has supplied fuel to the electrical power plants for many years, the use of the natural gas network for the storage and transmission of otherwise curtailed renewable power through the use of power to gas systems is gaining increasing interest. This especially evident in countries such as Germany and Ireland, where the renewable power is generated a distance from the major demand centres. The every increasing number of renewable electricity installations is putting more demands on electricity network operators to transmit this power to users, with priority given to renewable electricity generators. Due to the variable nature of renewable electricity and the limitations of existing electrical network infrastructure the electrical network is often unable to bring the power to the end users and it is lost due to curtailment and constraint. In Ireland as installed wind capacity has increased year on year so too has the percentage of wind power curtailed. Through the use of electrolysis it is possible to capture some of this otherwise lost renewable power and using the natural gas network, transport it to potential customers where it can be usedfor heating or electricity generation when renewable power in unavailable. The hydrogen generated through electrolysis can be directly injected into the natural gas network at concentrations up to 20% with out the need to change existing burners, but the upper limit for safe operation of network is still under discussion. While it is possible to convert the Hydrogen to Methane before grid injection a further 10% energy loss is incurred.
To understand the impact of incorporating this renewable hydrogen into the gas network a transient model of a representation of Ireland’s natural gas network was developed in Matlab. This model also allowed for changing composition of the gas flowing in the pipelines, influencing the energy density and compressiblity of the gas. The model was validated against a commercially available software SAInt for natural gas.
A hydrogen profile was injected into a node on the network based on an Irish daily wind curtailment profile using a 1 MW PEM Electrolyser and the changing flowrates and pressures in each branch was calculated to satisfy predicted demand nodes energy requirements. Hydrogen concentration in the demand nodes adjoining the injection node varied through out the simulated time period with the changing wind curtailment profile and while the mass fraction never increased above 1%, the variation did impact flow through the pipelines which would have a knock-on effect on metering and billing. This small study highlights both the potential and the challenges that are associated with incorporating more renewable energy in the form of hydrogen into the existing gas network.