Technical Report

A perspective on the potential role of biogas in smart energy grids

December 2014

Summary

This report documents the potential role of biogas in smart energy grids. Biogas systems can facilitate increased proportions of variable renewable electricity on the electricity grid through use of two different technologies:

• Demand driven biogas systems which increase production of electricity from biogas facilities at times of high demand for electricity, or store biogas temporarily at times of low electricity demand.
• Power to gas systems when demand for electricity is less than supply of electricity to the electricity grid, allowing conversion of surplus electricity to gas.

The report is aimed at an audience of energy developers, energy policy makers and academics and was produced by IEA Bioenergy Task 37. Task 37 is a part of IEA Bioenergy, which is one of the 42 Implementing Agreements within IEA. IEA Bioenergy Task 37 addresses the challenges related to the economic and environmental sustainability of biogas production and utilisation.

This publication describes a perspective on the potential role of biogas in meeting fluctuating demand for electricity, and in smart energy grids. The amount of variable renewable electricity produced in the world is rapidly increasing and so is the need to develop suitable technologies to balance uneven electricity production and utilisation. Demand driven biogas plants allow electricity generation specifically at times of peak electricity demand. Power to gas systems allow any surplus electricity to be converted to hydrogen at times of low demand. Power to gas systems can generate gaseous biofuel for transport (or for heat) from electricity that is in excess of demand, for example in regions with very high generation capacity from intermittent sources such as wind and solar.

It is shown that biogas:

• can be used to facilitate increased variable renewable electricity on the grid
• systems can be used to increase electricity production at times of low supply

And that:

• Power to gas systems convert electricity to storable gas when demand for electricity is low
• Power to methane systems can act as a means of upgrading biogas to biomethane

Biogas production systems have significant potential to facilitate increased proportions of variable renewable electricity in an integrated energy system. This is implemented either by demand driven biogas systems or through power to gas systems. Biogas systems typically produce electricity at a relatively uniform rate, unlike variable renewable electricity such as produced by wind turbines. Demand driven biogas plants can increase electricity production at times of high electricity demand and can reduce electricity production at times of low demand. This can be achieved through storing biogas and only using it to generate electricity when needed by the grid. This managed fluctuation of electricity production can be enhanced through varying the time, and rate, of feeding of the biogas plant. Power to gas systems have a totally different role. In essence these systems involve converting electrical energy into gas that can be more readily stored. At times of low demand for electricity, electrolysis may be employed to convert surplus variable renewable electricity to hydrogen. Hydrogen is an energy vector of the future; the hydrogen infrastructure is not yet in place. Hydrogen may subsequently be converted to methane by catalytic or biological methanation. The methane may be used as a source of renewable gaseous transport fuel or renewable heat.

A model is proposed which combines these two concepts at biogas facilities allowing storage of variable renewable electricity, with co-production of electricity (at times of peak demand for electricity) and methane for gas grid injection (at times of low demand for electricity).

The authors of this report are members of IEA Bioenergy Task 37, which addresses the challenges related to the economic and environmental sustainability of biogas production and utilisation. IEA Bioenergy is one of 40 currently active Implementing Agreements within the International Energy Agency and has the aim of improving cooperation and information exchange between countries that have national programmes in bioenergy research, development and deployment. IEA Bioenergy’s vision is to achieve a substantial bioenergy contribution to future global energy demands by accelerating the production and use of environmentally sound, socially accepted and cost-competitive bioenergy on a sustainable basis, thus providing increased security of supply whilst reducing greenhouse gas emissions from energy use.