Today’s electric distribution systems (“grids”) of all sizes are faced with the need to integrate a large power contribution from renewable energy sources. The intermittent nature of most renewable sources complicates this task significantly; energy storage technologies can help resolve the problem.
“Power to gas” is a new technology which enables storage from intermittent renewable energy sources (RES), typically at utility scale. Electricity from solar, wind or other renewable generators is used to generate hydrogen, which is stored under pressure. Because the hydrogen is then available to (re-)generate electricity on demand, the intermittent renewably-generated electricity is now available whenever it is needed – it has become “dispatchable”. Power-to-gas has the advantages of low capacity cost, fast response, and very good scalability. It can be an important element for successful island or micro-grid operation.
Island grids are often located in regions with good conditions for wind and solar power generation. Utility-scale renewable energy systems at such sites can have lower costs than diesel generators, so it is attractive to provide a large fraction of grid power from wind and solar resources. However, the stochastic nature of these resources makes their integration particularly challenging:
- Large renewable energy penetration will often lead to temporary over-generation, which either needs to be curtailed or integrated using storage units
- Due to the occurrence of periods with zero renewable energy indeed (e.g., low wind + bad weather), the grid still requires enough conventional generation capacity to meet the power demand.
Power to gas can help manage this challenges:
- Energy storage can integrate excess generation from renewable energy units, i.e., avoid curtailment. The higher the renewable energy penetration, the more relevant this aspect becomes. With high renewable energy penetration, the required storage capacity must be large. Storage capacity must be inexpensive.
- A large storage capacity is also very effective in “peak shaving” and load levelling. The required capacity for conventional diesel generators can be reduced and the units can run more steadily and with a higher average load. Both of these aspects significantly reduce the cost of the conventional generation to balance the system.