Balancing with Biogas?

News that the peak market prices are getting out of hand in Poland raises the issue of using more means to balance energy production. The 24 hour cycle seems to be getting worse. Energy storage over a short span of hours seems to be an attractive idea.

While there are a number of energy storage solutions using batteries to store electricity, or devices to store kinetic energy to produce electricity later, one of the renewable energy sources itself has the potential to provide output matched to the 24-hour demand cycle - biogas,

All biogas plants have biogas storage in some form. The most common is shown below:

One biogas vendor explained one of the advantages of gas storage:

 "Since the gas-store can hold several hours of gas, the CHP unit can be turned down during off-peak generating times without loss of biogas. The stored biogas can then be burned during high-peak electricity demand hours to maximize revenue efficiency. In addition, the gas store provides a steady supply to the generator during peaks and troughs in methane production, thereby increasing efficiency, reducing wear on the generator, and eliminating waste."

While the European Commission background document on energy storage pushes the idea of storage of hydrogen in the future to be used to balance energy production with demand, the same European Commission ignores the potential for doing this with biogas/methane right now. The costs are much lower since the only requirements are more methane storage capacity and more generation capacity. See below. The new state aid guidelines, however, seem to require that all renewable electricity be sold to the grid , where it gets swept up in one flat rate regardless of the time of production. This seems incredibly short-sighted to me, when the whole Commission document is complaining about demand and supply mismatches.

It is quite possible to store methane over-night and run more generation of electricity during the peak day hours. "The stored methane would subsequently be converted by a generator owner in order to dispatch MW power to the grid to supply high demand prices ($/MWh) on the spot market."  Stefan J. Minott,  Onpeak Market Dispatchable Energy From Megawatt Scale Fuel Cells And Stored Digester Methane, PhD thesis (Cornell Univeristy 2014).  This can be done without purification of the methane or any additional expensive processing. As Minott observed, this is easier to do when the facility can sell directly to the end-user.[1] This is the case now in Poland under the Green Certificate program and as long as that system is used, differential electricity pricing is possible.

A variable peak  feed-in tariff is also possible, as it done in Ontario.[2] This would require some additional paperwork at the Polish Energy Regulatory Agency, but would allow the technologies capable of "bending" production to do so. Given the huge problems from intermittent renewable energy production and even conventional peak cycles, this seems to be a solution worth serious consideration. Properly priced, such a solution could also foster additional energy storage technical solutions for intermittent producers like PV and wind.

The added costs for a biogas plant would be additional biogas storage capacity and additional generator capacity (which would not be used during off-peak hours). It is already feasible to produce additional peak hour output with direct sales of the electricity produced. It could be feasible to do so with grid sales if the differential were adequate. The direct sales market mechanism seems preferable since it can adjust itself to changes in the market. This should be the preference for both the European Commission and the Polish Ministry of Economy, who both espouse the need for market-based mechanisms (while not always finding them or recognizing them when they are presented). Using the existing differential in market price between peak and off-peak electricity does not really cost anyone anything more. It simply matches the solutions to the problem.

I am eager to discuss differential temporal electricity production  with potential direct users,  energy sellers and traders, as well as government officials. Poland has the time now to incorporate some sensible solutions into the new law. Under the current Green Certificate system, we still have some time to add the necessary facilities to ongoing biogas projects to  provide differential output for direct users.


[1] More elaborate processing to purify to natural gas quality could be used to develop a commodity that could be sold on the natural gas spot market (as Minott describes and models). But this seems to be a lot of added expensive with little to gain, if the electricity itself can be sold at a premium in the peak hours.

[2] From the Ontario Power Authority website:  "Is there an incentive for peak production? Yes.
  • Technologies that are not intermittent (i.e., dispatchable), such as bioenergy and waterpower, will be encouraged to shift production to peak periods when the electricity is most needed.
  • Payments will be 35% higher from 11 a.m. to 7 p.m. on business days, and 10% lower during off-peak hours.
    • Projects will earn the posted FIT price multiplied by:
      • 0.9 for off-peak periods
      • 1.35 for peak periods
  • Projects that operate 24 x 7 every day of the year will earn the same total revenue as if they had been paid the posted FIT price.


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