While there has been extensive discussion and analysis of the requirements for integration of renewableelectricity generators with the electric grid, there has been much less focus on the interactions with thenatural gas grid, which, nevertheless, could be significant. There is widespread agreement that gas-based generation will be an important component of renewable integration but there has been little detailed analysis to date of the potential interactions between the electric and natural gas systems.
ICF International, a leading provider of consulting services and technology solutions to government and commercial clients, has released a white paper titled Integrating Variable Renewable Electric Power Generators and the Natural Gas Infrastructure. Below are excerpts.
Click here for the full paper
Integrating variable electricity generation requires changes in the electric system. Some of these can be potentially large changes in planned generating capacity. The system must also be able to respond when electricity supply is different than expected. Thus, the system must respond quickly to short-term fluctuations in the renewable energy supply. This is addressed in part by a change in “ten minute reserve” requirements—typically quick-start gas peakers. Some of the services are required in the absence of renewable generation, but the addition of renewable generation adds more and different requirements that may be met by existing or new generating facilities.
The amount and type of new generating facilities that are required can vary widely depending on the existing generating mix, role of renewables in the local market, electric demand growth, regional transmission capacity and other factors. The requirement can range from zero to 80 to 90 percent of the renewable resource depending on these variables thus, selecting a value for analysis can be challenging.These changes in the make-up and operation of the electric system require changes in the gas supply infrastructure and its operation. These include enhanced line pack, applications of new no-notice and gas storage services, increasing the number of nomination cycles, and reducing the length of nomination cycles. They also include changes in local gas delivery infrastructure to accommodate these needs.
There is already significant variability in daily gas use due to weather and other factors:
(1) residential and commercial gas loads fluctuate significantly with changes in weather,
(2) electric load also fluctuates with weather and by time of day, which in turn drives fluctuations in gas demand for power generation, and (3) variability in loads from these sources will change as the amount of load changes over time. Projected impacts of renewable generation variability make up a relatively small portion of total gas load variability, but the variability associated with responding to variable renewable generation will grow as renewable capacity increases. Although it will still remain a small part of total gas load variability, it can have a significant effect on local infrastructure and operational requirements.
Overall, the issue is not total gas volume changes, but rather changes in operations and infrastructure and requirements. Plans must be made to account for the potential variability associated with gas generation used to support variable renewable generation. Changes in power infrastructure construction and operating costs will need to be recovered by generators. Similarly, changes in gas infrastructure construction and operating costs will need to be recovered by the natural gas pipelines.