Some of the major areas that regulators should keep in mind in terms of integrating renewables are market rules and public outreach, particularly for transmission investments, Bird said during a Feb. 10 panel as part of the NARUC Winter Committee Meetings held in Washington, D.C., noting that European countries have had issues with public acceptance of transmission, more so than with accepting renewable targets.
In discussing the importance of considering system operations, Bird noted that Denmark, for instance, has had very high penetrations of wind energy on its system and has been able to handle it pretty well. Some of that is because it operates in a large power pool and has a lot of flexibility in that the country has, for instance, access to Norway’s hydro plants as well as combined heat and power, which can serve as a form of thermal storage and provides additional flexibility.
In contrast, Germany has struggled with renewable integration because it has a smaller area in which to balance the system and less flexibility, Bird said. Also, Germany does not have locational marginal pricing, “so, there’s no financial impact for the congestion on the system,” she said.
Spain, she noted, has a control center for renewable energy, which is a centralized system “where they have a single point of contact with the grid operator and they’re tracking all of the output from the renewable generation and they’re able to manage very large amounts of wind power on their system.”
With respect to grid support, she noted there has been interest in Germany’s case, in which the country experienced a rapid growth in photovoltaics (PVs) and had to modify “their grid codes to make sure that they weren’t going to lose all the small PV capacity all at once on the system if there was a small frequency change on the system,” she said.
Germany had to retroactively change the inverters on the system to accommodate the PV, she said.
“hat’s a lesson for other regions — to get out ahead of those understand what’s needed in terms of grid support from these renewable facilities,” she said.
A challenge that Europe has faced is public engagement revolving around electric transmission, she said, noting that there is a lot of concern about aesthetics and interest “in trying to do undergrounding to deal with that.”
A lesson to learn from Ireland is that the country has coordinated the transmission planning at the national level in efforts to reduce the amount of local approvals required and site transmission, she said.
Renewable energy resources pose such challenges to the electric grid as unavailability and uncertainty, Bird said.
“We’ve always had these challenges with load — load is varying all the time — but the introduction of renewables creates variability on the generation side as well and so that’s a new challenge for the grid,” she said.
PV systems, for instance, are subject to variability from cloud cover, but once one increases the number of PV plants and they are dispersed across the grid, that variability smooths out, she said, adding that the same thing occurs with wind power plants.
There are a variety of solutions available to integrating renewables on the grid and there is no one single solution that a grid can adopt as every grid is different with its own institutional characteristics, market operations, generation mix and the like, she said.
It is important to consider which options are least cost for a particular grid and that can vary over time, Bird said, adding that some changes that can be made to help integrate renewables include faster energy markets and balancing over a larger geographic areas
Also, advanced forecasting techniques help reduce uncertainty as “you get a better handle of how much wind you’re going to have available,” she noted.
Other options include better utilization of the existing transmission capacity as sometimes, there is underused transmission capacity available, as well as a more flexible generation fleet “so there’s significant variation across generation sources in terms of how much time it takes to start them up, to ramp them, what are their minimum generation levels, and so forth,” she said.
Furthermore, demand response has been shown to be a useful tool for integrating renewables as it can help reduce the amount of reserves that are needed on the system.
This article was originally published on GenerationHub and was republished with permission.
http://www.renewableenergyworld.com/rea/news/article/2014/02/adequate-transmission-among-options-to-better-integrate-renewable-energy-to-grid-says-nrel
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