INTERVIEW - Solar, wind perform well during Texas heatwave, Enel executive says

As renewable power generation is helping the Texas power grid meet demand amidst extremely high summer temperatures, Mona Tierney-Lloyd, head of US state policy at Enel North America, says that solar and wind resources have performed very well during the heatwave and suggests that batteries and demand response could be used more broadly for reliability in the state.

“In spite of the heated political rhetoric around wind and solar’s reliability benefits, the technologies have performed well this summer to date,” Tierney-Lloyd tells Renewables Now, noting that ERCOT’s CEO has referenced the performance of solar resources as being a key component to maintaining the reliability of the grid. The Electric Reliability Council of Texas (ERCOT) is the grid operator for most of Texas.

Emphasising the synergy between solar and wind, she explains: “Solar and wind tend to have complementary production profiles: when wind is waning in the late morning, solar production is ramping up and vice versa. When wind is waning and solar is ramping, that is an excellent time for battery storage deployment to even out the potential lag in electricity generation, since demand is also ramping up at that point.”

Recently, the US Energy Information Administration (EIA) spotlighted Texas' successful management of unprecedented electricity demand during the late June and July heatwave, with a noteworthy shift in resources used to fulfil demand. While natural gas remained the main power source, non-fossil fuel sources -- wind, solar and nuclear -- contributed more than 50% of total generation on the high-demand days of June 28 and June 29. They never surpassed 50% of total generation in ERCOT in previous high-demand periods, such as in August 2019 and August 2022, EIA said. In addition, this shift helped wholesale electricity prices increase less than would be expected for such high demand levels.

Commenting on the changing grid and the market for grid support technologies, Tierney-Lloyd said: “The electricity grid is changing quickly in numerous ways: by adding higher levels of penetration of wind and solar, by changing demand profiles, due to electrification of buildings and transportation, by the need for more transmission infrastructure across the country, or by the backlog of interconnection queues managed by transmission operators (individual and organised)."

In light of potential delays in resource integration arising from transmission and interconnection complexities, she underscores the need for swift deployment of modular technologies to amplify supply or mitigate demand.

"Batteries are certainly one of those solutions that can be deployed at a customer site or on a larger scale to absorb generation from wind and/or solar during the day, and redispatch that energy at a later time when to meet demand or to provide grid support through ancillary services."

Managing customer consumption is also important, she adds, noting that demand response is currently limited either through ERCOT or through the transmission and distribution utilities (TDUs).

"Considering the significant growth in demand year-over-year in ERCOT and the timing delays that could occur on bringing new supplies online or building new transmission, batteries and demand response are two tools that could be used more broadly for reliability in ERCOT.”

Enel North America is a significant player in Texas’ energy sector. The company currently has over 3.3 GW of wind and solar capacity and 690 MW/1,036 MWh of utility-scale battery energy storage systems (BESS) installed across the state. The latest addition to its fleet is the Blue Jay solar + storage project in Grimes County, which combines 270 MW DC of solar capacity with a 59-MW DC battery storage system. The BESS component of the project became operational earlier this summer and is now fully participating in the market, having maintained high availability during the scorching hot weather. The solar component is fully operational and awaiting final ERCOT approval for full participation in the market.

Additionally, Enel manages around 200 MW of demand response capacity on behalf of commercial and industrial customers in the ERCOT market, says Tierney-Lloyd.

The company is continuing to grow its portfolio in Texas with over 1.8 GW of solar capacity and 652 MW/978 MWh of BESS activity under construction across the state. It is also continuing to grow its demand response and electric vehicle (EV) charging portfolios in the state, as well as its retail electricity business, which was launched in late 2022, the executive adds.

Asked about how Enel responds to challenges such as curtailments and negative prices, its US state policy head says that the company generally manages these risks through the geographic and technological diversification of its renewables and storage fleet in ERCOT.

“One cause of renewable curtailment is congestion on the transmission system—a lack of adequate capacity to transport electricity from the point of generation to the load centers. Expanding transmission service in areas that are experiencing congestion is a way of relieving renewable curtailment in those areas. The Texas Legislature, in 2021, passed legislation that allowed ERCOT to explore building transmission to relieve congestion, which consumers pay for. If the cost of congestion measured over a period of time was less than the cost of a transmission upgrade, then it makes economic sense to upgrade the transmission. We’re eager to see ERCOT make more progress on exploring the appropriate economic metrics for upgrading transmission corridors,” she further commented.

In another recent article, EIA said that in 2022, ERCOT curtailed 5% of its total available wind generation and 9% of the total available utility-scale solar generation. Assuming no significant grid upgrades, EIA projects wind curtailments could increase to 13% and solar curtailments to 19% by 2035.

Curtailments, however, could be reduced through an increase in demand, such as through battery charging.

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