Foxtail Flats solar will produce daytime surpluses and night shortfalls; staff lays out three options — market sales, storage, or dispatchable capacity

Los Alamos County staff told the Board of Public Utilities on Feb. 5 that when Foxtail Flats solar comes online in the 2026 timeframe the county’s pool will likely produce more daytime energy than the pool needs and be short of energy at night, and staff outlined three broad strategies for responding: market sales/purchases, added long‑duration storage, or locally sited dispatchable capacity.

The problem and the numbers Staff modeling presented at the work session projected that, on an annual basis and at full Foxtail Flats output, the power pool would have roughly 60,000 MWh/year of excess daytime energy available for sale and would be short about 83,000 MWh/year at night. The figures are aggregate annual estimates and vary seasonally: excesses are largest in high‑sun summer months and deficits peak in winter night hours.

Three broad response options 1) Market sales and purchases (low capital build but high market exposure): Sell daytime surplus into short‑term markets and buy night energy as needed. Preliminary order‑of‑magnitude modeling in the packet put the net annual cost of this buy/sell approach in the $44–$55 million range for the pool in current market assumptions. Staff cautioned this path carries high exposure to market price volatility and negative pricing events.

2) Add long‑duration storage (reduce market exposure, supports carbon goals): Staff said large‑scale multi‑hour or multi‑day storage (as an illustration, they discussed a conceptual ~200 MWh long‑duration facility) would reduce daytime sales and nighttime purchases and tighten the pool balance. A conceptual cost estimate in the packet tightened the modeled annual net cost range to roughly $47–$50 million. Staff emphasized long‑duration technologies are emerging and availability and unit economics are uncertain.

3) Add dispatchable peaking generation (reduce market buys, increase resilience but raises emissions): Staff sketched a scenario using combustion‑turbine or reciprocating internal combustion units sized for peaking/nighttime needs. That approach lowered market exposure and increased local operational resilience but produced the highest modeled cost range (roughly $54–$65 million annually in the packet’s conceptual figures) and would rely on thermal generation for some nighttime energy.

Other factors and next steps - Curtailment costs: Staff noted that curtailing Foxtail Flats output is costly under contract because of foregone production tax‑credit value; advisers cited illustrative curtailment penalty pricing in the presentation. - Potential buyers and partners: Staff reported outreach to potential offtakers, including Kirtland Air Force Base and Sandia National Laboratories, which are themselves procuring resources in the coming years; staff suggested 3–5 year sale agreements could be a near‑term approach while longer‑term storage markets and technologies mature. - Long‑duration technologies: Staff flagged emerging technologies (for example, new mechanical or chemical storage approaches) that might be lower‑cost than lithium‑ion four‑hour batteries for the specific long‑duration services needed, and said county staff is actively investigating vendors and potential sites. A vendor conversation and a developer meeting were scheduled as follow‑ups.

Resilience and carbon goals Staff framed the options against county goals: storage best supports an annual carbon‑neutral target by enabling renewable energy to serve night hours; dispatchable thermal units increase local resilience and reliability but would affect the county’s emissions profile unless paired with offsetting carbon‑free resources.

Public comment and community concerns Public commenters raised questions about how Foxtail Flats is considered in federal NEPA analysis related to LANL transmission upgrades. Marissa Naranjo of Honor Our Pueblo Existence asked the board to urge DOE/NNSA to include Foxtail Flats in analyses of proposed transmission infrastructure related to LANL’s Electrical Power Capacity Upgrade (EPCU) project to avoid unnecessary transmission expansion and to consider local renewable development as part of the alternatives analysis.

Speakers - Ben (Operations/energy planning lead, Los Alamos County utilities) (government) - Nick (presenter/modeling lead) (government) - Philo (utilities administration/finance) (government) - Chairman Gibson (Chair, Los Alamos Board of Public Utilities) (government) - Public commenter Marissa Naranjo (Honor Our Pueblo Existence) (nonprofit)

Authorities - {"type":"other","name":"Draft Energy Coordination Agreement (ECA) and related DOE/NNSA NEPA processes","citation":"discussed in meeting; draft under review by DOE/NNSA","referenced_by":["foxtail-flats-resource-planning"]}

Clarifying details - {"category":"project_capacity","detail":"Foxtail Flats capacity discussed as approximately 70 MW (nameplate); expected production and seasonal shape will create daytime surpluses and nighttime shortfalls","source_speaker":"Ben"} - {"category":"annual_energy_balance","detail":"Modeling showed approx. +60,000 MWh/year daytime surplus and –83,000 MWh/year nighttime deficit for the pool with Foxtail at full output","source_speaker":"Nick"} - {"category":"preliminary_cost_ranges","detail":"Conceptual net annual cost ranges (pool level) for three options: market buy/sell $44–$55M; storage $47–$50M; dispatchable peakers $54–$65M; modeling is high‑level and seasonal/hourly fidelity needed for final procurement decisions","source_speaker":"Ben"}

Discussion_decision":{"discussion_points":["Whether to rely on market sales/purchases, pursue long‑duration storage, or acquire dispatchable peaking capacity","How to structure short‑term sales agreements and the desired term length (e.g., 3–5 years)","Coordination with LANL, Kirtland and Sandia on offtake opportunities and NEPA/tansmission analyses"],"directions":["Staff to meet with the Foxtail Flats developer and potential offtakers and to continue evaluating long‑duration storage vendors and site options"],"decisions":[]},"searchable_tags":["Foxtail Flats","solar","storage","resource_planning","NEPA","DOE"],"provenance":{},