raw · papers · ingested 2026-09-19
Techno-Economic Feasibility of Geothermal Energy from Inactive Oil and Gas Wells for District Heating and Cooling in Tuttle, Oklahoma (Oh et al., NREL 2024) + YORK absorption-vs-electric break-even
Source: https://www.osti.gov/pages/servlets/purl/2341266
Provenance: Peer-reviewed national-lab modelling study (GEOPHIRES, TOUGH2, EnergyPlus). Not EGS-deep, but the only fetched source that quantifies geothermal absorption cooling against an electric baseline on the same loads. Retrieved via research agent; full text extracted with pdftotext.
Resource and configuration
- Gradient 25.3 °C/km: 68.2 °C at 2.1 km; 98.5 °C reservoir / 87.1 °C average production at 3.3 km. Repurposed inactive oil and gas wells; best scenario 9.3 kg/s.
- Absorption chiller COP assumed 0.7 (Table 3) and 0.8 (LCOC). Authors note single-effect COP is “typically less than 1 … at low temperature below 150 °C”; scenarios producing ~60 °C were excluded from cooling entirely because the temperature is too low to drive a chiller.
Energy comparison (Table 3)
| Case | Annual input | Peak |
|---|---|---|
| Electric baseline cooling (EnergyPlus air-cooled, modelled COP 13.9) | 1.55 GWh electricity | 1.01 MW |
| Geothermal absorption cooling, same loads | 8.64 GWh heat | 5.08 MW |
About 5.6× more input energy for the heat-driven route. Authors: geothermal absorption cooling “may consume much more energy than the base case due to a low efficiency of the chiller operating at a low temperature.” Heating, by contrast, saved ~7 GWh/yr.
Cost
- Best scenario (existing wells, 3.3 km, 9.3 kg/s): LCOC $74/MWh vs LCOH $42/MWh “due to the lower cooling production (0.99 MWth) than heating production (1.47 MWth) and the additional CAPEX and OPEX for absorption chillers.”
- Scenarios drilling new wells reached LCOH ~$500/MWh (four wells, $16M CAPEX); reusing wells saved ~$7M drilling.
- Utilization: LCOH $198–243/MWh without a base load; $100–130/MWh with 0.3 MW base load; $68–94/MWh with 0.6 MW. Heat-driven systems are only economic with high, flat utilization.
- Thermal drawdown: quartet configurations showed “rapid thermal drawdown … after 2 years of operation” even at 2–3.5 km and low flow.
Companion: YORK / Johnson Controls, “Busting Four Myths About Absorption Cooling” (R. Dixit, c. 2020)
Source: https://www.york.com/-/media/project/jci-global/york-sites/united-states-york/insights/files/busting-four-myths-for-absorption-cooling-whitepaper.pdf (vendor whitepaper; transparent worked example)
- 500-ton process plant, “average US city.” COPs: electric centrifugal 6.5; direct gas-fired absorption 1.2; double-effect steam 1.4; single-effect steam 0.7. Prices: electricity $0.15/kWh, gas $5/MMBtu, steam $4/1,000 lb.
- Chiller input-energy cost (¢/ton-h): electric 8.12 ($253,714/yr); gas-fired 5.00; double-effect 3.43; single-effect 6.86 ($235,513/yr). Whole plant incl. pumps and tower: electric $330,330; single-effect $316,044.
- Derived by the research agent from those figures: the electric chiller draws 0.541 kWh/ton-h, so single-effect absorption beats it on energy cost only when electricity exceeds ~$0.127/kWh at $4/1,000 lb steam. At the vendor’s own $0.15/kWh it saves just
$14k/yr on 500 tons; at US industrial rates ($0.08/kWh) it loses. - Auxiliaries cost more for absorption ($80.5k vs $76.6k/yr) because absorption rejects ~2.4 kW per kW of cooling vs ~1.15 kW for electric — roughly double the cooling-tower duty and water.
- Vendor concessions: “in many cases, an electric chiller makes more sense”; absorption needs entering condenser water ≥ 68 °F/20 °C (electric handles 55 °F); slower response due to LiBr inertia; “Electric centrifugal chillers … making them a sound choice for mission-critical applications such as data centers.” Crystallization: 0.5–1% LiBr concentration change materially shifts crystallization temperature; cold condenser water is a main trigger. COP 1.42 → 1.36 as condenser flow drops 4 → 2 gpm/ton.
- Quote: “Higher COP does not necessarily result in low operational cost.”
Relevance to the cooling wiki
The quantitative core of the “use the electricity, not the heat” argument: at <90 °C brine, heat-driven cooling costs ~1.8× heat and consumes ~5.6× the input energy of electric cooling; and even at good drive temperatures, single-effect absorption only wins where electricity is expensive, the heat is otherwise free, and rejection water is cheap. Pairs with the Chena and OIT case histories.